Abstract

Aerosol-induced laser breakdown thresholds have been measured for liquid droplets at wavelengths λ = 1.064, 0.532, 0.355, 0.266 μm using a Nd:YAG laser with 5–10-ns pulse duration. Breakdown thresholds are 2–3 orders of magnitude below those for clean air and range from 4 × 107 to 3 × 109 W cm−2 for nominal 50-μm diam droplets, depending on laser wavelength and droplet composition. Thresholds decrease with decreasing wavelength; they also decrease for droplets having a higher real refractive index. For water droplets the breakdown threshold intensity varies approximately as λ0.5. The wavelength dependence of breakdown thresholds can be qualitatively explained by considering (1) the effect of enhancement of internal fields and energy density within and near droplets and (2) the increasing importance of multiphoton absorption processes at shorter wavelengths. Laser transmission losses through the breakdown plasma and observations of the suppression of stimulated Raman scattering by the addition of small quantitites of absorbing material to water and carbon tetrachloride droplets are also reported.

© 1988 Optical Society of America

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References

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  1. D. E. Lencioni, “The Effect of Dust on 10.6 μm Laser-Induced Air Breakdown,” Appl. Phys. Lett. 23, 12 (1973).
    [CrossRef]
  2. D. C. Smith, R. T. Brown, “Aerosol-Induced Air Breakdown with CO2 Laser Radiation,” J. Appl. Phys. 46, 1146 (1975).
    [CrossRef]
  3. D. E. Lencioni, “Laser-Induced Air Breakdown for 1.06 μm Radiation,” Appl. Phys. Lett. 25, 15 (1974); also D. E. Lencioni, L. C. Pettingill, “The Dynamics of Air Breakdown Initiated by a Particle in a Laser Beam,” J. Appl. Phys. 48, 1848 (1977).
    [CrossRef]
  4. V. K. Mamanov, “Air Breakdown Minimized by Breakdown in Aqueous Aerosol Drops Acted upon by Radiation with Wavelength 1.06 μm,” J. Sov. Laser Res. 5, 249 (1980).
    [CrossRef]
  5. S. V. Zakharchenko, S. M. Kolomiets, A. M. Skripkin, “Breakdown in a Disperse Medium by Laser Radiation,” Sov. Phys. Tech. Phys. 3, 552 (1977).
  6. V. A. Pogodaev, A. E. Rozhdestvenskii, “Initiation of Optical Breakdown by Weakly Absorbing Water Droplets,” Sov. Tech. Phys. Lett. 5, 103 (1979).
  7. V. A. Pogodaev, A. E. Rozhdestvenskii, “Thresholds of Optical Breakdown in Weakly Absorbing Aqueous Aerosol,” in Proceedings, Second All-Union Conference on Propagating Laser Radiation in a Disperse Medium (1982), pp. 123–125.
  8. P. Chў, M. A. Jarzembski, N. Y. Chou, R. G. Pinnick, “Effect of Size and Material of Liquid Spherical Particles on Laser-Induced Breakdown,” Appl. Phys. Lett. 49, 1475 (1986).
    [CrossRef]
  9. P. Chў, M. A. Jarzembski, V. Srivastava, R. G. Pinnick, D. Pendleton, J. Cruncleton, “Effect of Spherical Particles on Laser-Induced Breakdown of Gases,” Appl. Opt. 26, 760 (1987).
    [CrossRef]
