Microsoft PowerPoint - CLEO08 tutorial

InP-Based Photonic Integrated Circuits CLEO’08 Tutorial CTuBB1 Larry A. Coldren ECE and Materials Departments University of California, Santa Barbara, CA 93106 coldren@ece.ucsb.edu Acknowledgements: Chris Doerr, Alcatel-Lucent; Chuck Joyner, Infinera; UCSB colleagues Coldren CLEO Tutorial 050608 Outline/Contents • Integration Platforms/Technology • Transmitters • Receivers • Transceivers/Wavelength Converters • Conclusions Coldren CLEO Tutorial 050608 Indium phosphide III-V material Zincblende structure (two intersecting FCC lattices, one for In and one for P) Lattice constant = 5.87 A at 300K Coldren CLEO Tutorial 050608 InGaAsP/InP lattice-matched alloys InGaAsP lattice-matched to InP 1.31 1.55 λg(µm) = 1.24/ Eg(eV) Coldren CLEO Tutorial 050608 Lateral waveguides/couplers Waveguide cross sections InP InGaAsP Deeply-etched Ridge Buried channel Surface ridge Buried rib Higher index contrast MMI coupler WMMI Pin LTUNE WWG Pout LMMI Coldren CLEO Tutorial 050608 Modulators Electro-absorption modulator (EAM) ~ 100 µm Can use quantum-confined Stark effect for large ∆α Data Electro-absorption modulator (EAM) Mach-Zehnder modulator (MZM) lumped ~ 500 µm Can use quantum-confined Stark effect with larger ∆λ Data Traveling-wave linear phase modulator ~4 mm Data RF and optical velocities difficult to match (Can get away with lumped phase modulator up to ~10 GHz) (Also, current injection for < 1 GHz) Coldren CLEO Tutorial 050608 Active-Passive (axial) Integration Desire lossless, reflectionless transitions between sections Vertical Twin-Guide Twin- Coldren CLEO Tutorial 050608 Partially transmissive mirrors • Coupling mirrors between integrated active and passive sections Etched grooves Tunable single frequency Laser-modulator Laser-detector First integrated InP (laser – X) devices L.A. Coldren, B.I. Miller, K. Iga, and J.A. Rentschler, “Monolithic two-section GaInAsP/InP active-optical-resonator devices formed by RIE,” Appl. Phys. Letts., 38 (5) 315-7 (March, 1981). DBR gratings and vertical couplers Tunable single frequency Combined integration technologies Y. Tohmori, Y. Suematsu, Y. Tushima, and S. Arai, “Wavelength tuning of GaInAsP/InP integrated laser with butt-jointed built-in DBR,” Electron. Lett., 19 (17) 656-7 (1983). Coldren CLEO Tutorial 050608 QWI For Multiple-Band Edges/Single Growth • Simple/robust QWI process – Ability to achieve multiple band edges with a single implant E. Skogen et al, “Post-Growth Control of the Quantum-Well Band Edge for the Monolithic Integration of Widely-Tunable Lasers and Electroabsorption Modulators,” IEEE Coldren CLEO Tutorial 050608 J. Sel. Topics Quantum Electron. PIC Transmitters Coldren CLEO Tutorial 050608 Early PIC transmitter: EML EML = electroabsorption-modulated laser DFB laser EAM M. Suzuki, et al., J. Lightwave Technol., LT-5, pp. 1277-1285, 1987. Coldren CLEO Tutorial 050608 Early PIC with wavelength-selectable laser and EAM M. G. Young, et al., Electron. Lett., 31, pp. 1835-1836, 1995. Coldren CLEO Tutorial 050608 Early PIC with widely-tunable laser and EA or