Photodichroic recording and storage material

Photosensitive characteristics of the optical information storage element using M centers in NaF crystals

Effects of M-center concentration and thickness of the M-center layer on the photosensitive characteristics of optical information storage elements using M centers in NaF crystals are presented. It is shown that writing in the disordering mode and reading with crossed polarizers in white light provide good contrast and gray scale images just like conventional silver halide film.

Real-time recording medium: photodichroic KF:LiF

Laser recording and readout measurements using the photodichroic crystal KF:LiF indicate that the material has potential as an input transducer and an adaptive spatial filter in an optical spectrum analyzer. These crystals are among the most photosensitive recording materials without gain, can be produced in large sizes at relatively low cost, and can be operated close to room temperature using thermoelectric coolers. Experiments using a high precision laser scanner providing 96.6-MHz subnsec pulses at 514 nm show that adequate recording can be accomplished with exposures less than 10 mJ/cm(2). An MTF of 40% at 72 1/mm was measured with uniform readout illumination of the recorded signal, but this is reduced if the signal is recovered by rescanning due to the convolution of the scanning beam profile with the recorded spot profile. The readout is destructive at the recording wavelength but can be read out with a much reduced decay rate by using 488 nm. The linear dynamic range in the Fourier plane was measured to be 40 dB.