It is the end of year again. I feel obligated to update this blog after a long hiatus. I have been busy as most of the men on the Chinese land do. I don’t have much time to blog, but I do spend some time on setting up a simple website for the research group and updating the new publications. The website has a nice domain name ““.

I wish to continue the guide star laser work. Therefore, we have researched ways to generate linearly polarized Yb doped fiber laser, and are now able to build 100 W class linearly polarized 1120 nm Yb-doped fiber laser with cross-axis-matched FBG pairs written in polarization maintaining fiber. We improved the SBS suppression technique further, and achieved a 44 W single frequency Raman fiber amplifier at 1178 nm with an optical efficiency of 52 %. Up to 25 W at 589 nm has been demonstrated with a home-built frequency doubling cavity, which is not yet optimized.

I feel mode locking of fiber laser fascinating, therefore, we have studied mode locking of Raman fiber laser with graphene absorber. The idea is simple: To achieve wavelength versatile mode locked fiber laser by combining the shared advantage of Raman gain and graphene saturable absorption, both of which is broadband. During the path, we have demonstrated passively Q-switched Yb-doped fiber laser by graphene, and the use of single-multi-single mode fiber structure as bandpass filter for building all fiber tunable dissipative soliton fiber laser.

The SBS suppression technique was applied to single frequency Yb doped fiber laser, and achieved 170 W linearly polarized laser with a 10 micron core PM fiber by 7 time increase of SBS threshold. We also find Yb doped fiber laser at the wing of gain spectrum interesting. One example is a demonstration of high power single frequency 1014.8 nm fiber amplifier working at room temperature for mercury cooling after frequency quadruplication. These works are not yet published.

The research works are on-going. Future update will be posted on the new group website.


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. 🙂