  10. J. H. Eickmans, W.-F. Hsieh, R. K. Chang, “Laser-Induced Explosion of Water Droplets: Spatially Resolved Spectra,” Opt. Lett. 12, 22 (1987).
    [CrossRef] [PubMed]
  11. J. F. Owen, R. K. Chang, P. W. Barber, “Morphology Dependent Resonances in Raman Scattering, Flourescence Emission, and Elastic Scattering from Microparticles,” Aerosol Sci. Tech. 1, 293 (1982).
    [CrossRef]
  12. R. Thurn, W. Kiefer, “Observations of Structural Resonances in the Raman Spectra of Optically Levitated Dielectric Microspheres,” J. Raman Spectrosc. 15, 411 (1984).
    [CrossRef]
  13. J. B. Snow, S. Qian, R. K. Chang, “Stimulated Raman Scattering from Individual Water and Ethanol Droplets at Morphology-Dependent Resonances,” Opt. Lett. 10, 37 (1985).
    [CrossRef] [PubMed]
  14. R. Thurn, W. Keifer, “Structural Resonances Observed in the Raman Spectra of Optically Levitated Liquid Droplets,” Appl. Opt. 24, 1515 (1985).
    [CrossRef] [PubMed]
  15. P. Chў, J. D. Pendleton, R. G. Pinnick, “Internal and Near-Surface Scattered Field of a Spherical Particle at Resonant Conditions,” Appl. Opt. 24, 3940 (1985).
    [CrossRef]
  16. S. Qian, R. K. Chang, “Multiple Order Stokes Emissions from Micrometer-size Droplets,” Phys. Rev. Lett. 56, 926 (1986).
    [CrossRef] [PubMed]
  17. S. C. Hill, R. E. Benner, “Morphology Dependent Resonances Associated with Stimulated Processes in Microspheres,” J. Opt. Soc. Am. 3, 1509 (1986).
    [CrossRef]
  18. S. M. Chitanvis, “Explosion of Water Droplets,” Appl. Opt. 25, 1837 (1986); J. C. Carls, J. R. Brock, “Explosion of a Water Droplet by Pulsed Laser Heating,” Aerosol Sci. and Technol. 7, 79 (1987).
    [CrossRef] [PubMed]
  19. S. Qian, J. B. Snow, R. Chang, “Coherent Raman Mixing and Coherent Anti-Stokes Raman Scattering from Individual Micrometer-Size Droplets,” Opt. Lett. 10, 499 (1985).
    [CrossRef] [PubMed]
  20. M. J. Soileau, “Air Breakdown by Pulsed Laser Radiation in the 2.7 μm and 3.8 μm Region,” Appl. Phys. Lett. 35, 309 (1979).
    [CrossRef]
  21. D. C. Smith, “Laser Radiation-Induced Air Breakdown and Plasma Shielding,” Opt. Eng. 20, 962 (1981); also D. C. Smith, “Gas-Breakdown Dependence on Beam Size and Pulse Duration with 10.6 μm Wavelength Radiation,” Appl. Phys. Lett. 19, 405 (1971).
    [CrossRef]
  22. W. E. Williams, M. J. Soileau, E. W. Stryland, “Picosecond Air Breakdown Studies at 0.53 μm,” Appl. Phys. Lett. 43, 352 (1983).
    [CrossRef]
  23. E. W. Van Stryland, M. J. Soileau, A. L. Smirl, W. E. Williams, “Pulse-width and Focal-Volume Dependence of Laser-Induced Breakdown,” Phys. Rev. B 23, 2144 (1981).
    [CrossRef]
  24. C. Gray Morgan, “Laser Induced Electrical Breakdown of Gases,” in Electrical Breakdown of Gases, J. M. Meek, Ed. (Wiley, New York, 1978).
  25. W. F. Hsieh, J. H. Eickmans, R. K. Chang, “Internal and External Laser-Induced Avalanche Breakdown of Single Droplets in an Argon Atmosphere,” 4, 1816 (1987).
  26. P. Chў, J. T. Kiehl, M. K. W. Ko, “Optical Levitation and Partial Wave Resonances,” Phys. Rev. A 18, 2229 (1978).
    [CrossRef]

