M. Goulkov, G. Jäkel, E. Krätzig, S. Odoulov, and
R. Schulz, "Influence of different impurities on light-induced scattering in
doped LiNbO_{3}/sub> crystals," Opt. Mater. 4, 314–317
(1995).

K. Nakagava and T. Minemoto, "Conical diffraction
induced by two extraordinary waves," J. Opt. Soc. Am. B 11, 1639–1643
(1994).

S. R. Montgomery, M. P. Gallagher, G. J. Salamo,
E. J. Sharp, G. L. Wood, and R. R. Neurgaonkar, "Cooperative photorefractive
beam fanning in BaSrKNaNb_{5}O_{15}," J. Opt. Soc. Am B. 11,
1694–1699 (1994).

B. Sturman, M. Goulkov, and S. Odoulov,
"Polarizatio-degenerate parametric light scattering in photorefractive
crystals," Appl. Phys. B 56, 193–199 (1993).

M. Yu. Goulkov, S. G. Odoulov, B. I. Sturman,
"Polarization-anisotropic scattering lines in LiNbO_{3}," Appl.
Phys. B 56, 223–228 (1993).

A. V. Ilenkov, S. G. Odoulov, M. S. Soskin, and
M. V. Vasnetsov, "Phase-matched light-induced scattering, mirrorless
self-generation, and oscillation of nearly retropropagating waves in
LiNbO_{3}:Fe in 'forbidden' interaction geometry," Appl. Phys. B
55, 509–512 (1992).

M. Goulkov, S. Odoulov, U. van Olfen, and E.
Krätzig, "A new light-induced scattering process in photorefractive
BaTiO_{3}," Phys. Stat. Sol. (B) 172, K37–K40
(1992).

S. G. Odulov and B. I. Sturman, "Parametric
polarization scattering of light in photorefractive BaTiO_{3}," Sov.
Phys. JETP 75, 241–249 (1992).

M. Horowitz and B. Fisher, "Parametric scattering
with constructive and destructive light patterns induced by two mutually
incoherent beams in photorefractive crystals," Opt. Lett. 17, 1082–1084
(1992).

A. Novikov, S. Odoulov, R. Jungen, and T.
Tschudi, "Spatial subharmonic generation in BaTiO_{3}," J. Opt. Soc.
Am. B 9, 1654–1660 (1992).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Parametric conical scattering of two orthogonally polarized waves
in BaTiO_{3}," J. Opt. Soc. Am. B 9, 1648–1653
(1992).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Nonlinear scattering in BaTiO_{3}/sub> induced by two
orthogonally polarized waves," Appl. Phys. B 52, 317–322
(1991).

I. N. Kiseleva, V. V. Obukhovskii, S. G. Odoulov,
and O. I. Oleinik, "Photoinduced light dispersion in crystals with
biharmonic pump," Ukr. Phys. J. 31, 1682–1686 (1986).

D. A. Temple and C. Warde, "Anisotropic
scattering in photorefractive crystals," J. Opt. Soc. Am. B 3, 337–341
(1986).

M. D. Ewbank, P. Yeh, and J. Feinberg,
"Photorefractive conical diffraction in BaTiO_{3}," Opt. Commun. 59,
423–428 (1986).

R. A. Rupp and F. W. Dress, "Light-induced
scattering in photorefractive crystals," Appl. Phys. B 39, 223–229
(1986).

I. N. Kiseleva, V. V. Obuchovskii, and S. G.
Odoulov, "Parametric scattering of the holographic type in class 3m
crystals," Sov. Phys. Solid State 28, 1673–1676 (1986).

K. G. Belabaev, I. N. Kiseleva, V. V.
Obuchovskii, S. G. Odoulov, and R. A. Taratuta, "New parametric holographic
type scattering of light in lithium tantalate crystals," Sov. Phys. Solid
State 28, 321–322 (1986).

Similar linear effects are also known in other
photosensitive materials; see, e.g., J. M. Moran and I. P. Kaminov,
"Properties of holographical gratings photoinduced in PMMA," Appl. Opt. 12,
1964 (1973); M. R. B. Forshaw, "Explanation of the two-ring diffraction
phenomenon observed by Moran and Kaminov," Appl. Opt. 13, 2
(1974).

