Xiaofu Zhang

High average power 1.5 microm eye-safe Raman shifting in BaWO4 crystals.

A nanosecond 1.3 microm Nd:YAG laser-pumped external cavity eye-safe Raman laser based on BaWO(4) crystal is efficiently demonstrated. The average power of 1.5 microm was 0.60 W operating at a pulse repetition rate of 1.7 kHz and an incident pump power of 4.14 W. Conversion efficiency of 14.5% and a high slope efficiency of 54.5% have been achieved. Pulse shortening was obviously observed. The pulse duration of the first Stokes was about 40 ns, much shorter than the fundamental pulse with a duration of approximately 220 ns.

Stimulated Raman scattering of picosecond pulses in a YVO4 crystal

Stimulated Raman scattering (SRS) with a picosecond pulse in YVO4 crystals in a transient state was investigated. The picosecond gain of YVO4 crystals pumped by a 532-nm laser evaluated by means of the threshold was 16.13 cm/GW.

Analytical solution of on-axis beam propagation for Z-scan technique

An analytical solution of on-axis beam propagation is presented for determining the nonlinear refraction and nonlinear absorption of a thin nonlinear medium accurately, efficiently, and simultaneously by a single Z-scan method. This result is based on the general Huygens-Fresnel principle. When applying our theoretical solution to the case without nonlinear absorption, it converges to the current formula based on the Huygens-Fresnel principle. For the first-order approximation, it agrees with the expression obtained by the Gaussian decomposition method. Because of the nonlinear absorption, the peaks of the Z-scan shape are suppressed, while the variation in the valleys depends on the nonlinear phase parameters.

A Highly Efficient Quasi-Continuous-Wave Diode-Pumped Nd: YAG Rod Laser with a 3.8 kW Output

A quasi-continuous-wave (QCW) Nd:YAG-rod laser with a 3.8 kW output and a 54% optical-optical efficiency is demonstrated by the stable zone control of resonator, which overcomes the limitations of thermal lens effect of Nd: YAG rod.