Abstract

Near-resonant optical pumping is applied for encoding the anisotropy of third-order susceptibility χ(3) in a Disperse Red 1 poly (methyl methacrylate) polymer thin film. The encoding process involves one- or two-photon excitation that results in trans–cis isomerization of azo molecules. Third-harmonic generation from the sample is used to probe the χ(3) anisotropy. We demonstrate large reversible variations of the third-harmonic generation (several times in intensity) in a sample pumped by the second harmonic of a Nd:YAG laser or a cw He–Cd laser. A microscopic model, which includes mechanisms for angular hole burning and molecular reorientation, is presented. The model is in good qualitative agreement with the experimental results.

© 2001 Optical Society of America

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References

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  1. M. Dumont, S. Hosotte, G. Froc, and Z. Sekkat, “Orientational manipulation of chromophores through photoisomerization,” in Photopolymers and Applications in Holography, Optical Data Storage, Optical Sensors, and Interconnects, R. A. Lessard, ed., Proc. SPIE 2042, 2–13 (1994).
    [CrossRef]
  2. M. Dumont, G. Froc, and S. Hosotte, “Alignment and orientation of chromophores by optical pumping,” Nonlin. Opt. 9, 327–338 (1995).
  3. A. E. Osman and M. Dumont, “Dynamical and spectroscopic study of photoinduced orientation of dye molecules in polymer films,” in Photopolymer Device Physics, Chemistry and Applications IV, R. A. Lessard, ed., Proc. SPIE 3417, 36–46 (1998).
  4. M. Dumont and A. E. Osman, “On spontaneous and photoinduced orientational mobility of dye molecules in polymers,” Chem. Phys. 245, 437–462 (1999).
    [CrossRef]
  5. C. Fiorini, F. Charra, J. M. Nunzi, and P. Raimond, “Quasi-permanent all-optical encoding of noncentrosymmetry in azo-dye polymers,” J. Opt. Soc. Am. B 14, 1984–2003 (1997).
    [CrossRef]
  6. R. Rangel-Rojo, S. Yamada, H. Matsuda, and D. Yankelevich, “Large near-resonance third order nonlinearity in azobenzene functionalized polymer film,” Appl. Phys. Lett. 72, 1021–1023 (1998).
    [CrossRef]
  7. C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
    [CrossRef]
  8. L. Misoguti, C. R. Mendonca, and S. C. Zilio, “Characterization of dynamic optical nonlinearities with pulse trains,” Appl. Phys. Lett. 74, 1531–1533 (1999).
    [CrossRef]
  9. V. M. Churikov and C. C. Hsu, “Optical control of third harmonic generation in azo-doped polymethylmethacrylate thin films,” Appl. Phys. Lett. 77, 2095–2097 (2000).
    [CrossRef]
  10. P. N. Prasad and D. J. Williams, Introduction to Nonlinear Optical Effects in Molecules and Polymers (Wiley, New York, 1991), pp. 77–79.
  11. Z. Sekkat and M. Dumont, “Polarization effects in photoisomerization of azo dyes in polymeric films,” Appl. Phys. B 53, 121–123 (1991).
    [CrossRef]
  12. Z. Sekkat and M. Dumont, “Photoassisted poling of azo dye doped polymeric films at room temperature,” Appl. Phys. B 54, 486–489 (1992).
    [CrossRef]
  13. R. W. Boyd, Nonlinear Optics (Academic, San Diego, Calif., 1992), pp. 110–115.
  14. R. H. Page, M. C. Jurich, B. Reck, A. Sen, R. J. Twieg, J. D. Swalen, G. C. Bjorklund, and C. G. Willson, “Electrochromic and optical waveguide studies of corona-poled electro-optic polymer films,” J. Opt. Soc. Am. B 7, 1239–1250 (1990).
    [CrossRef]
  15. Z. Sekkat, D. Morichere, M. Dumont, R. Loucif-Saibi, and J. A. Delaire, “Photoisomerization of azobenzene derivatives in polymeric thin films,” J. Appl. Phys. 71, 1543–1545 (1992).
    [CrossRef]
  16. V. M. Churikov, M. F. Hung, C. C. Hsu, C. W. Shiau, and T. Y. Luh, “Encoding of macroscopic second order nonlinearity via all-optical polar alignment in substituted norbornene polymer thin films,” Chem. Phys. Lett. 332, 19–25 (2000).
    [CrossRef]

