Abstract

We present experimental evidence for coherent, directional emission from a random gain medium above the threshold for laserlike emission. In particular, we report the first observation (to our knowledge) of a coherent angular backscattering peak above this threshold. A plausible explanation of our findings follows from the assumption that superfluorescent emission occurs in the gain medium above threshold.

© 2000 Optical Society of America

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References

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  1. N. M. Lawandy, R. M. Balachandran, A. M. L. Gomes, E. Sauvain, “Laser action in strongly scattering media,” Nature (London) 368, 436–438 (1994).
    [CrossRef]
  2. W. L. Sha, C.-H. Liu, R. R. Alfano, “Spectral and temporal measurements of laser action of Rhodamine 640 dye in strongly scattering media,” Opt. Lett. 23, 1922–1924 (1994).
    [CrossRef]
  3. D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
    [CrossRef]
  4. M. A. Noginov, H. J. Caulfield, N. E. Noginova, P. Venkateswarlu, “Line narrowing in the dye solution with scattering centers,” Opt. Commun. 118, 430–437 (1997).
    [CrossRef]
  5. R. M. Balachandran, N. M. Lawandy, “Interface reflection effects in photonic paint,” Opt. Lett. 11, 1271–1273 (1995).
    [CrossRef]
  6. M. Siddique, R. R. Alfano, G. A. Burger, M. Kempe, A. Z. Zenack, “Time-resolved studies of stimulated emission from colloidal dye solutions,” Opt. Lett. 21, 450–452 (1996).
    [CrossRef] [PubMed]
  7. R. M. Balachrandan, N. N. Lawandy, J. A. Moon, “Theory of laser action in scattering gain media,” Opt. Lett. 22, 319–321 (1997).
    [CrossRef]
  8. P. E. Wolf, G. Maret, A. Akkermans, R. Maynard, “Optical coherent backscattering by random media: an experimental study,” J. Phys. (Paris) 49, 63–75 (1988).
    [CrossRef]
  9. D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Coherent backscattering of light from amplifying random media,” Phys. Rev. Lett. 75, 1739–1742 (1995).
    [CrossRef] [PubMed]
  10. P. C. de Oliveira, A. E. Perkins, N. M. Lawandy, “Coherent backscattering from high-gain scattering media,” Opt. Lett. 21, 1685–1687 (1996).
    [CrossRef] [PubMed]
  11. A. Yu. Zyuzin, “Weak localization in backscattering from an amplifying medium,” Europhys. Lett. 26, 517–520 (1994).
    [CrossRef]
  12. H. C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981).
  13. R. G. Pinnick, G. L. Fernandez, J. G. Xie, T. Ruekgauer, J. Gu, R. L. Armstrong, “Stimulated Raman scattering and lasing in micrometer-sized cylindrical liquid jets: time and spectral dependence,” J. Opt. Soc. Am. B 9, 865–870 (1992).
    [CrossRef]
  14. A. Yu. Zyuzin, “Superfluorescence of photonic paint,” JETP 86, 445–449 (1998).
    [CrossRef]
  15. D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Random laser?” Nature (London) 373, 203–204 (1995).
    [CrossRef]
  16. J. P. Hermann, J. C. MacGillivray, N. Skribanowitz, M. S. Feld, “Self-induced emission in optically pumped HF gas: the rise and fall of the superradiant state,” in Laser Spectroscopy, R. G. Brewer, A. Mooradian, eds. (Plenum, New York, 1974), p. 379.
    [CrossRef]
  17. N. Skribanowitz, J. P. Hermann, J. C. MacGillivray, M. S. Feld, “Observation of Dicke Superradiance in optically pumped HF Gas,” Phys. Rev. Lett. 30, 309–312 (1973).
    [CrossRef]
  18. M. F. H. Schuurmans, Q. H. F. Vrehen, D. Polder, Superfluorescence, Vol. 17 of Advances in Atomic and Molecular Physics (Academic, New York, 1981), pp. 167–228.
  19. Q. H. F. Vrehen, H. M. Gibbs, “Superfluorescence experiments,” in Dissipative Systems in Quantum Optics, R. Bonifacio, ed. (Springer, New York, 1982), pp. 111–147.
    [CrossRef]
  20. N. E. Rehler, J. Eberly, “Superradiance,” Phys. Rev. A 3, 1735–1751 (1970).
    [CrossRef]
  21. V. P. Klochkov, E. B. Verkhovskii, “Cooperative emission of Rhodamine 6G molecules in a liquid solution,” Opt. Spectrosc. 85, 390–395 (1998).
  22. J. E. Selwyn, J. I. Steinfeld, “Aggregation equilibria of xanthene dyes,” J. Phys. Chem. 76, 762–774 (1972).
    [CrossRef]

