Azo-dye-doped photorefractive polymer composites for holographic testing and image processing

• US 5,744,267 A
• Filed: 09/10/1996
• Issued: 04/28/1998
• Est. Priority Date: 10/12/1994
• Status: Expired due to Fees

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Arizona Board of Regents (University of Arizona)
• Inventors: Meerholz, Klaus, Volodin, Boris L., Hall, Henry K. Jr., Sandalphon, (NFN), Padias, Anne B., Lyon, Scott R., Kippelen, Bernard, Peyghambarian, Nasser N.
• Primary Examiner(s): ANGEBRANNDT, MARTIN J
• Application Number:
  US08/710,084
• Time in Patent Office: 595 Days
• Field of Search: 430/1, 430/2, 430/290, 430/845, 385/4, 385/130-132, 385/122, 385/141, 359/1, 359/3, 359/4, 538/848, 538/845, 538/851
• US Class Current: 430/1
• CPC Class Codes: G03H 1/02 Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 2001/026 Recording materials or recording processes G03H2226/11 takes precedence; corresponding details, see subgroups of G03H2260/00
• CPC Class Codes: G03H 2001/0264 Organic recording material
• CPC Class Codes: G03H 2260/54 Photorefractive reactivity wherein light induces photo-generation, redistribution and trapping of charges then a modification of refractive index, e.g. photorefractive polymer

Abstract

A photorefractive (PR) device comprises of a layer of a novel photorefractive polymer composite sandwiched inbetween two transparent electrodes. The PR polymer composite comprises a photoconducting polymer, a photosensitizer, a novel second-order, non-linear optical chromophore, and a plasticizer in an amount sufficient to provide the PR polymer composite with a glass transition temperature below about 45° C. The PR polymer composite is capable of internally storing image patterns generated by interfering two coherent light beams inside the material. The PR polymer composite shows high diffraction efficiencies (near 100%) and high net two-coupling gain (>200 cm^-1). The writing of information is reversible. Consequently, the device is suitable for read/write holographic storage and real-time image processing applications, and is capable of being poled at essentially room temperature. The light source is an integrated semiconductor laser and the detector is a commercial Si photodiode or a CCD camera.

Claims

1. A photorefractive polymer composite comprising a second-order, non-linear optical dye, a polymeric photoconductor, a photosensitizer, and a photoconductive plasticizer having a molecular weight of less than 1,000 g/mole, said refractive composite having a glass transition temperature, said photoconductive plasticizer acting to plasticize said photorefractive polymer composite beyond any plasticizing effect provided by said second-order, non-linear optical dye, said photoconductive plasticizer acting to lower said glass transition temperature such that said glass transition temperature is at or below about 20°

C. and said photorefractive composite has a diffraction efficiency derived from the p-polarized readout that is greater than about 13% and approaches 100%.

2. The photorefractive polymer composite of claim 1 wherein said second-order, non-linear optical dye comprises a compound having the general formula ##STR4## where A is --H, --NO₂, --CN, --Cl, --C(CN)═

C(CN)₂, --SO₃ R, or --COOCH₃, with the proviso that at least one A is not --H;

D is --OR³ or --NR³₂ ;

R, R¹ and R² are independently --H, C_1-6 alkyl, or C_1-6 alkoxy; and

R³ is C_1-6 alkyl.

3. The photorefractive polymer composite of claim 2 wherein said second order, non-linear optical dye is selected from the group consisting of 2,5-dimethyl-4-p-nitrophenylazoeinisole and 2,5-dimethyl-4-p-nitrophenylazoaniline.

4. The photorefractive polymer composite of claim 1 wherein said polymeric photoconductor has a polymeric backbone selected from the group consisting of vinyl, acrylate, and methacrylate, said backbone containing pendant groups selected from the group consisting of triphenyl amine and carbazoles.

5. The photorefractive polymer composite of claim 1 wherein said polymeric photoconductor is selected from the group consisting of poly(N-vinylcarbazole), poly(3-alkylthiophene)s, and polyphenylenevinylene.