1987

1986

S. M. Chitanvis, “Explosion of Water Droplets,” Appl. Opt. 25, 1837 (1986); J. C. Carls, J. R. Brock, “Explosion of a Water Droplet by Pulsed Laser Heating,” Aerosol Sci. and Technol. 7, 79 (1987).
[CrossRef] [PubMed]

S. Qian, R. K. Chang, “Multiple Order Stokes Emissions from Micrometer-size Droplets,” Phys. Rev. Lett. 56, 926 (1986).
[CrossRef] [PubMed]

S. C. Hill, R. E. Benner, “Morphology Dependent Resonances Associated with Stimulated Processes in Microspheres,” J. Opt. Soc. Am. 3, 1509 (1986).
[CrossRef]

P. Chў, M. A. Jarzembski, N. Y. Chou, R. G. Pinnick, “Effect of Size and Material of Liquid Spherical Particles on Laser-Induced Breakdown,” Appl. Phys. Lett. 49, 1475 (1986).
[CrossRef]

1985

1984

R. Thurn, W. Kiefer, “Observations of Structural Resonances in the Raman Spectra of Optically Levitated Dielectric Microspheres,” J. Raman Spectrosc. 15, 411 (1984).
[CrossRef]

1983

W. E. Williams, M. J. Soileau, E. W. Stryland, “Picosecond Air Breakdown Studies at 0.53 μm,” Appl. Phys. Lett. 43, 352 (1983).
[CrossRef]

1982

J. F. Owen, R. K. Chang, P. W. Barber, “Morphology Dependent Resonances in Raman Scattering, Flourescence Emission, and Elastic Scattering from Microparticles,” Aerosol Sci. Tech. 1, 293 (1982).
[CrossRef]

1981

E. W. Van Stryland, M. J. Soileau, A. L. Smirl, W. E. Williams, “Pulse-width and Focal-Volume Dependence of Laser-Induced Breakdown,” Phys. Rev. B 23, 2144 (1981).
[CrossRef]

D. C. Smith, “Laser Radiation-Induced Air Breakdown and Plasma Shielding,” Opt. Eng. 20, 962 (1981); also D. C. Smith, “Gas-Breakdown Dependence on Beam Size and Pulse Duration with 10.6 μm Wavelength Radiation,” Appl. Phys. Lett. 19, 405 (1971).
[CrossRef]

1980

V. K. Mamanov, “Air Breakdown Minimized by Breakdown in Aqueous Aerosol Drops Acted upon by Radiation with Wavelength 1.06 μm,” J. Sov. Laser Res. 5, 249 (1980).
[CrossRef]

1979

V. A. Pogodaev, A. E. Rozhdestvenskii, “Initiation of Optical Breakdown by Weakly Absorbing Water Droplets,” Sov. Tech. Phys. Lett. 5, 103 (1979).

M. J. Soileau, “Air Breakdown by Pulsed Laser Radiation in the 2.7 μm and 3.8 μm Region,” Appl. Phys. Lett. 35, 309 (1979).
[CrossRef]

1978

P. Chў, J. T. Kiehl, M. K. W. Ko, “Optical Levitation and Partial Wave Resonances,” Phys. Rev. A 18, 2229 (1978).
[CrossRef]

1977

S. V. Zakharchenko, S. M. Kolomiets, A. M. Skripkin, “Breakdown in a Disperse Medium by Laser Radiation,” Sov. Phys. Tech. Phys. 3, 552 (1977).

1975

D. C. Smith, R. T. Brown, “Aerosol-Induced Air Breakdown with CO2 Laser Radiation,” J. Appl. Phys. 46, 1146 (1975).
[CrossRef]

1974

D. E. Lencioni, “Laser-Induced Air Breakdown for 1.06 μm Radiation,” Appl. Phys. Lett. 25, 15 (1974); also D. E. Lencioni, L. C. Pettingill, “The Dynamics of Air Breakdown Initiated by a Particle in a Laser Beam,” J. Appl. Phys. 48, 1848 (1977).
[CrossRef]

1973

D. E. Lencioni, “The Effect of Dust on 10.6 μm Laser-Induced Air Breakdown,” Appl. Phys. Lett. 23, 12 (1973).
[CrossRef]

Barber, P. W.

J. F. Owen, R. K. Chang, P. W. Barber, “Morphology Dependent Resonances in Raman Scattering, Flourescence Emission, and Elastic Scattering from Microparticles,” Aerosol Sci. Tech. 1, 293 (1982).
[CrossRef]

Benner, R. E.

S. C. Hill, R. E. Benner, “Morphology Dependent Resonances Associated with Stimulated Processes in Microspheres,” J. Opt. Soc. Am. 3, 1509 (1986).
[CrossRef]

Brown, R. T.

D. C. Smith, R. T. Brown, “Aerosol-Induced Air Breakdown with CO2 Laser Radiation,” J. Appl. Phys. 46, 1146 (1975).
[CrossRef]

Ch?, P.

