Research on Quadratic Nonlinear Technologies for Femtosecond Lasers

The recent progress of the authors' group on developing quadratic nonlinear technologies for femtosecond lasers is reviewed. A novel injective femtosecond optical parametric amplifier (OPA) is developed, which can produce tunable femtosecond laser with central wavelength at 1μm, based on the traditional Ti:sapphine laser. A wideband frequency doubling efficiency, as high as 55%, for femtosecond pulsed laser with central wavelength at 1μm is realized, by using the phase matching reentry principle and adopting partially deuterated KDP crystal as the quadratic nonlinear medium. Finally, a time telescope of femtosecond laser with functions of pulse expanding and spectral narrowing is demonstrated.