High-repetition-rate and high-beam-quality all-solid-state nanosecond pulsed deep-red Raman laser

We report on a high-repetition-rate and high-beam-quality all-solid-state nanosecond pulsed deep-red laser source by intracavity second harmonic generation of the actively Q-switched Nd:YVO₄/KGW Raman laser. The polarization of the 1342 nm fundamental laser was aligned with the Ng and Nm axes of KGW crystal for accessing the eye-safe Raman lasers at 1496 and 1526 nm, respectively. With the aid of the elaborately designed V-shaped resonator and the composite Nd:YVO₄ crystal, excellent mode matching and good thermal diffusion have been confirmed. Under an optimal pulse repetition frequency of 25 kHz, the average output powers of the Raman lasers at 1496 and 1526 nm were measured to be 3.7 and 4.9 W with the superior beam quality factor of M² = 1.2, respectively. Subsequently, by incorporating a bismuth borate (BIBO) crystal, the deep-red laser source was able to lase separately two different spectral lines at 748 and 763 nm, yielding the maximum average output powers of 2.5 and 3.2 W with the pulse durations of 15.6 and 11.3 ns, respectively. The resulting beam quality was determined to be near-diffraction-limited with M² = 1.28.