High frequency-reproducibility nanosecond pulsed laser with high output power

This paper reported a high frequency-reproducibility high-power single-longitudinal-mode (SLM) pulsed laser which was achieved by combining an etalon set, a pre-lasing process and a nonlinear optical frequency conversion (NOFC). The NOFC was used to rapidly enlarge the loss difference between the dominant mode and sub-modes. Then, the pre-lasing process was introduced before the pulse build-up to enhance the dominant-mode intensity. On this basis, an etalon set was inserted into the resonator to select a reference frequency. As a result, the frequency reproducibility between pulses was significantly improved. In the experiment, a type-I phase-matched LBO was used to introduce the NOFC. When the pre-lasing process was introduced by slightly lowering the loss induced by the Q-switch, the spectral width of the 1064 nm laser was narrowed from 32.80 pm to 14.40 pm, and the wavelength drift was improved from less than 1.20 pm to less than 0.36 pm. On this basis, the spectral width was further narrowed to 2.20 pm by improving the frequency reproducibility between pulses through employing an etalon set with thicknesses of 0.5 mm, 1 mm and 10 mm, and the wavelength drift was less than 0.07 pm.