Single-frequency continuous-wave solid-state 363.8-nm ultraviolet source generation by frequency tripling of a 1091-nm fiber laser

Abstract

A single-frequency continuous-wave (CW) ultraviolet (UV) solid-state source at 363.8 nm has been demonstrated through the frequency tripling of a high-power, single-frequency, linearly-polarized (LP) 1091-nm laser. This 1091-nm laser, which features a homemade single-frequency distributed Bragg reflector (DBR) seed and can deliver 78-W average power with an optical signal-to-noise ratio (OSNR) exceeding 63 dB and a polarization extinction ratio (PER) of ∼ 15.8 dB. Employing two cascaded periodically poled Mg-doped lithium niobate (PPMgLN) crystals, whose lengths are 30 mm and 20 mm, a single-frequency 545.5-nm source with an average power of 1.85 W and a single-frequency 363.8-nm source with an average power of higher than 20 mW were obtained, when the input power of the 1091-nm laser was just 11.78 W. To the best of our knowledge, this is the first single-frequency solid-state UV source at 363.8 nm, which is usually provided by argon-ion gas laser, thus offering a potential alternative for semiconductor chip inspection applications.