Yingjian Wang

The effects of ion cleaning on the roughness of substrates and laser-induced damage thresholds of films

The ion cleaning effect on the roughness of substrates and laser induced damage thresholds (LIDT) of films were investigated. It is found that ion cleaning has different effects on the roughness of substrates with the different ion cleaning time, and it improves the LIDT of single layer films greatly.

Elimination of the half-wave hole for short-wave pass filter

A few reasons to cause the half-wave hole for the short-wave pass filter had been analyzed. According to these reasons, the application of a new admittance-matching method and a photoelectric maximum control with half-wavelength effectively eliminated the half-wave hole. The matching stack consisted of a symmetrically periodic structure and provided a complete matching at the desired wavelength; i.e., both conditions for the equivalent admittance and phase thickness were fulfilled. Furthermore, both the theoretical and the tested curves had been given, and a good agreement between them was obtained.

Laser-induced damage threshold of the antireflection coatings on quartz and sapphire under different laser modes

The laser-induced damage threshold (LIDT) and damage morphology of antireflection (AR) coatings on quartz and sapphire are investigated. A very interesting phenomena is found in the measurement. In the case of a single pulse laser, the LIDT of the AIR coatings on quartz is higher than that of sapphire. On the contrary, for a free-pulse laser, the LIDT of AIR coatings on sapphire is higher than that of quartz

Preparation and performance of phase retarder at the wavelength of 1315 nm

The periodic dielectric phase retarders that produce a ±90° phase shift between the p- and s- polarization components at the incident angle of 54° and the wavelength of 1315nm while maintaining high reflectivity for both components are designed. An optimization technique has been used to determine the layer thickness for a coating design that produce a 270±1° phase shift between the p- and s- polarization components over 1285-1345nm while the average reflectivity is over 99.5%. Then the designed retarders were prepared by ion beam sputtering (IBS), and the phase shift was 262.4±1.8° and the reflectivity was over 99.6% at the design waveband.

Influence of inhomogeneities on the spectral characteristics of anti-reflection coatings

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.

LIDT of the AR coatings on quartz and sapphire under different laser modes

The LIDT and damage morphology of the AR coatings on quartz and sapphire are investigated. A very interesting phenomena is found in the measurement: In the case of single pulse laser, the LIDT of the AR coatings on quartz is higher than that of sapphire; on the contrary, for free pulse laser, the LIDT of the AR coatings on sapphire is higher than that of quartz.

Characteristics of high-reflection thin films in a COIL system

Several kinds of high reflection thin films are prepared by electron beam gun with different designs and coating materials. The reflectivity, transmission, absorption and scattering of these thin films are measured and calculated, the loss of absorption and scattering of the thin films are mainly discussed. Furthermore, the absorption of films are also analyzed under different annealing temperature, it is found that the absorption loss can be dramatically reduced after annealing. At the same time, the compositions of thin films are tested by AES (Auger electron spectroscopy) to detect whether there is impurity or contamination.