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Nortel Networks Institute University of Waterloo UNIVERSITYOF OFWATERLOO WATERLOO UNIVERSITY High Performance Semiconductor Optical Amplifiers: Enabling All-optical Circuits Simarjeet Singh Saini Nanophotonics and Integrated Optoelectronics Group University of Waterloo UNIVERSITYOF OFWATERLOO WATERLOO UNIVERSITY Semiconductor Amplifiers and Lasers Power Intensity Fabry-Perot (FP) Laser Diode R ~ 30% R ~ 30% Current Wavelength Semiconductor Optical Amplifier (SOA) Intensity AR Power AR R < 0.1% R < 0.1% Current Wavelength UNIVERSITY OF WATERLOO Outline Introduction SOA performance in DWDM systems Non-Uniform Current Distribution SOA as non-linear elements for Optical Logic Optical Header Recognition and Packet Routing Monolithic Integration Conclusion 4 UNIVERSITY OF WATERLOO Introduction to SOAs • SOA Chip • • Angled Facet Ridge or Buried Waveguide AR Coated (R < 10-5) • Typical Performance Specifications • • • • • Gain: 10-20 dB Saturation Output Power (Psat): 9-12 dBm Noise Figure: 7-9 dB Polarization Dependent Gain (PDG): 1.0 dB Gain flatness: 3 dB 20 Iop=600mA 19 18 17 Gain(dB) 16 MAX@1530nm MIN@1530nm 15 14 13 12 11 10 9 8 -10 -8 -6 -4 -2 0 2 4 6 8 Output Power (dBm) 10 12 14 16 18 UNIVERSITY OF WATERLOO SOA Applications Optical Switches Inline amplification Pre - amplification Optical Logic WDM DEMUX Post – amplification (Booster) Amplifiers in PICs WDM MUX UNIVERSITY OF WATERLOO SOA vs. EDFA EDFA responds to average power operation in linear or saturated regime possible EDFA Ppeak Pave SOA responds to peak power pattern dependent loss if operated in saturation SOA SOA operated in linear regime no pattern dependent loss SOA UNIVERSITY OF WATERLOO 8-Channel DWDM Experiments UNIVERSITY OF WATERLOO 8-Channel Spectrum SOA#1 Output Spectrumvs.Output Power 8 WDM Channels 45 100 GHz 7.5 dBm SOA Output 40 9 dBm SOA Output 11 dBm SOA Output 35 13 dBm SOA Output Output Spectrum (dB) 30 25 20 15 FWM Signals 10 5 0 -5 1550 1552 1554 1556 1558 1560 1562 Wavelength (nm) UNIVERSITY OF WATERLOO 10 Gbps Results UNIVERSITY OF WATERLOO WDM Performance Pattern dependence and multi-channel crosstalk effects are eliminated by operating the SOA in the linear regime Increasing Psat is the key for achieving higher SOA linear output power Gain 3 dB Linear Operation 2-3dB 3 dB Optical Output Pave Ppeak Psat UNIVERSITY OF WATERLOO Different Active Regions Active Region Engineering Gain, Psat Comments Bulk Very Easy High, Low Have low saturation Power compared to the QW’s Most of the commercial SOA’s are Bulk Alternate compressive and tensile strain QW’s Easy High, Low Half the carriers are not used at one time; NF will be High Tensile Strained QW’s δ-strained QW’s Difficult (get the right High but at lower Can be used for S-band; but not for C- and L-band balance) wavelengths (1.5 mm), High Difficult Medium, Medium Easy to grow and reproduce Distortions in carrier wavefunctions lead to reduced gain and saturation power Large transparency current increases NF UNIVERSITY OF WATERLOO δ-Strained Concept GaAs Delta Layers (e = -3.7%) InGaAsP (l = 1.27 mm) Ec 2 6 2 6 2 43 A Ev 52 A 43 A Lattice Matched InGaAs repeated 6X UNIVERSITY OF WATERLOO SOA Results: PI SOA Performance vs Current 26 24 22 Gain 20 18 dB 16 14 12 Psat 10 8 Gain Max @ 1530 6 Gain Max @ 1550 4 Psat Min @ 1550 Psat Min @ 1530 2 Noise Figure 0 200 300 400 500 Iop (mA) 600 700 800 UNIVERSITY OF WATERLOO SOA Results: Polarization Sensitive 19 Gain (dB) I @ 500 mA @ 1540 nm 0 TEC : 25 C 16 13 10 8 12 16 20 24 Output Power (dBm) UNIVERSITY OF WATERLOO • Non-uniform Current Distribution for Improved Device Performance UNIVERSITY OF WATERLOO Concept UNIVERSITY OF WATERLOO Approach Using vias in contact layer and changing the longitudinal density, can change local resistance in the device. Arbitrary current distributions can be achieved No change in processing steps P-Metal Contact vias Dielectric Isolation Ridge UNIVERSITY OF WATERLOO Resistance Measurements 2 mm long FP lasers were used to measure change of resistance with contact via spacing Ridge width was 3.2 mm Contact via spacing was uniformly varied from 4 mm to 50 mm for different devices Contact via diameter was 2.7 mm UNIVERSITY OF WATERLOO Effect on Saturation Power 40.00 Standard 4-20 um spacing 4-50 um spacing Psat = 15.5 dBm Gain (dB) 35.00 Psat = 17.8 dBm 30.00 Psat = 19.0 dBm 25.00 Psat increases by 3.5 dB The linearity of the curve also improves 20.00 0.00 5.00 10.00 15.00 20.00 25.00 Output Power (dBm) UNIVERSITY OF WATERLOO Multi-contact