6. The photorefractive polymer composite of claim 1 wherein said photosensitizer is either a charge transfer complex comprising said photoconductor and a strong electron acceptor or a separate photosensitizer molecule.

7. The photorefractive polymer composite of claim 6 wherein said strong electron acceptor is selected from the group consisting of 2,4,7-trinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenylidene malononitrile, and tetracyanoquinodimethane and wherein said separate photosensitizer molecule consists essentially of a fullerene.

8. The photorefractive polymer composite of claim 7 wherein said charge transfer complex consists essentially of poly(N-vinylcarbazole):

2,4,7-trinitro-9-fluorenone.

9. The photorefractive polymer composite of claim 1 wherein said photoconductive plasticizer is selected from the group consisting of carbazole, N-methylcarbazole, N-ethylcarbazole, N-butylcarbazole, N-hexylcarbazole N-phenylcarbazole, o-nitroanisole, m-nitroanisole, p-nitroanisole, and triphenylamine.

10. The photorefractive polymer composite of claim 1 wherein said dye is present in a concentration within a range of about 30 to 60 wt %, and said photosensitizer is present within a range of about 1 wt % or less.

11. A photorefractive polymer composite comprising a second-order, non-linear optical dye selected from the group consisting of 2,5-dimethyl-4-p-nitrophenylazoanisole and 2,5-dimethyl-4-p-nitrophenylazoaniline, a polymeric photoconductor consisting essentially of poly(N-vinylcarbazole), a photosensitizer consisting essentially of a charge transfer complex consisting essentially of said poly(N-vinylcarbazole) and 2,4,7-trinitro-9-fluorenone, and a plasticizer selected from the group consisting of N-ethylcarbazole, N-methylcarbazole, and N-phenylcarbazole, said photorefractive composite having a glass transition temperatures said plasticizer acting to plasticize said photorefractive polymer composite beyond any plasticizing effect provided by said second-order, non-linear optical dye, said plasticizer acting to lower said glass transition temperature to room temperature such that said glass transition temperature is at or below 20°

C. and said photorefractive polymer composite has a diffraction efficiency derived from the 6-polarized readout that is greater than about 13% and approaches 100%.

12. The photorefractive polymer composite of claim 11 wherein said dye has a concentration of about 50 wt %, said poly(N-vinylcarbazole) has a concentration of about 33 wt %, said plasticizer has a concentration of about 16 wt %, and said photosensitizer has a concentration of about 1 wt %.

13. A holographic device comprising a photorefractive polymer composite sandwiched between two transparent electrically conducting electrodes, said photorefractive polymer composite comprising a second-order, non-linear optical dye, a polymeric photoconductor, a photosensitizer, and a photoconductive plasticizer having a molecular weight of less than 1,000 g/mole, said photorefractive composite having a glass transition temperature, said photoconductive plasticizer acting to plasticize said photorefractive polymer composite beyond any plasticizing effect provided by said second-order, non-linear optical dye, said photoconductive plasticizer acting to lower said glass transition temperature such that said glass transition temperature is at or below about 20°

C. and said holographic device has a diffraction efficiency derived from the p-polarized readout that is greater than about 13% and approaches 100%.

14. The holographic device of claim 13 wherein said second-order, non-linear optical dye comprises a compound having the general formula ##STR5## where A is --H, --NO₂, --CN, --Cl, --C(CN)═

C(CN)₂ (tricyanovinyl), --SO₃ R (sulfonato), or --COOCH₃, with the proviso that at least one A is not --H;

D is --OR³ or --NR³₂ ;

R, R¹ and R² are independently --H, Cl_1-6 alkyl, or C_1-6 alkoxy; and

R³ is C_1-6 alkyl.

15. The holographic device of claim 14 wherein said second-order, non-linear optical dye is selected from the group consisting of 2,5dimethyl-4-p-nitrophenylazoanisole and 2,5-dimethyl-4-p-nitrophenylazoaniline.

16. The holographic device of claim 13 wherein said polymeric photoconductor has a polymeric backbone selected from the group consisting of vinyl, acrylate, and methacrylate, said backbone containing pendant groups selected from the group consisting of triphenyl amine and carbazoles.

