Diffraction gratings are highly important and widely used in many optical instruments and systems. In the field of spectroscopy, gratings are the enabling devices for the monochromators and spectrometers used in fields ranging from chemistry and biology to optoelectronics and telecommunications. Within the field of telecommunications, a grating can be used as a passive switching component for wavelength-division-multiplexing (WDM) systems. Within the field of optoelectronics, a grating can be used in conjunction with a laser cavity to create a tunable external-cavity-laser system or to Q-switch a laser. In all of these areas, it is of the utmost importance for the grating ruling to be symmetric and repeatable. These applications also require the grating to rotate to a fixed, known spot. This capability must be repeatable, as the grating will need to rotate to a specific point time and time again. These requirements dictate that the movement of the grating be precisely characterized.
The classical method of the mechanical ruling of gratings begins with Fraunhofer. The basic action in mechanical ruling is to inscribe or burnish a series of grooves upon a highly reflective, flat surface. This method creates gratings of poor optical quality due to difficulties in replicating exactly the groove shape, as well as the difficulty in putting the replicated groove in the correct place. Disparities in either of these variables lead to a loss of optical efficiency. With these restrictions and difficulties, the mechanical ruling of gratings produces a monetarily expensive optical component.
August 31, 2001
Rosfjord, K. M. (2001). Scanning Blazed Gratings: Research Project. United States: University of California, Berkeley.