Modified negative-branch confocal unstable resonator

Hall, Thomas; Duschek, Frank; Grünewald, Karin; Handke, Jürgen

doi:10.1364/ao.45.008777

Cited by 16 publications

(6 citation statements)

References 9 publications

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“…The modified negative branch confocal unstable resonator is a promising candidate to be the missing link for lasers with intermediate output power levels. In an earlier publication [10] the principle of the modified negative branch confocal unstable resonator (MNBUR) was explained theoretically using spherical geometry. Meanwhile, verification tests of the MNBUR were performed for the first time, to the best of our knowledge, and the resonator design proves to be easily adaptable to the rectangular geometry of the laser.…”

Section: Introductionmentioning

confidence: 99%

COIL emission of a modified negative branch confocal unstable resonator

Pargmann¹,

Hall²,

Duschek³

et al. 2007

Appl. Opt.

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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 approximately 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.

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Section: Introductionmentioning

confidence: 99%

COIL emission of a modified negative branch confocal unstable resonator

Pargmann¹,

Hall²,

Duschek³

et al. 2007

Appl. Opt.

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“…In order to enhance the beam quality extracted from unstable resonators, a Modified Negative Branch Unstable Resonator (MNBUR) was introduced 6,7 . The optical axis of the negative-branch resonator is shifted apart from the center and the output coupling is performed by a scraper.…”

Section: Introductionmentioning

confidence: 99%

“…The optical axis of the negative-branch resonator is shifted apart from the center and the output coupling is performed by a scraper. Numerical studies have been presented using spherical geometry 6 and numerical as well as experimental results have been shown for rectangular cross-sections 7 . The adaptation to the rectangular cross-section is only done by the shape and position of the scraper.…”

Section: Introductionmentioning

confidence: 99%

Negative-branch unstable resonator in off-axis configuration for rectangular cross-sections

et al. 2011

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An off-axis configuration of the negative-branch confocal unstable resonator is examined numerically and experimentally for a gain medium with rectangular cross-section. Due to less diffraction effects such a configuration yields lower beam divergences than the standard on-axis resonator. The output coupling and the adaptation to the geometry of the gain medium are attained by a scraper. Two different scraper profiles are examined. One profile resembles to a rectangular bracket "[" and the other profile resembles to the letter "L". The experiments are performed with a 10 kW class chemical oxygen iodine laser (COIL), which has a medium of low gain. Both scraper profiles are applied to a resonator of the same magnification. Measurements of the intensity distributions in the near field and in the far field are presented. The setup using the [-shaped scraper yields a higher output coupling and therefore a lower output power and a lower beam divergence, whereas the setup using the L-shaped scraper makes use of the complete gain medium. Furthermore, the L-shaped scraper is reusable for different resonator magnifications.

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“…In earlier publications, a modified negative-branch unstable resonator (MNBUR) was introduced [6,7]. The main intention for the application of the MNBUR is to reflect one-half of the radiation ring, which is coupled out of the standard unstable resonator, back into the resonator.…”

Section: Introductionmentioning

confidence: 99%

Off-axis negative-branch unstable resonator in rectangular geometry

et al. 2010

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The application of an off-axis negative-branch unstable resonator to an active medium of rectangular geometry is examined. The presented unstable resonator consists of spherical mirrors and a scraper mirror. The adaptation to the rectangular cross section is performed by the scraper, which takes two different shapes. One shape resembles a rectangular bracket "[" and the other resembles the letter "L." The [ and L configurations correspond to a shift of the optical axis away from the center of the cross section, toward one of the edges or toward one of the corners, respectively. Both scraper setups are examined numerically and experimentally. Experiments are performed with a multikilowatt class chemical oxygen iodine laser. The active medium is characterized by a low amplification coefficient. Measured results of the intensity distribution in the far field and of the phase distribution in the near field are shown for both resonator configurations. Using the same resonator magnification, the setup with the L-shaped scraper has a lower output coupling and, therefore, a higher output power and a slightly higher beam divergence. The L-shaped scraper configuration is able to cover the gain medium completely.

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Modified negative-branch confocal unstable resonator

Cited by 16 publications

References 9 publications

COIL emission of a modified negative branch confocal unstable resonator

COIL emission of a modified negative branch confocal unstable resonator

Negative-branch unstable resonator in off-axis configuration for rectangular cross-sections

Off-axis negative-branch unstable resonator in rectangular geometry

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