Coherent light generators – Particular resonant cavity – Folded cavity
Patent
1981-12-04
1985-02-12
Sikes, William L.
Coherent light generators
Particular resonant cavity
Folded cavity
372 97, 372 95, 372 87, 372107, 372108, 372 23, 372 55, H01S 3081
Patent
active
044995822
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a laser system consisting of a housing surrounding a resonator chamber and including an electrode assembly comprising a center electrode with at least two surfaces serving for electrical discharge and at least two outer electrodes opposite the first electrodes. At the end faces of the housing, at the level of the space between the electrodes, there are provided optical elements that are either reflective to return the laser beam in the opposite direction and/or are at least partially transmitting to permit coupling the laser beam out of the cavity. The beam-deviating elements are disposed at some angle relative to the beam direction.
A laser system of this kind is described, for example, in the W. German Offenlegungsschrift No. 27 533 304. In principle, any of the optical elements, if suitably constructed, can be used for coupling out the laser beam. If the optical element is embodied as a wavelength-selecting mirror, each mirror can couple out laser beams of different wavelength. The preferred construction, however, is a ring laser, i.e., an unstable resonator having only one exit mirror, as described in the Journal of Applied Physics, Vol. 42, Number 8, July 1971, pages 3133 to 3137, entitled "CO.sub.2 regenerative ring power amplifiers" by C. B. Buczek. R. J. Freiberg and M. L. Skolnick. Other details regarding ring lasers are to be found in the article "Der Ring Laserein neues Konzept fuer Farbstofflaser" by Gunter Hummelt, which appeared in the technical journal ELEKTRONIK, 1978, issue 12, pages 85 ff. An oscillator laser amplifier is described in "Applied Physics Letters, Vol. 24, No 7, Apr. 1, 1974, pages 306-307, and in the article "Generation of bandwidth-limited pulses from a TEA CO.sub.2 laser using p-type germanium", by A. F. Gibson, M. F. Kimmitt and B. Norris.
The object of the invention lies in improving the power output of the generic laser for at least one wavelength. This object is attained, according to the invention, in that all four optical elements deviate the laser beam in the manner of a ring laser in the direction of the opposite optical element by suitable mutual disposition of obliquely placed surfaces. The favorable utilization of the active medium makes possible a rapid increase of amplification. When the laser is embodied as a unstable resonator, the energy yield in single mode ooperation is high, i.e, the efficiency is high. While the disposition of the optical elements at 45.degree. to the beam direction is standard, thereby giving the overall beam path a rectangular shape, other angles are possible in principle if the mechanism for coupling out the beam should make that necessary. For example, it is possible that diagonally opposite optical elements are so placed as to subtend the same angle relative to the laser beam.
A further embodiment of the invention provides, for use with two or more wavelengths and with suitably partitioned electrodes, for the optical elements to be pivotable about an axis perpendicular to the horizontal main apparatus plane such that each of the free spaces between the electrodes is associated with a different wavelength. In this way, one obtains a two-wave or multiple-wave laser with synchronously generated wavetrains. The partitioning of the electrodes is understood to mean that, by reducing the width of the electrodes while keeping the discharge volume constant, the resonator volume can be subdivided into any desired number of mutually parallel beam paths, keeping the overall beam power constant. The simplest kind of partitioning is that of two beam paths created by a central electrode and two opposing outer electrodes having two effective surfaces. Such a partition as well as more complicated ones are described in the afore-mentioned Offenlegungsschrift. If the wavelengths are far apart, it may be useful, in the present context, to embody the surfaces of the optical elements associated with the various wavelengths as diffraction gratings with different grating constants.
In order to correct or homogenize any inhomogenou
Karning Heinrich
Prein Franz
Vierling Karl-Heinz
Jr. Leon Scott
Sikes William L.
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