Abstract

Photoinduced nonlinear optical phenomena in Sb2Te3CaCl2PbCl2 glasses have been studied by experimental and theoretical quantum chemistry and molecular dynamics methods. Additionally, photoinduced two-photon absorption (TPA) and second-harmonic generation (SHG) were measured in the IR region from 5.8 to 18 µm. A CO laser (λ=5.5 µm) and parametrically generated wavelengths (5.7–13.4 µm) were used as a source of pump light. With an increase of the photoinducing power, the SHG signal increased for a probe CO2 laser (with double frequency λ=5.7 µm) and achieved its maximum value at a photoinducing power of 1.65 GW/cm2 per pulse. Absolute values of the SHG intensities were more than 1 order of magnitude less than those of χ222 nonlinear optical tensor components for Ag3AsSe3 single crystals. The SHG signal increases strongly for a temperature decrease from 39 to 26 K. Femtosecond probe–pump measurements indicate a SHG maximum at a pump–probe delay time of ∼18 ps. The spectral positions of the TPA maxima depend strongly on the pump power. Differently from the SHG behavior, the TPA results show at least two time-delayed maxima, namely, at 14–17 and 45 ps. These dependencies are explained within the framework of the quantum-chemistry approach, which takes into account photoinduced anharmonic electron–vibration interactions. The Sb–Te tetrahedral plays a key role in the observed photoinduced nonlinear optics effects. The results clearly show that these effects can be used as powerful tools for investigation of picosecond IR nonlinear optics. In addition, these glasses are promising materials for IR femtosecond quantum electronics.

© 1999 Optical Society of America

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References

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  1. M. A. Vorobijow, “Properties and technology of the A2Te3–CaCl2–PbCl2 glasses,” Steklo Keramika 24, 235–243 (1997).
  2. R. Sewrin, “Technological problems in the synthesis of the Me2Te3–CaCl2–PbCl2 glasses,” Ph.D. dissertation (St. Petersburg University, St. Petersburg, Russia, 1998), pp. 545–549.
  3. M. Kasipor, “Opto-mechanical parameters of the Sb2Te3–CaCl2–PbCl2 glasses,” in Trends in Glass Society (Sweet, Kiev, Ukraine, 1998), pp. 21–26.
  4. J. Wasylak, J. Kucharski, I. V. Kityk, and B. Sahraoui, “Photoinduced effects in the Sb2Se3–BaCl2–PbCl2 glasses,” J. Appl. Phys. 85, 425–431 (1999).
    [CrossRef]
  5. G. J. Adriaenssens, V. K. Tikhomirov, and S. R. Elliott, “Mechanism and kinetics of photoinduced anisotropy in chalcogenide glasses,” J. Non-Cryst. Solids 227–230, 688–693 (1998).
    [CrossRef]
  6. K. Iakoubovskii, P. W. Hertogen, and G. J. Adriaensens, “Photoinduced anisotropy and polarization memory of the photoluminescence in germanium sulfide glasses,” J. Non-Cryst. Solids 240, 237–241 (1998).
    [CrossRef]
  7. V. M. Lyubin and V. K. Tikhomirov, “Novel photo-induced in chalcogenide glasses,” J. Non-Cryst. Solids 133, 37–48 (1991).
    [CrossRef]
  8. V. K. Tikhomirov and S. R. Elliott, “Metastable optical anisotropy in chalcogenide glasses induced by unpolarized light,” Phys. Rev. B 49, 17, 646–17, 650 (1994).
    [CrossRef]
  9. J. T. Chen, Q. D. Liu, P. P. Ho, and R. R. Alfano, “Comparison of nonlinear effects of linearly and circularly polarized picosecond pulses propagating in optical fibers,” J. Opt. Soc. Am. B 12, 907–912 (1995); E. Golis, I. V. Kityk, J. Wasylak, and J. Kasperczyk, “Nonlinear optical properties of lead–bismuth–gallium glasses,” Mater. Res. Bull. 31, 1057–1065 (1996).
    [CrossRef]
  10. N. Sugimoto, H. Kanbara, S. Fujiwara, and K. Tanaka, “Ultrafast response of third-order optical nonlinearity in glasses containing Bi2O3,” Opt. Lett. 21, 1637–1639 (1996).
    [CrossRef] [PubMed]
  11. K. Nagaya, T. Hayakawa, M. Yao, and H. Endo, “Photo-induced effects on chalcogen free microclusters,” J. Non-Cryst. Solids 205–207, 807–810 (1996).
    [CrossRef]
  12. J. Zyss and D. S. Chemla, Quantum Electronics (Principles and Applications) (Academic, New York, 1987), Vols. 1 and 2.
  13. J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
    [CrossRef]
  14. M. Krajci and J. Hafner, “Structural and electronic properties of liquid and amorphous carbon calculated by the ‘fuzzy’ tight-binding Monte Carlo method,” J. Non-Cryst. Solids 205–207, 846–850 (1996).
    [CrossRef]
  15. A. D. Becke, “New methods of molecular dynamics simulations,” J. Chem. Phys. 98, 1372–1384 (1994).
    [CrossRef]
  16. B. Sahraoui, I. V. Kityk, X. N. Phu, P. Hudhomme, and A. Gorgues, “Influence of hydrostatic pressure and temperature on two-photon absorption of a C60-2-thioxo-1, 3-dithiole cycloadduct,” Phys. Rev. B 59, 9229–9239 (1999).
    [CrossRef]
  17. O. I. Shpotyuk, J. Kasperczyk, and I. V. Kityk, “Mechanism of reversible photoinduced optical effects in amorphous As2S3,” J. Non-Cryst. Solids 215, 218–225 (1997).
    [CrossRef]
  18. M. J. Frisch, G. W. Trucks, H. W. Schlegel, P. M. W. Gill, B. G. Johnson, M. W. Wong, J. B. Foresman, M. Head-Gordon, E. S. Replogle, R. Gomperts, J. L. Andres, K. Raghvachari, J. S. Binkley, C. Gonzales, R. L. Martin, D. J. Fox, D. Defrees, J. Baker, J. J. P. Stewart, and J. A. Pople, GAUSSIAN 94 program, Rev. C3 (Gaussian, Inc., Pittsburgh, Pa., 1994).