P. Chў, M. A. Jarzembski, V. Srivastava, R. G. Pinnick, D. Pendleton, J. Cruncleton, “Effect of Spherical Particles on Laser-Induced Breakdown of Gases,” Appl. Opt. 26, 760 (1987).
[CrossRef]

P. Chў, M. A. Jarzembski, N. Y. Chou, R. G. Pinnick, “Effect of Size and Material of Liquid Spherical Particles on Laser-Induced Breakdown,” Appl. Phys. Lett. 49, 1475 (1986).
[CrossRef]

P. Chў, J. D. Pendleton, R. G. Pinnick, “Internal and Near-Surface Scattered Field of a Spherical Particle at Resonant Conditions,” Appl. Opt. 24, 3940 (1985).
[CrossRef]

P. Chў, J. T. Kiehl, M. K. W. Ko, “Optical Levitation and Partial Wave Resonances,” Phys. Rev. A 18, 2229 (1978).
[CrossRef]

Chang, R.

Chang, R. K.

J. H. Eickmans, W.-F. Hsieh, R. K. Chang, “Laser-Induced Explosion of Water Droplets: Spatially Resolved Spectra,” Opt. Lett. 12, 22 (1987).
[CrossRef] [PubMed]

W. F. Hsieh, J. H. Eickmans, R. K. Chang, “Internal and External Laser-Induced Avalanche Breakdown of Single Droplets in an Argon Atmosphere,” 4, 1816 (1987).

S. Qian, R. K. Chang, “Multiple Order Stokes Emissions from Micrometer-size Droplets,” Phys. Rev. Lett. 56, 926 (1986).
[CrossRef] [PubMed]

J. B. Snow, S. Qian, R. K. Chang, “Stimulated Raman Scattering from Individual Water and Ethanol Droplets at Morphology-Dependent Resonances,” Opt. Lett. 10, 37 (1985).
[CrossRef] [PubMed]

J. F. Owen, R. K. Chang, P. W. Barber, “Morphology Dependent Resonances in Raman Scattering, Flourescence Emission, and Elastic Scattering from Microparticles,” Aerosol Sci. Tech. 1, 293 (1982).
[CrossRef]

Chitanvis, S. M.

Chou, N. Y.

P. Chў, M. A. Jarzembski, N. Y. Chou, R. G. Pinnick, “Effect of Size and Material of Liquid Spherical Particles on Laser-Induced Breakdown,” Appl. Phys. Lett. 49, 1475 (1986).
[CrossRef]

Cruncleton, J.

Eickmans, J. H.

J. H. Eickmans, W.-F. Hsieh, R. K. Chang, “Laser-Induced Explosion of Water Droplets: Spatially Resolved Spectra,” Opt. Lett. 12, 22 (1987).
[CrossRef] [PubMed]

W. F. Hsieh, J. H. Eickmans, R. K. Chang, “Internal and External Laser-Induced Avalanche Breakdown of Single Droplets in an Argon Atmosphere,” 4, 1816 (1987).

Gray Morgan, C.

C. Gray Morgan, “Laser Induced Electrical Breakdown of Gases,” in Electrical Breakdown of Gases, J. M. Meek, Ed. (Wiley, New York, 1978).

Hill, S. C.

S. C. Hill, R. E. Benner, “Morphology Dependent Resonances Associated with Stimulated Processes in Microspheres,” J. Opt. Soc. Am. 3, 1509 (1986).
[CrossRef]

Hsieh, W. F.

W. F. Hsieh, J. H. Eickmans, R. K. Chang, “Internal and External Laser-Induced Avalanche Breakdown of Single Droplets in an Argon Atmosphere,” 4, 1816 (1987).

Hsieh, W.-F.

Jarzembski, M. A.

P. Chў, M. A. Jarzembski, V. Srivastava, R. G. Pinnick, D. Pendleton, J. Cruncleton, “Effect of Spherical Particles on Laser-Induced Breakdown of Gases,” Appl. Opt. 26, 760 (1987).
[CrossRef]

P. Chў, M. A. Jarzembski, N. Y. Chou, R. G. Pinnick, “Effect of Size and Material of Liquid Spherical Particles on Laser-Induced Breakdown,” Appl. Phys. Lett. 49, 1475 (1986).
[CrossRef]

Keifer, W.

Kiefer, W.

R. Thurn, W. Kiefer, “Observations of Structural Resonances in the Raman Spectra of Optically Levitated Dielectric Microspheres,” J. Raman Spectrosc. 15, 411 (1984).
[CrossRef]

Kiehl, J. T.

P. Chў, J. T. Kiehl, M. K. W. Ko, “Optical Levitation and Partial Wave Resonances,” Phys. Rev. A 18, 2229 (1978).
[CrossRef]

Ko, M. K. W.