2000 (2)

V. M. Churikov and C. C. Hsu, “Optical control of third harmonic generation in azo-doped polymethylmethacrylate thin films,” Appl. Phys. Lett. 77, 2095–2097 (2000).
[CrossRef]

V. M. Churikov, M. F. Hung, C. C. Hsu, C. W. Shiau, and T. Y. Luh, “Encoding of macroscopic second order nonlinearity via all-optical polar alignment in substituted norbornene polymer thin films,” Chem. Phys. Lett. 332, 19–25 (2000).
[CrossRef]

1999 (2)

L. Misoguti, C. R. Mendonca, and S. C. Zilio, “Characterization of dynamic optical nonlinearities with pulse trains,” Appl. Phys. Lett. 74, 1531–1533 (1999).
[CrossRef]

M. Dumont and A. E. Osman, “On spontaneous and photoinduced orientational mobility of dye molecules in polymers,” Chem. Phys. 245, 437–462 (1999).
[CrossRef]

1998 (2)

R. Rangel-Rojo, S. Yamada, H. Matsuda, and D. Yankelevich, “Large near-resonance third order nonlinearity in azobenzene functionalized polymer film,” Appl. Phys. Lett. 72, 1021–1023 (1998).
[CrossRef]

A. E. Osman and M. Dumont, “Dynamical and spectroscopic study of photoinduced orientation of dye molecules in polymer films,” in Photopolymer Device Physics, Chemistry and Applications IV, R. A. Lessard, ed., Proc. SPIE 3417, 36–46 (1998).

1997 (2)

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

C. Fiorini, F. Charra, J. M. Nunzi, and P. Raimond, “Quasi-permanent all-optical encoding of noncentrosymmetry in azo-dye polymers,” J. Opt. Soc. Am. B 14, 1984–2003 (1997).
[CrossRef]

1995 (1)

M. Dumont, G. Froc, and S. Hosotte, “Alignment and orientation of chromophores by optical pumping,” Nonlin. Opt. 9, 327–338 (1995).

1994 (1)

M. Dumont, S. Hosotte, G. Froc, and Z. Sekkat, “Orientational manipulation of chromophores through photoisomerization,” in Photopolymers and Applications in Holography, Optical Data Storage, Optical Sensors, and Interconnects, R. A. Lessard, ed., Proc. SPIE 2042, 2–13 (1994).
[CrossRef]

1992 (2)

Z. Sekkat and M. Dumont, “Photoassisted poling of azo dye doped polymeric films at room temperature,” Appl. Phys. B 54, 486–489 (1992).
[CrossRef]

Z. Sekkat, D. Morichere, M. Dumont, R. Loucif-Saibi, and J. A. Delaire, “Photoisomerization of azobenzene derivatives in polymeric thin films,” J. Appl. Phys. 71, 1543–1545 (1992).
[CrossRef]

1991 (1)

Z. Sekkat and M. Dumont, “Polarization effects in photoisomerization of azo dyes in polymeric films,” Appl. Phys. B 53, 121–123 (1991).
[CrossRef]

1990 (1)

Bjorklund, G. C.

Charra, F.

Churikov, V. M.

V. M. Churikov and C. C. Hsu, “Optical control of third harmonic generation in azo-doped polymethylmethacrylate thin films,” Appl. Phys. Lett. 77, 2095–2097 (2000).
[CrossRef]

V. M. Churikov, M. F. Hung, C. C. Hsu, C. W. Shiau, and T. Y. Luh, “Encoding of macroscopic second order nonlinearity via all-optical polar alignment in substituted norbornene polymer thin films,” Chem. Phys. Lett. 332, 19–25 (2000).
[CrossRef]

Delaire, J. A.

Z. Sekkat, D. Morichere, M. Dumont, R. Loucif-Saibi, and J. A. Delaire, “Photoisomerization of azobenzene derivatives in polymeric thin films,” J. Appl. Phys. 71, 1543–1545 (1992).
[CrossRef]

Dumont, M.

