Abstract
We report the generation of 28 W of 780 nm radiation with near diffraction limited beam quality (M2 ≤ 1.15) by frequency-doubling a continuous-wave erbium fiber master oscillator power amplifier system in a periodically poled lithium niobate crystal. The second-harmonic generation conversion efficiency reached 45% with no roll-off observed, suggesting that further power scaling should be possible with higher fundamental pump powers. The generated second-harmonic had a 3 dB spectral bandwidth of 0.10 nm. The presented architecture represents a simple and effective route to generating high-brightness radiation around 780 nm.
Highlights
H IGH average-power continuous-wave (CW) radiation around 780 nm with near diffraction-limited beam quality is required for a variety of scientific applications, such as spectroscopy, laser cooling of atoms [1] and the pumping of alkali gas-vapor lasers [2]
At 775 nm, an average-power of 41 W has been generated in a periodically poled potassium titanyl phosphate (PPKTP) crystal with a conversion efficiency of 72% using nanosecond pulses [13]. These results are encouraging for high average-power CW Second harmonic generation (SHG) in periodically poled crystals but to date, the highest reported CW power is 19 W at 532 nm using periodically poled lithium tantalate (PPLT) [14], [15]. In this manuscript we report the generation of 28 W of near diffraction limited (M2≤1.15) CW light at 780 nm by frequency-doubling an Er:fiber master oscillator power amplifier (MOPA) system in a periodically poled lithium niobate (PPLN) crystal
We attribute this decline in the rate of the SHG conversion efficiency increase to the onset of thermal issues caused by the absorption of the generated SH in the PPLN crystal
Summary
H IGH average-power continuous-wave (CW) radiation around 780 nm with near diffraction-limited beam quality is required for a variety of scientific applications, such as spectroscopy, laser cooling of atoms [1] and the pumping of alkali gas-vapor lasers [2]. Direct laser emission can be obtained at this wavelength by semiconductor laser diodes and a variety of solid-state gain media but scaling the diffractionlimited average-power of these lasers to multiple tens of Watts remains challenging. Of the solid-state gain media available in this wavelength region, Ti:Sapphire is by far the most widespread and commercially mature. Argon-ion laser pumped Ti:Sapphire systems have been demonstrated with CW powers reaching 43 W, but cryogenic cooling of the two laser crystals was required to alleviate thermally induced optical distortions in the laser rods [4]
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