P. Chў, J. T. Kiehl, M. K. W. Ko, “Optical Levitation and Partial Wave Resonances,” Phys. Rev. A 18, 2229 (1978).
[CrossRef]

Kolomiets, S. M.

S. V. Zakharchenko, S. M. Kolomiets, A. M. Skripkin, “Breakdown in a Disperse Medium by Laser Radiation,” Sov. Phys. Tech. Phys. 3, 552 (1977).

Lencioni, D. E.

D. E. Lencioni, “Laser-Induced Air Breakdown for 1.06 μm Radiation,” Appl. Phys. Lett. 25, 15 (1974); also D. E. Lencioni, L. C. Pettingill, “The Dynamics of Air Breakdown Initiated by a Particle in a Laser Beam,” J. Appl. Phys. 48, 1848 (1977).
[CrossRef]

D. E. Lencioni, “The Effect of Dust on 10.6 μm Laser-Induced Air Breakdown,” Appl. Phys. Lett. 23, 12 (1973).
[CrossRef]

Mamanov, V. K.

V. K. Mamanov, “Air Breakdown Minimized by Breakdown in Aqueous Aerosol Drops Acted upon by Radiation with Wavelength 1.06 μm,” J. Sov. Laser Res. 5, 249 (1980).
[CrossRef]

Owen, J. F.

J. F. Owen, R. K. Chang, P. W. Barber, “Morphology Dependent Resonances in Raman Scattering, Flourescence Emission, and Elastic Scattering from Microparticles,” Aerosol Sci. Tech. 1, 293 (1982).
[CrossRef]

Pendleton, D.

Pendleton, J. D.

Pinnick, R. G.

Pogodaev, V. A.

V. A. Pogodaev, A. E. Rozhdestvenskii, “Initiation of Optical Breakdown by Weakly Absorbing Water Droplets,” Sov. Tech. Phys. Lett. 5, 103 (1979).

V. A. Pogodaev, A. E. Rozhdestvenskii, “Thresholds of Optical Breakdown in Weakly Absorbing Aqueous Aerosol,” in Proceedings, Second All-Union Conference on Propagating Laser Radiation in a Disperse Medium (1982), pp. 123–125.

Qian, S.

Rozhdestvenskii, A. E.

V. A. Pogodaev, A. E. Rozhdestvenskii, “Initiation of Optical Breakdown by Weakly Absorbing Water Droplets,” Sov. Tech. Phys. Lett. 5, 103 (1979).

V. A. Pogodaev, A. E. Rozhdestvenskii, “Thresholds of Optical Breakdown in Weakly Absorbing Aqueous Aerosol,” in Proceedings, Second All-Union Conference on Propagating Laser Radiation in a Disperse Medium (1982), pp. 123–125.

Skripkin, A. M.

S. V. Zakharchenko, S. M. Kolomiets, A. M. Skripkin, “Breakdown in a Disperse Medium by Laser Radiation,” Sov. Phys. Tech. Phys. 3, 552 (1977).

Smirl, A. L.

E. W. Van Stryland, M. J. Soileau, A. L. Smirl, W. E. Williams, “Pulse-width and Focal-Volume Dependence of Laser-Induced Breakdown,” Phys. Rev. B 23, 2144 (1981).
[CrossRef]

Smith, D. C.

D. C. Smith, “Laser Radiation-Induced Air Breakdown and Plasma Shielding,” Opt. Eng. 20, 962 (1981); also D. C. Smith, “Gas-Breakdown Dependence on Beam Size and Pulse Duration with 10.6 μm Wavelength Radiation,” Appl. Phys. Lett. 19, 405 (1971).
[CrossRef]

D. C. Smith, R. T. Brown, “Aerosol-Induced Air Breakdown with CO2 Laser Radiation,” J. Appl. Phys. 46, 1146 (1975).
[CrossRef]

Snow, J. B.

Soileau, M. J.

W. E. Williams, M. J. Soileau, E. W. Stryland, “Picosecond Air Breakdown Studies at 0.53 μm,” Appl. Phys. Lett. 43, 352 (1983).
[CrossRef]

E. W. Van Stryland, M. J. Soileau, A. L. Smirl, W. E. Williams, “Pulse-width and Focal-Volume Dependence of Laser-Induced Breakdown,” Phys. Rev. B 23, 2144 (1981).
[CrossRef]

M. J. Soileau, “Air Breakdown by Pulsed Laser Radiation in the 2.7 μm and 3.8 μm Region,” Appl. Phys. Lett. 35, 309 (1979).
[CrossRef]

Srivastava, V.