17. The holographic device of claim 13 wherein said polymeric photoconductor is selected from the group consisting of poly(N-vinylcarbazole), poly(3-alkylthiophene)s, and polyphenylvinylene.

18. The holographic device of claim 13 wherein said photosensitizer is either a charge transfer complex comprising said photoconductor and a strong electron acceptor or a separate photosensitizer molecule.

19. The holographic device of claim 18 wherein said strong electron acceptor is selected from the group consisting of 2,4,7-trinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenylidene malononitrile, and tetracyanoquinodimethane and wherein said separate photosensitizer molecule consists essentially of a fullerene.

20. The holographic device of claim 19 wherein said charge transfer complex consists essentially of poly(N-vinylcarbazole):

2,4,7-trinitro-9-fluorenone.

21. The holographic device of claim 13 wherein said photoconductive plasticizer is selected from the group consisting of carbazole, N-methylcarbazole, N-ethylcarbazole, N-butylcarbazole, N-hexylcarbazole N-phenylcarbazole, o-nitroanisole, m-nitroanisole, p-nitroanisole, and triphenylamine.

22. The holographic device of claim 13 wherein said transparent electrically conducting electrodes consist essentially of indium tin oxide.

23. The holographic device of claim 13 wherein said dye is present in a concentration within a range of about 30 to 60 wt %, and said photosensitizer is present within a range of about 1 wt % or less.

24. A holographic device comprising a photorefractive polymer composite sandwiched between two transparent electrically conducting electrodes, said photorefractive polymer composite comprising a second-order, non-linear optical dye selected from the group consisting of 2,5-dimethyl-4-p-nitrophenylazoanisole and 2,5-dimethyl-4-p-nitrophenylazoaniline, a polymeric photoconductor consisting essentially of poly(N-vinyl-carbazole), a photosensitizer consisting essentially of a charge transfer complex consisting essentially of said poly(N-vinylcarbazole) and 2,4,7-trinitro-9-fluorenone, and a photoconductive plasticizer selected from the group consisting of N-ethylcarbazole, N-methylcarbazole, and N-phenylcarbazole, said transparent electrically conducting electrodes consisting essentially of indium tin oxide, said photorefractive composite having a glass transition temperature, said photoconductive plasticizer acting to plasticize said photorefractive polymer composite beyond any plasticizing effect provided by said second-order, non-linear optical dye, said photoconductive plasticizer acting to lower said glass transition temperature such that said glass transition temperature is at or below 20°

C. and said holographic device has a diffraction efficiency derived from the p-polarized readout that is greater than about 13% and approaches 100%.

25. The holographic device of claim 24 wherein said dye has a concentration of about 50 wt %, said poly(N-vinylcarbazole) has a concentration of about 33 wt %, said plasticizer has a concentration of about 16 wt %, and said photosensitizer has a concentration of about 1 wt %.

26. A method of fabricating erasable holographic recording devices for thick phase holograms comprising:

(a) providing a pair of transparent, electrically conducting electrodes;

(b) spacing said pair of transparent electrically conducting electrodes apart by a plurality of spacers to provide a space volume between said pair of transparent electrically conducting electrodes;

(c) filling said space volume with a photorefractive polymer composite, said photorefractive polymer composite comprising a second-order, non-linear optical dye, a polymeric photoconductive, a photosensitizer, and a photoconductive plasticizer having a molecular weight of less than 1,000 g/mole, said photorefractive composite having a glass transition temperature, said photoconductive plasticizer acting to plasticizer said photorefractive polymer composite beyond any plasticizing effect provided by said second-order, non-linear optical dye, said photoconductive plasticizer acting to lower said glass transition temperature such that said glass transition temperature is at or below about 20°

C. and said erasable holographic recording device has a diffraction efficiency derived from the p-polarized readout that is greater than about 13% and approaches 100%.

