Compact dual-parameter sensor design based on a photonic crystal nanobeam cavity with chirped slotted annular holes

A compact photonic crystal nanobeam cavity with a 20 mu m x 0.8 mu m footprint supporting simultaneous air and dielectric resonant modes is proposed for dual-parameter sensing of refractive index and temperature. The struc-ture consists of a row of chirped annular holes and an air-slot etched in an asymmetrical silicon slab. By tapering the lattice period and hole radius, the bands for air and dielectric modes shift in opposite directions, enabling confine-ment in a single cavity. Numerical simulations determine refractive index sensitivities of 173.59 nm/RIU for the air mode and 286.82 nm/RIU for the dielectric mode. Temperature sensitivities are 69.6 pm/degrees C and 78.7 pm/degrees C for the two modes, respectively. The structure demonstrates strong resistance to external interference with refractive index and temperature disturbance resistance coefficients of 2.3 x 10-5 and 0.07. The high sensitivities in an ultra -compact footprint with resistance to crosstalk make this dual-mode nanocavity promising for on-chip biochemical sensing applications. (c) 2023 Optica Publishing Group