Research News

Diamond guide star laser

The physical properties of CVD diamond make it excellent medium for high average power Raman laser generation. We have been thinking of using diamond to generate sodium guide star lasers. In the past few years, we have been cooperating with Prof. Mildren’ group at Macquarie Universty on fiber laser pumped diamond Raman lasers. A particular interest is to develop a new diamond Raman guide star laser technology, an important alternative to the already developed fiber Raman technology. Recently, we have made breakthough in this topic, thanks to the hard work of Mr. Xuezong Yang, who is a Ph.D. student jointly suported by UCAS and MU. The results was published on Optics Letters:

Xuezong Yang, Ondrej Kitzler, David J. Spence, Zhenxu Bai, Yan Feng, and Richard P. Mildren, “Diamond sodium guide star laser,” Opt. Lett. 45, 1898-1901 (2020)

Abstract: Laser guide stars based on the mesospheric sodium layer are becoming increasingly important for applications that require correction of atmospheric scintillation effects. Despite several laser approaches being investigated to date, there remains great interest in developing lasers with the necessary power and spectral characteristics needed for brighter single or multiple guide stars. Here we propose and demonstrate a novel, to the best of our knowledge, approach based on a diamond Raman laser with intracavity Type I second-harmonic generation pumped using a 1018.4 nm fiber laser. A first demonstration with output power of 22 W at 589 nm was obtained at 18.6% efficiency from the laser diode. The laser operates in a single longitudinal mode (SLM) with a measured linewidth of less than 8.5 MHz. The SLM operation is a result of the strong mode competition arising from the combination of a spatial-hole-burning-free gain mechanism in the diamond and the role of sum frequency mixing in the harmonic crystal. Continuous tuning through the Na D line resonance is achieved by cavity length control, and broader tuning is obtained via the tuning of the pump wavelength. We show that the concept is well suited to achieve much higher power and for temporal formats of interest for advanced concepts such as time-gating and Larmor frequency enhancement.

Research News

In the past five years…

It is already five years that I blogged nothing here. Just give a short outlines here to show the main research achievements.

We have improved and maturized the Raman fiber amplifier based guide star lasers. The laser can now operate at CW, 100 microsecond quasi-CW, and pulsed at Larmor frequency. Laser prototypes were tested at telescopes for sodium guide star, and also for mesospheric magnetometry.

With cascaded random Raman fiber laser, we have demonstrated up to 11 th Raman Stokes light generation. With a Yb pump laser at 1 micron, continuous wavelength tuning up to 2 micron were demonstrated. With this technology, fiber lasers can now output more than 100 W at any wavelength from 1030 nm to 2000 nm.

We continued our study on mode locked Raman fiber lasers, have made some interesting demonstrations including NPR mode locked dissipative soliton, figure of 8 dissipative soliton, rectangular pulse generation etc. We believe we have improved the understanding of mode locked Raman fiber lasers now.

Amplified spontanesou emission sources were found to be useful for pumping cascaded random Raman fiber lasers and mode locked Raman fiber lasers.

Specialty lasers at various wavelengths were demonstrated with wavelength tuning of fiber lasers and second harmonic generations.

Besides, we have made contributions in scattered topics. Many of them are actually more interesting and look for futher developments. Check out our publication list.

Research News

Update in 2013

In 2013, we continued our studies on Raman fiber laser/amplifier and mode locked fiber laser, and development of lasers for guide star and cold atom physics.

We found a method for power scaling of single mode linearly polarized Raman fiber laser. In a proof of principle experiment, an output power of 300 W has been achieved, limited by available power. In the single frequency Raman fiber amplifier direction, we have achieved more than 80 W at 1178 nm in the CW case and more than 120 W in the QCW long pulse case. Consequently, after frequency doubling, more than 50 W CW and 80 W QCW (peak power) laser at 589 nm have been demonstrated. With these results, we are confident that power scaling of Raman fiber amplifier based guide star laser to over 100 W is feasible.

We are always interested in applying our expertise in wavelength flexible high power narrow linewidth fiber amplifier to atomic physics. In this year, we have scale the room temperature 1014.8 nm single frequency fiber amplifier to ~ 20 W, and carried out the frequency doubling and quadrupling experiment to 253.7 nm, and absorption and Doppler-free absorption spectral measurement of mercury atoms.

Together with Prof. Gu of Ryerson University, we also studied mode locked Yb fiber lasers with chirped FBGs, and demonstrated dual wavelength switchable dissipative soliton fiber laser and studied the effect of large normal and anomalous dispersion.