Fangpei Zhang

High power coherent beam combination from two fiber lasers

Phase locking of two fiber lasers is demonstrated experimentally by the use of a self-imaging resonator with a spatial filter. The high-contrast interference strips of the coherent beam profile are observed. The coherent output power of the fiber array exceeds 12W and the efficiency of coherent power combination is 88% with pump power of 60W. The whole system operates quite stably and, for the spatial filter, no thermal effects have been observed, which means that we can increase the coherent output power further by this method.

Stable pulse-compressed acousto-optic Q-switched fiber laser

A novel acousto-optic switch operation by a simple laser-diode pumped acousto-optic, Q-switched, ytterbium-doped, double-clad fiber laser is reported. Stable compressed Q-switched sub-40 ns pulses with a beam quality factor (M(2)=2) are achieved at the repetition rate of 1-50 kHz. Q-switched pulses of ~20 microJ pulse energy and 35 ns pulse width are obtained at the repetition rate of 50 kHz. Finally, a reasonable explanation of the novel Q-switched operation is presented.

High-Repetition-Rate MHz Acoustooptic

A simple actively Q-switched double-clad fiber laser combining an amplifying cavity is reported by using a dynamic acoustooptic Q-switching as a beam splitter. Sub-100-ns pulses independence of the repetition rate of acoustooptic modulator are almost changeless with repetition rate varied from 50 kHz to 1.5 MHz. With 4.5-W absorbed power, 9.4-W peak-power pulses at 1.5-MHz repetition rate with 75-ns pulse duration are generated.

Q

A pulsed master-oscillator fiber power amplifier system with near diffraction-limited output by use of China-made large-mode-area fiber and a (2+1)×1 multimode combiner is reported. The effect of the seed power on the amplification performance is found. For the seed power, there exists a range within which the pulsed fiber amplifier can operate safely and reliably at a certain pump power. With the seed average power of 70 mW, the amplification performances of the fiber amplifier are investigated.

-Switched Fiber Laser

The authors report stable short high-repetition-rate Q-switched pulses in acousto-optic Q-switched ytterbium-doped double-clad fiber lasers. This device uses a diode pumped at 975 nm to end pump the large mode area double-clad fiber laser. In the experiment acousto-optic modulator is used as a special Q-switching in the F-P cavity. As a result, sub 100 nanosecond pulses are obtained with varying the acoustic-optic repetition rate from 1 kHz to 100 kHz. The Q-switching technique provides a novel method to generate short pulses at high repetition rate.

Impacts of seed power on amplification performance in pulsed double-clad fiber amplifier

A narrow-linewidth master-oscillator fiber power amplifier system with homemade large-mode-area fiber is demonstrated. Some fundamental characteristics of this system, including the output power characteristics, the emission spectrum characteristics, as well as the confirmation of single-frequency operation are investigated in detail. The system generates up to 7.3 W of single-frequency radiation at a wavelength of 1064 nm with 39% slope efficiency and 26% optical-optical power conversion efficiency.