The multi-tone amplification for the purpose of mitigating stimulated Brillouin scattering (SBS) effect is investigated. Different wavelengths and power ratio are considered in the simulation model to achieve optimal results. The numerical simulation results indicate that SBS is effectively suppressed in a fiber amplifier with an output from 53.7W to 96.9W by utilizing this approach.
The output power of a narrow line-width laser is usually limited by the Stimulated Brillouin Scattering effect. In Master Oscillator Power Amplifier structures, multi-point pump could rearrange the gain distribution along the fiber, leading to the suppression of the Stimulated Brillouin Scattering effect with maintained amplification efficiency. A theoretical model concerning 100W-level fiber amplifiers is proposed. Stimulation is performed to analyze the amplification process of the laser signal and Stimulated Brillouin Scattering. The results demonstrate that the power of scattering light decreases from 3.2W to 6.8mW (with two-point pump) indicating the effectiveness of this new technology in Stimulated Brillouin Scattering suppression.
The far field beam profile is of significant importance to the analysis of the atmospheric propagation effect and evaluation of the beam control capability, tracking and aiming precision of laser system. In the paper, technology of laser beam measurement such as mid-infrared laser detection at wide temperature range, power density attenuation, photoelectric and calorimetric compound method for laser measurement, synchronous detecting of multi-channel pulsed signal are introduced. A series of instrumented target with detector array are developed for laser beam power density distribution measurement at far field. The power in the bucket, strehl ratio, centroid and jitter of beam can be calculated from the measured results.
The discoloration and optical characteristics of the gold plating film under long-time high power laser irradiation are investigated. The fabrication process of gold plating on nickel underplate on rough surface of copper and aluminum alloy substrates is introduced. The measurement results of the diffuse reflectivity for the samples with different surface roughness indicate that roughness of the gold layer surface should be 4μm to obtain the maximum value of diffuse reflectivity. The discoloration and variation of diffuse reflectivity are experimentally studied under 2000W irradiation. The research results show that the discoloration and degrading of reflectivity are caused by the diffusion of Ni to the gold plating surface and forming NiO thin film due to the porosity of the gold film and high temperature treatment. A change of diffuse reflectivity related mechanism is described. Several plating solution recipes are used to eliminate the discoloration and mitigate the degrading of the reflectivity on gold surface.