TERAHERTZ-WAVE ANTIREFLECTION COATING ON GE AND GAAS WITH FUSED QUARTZ

In the terahertz-wave region, fabrication of an antireflection (AR) co ating is difficult because it must be as thick as several tens of micr ometers, which is far thicker than that used in the optical region. We discuss a lapping method for fabricating an AR layer with a desired t hickness for terahertz-wave optical devices. To demonstrate this metho d, we glued a thin fused-quartz plate to a surface of an undoped Ge or GaAs wafer and polished it to a thickness of one-quarter wavelength. This reduced the reflectivity of the AR surface to 1/720 of the reflec tion of an uncoated surface, as expected from optical theory. (C) 1998 Optical Society of America.