Flow Characteristics Of The Inorganic Liquid Laser System

Research on high-energy laser system is the international advanced domain which are of concern to the forefront of one of the areas in the civilian and military have broad application prospects. The Nd³⁺ inorganic liquid laser system with DL pumped has obvious advantages: not only effectively use of pump energy to achieve high output, but also can effectively solve the thermal distortion. Therefore, it is exploring a new type of high-energy laser system in the direction of the important research value.Laser diode-pumped neodymium-doped liquid inorganic laser systems can be used to achieve better cooling effect by using circulation. Liquid medium circulation to eliminate the thermal effects laser system provides an effective means to improve the system of laser beam quality is of great significance, in the course of the pipeline within the gain medium inevitable effect of the presence of turbulence, which have a greater impact on laser transmission and thermal distortion. The need for further discussion of these issues. To illustrate the characteristics of the system flow properties of laser systems, use theoretical analysis and numerical simulation model, combining the turbulence disturbance and distribution of temperature, and analyze the relationship between medium intensity and velocity and turbulent boundary layer thickness and transmission characteristics of the media spot drift, flashing spot and beam expansion, turbulence. The specific contents include:1. The development of inorganic liquid technology and related research results, a brief description of the optical properties of the inorganic liquid;2. According to flow and laser basic theory of the liquid medium cell gain region, basic theory and gain medium temperature distribution model are given. Derive steady down the temperature perturbation equation and the turbulence distribution of temperature in the pipeline;3. According to changes of flow field, analyze the relationship between pump area of medium intensity, velocity and turbulent boundary layer thickness, temperature perturbation and the impact of heat distortion. Using the OPD distribution and variance, a measure of its output characteristics was given;4. Analysis of transmission characteristics of the media spot drift, flashing spot, beam expansion and turbulence when the parallel beams through the cell, and the OPD of the laser beams through a turbulent medium. The scattering during light transmission was also concerned;5. Analyze the factors impacting the beam quality of the system and the SR beam quality assessment was given, which provides the way of choosing extracting region;6. Description of the neodymium-doped laser circulation system, inorganic liquid pipeline material selection process and the circulatory system of the basic structure of experimental device. Several experimental content is given, and under the conditions of the different configuration of the liquid laser fluorescence lifetime is measured.Combination of simulation using Fluent6.53 and analysis of basis thereoy, the conclusion of simulation about temperature distribution was agree with the theoretical analysis. Heat accumulation of surface phenomena was serious, which showes negative impact of laser output. Increasing velocity of laser medium in the channel would reduce thermally induced distortion and boundary layer thickness. Setting proper aperture under current conditions can also further reduce the distortion. Increasing turbulence coherence would be well for optical transmission, when the gain medium length is not too large, spot drift, flashing spot and beam expansion, such transmission performance little influence on the system. The appropriate pump power intensity, absorption, initial velocity and the average temperature of the selected gain medium is the key to choose the extraction region. Simulation results show that when pumping power intensity is 400 W/cm² and flow rate is 20-30 m/s, the wavefront distortion and extraction efficiency become better. When pumping power intensity increases, the greater velocity is needed to reduce heat gain the accumulation of the region.According to theoretical analysis and simulation results, using circulation system to carry out in-depth research. Through research of high average power, high beam quality, high-repetition-frequency output of the laser method, better system performance compared to passive optical experiments can be achieved. The instability of flow velocity in the cell, pipeline vibration and impurities in the liquid medium have effect on the system performance, which needs further study.