New Page-Composer for Holographic Data Storage

Abstract

CdS in the form of a single crystal is a material exhibiting a steep band edge at the green argon wavelength of 0.515 microm. The thermal shift of this band edge is used to modulate the transmittance of a matrix addressed page-composer for binary data presentation. Short switching pulses in the range of 20 / 50 V applied to evaporated transparent heating elements produce within 100 microsec a 70 degrees C temperature shift in a thin CdS-crystal, being the key element of the page-composer. Contrast ratios of the transmittance of better than 800 and optical efficiencies of 50% are easily obtained in 10 / 20-microm thick samples. Fast parallel switching of twenty-five elements using time multiplex heating has been demonstrated with a 5x5 CdS-page-composer. A 16x18 matrix is being fabricated, and the implementation of larger arrays accessible in 1 msec appears feasible.

High-density optical data storage

“…We start by excluding a certain type of system, namely, the holographic page-oriented systems. These systems are based on classical holography [49,50] and nowadays use angular multiplexing to store images or bit patterns and to retrieve them from a CCD-type array detector. More recent systems use specific properties of volatile recording materials such as bacteriorhodopsin and rely on polarization holography [51,52].…”