M. Dumont and A. E. Osman, “On spontaneous and photoinduced orientational mobility of dye molecules in polymers,” Chem. Phys. 245, 437–462 (1999).
[CrossRef]

A. E. Osman and M. Dumont, “Dynamical and spectroscopic study of photoinduced orientation of dye molecules in polymer films,” in Photopolymer Device Physics, Chemistry and Applications IV, R. A. Lessard, ed., Proc. SPIE 3417, 36–46 (1998).

M. Dumont, G. Froc, and S. Hosotte, “Alignment and orientation of chromophores by optical pumping,” Nonlin. Opt. 9, 327–338 (1995).

M. Dumont, S. Hosotte, G. Froc, and Z. Sekkat, “Orientational manipulation of chromophores through photoisomerization,” in Photopolymers and Applications in Holography, Optical Data Storage, Optical Sensors, and Interconnects, R. A. Lessard, ed., Proc. SPIE 2042, 2–13 (1994).
[CrossRef]

Z. Sekkat, D. Morichere, M. Dumont, R. Loucif-Saibi, and J. A. Delaire, “Photoisomerization of azobenzene derivatives in polymeric thin films,” J. Appl. Phys. 71, 1543–1545 (1992).
[CrossRef]

Z. Sekkat and M. Dumont, “Photoassisted poling of azo dye doped polymeric films at room temperature,” Appl. Phys. B 54, 486–489 (1992).
[CrossRef]

Z. Sekkat and M. Dumont, “Polarization effects in photoisomerization of azo dyes in polymeric films,” Appl. Phys. B 53, 121–123 (1991).
[CrossRef]

Egami, C.

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

Fiorini, C.

Froc, G.

M. Dumont, G. Froc, and S. Hosotte, “Alignment and orientation of chromophores by optical pumping,” Nonlin. Opt. 9, 327–338 (1995).

M. Dumont, S. Hosotte, G. Froc, and Z. Sekkat, “Orientational manipulation of chromophores through photoisomerization,” in Photopolymers and Applications in Holography, Optical Data Storage, Optical Sensors, and Interconnects, R. A. Lessard, ed., Proc. SPIE 2042, 2–13 (1994).
[CrossRef]

Fujimura, H.

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

Fujiwara, H.

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

Hosotte, S.

M. Dumont, G. Froc, and S. Hosotte, “Alignment and orientation of chromophores by optical pumping,” Nonlin. Opt. 9, 327–338 (1995).

M. Dumont, S. Hosotte, G. Froc, and Z. Sekkat, “Orientational manipulation of chromophores through photoisomerization,” in Photopolymers and Applications in Holography, Optical Data Storage, Optical Sensors, and Interconnects, R. A. Lessard, ed., Proc. SPIE 2042, 2–13 (1994).
[CrossRef]

Hsu, C. C.

V. M. Churikov and C. C. Hsu, “Optical control of third harmonic generation in azo-doped polymethylmethacrylate thin films,” Appl. Phys. Lett. 77, 2095–2097 (2000).
[CrossRef]

V. M. Churikov, M. F. Hung, C. C. Hsu, C. W. Shiau, and T. Y. Luh, “Encoding of macroscopic second order nonlinearity via all-optical polar alignment in substituted norbornene polymer thin films,” Chem. Phys. Lett. 332, 19–25 (2000).
[CrossRef]

Hung, M. F.

V. M. Churikov, M. F. Hung, C. C. Hsu, C. W. Shiau, and T. Y. Luh, “Encoding of macroscopic second order nonlinearity via all-optical polar alignment in substituted norbornene polymer thin films,” Chem. Phys. Lett. 332, 19–25 (2000).
[CrossRef]

Jurich, M. C.

Loucif-Saibi, R.

Z. Sekkat, D. Morichere, M. Dumont, R. Loucif-Saibi, and J. A. Delaire, “Photoisomerization of azobenzene derivatives in polymeric thin films,” J. Appl. Phys. 71, 1543–1545 (1992).
[CrossRef]

Luh, T. Y.

V. M. Churikov, M. F. Hung, C. C. Hsu, C. W. Shiau, and T. Y. Luh, “Encoding of macroscopic second order nonlinearity via all-optical polar alignment in substituted norbornene polymer thin films,” Chem. Phys. Lett. 332, 19–25 (2000).
[CrossRef]

Matsuda, H.