K. G. Belabaev, I. N. Kiseleva, V. V.
Obuchovskii, S. G. Odoulov, and R. A. Taratuta, "New parametric holographic
type scattering of light in lithium tantalate crystals," Sov. Phys. Solid
State 28, 321–322 (1986).

R. A. Rupp and F. W. Dress, "Light-induced
scattering in photorefractive crystals," Appl. Phys. B 39, 223–229
(1986).

M. D. Ewbank, P. Yeh, and J. Feinberg,
"Photorefractive conical diffraction in BaTiO_{3}," Opt. Commun. 59,
423–428 (1986).

M. D. Ewbank, P. Yeh, and J. Feinberg,
"Photorefractive conical diffraction in BaTiO_{3}," Opt. Commun. 59,
423–428 (1986).

B. I. Sturman and V. M. Fridkin, The Photovoltaic
and Photorefractive Effects in Noncentrosymmetric Materials (Gordon &
Breach, New York, 1992).

S. R. Montgomery, M. P. Gallagher, G. J. Salamo,
E. J. Sharp, G. L. Wood, and R. R. Neurgaonkar, "Cooperative photorefractive
beam fanning in BaSrKNaNb_{5}O_{15}," J. Opt. Soc. Am B. 11,
1694–1699 (1994).

M. Goulkov, G. Jäkel, E. Krätzig, S. Odoulov, and
R. Schulz, "Influence of different impurities on light-induced scattering in
doped LiNbO_{3}/sub> crystals," Opt. Mater. 4, 314–317
(1995).

B. Sturman, M. Goulkov, and S. Odoulov,
"Polarizatio-degenerate parametric light scattering in photorefractive
crystals," Appl. Phys. B 56, 193–199 (1993).

M. Goulkov, S. Odoulov, U. van Olfen, and E.
Krätzig, "A new light-induced scattering process in photorefractive
BaTiO_{3}," Phys. Stat. Sol. (B) 172, K37–K40
(1992).

M. Yu. Goulkov, S. G. Odoulov, B. I. Sturman,
"Polarization-anisotropic scattering lines in LiNbO_{3}," Appl.
Phys. B 56, 223–228 (1993).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Parametric conical scattering of two orthogonally polarized waves
in BaTiO_{3}," J. Opt. Soc. Am. B 9, 1648–1653
(1992).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Nonlinear scattering in BaTiO_{3}/sub> induced by two
orthogonally polarized waves," Appl. Phys. B 52, 317–322
(1991).

A. V. Ilenkov, S. G. Odoulov, M. S. Soskin, and
M. V. Vasnetsov, "Phase-matched light-induced scattering, mirrorless
self-generation, and oscillation of nearly retropropagating waves in
LiNbO_{3}:Fe in 'forbidden' interaction geometry," Appl. Phys. B
55, 509–512 (1992).

M. Goulkov, G. Jäkel, E. Krätzig, S. Odoulov, and
R. Schulz, "Influence of different impurities on light-induced scattering in
doped LiNbO_{3}/sub> crystals," Opt. Mater. 4, 314–317
(1995).

Similar linear effects are also known in other
photosensitive materials; see, e.g., J. M. Moran and I. P. Kaminov,
"Properties of holographical gratings photoinduced in PMMA," Appl. Opt. 12,
1964 (1973); M. R. B. Forshaw, "Explanation of the two-ring diffraction
phenomenon observed by Moran and Kaminov," Appl. Opt. 13, 2
(1974).

I. F. Kanaev and V. K. Malinovskii, "Mechanism of
light scattering in photorefractive media," Autometrija (Academy of
Sciences, Novosibirsk, 1991), Vol. 4, pp. 37–48.

M. P. Petrov, S. I. Stepanov, and A. V. Khomenko,
Photorefractive Crystals in Coherent Optical Systems, Springer Series in
Optical Sciences (Springer-Verlag, Berlin, 1991).

I. N. Kiseleva, V. V. Obukhovskii, S. G. Odoulov,
and O. I. Oleinik, "Photoinduced light dispersion in crystals with
biharmonic pump," Ukr. Phys. J. 31, 1682–1686 (1986).

