Photonic Integrated WidelyTunable Semiconductor Lasers

1
High-Efficiency Receiverless Optical
Interconnects
Unique features
Objective

• Transmitter Small footprint integrated
  laser-modulator high-k grating 45-degree facet
  for vertical backside microlenses quantum-well
  intermixing(QWI) for multiple-bandgaps
• Receiver Digital receiver architecture
  high-saturation power PDA photodetector design
  crosstalk shielding

Develop novel, high-efficiency, high-power, and
high-speed transmitter and receiver modules to
minimize additional support electronics in
chip-to-chip optical interconnects
Approach
MilestonesPhase I

• Design simulate transmitter and reciever
  modules
• Refine new technologies such as QWI, 45-degree
  facets, microlenses, air-bridge contacts, and
  shielding
• Fabricate test device arrays
• Provide samples to industrial collaborators.
• Re-spin designs to respond to systems needs
  fabricate deliver new modules

• Design and simulate to verify power
• budget and other aspects
  6 mo.
• Demo high-efficiency, high-power
• laser-mod and photodetectors 15 mo.
  
• Demo module arrays and deliver
• samples 18 mo.

2
Criteria/Concepts
Criteria

• Support data rates up to 40 Gbs
• Small footprint and low power dissipation

Concepts

• Avoid additional driver/receiver electronics
• Use integrated in-plane laser-modulator at 980
  nm to get bandwidth and power required at high
  efficiency
• Use high saturation power photodetector to
  directly drive logic (or same Si receiver as used
  for electrical interconnects)

3
Technical Approach Transmitter

• Design simulate short cavity laser,
  high-coupling gratings, and shallow-quantum-well
  modulator sections. Insure power budget is
  satisfied and thermal issues are understood.
• Refine QWI to simultaneously optimize gain,
  grating and EAM sections
• Fabricate test device arrays
• Re-spin designs to respond to systems needs,
  fabricate deliver new modules to industrial
  collaborators.
• In Phase II develop 45-degree facets and,
  microlenses for collimated vertical emission

IPSEL-Mod
Longitudinal cross sections
End-on view
4
Technical Approach Receiver
PDA Bandstructure

• Design simulate partially-depleted absorber
  photodetector for optical interconnect
  applications. Insure digital receiver
  architecture is valid and that power budget is
  satisfied.
• Refine PDA-PD design and secure wafers.
• Fabricate test device arrays
• Re-spin designs to respond to systems needs,
  fabricate deliver new modules to industrial
  collaborators.
• In Phase II further develop crosstalk shields,
  air bridge contacts, and other necessary
  improvements to meet specifications.

Air-bridge contacts
Initial results
5
LASER Simulation

• Threshold current and temperature rise vs. Lg
• Active length 75 µm
• Rear DBR length 40 µm
• Ridge width 2 µm
• Kappa 650 cm-1
• Grating etch depth 480Å

6
Optical Receiver Options
Conventional Receiver Design
Amplifierless Receiver Design
Lower noise Higher speed
PIN Photodiode High saturation power High
speed (High linearity)