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6.973Semiconductor Optoelectronics

6.973 Semiconductor Optoelectronics

Lecture 1: Course Overview

Rajeev J. Ram

Office: 36-491Telephone: X3-4182Email: [email protected]


•Background: p-n junctions

•Photodetectors

•Modulators

•Optical amplifiers

•Semiconductor lasers

•Heterostructure materials

•DFB and VCSEL resonators

•Modulation

•Systems

Syllabus

Basic concepts

Advancedconcepts


Outline for Lecture 1Outline for Lecture 1

• Applications of Optoelectronic Devices

• Overview of Devices

• Course Administration


Optical Devices Optical Devices

Passive Optical Devices• Waveguides• Optical Disk

Active Optical Devices• LEDS• Semiconductor lasers• Detectors

DVD player


Passive Optical DevicesPassive Optical DevicesWaveguidesWaveguides

Total internal reflection

Corning


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

Waveguides for DVD PlayersWaveguides for DVD PlayersPlastic Optical FiberPlastic Optical Fiber

PMMA (polymethyl methacrylate) core


7.5 miles of track

DVD DisksDVD Disks‘‘NanostructuredNanostructured Material’Material’

120 nm deep pits by injection molding


Active Devices for DVD PlayersActive Devices for DVD Players

Laserstrained QW at 655 nm

Detector


Devices for Optical CommunicationsDevices for Optical Communications


Example of Metro WDM

RxTx A B C D

A - 1 2 3B 1 - 4 5C 2 4 - 6D 3 5 6 -

Interconnect tableLogical mesh

6 transmitter wavelengths required for 4 nodes.

OADM Node configuration

Tx Tx TxRx Rx Rx

amplifiers amplifiers

Node A

Rx TxRx Tx

1,2,3,4,4,5,5,6,6 2,3,4,5,6,6 3,5,6

Rx:1,2,3,4,4,5,5,6,6 Rx:1,1,2,2,3,4,4,5,6

Rx Tx

Rx:1,2,2,3,3,4,5,6,6

Rx Tx

Rx:1,1,2,3,3,4,5,5,6

Node B Node C Node D

1,2,3 1,1,2,3,4,5 1,1,2,2,3,4,4,5,6

MetroCO/POP

CO/POP

CO/POP

CO/POP

CO/POP

CO/POPCO/POP

CO/POP

Access

ADM

ADMADM

ADM

Local Loop

CoreSan Francisco

Seattle

SubmarineNetwork

Boston

Chicago

Metro


Putting It All Together: OADM NodePutting It All Together: OADM Node

R-TpV

Transmit & Receive TranspondersClient IP,ATM,SDH/SONET,PDHTransmit & Receive TranspondersClient IP,ATM,SDH/SONET,PDH

Pre-ampEast

Pre-ampWest

WDM

Power ampWest

Power ampEast

ControlChannel

WDM

WDM

WDM

MUX

Traffic Traffic

... ...DEMUX

R-TpRtpRtp TpTpTp Tp

MUX

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


Background: p-n junctions

Large electric fields•p-i-n photodetector•modulators

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-6

-5.5

-5

-4.5

-4

-3.5

-3

-2.5

-2

Position (um)

E (e

V)

NA = 1017

ND = 1017

Unbiased

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-4.5

-4

-3.5

-3

-2.5

-2

-1.5

Position (um)

E (e

V)Biased

Injection of high carrier density•diode laser•optical amplifier•tunable filters•variable optical attenuator

Absorption

Emission


Photodetectors

P I N


0

0.2

0.4

0.6

0.8

1

1.2

10 100 10003 dB Bandwidth (GHz)

Equi

vale

nt D

evic

e Sl

ope

Effic

ienc

y at

λ =

130

0 nm

(A/W

)

Fujitsu, 1991

BT&D, 1991

UCSB / Colorado State, 1993

UCLA / JPL / Lucent, 1996

AT&T Bell Labs, 1986

NTT, 1991

NTT, 1994

Ortel, 1996 NTT, 1992

UCSD, 1993

UCSB, 1995

Wq λ Ah cTheoretical Maximum = –––– = 1.05 ––

Gray line indicates maximum available at any given frequency

UCSB, 1997


UCSD / Fermionics, 1996

Thomson-CSF, 1997


UCSD, 1992

UCSB, 1995

NTT, 1991

NTT, 1997

PIN (1500 nm)Waveguide (830 nm)Waveguide (1000 nm)Waveguide (1300 nm)Waveguide (1550 nm)MSM/Schottky (600 nm)

