With the laser power and operation time increasing, the surface distortion of the laser cavity mirrors has been a critical problem to be resolved. In order to maintain the mirror shape under intense laser irradiation, in this paper, a new type of micro channel silicon water cooled mirror is given. The water cooled mirror includes three layers, the first layer is mirror seat made of Invar materials with water inlet and outlet, the second layer is water manifold unit made of silicon with millimeter channels; the third layer is reflection plate with micro-channels. These three layers are bonded together by vacuum soldering. Then the thickness of the reflection plate is reduced to 0.5mm by grinding, and polished by traditional pitch polishing method. In order to reduce the coating stress, conventional all dielectric coating is replaced by a metal dielectric film stack. At last, a 100mm×100mm water cooled mirror is fabricated with surface figure 0.22λ@632.8 nm. The mirror surface distortion is 0.12λ、0.24λ、0.33 λ respectively corresponding to 7.3w/cm2 、11.9 w/cm2 、17.6 w/cm2 heat load.
Based on the principle of fluid mechanics, this paper presents the technological process of Fluid Jet Polishing. According
to the Preston hypothesis, the Fluid Jet Polishing removal amount could be described as a linearity function. The material
is removed by the collision and shear action between slurry and work-piece. Comparing to other optical method, kind of
abrasive slurry, average diameter of abrasive particle, pressure of abrasive particle, working time, incidence distance and
angle of incidence influence the surface figure result and quality of fluid jet polishing. The paper mainly focuses on the
influence of abrasive slurry and incidence distance.
In the experiment, we take the diameter of Φ120mm, thickness of 20mm, fused silica for example to examine the
exactitude principle of the fluid jet polishing. After the final process of fluid jet polishing, the surface figure PV(Peak
and Valley) is about 0.046λ(λ=633nm), the RMS (Root-Mean-Square)is about 0.007λ. The result of experiment testifies
fluid jet polishing could get high precision.