1999

J. Wasylak, J. Kucharski, I. V. Kityk, and B. Sahraoui, “Photoinduced effects in the Sb2Se3–BaCl2–PbCl2 glasses,” J. Appl. Phys. 85, 425–431 (1999).
[CrossRef]

B. Sahraoui, I. V. Kityk, X. N. Phu, P. Hudhomme, and A. Gorgues, “Influence of hydrostatic pressure and temperature on two-photon absorption of a C60-2-thioxo-1, 3-dithiole cycloadduct,” Phys. Rev. B 59, 9229–9239 (1999).
[CrossRef]

1998

G. J. Adriaenssens, V. K. Tikhomirov, and S. R. Elliott, “Mechanism and kinetics of photoinduced anisotropy in chalcogenide glasses,” J. Non-Cryst. Solids 227–230, 688–693 (1998).
[CrossRef]

K. Iakoubovskii, P. W. Hertogen, and G. J. Adriaensens, “Photoinduced anisotropy and polarization memory of the photoluminescence in germanium sulfide glasses,” J. Non-Cryst. Solids 240, 237–241 (1998).
[CrossRef]

1997

O. I. Shpotyuk, J. Kasperczyk, and I. V. Kityk, “Mechanism of reversible photoinduced optical effects in amorphous As2S3,” J. Non-Cryst. Solids 215, 218–225 (1997).
[CrossRef]

M. A. Vorobijow, “Properties and technology of the A2Te3–CaCl2–PbCl2 glasses,” Steklo Keramika 24, 235–243 (1997).

1996

N. Sugimoto, H. Kanbara, S. Fujiwara, and K. Tanaka, “Ultrafast response of third-order optical nonlinearity in glasses containing Bi2O3,” Opt. Lett. 21, 1637–1639 (1996).
[CrossRef] [PubMed]

