1. Broadband Lateral Tapered Structures for Improved Bandwidth and Loss Characteristics for All-Optical Wavelength Converters
Xuejin Yan, Joe Summers, Wei Wang, Marcelo Davanco, Wenbin Zhao, Milan Masanovic, Vikrant Lal, and Daniel Blumenthal
Electrical and Computer Engineering University of California at Santa Barbara

2. Summary of Work
Objective: Develop building blocks to extend tuning range and decrease insertion loss of SOA XPM tunable wavelength converter to 30nm tuning range at 1.55m wavelength.
Approach: Monolithically Integrate SOA wavelength converter with Mach-Zehnder structure with tunable laser using based-InP material.
Major accomplishments:
1) Designed new type of broadband splitter/combiner for WC.
2) Active/passive structures have been designed for same structures.
2) Splitter loss was measured to be better than MMI and Y-splitter over a wavelength range of 100nm.
3) Active XGM was demonstrated using this design.
4) A TWC has been designed and basic DC functionality demonstrated.
5) low reflection and low loss coupling techniques have been designed and fabricated: (i) a window design and (ii) a tapered mode converter

3. Outline
Mach-Zehnder SOA wavelength converter with new waveguide structure.
The splitter with lateral tapers
The vertical coupler at the interface of active to passive waveguide
The mode-shape converter with lateral taper and InP windows
XGM results
Tunable wavelength converter(WC with integrated tunable laser).
The structure of the TWC
The initial results
Issues
Future work

4. The picture of WC

5. Splitter and combiner
Waveguide layer
InP Substrate

6. The picture of the splitter

7. Near Field Image of Splitter
Distance between two spots is 250 m

8. Near Field Image of Splitter with InP Window

9. Wavelength sensitivity of the splitter

10. The spectrum of the splitter with integrated SOA

11. Active to passive vertical transformer
Active layer
InP etching stop layer
Waveguide layer
InP Substrate

12. The Vertical Coupler

13. InP window and mode-shape converter
Lateral taper
InP window
InP Substrate