Photonic Integration Technology

Photonic Integration Technology
Dr. Michael J. Wale
Director Active Products Research, Oclaro
Caswell, Towcester, Northamptonshire, UK
Symposium on Photonic Integration, Eindhoven, 9 November 2011
Agenda
• About Oclaro
• Why photonic integration?
• Photonic integration in the telecommunications network
• Critical technology for photonic integrated circuits
• New models for III-V PIC design and manufacture
• Conclusions
2
Oclaro
#1 or #2 in Core Optical Network
Bookham
Avanex
Merge
April 2009
+ M&A
Mintera
40/100G
Strategic Partner
Xtellus
Optical Switching &
Liquid Crystals
AOM
VOA/MEM
ClariPhy
DSP
#1 Merchant Supplier Laser Diodes & VCSELs for Selected Markets
Oclaro
Tucson
Laser
Diode
Newport
New
Focus
3
Network Transformation
International
Legacy IP
Metro/Regional Ring
Photonic Core
UNIVERSITY
Legacy Switching
International
Metro Ring
Access
Collector
Fibre Access
Metro/Regional
Mesh
Photonic Core:
WDM Light Signals Everywhere (Except Local Access, yet)
Optical Switching at Nodes (Avoid OEO), increased spectral
efficiency, bit rate per carrier, Coherent/ DSP…. 100G…
4
Technology Trends in Metro/Core Network
Core evolution to
full band tunable enabled
reconfigurability
• Reconfigurability valuable where services
change often
• Hitting metro price points a trigger for market growth
• Full band tunable lasers and transponders are
key components
• Small form factor, pluggable designs highly desirable
• Photonic integration
Move to 40Gb/s
& 100Gb/s transport being
accelerated
• Backwards compatibility with 10G infrastructure
• High spectral efficiency and resilience to channel
impairments
• Advanced modulation formats, coherent detection
• Photonic integration
Minimum power
consumption, high
efficiency, low cost
• Photonic integration coupled with new materials
(e.g. AlGaInAs/InP)
Adoption of impairment
mitigation technology
• Synergistic use of high speed ICs running digital
signal processing algorithms
5
Oclaro : Vertical Integration
Full line of transport subsystems for
40 and 100 Gbps
− DPSK, DQPSK, PM-QPSK with
coherent detection
Full line of required optical
components
I
I
I
− Lasers, receivers, modulators
Detectors
p
-
x
O
p
- x
p
- y
Q
p
-
x
90
S
x
S
y
Modulators
Pol
splitters
Laser
Laser
Drivers
Q
Q
p
- y
p
- x
I
Pol
mux
p
-
Q
y
O
p
-
y
90
Underlying chip technologies
− High degree of integration
LiNbO3
Modulator Chip
Tunable Laser
Chip
Coherent
Detector Chip
6
Photonic Integration: Motivation
• Greatly reduced component cost
• Monolithic interconnection of device elements
• Simpler packaging and assembly, standard processes
• High reliability
• Less interfaces
• High functionality
• Many more functional elements per chip, higher creativity in design
• High phase stability, excellent device matching
• Permits interferometric structures
• Robust
• Single chip designs with minimal optical interfaces are ideal for
demanding environments
• Better power efficiency
• Minimize optical power loss at interfaces between device elements
PIC Technologies intrinsically have high value
7
InP Tunable Laser Platform
Oclaro focus on Tunable Integration Platform on InP
• Digital Supermode Distributed Bragg
Reflector (DSDBR) Laser
• High volume production, >300,000 deployed
• Very high yield and extendable platform
• C-band and L-band
• High performance
• > 38nm tuning range
• > 40dB SMSR
• 13 dBm CW fibre output power
DSDBR laser on carrier
• Based on photonic integration technology
• Capability for monolithic integration with
other functions
• e.g. Integrated tunable laser/Mach Zehnder
modulator (ILMZ)
Packaged component with
control electronics (iTLA)
8
DS-DBR laser overview
•
•
•
•
•
SOA to boost o/p power, provide
power control and shuttering
Front chirped grating
– Multiple contacts provide
local reflection enhancement
to select supermodes
MQW gain section
– Generates light inside cavity
Phase section
– Fine wavelength tuning
Rear phase grating
– Generates comb of 7
reflection peaks
Chip-on-tile based solution for angled waveguide output
Ifront
ISOA
p contacts
Igain
Iphase
Irear
p InP
light
output
QW gain regions
Tuning regions
Grating
n InP substrate
AR coating
n contact
AR coating
9
Integrated Tunable Laser-Mach Zehnder Modulator
• Monolithic integration of
tunable laser with MZ
modulator eliminates
inter-chip coupling
optics, reducing size and
manufacturing cost
• Evolution to high temp
operation using Al(Q)
material
• Co-packaged ASIC for
control functions
ILMZ wafer
ILMZ chip on carrier
Full on-wafer testing
ER=11.7dB Unfiltered
Tunable XFP
10
Multifunction Photonic Integrated Circuits (PICs)
• Monolithic Laser + Modulator
chip for Tunable XFP module
• ~1000 chips per wafer
• Batch processed
• 3” InP wafers
• On wafer tested
• Scalable
Oclaro’s photonic integration technology is built on work
