Matthias Hillenbrand, Eric Markweg, Martin Hoffmann, Stefan Sinzinger:
Integrated hybrid GRIN lenses
Zuerst erschienen in: DGaO-Proceedings. - Erlangen-Nürnberg: Dt. Gesellschaft für angewandte Optik, ISSN 1614-8436. - Bd. 113.2012, P5, insg. 1 S. URN: urn:nbn:de:0287-2012-P005-2
Design Principle: Independent wavefront in two perpendicular directionscontrol
Direction 1: Perpendicular to the substrate
· GRIN element, variation of the refractive index during the layer deposition process
· Description of the refractive index profile:
Direction 2: Parallel to the substrate
· Etching process with perpendicular, optical quality side walls
· Element shape determined by 2D-profile of the lithographic mask
www.tu-ilmenau.de
Technische Universität Ilmenau®IMN MacroNano
Fachgebiet Technische Optik
Matthias Hillenbrand
Telefon: +49 3677 69-1276
Fax: +49 3677 69-1281
www.tu-ilmenau.de/optik
ReferencesThe authors would like to thank the German Federal Ministry of Education and Research and the Thuringian Ministry for Education, Science, and Culture for the financial support through the projects “Kompetenzdreieck Optische Mikrosysteme-KD OptiMi” (FKZ: 16SV3700) and “Graduate Research School on Optical Microsystems Technology (FZK: PE 104-1-1).
Acknowledgements
Macro ®NanoM. Hillenbrand, E. Markweg, M. Hoffmann, S. SinzingerIMN MacroNano , Technische Universität Ilmenau
®
Integrated Hybrid GRIN Lenses
Advantages· low cost by mass production (semiconductor technologies)· high reliability· high precision in geometric dimensions and positions (defined by lithography mask)· can be combined with integrated photonic elements on the same substrate· high refractive index range
Exemplary applications· efficient coupling structures between integrated optics and free space· beam shaping for integrated laser diodes
Challenges · 2D structuring for 3D functionality· High transmittance
Achievable parameters· Maximum height of the structures dependent on deposition
time; structures with 30µm GRIN layer height realized· Realized minimum feature size: 2 µm (DOE period)· Possible refractive index range: 1,47-1,85
[1] J.-i. Shimada, O. Ohguchi, R. Sawada: Gradient-index microlens formed by ion-beam sputtering, Applied Optics 31 No. 25, 5230 (1992)[2] D.R. Beltrami, J.D. Love, A. Durandet et al: Planar graded-index pecvd lens, Electronic Letters 32
No. 6, 549 (1996)
Wafer-level optics
sensor 1
sensor 2
single-
mode fiber
measure
beam
mirror
thermooptical
modulator
GRIN-
lense
mirror
Concept and prototype of a wafer-level interferometer for displacement measurements
variableGRIN-profile
Variety of diffractiveand refractive shapes
depostion of a ICPCVD film(SiO2/SiON)
electro-patterning of nickelstructured by UV-lithography
fluorine-based ICPRIE deep etching
separation and testingof the optical elements
Technology and experimental results
Design
Fabrication using semiconductor technologies
Design process· Raytracing-based optimisation· Simultaneous variaton of the refractive or
diffractive shape and the GRIN-profile· Merit function based on the wavefront
aberration of the output beam
refractive index
vert
ical p
osi
tio
n
Cylindrical Acylindrical Diffractive
Experimental setup for laser beam collimation
Beam profile at 15mm distance from the lens
collimated uncollimated
1/e^2 gaussian beam radius behind the GRIN lens
1/e
^2
beam
rad
ius
in m
m
distance from lens in mm
1,480
1,490
1,500
1,510
1,520
1,530
1,540
-10 -5 0 5 10
optimised refractive index profile
realised refractive index profile
stepped index profile of the produced elements
vertical position in µm
refr
act
ive in
dex
0
5
10
15
20
25
30
1,460
1,510
1,560
1,610
1,660
1,710
1,760
-5 5 15 25 35 45 55 65 75 85 95
refractive index of silicon oxynitride (500 W; 10 mTorr; SiH4 : 6sccm; 380 °C; gasratio N2O+N2= 100sccm)
gasratio vs refractive index at 380°C
deposition rate
gas ratio N2O
(N2 + N2O = 100 sccm)
refr
act
ive in
dex
dep
osi
tio
n r
ate
in
nm
/min
sensor 11
DGaO-Proceedings 2012 - http://www.dgao-proceedings.de - ISSN: 1614-8436 - urn:nbn:de:0287-2012-P005-2
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