Generation of highly efficient self-pumped phase conjugation femtosecond pulse using photorefractive BaTiO 3:Co crystal

Abstract

The generation of highly efficient self-pumped phase conjugate (SPPC) pulse of 180 fs, 810 nm Ti:sapphire laser at 76 MHz in a photorefractive BaTiO 3:Co crystal is demonstrated. Brewster prisms are inserted in front of the photorefractive crystal to make wide bandwidth of the femtosecond pulse spatially separated in order to remove an influence of erasure caused by beam fanning and to avoid spectrum narrowing. A maximum reflectivity is improved from 1.5% without prisms to 6.6% with prisms. The spectral bandwidth of the phase conjugate pulse is also improved from 2.7 to 3.8 nm. The spectral bandwidth of the phase conjugate pulse with prisms measured is approaching 5.1 nm of the incident laser pulse, whereas the phase conjugate pulse without prisms is narrower. Since the refractive index grating that contributes to the generation of the SPPC pulse is only the transmission grating, therefore, the rise-time behavior of the SPPC pulse is smoother than that of continuous wave.