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

Abstract

A compact photonic crystal nanobeam cavity with a 20µm×0.8µm footprint supporting simultaneous air and dielectric resonant modes is proposed for dual-parameter sensing of refractive index and temperature. The structure 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 confinement 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/°C and 78.7 pm/°C for the two modes, respectively. The structure demonstrates strong resistance to external interference with refractive index and temperature disturbance resistance coefficients of 2.3×10−5 and 0.07. The high sensitivities in an ultracompact footprint with resistance to crosstalk make this dual-mode nanocavity promising for on-chip biochemical sensing applications.