K. Nagaya, T. Hayakawa, M. Yao, and H. Endo, “Photo-induced effects on chalcogen free microclusters,” J. Non-Cryst. Solids 205–207, 807–810 (1996).
[CrossRef]

J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
[CrossRef]

M. Krajci and J. Hafner, “Structural and electronic properties of liquid and amorphous carbon calculated by the ‘fuzzy’ tight-binding Monte Carlo method,” J. Non-Cryst. Solids 205–207, 846–850 (1996).
[CrossRef]

1994

A. D. Becke, “New methods of molecular dynamics simulations,” J. Chem. Phys. 98, 1372–1384 (1994).
[CrossRef]

V. K. Tikhomirov and S. R. Elliott, “Metastable optical anisotropy in chalcogenide glasses induced by unpolarized light,” Phys. Rev. B 49, 17, 646–17, 650 (1994).
[CrossRef]

1991

V. M. Lyubin and V. K. Tikhomirov, “Novel photo-induced in chalcogenide glasses,” J. Non-Cryst. Solids 133, 37–48 (1991).
[CrossRef]

Adriaensens, G. J.

K. Iakoubovskii, P. W. Hertogen, and G. J. Adriaensens, “Photoinduced anisotropy and polarization memory of the photoluminescence in germanium sulfide glasses,” J. Non-Cryst. Solids 240, 237–241 (1998).
[CrossRef]

Adriaenssens, G. J.

G. J. Adriaenssens, V. K. Tikhomirov, and S. R. Elliott, “Mechanism and kinetics of photoinduced anisotropy in chalcogenide glasses,” J. Non-Cryst. Solids 227–230, 688–693 (1998).
[CrossRef]

Becke, A. D.

A. D. Becke, “New methods of molecular dynamics simulations,” J. Chem. Phys. 98, 1372–1384 (1994).
[CrossRef]

Elliott, S. R.

G. J. Adriaenssens, V. K. Tikhomirov, and S. R. Elliott, “Mechanism and kinetics of photoinduced anisotropy in chalcogenide glasses,” J. Non-Cryst. Solids 227–230, 688–693 (1998).
[CrossRef]

V. K. Tikhomirov and S. R. Elliott, “Metastable optical anisotropy in chalcogenide glasses induced by unpolarized light,” Phys. Rev. B 49, 17, 646–17, 650 (1994).
[CrossRef]

Endo, H.

K. Nagaya, T. Hayakawa, M. Yao, and H. Endo, “Photo-induced effects on chalcogen free microclusters,” J. Non-Cryst. Solids 205–207, 807–810 (1996).
[CrossRef]

Fujiwara, S.

Gorgues, A.

B. Sahraoui, I. V. Kityk, X. N. Phu, P. Hudhomme, and A. Gorgues, “Influence of hydrostatic pressure and temperature on two-photon absorption of a C60-2-thioxo-1, 3-dithiole cycloadduct,” Phys. Rev. B 59, 9229–9239 (1999).
[CrossRef]

Hafner, J.

M. Krajci and J. Hafner, “Structural and electronic properties of liquid and amorphous carbon calculated by the ‘fuzzy’ tight-binding Monte Carlo method,” J. Non-Cryst. Solids 205–207, 846–850 (1996).
[CrossRef]

Hayakawa, T.

K. Nagaya, T. Hayakawa, M. Yao, and H. Endo, “Photo-induced effects on chalcogen free microclusters,” J. Non-Cryst. Solids 205–207, 807–810 (1996).
[CrossRef]

Hertogen, P. W.

K. Iakoubovskii, P. W. Hertogen, and G. J. Adriaensens, “Photoinduced anisotropy and polarization memory of the photoluminescence in germanium sulfide glasses,” J. Non-Cryst. Solids 240, 237–241 (1998).
[CrossRef]

Hudhomme, P.

B. Sahraoui, I. V. Kityk, X. N. Phu, P. Hudhomme, and A. Gorgues, “Influence of hydrostatic pressure and temperature on two-photon absorption of a C60-2-thioxo-1, 3-dithiole cycloadduct,” Phys. Rev. B 59, 9229–9239 (1999).
[CrossRef]

Iakoubovskii, K.

