hitech

Laser: Lightwave of the Future

Bern University of Applied SciencesEngineering and Information Technology

2/2012 The Magazine

hi tech

The laser beam – a universal tool

Gwatt on Lake Thun – a Mecca for laser professionals

Well-prepared to start international business with Fit2GlobalizeTM

It is well-known that mankind differs from the animal

world in three distinct characteristics: abstract thinking

by means of concepts, language, and the use of tools

made by man himself. A lot of the world in which we live

today has been created by tools such as the computer

to process ideas, or by machines to process materials.

What is less well-known is the fact that our region (more

precisely, the Alemannic area that once stretched from

Augsburg to Geneva, and from Chiavienna to Strassbourg),

has been and still is the global leader in the inventing and

manufacturing of new precision mechanical tools as well as

in their use in machines.

When laser technology was invented in California 50 years

ago, Switzerland was soon looking into ways of using this

intense beam of light as a contact-free tool. A contact-free

tool never wears out and thus carries immense advantag-

es such as high precision at all times and no downtimes for

replacement. Soon some institutes and companies around

Bern came together and researched the use of laser tech-

nology for the purpose of processing materials. They de-

veloped processes and beam tools, and then sold them

worldwide. Today Switzerland is one of the leading nations

in the manufacturing of laser beam tools in competition

with Germany, Japan and the USA.

Since the 90’s, Bern University of Applied Sciences in

Burgdorf, first at the IALT, now at the ALPS, has been

researching and developing new laser beam tools and

ways of processing materials in close co-operation with

industry. The first development phase looked into ways

of using laser to minimie tool wear. In a later phase, re-

searchers sought ways to cut the materials more exactly

and then weld them in such ways that lighter and yet

safer cars could be produced, and motors that need less

fuel could be built.

E D I T O R I A L

Dr. Christoph HarderPresident Swisslaser.NetPhoto : Swisslaser.Net

The laser beam – a universal tool

ImpreSSUm

Editors Patrick Studer, Diego Jannuzzo Translation Carmel Widmer-O'Riordan, Patrick StuderAdress BFH-TI, hitech-Redaktion, Postfach, 2501 Biel,E-Mail Editor [email protected] Homepage hitech.bfh.ch Circulation 1500 issuesGraphics and layout Ingrid ZengaffinenPrint Stämpfli Publikationen AG, Wölflistrasse 1, Postfach CH-3001 Bern – hitech 2/2012, Special Edition English: September 2012

This magazine is available in German and French

under: www.hitech.bfh.ch

Focus 3Lightwave of the Future

The laser beam – a universal tool|

4 Gwatt on Lake Thun – a Mecca for laser professionals

7 Gwatt – where laser professionals develop new ideas

8 The Janus-faced aspects of applied research

10 Ultrashort and small

12 25 years of collaboration: a Russian-Swiss success story

14 Cutting metal with laser is like cutting through butter

16 Harvesting the sun more efficiently

18 Joining Forces: Doctoral Research at BUAS and University of Bern

20 Swept-Source laser sources at the BUAS OptoLab

23 Z-LASIK – eye surgery without blades

24 Fiber lasers: Processing material with glass fibers

26 ROFIN-LASAG: Pioneers in laser welding of copper

28 SILITEC – more efficiency and fewer costs thanks to sand

30 Well-prepared to start international business with Fit2GlobalizeTM

Cover:Impressions from the laser labPhoto: BUAS-EIT

2/2012 hitech 32 hitech 2 /2012

Laser beam sources developed further: in raw power

and strength, through beam guidance in fibers, in their

precision, and in their modulation. As a result, new appli-

cations continue to be created for use in, for example,

medical operations, the manufacture of bio-compatible

surfaces on implanted pieces of metal, and in the pro-

cessing of synthetics.

50 years after the invention of laser technology, the pro-

gress of beam tools continues unabated. Bern University

of Applied Sciences is in a good position to continue the

very old Alemannic tradition of developing mechanical

tools, and to contribute to our quality of life with newly

developed laser beam tools.

Dr. Christoph Harder

President Swisslaser.Net

Gwatt on Lake Thun – a Mecca for laser pro-fessionals

Physicists from the University of Bern built the first Swiss solid-state laser as far back as

1963. They continued to develop it further and mounted a stronger version on an astronomi-

cal telescope, allowing observation of satellites through laser beams at Zimmerwald Obser-

vatory. This was a huge success. Nobody could have anticipated that the Canton of Bern

would become a leader in the field of laser technology, which it did thanks to the know-how

of the University of Bern and, later, Bern’s University of Applied Sciences.

4 hitech 2 /2012

F O C U S | L I G H T W A v E O F T H E F U T U R E

Sciences to instruct students on the options of using the

laser as a tool, its application in the welding and cutting of

laser beams, as well as on aspects of laser safety or the

simulation of laser-led processes.

Lasers win over the world of industryThe number of laser welding applications has risen cons-

tantly over the last 20 years. Thanks to the controllability

of laser energy and the reaction time of the material, it

may soon be possible to weld metallic materials at high

melting temperatures or high thermal conductivity. Laser

welding is interesting in so far as it enables the combina-

tion of similar or different elements without having to ap-

ply supplementary material. In contrast to other, more

conventional methods of welding technology, the laser

directs heat precisely onto the object itself. Interaction

with the material lasts a matter of milliseconds. The range

of materials that can be used in laser welding is quite

wide; from high-alloyed steels, tungsten, molybdenum,

and tantalum to nickel and beryllium as well as aluminium

and titan and, thanks to a discovery made by Swiss re-

searchers from the Gwatt-Thun region, also to non-fer-

rous heavy metal such as copper.

1993, focuses on the latest developments and findings in

laser technology applications. It offers internationally rec-

ognised experts a platform to present their results and the

opportunity to exchange ideas.

Whether they are optimising combustion engines, making

a profit for the scanner industry, breathing life into our

CD’s and DvD’s, luring us into a speed trap or working

their magic in the 2 million cases of glaucoma every year,

lasers are here to stay and have become a fixed part of

our everyday lives. It’s just as well that Theodore Harold

went against his father’s wishes and became a physicist

instead of a doctor!

Contact:

> [email protected]

> Further information: www.alps.ti.bfh.ch

www.alt12.org

Abraham Maiman was not well pleased when his son,

Theodore Harold, decided to become a physicist instead

of a doctor. In a laboratory owned by the millionaire, How-

ard Hughes, Theodore worked tirelessly in the interests of

pure research to develop a piece of equipment that would

eventually be able to concentrate light. Einstein had al-

ready promoted the principle of stimulated emissions

back in 1917. By 1960 had come up with the solution and

presented the world’s first ever functioning ruby laser.

Other researchers were a little sceptical at first. Even

Maiman’s assistant, Irnee D’Haenens, joked that the laser

was «a solution looking for a problem».

Since then the laser has conquered the world. Optical and

laser technologies have become leading disciplines in-

volved in innovation around the globe. Universities teach

fundamental elements of physics such as the production

of laser beams, laser guidance and the design of laser

optics. It is also the remit of the Universities of Applied

2/2012 hitech 5

Researchers at the University of Bern have been develo-

ping lasers for use in both pure and applied research for

over 50 years. The first Swiss laser was set up in the la-

boratory of the IAP (Institute of Applied Physics, Universi-

ty of Bern). Today they are working on new types of high-

ly stabilised or pulsed models such as fiber or x-ray lasers.

As a result, the Canton of Bern has become a strong and

highly competent player in the laser and optics industry

with an annual turnover of 500m Swiss Francs.

ALPS-the problem solversThe Institute for Applied Laser, Photonics and Surface

Technologies (ALPS) at Bern University of Applied Sci-

ences, Engineering and Information Technology (BUAS-

EIT) is the ideal partner for organisations. It has a team of

highly specialised experts working with industrial partners

to develop new processes and techniques in the manu-

facturing of elements and their analysis in ways that save

both material and energy. The symbol for this technology

transfer is IAP’s and BUAS's joint Centre of Competence

«Fiber and Fiber Lasers». While the IAP concentrates on

developing fundamental elements, the ALPS deals with

applications, which then lead to cooperation with busi-

ness firms.