PIN – 1300 nmPIN – 1550 nmWaveguide PIN – 800 nmWaveguide PIN – 1300 nmWaveguide PIN – 1550 nmThomson-

CSF, 1996Ortel, 1994

UCSB / Colorado State, 1995

NTT, 1997

Courtesy of Charles Cox, PSI

Photodetectors


Electro-absorption ModulatorsFast Electrically Controlled Shutters

E = 0 E = 0

Stark shift in quantum well


Electro-absorption Modulators

E = 0 E = 0

Stark shift in quantum well

Applied voltage

Electric field at quantum well

Change in energy level (DOS)

Change in e-h overlap (peak abs)

Electrostatics of pn junctions

2nd order perturbation theory

1st order perturbation theory


Background: p-n junctions

Large electric fields•p-i-n photodetector•modulators

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-6

-5.5

-5

-4.5

-4

-3.5

-3

-2.5

-2

Position (um)

E (e

V)

NA = 1017

ND = 1017

Unbiased

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-4.5

-4

-3.5

-3

-2.5

-2

-1.5

Position (um)

E (e

V)Biased

Injection of high carrier density•diode laser•optical amplifier•tunable filters•variable optical attenuator

Absorption

Emission


Optical Amplifiers


Semiconductor Lasers

( ) gzoeIzI =

RII ir = RII ir =Fabry-Perot Resonator


current

radiative non-radiative

QW capture leakage

internal lossmirror loss

fiber coupled

above threshold below threshold

photons

outp

ut p

ower

(mW

)

current (mA)

Semiconductor Lasers

threshold


Heterostructure Materials

undoped 8x1017

P- dopedn-doped8x1017

InP

subs

trat

e

InP

ridge

electrons

holes

Minimum of 3 materials for good optical and electrical confinement

Minimum:Quantum wellQW barrierWaveguide cladding

Typical:Quantum wellQW barrierWaveguide core (SCH)Waveguide claddingElectrical contact layer

optical mode


• 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.

Quantum Confinement in Semiconductor LasersQuantum Confinement in Semiconductor Lasers


The World of Semiconducting MaterialsThe World of Semiconducting Materials

InP

850 nm

980 nm

1300 nm1550 nm

655 nm


InP

850 nm980 nm

1300 nm1550 nm

InGaAsN(Sb)

Heterostructure Materials

1300 & 1550 nm materials platformsInP – InGaAsP (lasers and detectors)GaAs – InGaAsN (lasers and detectors)

- SiGe (detectors)Si – SiGe (detectors)


ACTIVE DEVICESdiode laser

SOAsmodulators

photodetectorsTE cooler

ELECTRONICSMemory

Flip-flops/MUXTransimpedance amps

Bias circuitry

PASSIVE DEVICESAWGsVOAs

DispersionIsolator/Circulator

Silicon


SOAsmodulators


ELECTRONICSMemory


Bias circuitry



GaAs


SOAsmodulators


ELECTRONICSMemory


Bias circuitry



InP

Commercial

LabUndeveloped


Distributed Feedback Laser Resonators

p-InP

top metal

n-InPsubstrate

High spectral purity

Integrated diffraction grating

n1

n1

n2

( ) gzoeIzI =

Distributed Feedback Resonator

grating


Modulation Response


•Background: p-n junctions

•Photodetectors

•Modulators

•Optical amplifiers

•Semiconductor lasers

•Heterostructure materials

•DFB and VCSEL resonators

•Modulation

•Systems

Syllabus

Basic concepts

Advancedconcepts


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

Physics of Optoelectronic DevicesShun Lien Chuang

Diode Lasers and Photonic Integrated CircuitsL. A. Coldren, S. W. Corzine


Term Project

Last time: 60% 9 Homework Sets10% Midterm30% 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

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