Polarimetry of thin metal transmission gratings in the resonance region and its impact on the response of metal-semiconductor-metal photodetectors

The resonance behavior of metal transmission gratings and its impact on the response of metal-semiconductor-metal (MSM) photodetectors have been studied experimentally and theoretically. The metal gratings, with finger spacings in the subwavelength region of the visible light, were fabricated using e-beam lithography and lift-off. Strong resonances have been observed only in the S polarization. As a result, the light transmitted through a grating is primarily S polarized if the grating's finger spacing is less than one-third of the wavelength of the incident light, but P polarized otherwise. Similar phenomenon has been observed in the response of MSM photodetectors since the fingers (electrodes) of an MSM photodetector basically form a grating. Theoretical simulations employing the rigorous modal-expansion theory fairly predict the observed phenomenon.