1. Directly Modulated OEIC-WC (1st Generation – Task Area 3)
Jeff Henness, John Hutchinson (Intel), Leif Johansson, Jon Barton, Matt Sysak, Jon Getty, Larry Coldren

2. Overview Objective/Scope Approach Major Accomplishment
Demonstrate a modulated OEIC-WC with monitoring capability
Approach
Photodiode directly connected to SGDBR gain
Major Accomplishment
Designed and fabricated 1st run of 1st gen OEIC-WC
Begun initial testing/characterization
Main Issues/Problems/Limitations
Contacts, parasitics in test setup limit RF performance
Improve monitor design
Improve preamp-SOA design, SGDBR tuning, power output
Extinction ratio and chirp

3. OEIC Approach In-situ signal monitoring provided
No carrier lifetime limitations
Reduce pattern dependence
Increase linearity
Increase bandwidth
No filter to remove input wavelength
Separate optimization of detection and modulation
Net signal gain and programmable 2R regeneration possible
High integration density – no branching waveguides required

4. Direct vs External Modulation
Directly Modulated
Externally Modulated
PostAmp SOA
Front Mirror
Gain
Phase
Back Mirror
Preamplifier SOA
Photodetector
Front Mirror
Gain
Phase
Back Mirror
EAM
Preamplifier SOA
Photodetector

5. Concept for Direct Mod Device Layout1 2 3 5 6 4 PD
SGDBR
PD Bias
Pre Amp SOA
SOA Bias
Laser Bias
Post Amp
Input
Output
50Ω
Signal Monitor

6. SGDBR Direct Modulation
Small signal bandwidth = 8GHz
10dB extinction demonstrated at 5GHz with no mode hops

7. Laser Efficiency Enhancements
Gain-lever
Cascaded Multiple Active Region (MAR)

8. Directly Modulated WC Design
Gain-Lever w/ Meander
Post-Amp SOA
Front Mirror
Gain Section
Phase
Back Mirror
Absorber
Output
Input
(optional)
Input
Pre-Amp SOA
PhotoDetector
Signal
Interconnect
PhotoDetector
Pre-Amp SOA
(for discrete component testing)
500m PreAmp SOA into 50m active photodetector
Metal trace to carry photocurrent (data signal) to drive gain section
Meander line to provide AC block
SGDBR with 300m PostAmp SOA
Gain-lever designs included in mask

9. Gain Lever CW Spectra and PD Response
Gain Lever SGDBR exhibits low current turn-on
PD exhibits linear I-L response
Photocurrent enough to provide significant modulation

10. OEIC-WC CW Conversion Spectra
in = 1540nm, out = 1546nm
Pin of 4dB gives Pout of 17dB – high differential gain

11. Contacts – Error in Fabrication Run
Issue: Large number of open circuit N-metal contacts
Cause: Nitride not removed under metal – processing error
Solution: Oxygen FIB to open area to underlying metal
Effect: High resistivity & capacitance ground contact
P-metal: Ti/Pt/Au
SiN
InP
FIB 8kV Oxygen
opening (80mx80m)
N-metal: Ni/AuGe/Ni/Au
Long term solution: Change mask and process flow

12. Frequency Response 3dB down at >2.5GHz Clean waveform at 2.5GHz 3dB

13. Signal Monitoring Signal via bias-tee to 50Ω scope input
310A/mW monitor signal
-15.6dB conversion fiber-to-fiber

14. Segmented Ridge Laser (Cascaded Multiple Active Region)
N series connected diodes in one laser cavity
Differential efficiency multiplied by N
Signal/noise multiplied by N
Threshold current divided by N
Stages isolated by ion implants
Compatible with SGDBR technology
SI InP substrate NV o I /N H +
, He
Implantation
Initially Funded vs RFLICS

15. CW Results for MAR Facets: uncoated Stage Temp: 20ºC
Stages & Length
CW Diff. Efficiency
CW Thresh. Current
CW Thresh. Voltage
DC Input Impedance
12x50mm
390%
2.8 mA
11.3 V
470 W
6x100mm
218%
4.8 mA
5.8 V
110 W
3x200mm
119%
9.9 mA
3.1 V
48 W
1x600mm
37%
29 mA
1.04 V
5.8 W
Facets: uncoated
Stage Temp: 20ºC
Internal Loss: 12.2 cm-1
Internal Efficiency: 69.4%
Heatsink: soldered to AlN
Initially Funded vs RFLICS

16. Segmented Laser Performance
Linearity improved by segmentation
3-stage SFDR = dB/Hz2/3
Control SFDR = dB/Hz2/3
High speed operation possible
5 GHz small-signal bandwidth
Resonance-limited
Initially Funded vs RFLICS

17. Current Status and Future Directions
Devices to mounted on carrier, RF probing improved
High speed measurements possible
Possibly satisfy Phase I milestones
Second mask spin will address several aspects
Improved monitor/bias connection
Improved SOA/detector design
Improved SGDBR design
Inclusion of multiple-active region embodiment
Investigation of saturable absorbers for improved extinction in digital applications