Diffractive optical elements (DOEs), which are relatively new additions to the toolbox of optical engineering, can function as lenses, gratings, prisms, aspherics, and many other types of optical element. Typically formed in a film of only a few microns thickness, a DOE may be fabricated on an arbitrarily-shaped substrate. Flexible functionality, wide range of available optical aperture, light weight, and low manufacturing cost are among the advantages of DOEs. They can be fabricated in a broad range of materials such as aluminum, silicon, silica, and plastics, thus providing flexibility in selecting the base material for specific applications. The effects of temperature change, thermal gradients, shock, and stress in thin film optical devices, however, can cause deformation of the substrate and ultimately alter the behavior of a DOE.
DOEs are wavelength sensitive; for instance, the focal length and aberration characteristics of a diffractive lens can vary substantially if the wavelength of the incident light is changed. DOEs can duplicate most of the functions provided by conventional glass optics provided that the optical system operates over a narrow spectral bandwidth, or the operation of the system requires chromatic dispersion. To date, DOEs have found widespread application in beam-combiners, head-mounted displays, beam-shaping optics, laser collimators, spectral filters, compact spectrometers, diode laser couplers, projection displays, compact disk (CD) and digital versatile disk (DVD) players, laser resonators, computer interconnects, solar concentrators, laser material processing, and wavelength division multiplexers/demultiplexers.