Abstract

A large-core multimode optical fiber of a few meters length is studied as a 10-MW beam delivery system for a 15-ns pulsed Nd:YAG laser. A laser-to-fiber vacuum coupler is used to inhibit air breakdown and reduce the probability of dielectric breakdown on the fiber front surface. Laser-induced damage inside the fiber core is observed behind the fiber front surface. An explanation based on a high power density is illustrated by a ray trace. Damaged spots and measurements of fiber output energies are reported for two laser beam distributions: a flat-hat type and a near-Gaussian type. Experiments have been performed to deliver a 100-pulse mean energy between 100 and 230 mJ without catastrophic damage.

© 1997 Optical Society of America

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References

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  1. W. M. Trott, K. D. Meeks, “High power Nd:glass laser transmission through optical fibers and its use in acceleration of thin foil targets,” Appl. Phys. 67, 3297–3301 (1990).
    [CrossRef]
  2. Daoning Su, A. A. P. Boechat, J. D. C. Jones, “Beam delivery by large-core fibers: effect of launching conditions on near-field output profile,” Appl. Opt. 31, 5816–5821 (1992).
    [CrossRef] [PubMed]
  3. S. W. Allison, G. T. Gillies, D. W. Magnuson, T. S. Pagano, “Pulsed laser damage to optical fibers,” Appl. Opt. 32, 291–297 (1993).
  4. N. Bloembergen, “Laser-induced electric breakdown in solids,” IEEE J. Quantum Electron QE-10, 375–386 (1974).
    [CrossRef]

1993 (1)

1992 (1)

1990 (1)

W. M. Trott, K. D. Meeks, “High power Nd:glass laser transmission through optical fibers and its use in acceleration of thin foil targets,” Appl. Phys. 67, 3297–3301 (1990).
[CrossRef]

1974 (1)

N. Bloembergen, “Laser-induced electric breakdown in solids,” IEEE J. Quantum Electron QE-10, 375–386 (1974).
[CrossRef]

Allison, S. W.

Bloembergen, N.

N. Bloembergen, “Laser-induced electric breakdown in solids,” IEEE J. Quantum Electron QE-10, 375–386 (1974).
[CrossRef]

Boechat, A. A. P.

Gillies, G. T.

Jones, J. D. C.

Magnuson, D. W.

Meeks, K. D.

W. M. Trott, K. D. Meeks, “High power Nd:glass laser transmission through optical fibers and its use in acceleration of thin foil targets,” Appl. Phys. 67, 3297–3301 (1990).
[CrossRef]

Pagano, T. S.

Su, Daoning

Trott, W. M.

W. M. Trott, K. D. Meeks, “High power Nd:glass laser transmission through optical fibers and its use in acceleration of thin foil targets,” Appl. Phys. 67, 3297–3301 (1990).
[CrossRef]

Appl. Opt. (2)

Appl. Phys. (1)

W. M. Trott, K. D. Meeks, “High power Nd:glass laser transmission through optical fibers and its use in acceleration of thin foil targets,” Appl. Phys. 67, 3297–3301 (1990).
[CrossRef]

IEEE J. Quantum Electron (1)

N. Bloembergen, “Laser-induced electric breakdown in solids,” IEEE J. Quantum Electron QE-10, 375–386 (1974).
[CrossRef]

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Figures (3)

Fig. 1
Fig. 1

Diagram of the experimental arrangement; the Nd:YAG laser, lens A, and step-index fiber B are arranged along a common optical axis. The pressure inside the laser-to-fiber coupler is ∼3.8 × 10-2 Torr. Pyrometers D and C measure the incident energy and the fiber output energy, respectively. Data digitized by the oscilloscope are on-time recorded by a PC.

Fig. 2
Fig. 2

Localization and length of the damaged spot inside the fiber. L min (■) and L max (□), the minimum and maximum distances of the damaged spot from the fiber front surface, are represented versus distance d between the focal point of the lens and the fiber.

Fig. 3
Fig. 3

Representation at the fiber front surface of the beam propagation by a ray trace. ZZ′ is the beam axis; n 1 and n 2 are the indices of refraction of the fiber core and the optical fiber cladding, respectively. The annular intensity, supposed constant, is distributed on M and localized on an l 0-wide crown Cr (r 0, l 0, 0) on the front surface and on an l-wide crown Cr (r, l, z) at a distance z from the fiber front surface.

Equations (22)

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E=0Δt Pdt=0ΔtS0Ir0, θ, 0dsdt,
P=S0Ir, θ, 0ds.
Par0, 0=02πr0r0+l0Ir, θ, 0rdrdθ,
Par0, 0=Sr0,0Ir0, 0.
Ir0, 0=Par0, 0Sr0, 0.
Ir, z=Par0, 0Sr, z.
Ir, zIr0, 0=Sr0, 0Sr, z
Ir, θ, 0=I0.
Par0P=2l0R02r0.
Pa MaxP=PaR0P=2 l0R0, l0r0.
I0; n1dIR0, 0=SR0, 0S0; n1d
I0;n1dIR0, 0=πR02-R0-l02πl022R0l0, l0R0.
Ir0, θ=IM1-r02R02.
Par0P=4l0r0R021-r02R02.
PaMaxP=PaR0/3P=83×3l0R0.
I0; 2.48n1dIR0/3; 0=SR0/3; 0S0; 2.48n1d.
I0; 2.48n1dIR0/3, 0=23R0l0.
PaMaxparaboloid=PaR0/3,
PaMax paraboloid=433 πl0IMR0,
PaMax flat-hat=PaR0=2πl0I0R0.
PaMax paraboloidPaMax flat-hat=43×3  0.77.
I0; 2.48n1dI0; n1d=43×3×13 0.44.

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