1998 (2)

A. Yu. Zyuzin, “Superfluorescence of photonic paint,” JETP 86, 445–449 (1998).
[CrossRef]

V. P. Klochkov, E. B. Verkhovskii, “Cooperative emission of Rhodamine 6G molecules in a liquid solution,” Opt. Spectrosc. 85, 390–395 (1998).

1997 (2)

M. A. Noginov, H. J. Caulfield, N. E. Noginova, P. Venkateswarlu, “Line narrowing in the dye solution with scattering centers,” Opt. Commun. 118, 430–437 (1997).
[CrossRef]

R. M. Balachrandan, N. N. Lawandy, J. A. Moon, “Theory of laser action in scattering gain media,” Opt. Lett. 22, 319–321 (1997).
[CrossRef]

1996 (2)

1995 (4)

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Random laser?” Nature (London) 373, 203–204 (1995).
[CrossRef]

D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
[CrossRef]

R. M. Balachandran, N. M. Lawandy, “Interface reflection effects in photonic paint,” Opt. Lett. 11, 1271–1273 (1995).
[CrossRef]

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Coherent backscattering of light from amplifying random media,” Phys. Rev. Lett. 75, 1739–1742 (1995).
[CrossRef] [PubMed]

1994 (3)

N. M. Lawandy, R. M. Balachandran, A. M. L. Gomes, E. Sauvain, “Laser action in strongly scattering media,” Nature (London) 368, 436–438 (1994).
[CrossRef]

W. L. Sha, C.-H. Liu, R. R. Alfano, “Spectral and temporal measurements of laser action of Rhodamine 640 dye in strongly scattering media,” Opt. Lett. 23, 1922–1924 (1994).
[CrossRef]

A. Yu. Zyuzin, “Weak localization in backscattering from an amplifying medium,” Europhys. Lett. 26, 517–520 (1994).
[CrossRef]

1992 (1)

1988 (1)

P. E. Wolf, G. Maret, A. Akkermans, R. Maynard, “Optical coherent backscattering by random media: an experimental study,” J. Phys. (Paris) 49, 63–75 (1988).
[CrossRef]

1973 (1)

N. Skribanowitz, J. P. Hermann, J. C. MacGillivray, M. S. Feld, “Observation of Dicke Superradiance in optically pumped HF Gas,” Phys. Rev. Lett. 30, 309–312 (1973).
[CrossRef]

1972 (1)

J. E. Selwyn, J. I. Steinfeld, “Aggregation equilibria of xanthene dyes,” J. Phys. Chem. 76, 762–774 (1972).
[CrossRef]

1970 (1)

N. E. Rehler, J. Eberly, “Superradiance,” Phys. Rev. A 3, 1735–1751 (1970).
[CrossRef]

Akkermans, A.

P. E. Wolf, G. Maret, A. Akkermans, R. Maynard, “Optical coherent backscattering by random media: an experimental study,” J. Phys. (Paris) 49, 63–75 (1988).
[CrossRef]

Alfano, R. R.

M. Siddique, R. R. Alfano, G. A. Burger, M. Kempe, A. Z. Zenack, “Time-resolved studies of stimulated emission from colloidal dye solutions,” Opt. Lett. 21, 450–452 (1996).
[CrossRef] [PubMed]

W. L. Sha, C.-H. Liu, R. R. Alfano, “Spectral and temporal measurements of laser action of Rhodamine 640 dye in strongly scattering media,” Opt. Lett. 23, 1922–1924 (1994).
[CrossRef]

Armstrong, R. L.

