Sb 2 Se 3 ‐Integrated Silicon‐on‐Sapphire Photonics for Nonvolatile Spectral Trimming in the Mid‐Infrared

ABSTRACT Post‐fabrication calibration remains a central challenge for integrated mid‐infrared (mid‐IR) sensing systems because device responses are sensitive to fabrication variations and environmental perturbations. Nonvolatile optical phase‐change materials (PCMs) enable set‐and‐hold spectral correction without static holding power, yet integrated PCM platforms operating beyond 3 µm remain largely unexplored. Here, an Sb 2 Se 3 /silicon‐on‐sapphire trimming platform operating near 3.2 µm is demonstrated in three representative sensing‐oriented architectures: Mach–Zehnder interferometers (MZIs), microring resonators (MRRs), and Bragg gratings. Guided by optical and thermal design, this platform enables low‐loss phase and spectral trimming. Ex situ hot‐plate crystallization establishes the amorphous‐to‐crystalline end‐state trimming range, whereas integrated microheaters provide in situ multilevel trimming through progressive electrically driven crystallization. The PCM‐loaded hybrid waveguide used in the MZI and MRR yields a π‐phase‐shift length of 48 µm, while the Bragg device exhibits an 18 nm expansion of the 3 dB stopband bandwidth. To the best of our knowledge, this is the first experimental demonstration beyond 3 µm of a nonvolatile PCM‐integrated trimming platform spanning interferometric, resonant, and Bragg architectures. These results establish a practical route toward zero‐static‐power calibration and nonvolatile spectral correction in integrated mid‐IR photonics.