Abstract

A modified negative branch confocal unstable resonator (MNBUR) was coupled to the chemical oxygen-iodine laser (COIL) device of the German Aerospace Center. It consists of two spherical mirrors and a rectangular scraper for power extraction. Experimentally measured distributions of the near- and far-field intensities and the near-field phase were found in close agreement to numerical calculations. The extracted power came up to 90% of the power as expected for a stable resonator coupled to the same volume of the active medium. The output power revealed a considerable insensitivity towards tilts of the resonator mirrors and the ideal arrangement of the scraper was found to be straightforward by monitoring the near-field distributions of intensity and phase. The beam quality achieved with the MNBUR of an extremely low magnification of only 1.04 was rather poor but nevertheless in accordance with theory. The demonstrated consistency between theory and experiment makes the MNBUR an attractive candidate for lasers that allow for higher magnification. In particular, it promises high brilliance in application to 100  kW class COIL devices, superior to the conventional negative branch confocal unstable resonator.

© 2007 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  7. K. Kuba, T. Yamamoto, and S. Yagi, "Improvement of slab-laser beam divergence by using an off-axis unstable-stable resonator," Opt. Lett. 15, 121-123 (1990).
    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef]
  13. A. G. Fox and T. Li, "Resonant modes in a maser interferometer," Bell Syst. Tech. J. 40, 453-488 (1961).
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  15. R. V. Shack and B. C. Platt, "Production and use of a lenticular Hartmann screen," J. Opt. Soc. Am. 61, 656-660 (1971).
  16. J. Handke, K. M. Grünewald, and W. O. Schall, "Power extraction in investigations for a 10-kW-class supersonic COIL," Proc. SPIE 3574, 309-314 (1998).
    [CrossRef]

2006 (2)

2005 (1)

T. Hall, "Numerical studies on hybrid resonators for a medium-sized chemical oxygen iodine laser," Opt. Eng. 44, 114201 (2005).
[CrossRef]

2000 (1)

K. M. Grünewald, J. Handke, and F. Duschek, "Small signal gain and temperature profiles in supersonic COIL," Proc. SPIE 4184, 75-78 (2000).
[CrossRef]

1999 (1)

1998 (1)

J. Handke, K. M. Grünewald, and W. O. Schall, "Power extraction in investigations for a 10-kW-class supersonic COIL," Proc. SPIE 3574, 309-314 (1998).
[CrossRef]

1990 (2)

K. Kuba, T. Yamamoto, and S. Yagi, "Improvement of slab-laser beam divergence by using an off-axis unstable-stable resonator," Opt. Lett. 15, 121-123 (1990).
[CrossRef] [PubMed]

N. Hodgson, T. Haase, and H. Weber, "Improved resonator design for rod lasers and slab lasers," Proc. SPIE 1277, 70-84 (1990).
[CrossRef]

1986 (1)

1979 (1)

O. L. Bourne and P. E. Dyer, "A novel stable-unstable resonator for beam control of rare-gas halide lasers," Opt. Commun. 31, 193-196 (1979).
[CrossRef]

1974 (1)

1971 (1)

R. V. Shack and B. C. Platt, "Production and use of a lenticular Hartmann screen," J. Opt. Soc. Am. 61, 656-660 (1971).

1965 (1)

A. E. Siegman, "Unstable optical resonators for laser application," Proc. IEEE 53, 277-287 (1965).
[CrossRef]

1961 (1)

A. G. Fox and T. Li, "Resonant modes in a maser interferometer," Bell Syst. Tech. J. 40, 453-488 (1961).

1900 (1)

J. Hartmann, "Bemerkungen über den Bau und die Justirung von Spektrographen," Z. Instrum. 20, 2-27 (1900).

Appl. Opt. (5)

Bell Syst. Tech. J. (1)

A. G. Fox and T. Li, "Resonant modes in a maser interferometer," Bell Syst. Tech. J. 40, 453-488 (1961).

J. Opt. Soc. Am. (1)

R. V. Shack and B. C. Platt, "Production and use of a lenticular Hartmann screen," J. Opt. Soc. Am. 61, 656-660 (1971).

Opt. Commun. (1)

O. L. Bourne and P. E. Dyer, "A novel stable-unstable resonator for beam control of rare-gas halide lasers," Opt. Commun. 31, 193-196 (1979).
[CrossRef]

Opt. Eng. (1)

T. Hall, "Numerical studies on hybrid resonators for a medium-sized chemical oxygen iodine laser," Opt. Eng. 44, 114201 (2005).
[CrossRef]

Opt. Lett. (1)

Proc. IEEE (1)

A. E. Siegman, "Unstable optical resonators for laser application," Proc. IEEE 53, 277-287 (1965).
[CrossRef]

Proc. SPIE (3)

K. M. Grünewald, J. Handke, and F. Duschek, "Small signal gain and temperature profiles in supersonic COIL," Proc. SPIE 4184, 75-78 (2000).
[CrossRef]

N. Hodgson, T. Haase, and H. Weber, "Improved resonator design for rod lasers and slab lasers," Proc. SPIE 1277, 70-84 (1990).
[CrossRef]

J. Handke, K. M. Grünewald, and W. O. Schall, "Power extraction in investigations for a 10-kW-class supersonic COIL," Proc. SPIE 3574, 309-314 (1998).
[CrossRef]

Other (2)

J. Hartmann, "Bemerkungen über den Bau und die Justirung von Spektrographen," Z. Instrum. 20, 2-27 (1900).

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, 1968).

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Figures (10)

Fig. 1
Fig. 1

Sketch and photograph of the MNBUR showing the output mirror (OM), the back mirror (BM), and the scraper.

Fig. 2
Fig. 2

(a) Arrangement of a scraper in the MNBUR, and (b) the corresponding areas of the resonator mirrors and the scraper exposed to the radiation field.

Fig. 3
Fig. 3

Experimental setup.

Fig. 4
Fig. 4

Total coupling loss and output coupling of MNBUR versus magnification M.

Fig. 5
Fig. 5

Laser power extracted by MNBUR.

Fig. 6
Fig. 6

Calculated (a) near- and (b) far-field intensity distributions of the optimal MNBUR.

Fig. 7
Fig. 7

Numerical and experimental far-field intensity distribution of a MNBUR with a slightly reduced resonator length in the focus of a lens. The numerical results are cuts through the center of the distribution.

Fig. 8
Fig. 8

(a) Measured and (b) calculated near-field intensity distribution of the confocal MNBUR. The calculation is performed with the assumption of a slightly reduced resonator length.

Fig. 9
Fig. 9

(a) Calculated and (b) measured phase distribution of the near field behind a 1:1 image.

Fig. 10
Fig. 10

Changes of the (a) calculated intensity distribution, (b) the measured intensity distribution, and (c) the measured phase distribution of the near field by moving the scraper horizontally in the cavity. In (a) and (b) the maximum scraper displacement is 3   mm and in (c) it is 1.5   mm . The phase measurements show only the lower right corner of the [ shape.

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