Compact hybrid waveguide optical switch with low loss and high extinction ratio based on Ge2Sb2Te5

Abstract

High-efficiency and highly integrated optical switches in integrated photonic circuits have long been a pursuit for researchers. Due to the inherent limitations of silicon materials and fabrication processes, commonly used resonant or interferometric optical switches typically require tens to hundreds of micrometers of footprint to achieve desirable modulation efficiency. In response, we propose an optical switch structure filled with phase-change material (PCM) in a narrow slit, with tapered waveguides on curved sides coupling light in and out of the slit, enabling strong light-matter interaction. This structure consists of curved-side tapered coupling waveguides at both ends and a slit filled with GST (Ge₂Sb₂Te₅) in the middle. By applying an external stimulus to induce a phase change in the GST, which exhibits significant differences in optical properties between its crystalline and amorphous states, substantial modulation efficiency can be achieved. Operating in the transverse electric mode within the band of 1500–1600 nm, this structure can achieve an extinction ratio (ER) of 34.08 dB and an insertion loss (IL) of 0.18 dB at 1550 nm, and this design can still achieve an ER over 27.26 dB and an IL less than 0.43 dB within a wavelength range of ± 50 nm, with an overall length of just 10 micrometers. The proposed structure offers high modulation efficiency and a low footprint, while also exhibiting high tolerance to fabrication errors, making it highly promising for future photonic communication systems.