On the basis of their competence in this field, the Bern

University of Applied Sciences decided to invite scientists

and researchers from all over the world to the 20th Inter-

national Congress on Advanced Laser Technology at the

beginning of September 2012. This ALT event, first held in

Prof. Dr. Franz BaumbergerHead of Research and Development at BUAS-EITPhoto: Arteplus Sàrl

ALPS – who we areThe Applied Laser, Photonics and Surface Technologies group (ALPS) at BUAS-EIT has a long tradition in the field of materials processing and is the leading group in materials micro-processing in Switzerland. Our main experience lies in processing absorbing as well as dielectric materials with short (nanosecond) and ultrashort (picosecond and below) pulses of different wavelengths. Typical applications comprise the surface micro-structuring of metals, ultra-hard materials like diamond, hard metals, diamond-like carbon and ultra-hard coatings for tribological applications and the selective ablation of thin films on various substrates. ALPS operates a «Fiber and Fiber Lasers Center of Competence» together with the Institute of Applied Physics at the University of Bern. This center of competence started its activity in 2009 and runs fiber-technological equipment for fiber prototype drawing, fiber characterisation, fiber cleaving, fiber tapering. Contact: Prof. Dr. Patrick Schwaller, Head of ALPS, [email protected]

Material processing with laserPhoto: photolook-Fotolia.com

Laser scanning- problem solver in actionPhoto: BUAS-EIT

STI - We support innovation

The Foundation for Technological Innovation offers financial

support to founders of start-up companies in the form of a

long-term and interest-free loan. The Foundation promotes

technological innovation with economic potential.

STI - Wir unterstützen Innovationen

Die Stiftung für technologische Innovation gewährt Gründern von

Start-up-Firmen eine fi nanzielle Unterstützung in Form langfristiger

zinsloser Darlehen. Gefördert werden technologische Innovationen

mit wirtschaftlichem Potential.

www.sti-stiftung.ch

From the innovative idea to the marketable product

Von der innovativen Idee zum marktfähigen ProduktThe renowned Russian General Physics Institute in Mos-

cow launched the first ALT Conference in 1993, and since

then these have been held annually around the globe, re-

ceiving great acclaim along the way. This year it is Swit-

zerland’s turn to be the host country and welcome foreign

researchers to the shores of Lake Thun.

Glimpse behind the scenesThis year’s organisers are researchers from the Institute

for Applied Laser, Photonics and Surface Technologies

(ALPS) of the Bern University of Applied Sciences in co-

operation with their Russian counterparts. Thanks to their

international connections, they were able to attract re-

nowned researchers from the USA, France, Germany, Ja-

pan, Russia and Switzerland for the plenary lectures. In

addition, other speakers will be giving talks that will offer

an excellent overview of the state of research in laser

technologies and their applications. The scientific confer-

ences will be divided into various thematically-linked ses-

sions. The more fundamental themes such as biophoton-

ics, non-linear optics, photo-acoustics or terahertz laser

sources and their applications will be dealt with, and there

will also be sessions aimed specifically at people from the

world of industry. Here the focus will be on laser systems

and fiber lasers, laser diagnostics and spectroscopy, mi-

cro-and nanophotonic appliances and components as

well as special laser-material interactions and process

technologies.

The poster session will take place on the large sundeck of

the MS Stadt Thun, one of the largest motor boats on

Lake Thun. This will give participants the opportunity to

discuss scientific findings and exchange views in elegant

surroundings.

Contact:

> [email protected]

> Further information: www.alt12.org

www.alps.ti.bfh.ch

Prof. Dr. Patrick SchwallerHead of ALPS at BUAS-EITPhoto: BUAS-EIT

From September 2 – 6, 2012, the International Conference on Advanced Laser

Technologies ALT12 will be held in the Gwatt Center at Lake Thun. Scientists from all

over the world will be presenting their latest research findings and demonstrating the

opportunities that laser technology has to offer to industry.

Gwatt: where laser professionals develop new ideas


High-temperature ellipsometer at the ALPS Institute of the BUAS-EIT

Photo: BUAS-EIT

2 /2012 hitech 98 hitech 2 /2012

Dr. Valerio RomanoProfessor of Applied PhotonicsHead of the Applied Fiber Technology GroupPhoto: BUAS-EIT

The Janus-faced aspects of applied research

Building on sand is not always the worst ideaOne of the projects being run by the two institutes is «built

on sand», though this is not meant to be understood quite

in the same way as in the well-known expression. The sto-

ry begins with a small, creative company from Boudry,

called Silitec. In an effort to cut down on costs, this com-

pany began searching for ways of producing optical glass

fibers more cheaply without affecting the quality of the

product. They managed to develop and then patent a pro-

cess whereby the manufacture of non-critical parts of the

fiber preform is based on quartz sand. This reduces the

costs and stimulates the imagination of researchers!

This method makes it very easy to produce microstruc-

tured fibers. The structures replace the simple refractive

index difference of traditional glass fibers, and allow light

to be transmitted in the fiber core. Such fibers are based

on a brilliant idea that researchers from MIT had in the late

80’s; namely the photonic crystal effect. More specifically,

these fibers can actually implement a characteristic which

is highly relevant for materials processing. Given the ap-

propriate structure, the core can be enlarged without los-

ing beam quality. This is of interest in so far as it allows

light to be transported with far fewer non-linear effects. It

would, of course, be ideal to be able to enlarge the core

diameter to a few hundredths or even tenths instead of a

few thousandths millimetres. If you do this with a tradi-

tional fiber, you end up with a choice between two evils:

either the beam quality suffers, or the radiation can no

longer be guided in the core at bending points and es-

capes from the fiber. This is where microstructured fibers

can be of help. There are special hole patterns around the

core that facilitate its enlargement without any loss of

beam quality during delivery transportation (photonic

crystal and leakage channel fibers).

Universities are responsible for the basic understanding of

knowledge, a task that reflects their expertise in funda-

mental research. Universities of Applied Sciences, on the

other hand, are responsible for applying this basic knowl-

edge. The tasks complement each other. Like the Janus

face, each one looks in a different direction; the Universi-

ties looking back at fundamentals, the Universities of Ap-

plied Sciences looking forward towards the social and in-

dustrial relevance of an application.

This can be exemplified by the research on optical glass

fiber that was once used mainly for optical communica-

tion, while today it is a key element of many modern lasers

both for generating laser light and delivering it to the work-

piece.

Co-operation works better when tasks are divided correctlyCo-operation between the Institute ALPS at the BUAS-EIT

and the IAP at the University of Bern has become much

closer. One of the fruits of this co-operation is the joint

Centre of Competence for Fiber and Fiber Laser. This is

made up of two laboratories; one at the IAP in Bern and

the other at the BUAS-EIT in Burgdorf.

Tasks are divided according to competence. While the

IAP carries out fundamental research on fibers and comes

up with designs for new fiber laser systems, the BUAS-EIT

examines how these can be integrated into machines. The

co-operation goes much further than in other similar pro-

jects. Though the research tasks are separated and

adapted to the strengths of the two institutions, the pro-

ject leadership is undertaken in close collaboration with

representatives from both laboratories, or by a person

who operates in both institutions.

Both teams also run a fiber drawing tower at the IAP, which

is where they work on producing prototypes of original,

microstructured glass fibers in co-operation with industry.

At present many of the of the laser systems under exami-

nation are being produced with commercially available

glass fibers, but their own glass fibers should be ready for

use in the foreseeable future. Other joint activities in the

area of education are also in the pipeline.

Passive today …Passive fibers of this kind have been developed by the IAP

in co-operation with the company Silitec, and then tested

and successfully applied by the BUAS. They lay the foun-

dation for the possible integration of laser technology into

machinery, allowing more freedom and flexibility of design

through flexible beam guidance as well as greater eye-

safety for the user.

… Active tomorrowAnd what about active fibers? Active fibers are fibers in

which the core is doped with a material that allows laser

light to be generated or amplified within the fiber core.

These should also be able to profit from the sand method.

The necessary doping material can be added to the quartz

sand in powder form. This would result in a fiber with a

structure that, at present, cannot be achieved by tradi-

tional methods, and all within a matter of hours rather than

weeks. The IAP has proved that this simple principle actu-

ally works. The losses are higher than anticipated but we

are on the right track.

Contact:

> [email protected]


www.iap.unibe.ch

Infrared image of the active fiber in a

ytterbium fiber laser. Although the

fiber emits a 10 Watt output, it

doesn’t need to be cooled. To

demonstrate this more clearly, it has

been loosely wound around a

plastic roll Photo: IAP Bern


There has been a long tradition of bottom-up co-operation between BUAS-EIT and

the Institute of Applied Physics of the University of Bern in the area of lasers and laser

materials interaction, despite a slight undertone of opposition from the «purist» corner.

Researchers working on applied projects quickly realised that a successful solution to

an applied research task has two complementary sides; namely, an understanding of

the basic processes as well as the ability to apply them.

