Abstract: A crystalline Raman laser source is configured with a crystal Raman medium zigzagged by a pump light at a fundamental frequency of between input and output of the Raman medium such that the pump light sequentially converts to Stokes wave frequencies ?1-?n, the Raman medium having spaced opposite sides bridging the input and output. The Raman medium is provided with a wavelength discriminator coupled to the opposite sides of the Raman medium and configured to guide a desired Stokes frequency to the exit of the Raman medium while being transparent to Stokes wave frequency which is lower than the desired frequency.