K. G. Belabaev, I. N. Kiseleva, V. V.
Obuchovskii, S. G. Odoulov, and R. A. Taratuta, "New parametric holographic
type scattering of light in lithium tantalate crystals," Sov. Phys. Solid
State 28, 321–322 (1986).

I. N. Kiseleva, V. V. Obuchovskii, and S. G.
Odoulov, "Parametric scattering of the holographic type in class 3m
crystals," Sov. Phys. Solid State 28, 1673–1676 (1986).

M. Goulkov, G. Jäkel, E. Krätzig, S. Odoulov, and
R. Schulz, "Influence of different impurities on light-induced scattering in
doped LiNbO_{3}/sub> crystals," Opt. Mater. 4, 314–317
(1995).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Parametric conical scattering of two orthogonally polarized waves
in BaTiO_{3}," J. Opt. Soc. Am. B 9, 1648–1653
(1992).

M. Goulkov, S. Odoulov, U. van Olfen, and E.
Krätzig, "A new light-induced scattering process in photorefractive
BaTiO_{3}," Phys. Stat. Sol. (B) 172, K37–K40
(1992).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Nonlinear scattering in BaTiO_{3}/sub> induced by two
orthogonally polarized waves," Appl. Phys. B 52, 317–322
(1991).

I. F. Kanaev and V. K. Malinovskii, "Mechanism of
light scattering in photorefractive media," Autometrija (Academy of
Sciences, Novosibirsk, 1991), Vol. 4, pp. 37–48.

S. R. Montgomery, M. P. Gallagher, G. J. Salamo,
E. J. Sharp, G. L. Wood, and R. R. Neurgaonkar, "Cooperative photorefractive
beam fanning in BaSrKNaNb_{5}O_{15}," J. Opt. Soc. Am B. 11,
1694–1699 (1994).

Similar linear effects are also known in other
photosensitive materials; see, e.g., J. M. Moran and I. P. Kaminov,
"Properties of holographical gratings photoinduced in PMMA," Appl. Opt. 12,
1964 (1973); M. R. B. Forshaw, "Explanation of the two-ring diffraction
phenomenon observed by Moran and Kaminov," Appl. Opt. 13, 2
(1974).

S. R. Montgomery, M. P. Gallagher, G. J. Salamo,
E. J. Sharp, G. L. Wood, and R. R. Neurgaonkar, "Cooperative photorefractive
beam fanning in BaSrKNaNb_{5}O_{15}," J. Opt. Soc. Am B. 11,
1694–1699 (1994).

I. N. Kiseleva, V. V. Obuchovskii, and S. G.
Odoulov, "Parametric scattering of the holographic type in class 3m
crystals," Sov. Phys. Solid State 28, 1673–1676 (1986).

K. G. Belabaev, I. N. Kiseleva, V. V.
Obuchovskii, S. G. Odoulov, and R. A. Taratuta, "New parametric holographic
type scattering of light in lithium tantalate crystals," Sov. Phys. Solid
State 28, 321–322 (1986).

I. N. Kiseleva, V. V. Obukhovskii, S. G. Odoulov,
and O. I. Oleinik, "Photoinduced light dispersion in crystals with
biharmonic pump," Ukr. Phys. J. 31, 1682–1686 (1986).

M. Goulkov, G. Jäkel, E. Krätzig, S. Odoulov, and
R. Schulz, "Influence of different impurities on light-induced scattering in
doped LiNbO_{3}/sub> crystals," Opt. Mater. 4, 314–317
(1995).

B. Sturman, M. Goulkov, and S. Odoulov,
"Polarizatio-degenerate parametric light scattering in photorefractive
crystals," Appl. Phys. B 56, 193–199 (1993).

M. Goulkov, S. Odoulov, U. van Olfen, and E.
Krätzig, "A new light-induced scattering process in photorefractive
BaTiO_{3}," Phys. Stat. Sol. (B) 172, K37–K40
(1992).

