Electro-optical phase-change 2 × 2 switching using three- and four-waveguide directional couplers.

Area of Science:

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

Background:

• Silicon-on-insulator (SOI) technology is a key platform for integrated photonics.
• Electro-optical (EO) switching is crucial for optical communication networks.
• Phase-change materials offer unique optical properties for active photonic devices.

Purpose of the Study:

• To theoretically model and numerically simulate novel SOI channel-waveguide directional couplers.
• To investigate voltage-driven optical switching using Ge2Sb2Te5 phase-change material islands.
• To evaluate the switching performance and characteristics of these EO devices.

Main Methods:

• Theoretical modeling and numerical simulations at a wavelength of 2100 nm.
• Utilizing a mode-matching method to estimate switching performance under strong coupling.
• Investigating the effect of voltage-driven phase changes in Ge2Sb2Te5 on effective refractive index.

Main Results:

• Predicted low-loss switching for both cross-to-bar and bar-to-cross transitions.
• Demonstrated shorter active lengths (500-1000 μm) compared to free-carrier injection devices.
• Observed trade-offs between crosstalk and loss in three-waveguide versus four-waveguide configurations.

Conclusions:

• The proposed EO directional couplers with phase-change material islands show promise for efficient optical switching.
• The 'self-holding' nature and shorter active lengths are advantageous for device miniaturization and performance.
• Further optimization of waveguide design can balance crosstalk and insertion loss for practical applications.