Anti-stokes signal conversion of femtosecond pulses at near-ultraviolet wavelength in photonic crystal fibre

Anti-Stokes signals at the near-ultraviolet wavelength are efficiently generated based on degenerate four-wave mixing by coupling the femtosecond pulses into the fundamental mode of a photonic crystal fibre. When the pump pulses with the central wavelength of 840 nm and the average power of 300 mW are used, the conversion efficiency η_s of the anti-Stokes signal at 432 nm can be up to 40c/o, and the pulse width is measured to be 42 fs by the Talbot effect.