K. Iakoubovskii, P. W. Hertogen, and G. J. Adriaensens, “Photoinduced anisotropy and polarization memory of the photoluminescence in germanium sulfide glasses,” J. Non-Cryst. Solids 240, 237–241 (1998).
[CrossRef]

Kanbara, H.

Kasperczyk, J.

O. I. Shpotyuk, J. Kasperczyk, and I. V. Kityk, “Mechanism of reversible photoinduced optical effects in amorphous As2S3,” J. Non-Cryst. Solids 215, 218–225 (1997).
[CrossRef]

Kityk, I. V.

B. Sahraoui, I. V. Kityk, X. N. Phu, P. Hudhomme, and A. Gorgues, “Influence of hydrostatic pressure and temperature on two-photon absorption of a C60-2-thioxo-1, 3-dithiole cycloadduct,” Phys. Rev. B 59, 9229–9239 (1999).
[CrossRef]

J. Wasylak, J. Kucharski, I. V. Kityk, and B. Sahraoui, “Photoinduced effects in the Sb2Se3–BaCl2–PbCl2 glasses,” J. Appl. Phys. 85, 425–431 (1999).
[CrossRef]

O. I. Shpotyuk, J. Kasperczyk, and I. V. Kityk, “Mechanism of reversible photoinduced optical effects in amorphous As2S3,” J. Non-Cryst. Solids 215, 218–225 (1997).
[CrossRef]

Krajci, M.

M. Krajci and J. Hafner, “Structural and electronic properties of liquid and amorphous carbon calculated by the ‘fuzzy’ tight-binding Monte Carlo method,” J. Non-Cryst. Solids 205–207, 846–850 (1996).
[CrossRef]

Kucharski, J.

J. Wasylak, J. Kucharski, I. V. Kityk, and B. Sahraoui, “Photoinduced effects in the Sb2Se3–BaCl2–PbCl2 glasses,” J. Appl. Phys. 85, 425–431 (1999).
[CrossRef]

Lyubin, V. M.

V. M. Lyubin and V. K. Tikhomirov, “Novel photo-induced in chalcogenide glasses,” J. Non-Cryst. Solids 133, 37–48 (1991).
[CrossRef]

Nagaya, K.

K. Nagaya, T. Hayakawa, M. Yao, and H. Endo, “Photo-induced effects on chalcogen free microclusters,” J. Non-Cryst. Solids 205–207, 807–810 (1996).
[CrossRef]

Nicholson, D. M. C.

J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
[CrossRef]

Phu, X. N.

B. Sahraoui, I. V. Kityk, X. N. Phu, P. Hudhomme, and A. Gorgues, “Influence of hydrostatic pressure and temperature on two-photon absorption of a C60-2-thioxo-1, 3-dithiole cycloadduct,” Phys. Rev. B 59, 9229–9239 (1999).
[CrossRef]

Sahraoui, B.

B. Sahraoui, I. V. Kityk, X. N. Phu, P. Hudhomme, and A. Gorgues, “Influence of hydrostatic pressure and temperature on two-photon absorption of a C60-2-thioxo-1, 3-dithiole cycloadduct,” Phys. Rev. B 59, 9229–9239 (1999).
[CrossRef]

J. Wasylak, J. Kucharski, I. V. Kityk, and B. Sahraoui, “Photoinduced effects in the Sb2Se3–BaCl2–PbCl2 glasses,” J. Appl. Phys. 85, 425–431 (1999).
[CrossRef]

Shelton, W. A.

J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
[CrossRef]

Shpotyuk, O. I.

O. I. Shpotyuk, J. Kasperczyk, and I. V. Kityk, “Mechanism of reversible photoinduced optical effects in amorphous As2S3,” J. Non-Cryst. Solids 215, 218–225 (1997).
[CrossRef]

Stocks, G. M.

J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
[CrossRef]

Sugimoto, N.

Swihart, J. C.

J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
[CrossRef]

Tanaka, K.

Tikhomirov, V. K.

