Fast thermo-optic switching through parity-time symmetry breaking

Area of Science:

• Photonics and Materials Science
• Integrated Optics
• Nonlinear Optics

Background:

• Reconfigurable photonic integrated circuits (PICs) are essential for advanced applications.
• Fast optical switches are critical for on-demand reprogramming of optical functions.
• Silicon nitride (SiN) offers a promising platform for visible-wavelength photonics.

Purpose of the Study:

• To demonstrate a fast thermo-optic switching mechanism on a silicon nitride platform.
• To leverage parity-time symmetry breaking for enhanced switching performance.
• To enable efficient optical switching at visible wavelengths (775 nm).

Main Methods:

• Fabrication of a cladding-free, partially metal-covered waveguide on silicon nitride on insulator.
• Utilizing a thermo-optic effect triggered by a weak thermo-optic coefficient material.
• Investigating parity-time symmetry breaking for optical switching.

Main Results:

• Achieved a 7.1 µs rise time for a π phase shift, demonstrating fast switching.
• Demonstrated minimal optical loss in a metal-covered waveguide, an unusual finding.
• Confirmed reproducible fabrication metrics for the designed device.

Conclusions:

• The developed thermo-optic switch offers a fast and robust solution for PICs.
• The cladding-free, metal-covered waveguide design is effective at visible wavelengths.
• This technology holds potential for large-scale photonic networks and visible-light applications.