50 W CW 589nm laser

50W CW visible laser source at 589nm obtained via frequency doubling of three coherently combined narrow-band Raman fibre amplifiers

Luke R. Taylor, Yan Feng, and Domenico Bonaccini Calia

Optics Express, Vol. 18, Issue 8, pp. 8540-8555 (2010) doi:10.1364/OE.18.008540

Abstract: We demonstrate the cascaded coherent collinear combination of a seed-split triplet of 1178nm high-power narrow-band (sub-1.5MHz) SBS-suppressed CW Raman fibre amplifiers via nested free-space constructive quasi-Mach-Zehnder interferometry, after analysing the combination of the first two amplifiers in detail. Near-unity combination and cascaded-combination efficiencies are obtained at all power levels up to a maximum P1178 > 60W. Frequency doubling of this cascaded-combined output in an external resonant cavity yields P589 > 50W with peak conversion efficiency η589 ~85%. We observe no significant differences between the SHG of a single, combined pair or triplet of amplifiers. Although the system represents a successful power scalability demonstrator for fibre-based Na-D2a-tuned mesospheric laser-guide-star systems, we emphasise its inherent wavelength versatility and consider its spectroscopic and near-diffraction-limited qualities equally well suited to other applications.

This work was to demonstrate the scalability of the Raman fiber amplifier approach. As one can imagine, we had worked hard to break the published record power of 50 W by the Starfire people. 🙂


Breakthrough in guide star laser development

The Messenger is a quarterly journal presenting ESO‘s activities to the public. It has rather wide readership in the astronomy community. In the 2010 March issue, we have an article summarizing the development of Raman fiber amplifier based guide star laser at ESO.

Laser Development for Sodium Laser Guide Stars at ESO

Bonaccini Calia, D.; Feng, Y.; Hackenberg, W.; Holzlöhner, R.; Taylor, L.; Lewis, S.

Abstract: A breakthrough in the development of sodium laser guide star technology at ESO was made in 2009. The laser research and development programme has led to the implementation of a narrowband Raman fibre laser emitting at the wavelength of the sodium lines at 589 nm with demonstrated power beyond 50 W. Fibre lasers are rugged and reliable, making them promising candidates for use in the next generation of laser guide star systems, such as the Adaptive Optics Facility planned for installation on VLT UT4 in 2013.

The full article can be downloaded here.