Holographic data recording method and system

1 . A method for bit-wise holographic data recording, the method comprising:

providing an optically transparent substrate comprising a photochemically active dye; and

irradiating the optically transparent substrate with a holographic interference pattern and a photochromic conversion control illumination, wherein the pattern has a first wavelength λ 1 and an intensity I 1 both sufficient to convert in the presence of the photochromic conversion control beam, within a volume element of the substrate, at least some of the photochemically active dye into a photo-product, and producing within the irradiated volume element concentration variations of the photo-product corresponding to the holographic interference pattern thereby producing an optically readable datum corresponding to the volume element, and wherein the photochromic conversion control illumination has a second wavelength λ 2 and an intensity I 2 to control the photochromic conversion amplitude in the volume element, wherein the second wavelength is not equal to the first wavelength.

2 . The method of claim 1 , wherein the photochromic conversion control illumination illuminates a volume of the optically transparent substrate overlapping at least in part a volume illuminated by the holographic interference pattern.

3 . The method of claim 1 , wherein irradiating the optically transparent substrate with a holographic interference pattern comprises interfering two recording beams at the first wavelength within the volume element.

4 . The method of claim 3 , wherein the photochromic conversion control illumination is a beam at an angle to the recording beams.

5 . The method of claim 1 , wherein the holographic interference pattern and the photochromic conversion control illumination irradiate the optically transparent substrate simultaneously.

6 . The method of claim 1 , wherein the holographic interference pattern and the photochromic conversion control illumination irradiate the optically transparent substrate sequentially.

7 . The method of claim 1 , wherein the first wavelength is selected to be in a range from about 350 nanometers to about 450 nanometers.

8 . The method of claim 1 , wherein the second wavelength is selected to be in a range from about 450 nanometers to about 900 nanometers.

9 . The method of claim 1 , wherein I 2 /I 1 is in a range from about 0.02 to about 4.

10 . The method of claim 1 , wherein the photochromic conversion fluence of the holographic interference pattern is F 1 and the photochromic conversion fluence of the photochromic conversion control illumination is F 2 , wherein the peak intensity of the holographic interference pattern within a recording in the volume element is I 1,0 and wherein α=(F 1 /F 2 )(I 2 /I 1,0 ) is in a range from about 0.1 to 10.

11 . The method of claim 1 , wherein the photo-product comprises a photo-decomposition product, a product of oxidation, a product of reduction, a product of bond breaking, or a molecular rearrangement product.

12 . The method of claim 1 , wherein the photochemically active dye is a photochemically reversible active dye.

13 . The method of claim 1 , wherein the photochemically active dye comprises a dye material comprising vicinal diarylethenes, fulgides and fulgimides, spiropyrans, spirooxazines, naphtopyrans and combinations thereof.

14 . The method of claim 1 , wherein the photochemically active dye is a vicinal diarylethene, wherein the vicinal diarylethene comprises a material comprising of diarylperfluorocyclopentenes, diarylmaleic anhydrides, diarylmaleimides and combinations thereof.

15 . The method of claim 1 , wherein the photochemically active dye is a vicinal diarylethene, wherein the vicinal diarylethene has a structure (I)

wherein “e” is 0 or 1; R 1 is a bond, an oxygen atom, a substituted nitrogen atom, a sulfur atom, a selenium atom, a divalent C 1 -C 20 aliphatic radical, a halogenated divalent C 1 -C 20 aliphatic radical, a divalent C 3 -C 20 cycloaliphatic radical, a halogenated divalent C 1 -C 20 cycloaliphatic radical, or a divalent C 2 -C 30 aromatic radical; Ar 1 and Ar 2 are each independently a C 2 -C 40 aromatic radical, or a C 2 -C 40 heteroaromatic radical; and Z 1 and Z 2 are independently a bond, a hydrogen atom, a monovalent C 1 -C 20 aliphatic radical, divalent C 1 -C 20 aliphatic radical, a monovalent C 3 -C 20 cycloaliphatic radical, a divalent C 3 -C 20 cycloaliphatic radical, a monovalent C 2 -C 30 aromatic radical, or a divalent C 2 -C 30 aromatic radical.

16 . The method of claim 1 , wherein the photochemically active dye is present in an amount from about 0.1 to about 10 weight percent, based on the total weight of the optically transparent substrate.

17 . The method of claim 1 , wherein the optically transparent substrate comprises an optically transparent plastic material.

18 . The method of claim 1 , wherein the optically transparent substrate comprises a thermoplastic polymer, a thermosetting polymer, or a combination of a thermoplastic polymer and a thermosetting polymer.

19 . The method of claim 18 , wherein the thermoplastic polymer comprises a polycarbonate.

20 . A bit-wise pre-recorded holographic data storage medium prepared by a method comprising:

providing an optically transparent substrate comprising a photochemically active dye; and

irradiating the optically transparent substrate with a holographic interference pattern and a photochromic conversion control illumination, wherein the pattern has a first wavelength λ 1 and an intensity I 1 both sufficient to convert in the presence of the photochromic conversion control beam, within a volume element of the substrate, at least some of the photochemically active dye into a photo-product, and producing within the irradiated volume element concentration variations of the photo-product corresponding to the holographic interference pattern thereby producing an optically readable datum corresponding to the volume element, and wherein the photochromic conversion control illumination has a second wavelength λ 2 and an intensity I 2 to control the photochromic conversion amplitude in the volume element, wherein the second wavelength is not equal to the first wavelength,

wherein the data storage medium comprising greater than 4 recorded layers in the thickness of the holographic data storage medium.

21 . The pre-recorded holographic data storage medium of claim 20 , wherein the photochemically active dye is a reversible photochemically active dye.

22 . The pre-recorded holographic data storage medium of claim 21 , wherein the data storage medium has an areal density of individual data bits greater than 0.01 bits of data per square micron.

23 . A holographic data recording system comprising:

a holographic interference pattern generating source, wherein the holographic interference pattern has a peak Intensity I 1,0 and photochromic conversion fluence F 1 within a recording volume element; and

a photochromic conversion control illumination generating source, wherein the photochromic conversion control illumination has an intensity I 2 and photochromic conversion fluence F 2 within the recording volume element;

wherein α=(F 1 /F 2 )(I 2 /I 1,0 ) is in a range from about 0.1 to 10.