Multiple Photochemical Hole Burning in Organic Glasses and Polymers: Spectroscopy and Storage Aspects

Abstract

A scheme for optical information storage usingphotochemical hole burning (PHB) in amorphous systems is evaluated. Limits imposed by the nature of PHB in polymers and glasses and its dependence on temperature are discussed. It is demonstrated that optical information storage can be multiplexed by a factor of lo' using the frequency dimension and PHB.

Laser Light-Induced Physical Processes In Optical Materials: Persistent Spectral Hole-Burning

“…PERSISTENT SPECTRAL HOLE [4]. PHB (also called photochemical hole-burning although photophysical hole-burning also occurs) has the interesting property of allowing as many as 1000 or more bits of information to be stored dimension beyond x-y spatial dimensions to achieve this dramatic increase in areal storage density.…”

“…If the photoinduced change in the molecule is persistent on time scales of months or years at low temperatures, the spectral holes at various locations within the line can be used to encode binary information, where, for instance, the presence of a hole at a particular frequency within the inhomogeneous line might correspond to a binary "1" and the absence of a hole might correspond to a binary "0". Figure 3 gives an example of a 19 bit hole pattern written in the absorption line of free-base phthalocyanine molecules in a poly(methylmethacrylate) (PMMA) host [4]. Since in one laser spot many groups of molecules are available, 1000 or perhaps 10,000 bits can, in principle, be stored in the frequency domain in the volume illuminated by a focused laser beam, resulting in potential areal storage densities as large as 1011 bits/cm2.…”

Electrical conductivity of poly(N-vinylcarbazole)-based polysodium-2,9,16,23-tetramethylamine tetracyclohexane tetrazaporphyrin composites

“…Several experiments have been carried out intending to dissolve photoreactive molecules in a solid transparent amorphous material in order to get optical information storage by one tautomerization reaction induced by irradiation. Metal-free phthalocyanines can work in this way when they have been grafted or incorporated into proper polymers, i.e., poly(methylmetacrylate) [2,3]. However, this composite works properly only at 4.2 K. Other dye stuff as the 2,3,9,10,16,17,23,24-octacyano metal phthalocyanine has been incorporated into poly(N-vinylcarbazole) (PNV) either homogeneously dissolved or dispersed in order to favour the absorption of light at longer wavelength and the interaction between the donor and acceptor character of the groups that taking part in the system has been exceptional [4].…”

Dynamical Hole-Burning Requirements for Frequency Domain Optical Storage

“…One potentially important application of laser spectroscopy and photochemistry of molecular and ionic defects in solids at low temperatures is the use of persistent spectral hole-burning to form a frequency domain optical storage system [1] [21 [31 [4] [5). PHB (also called photochemical hole-burning although photophysical hole-burning also occurs) has the interesting property of allowing as many as 1000 or more bits of information to be stored in the volume irradiated by a single focused laser beam.…”

“…If the photoinduced change in the molecule is persistent on time scales of months or years at low temperatures, the spectral holes at various locations within the line can be used to encode binary information, where, for instance, the presence of a hole at a particular frequency within the inhomogeneous line might correspond to a binary "1" and the absence of a hole might correspond to a binary :.. W "0". Figure 3 gives an example of a 19 bit hole pattern written in the absorption line of free-base phthalocyanine molecules in a poly(methylmethacrylate) (PMMA) host [4]. Since in one laser spot many groups of molecules are available, 1000 or perhaps 10,000 bits can, in principle, be stored in the frequency domain in the volume illuminated by a focused laser %.…”