Balachandran, R. M.

R. M. Balachandran, N. M. Lawandy, “Interface reflection effects in photonic paint,” Opt. Lett. 11, 1271–1273 (1995).
[CrossRef]

N. M. Lawandy, R. M. Balachandran, A. M. L. Gomes, E. Sauvain, “Laser action in strongly scattering media,” Nature (London) 368, 436–438 (1994).
[CrossRef]

Balachrandan, R. M.

Burger, G. A.

Caulfield, H. J.

M. A. Noginov, H. J. Caulfield, N. E. Noginova, P. Venkateswarlu, “Line narrowing in the dye solution with scattering centers,” Opt. Commun. 118, 430–437 (1997).
[CrossRef]

Cheng, B.

D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
[CrossRef]

de Oliveira, P. C.

Eberly, J.

N. E. Rehler, J. Eberly, “Superradiance,” Phys. Rev. A 3, 1735–1751 (1970).
[CrossRef]

Feld, M. S.

N. Skribanowitz, J. P. Hermann, J. C. MacGillivray, M. S. Feld, “Observation of Dicke Superradiance in optically pumped HF Gas,” Phys. Rev. Lett. 30, 309–312 (1973).
[CrossRef]

J. P. Hermann, J. C. MacGillivray, N. Skribanowitz, M. S. Feld, “Self-induced emission in optically pumped HF gas: the rise and fall of the superradiant state,” in Laser Spectroscopy, R. G. Brewer, A. Mooradian, eds. (Plenum, New York, 1974), p. 379.
[CrossRef]

Fernandez, G. L.

Gibbs, H. M.

Q. H. F. Vrehen, H. M. Gibbs, “Superfluorescence experiments,” in Dissipative Systems in Quantum Optics, R. Bonifacio, ed. (Springer, New York, 1982), pp. 111–147.
[CrossRef]

Gomes, A. M. L.

N. M. Lawandy, R. M. Balachandran, A. M. L. Gomes, E. Sauvain, “Laser action in strongly scattering media,” Nature (London) 368, 436–438 (1994).
[CrossRef]

Gu, J.

Hermann, J. P.

N. Skribanowitz, J. P. Hermann, J. C. MacGillivray, M. S. Feld, “Observation of Dicke Superradiance in optically pumped HF Gas,” Phys. Rev. Lett. 30, 309–312 (1973).
[CrossRef]

J. P. Hermann, J. C. MacGillivray, N. Skribanowitz, M. S. Feld, “Self-induced emission in optically pumped HF gas: the rise and fall of the superradiant state,” in Laser Spectroscopy, R. G. Brewer, A. Mooradian, eds. (Plenum, New York, 1974), p. 379.
[CrossRef]

Hu, W.

D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
[CrossRef]

Kempe, M.

Klochkov, V. P.

V. P. Klochkov, E. B. Verkhovskii, “Cooperative emission of Rhodamine 6G molecules in a liquid solution,” Opt. Spectrosc. 85, 390–395 (1998).

Lagendijk, A.

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Random laser?” Nature (London) 373, 203–204 (1995).
[CrossRef]

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Coherent backscattering of light from amplifying random media,” Phys. Rev. Lett. 75, 1739–1742 (1995).
[CrossRef] [PubMed]

Lawandy, N. M.

P. C. de Oliveira, A. E. Perkins, N. M. Lawandy, “Coherent backscattering from high-gain scattering media,” Opt. Lett. 21, 1685–1687 (1996).
[CrossRef] [PubMed]

R. M. Balachandran, N. M. Lawandy, “Interface reflection effects in photonic paint,” Opt. Lett. 11, 1271–1273 (1995).
[CrossRef]

N. M. Lawandy, R. M. Balachandran, A. M. L. Gomes, E. Sauvain, “Laser action in strongly scattering media,” Nature (London) 368, 436–438 (1994).
[CrossRef]

Lawandy, N. N.

