Abstract

A new type of unstable resonator has been developed that permits multiple-selected-line operation. Selected-line operation is obtained with a diffraction grating that is oriented at an angle that is different from the Littrow angle. Secondary feedback mirrors at the appropriate angles provide an independent three-element cavity for each wavelength selected. The off-Littrow configuration is less efficient than a single-line cavity at the Littrow angle because there are secondary zero-order beams at each wavelength as well as a primary zero-order beam at all selected wavelengths. In the limit of a high gain this loss in efficiency is shown to be significantly reduced. Two types of multiple-selected-line unstable resonators are considered: an edge-coupled design, which produces an annular beam with a 45° output coupling mirror, and a continuously coupled design, which uses the primary zero-order beam as output. Experiments have been carried out with a multiple-selected-line unstable resonator on a cw HF laser. Selected-line operation was obtained on the P₂(5) and P₁(6) HF transitions in a continuously coupled design.

© 1974 Optical Society of America

Unstable Optical Resonators

A. E. Siegman
Appl. Opt. 13(2) 353-367 (1974)

Three-Dimensional Unstable Resonator Calculations with Laser Medium

D. B. Rensch
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Mode Calculations in Unstable Resonators with Flowing Saturable Gain. 1:Hermite-Gaussian Expansion

A. E. Siegman and Edward A. Sziklas
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Unstable resonator with multiple outputs

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Multiple line and polarization control in a far infrared laser with a compound grating resonator

Paul A. Rochefort, Eric Brannen, and Zdenek Kucerovsky
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