【摘要】 报道了一种基于光谱合束的Nd:YAG固体激光器双波长光源。系统由两个固体Nd:YAG脉冲激光器通过光谱合束组合而成，两个固体Nd:YAG脉冲激光器可独立工作，有利于输出脉冲的波长调谐、功率调节和相对延迟调整。通过光栅的色散特性以及输出镜的共同外腔反馈将各个激光器锁定在不同波长，从而实现合束，获得的激光源中心波长锁定在1 061.5 nm和1 064.6 nm，两谱线中心间距为3.1 nm，组合光束的输出能量为173 mJ，组合光束的光束质量因子M~2为2.8×2.2；两个Nd:YAG激光器独立工作的输出能量分别为94 mJ和92 mJ，在合束方向上的光束质量因子M~2分别为2.7和2.1，在非合束方向上的光束质量因子M~2分别为2.2和1.9；组合光束的输出能量为两个Nd:YAG激光器能量总和的93%，组合光束的光束质量因子与单个Nd:YAG激光束的光束质量因子M~2基本相同。该双波长激光源满足波长间隔小、输出功率大小相近、同光轴等要求，在太赫兹波产生、测速激光雷达以及医疗仪器等应用领域具有重要作用。更多还原

【Abstract】 Objective Solid-state lasers pumped by diode lasers have the advantages of small size, long lifetime, high efficiency, high energy and good beam quality because of the high emission cross section and the matching of the emission and the absorption spectral line. In particular, diode-pumped dual-wavelength solid-state lasers are attractive for environmental monitoring, laser radar for velocity measurement, medical instruments, holography,and terahertz generation. In addition to dual wavelengths, the following laser characteristics are required for these applications. The wavelength spacing between the two lasers must be small enough to generate terahertz waves;The two beams must have nearly equal power; The relative timing of the output pulses must be controllable, so that the output pulses can be in synchrony or in succession; The two beams must be coincident and the wavelengths must be tunable. For this purpose, a dual wavelength excimer based on spectral beam combining(SBC) is designed in this paper.Methods SBC comes from the principle of wavelength division multiplexing semiconductor laser transmitters used in communications(Fig.1). Beam combining was achieved using a common external cavity containing a grating, which simultaneously forces each Nd:YAG laser to operate at a different controlled wavelength and forces the beams from the two lasers to coincide. The lasers are arranged in a line at the focal plane of a transform lens. The collimated beams overlap at the grating and the output coupler. The common external cavity forces the beams to copropagate, and each laser has a different wavelength.Results and Discussions The spectrum of the combined beam shows the wavelength spread is 3.1 nm(Fig.3).At a maximum current of 200 A, the pulse energy of Laser 1 is 94 mJ and Laser 2 is 92 mJ before beam combining. The pulse energy of the combined beam is as high as 173 mJ, which corresponds to a combining efficiency of 93%(Fig.4). In the horizontal direction(beam combining direction), the M~2 is 2.7 and 2.1 for Laser 1and Laser 2 before beam combining. The M~2 of the combined beam in the horizontal direction is 2.8. In the vertical direction(no beam combining direction), the M~2 is 2.2 and 1.9 for Laser 1 and Laser 2 before beam combining respectively. The M~2 of the combined beam in the vertical direction is 2.2(Fig.5).Conclusions In summary, we have reported a dual-wavelength laser source by SBC of two solid-state Nd:YAG lasers. The resultant output beam quality is similar to that from a single laser. For the combined beam, a pulse energy of 173 mJ, and a combining efficiency of 93% are obtained. We believe that SBC could also be applied to an actively Q-switched Nd:YAG laser to obtain ns pulse durations and higher peak powers. Furthermore, because of the existence of additional transitions of Nd3+: YAG, it is expected that four or more lasers with different wavelengths(e.g., 1 052 nm, 1 061 nm, 1 064 nm, and 1 072 nm) can be combined in the future.更多还原