CMOS-compatible optical switching concept based on strain-induced refractive-index tuning.

Area of Science:

• Photonics and optical engineering
• Semiconductor device physics
• Materials science for optoelectronics

Background:

• Planar lightwave circuits (PLCs) are crucial for optical communication and signal processing.
• Existing tuning mechanisms for refractive index in PLCs often face limitations in compactness, efficiency, or material compatibility.
• Electrically controlled strain offers a promising avenue for dynamic refractive index modulation.

Purpose of the Study:

• To present and analyze a novel planar lightwave switching mechanism.
• To demonstrate the feasibility of using electrically-driven strain for large refractive index variations.
• To explore the potential for ultra-compact and efficient optical switching devices.

Main Methods:

• Numerical analysis of a Mach-Zehnder Interferometer (MZI) with Germanium (Ge) waveguides.
• Integration of a piezoelectric stressor for dynamic strain control in the MZI arms.
• Modeling of strain-induced modifications to the Ge band structure and refractive index.

Main Results:

• Achieved refractive index variations up to 0.05 through electrically-induced strain.
• Demonstrated potential for ultra-compact devices with low propagation loss (<2 dB insertion loss).
• Obtained high extinction ratios (>30 dB) for optical switching.

Conclusions:

• Electrically-driven strain control is a viable method for realizing high-performance planar lightwave switching.
• The proposed mechanism enables the development of compact photonic devices with excellent optical characteristics.
• Extending waveguide materials to SiGe(Sn) alloys can enable operation across the FIR spectrum.