The characterization of optical thin film includes the characterization of optical properties, optical parameters and non-optical properties, the optical properties mainly refer to the spectral reflectance, transmittance and optical loss (absorption loss and reflection loss) properties of optical thin film. Transmittance and reflectance are the most basic optical properties of optical thin films, so the testing of thin film transmittance and reflectance is the basic testing technique for optical thin films. Optical parameters of optical thin film include refractive index, absorption coefficient and film thickness of optical thin film. Due to the stoichiometric deviation in the material components of the optical thin film prepared by the actual process, the structure is no longer homogeneous and dense, but there are microstructures and various defects, the dielectric film layer is no longer completely transparent, and there is a weak absorption, while there are spatial non-uniformity and phase anisotropy in the refractive index of the film, and the film is no longer an infinite and smooth interface. More importantly, in the actual preparation process, the film preparation process parameters have a very large impact on the optical parameters of the film, so the real-time confirmation of the optical parameters of the film is very critical. In addition, the optical thin film as a device used in the actual environment, in addition to the optical characteristics of the device needs to meet the requirements, the film there are many other important non-optical characteristics affect the use of the film, such as film adhesion, film stress, film hardness and surface roughness and the film’s ability to withstand the environment and so on. Therefore, it is important to accurately measure all the various parameters or characteristics that affect the use of thin film devices.
Transmittance and reflectance of thin films are mainly tested using spectral test analyzers. Spectral analyzers for optical film testing can be divided into UV-Vis spectrophotometers, infrared spectrophotometers and infrared Fourier spectrometers according to the different test bands. The first two use spectral spectroscopy principle of analysis and testing system, the latter based on the principle of interference spectral analysis system. Due to the different geometric structures and shapes of thin-film devices, although all transmittance and reflectance measurements, but for different shapes, different precision or different polarization requirements, may require different test methods and techniques.
–This article is released by vacuum coating machine manufacturer Guangdong Zhenhua
Post time: Nov-03-2023