Abstract A new class of optical, switching and memory devices is based on the different refractive indices associated with each of the two states of the reversible photochemical interconversion between dimer and monomer states in a broad class of organic materials. Reversibility is expedited by use of a rigid medium. The active material may be a solution or suspension of the photosensitive species in a transparent matrix or may be a single-crystal form of the photosensitive material itself. The particular chemical systems upon which operation is based are so chosen as to result in a relatively large spacing between absorption peaks associated with each of the two states. This class, in which change of state results in a significant change in the resonant character of the material, is further characterized by strong absorption bands (resulting in reasonably complete reaction), by ready reversibility, by thermal stability in either state at usual ambient temperatures, and by refractive index changes within the visible spectrum which are of sufficient magnitude for holographic and other switching or memory use.
Element of claim 1 in which said variations are local and are produced by interference of at least two light beams of one of said different wavelengths.
Claim 2
Dependent Claim
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Element of claim 2 in which said two beams are coherent and unmodulated.
Claim 3
Dependent Claim
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Element of claim 3 in which at least one of the said beams is modulated.
Claim 4
Dependent Claim
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Element of claim 4 in which said modulation is produced during reflection.
Claim 5
Dependent Claim
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Element of claim 4 in which said modulation is produced during transmission.
Claim 6
Dependent Claim
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Element of claim 1 in which said local variation corresponds to digital information.
Claim 7
Dependent Claim
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Element of claim 1 in which the said local variation corresponds to analog information.
Claim 8
Dependent Claim
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Element of claim 8 in which the said local variation is an interference pattern.
Claim 9
Dependent Claim
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Element of claim 1 in which the medium is a photodimer of an anthracene derivative.
Claim 10
Dependent Claim
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Element of claim 10 in which the said anthracene derivative is acridizinium.
Claim 11
Dependent Claim
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Element of claim 1 in which the said photodimer is contained in a matrix.
Claim 12
Dependent Claim
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Element of claim 12 in which the said matrix consists essentially of a copolymer of acrylic acid and methyl methacrylate.
Claim 13
Dependent Claim
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Element of claim 1 in which the said switchable medium consists essentially of a single crystal.