MZ-modulator SGDBR+X: (UCSB’91-’08 Agility’99-’05 SG-DBR Laser Rear Mirror -140 -150 -160 SMSR (dB) 55 50 45 JDSU’05 ) SGDBR/SOA (no mod.) ∆ν (MHz) 3 2 1 • Vernier sampled DBRs and phase set wavelength • External SOA controls amplitude MZ Modulator Amplifier Front Mirror Gain Phase RIN (dB/Hz) MQW active regions Sampled gratings 19dBm 16dBm 13dBm 192 FIBER POWER 193 194 195 Channel Frequency (THz) 196 10 Gb/s Optical Duobinary Transmission 0 km 200 km Courtesy of JDSU + UCSB Coldren CLEO Tutorial 050608 L.A. Johansson, L.A. Coldren, P.C. Koh, Y.A. Akulova, and G.A. Fish, "Transmission of 10 Gbps Duobinary Signals Using an Integrated Laser-Mach Zehnder Modulator" Optical Fiber Communication (OFC), paper no. OThC4, San Diego, CA, MARCH, 2008 SGDBR- Mach-Zehnder transmitter stage of wavelength converter Series-push-pull SGDBR-MZ transmitter • • • • Integrated load R and bypass C 30 GHz Bandwidth 40 Gb/s error free operation Low/negative chirp Transmitter DQW Receiver MZ small-signal bandwidth 40 Gb/s eyes Negative chirp result 10 Gb/s Eyes 0 km 25 km 50 km (km) Coldren CLEO Tutorial 050608 A. Tauke-Pedretti, M.N. Sysak, J.S. Barton, L.A. Johansson, J.W.Raring, and L.A. Coldren, “40 Gbps series-push-pull Mach-Zehnder Transmitter on a dual-QW integration platform,” Photon. Tech. Lett., 18 (18) 1922-4 (2006). 40 Gb/s SGDBR/TW-EAM 40 Gb/s NRZ 1533 nm 1543 nm 1559 nm • Integration of traveling-wave EAM designs with SG-DBR laser • Modulation efficiency 15 – 20 dB/V over the tuning range • Open eyes at 40 Gb/s for all wavelengths – 6 – 10 dB extinction with 2.1V M. M. Dummer, J.Klamkin, E. J. Norberg, J. W. Raring, A. Tauke-Pedretti, and L A. Coldren, “ Periodic Loading and Selective Undercut Etching for High-Impedance Traveling-Wave Electroabsorption Modulators”, OFC’08, March, 2008. Coldren CLEO Tutorial 050608 Recent multi-channel transmitter PIC 10 x 10 Gb/s Electrical Input AWG Multiplexer CH1 Optical Output l1... l10 10 x 10 Gb/s DC Electrical Bias and Control CH10 ra EA y M Ar Tu ra y na ble D A FB OP rray M Ar ray Ar VO A R. Nagarajan, et al., Sel. Top. Quant. Electron., 11, pp. 50-65, 2005. Coldren CLEO Tutorial 050608 Slide courtesy of C. Joyner Multi-channel transmitter results 10 Optical Power Monitor Photocurrent (arbitrary units) 2 C hannels 1-10 10 2 3 Normalized Power (dB) -10 -20 -30 -40 -50 -60 -70 -80 1526 DFB Voltage (V) 4 5 6 7 8 9 10 1.5 1 0.5 0 Large-Scale Photonic Integrated C ircuit 10-C hannel D W D M T ransm itter D C (20°C ) 0 50 100 150 200 250 300 -0.5 -1 -1.5 D FB Forw ard C urrent (m A ) 1530 1534 1538 Wavelength (nm) 1542 Normalized Transfer Function (dB) Normalized Electrical Response Normalized Electrical Response (dB) (dB) 3 0 LS-PIC DWDM Transmitter EAM Frequency Response (-3V) 0 -4 -8 -12 -16 -20 0 1 2 Negative Bias (V) 3 4 EAM transfer function -3 -6 -9 Channels 1-10 0 5 10 Frequency (GHz) 15 20 -12 Coldren CLEO Tutorial 050608 Slide courtesy of C. Joyner Traveling-wave MZM DQPSK PIC Sub-MZMs I I π/2 phase shifters 50-Ω termination Modulated signal CW light Q Q 50-Ω termination DC bias Wavelength range: L-band (λPL = 1.47 