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
Good morning, my name is Xuejin Yan and my topic is

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) low loss and reflection connection of Active/passive structures have been designed for improving the quality of devices.
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 preliminary measurements are being taken.
5) Low reflection and low loss coupling techniques have been designed and fabricated: (i) a window design and (ii) a tapered mode converter
Here is the summary of the work we did

3. Outline
Mach-Zehnder SOA wavelength converter with new waveguide structure.
The splitter with lateral tapers
The vertical coupler at the interface from active to passive waveguide
The mode-shape converter with lateral taper and InP windows
Active XGM results (first stage of wavelength conversion)
Tunable wavelength converter (WC with integrated tunable laser).
The structure of the TWC
Progress for TWC
C Future work
Here is the outline of my talks

4. Splitter and Combiner Waveguide layer InP Substrate
This is the schematic structure of the splitter. The three waveguides are tapered laterally in the coupling region. The lower pictures are the simulation results of BPM.

5. Wavelength Sensitivity of the Splitter
Its advantages are low loss and very low wavelength sensitive. This curve has shown its these characteristics. Longitudinal axis is the output power from one of two arms and transverse axis the light wavelength.

6. Picture of the Splitter
This is the picture of the splitter we made. The length of coupled waveguides is about 120mm.

7. Near Field Image of Splitter
Distance between two spots is 250 m
This is near field image of the splitter

8. The Spectrum of the Splitter with Integrated SOA
These are the spectrum of the splitter with integrated SOA. Green one is from the facet of SOA. Red and black from the two arms of the splitter.

9. Active to Passive Vertical Transformer
Active layer
InP etching stop layer
Waveguide layer
Here is the schematic picture of the vertical coupler at the interface between the active and passive. Its function is reducing the reflection from the interface of active and passive waveguide.
InP substrate

10. The Vertical Coupler
Here is the picture of the vertical taper between active and passive waveguides.

11. InP Window and Mode-Shape Converter
Lateral taper
InP window
It shows the schematic structure of mode-shape converter with lateral taper and InP window. The taper can improve the coupling efficiency from fiber to device and InP window can suppress reflection from the facets of device.
InP substrate

12. The Function of InP Window
This is the calculating results of InP window. It shows the relation of reflection suppression and window length. It also shows the variation of lateral spot size with window length.

13. Near Field Image of Splitter with 50mm InP Window
This is the near field image of the splitter with about 50m InP window
60m

14. Gain Suppression of SOA
It shows the spectrums of SOA with and without input light when two different currents are injected
SOA
Input light
Output light

15. 2.5GHz XGM eye diagram
This is 2.5GHz eye diagram of XGM wavelength converter.
Probing wavelength =1560nm, pumping wavelength =1570nm.

16. 5.0GHz XGM Eye Diagram
This is 5.0GHz eye diagram of the XGM wavelength converter.
Probing wavelength =1560nm, pumping wavelength =1570nm.

17. Progress for TWC
SSG-DBR laser has been integrated into WC to reduce coupling loss
Splitter dimensions have been increased to ease fabrication
The first devices of TWC have been fabricated

18. Wavelength Converter with Integrated SSG-DBR Laser
This is the picture of WC with integrated tunable laser.

19. Future Work Measure and characterize the new TWC devices
Optimize the processing and design of TWC
Provide a high quality TWC device