Computational Analysis of a GST‐Based Long‐Wave Infrared Microring Resonator on a ZnSe Platform as a Photonic Sensor

This work presents the design and numerical simulation of a long‐wave infrared microring resonator sensor employing Ge 2 Sb 2 Te 5 (GST) as the core material, integrated on a ZnSe substrate with air cladding utilizing the finite‐element method in COMSOL Multiphysics. The study evaluates main properties such as effective mode index, power confinement factor, propagation loss, as well as transmission spectra across various modes. The proposed structure demonstrates strong confinement and minimal loss at 8 μm, achieving high Q ‐factors of 7.9 × 10 3 and 7.3 × 10 3 . The limit of detection is found to be 11.59 × 10 3 refractive index unit (RIU) and 52.32 × 10 3 RIU for the output and drop port, respectively. The GST ring resonator is exploited for label‐free gas and biosensing applications, successfully detecting refractive index variations among multiple ambient gases, cancerous and normal cells, as well as viruses and bacteria. The sensor exhibits high sensitivity, a narrow full‐width at half‐maximum, and wavelength tunability in response to subtle refractive index shifts. These findings establish the GST‐ZnSe platform as a promising candidate for compact, high‐performance integrated photonic sensors for biomedical diagnostics and environmental monitoring.