Stryland, E. W.

W. E. Williams, M. J. Soileau, E. W. Stryland, “Picosecond Air Breakdown Studies at 0.53 μm,” Appl. Phys. Lett. 43, 352 (1983).
[CrossRef]

Thurn, R.

R. Thurn, W. Keifer, “Structural Resonances Observed in the Raman Spectra of Optically Levitated Liquid Droplets,” Appl. Opt. 24, 1515 (1985).
[CrossRef] [PubMed]

R. Thurn, W. Kiefer, “Observations of Structural Resonances in the Raman Spectra of Optically Levitated Dielectric Microspheres,” J. Raman Spectrosc. 15, 411 (1984).
[CrossRef]

Van Stryland, E. W.

E. W. Van Stryland, M. J. Soileau, A. L. Smirl, W. E. Williams, “Pulse-width and Focal-Volume Dependence of Laser-Induced Breakdown,” Phys. Rev. B 23, 2144 (1981).
[CrossRef]

Williams, W. E.

W. E. Williams, M. J. Soileau, E. W. Stryland, “Picosecond Air Breakdown Studies at 0.53 μm,” Appl. Phys. Lett. 43, 352 (1983).
[CrossRef]

E. W. Van Stryland, M. J. Soileau, A. L. Smirl, W. E. Williams, “Pulse-width and Focal-Volume Dependence of Laser-Induced Breakdown,” Phys. Rev. B 23, 2144 (1981).
[CrossRef]

Zakharchenko, S. V.

S. V. Zakharchenko, S. M. Kolomiets, A. M. Skripkin, “Breakdown in a Disperse Medium by Laser Radiation,” Sov. Phys. Tech. Phys. 3, 552 (1977).

Aerosol Sci. Tech.

J. F. Owen, R. K. Chang, P. W. Barber, “Morphology Dependent Resonances in Raman Scattering, Flourescence Emission, and Elastic Scattering from Microparticles,” Aerosol Sci. Tech. 1, 293 (1982).
[CrossRef]

Appl. Opt.

Appl. Phys. Lett.

D. E. Lencioni, “The Effect of Dust on 10.6 μm Laser-Induced Air Breakdown,” Appl. Phys. Lett. 23, 12 (1973).
[CrossRef]

D. E. Lencioni, “Laser-Induced Air Breakdown for 1.06 μm Radiation,” Appl. Phys. Lett. 25, 15 (1974); also D. E. Lencioni, L. C. Pettingill, “The Dynamics of Air Breakdown Initiated by a Particle in a Laser Beam,” J. Appl. Phys. 48, 1848 (1977).
[CrossRef]

P. Chў, M. A. Jarzembski, N. Y. Chou, R. G. Pinnick, “Effect of Size and Material of Liquid Spherical Particles on Laser-Induced Breakdown,” Appl. Phys. Lett. 49, 1475 (1986).
[CrossRef]

M. J. Soileau, “Air Breakdown by Pulsed Laser Radiation in the 2.7 μm and 3.8 μm Region,” Appl. Phys. Lett. 35, 309 (1979).
[CrossRef]

W. E. Williams, M. J. Soileau, E. W. Stryland, “Picosecond Air Breakdown Studies at 0.53 μm,” Appl. Phys. Lett. 43, 352 (1983).
[CrossRef]

Internal and External Laser-Induced Avalanche Breakdown of Single Droplets in an Argon Atmosphere

W. F. Hsieh, J. H. Eickmans, R. K. Chang, “Internal and External Laser-Induced Avalanche Breakdown of Single Droplets in an Argon Atmosphere,” 4, 1816 (1987).

