[en] The polarization characeristics of the all fiber front-end for a laser facility prototype were analyzed. According to the polarization control demand of the laser facility prototype, a new method was developed to stablize the polarization of the fiber system with narrow bandwidth and short-pulse output. The amplitude modulator of the fiber system was pulse-biased and the auto-stabilizaion of the fiber system polarization was obtained by on-line detecting the polarization state of CW laser leakage from the amplitude modulaor. The decrease of the extinction ratio of the amplitude modulator in longtime operation was restrained and the stability of the all fiber front-end system was improved to 2.9%. (authors)

[en] The laser pulse waveform real-time precision measurement technology based on time division multiplexing (TDM) was developed for all fiber multi-beam high repetition frequency laser system. According to the characteristic of the system, we designed a kind of 1 × 8 optical time division multiplexer and a kind of 1×2 optical time division multiplexer with different time delay. Also we experimentally demonstrated the technology in the system, the results show that the pulse duration, pulse energy and rise time could be accurately measured, and meanwhile the system working status could be inspected in real time. (authors)

[en] In this paper, we demonstrate an all-fiber high-power Yb-doped 1030 nm fiber laser based on master oscillator power amplifier structure. The record output power at 1030 nm up to 3004 W was achieved, along with a slope efficiency of 69.27%, which is the highest output power for 1030 nm near diffraction limited beam quality fiber laser. The beam quality factor is M_x² = 1.169, M_y² = 1.174, and full width at half maximum is 0.18 nm at maximum power level. The amplified spontaneous emission (ASE) suppression ratio reaches up to 37 dB. (authors)

[en] The broadband nanosecond shaped laser pulse obtained by chirped pulse stacking(CPS) method can make the out-put stacked pulse meet the requirement of the inertial confinement fusion(ICF). However, temporal pulse shape modulation will come forth due to the pulse coherence of stacked chirped pulses, so will spectrum modulation. Factors influencing stacked chirped pulse waveshape and characteristics of the amplification process of stacked chirped pulse were studied. Results show that the evolution law of stacked chirped pulses is consistent with that of narrow band pulses, and the time modulation structure does not change in the amplification process. However, the spectrum modulation changes, which could be preliminarily inferred from the nonlinear effect. The stacked chirped pulse has a gain ability comparable to that of the narrowband pulse. (authors)

[en] In recent years, fiber laser has been developing rapidly, and gradually applied in many fields. Further improvement of output power is still the research hotspot of fiber laser. Beam combining is an important method to scale output power of fiber laser. Beam combining requires that the sub beam is a narrow linewidth fiber laser, so the research of narrow linewidth fiber laser is of great significance for power improvement. In this paper, the development and research status of narrow linewidth high power fiber lasers are introduced in detail, and based on the current research status, the future development trend is prospected. (authors)

[en] A power fiber amplifier module consisting of two stage fiber amplifiers,whose fiber core diameters were 15 μm and 25 μm respectively, was presented. It can output 30 kW peak power with 300 μJ output energy, when the input pulsed signal is 10 ns in duration, 1 Hz in repetition frequency, 0.3 nm in spectrum width, and 80 nJ in energy. The output pulse's temporal characteristic was investigated. It is found that the output energy of the amplifier module is confined by stimulated Brillouin scattering (SBS) effect when the input pulse is narrow banded, and adopting the broadband pulse could improve the SBS threshold of the fiber amplifier. (authors)

[en] Supercontinuum spectrum has wide applications in many fields, and it was one of the hottest research directions the past twenty years. However, limited by the mismatch of mode area between pig-tail of amplifier and the photonic crystal fiber and the balance of peak power and output power of the amplifier, the power of white-light supercontinuum is about 200 W. Based on frequency repetition and pulse duration of the amplifier and the high-efficient match of mode area, 563 W high power all-fiber white-light supercontinuum source was generated. (authors)

[en] The transmission characteristics of phase modulation pulse transmitted through the filter in the power amplifier are investigated theoretically and experimentally. The narrow bandpass filter can induce large temporal modulation depth for the phase modulation pulse and induce double amplitude modulation (AM) if the frequency shift is lower than half bandwidth of the signal spectrum. We should choose a wider bandwidth filter to minimize the impact of the filter on the output pulse and suppress the amplified spontaneous emission (ASE) for the power fiber amplifier. These results are of benefit to the design of the fiber front end system. (authors)

[en] The thermal effect has become the biggest limiting factor regarding the further power scaling of single mode fiber lasers, and it can lead to coating failure and transverse mode instability. A tapered cladding diameter profile design is proposed for the tandem-pumped fiber laser in this work, as it can smooth the temperature profile and reduce the maximum temperature rise within the fiber tremendously. The improvement in performance of the fiber design is verified by analytical and numerical results. (paper)

[en] In order to improve the signal-to-noise ratio of an all-fiber front-end system for high-energy pete-watt (PW) laser devices, we propose a method to restrain the noise by optical Kerr effect. In terms of analytical calculation, it is found that the signal-to-noise ratio can be increased by three orders of magnitude with the cell of pulse cleaning for the pulses, with the full width at half maximum TFWHM larger than 100 ps. However, numerical calculation indicates that the group-velocity dispersion (GVD) may have a marked effect on the pulses with TFWHM smaller than 100 ps but larger than 5 ps, with the help of self-phase modulation (SPM). This would debase the performance of the cell of pulse cleaning. Meanwhile, we study the methods of restraining the distortion for the pulses with different peak powers to improve the performance of an all-fiber front-end system for high-energy PW laser devices, These results are of benefit to the experiments and the improvement of signal-to-noise ratio for high-energy PW laser devices. (authors)