Li, Z.

D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
[CrossRef]

Liu, C.-H.

W. L. Sha, C.-H. Liu, R. R. Alfano, “Spectral and temporal measurements of laser action of Rhodamine 640 dye in strongly scattering media,” Opt. Lett. 23, 1922–1924 (1994).
[CrossRef]

MacGillivray, J. C.

N. Skribanowitz, J. P. Hermann, J. C. MacGillivray, M. S. Feld, “Observation of Dicke Superradiance in optically pumped HF Gas,” Phys. Rev. Lett. 30, 309–312 (1973).
[CrossRef]

J. P. Hermann, J. C. MacGillivray, N. Skribanowitz, M. S. Feld, “Self-induced emission in optically pumped HF gas: the rise and fall of the superradiant state,” in Laser Spectroscopy, R. G. Brewer, A. Mooradian, eds. (Plenum, New York, 1974), p. 379.
[CrossRef]

Maret, G.

P. E. Wolf, G. Maret, A. Akkermans, R. Maynard, “Optical coherent backscattering by random media: an experimental study,” J. Phys. (Paris) 49, 63–75 (1988).
[CrossRef]

Maynard, R.

P. E. Wolf, G. Maret, A. Akkermans, R. Maynard, “Optical coherent backscattering by random media: an experimental study,” J. Phys. (Paris) 49, 63–75 (1988).
[CrossRef]

Moon, J. A.

Noginov, M. A.

M. A. Noginov, H. J. Caulfield, N. E. Noginova, P. Venkateswarlu, “Line narrowing in the dye solution with scattering centers,” Opt. Commun. 118, 430–437 (1997).
[CrossRef]

Noginova, N. E.

M. A. Noginov, H. J. Caulfield, N. E. Noginova, P. Venkateswarlu, “Line narrowing in the dye solution with scattering centers,” Opt. Commun. 118, 430–437 (1997).
[CrossRef]

Perkins, A. E.

Pinnick, R. G.

Polder, D.

M. F. H. Schuurmans, Q. H. F. Vrehen, D. Polder, Superfluorescence, Vol. 17 of Advances in Atomic and Molecular Physics (Academic, New York, 1981), pp. 167–228.

Rehler, N. E.

N. E. Rehler, J. Eberly, “Superradiance,” Phys. Rev. A 3, 1735–1751 (1970).
[CrossRef]

Ruekgauer, T.

Sauvain, E.

N. M. Lawandy, R. M. Balachandran, A. M. L. Gomes, E. Sauvain, “Laser action in strongly scattering media,” Nature (London) 368, 436–438 (1994).
[CrossRef]

Schuurmans, M. F. H.

M. F. H. Schuurmans, Q. H. F. Vrehen, D. Polder, Superfluorescence, Vol. 17 of Advances in Atomic and Molecular Physics (Academic, New York, 1981), pp. 167–228.

Selwyn, J. E.

J. E. Selwyn, J. I. Steinfeld, “Aggregation equilibria of xanthene dyes,” J. Phys. Chem. 76, 762–774 (1972).
[CrossRef]

Sha, W. L.

W. L. Sha, C.-H. Liu, R. R. Alfano, “Spectral and temporal measurements of laser action of Rhodamine 640 dye in strongly scattering media,” Opt. Lett. 23, 1922–1924 (1994).
[CrossRef]

Siddique, M.

Skribanowitz, N.

N. Skribanowitz, J. P. Hermann, J. C. MacGillivray, M. S. Feld, “Observation of Dicke Superradiance in optically pumped HF Gas,” Phys. Rev. Lett. 30, 309–312 (1973).
[CrossRef]

J. P. Hermann, J. C. MacGillivray, N. Skribanowitz, M. S. Feld, “Self-induced emission in optically pumped HF gas: the rise and fall of the superradiant state,” in Laser Spectroscopy, R. G. Brewer, A. Mooradian, eds. (Plenum, New York, 1974), p. 379.
[CrossRef]

Steinfeld, J. I.

