Ultra-compact and broadband nonvolatile 2 × 2 optical switch based on a waveguide crossing

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Integrated Optics

Background:

• Emerging silicon-photonic applications require optical switches with small size, low power, and minimal loss.
• Existing optical switches face challenges in meeting the demands of large-scale programmable photonic integrated circuits (PICs).

Purpose of the Study:

• To present a simulation study of a novel 2x2 nonvolatile optical switch.
• To explore the use of phase-change material (PCM) for efficient light routing in silicon photonics.
• To optimize the device geometry for enhanced performance using inverse shape optimization.

Main Methods:

• Simulated a 2x2 nonvolatile optical switch utilizing a waveguide crossing with embedded Sb2S3 PCM.
• Leveraged the distinct refractive indices of Sb2S3 in crystalline (low loss) and amorphous (total internal reflection) states.
• Employed an adjoint-based inverse shape optimization approach and integrated an ITO microheater for device refinement.

Main Results:

• Achieved a compact footprint of ~6.4x9 µm² for the optimized device.
• Demonstrated ultra-broadband performance (1300-1800nm) with worst-case insertion loss of 1.24 dB and crosstalk of -12.5 dB.
• A C-band optimized design showed insertion loss < 0.26 dB and crosstalk > -19.1 dB over a 70 nm bandwidth.

Conclusions:

• The proposed Sb2S3-based nonvolatile optical switch offers a promising solution for compact switching elements.
• The device's low loss, low crosstalk, and broad bandwidth are suitable for programmable PIC platforms.
• Simulation results highlight the potential for efficient light routing in future photonic integrated circuits.