Infrared image of a ytterbium fiber laser Photo: IAP Bern

Preform of a microstructured optical glass fibersPhoto : Silitec SA


the material, and practically all materials can be treated with

these pulses in a way both precise and that minimises the-

heat-affected zone. This does away with the often tiresome

post-processing of parts that have been treated with a laser,

and leads to an essential increase in precision.

Relevant to industryWhile ultrashort pulses were only relevant in an academic

context 10 years ago, today the situation has changed radi-

cally. The arrival of industrial-strength laser systems has

boosted industry’s interest in applications. This has opened

new perspectives, especially for Swiss companies with a

tradition in micro- and precision engineering. Possible areas

for application could be, for example, in mould-making, em-

bossing templates, tribological surfaces, laser-drilling in

nozzles and micro-cutting, to name but a few. Other materi-

als that are generally considered to be more difficult to pro-

cess, such as glass or crystal, very hard materials (hard

metals, polycrystalline diamond), ceramics or even layered

thin films (such as thin-film solar cells) can be machined us-

ing ultrashort pulses.

What does ultrashort mean? Ultrashort laser pulses are «laser flashes» that last only a

matter of pico or femto seconds. Light takes about 1.3 s to

cover the distance between the earth and the moon. In 10

picoseconds it covers 3mm, and in 200 femtoseconds just

about the thickness of a strand of human hair. In other

words, here we are talking about an unimaginably short

time.

Because of the ultrashort pulse duration, theses pulses

show, even at a low pulse energy level, outstanding peak

powers that can amount to several GW’s, which is more

than that of a nuclear power station although, of course, only

during this extremely short time.

AdvantagesThe short exposure time means that the energy is not only

precisely deposited locally, which is a general feature of la-

ser radiation anyway, but it does not then flow into the sur-

rounding area. This makes it the perfect tool to evaporate

ChallengesWhile they may be fascinating in themselves, the fact is that,

in practice, ultrashort laser pulses face competition from

other processing methods. Only when their use finally re-

sults in money being saved or made for the company will this

technology be applied by industry. In various projects (CTI,

direct commissions and student project papers), we exam-

ine the use of ultrashort laser pulses for industrial process-

es. Besides the actual process development, the focus is

also strongly on increasing efficiency. Results from our

group’s work on this clearly show that the material removal

rate pro laser energy can be maximised when moderate

pulse energy is applied. We have also developed structuring

strategies that guarantee a minimal surface roughness (e.g.

R a <100nm with copper) at very high precision. Addition-

ally, our findings show that shorter pulse durations lead to

higher ablation rates for most materials. This advantage,

however, needs to be measured against the higher system

prices.

In order to remain close to maximum possible process effi-

ciency at the high average powers necessary for high

throughput, either a large focus diameter, fast-moving rays

or parallel processes need to be employed. The first varia-

tion runs the risk of delivering less precision, the second is

hampered by the limits of today’s beam guiding systems,

while the third makes completely new demands on the opti-

cal components being used. On top of that, the mechanical

axes have to be synchronised with the laser pulse train if

they are to work at the highest possible precision; ie. the

laser works as a master and the axes as slaves. We value

co-operation when attempting to surmount challenges like

these, be it within our department (for example, with the In-

stitute for Mechatronic Systems) or with external institutions

such as the Institute of Applied Physics at the University of

Bern, or the Institute for Product- and Product Engineering

at the FHNW. We are convinced that this is how we can

make our contribution to establishing ultrashort pulses in

Swiss industry.

Contact:

> [email protected]


Ultrashort in the jargon of laser machining means that the laser radiation is only applied

for an extremely short time to produce very small structures. Do you need a hole that

is thinner than a strand of human hair? Maybe you require surface structures with

dimensions that are even smaller than 1/10mm, or perhaps cut pieces of similar

dimensions? In the laser micro-processing laboratory, these and other wishes can be

fulfilled using laser systems with ultrashort pulses.

Ultrashort and small

Dr. Beat NeuenschwanderProfessor of Applied Laser TechnologyHead of the Laser Surface Engineering GroupPhoto: Andreas Marbot

2/2012 hitech 1110 hitech 2 /2012

TUX, grayscale image translated in height information, structured in copper with ps-pulsesFigure: B. Jäggi, BUAS-EIT

Micro-dino made of sheet steel (100 micrometers thick)

Photo: B. Joss, ALPS BUAS-TI

Swiss topography in copper and detailed images of the Eiger, Mönch and Jungfrau mountainsPicture: J. Zürcher, BUAS-EIT

Micro-dino with patternPhoto: B. Joss, ALPS BUAS-EIT


This year’s International Conference on Advanced Laser Technologies (ALT12) returns to

Switzerland, exactly ten years after its first successful organisation in the Bernese

Oberland. The conference builds on 25 years of intense research collaboration between

the Russian Academy of Sciences, the University of Bern, and a dedicated team of

researchers at BUAS.

25 years of collaboration: a Russian Swiss success story

Sergei Pimenov and valerio Romano

Photo: courtesy of Sergei Pimenov, GPI RAS

2/2012 hitech 13

It is exactly 10 years since the ALT02 conference was held

in the town of Adelboden, a famous tourist resort in the

centre of the western Bernese highlands. The conference

was the tenth in a series of events dedicated to the ad-

vancement of the theory and application of laser technol-

ogy. The prestigious series was established by the Prok-

horov General Physics Institute of the Russian Academy

of Sciences in 1993. The institute was named after Nobel

laureate Alexander Mikhailovich Prokhorov, who received

the Nobel Prize for his research in the field of quantum

electronics in 1964. This year’s ALT conference returns to

the gate of the Bernese highlands – the historic city of

Thun – bringing together leading scientists and research-

ers from all over the world.

Successful partnership since 1987The organisation of the ALT conference is only the latest

event in a long and successful history of joint activities

between Russia and Switzerland: Exactly 25 years ago, in

1987, a first collaboration was established between the

General Physics Institute in Moscow and the Institute of

Applied Physics in Bern. The collaboration aimed at ex-

ploring new ways of developing and processing laser ma-

terials.

The laser material of greatest interest to the IAP at that

time was erbium-doped crystal. This material made it

possible to generate laser radiation in mid-infrared (i.e. at

3 micrometer) wavelength.

Light of this wavelength is absorbed very efficiently within

one-thousandth of a millimeter in water, and hence in hu-

man tissue; it can therefore cut tissue efficiently and very

precisely at low energy and with minimum heat-affected

zone. Prof. Weber, at that time head of the laser depart-

ment at the IAP, was investigating the use of laser radia-

tion in medicine. These interests coincided with the inter-

ests of Prof. Konov and Prof. Shcherbakov at the GPI,

which resulted in fruitful joint work in the study of laser

interaction with human tissue, as well as the spectroscop-

ic analysis of laser materials, for the purpose of generating

those wavelengths.

In 1996, this initial collaboration led to the start of a joint

research project funded by the Swiss National Science

Foundation. The project was a great success and institu-

tional partnership projects followed, facilitating regular ex-

change visits between Russia and Switzerland.

Recently, the General Physics Institute in Moscow, the In-

stitute for Single Crystals (Ukraine) and Institute for Ap-

plied Laser, Photonics and Surface Technologies at BUAS-

EIT launched a new Swiss National Science Foundation

project, which is led by Prof. valerio Romano at BUAS-EIT.

Advances in ultrashort-pulse laser technologyThe present collaboration between Russia, the Ukraine

and Switzerland forms a continuous line of research from

the activities in the past. The joint SNF project, which is

due to be completed in 2012, springs from the recent in-

terest in ultrashort-pulse laser technology. The project

aims at exploring new possibilities in material processing

with ultrashort pulses required for applications in photon-

ics, data storage, micro-mechanical and micro-optical de-

vices.

Ultrashort laser pulses, for example, can be used to pro-

duce inscribed «wires» inside diamond for electronic or

photonic applications.

For this purpose, a variety of advanced optical materials

including diamond, sapphire, lithium niobate, and na-

nocrystalline films of silicon carbide (nc-SiC) are currently

being studied. A particular goal of each potential applica-

tion is to demonstrate how much the material properties

can be changed by only ‹small› changes induced by ultra-

short pulses in micrometer- and submicrometer-sized re-

gions of transparent materials.

Joint research activities in the project focus on the synthe-

sis of nanocrystalline SiC films, the investigation of struc-

ture and optical properties, as well as laser modification

of crystals and thin films.