J. E. Selwyn, J. I. Steinfeld, “Aggregation equilibria of xanthene dyes,” J. Phys. Chem. 76, 762–774 (1972).
[CrossRef]

van Albada, M. P.

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Random laser?” Nature (London) 373, 203–204 (1995).
[CrossRef]

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Coherent backscattering of light from amplifying random media,” Phys. Rev. Lett. 75, 1739–1742 (1995).
[CrossRef] [PubMed]

van de Hulst, H. C.

H. C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981).

Venkateswarlu, P.

M. A. Noginov, H. J. Caulfield, N. E. Noginova, P. Venkateswarlu, “Line narrowing in the dye solution with scattering centers,” Opt. Commun. 118, 430–437 (1997).
[CrossRef]

Verkhovskii, E. B.

V. P. Klochkov, E. B. Verkhovskii, “Cooperative emission of Rhodamine 6G molecules in a liquid solution,” Opt. Spectrosc. 85, 390–395 (1998).

Vrehen, Q. H. F.

M. F. H. Schuurmans, Q. H. F. Vrehen, D. Polder, Superfluorescence, Vol. 17 of Advances in Atomic and Molecular Physics (Academic, New York, 1981), pp. 167–228.

Q. H. F. Vrehen, H. M. Gibbs, “Superfluorescence experiments,” in Dissipative Systems in Quantum Optics, R. Bonifacio, ed. (Springer, New York, 1982), pp. 111–147.
[CrossRef]

Wiersma, D. S.

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Random laser?” Nature (London) 373, 203–204 (1995).
[CrossRef]

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Coherent backscattering of light from amplifying random media,” Phys. Rev. Lett. 75, 1739–1742 (1995).
[CrossRef] [PubMed]

Wolf, P. E.

P. E. Wolf, G. Maret, A. Akkermans, R. Maynard, “Optical coherent backscattering by random media: an experimental study,” J. Phys. (Paris) 49, 63–75 (1988).
[CrossRef]

Xie, J. G.

Yang, J.

D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
[CrossRef]

Zenack, A. Z.

Zhang, D.

D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
[CrossRef]

Zhang, Y.

D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
[CrossRef]

Zyuzin, A. Yu.

A. Yu. Zyuzin, “Superfluorescence of photonic paint,” JETP 86, 445–449 (1998).
[CrossRef]

A. Yu. Zyuzin, “Weak localization in backscattering from an amplifying medium,” Europhys. Lett. 26, 517–520 (1994).
[CrossRef]

Europhys. Lett. (1)

A. Yu. Zyuzin, “Weak localization in backscattering from an amplifying medium,” Europhys. Lett. 26, 517–520 (1994).
[CrossRef]

J. Opt. Soc. Am. B (1)

J. Phys. (Paris) (1)

P. E. Wolf, G. Maret, A. Akkermans, R. Maynard, “Optical coherent backscattering by random media: an experimental study,” J. Phys. (Paris) 49, 63–75 (1988).
[CrossRef]

J. Phys. Chem. (1)

J. E. Selwyn, J. I. Steinfeld, “Aggregation equilibria of xanthene dyes,” J. Phys. Chem. 76, 762–774 (1972).
[CrossRef]

JETP (1)

A. Yu. Zyuzin, “Superfluorescence of photonic paint,” JETP 86, 445–449 (1998).
[CrossRef]

Nature (London) (2)

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Random laser?” Nature (London) 373, 203–204 (1995).
[CrossRef]

N. M. Lawandy, R. M. Balachandran, A. M. L. Gomes, E. Sauvain, “Laser action in strongly scattering media,” Nature (London) 368, 436–438 (1994).
[CrossRef]

Opt. Commun. (2)

D. Zhang, B. Cheng, J. Yang, Y. Zhang, W. Hu, Z. Li, “Narrow-bandwidth emission from a suspension of dye and scatterers,” Opt. Commun. 118, 462–465 (1995).
[CrossRef]

M. A. Noginov, H. J. Caulfield, N. E. Noginova, P. Venkateswarlu, “Line narrowing in the dye solution with scattering centers,” Opt. Commun. 118, 430–437 (1997).
[CrossRef]

Opt. Lett. (5)

Opt. Spectrosc. (1)

V. P. Klochkov, E. B. Verkhovskii, “Cooperative emission of Rhodamine 6G molecules in a liquid solution,” Opt. Spectrosc. 85, 390–395 (1998).

