An ultracompact refractive index gas-sensor based on photonic crystal microcavity

An ultracompact gas-sensor based on the two-dimensional photonic crystal microcavity is presented. The sensor is formed by a point-defect resonant cavity. The transmission spectrums 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 Delta n =1 x 10(-4) is apparent, the sensitivity of the sensor (Delta lambda/Delta n) is achieved with 433nm/RIU(when lattice constant a = 520nm), where RIU means refractive index unit. The properties of the sensor are analyzed and calculated using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method. Using the fabry-Perot cavity mode, the performances of the refractive index sensor are analyzed theoretically. The sensor is optimized using the photonic crystal waveguide structure and simulated using the FDTD method. As the small sensing area (similar to 10 mu m(2)) of the device would require only similar to 1 fL sample analyte, these ultracompact gas sensors would be widely used in little sample analyte in gas measurement.