Ultrashort-pulse laser technology will be the subject of in-

tense interest in the research community for a long time to

come. And there is little doubt that the Russian-Swiss

partnership will continue to be at the forefront of these

developments.

Text: Patrick Studer

Contact:

> [email protected]

[email protected]


SEM picture of two holes into human hair.Photo: Courtesy of Prof. W. Lüthy, IAP, University of Bern

Two-dimensional structure (arrays of craters) with the period of 4 µm in diamond to change its optical propertiesPhotos: Courtesy of GPI RAS

3x3 array of graphitic micro-channels formed in a

0.68-mm-thick single crystal diamond plate using

1-ps-pulses (from the current project).

12 hitech 2 /2012

2 /2012 hitech 1514 hitech 2 /2012


Because of their ability to cut through 25mm thick metal plates, lasers are going to

play a major role in the future of metalworking. However, depending on the

metal, the plate thickness and the wavelength, the quality of the cut is not always

satisfactory and the workpiece needs some reworking afterwards. The Institute ALPS

at the BUAS-EIT and its partners are looking for solutions to this problem.

Cutting metal with laser is like cutting through butter

Dr. phil. nat. Marc SchmidSenior ResearcherALPS, BUAS-EITPhoto: BUAS-EIT

Ellipsometry as basic measurementAnyone wanting to achieve meaningful simulations first

needs to understand the optical material properties. For ex-

ample, during the laser-cutting process, a thin layer of liquid

metal forms at the cut front, which mainly absorbs the en-

ergy of the laser beam. For a simulation to work, one needs

to know how much of the laser beam’s energy is absorbed

by the metal and how deep the beam penetrates into it.

Consequently, refraction and absorption indices of the met-

al in its liquid form are important indicators. These material

properties are only known in the case of a few pure metals

such as silver, gold or mercury in their liquid phase, but not

for metal alloys like steel, which is widely used by the indus-

try. Therefore one of the aims of the project was to measure

the complex refraction index of liquid metals and alloys.

This was achieved with the help of ellipsometry, a method

which has been known about for more than a century. The

basic idea is that a defined polarised laser beam hits a sam-

ple at an angle φ and is reflected (see Figure 1). The polarisa-

tion of the laser beam changes through the reflection on the

material’s surface. Generally, elliptically polarised light forms

after the reflection, hence the name ellipsometry. By analys-

ing the change of polarisation after the reflection, one can

calculate the optical properties of the material. The theoreti-

cal background of ellipsometry has been well investigated ,

and the method is routinely used in the analysis of solids and

thin layers.

The crux of the measurement When determining the optical properties of liquid metals, the

main challenge is the handling and measuring of liquid met-

als. On the one hand, the surface (topology and roughness)

of the metal samples changes continuously when it is heat-

ed and liquefied. On the other hand, every change on the

surface has an effect on the reflected beam, which has to be

taken into consideration when applying ellipsometry. In or-

der to avoid unwanted reactions between the liquid metal

surface and atmospheric gases, we constructed a vacuum

chamber (Figure 2) for the experimental setup that achieves

a vacuum of about 105 mbar. Additionally, the vacuum

chamber can be flooded with an inert gas such as argon as

well. The vacuum chamber has various viewports to which

Lasers are the ideal tool when it comes to cutting plate-

shaped metals because they produce complex forms,

work quickly and precisely, and are profitable even in

small batches. In an effort to increase the quality of the

cut, researchers from the Institute for Applied Laser Pho-

tonics and Surface Technologies (ALPS) at the BUAS-EIT

got together with colleagues from the Institute of Applied

Physics (IAP) from the University of Bern as well as with an

industrial partner, Bystronic AG in Niederönz. Their aim

was to optimise the cutting process through simulation.

the ellipsometer arms and other measuring equipment can

be attached. The ellipsometer itself, which was specially

constructed for this experimental setup, is made up of a

source and a detector arm. A super-luminescent LED with a

wavelength of 1070 nm and a bandwidth of about 100 nm

serves as the light source, and a fiber-coupled spectrometer

serves as detector. The optical components of the ellipsom-

eter, for example the polarisers, of both the ellipsometer

arms are mounted on motorised rotating mounts, which can

be controlled thanks to software we have developed our-

selves.

One important part of the experimental setup is the heating.

To achieve high temperatures – the steel under examination

only begins to melt at 1660˚C – the experimental setup has

two heat sources. An electrically driven, adjustable heating

plate allows an adjustment of the metal samples during the

heating phase. This allows the samples to be heated to

about 1000˚C. Materials such as aluminium and silver melt

at these temperatures. The second heat source is a fiber-

coupled laser diode that emits at 800 nm and achieves an

output power of roughly 350 W. In this way, metals such as

copper, which melt at 1060˚C, or steel can be liquefied.

New questions for researchDuring our experiments, we were confronted with questions

that were entirely new. We needed to clarify how curved

surfaces affect the ellipsometry, because the rectangular-

shaped sample became semi-spherical during the melting

process (Figure 3). On top of that, slag from the liquid metal

resulted from contamination of the sample in the vacuum

chamber. This slag needs to be removed before the meas-

urement takes place. A skilful heating strategy, however, al-

lows the slag to be broken up and shoved to one side.

To date, simulations with our results have been promising.

Currently we are working on measuring further metals and

alloys in their liquid states so that we can extend the range

of applications of laser processing.

Contact:

> [email protected]


Figure 2: Measurement structure with vacuum chamber Photo: BUAS-EIT

Figure 3: Liquid aluminium in the vacuum chamber Photo: BUAS-EIT

Figure 1: Principle of ellipsometer measure-ment: linear polarised light beam changes polarisation after reflection on the sample surface. The reflected beam is analysed using λ/4-plate and polariser Graphic: BUAS-EIT

Dr. Andreas BurnSenior researcherALPS, BUAS-EITPhoto: BUAS-EIT

Thin-film photovoltaic (Pv) technologies are gaining ground despite their lower efficiency

compared to silicon wafer-based technologies. This trend is mostly economy-driven

and based on key advantages inherent to the technology.

Harvesting the sun more efficiently


2/2012 hitech 1716 hitech 2 /2012

In the scribing process, the thin films are removed selec-

tively along narrow lines on the panel. Three scribes per

sub-cell strip are necessary and their arrangement allows

a back-to-front electrical connection (see Figure 1). One

industrial-sized solar module can contain hundreds of

scribe meters. Therefore, it is necessary to develop highly

reliable scribing processes. The zone between the three

scribes is a non-productive area, also termed «dead-

zone», which has to be kept as small as possible. Laser

scribing addresses these problems and is rapidly emerg-

ing as one of the most significant processes for photovoltaic

elements production. It enables high-volume production of

next-generation thin-film devices, surpassing mechanical

scribing methods in quality, speed, and reliability.

Laser scribing in CIGS solar modules Solneva SA developed machines and processes for struc-

turing amorphous and micromorph silicon (a-Si, µ-Si)

thin-film cells and is now working on a solution for Copper

Indium Gallium (di-)Selenide (CIGS) cells. CIGS absorber-

based products are the fastest-growing branch in the

thin-film family thanks to their favorable properties. But

there is one important drawback: CIGS is a particularly

difficult material for laser-structuring and there is no in-

dustrial laser-based solution available for module pattern-

ing to date. Manufacturers fall back on mechanical needle

The advantages of thin-film Pv technologies are obvious:

The production process for thin-film Pv cells can be scaled

up easily to streamlined, high-volume manufacturing, and

the amount of absorber material needed (1-3 µm thick lay-

er) is much lower than for crystalline silicon cells. This leads

to dramatically lower fabrication costs per Watt peak pow-

er in high-volume production. Thin-film Pv cells show a

greater efficiency in diffuse weather conditions and high

temperatures than other materials. The enormous potential

of the thin-film Pv market is best illustrated by the projected

annual growth rate between 2009 and 2020, which is at a

spectacular 24 %.1

Innovation in the thin-film solar industry Despite these advantages, cost reduction remains a ma-

jor challenge for companies trying to make the technology

profitable. Let’s take the thin-film solar industry as a case

in point. Continuous developments need to address ways

of producing more efficient solar modules at lower cost

with less energy. Besides the obvious – the optimisation

of the absorber material – there is also an enormous po-

tential for improvement in module patterning, i.e. the

scribing of thin films between production steps in order to

build electrical interconnects (see «why interconnects are

necessary»).