J. Appl. Phys.

D. C. Smith, R. T. Brown, “Aerosol-Induced Air Breakdown with CO2 Laser Radiation,” J. Appl. Phys. 46, 1146 (1975).
[CrossRef]

J. Opt. Soc. Am.

S. C. Hill, R. E. Benner, “Morphology Dependent Resonances Associated with Stimulated Processes in Microspheres,” J. Opt. Soc. Am. 3, 1509 (1986).
[CrossRef]

J. Raman Spectrosc.

R. Thurn, W. Kiefer, “Observations of Structural Resonances in the Raman Spectra of Optically Levitated Dielectric Microspheres,” J. Raman Spectrosc. 15, 411 (1984).
[CrossRef]

J. Sov. Laser Res.

V. K. Mamanov, “Air Breakdown Minimized by Breakdown in Aqueous Aerosol Drops Acted upon by Radiation with Wavelength 1.06 μm,” J. Sov. Laser Res. 5, 249 (1980).
[CrossRef]

Opt. Eng.

D. C. Smith, “Laser Radiation-Induced Air Breakdown and Plasma Shielding,” Opt. Eng. 20, 962 (1981); also D. C. Smith, “Gas-Breakdown Dependence on Beam Size and Pulse Duration with 10.6 μm Wavelength Radiation,” Appl. Phys. Lett. 19, 405 (1971).
[CrossRef]

Opt. Lett.

Phys. Rev. A

P. Chў, J. T. Kiehl, M. K. W. Ko, “Optical Levitation and Partial Wave Resonances,” Phys. Rev. A 18, 2229 (1978).
[CrossRef]

Phys. Rev. B

E. W. Van Stryland, M. J. Soileau, A. L. Smirl, W. E. Williams, “Pulse-width and Focal-Volume Dependence of Laser-Induced Breakdown,” Phys. Rev. B 23, 2144 (1981).
[CrossRef]

Phys. Rev. Lett.

S. Qian, R. K. Chang, “Multiple Order Stokes Emissions from Micrometer-size Droplets,” Phys. Rev. Lett. 56, 926 (1986).
[CrossRef] [PubMed]

Sov. Phys. Tech. Phys.

S. V. Zakharchenko, S. M. Kolomiets, A. M. Skripkin, “Breakdown in a Disperse Medium by Laser Radiation,” Sov. Phys. Tech. Phys. 3, 552 (1977).

Sov. Tech. Phys. Lett.

V. A. Pogodaev, A. E. Rozhdestvenskii, “Initiation of Optical Breakdown by Weakly Absorbing Water Droplets,” Sov. Tech. Phys. Lett. 5, 103 (1979).

Other

V. A. Pogodaev, A. E. Rozhdestvenskii, “Thresholds of Optical Breakdown in Weakly Absorbing Aqueous Aerosol,” in Proceedings, Second All-Union Conference on Propagating Laser Radiation in a Disperse Medium (1982), pp. 123–125.

C. Gray Morgan, “Laser Induced Electrical Breakdown of Gases,” in Electrical Breakdown of Gases, J. M. Meek, Ed. (Wiley, New York, 1978).

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Figures (11)

Fig. 1
Fig. 1

Schematic of experimental setup for measuring laser breakdown thresholds. Radiation from a Q-switched Nd:YAG laser is focused by a lens to a 30–100-μm beam waist. Uniform droplets emanating from the aerosol generator are directed through the focal point where they initiate stimulated Raman scattering (observed through the filter and Zeiss Universal microscope) and laser breakdown (detected by observing luminous regions of ionization on or near the drop surface and emissive plumes of material ejected from the droplet). To achieve synchronous strobing of the droplets, the laser is triggered via a scope triggered from the aerosol generator signal, but not faster than 10 Hz. The pyrolectric and acoustic detector signals are measured by feeding them into another scope, triggered with the same signal used to trigger the laser. Laser fluence levels are read from both the pyroelectric detector and calorimeter.

Fig. 2
Fig. 2

Photographs of SRS and emissive plumes generated by irradiating 50-μm diam methanol droplets with intense 0.355-μm wavelength radiation from a frequency-tripled Nd-YAG pulsed laser. Photos are taken perpendicular to the direction of propagation, which is from the left in each photo. At laser intensities below that required for breakdown, SRS appears in the form of rings (blue, green, and red rings are seen visually) around the periphery of drops (a, b). At the breakdown threshold a luminous region and forward plume (on the shadow side of the drop) appears (c). At higher intensities this plume grows (d) and eventually a backward plume develops (e) and grows toward the laser source (f).

