Research On High Power Pulsed Fiber Laser And The Fiber Laser Pumped Optical Parametric Oscillator

High power pulsed fiber lasers, which draw a lot of attentions in recent years, have become the international research hotspot because of the advantages such as good beam quality, high efficiency, excellent heat dissipation capability, and compactness. Using the high power pulsed fiber laser as the pump source, the PPMgLN-based optical parametric oscillator can achieve high power output in mid-infrared waveband, which can be used in a wide variety of applications such as LIDAR, infrared jamming and optoelectronic countermeasure. In this thesis, the main work is on the development of the high power multi-10ns pulsed fiber lasers and their application on PPMgLN-based optical parametric oscillator. The thesis is composed of the following research work: acousto-optic(AO) Q-switched fiber laser, MOPA structured pulsed fiber amplifier and PPMgLN-based optical parametric oscillator.The AO Q-switched fiber laser was set up with Fabry-Perot cavity structure. Using a large mode area double-cladding fiber as the gain medium, stable Q-switched short pulse high power laser output was achieved. To maintain the laser pulse stable, many factors were considered such as the distance between the AO modulator and the reflect mirror, the length of the active fiber, the pump power and the repetition rate. Using the home-made fiber and the Panda PM fiber from Liekki, we obtained random polarized output power over 12W and linearly polarized output power over 10.5W with pulse duration of 45ns and 33ns respectively.We demonstrated two kinds MOPA structured fiber amplifier; one seeded by a solid state laser and another seeded by a Q-switched fiber laser. Because of the narrow linewidth of the solid state laser, serious nonlinear effect was observed in the fiber amplifier. By adjusting the output power and repetition rate of the seed source, the nonlinear effect could be suppressed. When the pump power exceeded 30.4W, a maximum linearly polarized output power of 20W was obtained. The measured polarization extinction ratio(PER) was greater than 14dB. The fiberized AO Q-switched seed laser has high output power and large linewidth, which is suitable for suppressing the nonlinear effect. This kind fiber amplifier has much higher output power. At the pump power of 40W, a maximum linearly polarized output power of 29.6W was obtained. The measured polarization extinction ratio(PER) was greater than 10dB.PPMgLN-based optical parametric oscillator pumped by MOPA structured fiber amplifier can achieve high output power. A high-energy PPMgLN optical parametric oscillator (OPO) pumped by a E-O Q-switched Nd:YAG laser working at 1.064μm was successfully illustrated. The damage to the input surface of PPMgLN crystal was carefully observed with a damage threshold of 4.6 J/cm~2. When pumped by the solid state laser seeded fiber amplifier, a maximum parametric output of over 8 W was obtained with 2.5 W at 3.16μm. The conversion efficiency of the OPO was computed to be 54% with a slope efficiency of 69%. No saturation phenomenon was observed in the experiment. When pumped by the fiber laser seeded fiber amplifier, a maximum parametric output of over 11.7 W was obtained with 3.3W at 3.16 urn. The conversion efficiency of the OPO was computed to be 51.9% . The saturation phenomenon was observed in this experiment. It is due to the absorption of PPMgLN within the idler wavelength band. To improve the performance of the OPO system, the cavity structure, beamwidth of the pump source and the design of the cooling system must be optimized.