Solneva Swiss Solar Tools SA in Aarberg is a young and

highly innovative company which is entering the global

market for industrial laser scribing machines. Solneva’s

unique concept rests on their core competencies in ma-

chine and laser integration, controller development, and

application know-how. Their machines are fast, reliable,

energy efficient and have a small footprint.

scribing for the P2 and P3 process. Mechanical scribing

produces up to 500 µm wide dead-zones mainly due to

chipping of the thin-films, which broadens the scribe sub-

stantially. Calculations have shown that module efficiency

can be increased by 4 % if the dead-zone width is reduced

to below 200 µm. Scientific articles published in the past

few years gave rise to the assumption that high-quality

CIGS laser-ablation could be achieved using picosecond

laser pulses.

Research collaboration with the industryIn 2010, Solneva SA started collaboration with the ALPS

institute at Bern University of Applied Sciences to benefit

from our expertise in short- and ultrashort pulse material

processing. The collaboration is funded by the Commis-

sion for Technology and Innovation (CTI). The first results

of the study are very promising. were able to prove the

existence of stable process windows for all three process

steps P1-P3 with picosecond laser sources.

We further demonstrated that dead-zone widths smaller

than 200 µm can be realis ed on functional mini-modules

using these processes for structuring. An electron micro-

graph of the scribing zone on the finished mini-module is

shown in Figure 2.

The ultimate goal of the project is to develop and build a

working prototype of an industrial all-laser scribing machine

that is adapted to the specific needs of the industry.

Contact:

> [email protected]


1 «Thin Film Photovoltaic Cells Market Analysis to 2020», GB

Why are interconnects necessary?The most important performance determining factor beside the absorber material is the electrical connection of the solar cell. While the back contact can be a thin metal film, the front contact must be transparent to the sunlight. Often, transparent conductive oxides (TCO) layers like aluminum-doped zinc-oxide (Al:ZnO) are used for this purpose. A problem arises when the area of the solar cell is scaled up: the electric current scales with the cell area (L x W) but the TCO cross section scales with the width of the cell. Consequently the current density in the TCO increases and so do the Ohmic losses.

Increasing the TCO thickness is not an option as this increases optical transmission losses. A solution to the problem is the subdivision of the solar cell into strips (sub-cells) that are connected in series.

In thin-film solar modules, interconnects are typically formed from three scribes (lines where the films are selectively remo-ved) that are made between thin film deposition process steps in industrial solar module production.An optimisation process yields the best compromise between the reduction of Ohmic losses and the total active area loss caused by the non productive «dead zone» at the interconnects. This optimisation process obviously profits from a reduction of the dead zone.

Figure 1 Cross-section through an interconnect with the three scribes P1-P3 made between the three main process steps. The P1 scribe is applied on the molybdenum-coated sheet glass substrate. Then the CIGS layer is grown on top followed by the P2 scribe which removes the CIGS and exposes the moly back contact. In the third step, the front contact – a transparent conductive oxide (TCO) layer – is deposited and patterned in the P3 scribing process. Together, the three scribes form an electrical back-to-front contact as indicated by the dashed arrow.Figure: A. Burn

Figure 2 Electron Micrograph of the scribing region on a functional mini-module. On this mini-module we demonstrated the feasibility of a dead-zone <200 µm.Photo: J. Zürcher

Dereje Etissa, a PhD student from Ethiopia, is currently working on a research project

aimed at minimising fiber scattering losses. Parts of his doctoral thesis on the

material improvement of fiber optics are carried out jointly by BUAS and the University

of Bern.

Joining Forces: Doctoral Research at BUAS and University of Bern


18 hitech 2 /2012

Rare-earth activated optical fibersDereje Etissa is currently conducting his doctoral research

in the framework of an ongoing project at the Institute of

Applied Physics. This is aimed at studying and improving

the production of rare-earth activated microstructured

optical fibers by the granulated silica method for laser ap-

plications. The results of his present research will form the

basis for a broader project in the same field that will lead

to fibers with large cores for fiber lasers and amplifiers.

Rare-earth (e.g. neodymium, erbium or ytterbium) doped

optical fibers are the active elements for fiber lasers and

amplifiers; they are incorporated in their trivalent ionic

form into the glass matrix of the fiber core where they act

as active laser media. The core of a fiber is the region in

which the light is guided, i.e. it is responsible for the wave-

guiding effect. The non-uniformities and material impuri-

ties of the core are responsible for the fiber losses through

scattering and absorption.

Two different methods are used for the production of the

doped materials: i) granulated oxides of the different spe-

cies are mixed, put into adequate silica tubes and directly

drawn to fibers; ii) the sol-gel method is used to produce

a porous glass that is already doped with the desired do-

pants, densified and then milled to a granulate. Method ii)

leads to improvements in homeogeneity and hence to

fewer scattering losses.

Dereje Etissa received his Bachelor degree in physics

from the University of Addis Ababa and after a few years

of work experience as a physicist in the Ministry of Educa-

tion in Ethiopia he continued his studies at the Institute of

Radiation Physics at the University of Stuttgart. There he

received his Master of Science in Sensor Technology and

in Physics. After the successful completion of his Master

degrees in Stuttgart, Dereje Etissa took up a research po-

sition at EMPA in Switzerland, working in the field of ex-

haust gas soot particle research, before he was offered a

PhD scholarship at the Institute of Applied Physics of the

University of Bern.

Minimising fiber scattering lossesDereje Etissa has chosen the sol-gel method because it is

very attractive if one wants to draw fibers with compli-

cated optical fiber geometries including, multicore or mi-

crostructured fibers. In both methods, after the inclusion

of dopants into a glass matrix, milling and melting is ap-

plied to obtain homogenous core material. This helps to

avoid fluctuation of refractive index and scattering losses.

Typically a fiber is then drawn by appropriately filling a

glass tube with the previously produced granulated silica

(doped silica for the core, undoped for the cladding and

empty capillaries for the holes) and evacuating the pre-

form while heating it in the drawing tower’s furnace.

The optical properties of the fabricated fiber will be char-

acterised by different analytical techniques (energy dis-

persive x-ray, electron probe microanalyses, x-ray diffrac-

tion analysis and refractive index profilometry). In this work,

particular emphasis is given to the minimisation of fiber

scattering losses.

Dereje Etissa does not know yet where his research will

take him, but he does know that his passion for physics

will guide his way wherever he goes – in Switzerland,

Europe, or, indeed, Ethiopia.

Contact:

> [email protected]

> Further information: www.iap.unibe.ch

Production of doped granualted optical fiber core material using CO2-laser at the Institute of Applied Physics, University of Bern.Photo: IAP Bern

Dereje EtissaPhD Candidate at Institute of Applied Physics, University of BernPhoto: Institute of Applied Physics (IAP), University of Bern

Refractive index profile of Yb+3, Al+3, P+5 doped optical fiber.Figure: IAP Bern

Christoph MeierProfessor of Optics,

Head of OptoLab, and scientific researchers

Photo: BUAS-EIT

In the world of medicine, Optical Coherence Tomography (OCT) is a reliable procedure

in the areas of ophthalmic examinations, skin disease and early tumor diagnosis.

Researchers at the BUAS OptoLab are taking this to a new level with Swept-Source

OCT, significantly faster and potentially cost-efficient laser systems for which they are

developing miniature solutions.

Swept-Source laser sources at the BUAS OptoLab

1/2012 hitech 21


2/2012 hitech 2120 hitech 2 /2012

OCT measurement of the iris and lens of a pig's eye at OptoLab, processed with a speckle-reduction-algorithmPhoto: OptoLab BUAS-EIT

speed. Swept Source OCT systems are made up of such

a fast tunable laser source, an interferometer, the differen-

tial amplifiers and an imaging software. «The current co-

herence length determines the measuring range within

which Swept Source measuring methods like OCT can be

used for interferometric measurements,» explains Tim von

Niederhäusern. He examined swept source lasers as part

of his Master Thesis, and came up with a new and original

measuring method that could characterise the laser at full

operating speed. Researchers at OptoLab make good use

of a broad spectrum of competence available at the Insti-

tute for Human Centered Engineering (HuCE), especially in

the areas of hardware algorithms, microelectronics, signal

processing and control engineering.

Applications for swept source laser have been demon-

strated especially in ophthalmology; for example, in the

Lasik technique (see article on Page 23). The use of swept

source laser outside the world of medicine has also been

recognised; for example, in material testing, where a sig-

nificantly higher resolution can be achieved than with ul-

trasound. «They are also being used for strain measure-

ment to monitor and guard buildings and bridges, and,

more recently, for offshore windmills, an economically at-

tractive market,» explains Professor Christoph Meier.

