Narrow linewidth pulsed single-frequency fiber laser has the characteristics of excellent coherence and high peak power, and has been widely used in coherent LiDAR, precision measurement and nonlinear frequency conversion. In this work, energy scaling of single-frequency laser with long pulse duration and low repetition rate is demonstrated through leveraging an all-fiber amplifier based on polarization-maintaining (PM) large mode area tapered Yb-doped fiber. With dedicate synchronous pulse pumping for suppressing the inter-pulse ASE effect, and pre-shaping of the seed pulse for compensating the distortion of temporal profile, a 1064nm pulsed single-frequency laser output with an energy of 370mJ is realized with a repetition rate of 100Hz. In addition, the rectangle pulse shape is well maintained with a duration of 1.1ms. It is believed that the obtained result represents the highest energy ever reported for pulsed single-frequency fiber lasers.
A high-power linearly-polarized all-fiber single-frequency amplifier at 1064 nm based on tandem corepumping is demonstrated by adopting large-mode-area (LMA) fiber with core/cladding diameter of 20/130 μm. The output performance of the amplifier dependence on the input signal power has been investigated, and the results indicate that enhancing the injection signal power is advantageous in mitigating the amplified simultaneous emission (ASE) and increasing slope efficiency. A maximum output power of 252 W with corresponding slope efficiency of 85% is achieved with injection signal power of 7 W. At the highest output power status, a polarization extinction ratio (PER) of 17 dB and a beam quality of 1.15 are obtained respectively. In addition, by virtue of LMA fiber and tandem core-pumping, the amplifier exhibits good performance on thermal load, which in turn facilitate the maintenance of frequency noise and linewidth. To the best of our knowledge, this is the highest output power of single-frequency all-fiber amplifier based on core-pumping scheme.
A single-polarization single-frequency (SPSF) 1030 nm distributed feedback (DFB) fiber laser with mode switchable output is achieved. The DFB fiber laser is realized based on a 5 cm long π-phase shifted fiber Bragg grating (PS-FBG). A maximum output power of 84 mW with single-polarization operation is achieved. The polarization extinction ratio (PER) is around 17 dB and the linewidth is 18 kHz. The slope efficiency is 13% and the spectrum at the highest power shows an excellent optical signal to noise ratio of about 75 dB. Moreover, LP11 mode single-frequency lasing is achieved by adopting an acoustically-induced fiber grating (AIFG). The mode purity is estimated to be higher than 96%. These results, to the best of our knowledge, show the highest output power among the reports that achieve single-frequency 1030 nm DFB laser output with single-polarization operation. Furthermore, it is the first time to realize transverse mode switchable single-frequency fiber laser based on an AIFG. The high order mode single-frequency 1030 nm fiber laser has much potential to find applications in multiplexing system.
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.
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