High power UV lasers employing elliptically focusing enhancement cavities.

Abstract

Continuous wave UV lasers have a plethora of applications in many fields, among others, laser spectroscopy, atom trapping, and other related areas. We present a high power continuous wave UV laser system based on twofold second harmonic generation of IR radiation for cooling bunched relativistic ion beams and laser spectroscopy with an output power exceeding 2.4 W in the UV range. Laser operation in the UV regime is often limited by degradation of β-barium borate (BBO) due to two-photon absorption (TPA). We were able to overcome this issue with a novel design of an elliptically focusing enhancement cavity employing commercially available BBO as the nonlinear medium. Building on previous results, we implemented a novel elliptically focusing enhancement cavity featuring an extreme waist ratio of w0,sag/w0,tan = 27.5 at the center of the BBO crystal, aiming to further reduce the peak intensity. This paper details the results as well as our advanced locking scheme for the enhancement cavities for both second harmonic generation steps.