We present studies of mixed

A stable, continuous wave, single frequency ber ampli er large mode double clad ber cooled to liquid nitrogen temper ampli ed light is frequency quadrupled to 254 nm and used for mode, plane-polarized ytterbium-doped ber master oscillator power ampli er source with 264 W of output Erbium-Doped Fiber Ampli ers: Principles and Applicationoped large-core ber laser with 1.36 kW continuous-

We present a high power single-frequency ytterbium fiber amplifier system with an output power of 30 W at 1091 nm. The amplifier system consists of two stages, a preamplifier stage in which amplified spontaneous emission is efficiently suppressed (>40 dB) and a high power amplifier with an efficiency of 52%. Two different approaches to frequency doubling are compared. We achieve 8.6 W at 545.5 nm by single-pass frequency doubling in a MgO-doped periodically poled stoichiometric LiTaO3 crystal and up to 19.3 W at 545.5 nm by frequency doubling with a lithium-triborate crystal in an external enhancement cavity.

We demonstrate a reliable continuous-wave (cw) laser source at the 1 S-2 P transition in (anti)hydrogen at 121.56 nm (Lyman-α) based on four-wave sum-frequency mixing in mercury. A two-photon resonance in the four-wave mixing scheme is essential for a powerful cw Lyman-α source and is well investigated.