Long-wave infrared surface plasmon grating coupler

摘要

We present a simplified analytic formula that may be used to design gratings intended to couple long-wave infrared radiation to surface plasmons. It is based on the theory of Hessel and Oliner (1965). The recipe is semiempirical, in that it requires knowledge of a surface-impedance modulation amplitude, which is found here as a function of the grating groove depth and the wavelength for silver lamellar gratings at CO_(2) laser wavelengths. The optimum groove depth for photon-to-surface-plasmon energy conversion was found by experiment and calculation to be approx10percent-15percent of the wavelength. This value is about twice what has been reported previously in the visible spectral range for sinusoidal grating profiles.