Sense high refractive index sensitivity with bragg grating and MIM nanocavity

Abstract

The study of optical microcavity sensors in current micro optical electro mechanical systems (MOEMS) devices is an important research direction in this field. This study investigates a new type of nanocavity temperature sensor based on the S-shaped metal-insulator-metal (MIM) and Bragg grating. The analysis of the original sensor model shows that the resonance wavelength of the proposed grating's reflection spectrum shifts to the long-wave direction with the change of refractive index. The value of the high refractive index sensitivity is 1960 nm/RIU, which is obtained near the Bragg resonance wavelength of 1950 nm, and the figure of merit (FOM) is 14.6. The structure is further optimized by adding nanocavity in the middle of the S-shaped MIM Bragg grating. Results show that the refractive index sensitivity is basically unchanged, but the corresponding FOM is 27.7, showing an improvement of 89.7%. The temperature sensor sensitivity is as high as 4.95 nm/°C, and the reflection spectrum resonance wavelength of the proposed grating shifts to the short-wave direction as the temperature changes. High sensitivity can be obtained when the Bragg resonance wavelength is long. Moreover, the Bragg wavelength has a good linear relationship with external physical parameters, such as refractive index and temperature. The findings of this study have certain theoretical and practical values in realizing high-precision, anti-harsh environment, and multi-sensor integrated MOEMS devices.