R. Rangel-Rojo, S. Yamada, H. Matsuda, and D. Yankelevich, “Large near-resonance third order nonlinearity in azobenzene functionalized polymer film,” Appl. Phys. Lett. 72, 1021–1023 (1998).
[CrossRef]

Mendonca, C. R.

L. Misoguti, C. R. Mendonca, and S. C. Zilio, “Characterization of dynamic optical nonlinearities with pulse trains,” Appl. Phys. Lett. 74, 1531–1533 (1999).
[CrossRef]

Misoguti, L.

L. Misoguti, C. R. Mendonca, and S. C. Zilio, “Characterization of dynamic optical nonlinearities with pulse trains,” Appl. Phys. Lett. 74, 1531–1533 (1999).
[CrossRef]

Morichere, D.

Z. Sekkat, D. Morichere, M. Dumont, R. Loucif-Saibi, and J. A. Delaire, “Photoisomerization of azobenzene derivatives in polymeric thin films,” J. Appl. Phys. 71, 1543–1545 (1992).
[CrossRef]

Nakagawa, K.

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

Nunzi, J. M.

Okamoto, N.

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

Osman, A. E.

M. Dumont and A. E. Osman, “On spontaneous and photoinduced orientational mobility of dye molecules in polymers,” Chem. Phys. 245, 437–462 (1999).
[CrossRef]

A. E. Osman and M. Dumont, “Dynamical and spectroscopic study of photoinduced orientation of dye molecules in polymer films,” in Photopolymer Device Physics, Chemistry and Applications IV, R. A. Lessard, ed., Proc. SPIE 3417, 36–46 (1998).

Page, R. H.

Raimond, P.

Rangel-Rojo, R.

R. Rangel-Rojo, S. Yamada, H. Matsuda, and D. Yankelevich, “Large near-resonance third order nonlinearity in azobenzene functionalized polymer film,” Appl. Phys. Lett. 72, 1021–1023 (1998).
[CrossRef]

Reck, B.

Sekkat, Z.

M. Dumont, S. Hosotte, G. Froc, and Z. Sekkat, “Orientational manipulation of chromophores through photoisomerization,” in Photopolymers and Applications in Holography, Optical Data Storage, Optical Sensors, and Interconnects, R. A. Lessard, ed., Proc. SPIE 2042, 2–13 (1994).
[CrossRef]

Z. Sekkat, D. Morichere, M. Dumont, R. Loucif-Saibi, and J. A. Delaire, “Photoisomerization of azobenzene derivatives in polymeric thin films,” J. Appl. Phys. 71, 1543–1545 (1992).
[CrossRef]

Z. Sekkat and M. Dumont, “Photoassisted poling of azo dye doped polymeric films at room temperature,” Appl. Phys. B 54, 486–489 (1992).
[CrossRef]

Z. Sekkat and M. Dumont, “Polarization effects in photoisomerization of azo dyes in polymeric films,” Appl. Phys. B 53, 121–123 (1991).
[CrossRef]

Sen, A.

Shiau, C. W.

V. M. Churikov, M. F. Hung, C. C. Hsu, C. W. Shiau, and T. Y. Luh, “Encoding of macroscopic second order nonlinearity via all-optical polar alignment in substituted norbornene polymer thin films,” Chem. Phys. Lett. 332, 19–25 (2000).
[CrossRef]

Sugihara, O.

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

Suzuki, Y.

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

Swalen, J. D.

Twieg, R. J.

Willson, C. G.

Yamada, S.

R. Rangel-Rojo, S. Yamada, H. Matsuda, and D. Yankelevich, “Large near-resonance third order nonlinearity in azobenzene functionalized polymer film,” Appl. Phys. Lett. 72, 1021–1023 (1998).
[CrossRef]

Yankelevich, D.

R. Rangel-Rojo, S. Yamada, H. Matsuda, and D. Yankelevich, “Large near-resonance third order nonlinearity in azobenzene functionalized polymer film,” Appl. Phys. Lett. 72, 1021–1023 (1998).
[CrossRef]

Zilio, S. C.