done over >20 years, supported in significant measure by
collaborative programmes (EC, DTI/TSB)
11
InP Tunable Device Arrays
• Technology trial of parallel
arrays of InP transmitters
• Same process platform as ILMZ
• Applications for both long and
short reach
• 3” wafer shown has 100 off
100Gbps integrated
transmitters
• 10λ x10Gb/s chip with
output combiner
• 4λ x 28Gb/s chip with
output combiner
• 1λ x 10G ILMZ reference chip
40G InP RZ-DQPSK
modulator to same approx
scale as 3” wafer above
• Scalability to higher channel
counts and aggregate data
rates
12
Grid-Tunable Device Arrays
• Chips presently under evaluation:
• 10 wavelengths x10 Gbit/s NRZ
192.5, 192.55,
192.6, 192.65
THz
• 4 wavelengths x 28 Gbit/s ODB
• Grid-tunable, 50GHz grid
• Same process as ILMZ/TXFP
• MZ modulator, TXFP equivalent
• Laser and modulator on-wafer test
• 10, 20, 40-channel versions considered
feasible
192.7, 192.75,
192.8, 192.85
THz
• Al(Q) materials will allow high
temperature operation, e.g. 60ºC, for
reduced heat dissipation
• Basis for complex, compact, WDM-PON
OLT
Grid tuning (4 channels)
10x10Gb/s chip
13
WDM-PON: Wavelength Division Multiplexed Passive
Optical Network
OLU/ OLT/ head end
ONT/ ONU subscriber end
Controller
Remote Node
Data I/F
Tunable
Tx
Rx
Advantages
• Conceptual simplicity
• Point-to-Point connectivity by
wavelength
• Fibre-lean
• Secure, resilient
• Future-proof
Rx
Data I/F
Controller
Tx
Enablers
• Low cost tunable laser-based
optical network units
• Photonic integration to manage
central office footprint and cost
Tunability and integration are once again critical enabling factors
14
Advanced Modulation Formats for 40G and above
• Advanced modulation formats such as DQPSK provide spectral
efficiency, dispersion tolerance and compatibility with 10G infrastructure
• Photonic integrated circuits required for effective implementation
uk
τ
τ
Ik
uk
π/4
π/2
DFB
vk
MZM
τ
τ
MZM
PRECODER
ENCODER
Qk
−π/4
DECODER
vk
• InP PIC provides 40Gbit/s (D)QPSK encoding
• Several monitoring functions also included on chip
15
3
0
0
-5
-3
-10
-6
-15
-9
-20
-12
-25
-15
-30
0
5
10
15
S11 (dB)
RZ-DQPSK Modulator Chip
EO Response (dB)
43Gb/s RZ-DQPSK in Practice
20
Frequency (GHz)
• Probed chip measurements
demonstrate S11 < 10dB up to
20GHz
– Electro-optic bandwidth > 20GHz
• InP Photonic Integrated Circuit incorporates RZ pulse-carving modulator
as well as 40Gbit/s QPSK encoder
• Owing to the size advantage of InP integrated circuits, the 40Gb/s
tunable transmitter assembly is the same length as 10Gb/s TTA
• Slightly increase in width to accommodate RF interconnects
16
Coherent 2-Pol QPSK: Four Lanes Per Wavelength
• Emerging as industry standard approach for 100Gb/s
– Standardization activity in OIF
• 4 bits per symbol: quadrature phase coding on both polarizations
• Complex Transmit and Receive functions
– Parallel QPSK modulators at Tx with polarization manipulation
– Polarization diversity + parallel optical hybrid + balanced detectors at Rx
– Full-band tunable Local Oscillator laser
• 10G system architecture compatibility
• High integration level required for effective realization
– LiNbO3 transmitter technology presently employed
– Opportunity for highly compact, integrated III-V solutions
17
Integrated Receivers
• InP chip technology for integrated phase-shift-key (PSK) receivers
incorporating common building blocks for receiver PICs
• Oclaro is developing highly integrated 40G & 100G Polarization
Multiplexing (PM)-QPSK Receivers
– Dual Indium Phosphide (InP) 90º optical “hybrid” PIC
– 4x high speed waveguide PIN detectors per PIC
– 2x dual TIA, with commensurate EO bandwidth,
giving 4x differential electrical outputs
Signal
Sx
Pol
Split
Lx
90°
Hybrid
Qx
Rotate
Sy
LO
Beam
split
Ly
Ix
90°
Hybrid
Iy
Qy
18
Photonic Integration in Oclaro
• Photonic integration is central to Oclaro’s business
• Highly flexible active-passive integration scheme based on
selective area epitaxy
– Butt-joins between active and passive sections
• Multiple stages of epitaxy using MOVPE
– 3-6 growth stages typically employed
– High yields
• Fabrication at Caswell, UK
– Major investment in equipment, facilities and R&D
– 3” processing, stepper and e-beam lithography, extensive automation
• Processes conceptually similar to those developed at TU/e
– Basis for ongoing joint research programmes
19
DSDBR Chip Manufacturing Flow
Completed Laser Chip
Plan view of chip
Bar Cleave / Facet coating
3” wafer: ~2500 die
Wafer Thinning
Metal Deposition
Etch& Dep Tools
Photolithography
Cross section of Ridge
Dielectric Deposition & Etch
MOVPE Overgrowth
Photolithography Tracks
Bare Wafer
Gratings fabrication
MOVPE Reactor
MOVPE Growth (2stages)
Purchased bare wafer
20
Phase Grating Rear Reflector
•
Multiple π–phase shifts in first order grating generate the comb
reflection response for the DS-DBR widely tuneable laser.
