With the progress of high power laser system, the specifications of the large-aperture optics on the
low-spatial-frequency wavefront, mid-spatial-frequency wavefront, high-spatial-frequency wavefront
all meet stricter requirements. To the mid-spatial-frequency wavefront, it has been researched less than
others. The influence factors of the mid-spatial-frequency wavefront PSD1 error for large-aperture
mirrors are analyzed in this work. The results show that the influence factors of the
mid-spatial-frequency wavefront is different with the low-spatial-frequency wavefront. PV error
depends on the peak and vale of film surface，Grms error is affected by the big amplitude wave of film
surface, and PSD1 error is mainly caused by the small frequency wave of film surface. So it is the key
to controlling the PSD1 error for large-aperture mirrors that reducing small frequency wave of film
Damage tests were carried out to measure the laser resistance of Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub>/HfO<sub>2</sub>
antireflection coatings at 1064nm grown by atomic layer deposition (ALD). The S-on-1 and
R-on-1 damage results are given. It's interesting to find that ALD coatings damage performance
seems closed to those grown by conventional e-beam evaporation process. For Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub>
coatings, the grown temperature will impact the damage resistance of thin films. Crystallization of
TiO<sub>2</sub> layer at higher temperature could play an importance role as absorption defects that reduced
the LIDT of coatings. In addition, it is found that using inorganic compound instead of organic
compound as precursors for ALD process can effective prevent residual carbon in films and will
increase the LIDT of coatings.
Generally, substrates in a planetary rotation system result in coatings with nonuniformity of 2% or greater over apertures of 500mm. However, more accurate, uniform deposition of large-aperture optical coatings is required now. So it is very important to study how to improve the deposition uniformity of large-aperture optical coatings. In this paper, we show that a theoretical model that can forecast the thickness distributions of films, get precise figure of masks, and should optimize the deposition uniformity accurately and fast through fixing the designed masks in the chamber.
The effects of coating parameters on the stress of silica coating, Hafnia coating have been studied. The aforementioned parameters are the angle of coating tooling, partial oxygen pressure during deposition. The experimental study shows that the parameters are two important parameters. To reduce the compress stress of silica, silica should be deposited at small angle of coating tooling and high partial oxygen pressure. The angle of coating tooling must be small and partial oxygen pressure must be higher still for the Hafnia coatings. According to the stress character of silica coating and Hafnia coating, the stresses are matched in a high reflection mirror. In this deposition technology, the high reflection mirrors also have high laser induce threshold. Which are satisfied the imposed requirement by power laser specifications.