27. The method of claim 26 wherein said second-order, non-linear optical dye comprises a compound having the general formula ##STR6## where A is --H, --NO₂, --CN, --Cl, --C(CN)═

C(CN)₂ (tricyanovinyl), --SO₃ R (sulfonato), or --COOCH₃, with the proviso that at least one A is not --H;

D is --OR or --NR ³₂ ;

R, R¹ and R² are independently --H, C_1-6 alkyl, or C_1-6 alkoxy; and

R³ is C_1-6 alkyl.

28. The method of claim 27 wherein said second-order, non-linear optical dye is selected from the group consisting of 2,5-dimethyl-4-p-nitrophenylazoanisole and 2,5-dimethyl-4-p-nitrophenylazoaniline.

29. The method of claim 26 wherein said polymeric photoconductor has a polymeric backbone selected from the group consisting of vinyl, acrylate, and methacrylate, said backbone containing pendant groups selected from the group consisting of triphenyl amine and carbazoles.

30. The method of claim 26 wherein said polymeric photoconductor is selected from the group consisting of poly(N-vinylcarbazole), poly(3-alkylthiophene) and polyphenylenevinylene.

31. The method of claim 26 wherein said photosensitizer is either a charge transfer complex comprising said photoconductor and a strong electron acceptor or a separate photosensitizer molecule.

32. The method of claim 31 wherein said strong electron acceptor is selected from the group consisting of 2,4,7-trinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenylidene malononitrile, and tetracyanoquinodimethane and wherein said separate photosensitizer molecule consists essentially of a fullerene.

33. The method of claim 32 wherein said charge transfer complex consists essentially of poly(N-vinylcarbazole):

2,4,7-trinitro-9-fluorenone.

34. The method of claim 26 wherein said photoconductive plasticizer is selected from the group consisting of carbazole, N-methylcarbazole, N-ethylcarbazole, N-butylcarbazole, N-hexylcarbazole N-phenylcarbazole, o-nitroanisole, m-nitroanisole, p-nitroanisole, and triphenylamine.

35. The method of claim 26 wherein said transparent electrically conducting electrodes consist essentially of indium tin oxide.

36. The method of claim 26 wherein said dye is present in a concentration within a range of about 30 to 60 wt %, and said photosensitizer is present within a range of about 1 wt % or less.

37. A method of fabricating erasable holographic recording devices for thick phase holograms comprising:

(a) providing a pair of transparent, electrically conducting electrodes consisting essentially of indium tin oxide;

(a) providing a pair of transparent, electrically conducting electrodes;

(b) spacing said pair of transparent electrically conducting electrodes apart by a plurality of spacers to provide a space volume between said pair of transparent electrically conducting electrodes;

(c) filling said space volume with a photorefractive polymer composite, said photorefractive polymer composite comprising a second-order, non-linear optical dye selected from the group consisting of 2,5-dimethyl-4-p-nitrophenylazoanisole and 2,5-dimethyl-4-p-nitrophenylazoaniline, a polymeric photoconductor consisting essentially of poly(N-vinyl-carbazole), a photosensitizer consisting essentially of a charge transfer complex consisting essentially of said poly(N-vinylcarbazole) and 2,4,7-trinitro-9-fluorenone, and a photoconductive plasticizer selected from the group consisting of N-ethylcarbazole, N-methylcarbazole, and N-phenylcarbazole, said photorefractive composite having a glass transition temperature, said photoconductive plasticizer acting to plasticize said photorefractive polymer composite beyond any plasticizing effect provided by said second-order, non-linear optical dye, said photoconductive plasticizer acting to lower said glass transition temperature such that said glass transition temperature is at or below 20°

C. and said holographic device has a diffraction efficiency derived from the p-polarized readout that is greater than about 13% and approaches 100%.

38. The method of claim 37 wherein said dye has a concentration of about 50 wt %, said poly(N-vinylcarbazole) has a concentration of about 33 wt %, said photoconductive plasticizer has a concentration of about 16 wt %, and said photosensitizer has a concentration of about 1 wt %.

