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Published on: April 1, 2020
Enhanced optical nonlinearity in amorphous silicon and its application to waveguide devices.
Kazuhiro Ikeda1, Yaoming Shen, Yeshaiahu Fainman
1Department of Electrical and Computer Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0409, USA. kazikeda@ucsd.edu
Optics Express
|June 25, 2009
Summary
Researchers measured enhanced optical nonlinearity in amorphous silicon films. A novel composite waveguide showed significantly higher free-carrier nonlinearity, attributed to localized states.
Area of Science:
- Materials Science
- Optoelectronics
- Nonlinear Optics
Background:
- Free carrier effects significantly influence optical nonlinearity in silicon.
- Amorphous silicon possesses unique electronic properties due to midgap localized states.
- Waveguide structures are crucial for integrated photonic devices.
Purpose of the Study:
- To measure optical nonlinearity in amorphous silicon films.
- To introduce and characterize a novel composite waveguide of amorphous and crystalline silicon.
- To investigate the impact of midgap localized states on free-carrier nonlinearity.
Main Methods:
- Z-scan technique for measuring optical nonlinearity.
- Fabrication of a composite rib waveguide structure.
- Experimental characterization of nonlinear optical properties and carrier lifetime.
Main Results:
- First measurements of optical nonlinearity in amorphous silicon films due to free carrier effects.
- Demonstrated enhanced nonlinearity in amorphous silicon attributed to midgap localized states.
- Fabricated composite waveguide exhibited a sevenfold increase in free-carrier nonlinearity (4 cm/GW) compared to crystalline silicon.
- Shorter free-carrier lifetime (~300 ps) observed in the composite waveguide due to localized states.
Conclusions:
- Amorphous silicon films exhibit enhanced free-carrier optical nonlinearity.
- The novel composite waveguide structure offers significantly improved nonlinear performance.
- Midgap localized states in amorphous silicon play a key role in enhancing nonlinearity and affecting carrier dynamics.
