Abstract

Holographic recording with photothermoplastic devices has been proposed for more than twenty years.¹ A grating, recorded in this way, can be used as a spatial switch. These devices, made of two thin layers spread on a substrate, are electrically charged in the first step of the recording cycle. In the second step, the photoconductive (PC) layer is illuminated to modulate the electric field across the thermoplastic (TP) upper layer. Finally, this electric-field profile is used to create a surface deformation of the TP by heating it to its softening point. This yields a thin phase grating with an efficiency limited theoretically to 33.9%. (Values from 10 to 20% are easily obtained at 633 nm.) The optimum spatial frequency varies from ~100 to more than 1000 mm⁻¹ depending on thermoplastic thickness. By this method, more than 10⁴ recording cycles can be performed by the same device, depending on the type of TP used and the recording conditions.

© 1988 Optical Society of America