.1.57 ¦¬m In Eye-safe Optical Parametric Oscillator

The 1.06μm lasers which are being broadly used in modern photoelectric devices tend to hurt people's eyes. In view of this, many scientists are trying work out novel lasers at eye-safe wavelengths. The lasers whose output wavelength is near 1.57 μm are widely used in range-finding because of they are relatively safe to people's eyes. Optical Parametric Oscillator (OPO) pumped by 1.06μm Nd:YAG laser outputs at 1.57μm and is one of the most effective way to realize the eye-safe laser.OPO as a kind of high coherence tunable laser source has been attracting many researchers for its unique characters. Recently, with the development of nonlinear frequency conversion crystal (NFCC) and solid-state laser technology, research activities in this area are heating up. The research on KTP-OPO system lasing at 1.57μm eye-safe wavelength is one of the favorite topics. By using a type IInoncritically phase-matched (x-cut, 6 = 90°. φ = 0°) singly resonant KTP-OPOsystem, laser at 1.57μm can be achieved. In this thesis, an eye-safe 1.57μm KTP-OPO pumped by a Cr~4+:YAG passively Q-switched Nd:YAG laser is theoretically and experimentally studied, and finally a compact eye-safe laser device is developed. The contents of dissertation can be outlined as follows:1. The fundamental theory and general research on OPO system are introduced. The applications of OPO system in many fields are discussed.2. By utilizing coupled wave equations of three-wave interaction process, the theory of OPO system is studied and some key parameters such as pump threshold and conversion efficiency are analyzed. The fundamental principle of OPO construction is summarized.3. By using Xenon flash as the pump source, the static and Cr4+:YAG Q-switched performance of Nd:YAG laser is studied and working condition for single-pulse oscillation is established.4. By using Xenon flash pumped, Cr4+:YAG Q-switched Nd.YAG cavity as thepump source, an intracavity KTP-OPO system lasing at 1.57 u m wavelength is realized. Output performance for different Cr4+:YAG small signal transmissions and different 1.57 u m output transmissions is demonstrated. Single pulse and multi-pulse output is observed. Working conditions for single-pulse and multi-pulse parametric oscillation are established.5. On the basis of the 1.06 u m Nd: YAG laser cavity which is used for range-finding, a 1.57 u m fold-cavity KTP-OPO laser system is realized as range-finding light source. The OPO system has stable output under different temperature conditions and meets the rigid demands for range-finding source. The OPO system is expected to be used in real applications.6. For the first time, a KTP crystal, whose entrance face is AR (anti-reflectance) coated at 1.06 v m and HR (high-reflectance) coated at 1.57um, is utilized in the KTP-OPO system so that a cavity mirror can be saved. The decrease in the number of tunable elements in the optical route is expected to improve the anti-impact performance of the KTP-OPO system.