Fabrication of subwavelength gratings on silicon micro lenses for MEMS scanners at optical communication wavelengths

We fabricated an antireflection subwavelength grating (SWG) on a Si micro lens for an optical scanner at optical communication wavelengths. The optical scanner mainly consisted of the micro lens, comb electrodes, and springs, which were formed on a Si layer. A Pyrex glass was used as a substrate and bonded with the Si layer. The optical characteristics of the SWG were calculated using rigorous coupled-wave analysis. The SWG was successfully fabricated on the micro lens with the diameter of 250 μrn and the height of 12 urn. The optical scanner with the micro lens was fabricated with high accuracy. We observed that the micro lens with the SWG had higher transmittance compared with that without the SWG Using the optical scanner without the SWG on the micro lens for only confirming the actuation characteristics, the scanning angle was measured. When the micro lens moved 50 urn at the voltage of 100 V, the scanning angle of 2.53° was achieved, which almost agreed with the calculation value.