G. J. Adriaenssens, V. K. Tikhomirov, and S. R. Elliott, “Mechanism and kinetics of photoinduced anisotropy in chalcogenide glasses,” J. Non-Cryst. Solids 227–230, 688–693 (1998).
[CrossRef]

V. K. Tikhomirov and S. R. Elliott, “Metastable optical anisotropy in chalcogenide glasses induced by unpolarized light,” Phys. Rev. B 49, 17, 646–17, 650 (1994).
[CrossRef]

V. M. Lyubin and V. K. Tikhomirov, “Novel photo-induced in chalcogenide glasses,” J. Non-Cryst. Solids 133, 37–48 (1991).
[CrossRef]

Vorobijow, M. A.

M. A. Vorobijow, “Properties and technology of the A2Te3–CaCl2–PbCl2 glasses,” Steklo Keramika 24, 235–243 (1997).

Wang, Y.

J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
[CrossRef]

Wasylak, J.

J. Wasylak, J. Kucharski, I. V. Kityk, and B. Sahraoui, “Photoinduced effects in the Sb2Se3–BaCl2–PbCl2 glasses,” J. Appl. Phys. 85, 425–431 (1999).
[CrossRef]

Yang, H.

J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
[CrossRef]

Yao, M.

K. Nagaya, T. Hayakawa, M. Yao, and H. Endo, “Photo-induced effects on chalcogen free microclusters,” J. Non-Cryst. Solids 205–207, 807–810 (1996).
[CrossRef]

J. Appl. Phys.

J. Wasylak, J. Kucharski, I. V. Kityk, and B. Sahraoui, “Photoinduced effects in the Sb2Se3–BaCl2–PbCl2 glasses,” J. Appl. Phys. 85, 425–431 (1999).
[CrossRef]

J. Chem. Phys.

A. D. Becke, “New methods of molecular dynamics simulations,” J. Chem. Phys. 98, 1372–1384 (1994).
[CrossRef]

J. Non-Cryst. Solids

J. C. Swihart, D. M. C. Nicholson, G. M. Stocks, Y. Wang, W. A. Shelton, and H. Yang, “Calculation of electronic properties of amorphous alloys,” J. Non-Cryst. Solids 205–207, 841–845 (1996).
[CrossRef]

M. Krajci and J. Hafner, “Structural and electronic properties of liquid and amorphous carbon calculated by the ‘fuzzy’ tight-binding Monte Carlo method,” J. Non-Cryst. Solids 205–207, 846–850 (1996).
[CrossRef]

O. I. Shpotyuk, J. Kasperczyk, and I. V. Kityk, “Mechanism of reversible photoinduced optical effects in amorphous As2S3,” J. Non-Cryst. Solids 215, 218–225 (1997).
[CrossRef]

G. J. Adriaenssens, V. K. Tikhomirov, and S. R. Elliott, “Mechanism and kinetics of photoinduced anisotropy in chalcogenide glasses,” J. Non-Cryst. Solids 227–230, 688–693 (1998).
[CrossRef]

K. Iakoubovskii, P. W. Hertogen, and G. J. Adriaensens, “Photoinduced anisotropy and polarization memory of the photoluminescence in germanium sulfide glasses,” J. Non-Cryst. Solids 240, 237–241 (1998).
[CrossRef]

V. M. Lyubin and V. K. Tikhomirov, “Novel photo-induced in chalcogenide glasses,” J. Non-Cryst. Solids 133, 37–48 (1991).
[CrossRef]

K. Nagaya, T. Hayakawa, M. Yao, and H. Endo, “Photo-induced effects on chalcogen free microclusters,” J. Non-Cryst. Solids 205–207, 807–810 (1996).
[CrossRef]

Opt. Lett.

