Ultracompact gas-sensor based on a 2D photonic crystal waveguide incorporating with tapered microcavity

Abstract

In this study, a new ultra compact gas-sensor, based on a 2D photonic crystal waveguide incorporating with tapered microcavity, is designed to detect small refractive index changes. The refractive index (RI) sensor is formed by a point-defect resonant cavity in the sandwiched waveguide on Si slab with triangular lattice. The properties of the sensor are simulated by using the plane wave expansion (PWE) method and the finite-difference time-domain (FDTD) algorithm. The transmission spectra of the sensor with different ambient refractive indices ranging from n = 1.0 to n = 1.01 are calculated. The calculation results show that a change in ambient refractive index of Δn=1×10−4is apparent. The proposed sensor achieves a sensitivity (Δλ/Δn) of 523.2 nm/RIU. It was found that the resonance wavelength is a linear function of the refractive index in under study range. The sensor is appropriate for detecting homogeneous media.