A 100W, double-clad, Nd:YAG slab laser

Abstract

Lasers that produce high average power, single longitudinal mode, diffraction-limited output are required for a variety of high precision remote sensing applications. For example, advanced interferometric gravitational wave detectors require ultra-stable 100W-class, single frequency CW Nd:YAG lasers with diffraction-limited output. Lasers for Na lidar and coherent laser radar systems must, in addition, be capable of high peak power, typically 10 mJ in 10-100 ns and produce transform limited pulses. We shall describe a novel end-pumped, side-cooled, double-clad composite slab architecture that is suitable for these high power applications, and which can be injection-locked or injection-seeded to obtain spectral control. The composite structure and end-pumping allow the use of low brightness pump sources and optimizes the gain distribution while minimizing thermal lensing and thermally induced birefringence. The slab supports a folded zigzag laser mode and is side-cooled, with the top and bottom edges temperature controlled. The side-cooling enables power scaling and is achieved without any direct water contact, enhancing reliability. An output power of 103 W using a pump power of 280 W has been achieved, with a slope efficiency of 44%. Interferometric measurements show that the thermal lens is weak, with a focal length of approximately 25 cm at this pump power, and can be changed by adjusting the boundary conditions. We shall report latest results of power scaling and beam quality measurements.