Phys. Rev. A (1)

N. E. Rehler, J. Eberly, “Superradiance,” Phys. Rev. A 3, 1735–1751 (1970).
[CrossRef]

Phys. Rev. Lett. (2)

D. S. Wiersma, M. P. van Albada, A. Lagendijk, “Coherent backscattering of light from amplifying random media,” Phys. Rev. Lett. 75, 1739–1742 (1995).
[CrossRef] [PubMed]

N. Skribanowitz, J. P. Hermann, J. C. MacGillivray, M. S. Feld, “Observation of Dicke Superradiance in optically pumped HF Gas,” Phys. Rev. Lett. 30, 309–312 (1973).
[CrossRef]

Other (4)

M. F. H. Schuurmans, Q. H. F. Vrehen, D. Polder, Superfluorescence, Vol. 17 of Advances in Atomic and Molecular Physics (Academic, New York, 1981), pp. 167–228.

Q. H. F. Vrehen, H. M. Gibbs, “Superfluorescence experiments,” in Dissipative Systems in Quantum Optics, R. Bonifacio, ed. (Springer, New York, 1982), pp. 111–147.
[CrossRef]

H. C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981).

J. P. Hermann, J. C. MacGillivray, N. Skribanowitz, M. S. Feld, “Self-induced emission in optically pumped HF gas: the rise and fall of the superradiant state,” in Laser Spectroscopy, R. G. Brewer, A. Mooradian, eds. (Plenum, New York, 1974), p. 379.
[CrossRef]

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Figures (6)

Fig. 1
Fig. 1

Experimental arrangement: SH, sample holder; BS’s, beam splitters; L’s, lenses; LS, pulsed Nd:YAG laser; F, filter; OMA, optical multichannel analyzer; CCD’s, charge-coupled detectors; SP, spectrograph; DG, diffraction grating; AP, aperture. Partial setup on left for angular backscattering measurements, on right for interference and spectral measurements.

Fig. 2
Fig. 2

BP angular spectra of laserlike emission (near 615 nm) of 5 × 10-3 M Rhodamine 640 dye and 2.5 × 1011/cm3 TiO2 scatterers in methanol: solid curves, lower curve below threshold, pump energy of 0.05 mJ, upper curve at threshold, pump energy of 0.08 mJ. Dotted curve, fit to theory of Ref. 11.

Fig. 3
Fig. 3

Same as for Fig. 2, except for a pump energy of 0.66 mJ; curve a, for a neat dye solution above its 0.28-mJ threshold.

Fig. 4
Fig. 4

Elastic backscattering spectra of a He–Ne laser at 632.8 nm: a, for a particle-only solution; b, for a solution of particles plus dye. Dotted curve, a fit to theory of Ref. 8.

Fig. 5
Fig. 5

Coherence and spectral characteristics of the BP for a dye with the particle concentrations of Fig. 1 obtained with a charge-coupled detector above threshold and a pump energy of 1 mJ for a 1-cm-thick sample holder. (a) Interferogram taken with an 11-groove/mm grating; (b) spectrum from a spectrograph with a using low-resolution, 300-groove/mm grating.

Fig. 6
Fig. 6

Coherence and spectral characteristics of the LP for the dye concentration of Fig. 2 (no particles added) obtained with the charge-coupled detector above threshold and a pump energy of 1 mJ. (a) Interferogram with an 11-groove/mm grating and a 1-cm-thick cuvette; (b) spectrum for a 1-mm thick cuvette from a spectrograph with a high-resolution, 1800-groove/mm grating (inset, spectrum near 620 nm for a 1-cm cuvette with a spectrograph with a low-resolution, 300-groove/mm grating).

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