Hi-tech with potential for the futureChristoph Meier recognises the potential of improving the

measurement system to achieve an even higher speed and

a wider range, especially in the areas of data acquisition.

Since researchers from the Massachusetts Institute of

Technology (MIT) developed the concept of Optical Co-

herence Tomography in the early 1990’s, it has become

firmly established as a diagnostic tool in medicine. OCT

supports the measurement of the inside of light scattering

samples. Biological samples, which scatter light quite

strongly, are particularly suitable for examination using

OCT. «This allows non-invasive, 3-D images of live tissue

to be created with a resolution of just a few micrometers»,

says Professor Christoph Meier, Head of OptoLab. Opto-

Lab is a joint group made up of researchers from the In-

stitutes for Applied Laser, Photonics and Surface Tech-

nologies (ALPS) and Human Centered Engineering HuCE.

«In contrast to the ionising radiation of x-ray tomography,

OCT only emits a low light intensity, which does not affect

the biological samples in any way.»

Breeding ground for new laser applicationsNot only is OptoLab a specialist in OCT, it is also perform-

ing innovative pioneer work in this field. One such area is

the so-called Swept Source Laser (SSOCT), which engi-

neers from OptoLab and MicroLab have integrated into an

OCT system as part of a research project with the firm EXA-

LOS AG in Schlieren. EXALOS first became known through

its design, development and distribution of super-lumines-

cent light emitting diodes (SLED’s), hi-tech products that

are used in various markets. The firm has an interest in

semiconductor lasers that can be quickly tuned, as their

wavelength can be altered rapidly and precisely with the

help of micromechanic elements. These semiconductors

present a good signal-to-noise ratio and are ahead of the

competition when it comes to

3-D, non-invasive imaging methods are growing more and

more important around the world. «What’s needed is a

monochromatic laser, a large tunable spectral range as

well as a high sweep frequency. The laser must also be

easily focused or, in other words, it must be possible to

connect it to a single mode fiber,» summarises Christoph

Meier. When you leave the breeding ground that is the

OptoLab in Biel/Bienne, you won’t have to worry about

getting a job. The market is crying out for well-educated

engineers in optical technology. One example is that of

former Master student, Tim von Niederhäusern, who is

now bringing his ideas and creativity to life for our indus-

trial partner EXALOS.

The firm launched its new, high performance swept source

laser sources in January. Featuring individually adjustable

tuning ranges of up to 200 nanometers, and wobble fre-

quencies of from 2kHz to 150 kHz in a 1550 nanometer

spectrum, the new swept sources offer flexible system de-

signs for application in fiber-optical processing and optical

imaging in the frequency range. In order to maintin a global

lead in the future, the EXALOS team is relying on its skilled

research colleagues. Co-operation with the OptoLab is,

therefore, about to go to the next level.

Original text in German by Elsbeth Heinzelmann

CST Communication Science & Technology GmbH

Contact:

> [email protected]

> Further information:

www.alps.ti.bfh.ch

www.huce.bfh.ch

www.arcoptix.com

www.exalos.com

BUAS-EIT’s OptoLabThe OptoLab at the BUAS-EIT comprises a joint research group from thei Institutes ALPS and HuCe. Its core competence is optical measurement techniques, particularly optical coherence tomography (OCT), as well as opto-electric and opto-mechanical design. The team has the necessary infrastructure available to be able to carry out feasibility studies or test measurements in optical sensors within a very short time scale. In January 2005 engineers from OptoLab and from the University of Lausanne founded the spin-off firm Arcoptix as a joint project, which offers various optical measuring and analysis tools.

2 /2012 hitech 23

Lorenz Klauser, Product Manager R+D, and Lukas Kohler, Product Manager HW/R+D with the latest FEMTO LDv Z model.Photo: Ziemer Ophthalmic Systems AG

LASIK eye correction is performed in two steps. Firstly,

the doctor creates a thin film, known as a flap, over the

cornea and then folds this to one side. A femtosecond

laser is most often used at this point as it guarantees pre-

cision and safety. Using the second laser, known as the

excimer laser, the tissue under the flap is then removed.

The flap is afterwards repositioned and grows back with-

out stitches.

Z-LASIK- the latest generationThe FEMTO LDvTM being produced by Ziemer works ex-

clusively with a very high frequency of over 5 million puls-

es per second as well as extremely low pulse energies.

very small and regular laser spots can therefore be placed

side by side, resulting in a very smooth tissue section. The

low pulse energy also preserves the cornea. Furthermore,

the precise and thin Z-LASIK flap cuts of between 90 and

140 um thickness allow a cut where the cornea is thinner

or in the case of greater vision impairment. Over one and

a half million Z-LASIK operations have been carried out to

date worldwide. It holds the record as the method that re-

sults in the fewest complications, and the post-operative

recovery phase, known as «visual recovery», is also by far

the fastest.

The latest generation of Ziemer femtosecond lasers, FEM-

TO LDv Z-Models, is fitted with new improved technology,

and also has a modular structure. The advantage of a

modular construction is that it allows upgrades. In fact, all

Z-lasers can be upgraded. As a result, customers can

now not only order a laser system that is tailor-made to

their needs, but also have access to enhanced function-

alities without having to buy a new laser system. Other

functions that are not yet available on the market, such as

integrated imaging for cut monitoring (OCT based), or oth-

er surgical applications, can be added as upgrades.

Femtosecond laser systems are among the technologi-

cally most sophisticated surgical instruments being used

in ophthalmology, perhaps even in any kind of surgery. As

well as the robust production of femtosecond pulses (in

one femtosecond, light covers a distance of only 300 nm),

and the precise and speedy scanning, it also requires dif-

fraction-limited, high-performance optics. It further needs

steering hardware and software that is built with real-time

capability and is technologically safety redundant.

Other special features of Ziemer’s FEMTO LDvTM are a «a

hand-held laser applicator, and a compact basis station»

with integrated running gear, the only device which allows

mobile application. Due to its highly complex nature, only

the most highly trained staff, used to interdisciplinary

work and international communication modes, can be

employed in the development, manufacturing and distri-

bution of this system. Clearly, Switzerland is capable of

maintaining its cutting-edge position alongside interna-

tional competitors.

Text by Ziemer Opthalmology

Contact:

> [email protected]

> Further information: www.ziemergroup.com

LASIK (laser assisted in situ keratomileusis) is a laser operation on the eye that corrects

vision impairment. At present, it is the most commonly used procedure to achieve

sharp vision without the aid of spectacles or contact lenses. The guiding principle of

LASIK is that it changes the form and refractive power of the cornea and therefore

eliminates vision impairment.

Z-LASIK – eye surgery without blades

2/2012 hitech 23

Imagine that your bathroom mirror could tell you where and when it is going to rain today. You would know what clothes to put on, even before you’re fully awake. Mirrors can’t do that yet, but they might be able to soon. Help shape the future with us and develop innovative solutions that inspire our customers!

Information on our trainee programme, internships and job vacancies:

www.swisscom.ch/students

Nora Kleisli, Business IT, Business Engineer

“Exciting technical projects”

UM_Nora_210x297mm_en_QRCode_ZT.indd 1 19.07.12 09:25

Micro processing: highest intensity for less ablationIn many ways, micro processing makes more demands

on lasers than macro processing. While for the latter high

continuous power output and good beam quality are suf-

ficient, micro processing needs low average power but

very high peak intensities. This can be achieved by pul-

sing the light at a pulse duration in the area of picose-

conds (1 ps is a millionth of a millionth second). In micro-

processing applications fiber lasers are therefore pushed

to their limit. This is because what is needed is not high

average power, but very high peak power being emitted

from a surface that is smaller than the cross-sectional

surface of a strand of hair. It doesn’t take expert know-

ledge to recognise what the problem is: on the one hand,

First laughed at, then considered suitable for work that doesn’t require finesseThe research paid off. With an output of several kilowatts

in continuous wave operation, displaying optimal beam

quality and highest efficiency, continuous wave fiber la-

sers have become an alternative to conventional systems,

even to the point of replacing them on the market. At pre-

sent, fiber laser systems like these are being optimised for

use in macro processing in areas like metal sheet cutting,

hardening and welding. These are often applications that

benefit from the good beam quality of the fiber laser at

high average output. The new, smaller fiber lasers, which

are easier to integrate and more efficient, are gradually

replacing the dinosaurs of the first generation.

the generated light of such high intensity is able to ablate

steel or even diamond, on the other hand the same light

should be generated and transported at the same time in

a glass fiber laser without any side-effects (absorbtion or

non-linear effects). This is a challenge.

