Comparison of TiO2 and ZrO2 Films Deposited by Electron-Beam Evaporation and by Sol-Gel Process

TiO2 and ZrO2 films are deposited by electron-beam （EB） evaporation and by sol-gel process. The film properties are characterized by visible and Fourier-transform infrared spectrometry, x-ray diffraction analysis, surface roughness measure, absorption and laser-induced damage threshold （LIDT） test. It is found that the sol-gel films have lower refractive index, packing density and roughness than EB deposited films due to their amorphous structure and high OH group concentration in the film. The high LIDT of sol-gel films is mainly due to their amorphous and porous structure, and low absorption. LIDT of EB deposited film is considerably affected by defects in the film, and LIDT of sol-gel deposited film is mainly effected by residual organic impurities and solvent trapped in the film.

Influence of deposition rate on the properties of ZrO_2 thin films prepared in electron beam evaporation method

ZrO2 thin films were prepared in electron beam thermal evaporation method. And the deposition rate changed from 1.3 to 6.3 nm/s in our study. X-ray diffractometer and spectrophotometer were employed to characterize the films. X-ray diffraction (XRD) spectra pattern shows that films structure changed from amorphous to polycrystalline with deposition rate increasing. The results indicate that internal stresses of the films are compressive in most case. Thin films deposited in our study are inhomogeneous, and the inhomogeneity is enhanced with the deposition rate increasing.

Study on absorbance and laser damage threshold of HfO_2 films prepared by ion-assisted reaction deposition

Using a new kind of EH1000 ion source, hafnium dioxide (HfO2) films are deposited with different deposition techniques and different conditions. The absorbance and the laser damage threshold of these films have been measured and studied. By comparing these characteristics, one can conclude that under right conditions, such as high partial pressure of oxygen and right kind of ion source, the ion-assisted reaction deposition can prepare HfO2 films with higher laser induced damage threshold.

Laser-induced damage threshold in n-on-1 regime of Ta_2O_5 films at 532,800,and 1064 nm

Ta205 films were prepared with conventional electron beam evaporation and annealed in 02 at 673 K for 12 h. Laser-induced damage thresholds （LIDTs） of the films were performed at 532 and 1064 nm in 1-on-1 regime firstly, and then were performed at 532, 800, and 1064 nm in n-on-1 regime, respectively. The results showed that the LIDTs in n-on-1 regime were higher than that in 1-on-1 regime at 532 and 1064 nm. In addition, in n-on-1 regime, the LIDT increased with the increase of wavelength. Furthermore, both the optical property and LIDT of Ta205 films were influenced by annealing in 02.

Influence of coating material on laser damage threshold of TiO_2 films

The optical property, structure, surface properties （roughness and defect density） and laser-induced damage threshold （LIDT） of TiO2 films deposited by electronic beam （EB） evaporation of TiO2 （rutile）, TiO2 （anatase） and TiO2 ＋ Ta205 composite materials are comparatively studied. All films show the polycrystalline anatase TiO2 structure. The loose sintering state and phase transformation during evaporating TiO2 anatase slice lead to the high surface defect density, roughness and extinction coefficient, and low LIDT of films. The TiO2 ＋ Ta205 composite films have the lowest extinction coefficient and the highest LIDT among all samples investigated. Guidance of selecting materials for high LIDT laser mirrors is given.

Laser-induced damage of high reflectors for Ti:sapphire laser system

A broadband （- 176 nm, R 〉 98%, λo = 800 nm） and high laser-induced damage threshold （LIDT = 2.4 J/cm^2） TiO2/HfO2/SiO2 high reflector （HR） for Ti：sapphire chirped-pulse amplification （CPA） laser system is fabricated by the electron beam evaporation. The refractive index and extinction coefficient of TiO2 and HfO2 films are calculated from single-layer films＇ transmittance spectra. The properties of HR are mainly determined by the high refractive index material. The high refractive index leads to wide bandwidth. A low extinction coefficient indicates low absorption and high LIDT. The possible damage mechanism of HR is discussed.

Investigation on the properties of high reflective mirror prepared by ion-beam sputtering

The single-sided and dual-sided high reflective mirrors were deposited with ion-beam sputtering （IBS）. When the incident light entered with 45°, the reflectance of p-polarized light at 1064 nm exceeded 99.5%. Spectrum was gained by spectrometer and weak absorption of coatings was measured by surface thermal lensing （STL） technique. Laser-induced damage threshold （LIDT） was determined and the damage morphology was observed with Lecia-DMRXE microscope simultaneously. The profile of coatings was measured with Mark III-GPI digital interferometer. It was found that the reflectivity of mirror exceeded 99.9% and its absorption was as low as 14 ppm. The reflective bandwidth of the dual-sided sample was about 43 nm wider than that of single-sided sample, and its LIDT was as high as 28 J/cm^2, which was 5 J/cm^2 higher than that of single-sided sample. Moreover, the profile of dual-sided sample was better than that of substrate without coatings.