Abstract: 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.