The Experimental Researches Of Passive Q-switched And Mode-locked Nd: YVO₄/and Cr～(4+): YAG Laser By LD Pumped

In recent years, a diode-end-pumped solid-state laser with high efficiency attract lots of interests. The Nd:YVO₄ crystal was identified as a promising gain medium of the diode-end-pumped solid-state laser because of its many advantages such a high absorption over a wide pump-wavelength bandwidth, a large efficient stimulated emission cross-section. However the capability of heat exchange is bad, so the influence of thermal effect is obvious. So the development of the Nd:YVO₄ crystal is limited in the high power field . How to reduce the thermal effect of crystal is the hot topic of Nd:YVO₄. Cr⁴⁺:YAG crystal was invented in 1988. It is a new type laser crystal in near infrared ray. Its emission range is between 1.3¹.6μm. Cr⁴⁺:YAG crystal has good capability of heat exchange, steady physical and chemical character. It can generate passive Q-switching, passive mode-locking, self mode-locking by continuous or pulsed pumped. Cr⁴⁺:YAG crystal is attractive in light communications, medical applications, laser technology field. The contents can be outlined as follows: (1) introduction. (2) the theoretical researches of the passive Q-switching and passive mode-locking of Nd:YVO₄/Cr⁴⁺:YAG. (3) the experimental researches of passive Q-switched and mode-locked Nd:YVO₄ /and Cr⁴⁺:YAG solid-state lasers by continuous-wave pumped. (4) the experimental researches of passive Q-switched and mode-locked Nd:YVO₄ /and Cr⁴⁺:YAG solid-state lasers by pulse pumped.(1) The history and progress of diode-pumped solid-state lasers are reviewed; and the characters of the diode-end-pumped solid-state laser are presented; the research progress of Q-switch and the theory of Q-switch is introduced. Then several ways of mode-locking and the theory of mode-locking is introduced.(2) The theory of Cr⁴⁺:YAG mode-locking is introduced. Then introducing the characters of Cr⁴⁺:YAG crystal. Based on the speed-rate equations, the condition of Cr⁴⁺:YAG when it operate at Q-switch and mode-locking. Using ABCD matrix, the stable area of cavity in different pumping power when contious-wave is obtained. In theory, the change of radius of the beam on Cr⁴⁺:YAG with different resonance cavity length is calculated. When the pumping power is 8.5W, the stable area of cavity is calculated in different duty cycles. And when the duty cycle is 1:5, the change of radius of beam on Cr⁴⁺:YAG is calculated.(3) When CW pumped and pulse pumped, the experiment pictures are shown about different cavity lengths and duty cycles. Then we explain the experiment results, the experiment condition of Q-switch and mode-locking is given. And how to increase the peak power is analyse.(4) By pulse pumped, Nd:YVO₄/Cr⁴⁺:YAG passive mode-locking and Q-switch is obtained. the experiment pictures are obtained about different cavity lengths and different pumping power. compared it with the experimental result, analysing the experiment result. Changing the conditon of experiment, the expermental result of Cr⁴⁺:YAG with different resonance cavity length and T is compared. The research result is useful.