Polarized spectral emittance from periodic micromachined surfaces: IV Undoped silicon: Normal direction in deep lamellar gratings

Experimental results of thermal emittance from deep gratings are presented along with a theoretical discussion. We have found that for a certain grating geometry thermal emission peaks coincide with the cutoff frequencies of slab waveguides. The coincidence was found with s- but not p-polarized emission. This suggests that coupling between grating fins for s-polarized emission is small. It was also found that emission peaks do not correlate directly with the well-known grating equation for these deep gratings.