Optical constants of vacuum-deposited hafnium oxide film (HfO2) from infrared to ultraviolet spectral region
(215nm-1700nm) have been determined by variable angle Spectroscopic ellipsometry with Cauchy dispersion model,
Sellmeier dispersion model, Cauchy-Urbach dispersion model and Tauc-Lorentz dispersion model, respectively. The
optical constants of the HfO2 film which were extracted with the four dispersion models have been compared. The
surface roughness layer between HfO2 film and air and the interface layer between the film and the substrate have also
been modeled with Bruggeman effective medium approximation (BEMA).
Optical constants of vacuum-deposited Zinc selenide (ZnSe) film from far infrared to near ultraviolet spectral region
(270nm-30μm) have been determined by variable angle spectroscopic ellipsometry. The surface roughness layer and
interface layer between ZnSe film and crystalline silicon have been modeled with Bruggeman effective medium
approximation (BEMA). To evaluate the microstructure of ZnSe film, X-ray diffraction (XRD) measurements are also
The Laser-induced damage behavior of single-Crystalline Silicon was investigated with a Nd:YAG laser at 1064nm under single-pulse mode and free-running mode. It was found that the damage behavior of the SCS showed strong dependence on the output mode of the incident laser. From the experimental and theoretical analysis, the damage mechanism under the two laser modes were given based on thermal and thermal-stress coupling models.
Zirconium oxide films were prepared with and without ion beam assisted deposition (IBAD) by an electron beam. The effects of Ar-ion bombardment on the optical inhomogeneity of ZrO<sub>2</sub> films deposited at room temperature were investigated. The results show that all samples are amorphous, and the refractive index of sample A without IBAD randomly changed with the film thickness, while the relative inhomogeneity of samples B, C, D with IBAD nearly zero. It was found that the energy of depositing molecule or atom had an important effect on the optical inhomogeneity of films, and the optical inhomogeneity of amorphous ZrO2 films could be improved by IBAD.
Laser conditioning effects of the dielectric oxide mirror coatings with different designs were investigated. Simple quarter-wave ZrO<sub>2</sub>:Y<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> mirrors and half-wave SiO<sub>2</sub> over-coated ZrO<sub>2</sub>:Y<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> mirror coatings at 1064nm were fabricated by E-beam evaporation (EBE). The absorbance of the samples before and after laser conditioning was measured by surface thermal lensing (STL) technology and the defects density was detected under Nomarski microscope. The enhancement of the laser damage resistance was found after laser conditioning. The dependence of the laser conditioning on the coating design was also observed and the over-coated sample obtained greatest enhancement, whereas the absorbance of the samples did not change obviously.
The Laser-induced damage behavior of narrow-band interference filters was investigated with a Nd:YAG laser at 1064nm under single-pulse mode and free-running mode. The absorption measurement of such coatings had been performed by Surface Thermal Lensing (STL) technique. And the relationship between damage morphology and absorption under the two different laser modes had also been studied in detail. The explanation is given by the standing-wave distribution theory.
Investigation of laser-induced damage (LID) of dielectric optical coatings was reviewed in this paper. Several methods for evaluating characters of LID were developed, especially for the determinations of laser-induced damage threshold (LIDT) and the detections of absorption based on surface thermal lensing (STL) technology of optical coatings. Defect was deemed to be the initial source of several previous damage mechanisms, and was the main factor restricting the laser damage resistance of optical coatings. A pulsed laser induced damage model with a spherical absorptive inclusion was proposed in order to obtain the nature, size and distribution of defects. Attentions were paid to find out the origins of damage mechanism transformation from one laser mode to another. Moreover, interests were focused on distinct damage behaviors of ultraviolet (UV) lasers. Deposition temperature and annealing process in vacuum chamber had obvious influences on LIDT of the third harmonic Nd:YAG laser coatings. At the end of this paper, several effective methods for improving LIDT were put forward, such as cleaning substrate, improving deposition process, adding protective layers, optimizing coating stacks based on temperature field theory, as well as laser conditioning.
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.