1. Wavelength Converter Enhancements Using QWI
Task Area: Integration Platforms
Wavelength Converter Enhancements Using QWI
James Raring, Erik Skogen, Jon Barton, Larry Coldren

2. Overview Accomplishments Main issues Objective Approach
Develop a novel QWI process for the fabrication of CQW wavelength-agile PICs to allow for the monolithic integration of high power SGDBRs with other optimized components
Approach
Impurity-free vacancy-enhanced QWI
Accomplishments
Achieved 3 band edges in single PIC
Monolithically integrated optimized SGDBRs with EAMs
Main issues
OEIC: Improve EAM design for better absorption and bandwidth
AOWC: Optimize SOA design for low saturation power

3. Quantum Well Intermixing Theory
Impurity-free vacancy-enhanced quantum-well-intermixing
Theory
Create vacancies
Thermal process to diffuse vacancies
Vacancies allow atoms to exchange positions
Smears the well/barrier interface, increasing the quantized energy level
λg1
λg2

4. Quantum Well Intermixing Process
Novel QWI process
Ability to achieve multiple band edges with a single implant

5. Offset Vs CQW
- 50% larger confinement factor in CQW → 50% more modal gain

6. Advantages for Wavelength Converters
Low Threshold High Power SGDBR Lasers
50% more modal gain with centered quantum wells
Higher overall efficiency
AOWC
OEIC
Efficient EA Modulator
- Higher Δα/ΔV with shallow MQWs
-Reduced length and higher speed
Low saturation power SOAs
-Enhanced cross-gain modulation

7. Initial SGDBR/EAM Results: PL
Achieved three desired band edges across wafer
Monolithically integrated widely-tunable laser with EAM

8. SGDBR CQW BRS Cross Section
1.7um ridge
7 x 65Å wells
8 x 80Å barriers
Proton Implant
10um mask in gain
4um mask in EAM

9. SGDBR Results Ith = 8.2 mA ηi = 85% Slope Efficiency = 25%mA
αia = /cm
αip = 2.8 1/cm

10. EAM Frequency Response
• Capacitance due to homojunction can be reduced with tighter implant
• Implanted EAM appears to be limited by pad capacitance
- No pad capacitance on wavelength converter design

11. EAM DC Absorption Add quantum wells for increased absorption
Results in ~ 1V/10dB with 200um length in 10 QW

12. Future Work Improve modulator bandwidth for OEIC
Minimize EAM parasitics
Low k dielectric under interconnect for reduced capacitance
Tighter implant profiles for reduced homojunction capacitance
Explore traveling wave designs
EA and Mach-Zehender modulators
Improve EAM efficiency for OEIC
Redesign active region for increased absorption
Develop technology for higher-efficiency AOWC
Design SOAs with low saturation power
Fabricate OEIC wavelength converters using QWI
Fabricate AOWC wavelength converters using QWI