µm) RF input: Differential EO interaction length: 3 mm (Sub-MZMs), 1.5 mm (π/2-phase shifter) Chip size: 7.5 mm x 1.3 mm Courtesy of N. Kikuchi N. Kikuchi, ECOC, 10.3.1, 2007. Coldren CLEO Tutorial 050608 Uses novel n-p-i-n structure TW-MZM DQPSK Results Driving voltage: 3 Vpp (Vπ ) for each 40 Gbit/s data data Received eye patterns 80 Gbit/s LD λ = 1580 nm data data +/-π/4 (+π/4) MZDI Fiber output power (dBm) -10 -20 -30 -40 -50 -60 -70 -80 189.5 189.6 Balanced receiver 40 Gbit/s (-π/4) (10 ps/div) 189.7 189.8 Frequency (THz) Slide courtesy of N. Kikuchi Coldren CLEO Tutorial 050608 Recent InP DQPSK modulator PIC 1.7 mm Star coupler 37% Ground pad EAM #1 0° 225° EAM pad DC bias pad Au p+ InGaAs 2.2 µm p InP i InP 26% Inlet width ratio chosen to achieve desired splitting ratio BCB 8 QWs n InP 37% EAM #2 +90° Set to 90° bias by design (using extra path length in one arm) Coldren CLEO Tutorial 050608 C. R. Doerr, et al., OFC, PDP33, 2007. DQPSK modulator results -2 Quad #1 Quad #2 10 ps Log (bit error rate) -3 -4 -5 -6 -7 215-1 PRBS -30 Power (dBm) -40 -50 -60 1554.4 1554.6 1554.8 1555 1555.2 -8 79.6 Gb/s (OC-1536) -9 15 20 25 OSNR (dB) Wavelength (nm) Coldren CLEO Tutorial 050608 C. R. Doerr, et al., OFC, PDP33, 2007. Receivers Coldren CLEO Tutorial 050608 Early PIC multi-wavelength receiver 8 × 2 nm J. B. D. Soole, et. al., Electron. Lett., pp. 1289-1290, 1995. Coldren CLEO Tutorial 050608 Recent multi-channel receiver PIC CH1 AWG De-Multiplexer Optical Input l1... l10 10 x 10Gb/s 10 x 10Gb/s Electrical Output PIN Photodiode Array CH10 Slide courtesy of C. Joyner R. Nagarajan, et al., Sel. Top. Quant. Electron., 11, pp. 50-65, 2005. Coldren CLEO Tutorial 050608 Multi-channel receiver results Normalized Photoresponse (dB) 5 -5 -10 -15 -20 -25 -30 -35 1528 1533 1538 1543 Wavelength (nm) 1548 Polarization Dependent Loss (dB) 0 1.0 0.8 0.6 0.4 0.2 0.0 0 1 2 3 4 5 6 7 8 Channel Number 9 10 Slide courtesy of C. Joyner Coldren CLEO Tutorial 050608 Early heterodyne receiver PIC Heterodyne receiver for coherent LO laser T. L. Koch, et al., Electron. Lett., 25, pp. 1621-1622, 1989. Also, H. Takeuchi, et al., IEEE Photon. Tech. Lett., 1, pp. 398-400, 1989. Coldren CLEO Tutorial 050608 Balanced receiver for phase modulated signals with feedback is ~ sin(ϕsignal - ϕLO) Photocurrent 1 Large-signal modulation •Open loop •Closed loop Transmission 0 .5 0 M Z p h ase (r Signal – LO phasea d ) difference 0 π 2π • Signal mixed with local oscillator to demodulate optical phase – Detected differential photocurrent represents signal-LO phase difference – Response of interferometer based demodulator is sinusoidal • With feedback the differential photocurrent is reduced by the loop gain: 1/(1+T) – Hybrid integrated EIC* provides transconductance amplification – Closely track received optical phase to operate within linear regime Coldren CLEO Tutorial 050608 L.A. Johansson, H.F. Chou, A. Ramaswamy, L. A. Coldren, and J.E. Bowers, “Coherent optical receiver for linear optical phase demodulation,” Proc. MTT-S Microwave Sym., Tu3D-01 (June, 2007). Balanced PD implementation