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SiO2 thin films is one of the most important low refractive index materials in the field of optical thin film. SiO2 thin films were deposited on Si substrates by different deposition technique. The optical stability of SiO2 thin films were investigated as a function of time placed in the air. Optical constants of SiO2 thin films were calculated using the ellipsometry spectra at different aging times. With the increase of the placed time, the physical thickness and optical thickness of EB-SiO2 thin films and IAD-SiO2 thin films increase, but IBS-SiO2 thin film decreases. The change of optical thickness of SiO2 thin films are separately 1.0%, 2.3% and -0.2%. When the placed time reaches 120 days, the physical thickness and optical thickness of IBS-SiO2 thin films, EB-SiO2 thin films, and IAD-SiO2 thin films tend to be stable. The results indicate that the optical stability of IBS-SiO2 thin film is better than other SiO2 thin films, and in the design of protective coating, SiO2 thin films should be deposited with ion beam sputtering technique.

Compound Gaussian oscillator model is one of the most commonly used physics model in the study of dielectric coefficient of amorphous glassy material in abnormal dispersion region. A new procedure was demonstrated for that the characteristic peaks of SiO2 films were equal to chemical component by combining the factorial analysis technology of chemical meterage. Infrared absorption spectrum in the range of wavenumber 400~4000cm−1 was studied. Through matrix analysis of infrared spectrum of ion sputtering prepared SiO2 films of different thickness (800~100nm), the number of Gaussian oscillators was calculated to be 9, which provide definite physics meaning for the reverse data process of dielectric constant. A comparison of dielectric constant between SiO2 thin film and fused quartz in the range of wavenumber 3000~4000cm-1 was made. Results indicated that there is obvious hydration defects in SiO2 films, which would affect the dielectric constant in the entire infrared range.

SiO2 thin film is one of the most important low refractive index materials in the area of optical thin films. It is always used in the design and preparation of many kinds of multilayer films. The dielectric constant of the SiO2 thin film is a key characteristic for design of the multilayer thin film. The composite Gaussian oscillator model is one of the most important dispersion models for the dielectric constant of the amorphous SiO2 in the anomalous dispersion regime in the infrared range. More and more researchers have focused on the number and the physical meaning of the oscillators in the composite oscillator. A method to determine the SiO2 thin film oscillator quantity was proposed. In this method, the quantity of oscillator peaks was equivalent to the oscillator number of chemical composition, based on the factor analysis technology of chemometrics. Concretely, the composite oscillators of the dielectric constant were equivalent to the mixture, and the independent oscillators were equivalent to the compositions of the mixture. The absorbance of the mixture changed with the physical thickness of the thin film. Eight SiO2 film samples with different thickness were prepared on the Si substrate by the ion beam sputtering deposition. The infrared transmittances of the eight samples were used as elements in the spectral matrix. There were nine Gaussian oscillators in the range of 400-4000 cm-1, which was determined by the factor analysis technology. The dielectric constant of the SiO2 thin film in this range was obtained by the inverse calculation from the spectral transmittance. It provides the inverse calculation result for the dielectric constant of the SiO2 thin film with a specific physical meaning. By analyzing the dielectric constant in the range of 400-900 cm-1, the symmetric stretching vibrational frequency and the in-plane rocking frequency of the Si-O-Si bond of the SiO2 thin film can be obtained. Compared with fused silica, the symmetric stretching vibrational frequency increased while the rocking frequency was reduced. In fact, the frequency shifts are caused by the strain of the thin film. By analyzing the dielectric constant in the range of 900-1500 cm-1, four anti-symmetric stretching vibrational frequencies of the Si-O-Si bond in the SiO2 thin film were obtained. They have a certain corresponding relation with the anti-symmetric stretching vibrational frequency of the Si-O-Si bond in the fused silica. What's more, by analyzing the dielectric constant in the range of 3000-4000 cm-1, the water-cut (or hydroxyl) chemical defects in the films were confirmed. The chemical defects can influence the dielectric constant in the whole infrared range.

SiO2薄膜是光学薄膜领域内常用的重要低折射率材料之一。在文中研究中，通过测量薄膜的椭偏参数，使用非线性最小二乘法反演计算获得薄膜的光学常数。采用离子束溅射和电子束蒸发两种方法制备了SiO2薄膜，在拟合过程中，基于L8（22）正交表设计了8组反演计算实验，以评价函数MSE为考核指标。实验结果表明：对IBS SiO2薄膜拟合MSE函数影响最大的为界面层模型，对EB SiO2薄膜拟合MSE函数影响最大的为Pore模型。同时确定了不同物理模型对拟合MSE函数的影响大小和反演计算过程模型选择的次序，按照确定的模型选择次序拟合，两种薄膜反演计算的MSE函数相对初始MSE可下降35%和38%，表明拟合过程模型选择合理物理意义明确。文中提供了一种判断薄膜物理模型中各因素对于薄膜光学常数分析作用大小的途径，对于薄膜光学常数分析具有指导意义。

Periodic structure is the basic physical model in optical film design. Universal conditions of the reflecting center wavelength are given. With the refractive index dispersion of the layers, the reflecting center wavelength and the band characteristic of equal-thickness and unequal-thickness periodic structures are studied. According to experimental results, in both the equal-thickness and unequal-thickness periodic structures with the refractive index dispersion of the coating layers, the reflecting center wavelength moves towards the longer wavelengths, and the reflective series as well as the relative wave number will depart from linear relation. For the same optical thickness of the film with unequal-thickness periodic structure, when the optical thickness of the high refractive index layer is bigger than that of the low refractive index layer, the departure from linear relation between the reflective series and the relative wave number is higher. For the low reflective series, the bandwidth of unequal-thickness periodic structure is smaller than that of equal-thickness periodic structure. The influence of the layer dispersion on the bandwidth is found to be weak.

SiO2 is one of important low refractive index materials, and SiO2 films are prepared by both ion-beam sputtering (IBS) and electron-beam evaporating (EB) technology. Dielectric constants of SiO2 films are calculated by infrared spectrum inversion technique in a wavenumber range from 400 cm-1 to 1500 cm-1. Through analyzing dielectric energy loss function, the oscillation frequency and the Si–O–Si angle of two types of SiO2 films are obtained in the transverse optics and longitudinal optics oscillating mode. The research results indicate that the attended modes of SiO4 are main coesite-like structure, three-plane folding ring structure, and keatite-like structure in the range of short-range order for EB-SiO2 films, but the attended modes of SiO4 are main coesite-like structure, three-plane folding ring structure, four-plane folding ring structure, and keatite-like structure in the range of short-range order for IBS-SiO2 films.