Power and energy scaling of an acousto-optically Q switched Raman deep-red laser

Nanosecond pulsed deep-red Raman laser based on the Nd:YLF dual-crystal configuration

A highly powerful nanosecond pulsed deep-red laser was demonstrated by intracavity second-harmonic generation of an actively Q-switched Nd:YLF dual-crystal-based KGW Raman laser in a critically phase-matched lithium triborate (LBO) crystal. The first-Stokes fields at 1461 and 1490 nm driven by the 1314 nm fundamental laser were firstly produced by accessing the Raman shifts of 768 and 901 cm-1 in the KGW crystal, respectively, and thereafter converted to the deep-red emission lines at 731 and 745 nm by finely tuning the phase-matching angle of the LBO crystal and carefully realigning the resonator. Integrating the benefits of the Nd:YLF dual-crystal configuration and the meticulously designed L-shaped resonator, this deep-red laser system delivered the maximum average output powers of 5.2 and 7.6 W with the optical power conversion efficiencies approaching 6.3% and 9.2% under the optimal pulse repetition frequency of 4 kHz, respectively. The pulse durations of 6.7 and 5.5 ns were acquired with the peak powers up to approximately 190 and 350 kW, respectively, and the resultant beam qualities were determined to be near-diffraction-limited with M2 ≈ 1.5.

Ten-watt-level all-solid-state eye-safe intracavity Raman laser

We demonstrate the first ten-watt-level eye-safe intracavity crystalline Raman laser, to the best of our knowledge. The efficient high-power eye-safe Raman laser is intracavity-pumped by an acousto-optically Q-switched 1314 nm two-crystal Nd:YLF laser. Benefiting from the unique bi-axial properties of KGW crystal, two sets of eye-safe dual-wavelength Raman lasers operating at 1461, 1645 nm and 1490, 1721nm are achieved by rotating the Raman crystal. Under the launched pump power of 84.9 W and the repetition rate of 4 kHz, the maximum first-Stokes output powers of 7.9 W at 1461 nm and 8.2 W at 1490 nm are acquired with the second-Stokes output powers of 1.4 W at 1645 nm and 1.5 W at 1721nm, respectively, leading to the eye-safe dual-wavelength Raman output powers of up to 9.3 and 9.7 W. Meanwhile, the pulse durations at the wavelengths of 1461, 1490, 1645, 1721nm are determined to be 4.8, 5.5, 4.3, and 3.6 ns, respectively, which give rise to the peak powers approaching about 410, 370, 80, 100 kW. These Stokes emissions are found to be near diffraction limited with M2 < 1.6 across the entire output power range.

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.

High-power diode-end-pumped 1314 nm laser based on the multi-segmented Nd:YLF crystal

We demonstrate the first multi-segmented Nd:YLF laser, to the best of our knowledge. The multi-segmented crystal was designed to straightforwardly aim for the minimum thermal stress without sacrificing the overall laser efficiency, with the influence of the pump beam waist position considered in particular. Integrating the enhanced thermo-mechanical resistance of multi-segmented crystal and the alleviated heat load of low quantum defect pumping, this end-pumped 1314 nm Nd:YLF laser system delivered a maximum continuous-wave output power of up to 35.5 W under a pump power of 105 W, corresponding to an optical-to-optical efficiency of 33.8%. Furthermore, by incorporating an acousto-optic modulator, an active Q-switching oscillator was accomplished, yielding a maximum average output power of 22.9 W at a pulse repetition frequency (PRF) of 20 kHz and a largest pulse energy of 13.6 mJ at a PRF of 1 kHz.

Wavelength-versatile deep-red laser source by intracavity frequency converted Raman laser

We demonstrate an efficient wavelength-selectable output in the attractive deep-red spectral region from an intracavity frequency converted Nd:YLF/KGW Raman laser. Driven by an acousto-optic Q-switched 1314 nm Nd:YLF laser, two first-Stokes waves at 1461 and 1490 nm were generated owing to the bi-axial properties of KGW crystal. By incorporating intracavity sum-frequency generation and second-harmonic generation with an angle-tuned bismuth borate (BIBO) crystal, four discrete deep-red laser emission lines were yielded at the wavelengths of 692, 698, 731, and 745 nm. Under the incident pump power of 50 W and the repetition rate of 4 kHz, the maximum average output powers of 2.4, 2.7, 3.3, and 3.6 W were attained with the pulse durations of 3.4, 3.2, 4.3, and 3.7 ns, respectively, corresponding to the peak powers up to 177, 209, 190, and 245 kW. The results indicate that the Nd:YLF/KGW Raman laser combined with an angle-adjusted BIBO crystal provides a reliable and convenient approach to achieve the selectable multi-wavelength deep-red laser with short pulse duration and high peak power.