39. A method of forming a photorefractive polymer composite comprising combining a second-order, non-linear optical dye, a polymeric photoconductor, a photosensitizer, and a photoconductive plasticizer having a molecular weight of less than 1,000 g/mole, said photorefractive composite having a glass transition temperature, said photoconductive plasticizer acting to plasticize said photorefractive polymer composite beyond any plasticizing effect provided by said second-order, non-linear optical dye, said photoconductive plasticizer acting to lower said glass transition temperature such that said glass transition temperature is at or below about 20°

C. and said photorefractive polymer composite has a diffraction efficiency derived from the p-polarized readout that is greater than about 13% and approaches 100%.

40. The method of claim 39 wherein said second-order, non-linear optical dye comprises a compound having the general formula ##STR7## where A is --H, --NO₂, --CN, --Cl, --C(CN)═

C(CN)₂, --SO₃ R, or --COOCH₃, with the proviso that at least one A is not --H;

D is --OR³ or --NR³₂ ;

R, R¹ and R² are independently C_1-6 alkyl, or C_1-6 alkoxy; and

R³ is C_1-6 alkyl.

41. The method of claim 40 wherein said second-order, non-linear optical dye is selected from the group consisting of 2,5-dimethyl-4-p-nitrophenylazoanisole or 2,5-dimethyl-4-p-nitrophenylazoaniline.

42. The method of claim 39 wherein said polymeric photoconductor has a polymeric backbone selected from the group consisting of vinyl, acrylate, and methacrylate, said backbone containing pendant groups selected from the group consisting of triphenyl amine and carbazoles.

43. The method of claim 39 wherein said polymeric photoconductor is selected from the group consisting of poly(N-vinylcarbazole), poly(3-alkylthiophene)s, and polyphenylenevinylene.

44. The method of claim 39 wherein said photosensitizer is either a charge transfer complex comprising said photoconductor and a strong electron acceptor or a separate photosensitizer molecule.

45. The method of claim 44 wherein said strong electron acceptor is selected from the group consisting of 2,4,7-trinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenylidene malononitrile, and tetracyanoquinodimethane and wherein said separate photosensitizer molecule consists essentially of a fullerene.

46. The method of claim 45 wherein said charge transfer complex consists essentially of poly(N-vinylcarbazole):

2,4,7-trinitro-9-fluorenone.

47. The method of claim 39 wherein said photoconductive plasticizer is selected from the group consisting of carbazole, N-methylcarbazole, N-ethylcarbazole, N-butylcarbazole, N-hexylcarbazole, N-phenylcarbazole, o-nitroanisole, m-nitroanisole, p-nitroanisole, and triphenylamine.

48. The method of claim 39 wherein said second-order, non-linear optical dye is present in a concentration within a range of about 30 to 60 wt %, and said photosensitizer is present within a range about 1 wt % or less.

49. A method of forming a photorefractive polymer composite comprising combining a second-order, non-linear optical dye selected from the group consisting of 2,5-dimethyl-4-p-nitrophenylazoanisole and 2,5-dimethyl-4-p-nitrophenylazoaniline, a polymeric photoconductor consisting essentially of poly(N-vinylcarbazole), a photosensitizer consisting essentially of a charge transfer complex consisting essentially of said poly(N-vinylcarbazole) and 2,4,7-trinitro-9-fluorenone, and a plasticizer selected from the group consisting of N-ethylcarbazole, N-methylcarbazole, and N-phenylcarbazole, said photorefractive composite having a glass transition temperature, said plasticizer acting to plasticize said photorefractive polymer composite beyond any plasticizing effect provided by said second-order, non-linear optical dye said plasticizer acting to lower said glass transition temperature to room temperature such that said glass transition temperature is at or below about room temperature and said photorefractive polymer composite has a diffraction efficiency that is greater than about 13% and approaches 100%.

50. The method of claim 49 wherein said second-order, non-linear optical dye has a concentration of about 50 wt %, said poly(N-vinylcarbazole) has a concentration of about 33 wt %, said plasticizer has a concentration of about 16 wt %, and said photosensitizer has a concentration of about 1 wt %.