Semiconductor Raman laser with resonator film transparent to pump light

A waveguide structure semiconductor Raman laser for which the pump beam is incident through a multilayer dielectric film transparent for the pump light but highly reflective for the Stokes light is reported. There is no need to open a window for pump beam introduction. Accordingly, narrow waveguides with a width of 10 μm have been fabricated and successful operation has been achieved using a pulse-modulated pump beam from a CW-YAG laser, instead of a Q-switched YAG laser used in the previous experiments. This structure is capable of further reducing the size of the waveguide cross-section to realise very low threshold operation necessary for use in wideband optical communications