Lecture 1: Course Overview Rajeev J. Ram Office: 36-491 Telephone: X3-4182 Email: rajeev@mit.edu
Syllabus Basic concepts Advanced concepts Background: p-n junctions Photodetectors Modulators Optical amplifiers lasers Heterostructure materials DFB and VCSEL resonators Modulation Systems
Outline for Lecture 1 Applications of Optoelectronic Devices Overview of Devices Course Administration
Optical Devices Passive Optical Devices Waveguides Optical Disk Active Optical Devices LEDS lasers Detectors DVD player
Passive Optical Devices Waveguides Total internal reflection Corning
Waveguides for DVD Players Plastic Optical Fiber Premium Optical (Toslink) cables are used for digital audio connections Features: - Application light wavelength 655 + or - 30 nm - Attenuation less than or equal to 0.25 db per meter - Bend Radius greater than or equal to 17 mm - Connection loss less than or equal to 0.5 db PMMA (polymethyl methacrylate) core
DVD Disks Nanostructured Material 120 nm deep pits by injection molding 7.5 miles of track
Active Devices for DVD Players Detector Laser strained QW at 655 nm
Devices for Optical Communications
Submarine Network Example of Metro WDM Seattle San Francisco Core Boston CO/POP CO/POP CO/POP Metro CO/POP ADM CO/POP ADM Access ADM CO/POP Local Loop ADM Chicago CO/POP CO/POP Metro 1,2,3,4,4,5,5,6,6 2,3,4,5,6,6 3,5,6 1,2,3 1,1,2,3,4,5 1,1,2,2,3,4,4,5,6 Rx Tx Rx Tx Rx Tx Rx Tx Rx:1,2,3,4,4,5,5,6,6 Rx:1,2,2,3,3,4,5,6,6 Rx:1,1,2,3,3,4,5,5,6 Rx:1,1,2,2,3,4,4,5,6 Node A Node B Node C Node D Interconnect table Logical mesh Rx Tx A B C D A - 1 2 3 B 1-4 5 C 2 4-6 D 3 5 6-6 transmitter wavelengths required for 4 nodes. OADM Node configuration amplifiers amplifiers Rx Rx Rx Tx Tx Tx
Putting It All Together: OADM Node Traffic WDM WDM Pre-amp East Power amp East DEMUX Control Channel MUX...... Rtp RtpR-Tp TpTpTp Tp Power amp West WDM Pre-amp West Transmit & Receive Transponders Client IP,ATM,SDH/SONET,PDH WDM Traffic MUX R-TpV Gain block EDFAmplifier Pump lasers Detectors 980/1550 MUX Isolators Gain equalizers Multiplexers AWG ( Prism ) Thermoelectrics Attenuators Transceivers EA modulator +DFB Thermoelectrics Isolators Detectors Laser Driver Receiver Amps
Outline for Lecture 1 Applications of Optoelectronic Devices Overview of Devices Course Administration
Background: p-n junctions Large electric fields p-i-n photodetector modulators Injection of high carrier density diode laser optical amplifier tunable filters variable optical attenuator -2 N A = 10 17-1.5-2.5-2 E (ev) -3-3.5-4 -4.5-5 -5.5 N D = 10 17 Absorption Unbiased E (ev) -2.5-3 -3.5-4 Emission Biased -6 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Position (um) -4.5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Position (um)
Photodetectors P I N
Photodetectors Equivalent Device Slope Efficiency at λ = 1300 nm (A/W) 1.2 1 0.6 0.2 q λ A Theoretical Maximum = = 1.05 h c W Thomson- Ortel, 1994 CSF, 1996 Thomson-CSF, 1997 0.8 AT&T Bell Fujitsu, 1991 Labs, 1986 NTT, 1991 Ortel, 1996 NTT, 1992 UCSD, 1993 AT&T Bell Labs, 1986 NTT, 1991 0.4 UCSD / Fermionics, 1996 UCSD, 1992 NTT, 1994 NTT, 1997 UCSB / Colorado State, 1995 UCSB, 1995 BT&D, 1991 UCSB / Colorado State, 1993 AT&T Bell Labs, 1986 UCLA / JPL / NTT, 1997 UCSB, 1995 UCSB, 1997 Lucent, 1996 0 10 100 1000 3 db Bandwidth (GHz) Gray line indicates maximum available at any given frequency PIN PIN 1300 (1500 nm nm) PIN Waveguide 1550 nm(830 nm) Waveguide (1000 nm) Waveguide PIN (1300 800 nm) nm Waveguide PIN (1550 1300 nm) nm MSM/Schottky (600 nm) Waveguide PIN 1550 nm Courtesy of Charles Cox, PSI
Electro-absorption Modulators Fast Electrically Controlled Shutters E = 0 E = 0 Stark shift in quantum well
Electro-absorption Modulators E = 0 E = 0 Applied voltage Electrostatics of pn junctions Electric field at quantum well Change in energy level (DOS) Change in e-h overlap (peak abs) 2 nd order perturbation theory 1 st order perturbation theory Stark shift in quantum well
