Abstract

Recent experimental measurements of nonlinear, multiple-pulse propagation are presented. Long atmospheric paths were simulated by laboratory scale instrumentation. Blooming was examined as a function of pulse overlap. Observed peak target intensities decreased as the pulse repetition frequency increased and as the effective transverse wind decreased. Theoretical predictions from two computer codes are shown to be consistent with the measurements. A significant fraction of the induced beam distortions were corrected by phase compensation with a deformable mirror.

© 1977 Optical Society of America

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References

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  1. J. Wallace and J. Q. Lilly, “Thermal blooming of repetitively pulsed laser beams,” J. Opt. Soc. Am. 64, 1651–1655 (1974).
    [CrossRef]
  2. A. H. Aitken, J. N. Hayes, and P. B. Ulrich, “Thermal blooming of pulsed focused Gaussian laser beams,” Appl. Opt. 12, 193–197 (1973).
    [CrossRef] [PubMed]
  3. D. C. Smith, “Overview of laser radiation induced gas breakdown,” paper presented at the First DoD Conference on High Energy Laser TechnologySan Diego, Calif., October 1974 (unpublished).
  4. J. Wallace and J. Pasciak, “Compensating for thermal blooming of repetitively pulsed lasers,” J. Opt. Soc. Am. 65, 1257–1260 (1975).
    [CrossRef]
  5. P. B. Ulrich, Naval Research Laboratories, Washington, D. C. (private communication).
  6. J. Q. Lilly, “Simplified calculation of laser beam propagation through the atmosphere,” Technical Report RH-76-9, U. S. Army Missile Command, Redstone Arsenal, Alabama, January1976 (unpublished).
  7. F. G. Gebhardt, “Experimental demonstration of the use of phase correction to reduce thermal blooming” (unpublished).

1975 (1)

1974 (1)

1973 (1)

Aitken, A. H.

Gebhardt, F. G.

F. G. Gebhardt, “Experimental demonstration of the use of phase correction to reduce thermal blooming” (unpublished).

Hayes, J. N.

Lilly, J. Q.

J. Wallace and J. Q. Lilly, “Thermal blooming of repetitively pulsed laser beams,” J. Opt. Soc. Am. 64, 1651–1655 (1974).
[CrossRef]

J. Q. Lilly, “Simplified calculation of laser beam propagation through the atmosphere,” Technical Report RH-76-9, U. S. Army Missile Command, Redstone Arsenal, Alabama, January1976 (unpublished).

Pasciak, J.

Smith, D. C.

D. C. Smith, “Overview of laser radiation induced gas breakdown,” paper presented at the First DoD Conference on High Energy Laser TechnologySan Diego, Calif., October 1974 (unpublished).

Ulrich, P. B.

Wallace, J.

Appl. Opt. (1)

J. Opt. Soc. Am. (2)

Other (4)

P. B. Ulrich, Naval Research Laboratories, Washington, D. C. (private communication).

J. Q. Lilly, “Simplified calculation of laser beam propagation through the atmosphere,” Technical Report RH-76-9, U. S. Army Missile Command, Redstone Arsenal, Alabama, January1976 (unpublished).

F. G. Gebhardt, “Experimental demonstration of the use of phase correction to reduce thermal blooming” (unpublished).

D. C. Smith, “Overview of laser radiation induced gas breakdown,” paper presented at the First DoD Conference on High Energy Laser TechnologySan Diego, Calif., October 1974 (unpublished).

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Figures (3)

FIG. 1
FIG. 1

Typical deformable mirror profile. Measured from laboratory mirror via interferometric techniques. When this profile is shifted off the beam center, the deformable mirror provides a good approximation to profiles required for correction when the number of pulses per flow time (K) is small.

FIG. 2
FIG. 2

Peak target intensity measured as a function of pulse repetition frequency. Data with error bars ( josa-67-3-295-i001) are normalized by the undistorted value. Experimental conditions: a = 0.56 cm, F = 5.8, E = 0.41 J, vx = 0.60 cm/s (uniform), α = 2.7 m−1, Nl = 0.36, and a detector diameter of 400 μm. Computer code predictions from Refs. 5 and 6 for parameters encompassing the experimental conditions are given by the shaded region.

FIG. 3
FIG. 3

Peak target intensity measured as a function of transverse wind velocity (uniform). Data with error bars ( josa-67-3-295-i001) are normalized by the undistorted value. Experimental conditions; a = 0.56 cm, F = 10, E = 0.46 J, PRF = 6, α = 1.9 m−1, Nl = 0.36, and detector diameter of 400 μm. Computer code predictions from Refs. 5 and 6 parameters encompassing the experimental conditions are given by the shaded region.

Tables (2)

Tables Icon

TABLE I Maximum phase requirements calculated by a multiple-pulse propagation code (ϕf). K is the number of pulses per flow time, Nl = 0.35, F = 9.3, λ = 10.6 μm, β(optical beam quality factor) = 2, and PRF = 6. Phase is given in units of wavelengths of CO2.

Tables Icon

TABLE II Irel vs mirror profile. For experimental conditions: a = 0.56 cm, F = 10, E = 0.41 J, PRF = 6, vx = 0.89 cm/s, α = 2.2 m−1, and Nl = 0.34. Experimental sequence corresponds with lettering sequence. Optimum correction was achieved in case (e).

Equations (2)

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N l = 2 ( η T ) E α z 2 h ( α z ) π n 0 ρ c p a 4 ,
h ( α z ) = 2 α z ( 1 - ( 1 - e - α z ) α z )