Adjacent UTC-PDs electrically isolated with high energy Helium implantation – – Rshn Rshp = 5.28 MΩ/sq = 2.46 MΩ/sq PD 1 Interconnect Plan view SEM of BPD PD 2 PDs connected in series with a monolithic metal interconnect Cross-sectional schematic of series-connected PDs IV curves of PDs Ti/Pt/Au P-metal and interconnects Ni/AuGe/Ni/Au N-metal Helium implantation to substrate for isolation Coldren CLEO Tutorial 050608 UTC-PD design p+ InGaAs Absorber n-InP Collector InGaAsP MQW and Waveguide BPM simulation illustrating absorption profile 2D overlap of mode with absorber: 2.8% 1D mode profile QW 4 µm wide 9 µm wide Absorber Barrier Long absorption profile and wide input reduce front end saturation J. Klamkin, A. Ramaswamy, L. A. Johansson, H-F Chou, M.N. Sysak, J. W. Raring, N. Parthasarathy, S.P. DenBaars, J.E. Bowers, and L. A. Coldren, “High-output-saturation and high-linearity uni-traveling-carrier waveguide photodiodes,” Photonics Tech. Letts. 19 (3) 149-151 (Feb. 2007). Coldren CLEO Tutorial 050608 Saturation characteristics UTC CC-UTC f = 1 GHz f = 1 GHz Isat = 65 mA • • Isat = 63 mA Appears less linear More bias dependent Coldren CLEO Tutorial 050608 J. Klamkin, Y-C Chang, A. Ramaswamy, L. A. Johansson, J.E. Bowers, S.P. DenBaars, and L. A. Coldren, “Output saturation and linearity of waveguide uni-traveling-carrier photodiodes,” J. Quantum Electron,. 44 (4) 354-359 (Apr., 2008). Phase modulator design 15 QW - Γ2D = 20.7 % Push-pull modulation QW Barrier VπDC = 2.1 V•mm • • ∆φ Linear term doubled, even order terms cancelled Third order distortion suppressed with bias optimization ∆φ Linearized output characteristic [∆φ(∆V) – ∆φ(-∆V)] ∆V V0 Coldren CLEO Tutorial 050608 ∆V V V0 V MMI coupler design-surface ridge Surface ridge BPM simulation Integrated pad for current injection tuning WMMI Pin LTUNE WWG Pout LMMI WMMI 8 µm WWG 2.5 µm LTUNE 100-300 µm LMMI 345 µm Coldren CLEO Tutorial 050608 Deep-etched 2x2 MMI coupler Deep ridge Shorter MMI coupler Shorter bends and tapers Deep Etched Ridge Surface Ridge WMMI WWG WMMI WMOD LMM I WWG 1.8 µm LMMI 130 µm WDET 9 µm DR MMI coupler Coldren CLEO Tutorial 050608 DR to SR transition PIC receiver/QWI process flow MQW ERM (as grown) Low loss passive waveguide Offset ternary detector InP n- - InGaAsP WG n+ - InP n++- InGaAs or InGaAsP contact n+ - InP Semi-Insulating InP substrate Coldren CLEO Tutorial 050608 PIC receiver/QWI process flow MQW ERM (as grown) Low loss passive waveguide Offset ternary detector InP n- - InGaAsP WG n+ - InP n++- InGaAs or InGaAsP contact n+ - InP Semi-Insulating InP substrate Coldren CLEO Tutorial 050608 PIC receiver/QWI process flow MQW ERM (as grown) Low loss passive waveguide Offset ternary detector n- - InGaAsP WG n+ - InP n++- InGaAs or InGaAsP contact n+ - InP Semi-Insulating InP substrate Coldren CLEO Tutorial 050608 PIC receiver/QWI process flow MQW ERM (as grown) Low loss passive waveguide Offset ternary detector p+ - InP p++ - InGaAs absorber InP collector n- - InGaAsP WG n+ - InP n++- InGaAs or InGaAsP contact n+ - InP Semi-Insulating InP substrate Coldren CLEO