GHz photonics on a Silicon Chip

- Cornell Nanophotonics Group - nanophotonics.ece.cornell.edu

GHz photonics on a Silicon Chip

Michal LipsonSchool of Electrical and Computer

EngineeringCornell University

nanophotonics.ece.cornell.edu


Optical Devices in Si Structures• High index contrast – tight optical confinement

compact structures, much smaller than the wavelength dispersion engineering

• Massively parallel devices enable ultrahigh bandwidth processing

LightLight

High indexHigh indexcorecore

nn ~ 3.5 ~ 3.5

Low-index cladding cladding

nn ~ 1.5 ~ 1.5

300 X 500 nm


Loss: Propagation and Bending

propagation loss:

waveguide: 445 nm X 220 nm, wavelength 1500 nm, TE-like

1.06.3 ± dB/cm Vlasov (IBM)


Achieving Low Losses with EtchlessSilicon Waveguides

Si

SiO2

Si

SiO2

Si3N4

Si

SiO2

Si

SiO2

Si

SiO2

Si

SiO2

e-beamresist


Dispersion-Engineered EtchlessWaveguides

• Etchless Si waveguides engineered for 0-GVD at 1550 nm.• Waveguides dimensions: 315-nm high by 1-µm wide.• Losses less than 0.3 dB/cm.

Example of thin (100-nm high) etchless siliconwaveguide profile cross-section


Scanning electron micrograph of a ring resonator

Diameter = 12μm

Width = 450nm

Gap = 200nm

BOx: 3μm

Si: 250nm

Si Substrate

BOx: 3μm

Si Substrate

BOx: 3μm

Si Substrate

Width = 450nm

BOx: 3μm

Si Substrate

p+ (B) n+ (As)

Ebeam Lithography EBeam Resist

Oxide Deposition

Etching using RIE

Via Hole Etching and Ion Implantation

BOx: 3μm

Si Substrate

Contact MetallizationMicroscope image offabricated opticalmodulator withelectrical contacts

Fabrication


Micrometer Scale Silicon ElectroopticModulator At 20 gbps

>9dB modulation depth!

PRBS 210-1

Q. Xu, M. Lipson, Optics Express Feb 2007


Silicon substrate

Silicon Photonics

Buried oxide

Combining optics and electronics on asilicon chip

Silicon-on-Insulator (SOI)250 nm

450 nm

Silicon (n = 3.5)

Silicon dioxide (n = 1.5)

Commercial SOI wafer:

IBM:


CMOS IntegrationIBM:

“Front end”transistor layer

“Back end”metal layers

…

Where does silicon photonics fit?

Vertical integrationDeposited silicon layer above the front end?

500 nm


Deposited Silicon

Silicon dioxide

Side view

Crystalline grains: vertical, ~300 nm

Grain Boundaries: amorphous Si, ~1 nm thick

Grain size ≈ Device size

Cross-section TEM of crystallizedLPCVD film

Previously shown passive waveguides, filters Kimerling et al. (MIT)Lipson (Cornell)Baets (Belgium)

Now demonstrating active device electro-optic modulator


Poly For Active Electro-optic Devices


Poly For Active Electro-Optic Devices

• Carrier mobility µ = 100cm2/V·s (only a factor of10 less than crystallinesilicon

• 2.5GHz speed!


Integration of Optical Interconnect


4 1

@1.5

1.86 10Si m

dnK

dT µ

! !" #= $% &

' (

Ring Resonators for Switching

Dong, P., Preble, S.F., and Lipson ,M.., All-Optical Compact Silicon CombSwitch, Opt. Express, Vol. 15, No. 15, 23 July 2007


Proposed Hitless Network

South

Input

East

Input

South

Output

East

Output

North

Output

North

Input

West

Input

West

Output

R1

R2 R3

R4R5

R6 R7

R8-Allows for parallel hitless routing-spatially non-blocking,-One dedicated waveguide for each input-output combination.

w/ Keren BergmanColumbia University


Thermal Effects Max: 284.54

Min: 26.85

50

100

150

200

250

156.0Si

W

m K! =

"

2

1.4SiO

W

m K! =

"

Thermal coefficients

Heat is conducted two ordersmore efficiently in Si than SiO2

Efficient heating requiresproximity to heater.

Nearby rings experienceminimal thermal crosstalk

Si Ring

Heater


Fabricated Network

Nicolás Sherwood-Droz, Howard Wang, Long Chen, Benjamin G. Lee, Aleksandr Biberman,Keren Bergman, Michal Lipson1, “Optical 4x4 Hitless Silicon Router for Optical Networks-

on-Chip (NoC)”, submitted for publication


Network Performance

1553.4 1553.7 1554.0

-20

-10

0 R6 Switch Off R6 Switch On

No

rth

-Ea

st

(Th

rou

gh

-Po

rt)

No

rma

lize

d T

ran

sm

issio

n (

dB

)

Wavelength (nm)

1553.4 1553.7 1554.0

-20

-10

0 R5 Switch On R5 Switch Off

We

st-

Ea

st

(Sw

itch

-Po

rt)

No

rma

lize

d T

ran

sm

issio

n (

dB

)

Wavelength (nm)

< -20 dB crosstalk


Nonlinear Optical Devices In Si Structures

• High index contrast – tight optical confinement compact structures, much smaller than the wavelength enhanced nonlinearity (1000 X silica) dispersion engineering

• Massively parallel devices enable ultra-high bandwidthprocessing.

LightLight

High indexHigh indexcorecore

nn ~ 3.5 ~ 3.5

Low-index cladding cladding

nn ~ 1.5 ~ 1.5

300 X 500 nm


Phase-Matched Four-Wave Mixing

• Broad regions of FWM gain predicted.

Foster et al. (2006)Lin et al. (2006)


Turner, Manolatou, Schmidt, Lipson, Foster, Sharping, and Gaeta, Opt. Express 14, 4357-4362 (2006).Dulkeith, Xia, Schares, Green, and Vlasov, Opt. Express 14, 3853 (2006).

Measurement of Anomalous-GVD In SOIWaveguides


Four-Wave Mixing Amplification

• Frequency conversion with 5-dB gain.Foster, Turner, Sharping, Schmidt, Lipson,Gaeta, Nature 441, 960 (2006)


Extremely Broadband Wavelength Conversion

• Pump wavelength 0.2 nm from zero-GVD point• 750-nm bandwidth

pump

prediction


Broadband Wavelength Conversion

pump

• pump wavelength 1.5 nm from zero-GVDpoint

• 500-nm bandwidthFoster, Turner, Salim, Gaetra, Lipson, Opt Express, 15, 12949 (2007)


Summary

AFOSR- Air Force Office of Sponsored Research, Gernot PomrenkeDarpa, MTO and DSO, NSF-National Science Foundation

-Nonlinearity in silicon waveguides-GHz silicon photonics-Networs on-chip-Poly-silicon for photonics on-chip

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GHz photonics on a Silicon Chip