Abstract

In this paper we discuss certain aspects concerning the transport and focusing of a high power far-IR laser beam into a plasma for Thomson scattering measurements. To attain the required megawatt power level in a D2O laser, it is important to use efficiently the volume of the optically pumped vapor. The best known method to achieve this is use of an unstable resonator which produces a beam with an annular intensity profile. This has a negative effect on the quality of the focused beam and on the intensity profile incident on the beam dump. A system utilizing a Cassegrainian telescope and spatial filtering techniques is found to be a good solution.

© 1983 Optical Society of America

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References

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  1. A. E. Siegman, Appl. Opt. 13, 353 (1974).
    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef] [PubMed]
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  7. R. Behn, I. Kjelberg, P. D. Morgan, T. Okada, M. R. Siegrist, “A High Power D2O Laser Optimized for Microsecond Pulse Duration,” Laboratory Report LRP 213/82 CRPP-EPFL, Lausanne (1982).
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]

1981 (3)

1980 (1)

1979 (1)

P. D. Morgan, M. R. Green, M. R. Siegrist, R. L. Watterson, Comments Plasma Phys. Controlled Fusion 5, 141 (1979).

1974 (2)

Behn, R.

R. Behn, I. Kjelberg, P. D. Morgan, T. Okada, M. R. Siegrist, “A High Power D2O Laser Optimized for Microsecond Pulse Duration,” Laboratory Report LRP 213/82 CRPP-EPFL, Lausanne (1982).

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, London, 1970), p. 416.

Casperson, L. W.

Green, M. R.

M. R. Siegrist, M. R. Green, P. D. Morgan, R. L. Watterson, Appl. Opt. 19, 3824 (1980).
[CrossRef] [PubMed]

P. D. Morgan, M. R. Green, M. R. Siegrist, R. L. Watterson, Comments Plasma Phys. Controlled Fusion 5, 141 (1979).

Johnson, M. M.

Kjelberg, I.

R. Behn, I. Kjelberg, P. D. Morgan, T. Okada, M. R. Siegrist, “A High Power D2O Laser Optimized for Microsecond Pulse Duration,” Laboratory Report LRP 213/82 CRPP-EPFL, Lausanne (1982).

Morgan, P. D.

M. R. Siegrist, M. R. Green, P. D. Morgan, R. L. Watterson, Appl. Opt. 19, 3824 (1980).
[CrossRef] [PubMed]

P. D. Morgan, M. R. Green, M. R. Siegrist, R. L. Watterson, Comments Plasma Phys. Controlled Fusion 5, 141 (1979).

R. Behn, I. Kjelberg, P. D. Morgan, T. Okada, M. R. Siegrist, “A High Power D2O Laser Optimized for Microsecond Pulse Duration,” Laboratory Report LRP 213/82 CRPP-EPFL, Lausanne (1982).

Okada, T.

R. Behn, I. Kjelberg, P. D. Morgan, T. Okada, M. R. Siegrist, “A High Power D2O Laser Optimized for Microsecond Pulse Duration,” Laboratory Report LRP 213/82 CRPP-EPFL, Lausanne (1982).

Scott, P. W.

Siegman, A. E.

Siegrist, M. R.

M. R. Siegrist, M. R. Green, P. D. Morgan, R. L. Watterson, Appl. Opt. 19, 3824 (1980).
[CrossRef] [PubMed]

P. D. Morgan, M. R. Green, M. R. Siegrist, R. L. Watterson, Comments Plasma Phys. Controlled Fusion 5, 141 (1979).

R. Behn, I. Kjelberg, P. D. Morgan, T. Okada, M. R. Siegrist, “A High Power D2O Laser Optimized for Microsecond Pulse Duration,” Laboratory Report LRP 213/82 CRPP-EPFL, Lausanne (1982).

Southwell, W. H.

Watterson, R. L.

M. R. Siegrist, M. R. Green, P. D. Morgan, R. L. Watterson, Appl. Opt. 19, 3824 (1980).
[CrossRef] [PubMed]

P. D. Morgan, M. R. Green, M. R. Siegrist, R. L. Watterson, Comments Plasma Phys. Controlled Fusion 5, 141 (1979).

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, London, 1970), p. 416.

Appl. Opt. (5)

Comments Plasma Phys. Controlled Fusion (1)

P. D. Morgan, M. R. Green, M. R. Siegrist, R. L. Watterson, Comments Plasma Phys. Controlled Fusion 5, 141 (1979).

J. Opt. Soc. Am. (1)

Other (2)

M. Born, E. Wolf, Principles of Optics (Pergamon, London, 1970), p. 416.

R. Behn, I. Kjelberg, P. D. Morgan, T. Okada, M. R. Siegrist, “A High Power D2O Laser Optimized for Microsecond Pulse Duration,” Laboratory Report LRP 213/82 CRPP-EPFL, Lausanne (1982).

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Figures (6)

Fig. 1
Fig. 1

Beam profiles of a flat annular intensity distribution (diameter, 20 cm; hole diameter, 10 cm) for propagation distances z of 2, 5, 10, 20, 50 m. (Left) integral method; (right) differential method.

Fig. 2
Fig. 2

Focusing of a flat annular intensity distribution with a lens of f = 50 cm: curve 1, initial profile; 2, profile in focal plane; 3, profile at distance f beyond focus.

Fig. 3
Fig. 3

Free space propagation of a flat annular intensity distribution. Radial intensity profiles are shown for axial distances up to 45 m.

Fig. 4
Fig. 4

Three beam qualifiers for the intensity distribution in the focal plane of a lens as a function of the size of the hole of an initially flat annular profile: (a) halfwidth of central lobe; (b) intensity ratio of the second and first maximum; (c) fraction of energy contained in central lobe.

Fig. 5
Fig. 5

Schematic of beam transport system for Thomson scattering measurements with an unstable resonator D2O laser. A telescopic system allows use of a small output window and spatial filtering. Calculated radial beam profiles are shown for several positions.

Fig. 6
Fig. 6

Beam profiles at the position of the beam dump for three beam transport systems (compare with Fig. 5): (a) direct focusing with element M3; (b) system shown in Fig. 5; (c) as (b) with aperture at P2.

Tables (3)

Tables Icon

Table I Fill-in Distances for Annular Beams of 20-cm External Diameter

Tables Icon

Table II Beam Qualifiers in the Plane at Distance 2f from the Lens. Initial Profile: Flat, Annular, 20-cm o.d.

Tables Icon

Table III Beam Qualifiers in the Planes P4 (Focus) and P5 (Beam Dump) for the System shown in Fig. 5

Equations (3)

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I ( ρ ) = 4 / ( 1 2 ) 2 · [ J 1 ( ρ ) / ρ 2 J 1 ( ρ ) / ρ ] 2 · I in ,
E a / E tot = 1 2 0 ρ a ( 1 2 ) I ( ρ ) / I 0 · ρ d ρ .
R 1 = 2 d R 2 2 d 4 d R 2 ,

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