L. Misoguti, C. R. Mendonca, and S. C. Zilio, “Characterization of dynamic optical nonlinearities with pulse trains,” Appl. Phys. Lett. 74, 1531–1533 (1999).
[CrossRef]

Appl. Phys. B (3)

C. Egami, Y. Suzuki, O. Sugihara, N. Okamoto, H. Fujimura, K. Nakagawa, and H. Fujiwara, “Third-order resonant optical nonlinearity from trans–cis photoisomerization of an azo dye in a rigid matrix,” Appl. Phys. B 64, 471–478 (1997).
[CrossRef]

Z. Sekkat and M. Dumont, “Polarization effects in photoisomerization of azo dyes in polymeric films,” Appl. Phys. B 53, 121–123 (1991).
[CrossRef]

Z. Sekkat and M. Dumont, “Photoassisted poling of azo dye doped polymeric films at room temperature,” Appl. Phys. B 54, 486–489 (1992).
[CrossRef]

Appl. Phys. Lett. (3)

R. Rangel-Rojo, S. Yamada, H. Matsuda, and D. Yankelevich, “Large near-resonance third order nonlinearity in azobenzene functionalized polymer film,” Appl. Phys. Lett. 72, 1021–1023 (1998).
[CrossRef]

L. Misoguti, C. R. Mendonca, and S. C. Zilio, “Characterization of dynamic optical nonlinearities with pulse trains,” Appl. Phys. Lett. 74, 1531–1533 (1999).
[CrossRef]

V. M. Churikov and C. C. Hsu, “Optical control of third harmonic generation in azo-doped polymethylmethacrylate thin films,” Appl. Phys. Lett. 77, 2095–2097 (2000).
[CrossRef]

Chem. Phys. (1)

M. Dumont and A. E. Osman, “On spontaneous and photoinduced orientational mobility of dye molecules in polymers,” Chem. Phys. 245, 437–462 (1999).
[CrossRef]

Chem. Phys. Lett. (1)

V. M. Churikov, M. F. Hung, C. C. Hsu, C. W. Shiau, and T. Y. Luh, “Encoding of macroscopic second order nonlinearity via all-optical polar alignment in substituted norbornene polymer thin films,” Chem. Phys. Lett. 332, 19–25 (2000).
[CrossRef]

J. Appl. Phys. (1)

Z. Sekkat, D. Morichere, M. Dumont, R. Loucif-Saibi, and J. A. Delaire, “Photoisomerization of azobenzene derivatives in polymeric thin films,” J. Appl. Phys. 71, 1543–1545 (1992).
[CrossRef]

J. Opt. Soc. Am. B (2)

Nonlin. Opt. (1)

M. Dumont, G. Froc, and S. Hosotte, “Alignment and orientation of chromophores by optical pumping,” Nonlin. Opt. 9, 327–338 (1995).

Proc. SPIE (2)

A. E. Osman and M. Dumont, “Dynamical and spectroscopic study of photoinduced orientation of dye molecules in polymer films,” in Photopolymer Device Physics, Chemistry and Applications IV, R. A. Lessard, ed., Proc. SPIE 3417, 36–46 (1998).

M. Dumont, S. Hosotte, G. Froc, and Z. Sekkat, “Orientational manipulation of chromophores through photoisomerization,” in Photopolymers and Applications in Holography, Optical Data Storage, Optical Sensors, and Interconnects, R. A. Lessard, ed., Proc. SPIE 2042, 2–13 (1994).
[CrossRef]

Other (2)

R. W. Boyd, Nonlinear Optics (Academic, San Diego, Calif., 1992), pp. 110–115.

P. N. Prasad and D. J. Williams, Introduction to Nonlinear Optical Effects in Molecules and Polymers (Wiley, New York, 1991), pp. 77–79.

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Figures (10)

Fig. 1
Fig. 1

Structure of DR1 molecule, of trans–cis photoisomerization, and cis–trans thermal relaxation.

Fig. 2
Fig. 2

Simplified three-level schematic for trans–cis photoisomerization of the DR1 molecule. Here σT is the absorption cross section of molecules whose dipole moments are parallel to the pump field, ϕTC is the quantum yield for the trans-to-cis transition, and ηCT is the thermal relaxation rate from cis to trans.

Fig. 3
Fig. 3

Setup for Nd:YAG and He–Cd laser experiments: 1, Nd:YAG laser; 2, 4, 1064-nm mirrors; 3, glass plate; 5, β-barium borate crystal; 6, 7, half-wave (λ/2) plates; 8, 9, 355-nm mirror pair; 10, polarizer; 11, color filter; 12, 13, lenses; 14, thin-film sample; 15, fast photodiode; 16, iris pinhole; 17, 21, neutral-density filters; 18, PMT; 19, pump damper; 20, He–Cd laser; 22, mirror.

