Her Majesty the Queen as Represented by the Minister of National Defence

Pierre J Mathieu

Georges R Fournier

Paul Pace

Silvester Wong

Vincent Larochelle

A Raman cell for Raman shifting of a laser pump beam, to an output beam of a different wavelength, the cell containing a gaseous Raman medium at a pressure of 100-1000 PSIG. An input window for a pump beam is located at one end of the cell and an output window for a Raman shifted wavelength output beam is located at the cells opposite end. The output window is formed as a plane mirror having an inner face coated with dielectric thin films which provide a high reflectivity for the wavelength of the pump beam and a partial reflectivity at the cell's Raman shifted wavelength. The input window includes at least one lens that forms a converging lens for the pump beam which has a focal length in the Raman medium of about 3/2 of the cell's inner length to substantially focus the pump beam at the center of the cell after it is reflected back by the inner face of the plane mirror.

Miniature stimulated raman shifting cell

A raman cell oscillator/amplifier arrangement comprising a cell containing a raman high pressure gas or liquid medium with an axicon being located at each end of the cell, one axicon having an input window for a laser pump beam and the axicon at the cell's other end having an output coupler for the raman process converted beam. The axicons directs the laser pump beam towards an extended line focus along the axis of the cell at a shallow angle, the extended line focus for each axicon being collinear with each other to produce an extended raman gain region. By suitable design, it can be ensured that the pump beam energy density at focus is lower than either an optical breakdown or Brillouin backscatter threshold. This provides a means of efficiently producing a raman laser or amplifier having an extended raman gain region without developing problems of optical breakdown, Brillouin backscattering or self-focusing in the case of a liquid raman media.

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Cap-Rouge, Canada

Pierre J Mathieu