A. Novikov, S. Odoulov, R. Jungen, and T.
Tschudi, "Spatial subharmonic generation in BaTiO_{3}," J. Opt. Soc.
Am. B 9, 1654–1660 (1992).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Parametric conical scattering of two orthogonally polarized waves
in BaTiO_{3}," J. Opt. Soc. Am. B 9, 1648–1653
(1992).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Nonlinear scattering in BaTiO_{3}/sub> induced by two
orthogonally polarized waves," Appl. Phys. B 52, 317–322
(1991).

S. Odoulov, "Anisotropic scattering in
photorefractive crystals: comment," J. Opt. Soc. Am. B 4, 1333–1334
(1987).

S. Odoulov, K. Belabaev, and I. Kiseleva,
"Degenerate stimulated parametric scattering in LiTaO_{3}," Opt.
Lett. 10, 31–33 (1985).

M. Yu. Goulkov, S. G. Odoulov, B. I. Sturman,
"Polarization-anisotropic scattering lines in LiNbO_{3}," Appl.
Phys. B 56, 223–228 (1993).

A. V. Ilenkov, S. G. Odoulov, M. S. Soskin, and
M. V. Vasnetsov, "Phase-matched light-induced scattering, mirrorless
self-generation, and oscillation of nearly retropropagating waves in
LiNbO_{3}:Fe in 'forbidden' interaction geometry," Appl. Phys. B
55, 509–512 (1992).

I. N. Kiseleva, V. V. Obuchovskii, and S. G.
Odoulov, "Parametric scattering of the holographic type in class 3m
crystals," Sov. Phys. Solid State 28, 1673–1676 (1986).

I. N. Kiseleva, V. V. Obukhovskii, S. G. Odoulov,
and O. I. Oleinik, "Photoinduced light dispersion in crystals with
biharmonic pump," Ukr. Phys. J. 31, 1682–1686 (1986).

K. G. Belabaev, I. N. Kiseleva, V. V.
Obuchovskii, S. G. Odoulov, and R. A. Taratuta, "New parametric holographic
type scattering of light in lithium tantalate crystals," Sov. Phys. Solid
State 28, 321–322 (1986).

S. G. Odulov and B. I. Sturman, "Parametric
polarization scattering of light in photorefractive BaTiO_{3}," Sov.
Phys. JETP 75, 241–249 (1992).

I. N. Kiseleva, V. V. Obukhovskii, S. G. Odoulov,
and O. I. Oleinik, "Photoinduced light dispersion in crystals with
biharmonic pump," Ukr. Phys. J. 31, 1682–1686 (1986).

M. Goulkov, S. Odoulov, U. van Olfen, and E.
Krätzig, "A new light-induced scattering process in photorefractive
BaTiO_{3}," Phys. Stat. Sol. (B) 172, K37–K40
(1992).

M. P. Petrov, S. I. Stepanov, and A. V. Khomenko,
Photorefractive Crystals in Coherent Optical Systems, Springer Series in
Optical Sciences (Springer-Verlag, Berlin, 1991).

R. A. Rupp and F. W. Dress, "Light-induced
scattering in photorefractive crystals," Appl. Phys. B 39, 223–229
(1986).

S. R. Montgomery, M. P. Gallagher, G. J. Salamo,
E. J. Sharp, G. L. Wood, and R. R. Neurgaonkar, "Cooperative photorefractive
beam fanning in BaSrKNaNb_{5}O_{15}," J. Opt. Soc. Am B. 11,
1694–1699 (1994).

M. Goulkov, G. Jäkel, E. Krätzig, S. Odoulov, and
R. Schulz, "Influence of different impurities on light-induced scattering in
doped LiNbO_{3}/sub> crystals," Opt. Mater. 4, 314–317
(1995).

S. R. Montgomery, M. P. Gallagher, G. J. Salamo,
E. J. Sharp, G. L. Wood, and R. R. Neurgaonkar, "Cooperative photorefractive
beam fanning in BaSrKNaNb_{5}O_{15}," J. Opt. Soc. Am B. 11,
1694–1699 (1994).

