A reflection sensor based on the Rayleigh anomaly of metallic grating in terahertz wave band

Abstract

An optical refractive index sensor based on the Rayleigh anomaly of the gold grating is demonstrated in the terahertz (THz) wave band. A pronounced peak due to the Rayleigh anomaly of the gold grating is observed in the reflection spectrum, the center wavelength of which is sensitive to the environmental refractive index on the top of the grating. The wavelength of the Rayleigh anomaly reflection peak and the corresponding sensitivity are solely determined by the period of the gold grating, the larger the period, the longer the resonance wavelength and the higher the sensitivity. Therefore, a higher sensitivity can be achieved in the THz wave band. Both theoretical and experimental investigations show that the shape and intensity of the Rayleigh anomaly reflection peaks are determined by the duty cycle of the grating, for the value of the duty cycle about 0.4, the maximum intensity of the Rayleigh anomaly reflection peak was achieved.