Fig. 4
Fig. 4

Absorption spectrum of the DR1 PMMA thin film.

Fig. 5
Fig. 5

355-nm light transmitted (a) through the sample without pumping and (b) through the sample pumped by the SH of a Nd:YAG laser or (c), (d) by a cw He–Cd laser. The pump and the probe are copolarized (‖) and perpendicularly polarized (⊥), respectively. The average pump intensity is indicated in each case. The curves for ‖ and ⊥ are given in arbitrary units, as they were obtained from but not normalized to the same initial level. In this and the following figures, the first point (t=0) and a dashed line represent the initial TH level obtained by averaging of 10 points before pumping.

Fig. 6
Fig. 6

TH intensity as a function of time in the sample pumped by the SH of a Nd:YAG laser. The sample was probed with the fundamental beam copolarized (‖) and perpendicularly polarized (⊥) with the pump beam. The curves for ‖ and ⊥ are normalized to the same initial level and represent a relative change in the TH-generation level.

Fig. 7
Fig. 7

TH generation in the DR1 PMMA thin film pumped by the fundamental beam as a function of time. The average intensity of the pump beam is shown in each case.

Fig. 8
Fig. 8

Normalized value Δχ(3)/χ0(3)=1-I/I0 versus pump intensity in cases of excitation by the 532-nm pump. The solid curve is the AHB theoretical dependence of Δχ(3)/χ0(3) obtained from Eq. (7a) with the parameters ϕTC=0.11, ηCT0.5 s-1, and σT3×10-17 cm2 for DR1 PMMA.

Fig. 9
Fig. 9

TH intensity as a function of time in the sample pumped by a cw He–Cd laser. The sample was probed by the fundamental beam copolarized (‖) and perpendicularly polarized (⊥) with the pump beam.

Fig. 10
Fig. 10

TH intensity as a function of polarization angle φ of the probe beam before pumping (leftmost column), (a), (b) after 8 min of pumping with 532- and 442-nm light, respectively, of 0.3-W/cm2 average intensity and (c) 442-nm light of 3-W/cm2 intensity (second column), after 1 min of dark relaxation (third column), and following 15 min of dark relaxation (fourth column). The zero angle corresponds to the plane of polarization of the pump.

Equations (19)

Equations on this page are rendered with MathJax. Learn more.

χ(3)(-3ω, ω, ω, ω)=f4γ  NT(Ω)cos4 θdΩ,
dNT(Ω)/dt=-NT(Ω)ϕTCPr(θp)+NC(Ω)ηCT,
NT(Ω)=(N/4π)(1+a2 cos2 θp)-1,
N(θp)=(N/4π)j(2 j+1)AjPj(cos θp).
Am=(1/2)0π Pm(cos θ)sin θdθ1+a2 cos2 θ.
A0=arctan aa,
A2=32a2 1-arctan aa-a arctan a3,
A4=58a2 a arctan a5 35a4+30a2+3-7a2-113.
χ(3)=f4γN3a2 1-3a2+3 arctan aa3,
χ(3)=3f4γN8 arctan a1a+2a3+1a5-53a2-1a4.
χ(3)=χiso(3)+χ(3)=χiso(3)-(1/7)f4a2γN,
χ(3)=χiso(3)+Δχ(3)=χiso(3)-(1/35)f4a2γN,
NT(Ω)=(N/4π)(1-b2 cos4 θp),
dNT(Ω)/dt=-NT(Ω)ϕTCPr(θp)+ϕTCNT(Ω1)Pr(θp1)R(Ω1Ω)dΩ1+D2NT(Ω).
A0=1(thetranspopulationdoesnotchange),
A2=215×[20ξ+(39/77)](16/245)-[6ξ+(11/21)][20ξ+(39/77)],
A4=-8315×1(16/245)-[6ξ+(11/21)][20ξ+(39/77)],
χ(3)=f4γN15+47A2+835A4=χiso(3)+Δχ(3),
χ(3)=f4γN15-27A2+335A4=χiso(3)+Δχ(3).

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