Study On The Operating Properties Of The Intracavity Pumped Nanosecond Sum-frequency Mixing Laser At484nm

With the development of science and technology, people have carried out moreresearch in laser application to satisfy the needs. High output power and highefficiency nonlinear frequency conversion technology have become an importantresearch subject in the optical areas. For doubling frequency technology, there havebeen many studies and reports, but the sum frequency technology is not.Nonlinearity sum-frequency technology will broaden the range of laser wavelengthand promote the development of related fields.In this paper, we should solve two problems. We should obtain1030nm laser inthe way of intracavity pumped by the using of the Yb:YAG crystal’s absorptionpeaks at914nm. And sum-frequent blue laser output is gotten at484nm. We analysisdual quasi-three-level wavelengths in the way of sum-frequency. We should obtain1030nm puslsed laser by the using of the nanosecond short pulse pumping Yb:YAGcrystal.In this paper, the intracavity pumped Yb:YAG sum-frequency laser of484nmand the quasi-three-level Q-switch operation are analysised by the way ofcombining the theoretical, numerical simulation and experimental studies. First, weanalysis and imitate quasi-three-level rate equations of914nm, nonlinear theory ofsum frequency and the intracavity pumps characteristics. Then there is the highesteffciency of sum-frequency when the photon density of808nm pump equals to thephoton density of914nm laser. This is important to the sum-frequency blue laser at484nm. Based on the theoretical analysis of acousto-optic Q-switch and Cr:YAGpassively Q-switch, combined with the characteristics of quasi-three-level andconsidering the lower level of the re-absorption effect, there are expressions of thelaser pulse’s threshold conditions of intracavity photons number, peak power, pulseenergy and pulse width in quasi-three-level operation. It is different from four levelsof Q-switch. The threshold condition is higher than the four-level system.Second, we analysis and optimize the Nd:YVO4crystal. And the concentrationof Nd3+is0.1at.%, and the length is5mm on the optical axis direction. We alsoanalysis and optimize the Yb:YAG crystal, the concentration of Yb3+is0.5at.%, thelength is0.8mm on the optical axis direction. We utilize ABCD Gaussian beamtransmission theory and Matlab software to build and simulate the Z-shape cavitypump Yb: YAG solid-state laser operation and frequency model. To optimize thedesign of the model,we obtain preferable parameters of the cavity by the presentexperimental conditions. The three levels of914nm Q-switch is simulated to obtaina theoretical pulse shape, peak power, pulse energy and pulse width. Finally, we obtain experimentally blue light output at484nm in the way ofdiode end-pumped and sum frequency Z-shape cavity laser. When the power ofpump is15W, the power of484nm blue laser is12.38mW and the beam quality isgood. Experimentally, we obtain quasi-three-level914nm pulse in the linear cavity,pulse width of100ns; and quasi-three-level1030nm pulse in the Z-cavity, pulsewidth of230ns.However, the output power of484nm blue laser can be increased by improveexperimental conditions. And we need more experimental proofs for the Q-quasi-three-level optimization.