主振荡功率放大激光器中锥度光纤相位共轭镜的实验研究

锥度光纤作为相位共轭镜具有高反射率、高保真度等优点，将3根自制的、规格不同的锥度光纤相位共轭镜应用在重复频率100Hz，脉宽28ns的激光二极管(LD)抽运的高功率脉冲激光主振荡功率放大器(MOPA)系统中，对其受激布里渊散射(SBS)性能以及锥度区尺寸的影响进行了研究。结果表明，芯径大于400μm的大尺寸锥度光纤可以应用于高功率激光系统中，如选择较长的后端光纤长度以及适当的锥度区规格可获得较高的受激布里渊散射能量反射率和输出能量。在应用总长5．2m，锥度区从φ400μm过渡到φ200μm的锥度光纤时，实验获得了高达85％的受激布里渊散射能量反射率和大于21mJ的双通输出能量，激光脉宽被压缩到17ns，最大峰值功率达到兆瓦量级。

Experimental Study on Optical Tapered Fiber Phase-conjugator in MOPA System

The tapered fiber as phase conjugator has the merits of high stimulated Brillouin scattering (SBS) reflectivity and high fidelity. In this paper, three self-designed tapered fibers with different dimensions were applied in a laser diode (LD) pumped high-power master oscillator power amplifier (MOPA) laser system operated at 100 Hz repetition-rate and 28 ns pulse width. Their SBS performances and influences of taper size on fiber phase-conjugator were experimentally studied. The results demonstrated that tapered fiber with core more than ?? 400 μm can be used in high-power laser system, while higher output energy and SBS reflectivity can be achieved by using a fiber phase conjugator with optimum taper size and larger fiber length of thinner side. Appling a 5.2 m-long tapered fiber with taper from ?? 400 μm down to ?? 200 μm, 85% energy reflectivity and 21 mJ output energy of double-pass can be obtained. The pulse width was compressed up to 17 ns, the peak power reached to MW.