Research Articles|153 Article(s)
Propagation characteristics of a high-power broadband laser beam passing through a nonlinear optical medium with defects
Xueqiong Chen, Xiaoyan Li, Ziyang Chen, Jixiong Pu, Guowen Zhang, and Jianqiang Zhu
The intensity distributions of a high-power broadband laser beam passing through a nonlinear optical medium with defects and then propagating in free space are investigated based on the general nonlinear Schr dinger equation and the split-step Fourier numerical method. The influences of the bandwidth of the laser beam, the thickness of the medium, and the defects on the light intensity distribution are revealed. We find that the nonlinear optical effect can be suppressed and that the uniformity of the beam can be improved for a high-power broadband laser beam with appropriate wide bandwidth. It is also found that, under the same incident light intensity, a thicker medium will lead to a stronger self-focusing intensity, and that the influence of defects in the optical elements on the intensity is stronger for a narrowband beam than for a broadband beam.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.1 Issue, 3-4 3-4000132 (2013)
Energy measurement system of a large-aperture high power laser experiment platform
Yanwen Xia, Yue Liang, Sen Li, Junpu Zhao, Zhitao Peng, Hongguang Li, Hua Liu, Zhihong Sun, Kuixing Zheng, and Xiaofeng Wei
An energy measurement system in a Large-aperture high power laser experiment platform is introduced. The entire measurement system includes five calorimeters, which carry out the energy measurement of the fundamental frequency before the frequency conversion unit, remaining fundamental frequency, remain second-harmonics, third harmonics, as well as the energy balance measurement after the frequency conversion unit. Combinational indirect calibration and direct calibration are employed to calibrate the sampling coefficients of the calorimeters. The analysis of the data showed that, regarding the energy balance coefficients, combinational calibration approach gives a higher precision, and leads to an energy balance with 1%; and regarding the energy sampling coefficients for the various wavelengths after the frequency conversion, the results from direct and combinational calibration are consistent. The uncertainties for all energy sampling coefficients are within 3%, which guarantees the reliability of the energy measurement for the laser facility.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.1 Issue, 3-4 3-4000126 (2013)
Rapid growth of a large-scale (600 mm aperture) KDP crystal and its optical quality
Guohui Li, Guozong Zheng, Yingkun Qi, Peixiu Yin, En Tang, Fei Li, Jing Xu, Taiming Lei, Xiuqin Lin, Min Zhang, Junye Lu, Jinbo Ma, Youping He, and Yuangen Yao
Potassium dihydrogen phosphate (KDP) single crystals are the only nonlinear crystals currently used for electro-optic switches and frequency converters in inertial confinement fusion research, due to their large dimension and exclusive physical properties. Based on the traditional solution-growth process, large bulk KDP crystals, usually with sizes up to 600 $\times $ 600 mm$^{{2}}$ so as to make a frequency doubler for the facility requirement loading highly flux of power laser, can be grown in standard Holden-type crystallizers, without spontaneous nucleation and visible defects, one to two orders of magnitude faster than by conventional methods. Pure water and KDP raw material with a few ion impurities such as Fe, Cr, and Al (less than 0.1 ppm) were used. The rapid-growth method includes extreme conditions such as temperature range from 60 to 35$^{\circ }$C, overcooling up to 5$^{\circ }$C, growth rates exceeding 10 mm/day, and crystal size up to 600 mm. The optical parameters of KDP crystals were determined. The optical properties of crystals determined indicate that they are of favorable quality for application in the facility.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.2 Issue, 1 010000e2 (2014)
Ultrafast dynamical process of Ge irradiated by the femtosecond laser pulses
Fangjian Zhang, Shuchang Li, Anmin Chen, Yuanfei Jiang, Suyu Li, and Mingxing Jin
The ultrafast dynamic process in semiconductor Ge irradiated by the femtosecond laser pulses is numerically simulated on the basis of van Driel system. It is found that with the increase of depth, the carrier density and lattice temperature decrease, while the carrier temperature first increases and then drops. The laser fluence has a great influence on the ultrafast dynamical process in Ge. As the laser fluence remains a constant value, though the overall evolution of the carrier density and lattice temperature is almost independent of pulse duration and laser intensity, increasing the laser intensity will be more effective than increasing the pulse duration in the generation of carriers. Irradiating the Ge sample by the femtosecond double pulses, the ultrafast dynamical process of semiconductor can be affected by the temporal interval between the double pulses.
High Power Laser Science and Engineering
  • Publication Date: Apr. 05, 2016
  • Vol.4 Issue, 2 02000e12 (2016)
Nitrogen fluorescence induced by the femtosecond intense laser pulses in air
He Li, Suyu Li, Shuchang Li, Dunli Liu, Dan Tian, Anmin Chen, Ying Wang, Xiaowei Wang, Yunfeng Zhang, and Mingxing Jin
Our experiments show that external focusing and initial laser energy strongly influences filament generated by the femtosecond Ti–sapphire laser in air. The experimental measurements show the filament length can be extended both by increasing the laser energy and focal length of focusing lens. On the other hand, the plasma fluorescence emission can be enhanced by increasing the laser energy with fixed focal length or decreasing the focal length. In addition, the collapse distance measured experimentally are larger than the calculated ones owing to the group-velocity-dispersion effect. In addition, we find that the line widths of the spectral lines from $\text{N}_{2}$ is independent of filament positions, laser energies and external focusing.
High Power Laser Science and Engineering
  • Publication Date: Mar. 09, 2016
  • Vol.4 Issue, 1 010000e7 (2016)