Phys. Rev. B

B. Sahraoui, I. V. Kityk, X. N. Phu, P. Hudhomme, and A. Gorgues, “Influence of hydrostatic pressure and temperature on two-photon absorption of a C60-2-thioxo-1, 3-dithiole cycloadduct,” Phys. Rev. B 59, 9229–9239 (1999).
[CrossRef]

V. K. Tikhomirov and S. R. Elliott, “Metastable optical anisotropy in chalcogenide glasses induced by unpolarized light,” Phys. Rev. B 49, 17, 646–17, 650 (1994).
[CrossRef]

Steklo Keramika

M. A. Vorobijow, “Properties and technology of the A2Te3–CaCl2–PbCl2 glasses,” Steklo Keramika 24, 235–243 (1997).

Other

R. Sewrin, “Technological problems in the synthesis of the Me2Te3–CaCl2–PbCl2 glasses,” Ph.D. dissertation (St. Petersburg University, St. Petersburg, Russia, 1998), pp. 545–549.

M. Kasipor, “Opto-mechanical parameters of the Sb2Te3–CaCl2–PbCl2 glasses,” in Trends in Glass Society (Sweet, Kiev, Ukraine, 1998), pp. 21–26.

J. Zyss and D. S. Chemla, Quantum Electronics (Principles and Applications) (Academic, New York, 1987), Vols. 1 and 2.

J. T. Chen, Q. D. Liu, P. P. Ho, and R. R. Alfano, “Comparison of nonlinear effects of linearly and circularly polarized picosecond pulses propagating in optical fibers,” J. Opt. Soc. Am. B 12, 907–912 (1995); E. Golis, I. V. Kityk, J. Wasylak, and J. Kasperczyk, “Nonlinear optical properties of lead–bismuth–gallium glasses,” Mater. Res. Bull. 31, 1057–1065 (1996).
[CrossRef]

M. J. Frisch, G. W. Trucks, H. W. Schlegel, P. M. W. Gill, B. G. Johnson, M. W. Wong, J. B. Foresman, M. Head-Gordon, E. S. Replogle, R. Gomperts, J. L. Andres, K. Raghvachari, J. S. Binkley, C. Gonzales, R. L. Martin, D. J. Fox, D. Defrees, J. Baker, J. J. P. Stewart, and J. A. Pople, GAUSSIAN 94 program, Rev. C3 (Gaussian, Inc., Pittsburgh, Pa., 1994).

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Figures (10)

Fig. 1
Fig. 1

Phototransparency of SbTeCaCl2PbCl2 glasses.

Fig. 2
Fig. 2

Experimental setup for measurement of photoinducing SHG and TPA in SbTeCaCl2PbCl2 glasses: M, mirror; L, lens; P2, polarizer; F, filter; B, bolometer; MP, multiplier; other abbreviations defined in text.

Fig. 3
Fig. 3

Dependence of photoinduced SHG (λ=5.3 µm) on photoinducing CO-laser intensity at four temperatures: crosses, 4.2 K; dashed curve, 8.6 K; open squares, 16.3 K; filled circles, 22.4 K. Measurements correspond to a time delay between probe and pump light of ∼25 ps.

Fig. 4
Fig. 4

Dependence of TPA (λ=5.3 µm) on pump–probe time delay for three temperatures: crosses, 4.2 K; open squares, 8.6 K; filled circles, 16.3 K.

Fig. 5
Fig. 5

Spectral dependence of TPA for four temperatures: crosses, 4.2 K; open diamonds, 8.6 K; open squares, 16.3 K; filled circles, 22.4 K.

Fig. 6
Fig. 6

Spectral dependence of the imaginary part 2(E) of the dielectric susceptibility: filled circles, before IR photoexposure; filled squares, during IR photoexposure of 1.2 GW/cm2; crosses, theoretically calculated without inclusion of excited states; solid curve, theoretically calculated with inclusion of excited states.

Fig. 7
Fig. 7

Changes of electronic charge density distribution in a SbTe4 cluster (increments of 0.45e/Ω) (a) before and (b) after laser photoexposure.

Fig. 8
Fig. 8

Theoretically calculated dependence of photoinduced SHG (λ=5.3 µm) on photoinducing CO-laser intensity and temperature.

Fig. 9
Fig. 9

Theoretically calculated dependence of TPA (λ=0.53 mm) on pump–probe time delay and temperature.

Fig. 10
Fig. 10

Calculated spectral dependence of TPA on temperature and wavelength.

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