Gec Ferranti Defence Systems Limited

Stewart T Whittley

This invention provides a Raman laser wherein a light beam from a laser source (1) passes through a first chamber (3) and experiences Raman scattering, and then passes through a second chamber (9) and experiences further Raman scattering, such that the output of the Raman laser is frequency shifted. The first and second chambers may be distinct from each other enabling different types and pressures of gases to be utilised, or may be one and the same (20) providing a particularly compact arrangement. A Raman laser in accordance with the invention is particularly suitable for the production of light consisting of multiple rotational Raman orders, and particular embodiments enable frequency switching to be achieved and also provides arrangements which reduce the problems of boresight stability and gas circulation encountered with previous designs.

Raman laser

The present invention provides a Raman laser wherein hazardous radiation from a pump laser source 20 is focused by lens 25 via a cell 27 containing a Raman active medium before passing to a absorbing beam dump 30. Lasing action is maintained within the cell 27 by the action of mirrors 29 and 26 which are respectively totally and partially reflective to radiation generated at the Raman wavelength, and which are both transmissive to the pump beam. A Raman beam exits the cell via partially transmissive mirror 26 is refocused by lens 25 and passes through to the output of the device 31. This configuration provides a Raman laser where the 'eyesafe' Raman beam is generated in a backwards direction relative to the pump beam, so that during normal operation, or in the event that the optics breakdown, or conversion does not take place within the cell, the output beam would not be contaminated by potentially harmful wavelengths at a hazardous level.

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Edinburgh, United Kingdom

Stewart T Whittley