Design And Research Of The Multilayer Water-cooled Silicon Mirror

In order to obtain close-to-diffraction-limited output at the far-field in high-energy laser, the thermal deformation of the resonator mirror must be decreased. The aim of this thesis is to design a multi-layer water-cooled silicon mirror with low thermal deformation during laser operation. The analysis of thermal deformation, the structure design and the finite element numerical simulation for the multi-layer water-cooled silicon mirror as well as the indoor tests and on-site tests have been investigated in this thesis. . The theoretical analysis of resonator mirror thermal distortion is based on the resonator mirror heat transfer model, and considered synthetically the influence of pressure deformation and thermal deformation. The result shows that the mirror should be as thin as possible under the condition of keeping the mirror rigidity if small total deformation is demanded. Thus, this thesis is focused on the investigation of an ultra-thin multi-layer water-cooled silicon mirror. Concerning about the structure design and the finite element numerical simulation of the mirror, the different types of water-cooled mirror distortion and influence factors were introduced, and the structure characteristics of the various pressure manifold water-cooled mirror were illuminated in detail. For the actual demand, the two kinds of water-cooled silicon mirrors with respectively spiral and linear microgroove structures were designed based on the previous researches. In addition, the numerical simulation of the two water-cooled mirrors was computed by using ANSYS software. The simulation results show that the dynamic thermal characteristic of the water-cooled mirror with linear runner structure is much better than that of the water-cooled mirror with spiral runner structure. The water-cooled mirror with linear runner structure can reach steady state in 1.5s, but the water-cooled mirror with spiral runner reaches steady state after 3s, although it has small deformation and uniform deformation. In order to further verify the thermal deformation characteristic of the mirror, the experiments such as the water pressure, the thermal deformation and the deformation recovery have been performed. The experimental results testify that the water-cooled silicon mirror with linear type microgroove runner can make the stability of laser output better and meet the need of stability in practical application although its absolute distortion is tinily larger compared with the water-cooled mirror with spiral type runner. Moreover, the mirror have been applied in the 2kW continuous wave CO2 laser and the high-energy pulse COIL laser for the stability test, and the test results prove that 2kW continuous wave CO2 laser can steadily reach the average output power of 890W with the low-order modes dominated by TEM01 mode and the two-hour stability of ±3.4%, and the βvalue of high-energy pulse COIL laser will be steady in 2s.