Polarized spectral emittance from periodic micromachined surfaces. I. Doped silicon: The normal direction

The normal, polarized spectral (3 μm≤λ≤14 μm) emittances of highly doped, micromachined, periodic structures on heavily phosphorus-doped (110) silicon ([P]∼5×${10}^{19}$ ${\mathrm{cm}}^{\mathrm{-}3}$) were measured for pattern repeat scales, Λ, of 10, 14, 18, and 22 μm and depths ranging from 0.7 to 45 μm. These structures have dimensions that are comparable to the wavelengths of the measured radiation. The s-polarization vector in these measurements was perpendicular to the grating vector. The data demonstrated that the emittance from the deep structures is dominated by standing (quantized) electromagnetic waves in a direction normal to the surface similar to those in an organ pipe. Wood’s singularities were clearly visible in the p-polarized emission on shallow gratings (depth ≤1.5 μm). It is concluded that these measurements, particularly the s-polarized emission from deep gratings, cannot be explained by calculations of electromagnetic singularities on lamellar gratings.