Background: p-n junctions Large electric fields p-i-n photodetector modulators Injection of high carrier density diode laser optical amplifier tunable filters variable optical attenuator -2 N A = 10 17-1.5-2.5-2 E (ev) -3-3.5-4 -4.5-5 -5.5 N D = 10 17 Absorption Unbiased E (ev) -2.5-3 -3.5-4 Emission Biased -6 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Position (um) -4.5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Position (um)
Optical Amplifiers
Lasers I r = I i R Fabry-Perot Resonator ( z gz ) I e o I = I r = I i R
current Lasers QW capture leakage above threshold radiative photons mirror loss non-radiative internal loss below threshold fiber coupled output power (mw) threshold current (ma)
Heterostructure Materials Minimum of 3 materials for good optical and electrical confinement Minimum: Quantum well QW barrier Waveguide cladding optical mode Typical: Quantum well QW barrier Waveguide core (SCH) Waveguide cladding Electrical contact layer electrons InP substrate n-doped 8x10 17 undoped 8x10 17 P- doped InP ridge holes
Quantum Confinement in Lasers Advantages More efficient, higher material gain, lower threshold Concentration of carriers near band edge Less thermal dependence, spectral broadening Ledenstov et al. Quantum-dot heterostructure lasers. JSTQE, May 2000.
The World of Semiconducting Materials 655 nm 850 nm 980 nm 1300 nm 1550 nm InP
Heterostructure Materials 850 nm 980 nm 1300 nm 1550 nm InP InGaAsN(Sb) 1300 & 1550 nm materials platforms InP InGaAsP (lasers and detectors) GaAs InGaAsN (lasers and detectors) -SiGe(detectors) Si SiGe (detectors)
Undeveloped Lab Commercial Silicon PASSIVE DEVICES AWGs VOAs Dispersion Isolator/Circulator ACTIVE DEVICES diode laser SOAs modulators photodetectors TE cooler ELECTRONICS Memory Flip-flops/MUX Transimpedance amps Bias circuitry GaAs PASSIVE DEVICES AWGs VOAs Dispersion Isolator/Circulator ACTIVE DEVICES diode laser SOAs modulators photodetectors TE cooler ELECTRONICS Memory Flip-flops/MUX Transimpedance amps Bias circuitry InP PASSIVE DEVICES AWGs VOAs Dispersion Isolator/Circulator ACTIVE DEVICES diode laser SOAs modulators photodetectors TE cooler ELECTRONICS Memory Flip-flops/MUX Transimpedance amps Bias circuitry
Distributed Feedback Laser Resonators High spectral purity top metal p-inp n-inp substrate Integrated diffraction grating Distributed Feedback Resonator ( z gz ) I e o I = n 1 grating n 2 n 1
Modulation Response
Outline for Lecture 1 Applications of Optoelectronic Devices Overview of Devices Course Administration
Syllabus Basic concepts Advanced concepts Background: p-n junctions Photodetectors Modulators Optical amplifiers lasers Heterostructure materials DFB and VCSEL resonators Modulation Systems
Pre-requisites Knowledege Continuity equation for minority carrier transport Drift-diffusion transport in diodes Bloch functions in a crystals Density of states for electrons and holes Fermi s Golden Rule time-dependent perturbation theory Slab waveguide modes
Recommended Reading Diode Lasers and Photonic Integrated Circuits L. A. Coldren, S. W. Corzine Physics of Optoelectronic Devices Shun Lien Chuang
Term Project Last time: 60% 9 Homework Sets 10% Midterm 30% Term project Term project: 2 person teams each present one side of an issue 15% written term paper (instead of HW 10) 15% oral presentation (instead of class in Dec)
Term Project Suggested Topics: Gratings vs. Microrings for Compact Optical Add/Drop InGaAsN vs. Quantum Dots for Telecom on GaAs Waveguide vs. Resonant Cavity for High Speed Detectors In-Silicon vs. On-Silicon Photonics for Optical I/O Organic vs. Inorganic LEDs for Alphanumeric Displays Electro-Optic vs. Electro-Absorption Modulators in InP SOA vs. EDWA for Channelized Amplifiers