A. V. Ilenkov, S. G. Odoulov, M. S. Soskin, and
M. V. Vasnetsov, "Phase-matched light-induced scattering, mirrorless
self-generation, and oscillation of nearly retropropagating waves in
LiNbO_{3}:Fe in 'forbidden' interaction geometry," Appl. Phys. B
55, 509–512 (1992).

M. P. Petrov, S. I. Stepanov, and A. V. Khomenko,
Photorefractive Crystals in Coherent Optical Systems, Springer Series in
Optical Sciences (Springer-Verlag, Berlin, 1991).

B. Sturman, M. Goulkov, and S. Odoulov,
"Polarizatio-degenerate parametric light scattering in photorefractive
crystals," Appl. Phys. B 56, 193–199 (1993).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Parametric conical scattering of two orthogonally polarized waves
in BaTiO_{3}," J. Opt. Soc. Am. B 9, 1648–1653
(1992).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Nonlinear scattering in BaTiO_{3}/sub> induced by two
orthogonally polarized waves," Appl. Phys. B 52, 317–322
(1991).

M. Yu. Goulkov, S. G. Odoulov, B. I. Sturman,
"Polarization-anisotropic scattering lines in LiNbO_{3}," Appl.
Phys. B 56, 223–228 (1993).

S. G. Odulov and B. I. Sturman, "Parametric
polarization scattering of light in photorefractive BaTiO_{3}," Sov.
Phys. JETP 75, 241–249 (1992).

B. I. Sturman and V. M. Fridkin, The Photovoltaic
and Photorefractive Effects in Noncentrosymmetric Materials (Gordon &
Breach, New York, 1992).

K. G. Belabaev, I. N. Kiseleva, V. V.
Obuchovskii, S. G. Odoulov, and R. A. Taratuta, "New parametric holographic
type scattering of light in lithium tantalate crystals," Sov. Phys. Solid
State 28, 321–322 (1986).

A. V. Ilenkov, S. G. Odoulov, M. S. Soskin, and
M. V. Vasnetsov, "Phase-matched light-induced scattering, mirrorless
self-generation, and oscillation of nearly retropropagating waves in
LiNbO_{3}:Fe in 'forbidden' interaction geometry," Appl. Phys. B
55, 509–512 (1992).

S. R. Montgomery, M. P. Gallagher, G. J. Salamo,
E. J. Sharp, G. L. Wood, and R. R. Neurgaonkar, "Cooperative photorefractive
beam fanning in BaSrKNaNb_{5}O_{15}," J. Opt. Soc. Am B. 11,
1694–1699 (1994).

M. D. Ewbank, P. Yeh, and J. Feinberg,
"Photorefractive conical diffraction in BaTiO_{3}," Opt. Commun. 59,
423–428 (1986).

R. A. Rupp and F. W. Dress, "Light-induced
scattering in photorefractive crystals," Appl. Phys. B 39, 223–229
(1986).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Nonlinear scattering in BaTiO_{3}/sub> induced by two
orthogonally polarized waves," Appl. Phys. B 52, 317–322
(1991).

B. Sturman, M. Goulkov, and S. Odoulov,
"Polarizatio-degenerate parametric light scattering in photorefractive
crystals," Appl. Phys. B 56, 193–199 (1993).

M. Yu. Goulkov, S. G. Odoulov, B. I. Sturman,
"Polarization-anisotropic scattering lines in LiNbO_{3}," Appl.
Phys. B 56, 223–228 (1993).

A. V. Ilenkov, S. G. Odoulov, M. S. Soskin, and
M. V. Vasnetsov, "Phase-matched light-induced scattering, mirrorless
self-generation, and oscillation of nearly retropropagating waves in
LiNbO_{3}:Fe in 'forbidden' interaction geometry," Appl. Phys. B
55, 509–512 (1992).

S. R. Montgomery, M. P. Gallagher, G. J. Salamo,
E. J. Sharp, G. L. Wood, and R. R. Neurgaonkar, "Cooperative photorefractive
beam fanning in BaSrKNaNb_{5}O_{15}," J. Opt. Soc. Am B. 11,
1694–1699 (1994).

S. Odoulov, B. Sturman, L. Holtmann, and E.
Krätzig, "Parametric conical scattering of two orthogonally polarized waves
in BaTiO_{3}," J. Opt. Soc. Am. B 9, 1648–1653
(1992).

