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We experimentally explore the fluorescent spectrum of the Nd:YAP crystal to manifest the feasibility of tunable single- and multi-wavelength operations in the (4)F3/2 → (4)I11/2 transition. An intracavity etalon is subsequently exploited to effectively select spectral lines at 1073, 1080, and 1084 nm with the tunabilities of 0.56, 1.13, and 0.1 nm, respectively. We also experimentally obtain multi-wavelength oscillations among various intermanifold lines in the Nd:YAP crystal with the output powers on the order of several watts for each group. Employing the Cr(4+):YAG crystal to realize the passively Q-switched operation, the maximum average output powers as high as 2.3 and 3.5 W for 1073 and 1080 nm are obtained. The corresponding pulse energies at 1073 and 1080 nm are up to 177 and 159 μJ, respectively.

The effect of spatial hole burning (SHB) on dual-wavelength self-mode-locked lasers based on physically combined Nd:YVO4/Nd:LuVO4 and Nd:YVO4/Nd:KGW composite active medium is comparatively investigated. The length of the first Nd:YVO4 crystal is optimized to realize a highly compact and efficient TEM00-mode picosecond laser at 1.06 μm with optical conversion efficiency greater than 20%. When the SHB effect is enhanced by decreasing the separation between the input end mirror and the composite gain medium, it is experimentally found that not only the pulse duration monotonically decreases, but also the temporal behavior gradually displays a narrow-peak-on-a-pedestal shape for the Nd:YVO4/Nd:LuVO4 scheme, while the multipulse operation can be obtained for the Nd:YVO4/Nd:KGW configuration. These phenomena are further explored by numerically simulating mode-locked pulses from the experimentally measured optical spectra.

We originally present a novel tactic to accomplish a compact efficient dual-wavelength synchronously mode-locked laser by physically combining the Nd:YVO4 crystal to the Nd:GdVO4 crystal as a composite gain medium. With the developed method, the total output power at 1.06 μm could be effectually produced to reach 1.3 W under the optimally balanced two-color intensities. The corresponding mode-locked pulse width and repetition rate are measured to be 47 ps and 2.86 GHz, respectively. Through the optical beating between two carrier frequencies of dual-color synchronous pulses, a train of 0.32 THz ultrashort pulses is further generated with the effective duration of down to 1.6 ps.

We report on a high-power diode-pumped self-mode-locked Nd:YLF laser with the pulse repetition rate up to several GHz. A novel tactic is developed to efficiently select the output polarization state for achieving the stable TEM(00)-mode self-mode-locked operations at 1053 nm and 1047 nm, respectively. At an incident pump power of 6.93 W and a pulse repetition rate of 2.717 GHz, output powers as high as 2.15 W and 1.35 W are generated for the σ- and π-polarization, respectively. We experimentally find that decreasing the separation between the gain medium and the input mirror not only brings in the pulse shortening thanks to the enhanced effect of the spatial hole burning, but also effectively introduces the effect of the spectral filtering to lead the Nd:YLF laser to be in a second harmonic mode-locked status. Consequently, pulse durations as short as 8 ps and 8.5 ps are obtained at 1053 nm and 1047 nm with a pulse repetition rate of 5.434 GHz.