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Broadband all-optical modulation in hydrogenated-amorphous silicon waveguides
Karthik Narayanan1, Ali W Elshaari, Stefan F Preble
1Microsystems Engineering, Kate Gleason College of Engineering, Rochester Institute of Technology, Rochester, New York 14623, USA. kxn0404@rit.edu
Optics Express
|July 1, 2010
Summary
Hydrogenated-amorphous silicon (a-Si:H) waveguides enable broadband all-optical modulation with significant signal change in short devices. This material offers a high-performance platform for integrated photonics.
Area of Science:
- Photonics
- Materials Science
- Integrated Optics
Background:
- Low-loss waveguides are crucial for integrated photonics.
- All-optical modulation in silicon is challenging due to weak nonlinear effects.
Purpose of the Study:
- To demonstrate broadband all-optical modulation in hydrogenated-amorphous silicon (a-Si:H) waveguides.
- To investigate the modulation performance and carrier dynamics in a-Si:H compared to crystalline silicon.
Main Methods:
- Fabrication of low-loss a-Si:H waveguides.
- Characterization of all-optical modulation depth and speed.
- Estimation of free-carrier absorption coefficients and recombination rates.
Main Results:
- Achieved significant broadband all-optical modulation (approx. 3 dB) in a 15 micrometer a-Si:H device.
- Observed a larger free-carrier absorption effect in a-Si:H (alpha = 1.63x10^-16 N cm^-1) compared to crystalline silicon.
- Measured a modulation time of approximately 400 ps, indicating dominant surface recombination in a-Si:H waveguides.
Conclusions:
- a-Si:H exhibits enhanced all-optical modulation capabilities due to increased free-carrier absorption.
- Surface recombination significantly influences carrier dynamics in nanoscale a-Si:H waveguides.
- a-Si:H presents a promising material for high-performance, backend-integrated CMOS photonics.
