(Waveguide theory and) photonic circuit...

2572-2

Winter College on Optics: Fundamentals of Photonics - Theory, Devices and Applications

A. Melloni

10 - 21 February 2014

Dip. Elettronica, Informazione e Bioingegneria Politecnico di Milano

Italy

(Waveguide theory and) photonic circuit design

7th Optoelectronics & Photonics Winter School: Physics and Applications of Optical Resonators – A. Melloni, Politecnico di Milano

(Waveguide theory and) photonic circuit design

A. MelloniDip. Elettronica, Informazione e Bioingegneria

Politecnico di Milano, Italy

Winter College on Optics: Fundamentals of Photonics Theory, Devices and Applications

7th Optoelectronics & Photonics Winter School: Physics and Applications of Optical Resonators – A. Melloni, Politecnico di Milano

Waveguide theory and photonic circuit design

- Waveguides (no theory…)- The role of index contrast in waveguides (survey of technologies, type of

waveguides, index contrast…)- Bends and advanced topics on bends (the matched bend,...)

- The dark side of integrated optical waveguides (backscatter, xtalk, losses, spurious modes, the (ng-neff) role….)

- An excursus on ring resonators: history, spectral characteristics, applications, ...

- Circuits: MZ, rings, higher order filters, delay lines, …- The circuit approach (building Blocks, Circuit simulators and few slides on Aspic, our circuit simulator that will be used at the end of the course for

hands-on session).- The structure of generic foundries and available generic foundries

A. Melloni

Let’s combine rings

ORES School, Levico, 2013 A. Melloni

from Ring to Rings…

A. Yariv Caltech 1999 Microwave

C. Madsen Bell Labs 1999 DSP

R. Orta Politecnico Torino 1999 DSP

A. Melloni Politecnico Milano 2002 Microwave

V. Van Maryland Univ. 2006 Electronic/Microwave

Books from I. Chremmos, O. Schwelb, D.G. Rabus, J. Hebneer, ….


from Ring to Rings…

Parallel coupled bandstop filter

Directly coupled bandpass filter (CROW)

Ring-loaded Mach-Zehnder filter


Ring loaded Mach-Zehnder

FSR

2N

2(N+1)

APF allows to shape the phase response

1()

2()


Tunable bandwidth filterTunable bandwidth filter

kckc

kr

Lr Lr

kr

Bandwidth tunability is obtained by varying

FSR = 200 GHz

B = 23 GHz … 175 GHz

IL < 0.6 dB

ER > -18 dB


Coupled resonatorsCoupled resonators

8


Direct coupled cavities vs cascaded cavities

Direct coupled cavities(CROW)

-1 -0.5 0 0.5 1-25

-20

-15

-10

-5

0

Frequency

Tran

smis

sion

[dB

] 1

25

Cascaded cavities(SCISSOR)

-1 -0.5 0 0.5 1-25

-20

-15

-10

-5

0

Frequency

Tran

smis

sion

[dB

]

1

25


-1.5 -1 -0.5 0 0.5 1 1.5x 104

-50

-40

-30

-20

-10

0

Tran

smis

sion

[dB

]

Frequency [GHz]

B=22THz

-1.5 -1 -0.5 0 0.5 1 1.5x 104

-50

-40

-30

-20

-10

0

Tran

smis

sion

[dB]

Frequency [GHz]

B=22THz

-1500 -1000 -500 0 500 1000 1500-5

-4

-3

-2

-1

0

Tran

smis

sion

[dB]

Frequency [GHz]

K=0.01

1st order cavity d=/2

B1 cavity=1.2 THz

BCROW=22.5 THz

10 cavities 100 cavities

1 cavity

B=1.2THz

Identical cavities ?


/4

CROW

Frequency [GHz]

|H(f)|2

[dB]

-14 dB 0 dB

CROW impedance matching

11

ZW neff

ZCROW 2ng ()

Quarter-wavematching

No impedance matching

neff( / 4 ) neff 2ng


Impedance Matching (Apodization)

ZW neffZCROW 2ng ()

Quarter-wavematching

No impedancematching

neff( / 4 ) neff 2ng

...


IN

THROUGH

Coupled ring resonators

DROP

f0 f0 f0 f0 f0 f0

K0

K1 K2 K3 K2 K1

K0

ProgressProgress in tuneable ringin tuneable ring--CROW CROW

2010

2009

2008

2007

2009


N x 40 μm

56 μ

m

F. Morichetti et al., The first decade of coupled resonator optical waveguides: bringing slow light to applications.

Laser & Photonics Reviews, 6: 74–96 (2012)

A. Melloni

Wavelength [nm]

Inte

nsit

y [d

Bm]

Return loss: -15 dB; IL 0.5 dB; In-band ripple <0.2 dB; Off-band rejection >50 dB

8-rings Bandpass filters in SOI

A. Melloni

8-rings Bandpass filters in SOI

Wavelength [nm]6 8 10 12 14 16 18 20 22 10-1210-11

10-1010-910-810-7

10-6

10-5

10-4

10-3

10-2

OSNR over 0.2 nm

BER

Waveguide

λ=1536.27 nmλ=1550.42 nm

λ=1564.75 nm


Thermal tuning

8 rings

7 rings

6 rings

5 rings

4 rings

3 rings

1556 1558 1560 1562 1564 1566

-70

-60

-50

-40

-30

-20

Wavelength [nm]

Tran

smis

sion

[dB]

Si

Si

SiO2

Spin‐on glass

w

h

wh

NiCr Au

Thermal crosstalk

=2.5 nm

7 m

28° C 0.7° C

hot ring

cold ring

=0.06 nm

A. Melloni

Tunable Delay lines


On-Chip Tunable delay… not an easy task !!!

