Raman gain from waveguides inscribed in KGd(WO4)2 by high repetition rate femtosecond laser

We report the formation of waveguides in Raman-active KGd(WO4)2 with a focused, high repetition rate femtosecond laser. Parallel guiding regions, formed to either side of the laser-induced damage track, supported TE and TM modes that coupled efficiently to optical fiber at telecom wavelengths. Micro-Raman spectroscopy of the guiding regions revealed the preservation of the characteristic 768 and 901cm−1 Raman mode intensities. Raman gain with 6% efficiency was demonstrated for the 768cm−1 Raman line by pumping the waveguide with an infrared 80ps source, the first time Raman gain has been reported in laser formed waveguides.