Tutorial 050608 PIC receiver/QWI process flow MQW ERM (as grown) Low loss passive waveguide Offset ternary detector p+ - InP p++ - InGaAs absorber InP collector n- - InGaAsP WG n+ - InP n++- InGaAs or InGaAsP contact n+ - InP Semi-Insulating InP substrate Coldren CLEO Tutorial 050608 PIC receiver/QWI process flow p++ - InGaAs contact p+ - InP p+ - InP p++ - InGaAs absorber InP collector n- - InGaAsP WG n+ - InP n++- InGaAs or InGaAsP contact n+ - InP Semi-Insulating InP substrate Coldren CLEO Tutorial 050608 PIC receiver/QWI process flow p++ - InGaAs contact p+ - InP p+ - InP p++ - InGaAs absorber InP collector n- - InGaAsP WG n+ - InP n++- InGaAs or InGaAsP contact n+ - InP Semi-Insulating InP substrate Coldren CLEO Tutorial 050608 SOA-PIN “all-photonic” receiver for transceiver/wavelength-converter PIC • Semiconductor Optical Amplifiers (SOAs) – High gain • Low input powers - increases conversion efficiency – High saturation power • Prevents pattern dependence • Aids in conversion efficiency • Photodetectors – – High bandwidth Large absorption coefficient • Smaller devices Transceiver PIC A. Tauke-Pedretti, M.M. Dummer, M.N. Sysak, J.S. Barton, J.W. Raring, J. Klamkin, and L.A. Coldren, “Monolithic 40 Gbps Separate Absorption and Modulation Mach-Zehnder Wavelength Converter,” Proc. OFC, paper no. PDP36, Anaheim, CA (March 25-29, 2007) Coldren CLEO Tutorial 050608 Simple offset QW integration platform Use simplest integration platform to do the job Active InGaAs p-contact p-InP 7 – Quantum Wells 1.4 Q InGaAsP WG Passive Offset well Gain for SGDBR and SOA λPL = 1550 nm Semi-insulating substrate Reduces capacitance Isolates absorber and modulator grounds n-InP InGaAs n-contact n-InP Fe doped InP substrate Single blanket regrowth InP cladding InGaAs contact layer Coldren CLEO Tutorial 050608 Offset QW receiver design • Receiver SOA – Offset quantum wells provide gain – Linearly flared waveguide • Quantum-well PIN detector – Reverse biased laser QW provide high absorption coefficient – Wide front end prevents saturation – Tapering reduces capacitance Coldren CLEO Tutorial 050608 SOA gain and linearity • High-gain pre-amps improve conversion efficiency – 23 dB of gain was achieved • High saturation power preserves signal quality / reduces pattern dependence – 16 dBm of unsaturated output power with a 12 µm width – 13 dBm (20mW) 1 V rms (2.8 Vpp) over 50 Ω Coldren CLEO Tutorial 050608 Tranceivers/wavelength converters Coldren CLEO Tutorial 050608 Wavelength converter/SOA-PIN receiver & SGDBR-Mach Zehnder transmitter • • • • • • Photocurrent driven 35 µm QW absorption region in receiver – Tapered for reduced capacitance 300 µm traveling-wave Mach-Zehnder modulation region – Series-push-pull design to maximize bandwidth Data format and rate transparent No optical filter required Integrated termination resistor and bypass Capacitor – No external bias tees used Coldren CLEO Tutorial 050608 Mach-Zehnder Wavelength Converter Current from absorber drives MZM WC Performance • • 40 Gb/s NRZ operation <2.5 power penalty for varying input and output wavelengths DQW