Sub-10-µm TM-selective optical switch using phase-matching control of absorptive Ge₂Sb₂Te₅ states.

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Integrated Optics

Background:

• Optical switches are crucial components in photonic integrated circuits (PICs) and reconfigurable optical networks.
• Existing optical switches often face challenges with size, power consumption, and mode selectivity.
• Phase-change materials (PCMs) offer tunable optical properties for advanced photonic device applications.

Purpose of the Study:

• To propose and demonstrate a novel transverse-magnetic (TM)-selective optical switch.
• To utilize Germanium-Antimony-Tellurium (GST) as the phase-change material for switch operation.
• To achieve a compact, efficient, and polarization-selective optical switching functionality.

Main Methods:

• Design of a bent directional coupler incorporating a GST-embedded silicon waveguide.
• Utilizing the distinct optical properties of amorphous and crystalline GST states to control light propagation.
• Characterization of the device performance, including insertion loss, extinction ratio, and bandwidth at 1545 nm wavelength.

Main Results:

• The proposed TM-selective optical switch exhibits a compact footprint (16µm x 3µm) and short coupling length (6.4 µm).
• Achieved an extinction ratio (ER) of 22.8 dB and insertion loss (IL) of 0.21 dB for the TM mode.
• Demonstrated a bandwidth of 32 nm for ER > 15 dB, with unaffected performance for the transverse-electric (TE) mode.

Conclusions:

• The GST-based TM-selective optical switch offers high performance and polarization selectivity.
• The device is suitable for integration into advanced PICs, enhancing functionality.
• This work contributes to the development of reconfigurable optical transmission networks.