Energy transfer channels at the diffraction-anomaly in transparent gratings and applications in sensors

Diffraction anomaly corresponds to an energy re-distribution in the reflected and transmitted light beams and in different diffraction orders of a grating, which leads to sharp modulations on the transmission and reflection spectra. In gratings sitting on a transparent substrate, this portion of the energy is actually transferred to channels separated from the reflected and transmitted beams. These channels are based on multiple degenerated diffraction processes at the same wavelength as the diffraction anomaly. The spectroscopic response of these channels is sensitive to the change in the environmental refractive index and can be utilized in sensor devices.

► Multiple diffraction processes were found degenerate at the Rayleigh anomaly. ► Experimental verification of light trapping in the grating at diffraction anomaly. ► Application of the sensitive response of diffraction anomaly in index sensors. ► The value of the sensor sensitivity is found equal to the grating period.