D. A. Temple and C. Warde, "Anisotropic
scattering in photorefractive crystals," J. Opt. Soc. Am. B 3, 337–341
(1986).

G. Zhang, Q. X. Li, P. P. Ho, and R. R. Alfano,
"Degenerate stimulated parametric scattering in LiTaO_{3}:Fe," J.
Opt. Soc. Am. B 4, 882–885 (1987).

S. Odoulov, "Anisotropic scattering in
photorefractive crystals: comment," J. Opt. Soc. Am. B 4, 1333–1334
(1987).

A. Novikov, S. Odoulov, R. Jungen, and T.
Tschudi, "Spatial subharmonic generation in BaTiO_{3}," J. Opt. Soc.
Am. B 9, 1654–1660 (1992).

K. Nakagava and T. Minemoto, "Conical diffraction
induced by two extraordinary waves," J. Opt. Soc. Am. B 11, 1639–1643
(1994).

M. D. Ewbank, P. Yeh, and J. Feinberg,
"Photorefractive conical diffraction in BaTiO_{3}," Opt. Commun. 59,
423–428 (1986).

M. Goulkov, G. Jäkel, E. Krätzig, S. Odoulov, and
R. Schulz, "Influence of different impurities on light-induced scattering in
doped LiNbO_{3}/sub> crystals," Opt. Mater. 4, 314–317
(1995).

M. Goulkov, S. Odoulov, U. van Olfen, and E.
Krätzig, "A new light-induced scattering process in photorefractive
BaTiO_{3}," Phys. Stat. Sol. (B) 172, K37–K40
(1992).

S. G. Odulov and B. I. Sturman, "Parametric
polarization scattering of light in photorefractive BaTiO_{3}," Sov.
Phys. JETP 75, 241–249 (1992).

I. N. Kiseleva, V. V. Obuchovskii, and S. G.
Odoulov, "Parametric scattering of the holographic type in class 3m
crystals," Sov. Phys. Solid State 28, 1673–1676 (1986).

K. G. Belabaev, I. N. Kiseleva, V. V.
Obuchovskii, S. G. Odoulov, and R. A. Taratuta, "New parametric holographic
type scattering of light in lithium tantalate crystals," Sov. Phys. Solid
State 28, 321–322 (1986).

I. N. Kiseleva, V. V. Obukhovskii, S. G. Odoulov,
and O. I. Oleinik, "Photoinduced light dispersion in crystals with
biharmonic pump," Ukr. Phys. J. 31, 1682–1686 (1986).

Similar linear effects are also known in other
photosensitive materials; see, e.g., J. M. Moran and I. P. Kaminov,
"Properties of holographical gratings photoinduced in PMMA," Appl. Opt. 12,
1964 (1973); M. R. B. Forshaw, "Explanation of the two-ring diffraction
phenomenon observed by Moran and Kaminov," Appl. Opt. 13, 2
(1974).

It dominates when the pump waves propagate in the
plane normal to the polar axis; see, e.g., Ref. 14.

In spite of a large body of convincing evidence
of a one-to-one correspondence between the light rings and lines and the
phase-matching conditions, some authors still try to connect these light
singularities with hypothetical anisotropic scattering centers; see Ref.
19.

B. I. Sturman and V. M. Fridkin, The Photovoltaic
and Photorefractive Effects in Noncentrosymmetric Materials (Gordon &
Breach, New York, 1992).

P. Günter and J.-P. Huignard, eds.,
Photorefractive Materials and Their Applications I and II, Vols. 61 and 62
of Topics in Applied Physics (Springer-Verlag, Berlin, 1988 and
1989).

M. P. Petrov, S. I. Stepanov, and A. V. Khomenko,
Photorefractive Crystals in Coherent Optical Systems, Springer Series in
Optical Sciences (Springer-Verlag, Berlin, 1991).

I. F. Kanaev and V. K. Malinovskii, "Mechanism of
light scattering in photorefractive media," Autometrija (Academy of
Sciences, Novosibirsk, 1991), Vol. 4, pp. 37–48.