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高增益和泵浦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、光栅等元件对谱宽进行控制，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。本文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的方案。该方案把窄谱宽和高功率相分离，分别获取。搭建了 1.064 μm Nd:YAG 主振荡功率放大（MOPA）结构的窄谱宽泵浦源。通过调节光参量振荡器中 PPMg LN 晶体内的泵浦光功率和泵浦光光斑的直径，实现晶体内增益强度的控制，从而实现了对中红外激光谱宽的有效控制。在光参量振荡器中，当泵浦功率约为 3 倍阈值时，获得了 0.7 W，谱宽小于 1.12 nm 的 2.9 μm 种子光。通过两级光参量放大器后，最终获得 6.27 W，光光转换效率 15.7%的 2.9 μm 激光输出，谱宽基本保持不变。
Factors such as high gain and wide pump spectrum will widen the parametric spectral line output by the optical parametric oscillator. Usually inserted in the cavity etalon, grating and other components to control the spectral width, but will introduce loss, resulting in increased laser output threshold, the conversion efficiency and output power decreases. This paper reports a scheme to obtain a narrow-band, high-power, mid-infrared laser without any spectral width compression element. The scheme separates the narrow spectrum width and the high power separately and acquires them respectively. A narrow bandwidth pump source with a 1.064 μm Nd: YAG main oscillator power amplifier (MOPA) structure was constructed. By adjusting the pump light power and pump light spot diameter in the PPMg LN crystal in the optical parametric oscillator, the gain intensity in the crystal can be controlled, and the wide control of the laser spectrum can be realized. In the optical parametric oscillator, when the pump power is about 3 times the threshold, 0.7 W seed light with a spectral width of less than 1.12 nm is obtained. After passing through two stages of optical parametric amplifiers, a 2.9 μm laser output of 6.27 W and a light conversion efficiency of 15.7% was finally obtained, and the spectral width remained basically unchanged.