| LI Yang,XU Jun-qi,SU Jun-hong,YUAN Song-song,LIU Qi,LIU Zheng.Residual Stress and Deformation of 1 064 nm High Reflection Films for Laser Systems[J],51(9):311-318, 334 |
| Residual Stress and Deformation of 1 064 nm High Reflection Films for Laser Systems |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.09.032 |
| KeyWord:multilayer films residual stress equivalent reference temperature birth-death element stress compensation layer surface shape |
| Author | Institution |
| LI Yang |
Shaanxi Province Thin Film Technology and Optical Test Open Key Laboratory, Xi'an Technological University, Xi'an , China |
| XU Jun-qi |
Shaanxi Province Thin Film Technology and Optical Test Open Key Laboratory, Xi'an Technological University, Xi'an , China |
| SU Jun-hong |
Shaanxi Province Thin Film Technology and Optical Test Open Key Laboratory, Xi'an Technological University, Xi'an , China |
| YUAN Song-song |
Shaanxi Province Thin Film Technology and Optical Test Open Key Laboratory, Xi'an Technological University, Xi'an , China |
| LIU Qi |
Shaanxi Province Thin Film Technology and Optical Test Open Key Laboratory, Xi'an Technological University, Xi'an , China |
| LIU Zheng |
Advanced Optical Manufacturing Technology Joint Laboratory, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an , China |
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| Abstract: |
| The large surface shape change on the substrate after coating is due to the residual stress of the optical films. It presents a challenge for coating optical elements with high precision surface shape. The work aims to study the residual stress mechanism and surface profile shape change of monolayer films and laser high reflection films with different films on substrate. The surface shape change of the substrate is reduced by adding a compressive stress compensation layer on the outermost layer of the multilayer films. It provides a method for preparing micro-deformation laser high reflection mirrors. The residual stress mechanism of monolayer film is analyzed by the theory of thermal stress and residual stress in optical films. The equivalent reference temperature is used to replace the intrinsic stress of optical thin films, and the intrinsic stress of optical thin films is obtained by simulation. The residual stress distribution and surface shape change of laser high reflection films-substrate system is studied by finite element analysis and experiments. Based on the stress of monolayer film, the residual stress distribution and surface profile change of high reflection films-substrate system is simulated and analyzed by equivalent reference temperature, birth and death element and load step technology. Different high reflection films are prepared by thermal evaporation of electron beam. The effects of initial substrate surface profile, films material and films combinations on high reflection films-substrate system are analyzed via testing surface profile changes of it, using Zygo laser interferometer. The simulation results show that the residual stress of high reflection films-substrate system is layered. It changes from tensile stress to compressive stress and then to tensile stress in the direction from the substrate to films. The surface profile of high reflective films-substrate system is concave and the Z-axis displacement is distributed annularly due to residual stress. By analyzing the influence of monolayer film on the substrate surface shape and comparing the residual stress value of each film layer in different high reflective films systems, it is found that the surface profile change of G│(HL)10H2L│A is smaller than G│(HL)10H│A with TiO2/SiO2. The surface profile of substrate with high reflective films (fused silica substrate, ϕ30×2 mm) is basically unchanged (ΔPV=0.004λ) because the residual stress of films reduced by adding a compressive stress compensation layer, which is consistent with the simulation results. On the fused silica substrate, the intrinsic stress of TiO2, HfO2, H4 and SiO2 plays a leading role in the residual stress. The residual stress of TiO2, HfO2, H4 is tensile on the fused silica substrate while the SiO2 is compressive. All the high reflection films systems with different material combinations show compressive. For TiO2/SiO2, the films-substrate system G│(HL)10H2L│A is smaller than G│(HL)10H│A in residual stress of optical films and the change of surface shape on substrate. Its residual stress value is –39.70 MPa, which is 22.26 MPa less than that without stress compensation layer. Its surface shape has basically not changed. The addition of 2L (stress compensation layer) balances the residual stress of the multilayer films-substrate system without affecting the spectral characteristics. |
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