High-quality Nd,Yb:YAG crystal with 5 at. % Yb3+ and 0.5 at. % Nd3+ was grown using the Czochralski method. A complete optical characterization was reported including absorption, excitation spectra and luminescence lifetime measurements at room temperature and emission spectra at temperatures ranging from 300 K to 800 K. The emission spectra of Nd3+/Yb3+ co-doped YAG were measured for different excitation wavelengths 808 nm and 940 nm. The presence of Yb3+ emission after excitation in the 4F5/2 and 4F3/2 levels of Nd3+ together with the 4I9/2→ 4F5/2 and 4I9/2→ 4F3/2 bands of Nd3+ in the excitation spectra of Yb3+ ions confirm that energy transfer occurs from Nd3+ to Yb3+. On the other hand, the back transfer from Yb3+ to Nd3+ can be neglected. This conclusion is also in agreement with the vanishing overlap between the Yb3+ emission and Nd3+ absorption. The analysis of the luminescence decay curves obtained after pulsed excitation has been used to further explore energy transfer processes and the interaction mechanism.

A numerical model of intracavity second harmonic generation（SHG） is constructed considering the effect of phase mismatching and birefringent walk-off in nonlinear crystals for optically pumped semiconductor vertical-external-cavity surface-emitting laser（OPS-VECSEL）. The influences of the crystal length and the pump power on the SHG output power for some nonlinear crystals, such as BBO, LBO and PPLN, are studied in detail. The results are in good agreement with the experimental data.

Optical properties and high-order stimulated Raman scattering (SRS) generation in a homemade CVD diamond crystal with 3 × 3 mm2 aperture are investigated in this paper. The high order of the Raman laser has been studied theoretically and demonstrated experimentally. By simulating the Stokes components at different pump intensities and the divergence angles, the pump source was well matched with the size of the crystal. Pumped by using a 1064 nm picosecond laser, five coaxial wavelengths were obtained for the first time based on the CVD diamond at 932 nm, 1064 nm, 1240 nm, 1485 nm, and 1851 nm. This work provides a reference for further development of the optical grade diamond crystal with a large aperture.