The company Onefive has taken up the challenge and is

developing a series of fiber lasers for micro material pro-

cessing. It is working closely with the University of Bern

(IAP) and the University of Applied Sciences (ALPS,

BUAS-EIT in Burgdorf) in the frame of a CTI project. The

aim is to get the most out of the fibers in ways that are

cost effective, efficient, and that allow easy integration

into machinery.

Onefive enjoys working with research institutes. Some-

times the universities don’t function the way industry would

wish for, but diligence and skillful coordination has produ-

ced very positive results. The BUAS has wide expertise in

When fiber lasers were first discovered about 50 years ago, shortly after the first laser

had been presented to the world, nobody really expected them to be put to any

serious use in the area of industrial applications. The maximum performance emitted

lay in the area of thousandths of a watt, and the fiber laser was deemed a curiosity, a

toy for experimental physicists.

Fiber lasers: Processing material with glass fibers


the area of laser application development and has become

an invaluable partner for companies like Onefive.

Contact:

> [email protected]

> Further information : www.onefive.com

24 hitech 2 /2012

Dr. Valerio RomanoProfessor of Applied Photonics, Head of the Applied Fiber Technology GroupPhoto: BUAS-EIT

1 Lightwaves that are doped with the rare metal erbium can strengthen the light signals that are transmitted by way of glass fibers without the need of an electronic amplifier. (Source: T. Seilnacht, PH Luzern)2 The laser beam is produced in a continuous wave operation using a constant supply of energy. The laser transmits a laser light of constant intensity. (Source: Technical Information, TRUMPF GmbH Ditzingen)

ORIGAMI - Low-noise femtosecond laser modulesPhoto: onefive

Photo: victoria-Fotolia.com

Institute for Applied Laser, Photonics and Surface Technologies

Our core competencies are• Fibertechnologiesforlaserapplications• Materialprocessingwithlasers• Changes in the properties of boundary layers with heat or laser treatment • Applicationofthinfilms• Development of optical measuring systems for the

analysis, processes control and quality assurance • Materialsandsurfaceanalysis• Topographicmeasurementsintheµmandnmrange

We use our know-how to develop solutions jointly with our industrial partners in research and development projects. These solutions contribute to the efficient pro-duction of goods and ensure or improve their quality.

alps.ti.bfh.ch

We develop new methods and techniques for the energy- and material-saving production of materials and their analysis.

interaction between focussed laser beam and copper

surface, as the metal has to melt.

Engineers at ROFIN-LASAG came up with the clever idea

of merging a laser pulse of 532 nm wavelength (green)

with a laser pulse of 1 micrometer wavelength (infrared).

«Because the green wavelength is initially better absorbed

than the infrared one, the copper surface heats up, the

temperature of the copper rises and thus the absorption

of both wavelengths is achieved,» explains the Head of

Development, Dr Christoph Rüttimann. If the absorption

values are high enough, the variations of the surface char-

acteristics (e.g. oxide layers) are less notable. The clever

solution lies in the amalgamation of both pulses: using the

pure infrared on its own could mean that the copper sur-

face doesn’t melt, whereas it is visible when the pure

green is used. Merging the pulses results in a considerably

enlarged molten pool.

The story of Swiss laser technology only really began in

January 1965, when the company known as Watch Stones

AG in Thun, producer of rubies for watch bearings, com-

missioned the University of Bern to research possibilities

for drilling watch stones with lasers. 7 years later, a Laser

Development Center was set up in Thun, followed by the

company LASAG in 1974.

Non-ferrous metals: a hard nut to crackTheir lasers are in demand all over the world in almost all

areas of manufacturing industry. However, laser welding

of copper materials continues to challenge the experts. All

efforts to solve the problem to date have resulted in pro-

cesses that were not efficient enough and had a low re-

producibility. The challenge with non-ferrous metals is

that, due to their high reflectivity at the common laser

wavelength of 1 micrometer, the welding results can vary

enormously, which reduces the level of processing relia-

bility. Because a high proportion of the induced radiation

is reflected, the metal hardly heats up at all. Yet a require-

ment for thermal laser material processing is the direct

Minimum investment for maximum effectTo start with, a high intensity of the laser pulses is aimed

at through use of a skilful process. The combined infrared

and green beams warm the surface of the copper until the

infrared absorption is high enough and the metal begins

to melt. Then the pulse power is reduced. «Although only

a little green is converted, the absorption of infrared is

high enough during the melting phase and welding with

infrared can continue,» says Christoph Rüttimann. The ex-

tension and the penetration depth of the weld spot de-

pends on the length of the welding phase. At the end of

the pulse, the performance can be shut down in a given

time period, as this determines the cooling phase and, as

a result, the metallurgical and mechanical properties of

the weld. A comparison between welding done with infra-

red alone and with a mixture of infrared and green shows

that the reproducibility of the welding is considerably

higher when done with the combined model, and that no

flaws appear.

The innovative aspect of this is the converting module, the

so-called GreenMix Add-on-Box. This takes over the con-

version of the green at the output of the laser resonator,

and looks after the programmable wavelength mix bet-

ween 532 nm and 1064 nm via intelligent pulse shaping.

The laser beam is safely fed into highly reflective materials

like copper and precious metals through an optical fiber

and a processing head, which ensures efficient use of the

total laser energy available for the welding process. Preci-

sion welding on the tiniest diameters of 25 micrometers is

suited for medical applications, for example for cardiac

pacemakers, and in the electronics industry, for example

for copper bonds or electrical contacts.

When it comes to cutting, welding, drilling or ablating materials, ROFIN-LASAG,

with headquarters in Thun, is one of the global leaders in lasers for high-precision

materials processing. The company has done pioneer work with the GreenMix

laser, which facilitates reliable and reproducible copper welding, an area which

even today continues to pose a challenge to industrial applications.

ROFIN-LASAG: Pioneers in laser welding of copper


What makes it interesting for the user is the fact the ROFIN-

LASAG system only needs one laser source to produce the

wavelength mix, which has a positive effect on investment

costs.

Contact:

> [email protected]

> Further information: www.lasag.com

The ROFIN-LASAG AGLASAG AG has been developing and producing industrial solid-state lasers for almost 40 years. Their products for precision cutting, spot welding, drilling and scribing are used in medical equipment, in electronics and precision mechanics as well as in the automotive and aviation industries. The October 2010 takeover by ROFIN-SINAR allowed the traditional Thun-based company to become even more dynamic and, in line with the company's vision, to be the most successful producer of solid-state solutions for precision processing.

2/2012 hitech 2726 hitech 2 /2012

Welding laser in actionPhoto: uwimages-Fotolia.com

ROFIN-LASAG's solid-state

lasers performing precision work on the smallest surface area.

Photo: ROFIN-LASAG AG

This is why the company SILITEC, based in Boudry, is

breaking new ground with its patented sand technology.

A tube made out of silicone dioxide is filled with sand,

which is, for example, doped with rare earth elements,

particularly with ytterbium and erbium. Silitec engineers

place a second tube, this time of larger diameter, over the

first one and fill the space between the two with pure or

doped sand. They then remove the inner tube, which leaves

a good interface between the inner sand core and the out-

er sand layer which later make up the cladding. The Silitec

team then heats up the whole structure and, at the same

time, begins a pure gas treatment. This guarantees that all

of the sand is glazed and that a solid preform results.

The need for flexibility«The sand method is a flexible process which allows the

core to be doped with rare earth oxides, the difference in

the refractive index to be perfectly set, and finally to

achieve a larger core diameter,» explains plant manager

Frédéric Sandoz. Sand technology also makes it possible

to produce multi-core fibers, in which the Silitec team

mount various doped core rods. «This process is particu-

larly suited to achieving non-symmetrical structures, such

as polarisation maintenance or an eccentric arrangement

of the core materials.» Thanks to their new manufacturing

method of using doped silicone dioxide powder, research-

ers from Silitec are breaking new ground in the area of

manufacturing active fibers for laser applications. Now

they are in a position to provide large and highly active

cores with a very uniform refractive index without the

need for expensive production equipment.

«The index difference between the core and the cladding

can be achieved in a smaller and more homogeneous way

than with traditional methods,» says Frédéric Sandoz.

This allows the realisation of fiber lasers which have a 74%

higher degree of efficiency in relation to the initial pump

Industrial manufacturers have only been using the high beam quality of fiber lasers

for the last few years. Their high power density on the workpiece enables speedy

processing when using suitably designed systems. Special fibers are necessary to

produce suitable lasers, and this is where production has hit a barrier. The compa-

ny Silitec in Boudry is in a position to offer a way over it.

