Coherent light generators – Particular active media – Gas
Patent
1996-01-19
1997-10-07
Scott, Jr., Leon
Coherent light generators
Particular active media
Gas
322 92, 322 97, 322 98, 322107, H01S 303
Patent
active
056756038
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a laser device.
2. Discussion of Prior Art
Lasers are well known in the prior art, having been first invented in 1960 by T. H. Maiman. In a laser, electromagnetic radiation is reflected between two ends of a resonating cavity stimulating transitions from excited energy levels to lower energy levels, which results in the generation of further photons in phase and travelling in the same direction as the stimulating radiation. The ends of the cavity must be sufficiently reflecting so that the amount of radiation absorbed or transmitted at the mirror is less than or equal to the amount of radiation generated by this stimulation process. Prior art lasers include a partially reflecting cavity mirror in their construction to reflect a high percentage of incident radiation back into the cavity and transmit a small fraction as the laser beam. Partially reflecting mirrors incorporating a number of dielectric layers are relatively expensive to produce; also, partially reflecting mirrors are susceptible to damage in high power applications.
An example of a laser device is a He:Ne gas filled laser as described on page 486 of the book `Optics` by E. Hecht and A. Zajac published by the Addison-Wesley Publishing Company Inc. of Massachusetts USA in 1974.
SUMMARY OF THE INVENTION
The present invention provides a laser device including waveguiding means and first and second reflecting means arranged to define a resonant cavity, characterised in that the waveguiding means is arranged to define radiation intensity maxima at the first reflecting means, an intensity maximum at least transiently at the second reflecting means, and an intensity maximum at least transiently at an output separate from the first and second reflecting means.
The invention provides the advantage that a partially reflecting output mirror is not required, such mirrors being sensitive to power damage. This is the case particularly for high power carbon dioxide lasers.
The use of a multi-mode propagating waveguide configured as a laser is described in Patent Cooperation Treaty application number WO 92/11550. This describes a laser incorporating a partially reflecting mirror. Patent Cooperation Treaty patent application number WO 92/11554 describes the use of a multi-mode waveguide as an intensity dividing device.
The laser device of the invention may have a multi-mode beamsplitter waveguide which at a first end is connected to two coupling waveguides, one of which is a reflection coupling waveguide and one of which is an output coupling waveguide. The reflection coupling waveguide is terminated by a fully reflecting mirror. Reflecting means are arranged at a second end of the beamsplitter waveguide.
The device may be arranged so that approximately 85% of radiation coupled to the coupling waveguides is coupled to the reflection coupling waveguide and the remaining 15% is coupled to the output coupling waveguide.
The reflecting means at the second end of the beamsplitter waveguide may include modulation waveguides. The modulation waveguides may be arranged to provide phase control of radiation reflected by the reflecting means. Electro-optic phase modulators may be arranged within the modulation waveguides. These phase modulators may be arranged to correct for changes in the dimensions of the device due to thermal effects; they may also be arranged to operate the device in a Q-switched mode by switching radiation intensity maxima between the coupling waveguides. Operation as a Q-switched laser device gives the advantage that a high intensity pulsed output may be produced. The intensity of the output of the laser device may be controlled by controlling the phase modulators.
The reflecting means at the second end of the beamsplitter waveguide may be a flat mirror, and the radiation intensity maxima coupled to the two coupling waveguides may be of equal intensity.
The laser device may be a gas laser with hollow waveguides. The gas provides a gain medium with energy coupled into
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Jr. Leon Scott
The Secretary of State for Defence in her Britannic Majesty's Go
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