Optical Parametric Oscillator At 1.57 μm Eye-safe Wavelength

1.57μm eye-safe wavelength lasers, because of their advantages such as eye -safe ,all-weather operation, pass through smoke and so on, are vital for applications in the field of military involving photoelectricity counterwork,laser rangefinder , scout , obstacle avoidance and etc. Especially the 1.57μm lasers obtained by technology of optical parametric oscillator, have become a central of focus in the fields of laser process ,surgical ,laser radar ,laser-guided and so on due to their many advantages, such as higher conversion efficiency, compactness and higher pulse repetition rate and etc. This dissertation presents results of theoretical and experimental researches on optical parametric oscillator at 1.57μm eye-safe wavelength. The contents can be outlined as follows:1. The history and development of optical parametric oscillator are reviewed. The main approaches and new results of eye-safe wavelength KTP-OPO at present are summarized,The advantages of optical parametric oscillator at 1.57μm eye-safe wavelength are introduced.2. Introducing the theory of nonlinear wavelength transform technology, second nonlinear polarization frequency transform and the coupling equations of three nonlinear frequencies mixing. The theory of optical parametric oscillator is summarized.3. Analyzing the characters of laser crystals of Nd:YVO₄ and Nd:GdVO₄.The output characters of LD pump acoustic-optical Q-switched Nd:YVO₄ 1064nm laser is investigated by experiments.4. Two efficient, eye-safe wavelength, intracavity single-resonance optical parametric oscillators, based on a type II non-critical phase-matched KTP crystal, inside a Q-switched laser end pumped by a fiber-coupled diode laser are demonstrated. When the incident pumping power was 6.33W, we obtained 405mW 1.57μm eye-safe wavelength at 15 kHz repetition rate with pulse duration of 2.5ns and peak power of 10.8kW. And minimum of pulse duration of 2ns has been obtained at 5 kHz repetition rate.5. The characters and the angle phase matching of the new type KTA crystal are introduced .The intracavity optical parametric oscillator based on a KTA crystal inside an acoustic-optical Q-switched Nd:YVO₄ laser end pumped by a fiber-coupled diode laser are demonstrated. When the incident pumping power was 6.35W, 424mW 1.57μm eye-safe wavelength was obtained at 20 kHz repetition rate with pulse duration of 2.5ns and peak power of 8.48kW.