Analytical study of optical bistability in silicon-waveguide resonators

Area of Science:

• Photonics
• Materials Science
• Nonlinear Optics

Background:

• Optical bistability is crucial for all-optical switching and optical memory.
• Silicon-on-insulator (SOI) waveguides offer a promising platform for integrated photonic devices due to their nonlinear optical properties.

Purpose of the Study:

• To present an accurate yet analytically tractable theoretical model for optical bistability in silicon-waveguide resonators.
• To investigate the role of free carriers and thermo-optic effects in enabling bistability in ultrashort resonators.

Main Methods:

• Derivation of a transcendental equation governing transmitted light intensity in a silicon Fabry-Perot resonator.
• Analysis of free-carrier absorption, free-carrier dispersion, and thermo-optic effects.
• Theoretical exploration of controlling device characteristics via p-n junction biasing.

Main Results:

• The model accurately describes optical bistability in silicon waveguides.
• Free carriers exhibit a dual role: absorption saturates intensity, while dispersion and thermo-optic effects enhance phase shifts.
• Ultrashort resonators (micrometer-scale) can achieve bistability due to significant phase shifts, even without facet coatings.
• Electronically controlled optical switching and nanometer-scale optical memory are theoretically feasible.

Conclusions:

• A novel theoretical framework elucidates optical bistability mechanisms in silicon waveguides.
• Free carriers and thermo-optic effects are key to achieving compact, efficient silicon-based optical switches and memory devices.
• The proposed electronically controlled switching mechanism offers a pathway towards advanced integrated photonic functionalities.