The steady-state stimulated Raman scattering （SRS） gain with different excitation wavelengths ranging from 400 to 1100 nm of tungstate crystals, SrWO4 and BaWO4, is systematically researched. As excitation frequency is close to electronic transition frequency, molecular polarizability is not a constant, which has to be taken into account in our work. The experiment and theory agree well with each other and show that SRS gain is not only proportional to Stokes light frequency, but is also inversely proportional to biquadratic excitation frequency.
Graphene saturable absorber （SA） is used as tile passive Q-switcher of a 0.9-μm solid-state laser the laser medium is a Nd：La0.11Y0.89VO4 crystal, the initial transmittance of the graphene SA is 78%; at an absorbed pump power of 7.62 W, the maximum average output power, largest pulse energy, and minimum pulse width are 0.62 W, 2.58 μJ, and 84 ns, respectively. This study shows that graphene is a promising and cost-saving SA for 0.9-μm pulse generation.
By using a pulse laser at 532.36 nm as the incident light,stimulated Raman scattering(SRS)of a series of a-cut and c-cut Nd:Lu_(x)Y_(1−x)VO_(4)(x=0,0.10,0.26,0.41,0.61,0.67,0.80)crystals is investigated.For theπ-polarization(E||c),the gain coefficient reduced as x value increased.For theσ-polarization(E||a),the Raman gain of all of the mixed crystals is larger than the pure Nd:YVO_(4),and the maximum value is obtained from the Nd:Lu_(0.1)Y_(0.9)VO_(4)crystal.Such results are also supported by the measurement of spontaneous Raman scattering spectra.
Owing to the small differences between the cross-sections of the four emission peaks around 1.3 μm, an efficient four-wavelength synchronous launched laser is demonstrated using a Nd：Gd Lu AG crystal. The laser has no special resonator design. The maximum output power is 4.28 W, which corresponds to a conversion efficiency of 45.6%. For the Q-switching, the laser operated in dual-wavelength mode, and the single pulse energy is maintained at ～80 μJ. By calculating the population inversion density, multi-wavelength emission characteristics in both continuous wave and Q-switching lasers are discussed.
