Research On The Optical Bistability Characteristics In LD End-pumped Tm, Ho: YLF Lasers

LD-pumped 2um solid lasers are wildly used in industry, medical treatment and military for its various advantages such as eye-safety, good atmosphere penetration and high efficiency. Optical bistability devices have attracted great attention for their potential applications in many areas such as high-speed optical communication, optical image processing, optical storage and optical logic elements. Therefore, the research on optical bistability characteristics in LD-pumped solid lasers is of great significant in the area of nonlinear optical technique.Optical bistability output phenomenon of Tm,Ho:YLF 2μm laser has been observed in the experiment, but the formation mechanism of the optical bistability has not been well researched theoretically yet. In this dissertation, a self-saturable absorption mechanism for the optical bistability in Tm,Ho:YLF laser is proposed on the basis of detailedly analyzing the particle transition processes and the pump light transmission characteristic in the Tm,Ho:YLF laser crystal. The formation reason and the physical mechanism of the bistability in Tm,Ho:YLF laser is explained. Self-saturable absorption mechanism is an all-optical bistability mechanism, which is due to the quasi-three-level property and the resulting ground state reabsorption (GSR) of the Tm,Ho:YLF laser system.The steady state bistability output characteristics of the Tm,Ho:YLF laser are researched in this dissertation. Based on the self-saturable absorption bistability mechanism, the coupled energy level rate equation model for the optical bistability in Tm,Ho:YLF laser is established. Through the numerical simulation of the bistability rate equation model, the steady state bistability output characteristics of the laser are obtained. The influences of energy transfer upconversion (ETU) and important laser parameters on bistability pump threshold, jump power, and bistability width are detailedly researched, and these parameters include the transmittance of the output mirror, cavity length, Ho3+ doped concentration, crystal temperature, and cavity loss.The dynamic rate equation model of optical bistability in the Tm,Ho:YLF laser is established. The dynamic process of bistability operation in the Tm,Ho:YLF laser are researched through numerically analyzing the dynamic bistability theoretical model, and the physical mechanism of optical bistability is further explained. Through numerically analyzing the dynamic bistability operation, the important time characteristics of the bistability operation are obtained, including the bistability turn-on delay time and the bistability switch time. The influences of the bistability trigger pulse on the time characteristics of the optical bistability are obtained.