SILITEC – more efficiency and fewer costs thanks to sand


capacity. The production process is the key to the manu-

facturing of highly doped, large cores with a very high index

contrast, and cost-efficient, high-performance Large-Mode-

Area (LMA) fibers with a single mode management.

Original text in German by Elsbeth Heinzelmann

CST Communication Science & Technology GmbH

Contact:

> [email protected]

> Further information: www.silitec.ch

The trick with the sandThe last 10 years have seen an increase in the perfor-

mance of fiber lasers, during which time they have be-

come a real alternative to solid-state lasers. On the nega-

tive side, however, non-linear disruptions such as inelastic

scattering severely affect efficiency. A single-mode laser

beam is necessary to evenly distribute the power of the

light on the inside of the beam. Active Large Mode Area

(LMA) fibers can enlarge the core diameter, afford a more

exact control of the core and, especially, the refractive in-

dex, which has to be uniform and homogeneous. A micro-

structured fiber technique with the «stack and draw»

method allows the beam to be evenly distributed and, in

combination with the Multidrawing Method, a diameter of

60 micrometers. However, such sophistication is hardly

possible when using a classic procedure like MCvD.

The production of optical fibers is a delicate operation but

it always starts with the so-called preform, which is

equipped with the characteristics of the subsequent fiber.

This cylinder made of quartz glass is coated on the inside.

Using the Modified Chemical vapour Deposition (MCvD

process), gases are repeatedly fed through it and modi-

fied until the raw materials in the inner surface of the cyl-

inder have melted, and layers with a different refractive

index have been formed.

28 hitech 2 /2012

In 1978, Silitec was one of the first companies in the world to produce optical fibers. Today, their highly original sand technology enables them to produce optical fibers that perform at the highest end of the scale.Photo: Silitec SA

SILITECWhen today’s plant manager at SILITEC, Frédéric Sandoz, developed the first optical fiber with his fellow-workers in 1978, he became one of the first producers worldwide that dared enter this new territory. Since then, innovation has become a watchword, and the partnership with Professor valerio Romano from the Institute for Applied Laser, Photonics and Surface Technologies at the BUAS-EIT has become an extremely important element of this philosophy. Today, the company has become a pioneer with its patented sand technology, a method which stands for high performance and cost-efficiency. SILITEC’s special optical fibers are used in the worlds of industry as well as in telecommunica-tions, medicine, the military and aviation. They are equally used in measuring equipment and instruments, but are especially valued for client-specific applications

Preform for a microstruc-tured fiber. The sand that has not yet been melted is visible in the upper part of the preform. Photo: Silitec SA

2/2012 hitech 29

Jan RichardM.Sc., EMBAManagement Center Bern

There are enormous opportunities for Swiss exporters in

the emerging economies. The exports to the BRIC coun-

tries are expected to increase by 11% to 19% per annum.

This means that exports to the BRIC states are expected to

almost triple within seven years. By extrapolating these de-

velopments until 2030, the BRIC countries will make up a

market share of nearly 45% of the Swiss exports1.

In addition to the opportunities in the new markets, it is also

important to examine the potential risks which could lead

to problems when entering the emerging markets, such as

legal security, bureaucracy or poorly developed logistics,

as well as the lack of internal readiness to do business with

the emerging markets. It is important to identify the poten-

tial risks in good time in order to be prepared for them and

to be able to react correctly.

The Fit2GlobalizeTM method helps companies to assess

all the relevant factors associated with a market entry. Us-

ing this method, companies can process the relevant infor-

mation in order to develop a country-specific market entry

strategy. The method incorporates two dimensions: the ex-

ternal dimension shows the opportunities and risks in a for-

eign market, whereas the internal dimension demonstrates

one’s own strengths and weaknesses with regard to inter-

national business. It is this latter dimension which is often

underestimated: one of the strengths of this method is that

it also clearly shows, apart from the potential of a foreign

market, whether a company is actually ready to work at an

international level.

On the basis of the answers to two sets of 25 questions2,

each pertaining to the market situation in a country and

the internal situation of the company, the opportunities

and risks, as well as the strengths and weaknesses are

compiled. The questions related to the foreign market

deal with the political, social, economic, legal and techno-

logical situation of a target country. The customer and

competitive situation and the market potential are also the

topics of the external analysis. Using the questions related

to the internal situation of a company, its management,

core business and support processes are assessed with

regard to its readiness for international business. Many of

the questions related to the individual export markets are

answered by accessing the evaluations of specialist infor-

mation providers, such as the World Bank, the IMF, Euler-

Hermes, Transparency International, doingbuisness.org,

Human Development Index, heritage.org, WTO, geert-

hofstede.com and others. This ensures that decisions are

not made on the basis of a «gut feeling», but on the basis

of neutral evaluations. The results of the method include

an Attractiveness/Readiness Portfolio, a SWOT3 analysis

and a To-do-List with regard to the identified weaknesses

and risks. Finally, different markets are compared in order

to facilitate decision-making when it comes to prioritising

external business.

In the Market Attractiveness/Readiness Portfolio (Illustra-

tion 1), depending on the position of the analysed market,

four standard approaches are suggested: for the com-

pany taken as an example in Illustration 1, «Italy» is a mar-

ket which should be developed because the market is at-

tractive and the company is ready to do business with

Italy. The potential is, however, limited. In contrast, al-

though China displays great potential, the company is not

yet ready to do business in China. Therefore, the standard

strategy «Do homework» would be effective in this case.

The homework is defined based on the risks of a market

and the weaknesses of a company, which are the results

of the answers given to the questions listed in the method.

The «homework» is displayed as suggested actions in a

To-do-List.

The companies should concentrate on the markets in the

first and second quadrant. The markets in the fourth

quadrant should not be dealt with for the time being, and

those in the third quadrant only at a subordinated level –

e.g. in case of very low entry barriers.

Economic growth has shifted to the emerging economies. These new markets are also

attractive to the many Swiss companies. At the same time, the opportunities in the

enormous market potential are often accompanied by risks to which the companies in the

traditional export markets are less exposed. To ideally examine the opportunities and

risks associated with a market entry, the Market Entry Evaluation Method Fit2Globalize™

was developed in the Management Center of Bern University of Applied Sciences BUAS

in a research project supported by the BUAS Department of Engineering and Information

Technology research fund.

Well-prepared to start international business with Fit2GlobalizeTM

Sooner or later, many engineers deal intensively with the

development of foreign markets – since most of the Swiss

small and medium-sized enterprises (SMEs) are heavily

dependent on the export trade. Therefore, to assist the

said SMEs, the Management Center in Bern offers the Ex-

ecutive MBA in International Management based on the

concept of lifelong learning. Fit2GlobalizeTM is used in this

course (www.emba.ch) and in consultancy projects. The

students use the methods in the course of a market entry

study to be written by them during their stays abroad in

China, Russia or the USA. The findings are very often of

great interest to the companies. The key benefits of the

method are that all the relevant questions and topics

come to light, the findings are neutral and can be suc-

cessfully used as a basis both for discussions and for the

definition of a market entry strategy.

Contact:

> [email protected]

> Further information: www.emba.ch

www.fit2globalize.ch

Dr. Paul AmmannHead of Program EMBA-IMManagement Center BernPhotos: BUAS-EIT

1 Source: Credit Suisse, Exportindustrie Schweiz – Erfolgsfaktoren und Ausblick, 20112 See www.fit2globalize.ch for the list of questions 3 SWOT: Strengths, Weaknesses, Opportunities and Threats

Illustration 1: The MarketAttractiveness / ReadinessPortfolio of Fit2GlobalizeTM

Figure: M. Signer

Executive MBA program based on the concept of lifelong learningThe Management Center in Bern (www.mzbe.ch) supports university graduates with customised post-graduate education programs based on the concept of lifelong learning throughout their entire career after their first degree. One of these programs is the Executive MBA in International Management (www.emba.ch), which prepares the students for international challenges. Fit2GlobalizeTM is an integral component of this post-graduate study.

China is a market with great potential for Swiss companies.

view of Hongkong. Photo: Fotolia.com

Fit2GlobalizeTM -Portfolio

Mar

ket A

ttra

ctiv

enes

s

Readiness forinternational business

Diameter of the circle representing the market potential of a country

+

+-

2. Do homework

4. Do not developthe market

1. DevelopMarket

3. Process as third level priority

CHINA

ITALY

I N T E R A N T I O N A L B U S I N E S S

30 hitech 2 /2012

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