Polyimide films are widely used in spacecraft, but their mechanical properties would degrade in space environments, such as electron, proton, near ultraviolet or far ultraviolet, etc. The mechanical property and mechanism of polyimide film in electron, proton, near ultraviolet and far ultraviolet was studied by Φ800 combined space radiation test facility of Beijing Institute of Space Environment Engineering (BISSE. Rupture elongation of Kapton film decrease with the increase of the tensile deformation rate. The tensile strength and the rupture elongation of Kapton film decrease with the increase of electron and proton radiation, while tensile strength and the rupture elongation of Kapton film decrease firstly and then increase with near ultraviolet and far ultraviolet.
During its projected extended stay in LEO, spacecraft will encounter many environmental factors including energetic particles, ultraviolet radiation, atomic oxygen, and space debris and meteoroids, together with some induced environments such as contamination and discharging. These space environments and their effects have threat to the reliability and lifetime of spacecraft. So, it is important to give a combined design against the threat from space environments and their effects. The space environments and effects are reviewed in this paper firstly. Secondly, the design process and method against space environments are discussed. At last, some advices about protective structure and materials are proposed.
Glancing angle deposition (GLAD) is a novel way to produce nanostructural thin films with engineered porosity, and it is
possible to make new optical components in laser systems. In this paper, ZrO2, SiO2 and TiO2 thin films were grown by
electron beam evaporation with GLAD technique. Different microstructures were observed. The optical properties, such
as transmittance and refractive index were characterized. As application of the GLAD thin films, several optical
components were designed and fabricated, such as graded-index rugate filter, broadband antireflection coating and phase
retardater for visible and near infrared laser systems. Finally, laser-induced damage threshold were measured and
Reactive magnetron sputtering can be used to prepare graded index coatings. In this paper the relationship between the refractive index of the coatings and the partial pressure of reactive gas is discussed by experiment, in which A, O2 and Si are taken as sputtering gas, reactive gas and target material separately. And we have come to such conclusions that with the increase of partial pressure of reactive gas the color of the coatings turns shoal, the transmittance minimum of the coatings increases and the refractive index of coatings decreases according to the fitting rule of cubic polynomial. From XRD analysis, it can be seen that the coatings are identified to be amorphous.
Multi-layer dielectric grating is a key element used in chirped-pulse amplification technique. It includes high reflectivity film and periodic gratings on its top. Design of HR coating and top layer film (called multi-layer dielectric grating film) to produce gratings is important to fabricate such element with perfect optical properties and high laser induced damage threshold. In this paper, needle method is employed to synthesize the HR film with non-quarter wave coatings. The top layer is constructed by Fourier modal method, which is a rigorous method to analyze gratings. The synthesized multi-layer dielectric grating film shows good optical properties and electric intensity distribution.
By introducing scattering probability and statistical distribution functions of substrate subsurface defects' radius, refractive indices and positions, extended bidirectional reflectance distribution function (BRDF) was derived on the foundation of Jones scattering matrix. A numerical calculation of the extended BRDF for p-polarization incident light has been performed by employing Monte Carlo method. The calculating results indicate that the extended BRDF depends strongly on incident angle, scattering angle and azimuth angle, and presents a specific symmetry. For real refractive index, the extended BRDF is independent of subsurface defects' positions. And the extended BRDF will provide a more precise model for the calculation and measurement of polarized light scattering resulting from subsurface defects.
A model for refractive index of stratified dielectric substrate was put forward according to theories of inhomogeneous coatings. The substrate was divided into surface layer, subsurface layer and bulk layer along the normal direction of its surface. Both the surface layer (separated into N1 sublayers of uniform thickness) and subsurface layer (separated into N2 sublayers of uniform thickness), whose refractive indices have different statistical distributions, are equivalent to inhomogeneous coatings respectively. And theoretical deduction was carried out by employing characteristic matrix method of optical coatings. An example of mathematical calculation for optical properties of dielectric coatings had been presented. The computing results indicate that substrate subsurface defects bring about additional bulk scattering and change propagation characteristic in thin film and substrate. Therefore, reflectance, reflective phase shift and phase difference of an assembly of coatings and substrate deviate from ideal conditions. The model will provide some beneficial theory directions for improving optical properties of dielectric coatings via substrate surface modification.
The influence of inhomogeneous transitional layers on the spectral characteristics of AR coatings is discussed in this paper, and some results have been got: Inhomogeneous layers between substrate and coatings results in decreasing of the anti-reflection performance along with extremum shift to short wavelength; and among several kinds of inhomogeneous layers between two coatings, sine transition increases the anti-reflection performance, linearity, hyperbolae and exponent decrease the anti-reflection performance. Then a good fitting was given to the experiment of AR coatings and it was discovered that the sine transition between substrate and coatings is similar to experiment very well.