Electronic

Microwave

Photonics - let photons run around (coil of fiber)

– slow down photons

out


Recirculating buffer

Technologies: 2007 Glass for the spire + InP for the switch2010 All Silicon (15 dB/ns)

Spires

Switches

Trade off between waveguide attenuation and switch ER (limit)

Discrete delay line, Packet(s) delay and Buffer

Courtesy of John Bowers, University of California, Santa Barbara INTEL 2010


Slow down photons

velocity c

group refractive index

ng of the material: Atomic resonances, band edge, EIT, CPO,…

ng of the circuit: Resonators, Bragg Gratings, Photonic Crystals, Brillouin and Raman,…

Tran

smis

sion


Slow down photons


Tunable Delay lines

IN

OUT

open ringsclosed rings

λr = λin λr ≠ λin

F. Morichetti et al., Optics Express, Vol. 15, 25, December 2007A. Canciamilla et al., Journal of Optics, IOP, 2010A. Melloni et al., IEEE Photonics Journal, vol. 1, no. 4, 2010

1 byte continuously tuneable delay at 10 and 100 Gbit/s demonstrated


-200 -100 0 100 200 300 400 500

0

0.2

0.4

0.6

0.8

1

Inte

nsit

y

Time [ps]

In

In

Locked rings(off-resonance)

Out

in

r ≠in

Minimum delay

The CROW in reflection

-20 -15 -10 -5 0 5 10 15 200

50

100

150

200

250

300

350

Frequency [GHz]Frequency [GHz]

Del

ay [p

s]


-200 -100 0 100 200 300 400 500

0

0.2

0.4

0.6

0.8

1

Inte

nsit

y

Time [ps]

20In

In

Out

M = 2

Open rings(on-resonance)

Locked rings(off-resonance)

r ≠in

in

Frequency [GHz]

Del

ay [p

s]

The CROW in reflection


-200 -100 0 100 200 300 400 500

0

0.2

0.4

0.6

0.8

1

Inte

nsit

y

Time [ps]

4

0

2

In

In

Out

M = 4

r ≠in

Open rings(on-resonance)

Locked rings(off-resonance)in

F. Morichetti et al., Optics Express, no. 25, Dec. 2007

R-CROW: a reconfigurable delay line

Frequency [GHz]

Del

ay [p

s]


R-CROW continuous tuning


In

100 ps Intensity modulationOOK NRZ @ 10 Gbit/s

Data transmission at 10 Data transmission at 10 Gbit/sGbit/s

OutReconfiguration

- hitless- time 100 s- power 5 mW


0 20 40 60 80 100 1200

1

0.8

0.6

0.4

0.2

TuneableTuneable pulse delay @100Gbit/spulse delay @100Gbit/s

Delay [ps]

Nor

mal

ized

inte

nsit

y

Fractional delay = 7.5 ps/RR

9 ps

11 ps

89 ps (8 bits)

(0)

(4)(8)

(12)

In10 ps

Out

τ

B = 87 GHz

Fractional loss≈ 1.1 dB/bit

Storage efficiency0.66 bit/RR

Pulse Broadening (1 byte)≈ 20%

ORES School, Levico, 2013 A. Melloni systems

GenericFoundries

Final Users

High level circuit designHigh level circuit design

Final User: PICs design at a circuit level using a selected set of elementary functional elements (BBs), according

to well defined rules (DKs)

materials

technol.

waveguides

devices

circuits

packaging

modules

BuilidingBlocks

Design kits


3,46

3,47

3,48

3,49

3,5

3,51

3,52

3,53

1 2 3 4

grou

p in

dex

width [um]

TE

TM

fundamental mode

Higher order mode

TE

TM

Simulation

exp

Characterization

ModellingModelling of photonic Building Blocksof photonic Building Blocks

EM analysis

Numerical simulations

E jBH jD J

B HD

S

BB model

• realistic model • no information on geometry & materials • access only to input/output port waves

• very fast, suitable for large circuits

Circuit approach(high abstraction level)


BBs of the SAPPHIRE platformBBs of the SAPPHIRE platform

Straight & bent waveguides

Directional couplers

Waveguide crossing

Bragg gratingsIn/Out mode adapter

Ring resonators

Grating assisted coupler (GAC)

Heaters

BBs of the SAPPHIRE platformBBs of the SAPPHIRE platform

Straight & bent waveguides

Directional couplers

Waveguide crossing

Bragg gratings

In/Out mode adapter

Ring resonators

Grating assisted coupler (GAC)

Heaters


Design kitsDesign kits

Lc

K

tB

tX

,BB model

Analytical model(S matrix)

Circuit parameters & variables

Mask layout

SAPPHIRE design manual

Release 1 (July 2012)

Design rules‐ BB connections

‐ validity range of the model‐ layout constraints‐ quality assessment

‐ …


Libraries for ASPICLibraries for ASPICTMTM simulatorsimulator

1600 BBs; 100 lambda points 1 min

www.aspicdesign.com

Direct exportation of the mask layout

Play with realistic BB

SAPPHIRE BBs

Phoenix


ww

w.a

spic

desi

gn.c

om

CITCUIT SIMULATOR

ww

w.p

hoen

ixbv

.com

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