A Slow-Light Mach-Zehnder Interferometric Switch With One-Dimensional Grating Waveguides

Optical switches are essential components of all-optical switching networks, enabling optical path switching in the optical domain without the need for electronic conversion. However, the design of optical switches with low-power and ultra-compact footprints remains a significant challenge. In this work, a slow-light thermo-optic (TO) Mach-Zehnder interferometer (MZI) switch based on one-dimensional (1D) grating waveguides is proposed. The proposed structure, with a compact footprint of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$72~\mu $ </tex-math></inline-formula>m, exhibited both strong and weak slow-light regions. In the strong-slow-light region, the structure achieved a high group index (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{g}$ </tex-math></inline-formula>) at a wavelength of 1539.8 nm, with a power consumption of 3.9 mW. Different from conventional designs that rely solely on strong-slow-light effects near the bandgap edge, our approach utilizes the weak-slow-light region centered around 1550 nm. This enables a broader operational bandwidth (~109.5 nm) while maintaining a low switching power of 8.73 mW. The integrated structure presented in this work is promising for building ultra-compact and broadband photonic networks.