Topology UNIVERSITY OF WATERLOO 16 16 14 14 1.6 dB 12 12 10 10 8 1.0 dB8 6 6 Psat with Via Contact NF with Via Contact Psat with Std. Contact NF with Std. Contact 4 2 Noise Figure (dB) Saturation Power (dBm) Performance Improvements 4 2 0 0 0 2 4 6 8 10 12 Package Number UNIVERSITY OF WATERLOO Noise Figure Improvement 22 20 Top= 25 C Iop = 500 mA 16 14 12 10 min g @ 1530 max g @ 1530 min g @ 1550 max g @ 1550 8 10 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 9 Output Power [dBm] 8 Noise Figure (dB) Gain [dB] 18 7 6 5 4 3 2 1 0 0 100 200 300 400 500 600 700 Current (mA) UNIVERSITY OF WATERLOO • SOAs as Non-linear Elements UNIVERSITY OF WATERLOO Non-linear Effects in SOA Cross Gain Modulation Cross Phase Modulation Four Wave Mixing Wavelength Conversion 2R/3R Regeneration Optical Logic: AND, NAND Optical Switching UNIVERSITY OF WATERLOO Packet Routing Output Slot 8 Address Decision is made at each stage by taking the autocorrelation of header with a properly delayed copy of itself and thresholding the result 1 x 2 Space Switches 000É 01 Slot 1 clock bit 100É 01 010... 01 Input 110É 01 001... 01 101É 01 011É 01 111É 01 UNIVERSITY OF WATERLOO Address Recognition Optical Delay Optical AND Gates Electronic Trigger Circuit . Toward 1 x 2 Space Switch Reading the first header bit Address Bits Control Bits Copy of header Copy of header delayed by 4 bits UNIVERSITY OF WATERLOO Sagnac Gate for Optical AND SOA UNIVERSITY OF WATERLOO Input Bits 32 bits Input to the gate 1000xxx00É 0001000xxx00ÉÉ . Control bits Header bits to be detected Delay aligned to the 5th bit Gate was tested for all 8 combinations of address bits Correlated output should be 1 only when the 5th bit is 1 UNIVERSITY OF WATERLOO Logic Outputs Intensity (mW) 5th bit correlated output Input 1000100 3.00 2.00 1.00 0.00 0 0.2 0.4 0.6 0.8 1 0.8 1 Tim e (ns ) Input 1000011 Intensity (mW) 3.00 2.00 1.00 0.00 0 0.2 0.4 0.6 T im e (n s ) UNIVERSITY OF WATERLOO Control Electronics From Optical AND gate THORLAB D400FC Modulator InGaAs Detector MINICIRCUITS ZFBT-4R2GW Pulse Research lab PRL-470B Pulse Research lab PRL-434A Wideband Bias Tee 0.1~4200MHz Line-Driver Fanout Buffer ECL BNC 6040 Pulse Generator MINICIRCUITS ZFL-500LN Amplifier MINICIRCUITS SBLP-300 Low-Pass Filter DC~180MHz UNIVERSITY OF WATERLOO Output from InGaAs Detector UNIVERSITY OF WATERLOO Integration and SOA driver 7V 0V 10ns UNIVERSITY OF WATERLOO Eye diagrams for Cascaded SOAs UNIVERSITY OF WATERLOO Packet Transmission All SOA’s turned on One out of 3 SOA’s off UNIVERSITY OF WATERLOO • TM PARC : A Platform for Monolithic Integration of Photonics Devices UNIVERSITY OF WATERLOO Approach Amplifier Passive Splitter Integrated Mach-Zehnder UNIVERSITY OF WATERLOO Resonantly Coupled Tapers Top View of Active and Passive Waveguides Mode Transform Section Passive Section Gain Section Off-resonance region Mode excited due to sharp taper st 1 order Suprermode Phase Matching region 2nd order Suprermode Transverse view of Active and Passive Waveguides UNIVERSITY OF WATERLOO Basic PARC Platform Mode ormation f Trans on Secti ve i s s a P on i t c e S tion c e S Gain 2.5 mm 1.5 mm 0.3 mm 600 mm 50 mm 2.0 mm 50 mm UNIVERSITY OF WATERLOO Experimental Results 1.0 30 mm 40 mm 80 mm 100 mm 60 mm simulated lateral farfield experimental lateral simulated farfield experimental data transverse Light Intensity (AU) Output Power (mA) 10 5 0 0 50 Current (mA) 100 0.5 0 -90 -60 -30 0 30 60 90 Angle (in degrees) UNIVERSITY OF WATERLOO 3-dB Lossless Splitters Input Waveguide S-bend Waveguides Mode Transformation Mode Expansion Mode Expansion Gain Section Passive Section Coupling Gain Section Sectio UNIVERSITY OF WATERLOO 3-dB Lossless Splitters 20 30 Internal Gain (dB) Signal Gain (dB) Amplifier 1 Amplifier 2 20 15 10 10 5 0 0 100 Current (mA) 200 0 1490 1500 1510 1520 1530 1540 1550 1560 1570 Wavelength (nm) UNIVERSITY OF WATERLOO 2x2 Crosspoint Switches UNIVERSITY OF WATERLOO 2x2 Crosspoint Switch 0 Modulation (in dB) Bar Cross -10 -20 Wavelenghth = 1570 nm -30 -40 0 1 2 3 Voltage (V) UNIVERSITY OF WATERLOO Conclusion SOA performance continues to improve Higher saturation power extends linear operating range Minimal non-linear distortion/crosstalk for ave. output power < Psat – 6 dB SOA saturation power of 16 dBm with NF less than 6 dB demonstrated SOA can allow for all-optical logic Further Integration of SOA with photonic devices should allow for highly functional modules Future: Low cost application FTTH Coarse and D-WDM Ultra-fast optical signal processing and Integration UNIVERSITY OF WATERLOO