Coherent Photofabrication

Photofabrication is the manufacture of devices through the action of light on a photosensitive material. In its most usual form an image is projected onto a layer of photoresist which, when developed, acts as a mask for the selective processing of the underlying substrate. In coherent photofabrication the pattern to which the photo-resist is exposed is generated in situ as a pattern of interference fringes, produced by the interaction of coherent beams of light. The device is then an interferogram recorded as a modulation in the surface of the photoresist layer and may either be used as it stands or may require further processing. Items which have successfully been made in this way include spectroscopic diffraction gratings of very high quality, grid polarisers for the near infrared, a novel type of antireflection surface, grating couplers for thin film integrated optics and a selectively absorbing surface which may be useful for the harnessing of solar energy.