Sagi Mathai 1 Si WDM Modulator Array for FWH-OCDMA Sagi Mathai, Xin Sun Prof. Tsu-Jae King, Prof....
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Transcript of Sagi Mathai 1 Si WDM Modulator Array for FWH-OCDMA Sagi Mathai, Xin Sun Prof. Tsu-Jae King, Prof....
Sagi Mathai 1
Si WDM Modulator ArraySi WDM Modulator Arrayfor FWH-OCDMAfor FWH-OCDMA
Sagi Mathai, Xin SunProf. Tsu-Jae King, Prof. Ming C. Wu
EECS DepartmentUniversity of California, Berkeley
OCDMA ReviewApril 6th, 2005
Sagi Mathai 2
FWH-OCDMA All Si TransmitterFWH-OCDMA All Si Transmitter
EncodedOutput
Multi-WavelengthSource Input
Drop Ports for Feedback Control
Wavelength Selective Microring Modulator
Array
Sagi Mathai 3
Free-Carrier Plasma EffectFree-Carrier Plasma Effect
Carrier Concentration (cm-3) Carrier Concentration (cm-3)
PNPN 1818 100.6105.8,
8.01822 105.8108.8, PNPNn
Ref: Irace, et.al., Silicon Photonics, Topics in Appl Phys, vol 94, pp 361-392, 2004.
1012 1013 1014 1015 1016 1017 101810-6
10-5
10-4
10-3
10-2
10-1
100
101
102
1012 1013 1014 1015 1016 1017 101810-9
10-8
10-7
10-6
10-5
10-4
10-3
Absorption Coefficient Change Refractive Index Change
(
cm-1)
-n
Electrons
Holes
Electrons
Holes
Sagi Mathai 4
Modulation MechanismModulation Mechanism
• Index of refraction can be tuned by injecting or depleting carriers in the microring optical waveguide
• Shifting the index of refraction will shift the microring resonant frequency and thus its transfer curve
• The resulting modulation in resonant frequency will cause intensity modulation on the optical carrier
si
sd
n0
n=0
OPTICAL FREQUENCYRESPONSE
SCHEMATIC(TOP VIEW)
Modulated Output
st
|st/si|2
0
Sagi Mathai 5
Wavelength Channel DistributionWavelength Channel Distribution
100 GHz
FSR = 500 GHz0 5 10 15 20 25 30
0
200
400
600
800
1000
Radius (µm)
FS
R (
GH
z)
4 WAVELENGTH CHANNELS
FSR = 500 GHz corresponds to R = 24 µm
FREE SPECTRAL RANGE
Sagi Mathai 6
Quality Factor and RC Parasitic LimitsQuality Factor and RC Parasitic Limits
5 10 15 20 25 30200
250
300
350
400
450
500
Radius (µm)
f 3d
B (
GH
z)
103 104 1050
5
10
15
20
25
30
Quality Factor
f 3d
B (
GH
z)
QUALITY FACTORLIMITED BANDWIDTH
RC LIMITEDBANDWIDTH
RL=50 0=1.55 µm
RC Parasitics do not limited the bandwidth
2.5 Gb/s switching speed requires Q = 80,000
10 Gh/s switching speed requires Q = 20,000
Sagi Mathai 7
Transfer Function at ResonanceTransfer Function at Resonance
1013 1014 1015 1016 1017-25
-20
-15
-10
-5
0si
sd
st
i
t
s
slog20
Carrier Density (cm-3)
POWER TRANSMISSION
2 = 0.063 = 0.54 cm-1
Target 10 dB Extinction Ratio
Sagi Mathai 8
Carrier Transport SimulationCarrier Transport Simulation
0.0 0.5 1.0 1.5 2.0 2.5 3.0-7.0x10-6
-6.0x10-6
-5.0x10-6
-4.0x10-6
-3.0x10-6
-2.0x10-6
-1.0x10-6
0.0
tOFF
=0.042nstON
=0.051ns
n
Time (ns)
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.01E10
1E11
1E12
1E13
1E14
1E15
1E16
Ho
le C
on
cen
trat
ion
(cm
-3)
Driving Voltage (V)
SWITCHING DYNAMICS CARRIER CONCENTRATION
Sagi Mathai 9
Previous Results on Passive Si Microdisk Previous Results on Passive Si Microdisk ResonatorsResonators
• Microdisk resonators have been fabricated on Si
• Optical performance characterized
• Optical Q > 100,000 was demonstrated
Sagi Mathai 10
Si Microring Modulator SchematicSi Microring Modulator Schematic
InputPort
DropPort
TransmitPort
AddPort
P-typeRegions
N-typeRegion
SOI
Sagi Mathai 11
Cross SectionCross Section
B
A
C D
TOP VIEW
A-B CROSS SECTION C-D CROSS SECTION
N-typeDoping
C D
BOX
0.45 m
0.45 m
P-typeDoping
A B
0.2 m
0.05 m
BOX
N-typeDoping P-type
Doping
Sagi Mathai 12
BPM Waveguide SimulationsBPM Waveguide Simulations
Width = 0.45 mRib height = 0.2 m
Slab height = 0.05 m
Radius = 24 m
STRAIGHT WAVEGUIDE CURVED WAVEGUIDE
Oxide Oxide
Oxide Oxide
SiSi
Sagi Mathai 13
Mask LayoutMask Layout
Input Port
Drop Port
Transmit Port
Add Port
RF and DC Biasing Pads
MicroringResonator
250 microns
Sagi Mathai 14
(1) Waveguide Dry Etching (2) Hydrogen Anneal (3) P+ Implant
Fabrication ProcessFabrication Process
(4) N+ Implant(5) Recrystallization/DopantActivation Anneal
(6) Ni-Silicide
(7) Passivation/Via (7) Contact Pads/Interconnect
Sagi Mathai 15
Berkeley Microlab CapabilityBerkeley Microlab Capability
• Complete 0.35μm CMOS on 6” wafers
• 0.35μm Deep UV Lithography: ASML 5500/90 Stepper
• Device group demonstrated FIN FET with 60 nm gate length (King, Hu, Bokor)
Sagi Mathai 16
ECTL PC /2 Plate Polarizer
Bias-TDC Voltage
SourceRF
Source
EDFA
Free-SpaceOptical Bench
Oscilloscope
ESA
BERT
IR CameraVOA
ElectricalCharacterization
OSA
DUT
RFAmp
PD
Si-Modulator TestbedSi-Modulator Testbed
Sagi Mathai 17
SummarySummary
• Reviewed preliminary study on an all Si based microring modulator array
• Exploit SOI technology and CMOS compatible fabrication process
• Built testbed for device characterization
• 1st generation device target– 2.5 Gb/s
– Single wavelength channel
– Free spectral range ~ 0.5 THz
• Next generation device– 10 Gb/s
– Q = 20,000
– 4 wavelength channels (100 GHz spacing)
– Low power (~µW)