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US 4,538,274 AGranted
Q-Switched Raman laser system
AssigneeThe United States of America as represented by the United States Department of Energy
InventorE. Victor George
Life of this patent
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Abstract
Method and apparatus for use of a Raman or Brillouin switch together with a conventional laser and a saturable absorber that is rapidly bleached at a predetermined frequency .nu.=.nu..sub.0, to ultimately produce a Raman or Brillouin pulse at frequency .nu.=.nu..sub.0 .+-..nu..sub.Stokes.
Claims9
A method for producing a pulse of laser radiation of frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S, the method comprising the steps of:
- providing an optical cavity including two end mirrors, with a Raman cell, an energy storage laser amplifier and a saturable absorber therebetween, with the saturable absorber being positioned adjacent to one optical cavity end mirror, with the absorber density N, the length of the saturable absorber L.sub.A, the absorber cross-sectional area Q.sub.A, the effective amplifier gain length L and the amplifier gain per unit length .alpha.L satisfying NQ.sub.A L.sub.A .gtorsim..alpha.L;
- introducing into the Raman cell a Raman-active gas that is excited by passage therethrough of radiation of frequency .nu.=.nu..sub.0 and that emits radiation at the first Stokes or anti-Stokes frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S corresponding to excitation at frequency .nu.=.nu..sub.0 ;
- introducing a small intensity pulse of predetermined frequency .nu.=.nu..sub.0 into the optical cavity and causing the pulse to propagate two or more times through the energy storage laser amplifier, the Raman cell, and the saturable absorber;
- introducing a bleaching pulse centered at frequency .nu.=.nu..sub.0 into the saturable absorber so that the absorber becomes substantially transparent to radiation of frequency .nu.=.nu..sub.0 ;
- shortly after introduction of the bleaching pulse, propagating a Raman pulse of predetermined frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S through the Raman cell in timed relationship with a counterpropagating pulse produced by the amplifier itself,
- whereby a high intensity pulse of frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S issues from the Raman cell.
3 more elements
Apparatus for producing a pulse of laser radiation of frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S, the apparatus comprising:
- an optical cavity bounded by two end mirrors substantially parallel and facing one another, at least one of which is substantially 100% reflecting at a predetermined frequency .nu.=.nu..sub.0 ;
- a broadband saturable absorber positioned within the optical cavity and adjacent to one of the end mirrors;
- an energy storage laser amplifier, positioned within the optical cavity between the saturable absorber and the second end mirror, the amplifier being capable of amplifying radiation of frequency .nu.=.nu..sub.0 ;
- a Raman cell having at least two sidewalls, positioned in the optical cavity between the saturable absorber and the second end mirror, and containing a Raman-active gas that is excited by passage therethrough of radiation of frequency .nu.=.nu..sub.0 and emits that radiation at the first Stokes or anti-Stokes frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S corresponding to excitation at frequency .nu.=.nu..sub.0, the cell having at least one sidewall that is substantially transparent to radiation of frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S ;
- seed pulse means to produce and introduce a radiation pulse of frequency .nu.=.nu..sub.0 into the optical cavity so that this pulse propagates from one cavity end mirror to the other cavity end mirror;
- Stokes pulse means, positioned adjacent to the Raman cell to produce a radiation pulse of frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S and to direct this pulse through at least one Raman cell transparent sidewall in timed relationship with passage of the radiation pulse of frequency .nu.=.nu..sub.0 through the Raman cell;
- and
- a mirror that is substantially fully reflecting to incident radiation at frequency .nu.=.nu..sub.0 +.DELTA..nu..sub.S, positioned adjacent to one of the transparent sidewalls of the Raman cell so that radiation from the radiation source passes through the Raman cell once, is reflected at perpendicular incidence by this mirror and passes through the Raman cell a second time.
5 more elements
Dependencies are inferred from the claim text.