Written using e-beam lithography
π–phase shifts
Comb reflection response
1
0.9
0.8
Reflectivity
•
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1.5
1.52
1.54
1.56
1.58
1.6
Wavelength (µm)
21
Scaling Photonic Integrated Circuits
Building an integrated design,
simulation and layout
environment...
AWG active
PIC design
with Tu/e
Design
ILMZ for T-XFP
On wafer test
Known Good Die Process and test
Enable100% factory
efficiency
Fab
On-wafer
testing of
ILMZ, TL,
modulators
and PICs
Data Centre
NG Access
Applications
Coherent
Beyond 100G
Industrial, medical,
consumer applications
Process Robustness
Scalability
Cycle time
Process reuse
22
Next Generation Questions for Industry
• InP photonic integration driving footprint and cost reductions
for 10, 40 and 100Gb/s in telecom and applications beyond;
WDM PON potentially a major application area
• Yields and manufacturability of tunable PIC technology now
relatively mature
• The applications and volume requirements are becoming
business driven, not technology limited
• Integration as an enabling and cost reduction technology
works if volumes and revenues scale also – the business
must grow for technology to be sustainable
• Need to increase market size and reduce the cost of entry for new
applications for the industry to flourish
– PICs can be a major enabler for new markets
– Increased return on investment for next-generation wafer fabs
• Volume and market must expand faster than cost reduction to
enable re-investment
23
Generic Foundry Platform Model
• Generic design and manufacturing platforms are based on standard process flows
and structures, as distinct from custom foundry operations, where processes may
also be specified and adapted by the user
• The foundry can
accordingly turn wafers
in high volume on
stable processes,
supporting many
different designs
• We can establish a
separation of function
between specification,
design and fab
• We can develop
dedicated software
tools and a component
library for rapid and
accurate chip design
This model is used to great effect in microelectronics, but until now has never been
applied in photonics
24
Generic PIC Foundry - Potential Impact
• Photonic ICs come within reach for a much wider range
of users and applications
• Design capability and design productivity greatly
increased
– Move from photonic device development to photonic
circuit design
– New skills, new industries in PIC design will emerge
• High manufacturing volumes on standard processes
• Designs that pass design rule checks are automatically
qualified for reliability, so eliminating an expensive and
time-consuming part of product development
• PIC development and manufacturing cost is no longer
the bottle neck
25
Example 1: 8-channel AWG-based laser
 AWG (Arrayed Waveguide Grating):
λc = 1.55 μm, ∆λ = 100 GHz
 Single mode operation
Booster amplifier ↑ optical power
Output power up to 5 dBm
SMSR > 40 dB
Ith < 15 mA (while booster biased
Mask layout and photograph of the laser
with 20 mA)
 SOA: 500 μm long
COBRA
 Size: 2.35 mm × 2.05 mm




K. Ławniczuk et al., “AWG-based
Multi-wavelength Lasers Fabricated in
a Multi-Project Wafer Run”, IP2011,
PI-Poster-19-10
Design: TU/e, Fab: Oclaro
Transmission spectra of 8-λ AWG laser, while
biasing the booster amplifier with 50 mA
26
Example 2: MMI-Reflector based lasers
COBRA
1270μm
420μm
420μm
2,0
A, Lsoa=1270µm
A, Lsoa=420µm
1,5
1,0
0,5
0,0
0 10 20 30 40 50 60 70 80 90 100
Injection Current [mA]
Power from fiber [dBm]
Fiber coupled power [mW]
2,5
0
-10
-20
-30
-40
-50
-60
-70
-80
I=15mA
I=50mA
1546
1548 1550 1552
Wavelength [nm]
1554
J. Zhao, I. Knight, X. Leijtens, M. Smit, M. Wale, P. Williams, E. Kleijn, “Novel
Lasers Using Multimode Interference Reflector”, IP2011, PI-Poster-19-11
Design: TU/e, Fab: Oclaro
27
Conclusions
• Photonic Integration is a vital technology for competitiveness
• Highly demanding in process technology
• Lithography
• Epitaxy
• State of the art tools are essential for world-class research and
production
• Economic breakthrough may well come from adoption of platform-based,
generic foundry models, with corresponding impact for client industries
• In 5 to 10 years we believe the generic foundry model has potential to
become the dominant model, greatly expanding
the photonic IC business
– So it is right to ask the questions now about how
such a model might work!
• Generic, design-rule/library-based approach, based on qualified
integration platforms and supported by powerful design tools
• A collaborative effort to keep Europe ahead!
28
Thank you!
[email protected]