中文摘要：

高增益和抽运光谱宽等因素会使光参量振荡器输出的参量光谱线大幅展宽。通常在腔内插入标准具、光栅等元件以控制谱宽，但会引入损耗，导致激光器输出阈值增大，转换效率和输出功率降低。报道了一种不使用任何谱宽压缩元件获得窄谱宽高功率中红外激光输出的方案。该方案将窄谱宽和高功率分离，分别获取。搭建了1．064μmNd：YAG主振荡功率放大结构的窄谱宽抽运源。通过调节光参量振荡器中PPMgLN晶体内的抽运光功率和光斑直径，实现晶体内增益强度的控制，从而有效控制中红外激光谱宽。在光参量振荡器中，当抽运光功率约为3倍阈值时，获得了0．7W、谱宽小于1．12nm的2．9μm种子光，再通过两级光参量放大器后，最终获得6．27W、光光转换效率15．7％的2．9μm激光输出，谱宽基本保持不变。

英文摘要：

Factors such as high gain and spectral width of pump laser will significantly broaden the output parametric spectra of optical parametric oscillators （OPO）. Etalons, gratings and other components are usually used to control the spectral width, however, loss will be imported, and thus the output threshold of lasers will increase and the conversion efficiency and the output power will decrease. A scheme for obtaining mid-infrared laser with narrow spectral width and high power is reported, in which the spectral width compression components are not used. The proposed scheme obtains narrow spectral width and high power respectively. A narrow-spectral-width pump source with a 1. 064μm Nd： YAG main oscillator power amplifier （OPA） structure is built. By adjusting the power and the diameter of the pump light spot in PPMgLN crystal of the optical parametric oscillator, we can control the gain intensity in the crystal and the spectral width of mid-infrared laser. In the optical parametric oscillator, when the pump power is about three times of the threshold, 0.7 W, 2.9 μm seed laser with spectral width less than 1.12 nm is obtained. The seed light is amplified through two optical parametric amplifiers, and 6.27 W, 2.9 μm laser output is finally obtained, when the light conversion efficiency is 15.7% and the spectral width remains unchanged.