Coherent light generators – Particular beam control device – Nonlinear device
Patent
1998-12-17
2000-04-04
Scott, Jr., Leon
Coherent light generators
Particular beam control device
Nonlinear device
372 21, 359327, H01S 310
Patent
active
060470119
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an harmonic generator system for efficiently generating higher order harmonic radiation from an input beam of fundamental frequency radiation. In particular, the system may be used to generate beams of second, third or fourth harmonic radiation. The system is particularly suitable for use with lasers which are used to pump a secondary laser system as multiple output beams may be generated, each being used to drive separate stages of the laser system.
Conventionally, the generation of second harmonic frequencies, 2.omega., may be achieved by irradiating an appropriate crystal with a beam of primary radiation of frequency .omega.. Some fraction of the incident energy is converted into the second harmonic within the crystal. For example, crystals which may be used for the generation of second harmonic frequencies are potassium dihydrogen phosphate (KDP) and ammonium dihydrogen phosphate (ADP).
Second harmonics of a primary laser beam are often used to pump a secondary laser system, for example a dye laser. It is common in most secondary lasers of this type to sub-divide the pumping beam (the second harmonic) into a series of lower energy beams, graded in intensity, which are then used to pump the various stages of the secondary laser system such as the oscillators and the amplifiers.
The efficiency of the second harmonic generation process depends on the crystal material used and the power of the incident primary radiation. Typically, the efficiency with which second harmonics can be generated using a conventional frequency doubling crystal is only 50% to 60% of the primary laser source. The second harmonic may be separated using a prism arrangement or a dichoric mirror and the remaining fraction of fundamental radiation is wasted. Because of the limitation of the efficiency with which higher frequencies can be produced, powerful and bulky lasers may be needed in order to achieve sufficiently energetic second harmonic frequency beams for pumping applications.
The present invention relates to a system for generating a plurality of beams of multiple order harmonic radiation from an input beam of fundamental frequency radiation with a conversion efficiency approaching 100%. In particular, the system may be used to generate a plurality of beams of second, third or fourth harmonic radiation.
The system is particularly suitable for use with lasers which are used as pump sources for a secondary laser system as the output beams are conveniently split into separate beams which may be used to pump the separate stages of the secondary laser system. The system therefore enables a smaller and more convenient primary laser to be used to achieve sufficiently energetic beams of multiple order harmonic radiation than can be achieved using known techniques.
According to the present invention, a system for generating at least two output beams of higher order harmonic radiation from an input beam of fundamental radiation comprises; and generating output radiation comprising beams of fundamental and higher order harmonic radiation, radiation output from the first sample, first and further samples are arranged in series, each further sample having, associated means for increasing the intensity of radiation incident on the further sample and means for separating beams of fundamental and higher order harmonic radiation output from the further sample, further samples pass through the subsequent sample in the series and generate further beams of fundamental and higher order harmonic radiation.
In one embodiment of the invention, the first and further samples are arranged in series such that the beams of fundamental radiation output from each of the first and further samples pass through the next sample in the series, such that at least two output beams of second harmonic radiation may be generated. Preferably, the system comprises a first sample of non linear optical material and two further samples of non linear optical material, such that three output beams of second harmonic radiation may be generated.
The
REFERENCES:
patent: 5519724 (1996-05-01), Tatah
patent: 5912910 (1999-06-01), Sanders et al.
Jr. Leon Scott
The Secretary of State for Defence in Her Majesty's Government o
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