Exotic Optical Components

Summary

The mundane optical tasks of directing and transforming beams are mostly done with lenses and mirrors, with the occasional polarizer or wave plate thrown in, and this is enough for cameras and microscopes. A diffraction grating is an optical surface with grooves in it, shaped and spaced so as to disperse incident polychromatic light into a sharply defined spectrum. The analogy can be pressed further, because the grating also has analogs of LO phase noise, LO spurs, and spurs due to LO harmonics. The essential function of a grating is to apply a very precise spatial phase modulation to an incoming beam. Ruled gratings have nice triangular grooves, which allow high diffraction efficiency, but since the process of cutting the grooves produces minute hummocks and irregularities in the surface, they also have relatively high scatter. Holographic gratings are frozen interference fringes, made by shining two really, really good quality laser beams on a photoresist‐coated substrate.