1 October 1980 Photodichroic Silicate Glass Surface
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Abstract
The photodichroic silicate glass surface is a direct-read-after-write laser recording material which permits instant optical recording without processing of any kind. The required writing energy density at mega Hz rate and higher is 40 mj/cm2. An even better writing sensitivity is expected for a preconditioned glass surface which is yet to be demonstrated at mega Hz rates. The inherent resolution capability of this material is better than 2000 cycles/mm, which is consistent with the fine grain structure of the photodichroic silicate glass surface (grain size <0.02 pm). The photodichroic silicate glass surface can be pre-recorded with tracks of width 1 µm or less. It is potentially a pinhole-free recording material due to the inherent homogeneity of the silicate glasses, and to the very small sizes of the photosensitive crystals, relative to the wavelength of light and the thickness of the photosensitive glass sur-face layer. The physical effect of recording is irreversible; yet the recorded spots or bits are erasable. The erased 1-bit can be distinguished easily from the 0-bit (of course, not distinguishable in the normal read mode), when necessary. There is also a mechanism to prevent erasing after recording and error corrections are completed. The writing is done with a polarized red light, and nondestructive read is done using a near infrared beam, with the recorded bits between crossed polarizers. The erasure is to re-expose with the write beam whose polarization direction has been rotated 45° with respect to the initial polarization exposure direction. In this manuscript, the physical effect of recording is discussed in detail, including the intensity dependent writing sensitivity, the threshold effect, and the relationships among observed spot size, contrast and the writing energy density. Recording in mega Hz rates as well as write-erase cycling are demonstrated.
Che-Kuang Wu, "Photodichroic Silicate Glass Surface," Optical Engineering 19(5), 195769 (1 October 1980). https://doi.org/10.1117/12.7972602 . Submission:
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