Fig. 3
Fig. 3

Previous measurements of clean air and aerosol-induced laser breakdown thresholds at 10.6-, 1.06-, 0.63-, and 0.53-μm laser wavelengths. Aerosol-induced breakdown thresholds for nominal 50-μm diam particles are lower than clean air thresholds by ~2 orders of magnitude.

Fig. 4
Fig. 4

Measurements of clean air and aerosol-induced breakdown thresholds compared with previous measurements. Unlike measurements in the IR, our measurement show a decrease in breakdown thresholds with decreasing wavelength. Our measurements demonstrate that aerosol-induced breakdown thresholds are strongly dependent on droplet composition and are lower for drops with larger real refractive index.

Fig. 5
Fig. 5

Source function along the axis of a water droplet and parallel to the direction of propagation. The source function reaches values of ~200 within the drop surface (defined by −1,+1 on the horizontal coordinate axis) and values of ~2000 in the forward-scattering direction ~1.7 radius units away from the particle center.

Fig. 6
Fig. 6

Peak field enhancement (source function) inside and outside a 50-μm diam water drop as a function of radiation wavelength. These enhancements are believed to contribute to the relatively low values of aerosol breakdown thresholds.

Fig. 7
Fig. 7

Measurements of aerosol-induced breakdown thresholds for nominal 50-μm diam water droplets. The measurements are in qualitative agreement with the prediction (8), which accounts for enhancement of local fields and which assumes that multiphoton absorption is the dominant mechanism in initiation of breakdown. On the other hand, Eq. (9), which assumes cascade-collision ionization to be dominant, is in poor agreement with measurement.

Fig. 8
Fig. 8

Transmission of laser energy through aerosol-induced breakdown plasma vs laser wavelength. Beam waists are between 30 and 40 μm. Measurements have a weak dependence on droplet composition. The decrease in transmission with increasing wavelength is likely a consequence of the longer pulse lengths at the longer wavelengths, which allows more time for the plasma to grow in spatial extent and thereby reduce transmitted energy.

Fig. 9
Fig. 9

Nd:YAG laser beam waist profile at a 0.53-μm wavelength. The profile is a densitometer scan of a photographic image of the beam focused in a cell containing small latex particles suspended in water. The FWHM is 33 μm.

Fig. 10
Fig. 10

Nd:YAG laser beam waist profile at 0.53 μm. The profile represents measurements of transmitted laser energy as a knife-edge is translated through the focal point perpendicular to the direction of propagation. Under the assumption that 75% of the beam energy is contained within the FWHM points (as for a Gaussian beam), the FWHM beam waist is 38 μm.

Fig. 11
Fig. 11

Time-resolved measurements of the shot-to-shot variations in the Q-switched Nd:YAG laser waveform for the fundamental, doubled, tripled, and quadrupled frequencies. For each laser wavelength pulses typical of the range of laser pulse waveforms are shown.

Tables (4)

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Table I Threshold Laser Intensity and Fluence Thresholds for Aerosol-induced Breakdown a

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Table II Laser Intensity and Fluence Threshold for Clean (Aerosol-free) Air at Atmospheric Pressure

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Table III Number of Photons Required in Multiphoton Absorption to Produce a Positively Ionized Molecule and a Free Electron

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Table IV Nd:YAG Laser (quanta-Ray model DCR-2-10) Beam Characteristics

Equations (9)

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F ma = b ( t / τ ) 1 / k λ 1 1 / k ( multiphoton absorption ) ,
F c c = C U ( t / τ ) λ 2 ( cascade collision ionization ) ,
S = | E | 2 | E 0 | 2 ,
F ma = b S ( t / τ ) 1 / k λ 1 1 / k ( multiphoton absorption and field enhancement ) ;
F cc = C U S ( t / τ ) λ 2 ( cascade collision ionization and field enhancement ) .
S λ 1 . a , a = { 0 . 15 ( inside waterdrops , 0 . 26 μ m < λ < 1 . 06 μ m ) , 0 . 16 ( outside waterdrops , 0 . 26 μ m < λ < 1 . 06 μ m ) .
k ( λ ) = c λ, c = { 5 . 7 μ m 1 , water 10 . 5 μ m 1 , air .
F ma = b λ a + 1 / ( c λ ) ( t / τ ) 1 / ( c λ ) ( multiphoton absorption and field enhancement for water droplets ) .
F cc = C U ( t / τ ) λ 1 a ( cascade collision ionization and field enhancement for water droplets ) .

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