Femtosecond Hydrogen Raman Frequency-Shifter/Pulse-Compressor Based on Revolver Fiber

Generation of 23-fs-long laser pulses with energy of 8.5 μJ at the wavelength of 1.8 μm is achieved by means of Raman conversion of 250-fs 50-μJ pulses at the wavelength of 1.03 μm. The Raman conversion with simultaneous spectral broadening is realized in a hydrogen-filled revolver fiber. Energy conversion efficiency to the Stokes pulses as high as 17% is demonstrated.