Single-frequency fiber laser has attracted a lot of interest in recent years due to its numerous application potentials in telecommunications, LIDAR, high resolution sensing, atom frequency standard, etc. Phosphate glass fiber is one of the candidates for building compact high gain fiber lasers because of its capability of high-concentration of rare-earth ions doping in fiber core. Nevertheless, it is challenging for the integration of UV-written intra-core fiber Bragg gratings into the fiber laser cavity due to the low photosensitivity of phosphate glass fiber. The research presented in this paper will focus on demonstration of UV-written Bragg gratings in phosphate glass fiber and its application in direct-written short monolithic single-frequency fiber lasers. Strong π-phase shift Bragg grating structure is direct-inscribed into the Er/Yb co-doped gain fiber using an excimer laser, and a 5-cm-long phase mask is used to inscribe a laser cavity into the Er/Yb co-doped phosphate glass fibers. The phase mask is a uniform mask with a 50 μm gap in the middle. The fiber laser device emits output power of 10.44 mW with a slope efficiency of 21.5% and the threshold power is about 42.8 mW. Single-longitudinal mode operation is validated by radio frequency spectrum measurement. Moreover, the output spectrum at the highest power shows an excellent optical signal to noise ratio of about 70 dB. These results, to the best of our knowledge, show the lowest power threshold and highest efficiency among the reports that using the same structure to achieve single-longitudinal mode laser output.
Yb-doped fiber lasers (YDFL) have been one of the most widely studied project in last 10 years due to its
capability in high power output with excellent beam quality. The optical properties of Yb3+ ions in silica glass allow
lasing over wide spectral range from 0.98 to 1.2 μm. Up to now, most of the researches focus on YDFL lasing at
1.06-1.12μm, which is most common wavelength band. Actually YFDL operates at other special wavelength bands
(i.e., 1.17μm or 1.02μm) are widely required in many application fields. In this paper, we will reports the recent
research results of high power YDFL operates at special wavelength. By using Yb3+-doped double-clad silicate fiber
as the gain medium and commercial pigtailed laser diode as the pump source, we have demonstrated (1) an allfiberizied
YDFL operates at 1.12μm, a record output power of 178 W is obtained, the power is further boosted to be
309 W by using one stage of fiber amplifier (2) an all-fiberizied YDFL operates at 1.173 μm, a record output power
of 15.7 W is obtained when the pump power is 28 W. (3) an all-fiberizied YDFL operates at 1.018 μm, a record
output power of 309 W is obtained when the pump power is 435 W.