Cr (4 +): Yag Passively Q-switched Laser Gain Medium

As a new solid laser material in recent years, Cr4+:YAG crystal has super advantages, such as big absorption cross section, stable saturable absorption, good heat-conducting and mechanical performance. With the theoretical and experimental methods, the characters of Cr4+:YAG are studied from Cr4+:YAG as passive Q-switching in Nd:YAG laser, intracavity frequency-doubling of Q-switching laser and dual-wavelength laser, which is based on Cr4+:YAG's operations of saturable absorption and laser gaining medium.Chapter 1: Introducing the Cr4+:YAG's optical function, the general research situation and the main idea of this thesis. The Cr +:YAG crystal has been operated differently as passive Q-switching and mode-locking medium by researchers at home and abroad.Chapter 2: Researching the Q-switching performance of Cr4+:YAG crystals with the rate equations. In low laser intensity, Cr4+:YAG can be used as slow saturable absorber. The nearer is the initial transparence to the max initial transparence, the bigger is the loss modulation. The experiment with Cr4+:YAG of 30% and 63% initial transparence was conducted in plane-convex unstable resonators and get the laser's FWHM and output energy are accordingly 8ns and 52mJ, 18ns and 45.7mJ. It is proved that the nearer the max initial transparence is the initial transparence, the stronger intensity and smaller FWHM can be obtained Cr4+:YAG crystal, which is consistent with the theoretical results. In addition, the experimental results acquired in different resonator structures and parameters are also analyzed.Chapter 3: Researching the intracavity frequency-doubling of Nd:YAG/Cr4+:YAG Q-switching laser with CLBO crystal. The several factors to affect the frequency doubling conversion efficiency are analyzed theoryretically. The 33.5% and 46.8% frequency doubling conversion efficiency are achieved in plane-concave and dual-concave resonators. The former value is clearly smaller than the latter, because the laser beam radius and the laser beam angle of divergence on the CLBO in the plane-concave resonator is bigger than in the dual-concave resonator.Chapter 4: For the first time achieving the dual-wavelength laser of 1.06m and 1.44m in the designed compound resonator in domestic. The Cr4+:YAG is operated as saturable absorber and laser gaining medium simultaneously. The output energy and FWHM of 1.06 m and 1.44m are 18mJ, 52ns and 0.2mJ, 19ns. The theoretical FWHM of \A4jum laser, which is analyzed theoretically with the pertinent parameters of Cr4+:YAG crystal, is consistent with the experimental results.