We used two novel approaches to produce sub-wavelength structure (SWS)anti-reflection coatings (ARC) on silicon for the millimeter and sub-millimeter(MSM) wave band: picosecond laser ablation and dicing with beveled saws. Weproduced pyramidal structures with both techniques. The diced sample, machinedon only one side, had pitch and height of 350 $\mu$m and 972 $\mu$m. The twolaser ablated samples had pitch of 180 $\mu$m and heights of 720 $\mu$m and 580$\mu$m; only one of these samples was ablated on both sides. We presentmeasurements of shape and optical performance as well as comparisons to theoptical performance predicted using finite element analysis and rigorouscoupled wave analysis. By extending the measured performance of the one-sideddiced sample to the two-sided case, we demonstrate 25 % band averagedreflectance of less than 5 % over a bandwidth of 97 % centered on 170 GHz.Using the two-sided laser ablation sample, we demonstrate reflectance less than5 % over 83 % bandwidth centered on 346 GHz.
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