Thin solid film systems of antireflection coating and for active mirror amplifier, polarizing beam splitter and disk amplifier used in the high power laser system ($\lambda_0 = 1060$ nm) are designed by computer aided optimization technique. In order to satisfy the specified characteristics of the thin film systems, the typical thin film systems reported previously are extensively analyzed. Maximum reflectance of designed thin film system of active mirror amplifier is less than 5% for pumping band (500-900 nm) and 99.74% for laser beam. Extinction ratio of designed polarizing beam splitter for incidence angle 30˚,45˚,56.66˚ are 1:93, 1:895, 1:1991, respectively. Maximum reflectance of designed thin film system of disk amplifier is less than 3% for pumping band (500-900 nm) and 0.15% for laser beam.
Further, $SiO_2$ film chosen as one of the suitable thin films in the high power laser system is prepared by the sol-gel process which gives high damage threshold coating. Among the various parameters in the control of film thickness, withdrawal speed of substrate and concentration of the solution are determined. When the withdrawal speed is 6.15 cm/min - 16.62 cm/min and the mixing ratio is in the range of 1 mol (ethylsilicate) : 4-8 mol (ethylalcohol) : 2 mol (water), the thickness of deposited film is in the range of 500Å-1500Å.