Constant input to varying output Varying input to constant output 1529 nm 1545 nm 1561 nm Back to back Coldren CLEO Tutorial 050608 A. Tauke-Pedretti, M.M. Dummer, M.N. Sysak, J.S. Barton, J. Klamkin, J.W. Raring and L.A. Coldren, “Separate Absorption and Modulation Mach-Zender Wavelength Converter,” J. Lightwave Tech., 26, (1), 91-98 (Jan. 2008) QWI+ widely-tunable transceiver/ SOA-PIN & SGDBR-EAM Coldren CLEO Tutorial 050608 J.W. Raring, and L.A. Coldren, “40-Gb/s Widely Tunable Transceivers,” IEEE J. Sel. Topics Quantum Electron., 13, (1), pp. 3-14, (January/February 2007) Transceiver chip architecture • Low confinement SOAs, UTC photodiodes, and QW EAMS integrated with SG-DBR lasers Widely-tunablemodulator 175µM QW EA Psat SOA • High photodiode UTC gain/high SGDBR laser Coldren CLEO Tutorial 050608 Tranceiver 40Gb/s receiver performance • Chip-Coupled Receiver Sensitivity at 40 Gb/s – 250µm/1650µm error-free (1E-9) at -16.8dBm – 400µm/1500µm error-free (1E-9) at -20.3dBm • 40 Gb/s eye diagams – 25Ω effective load – ~-19.8 dBm sensitivity @ 40Gb/s – 500mV amplitude – Integrated with 40Gb/s transmitter Coldren CLEO Tutorial 050608 QWI+ tranceiver 40 Gb/s transmit and receive functionality • Transceiver #1 – Transmitter: 75µm EAM DC = 3.5-4.75V: VPtoP = 2.5 – Receiver: SOA design #1 with 30µm UTC • Transceiver #2 – Transmitter: 175µm EAM DC = 2.5-4.5V: VPtoP = 2.5 – Receiver: SOA design #2 with 40µm UTC Coldren CLEO Tutorial 050608 SOA-PIN & SGDBR-TW/EAM wavelength converter • Data format and rate transparent 5-40Gb/s • No filters required (same λ in and out possible) • On-chip signal monitor • Two-stage SOA pre-amp for high sensitivity, efficiency and linearity • Traveling-wave EAM with on chip loads • Only DC biases applied to chip • 40 nm wavelength tuning range M. Dummer et al. OFC 2008 OThC6 (2008) Coldren CLEO Tutorial 050608 LASOR 40 Gb/s Packet Forwarding Chip – OQW & Butt-joint regrowth • • • • Fast Tunable SGDBR Laser Differential Mach-Zehnder Interferometer SOA Wavelength Converter (‘all-optical’) Preamplifier SOAs Integrated delay Output 1550nm Coldren CLEO Tutorial 050608 V. Lal, M. L. Masanovic, J. A. Summers, G. Fish, and D. J. Blumenthal, "Monolithic Wavelength Converters for High-Speed Packet-Switched Optical Networks," JSTQE, 13, pp. 49-57, 2007. Tunable wavelength converter using AWG-laser + SOA + filter lsig • Fast-tunable 40G wavelength converter – 8-channel multi-frequency laser (MFL) – λ-conversion via nonlinear SOA and delay filter WC WC-SOA MZI lsig & lj lj j = 1..8 MFL SOA InP SOA Array Converted optical eye diagram at 40 Gb/s W C Laser 6.5 mm P. Bernasconi, et al., PDP16, OFC 2005. Coldren CLEO Tutorial 050608 Slide courtesy of P. Bernasconi Alcatel-Lucent—IRIS Project 4.0 mm Conclusions • Multi-functionality InP-based Photonic ICs can now be made with state-of-the-art performance and reductions in power dissipation, size, and perhaps cost in sufficient numbers. • Multi-channel WDM transmitters, receivers, and wavelength converters demonstrated • Many future PICs now on the ‘drawing board’ Coldren CLEO Tutorial 050608