RESUMEN
Thin-film polarizing beam splitters (PBSs) fulfill a pivotal role in laser beam splitting, modulation, shaping and isolation. In this study, a high-reliability infrared broadband thin-film PBS was developed. To correct for tensile stress in Ge/YbF3 multilayer coatings, ZnSe compensation layers were incorporated in the multilayer design. The effects of different symmetrical periods on the spectral properties of the infrared PBS were systematically discussed. The infrared PBS operated at 45° and in the long-wave infrared (LWIR) band. Using the percent of optical extrema monitoring (POEM) strategy combined with the high-temperature optical constants (HTOC) of Ge film, the infrared PBS was precisely fabricated on ZnSe substrates. Subsequently, the spectral performance and film reliability of the infrared PBS were carefully characterized. Specifically, the transmittance of p-polarization surpassed 96%, while the extinction ratio exceeded 100:1 within the 10.6 ± 0.15â µm band. The infrared PBS demonstrated commendable environmental reliability, in addition to exhibiting excellent spectral characteristics.
RESUMEN
HfO2 films are widely used for optical coatings due to the high refractive index and low absorption, especially in the ultraviolet (UV) band. In this work, HfO2 film samples were prepared with the optimized assistant source power and deposition temperature by dual-ion beam sputtering (DIBS), followed by annealing treatments in vacuum and atmosphere, respectively. For samples with different annealing temperatures from 200 to 450 °C, the microstructure, morphology, film stress and optical properties from 200 to 1000â nm were systematically investigated. A monoclinic phase, a refractive index inhomogeneity along the film thickness and an absorption of shoulder-shape in the 250-300â nm band were found in the as-deposited samples. For samples annealed in vacuum, 400 °C annealing leaded to more oxygen defects, which in turn caused aggravated UV absorption. For samples annealed in atmosphere, the shoulder-shaped absorption weakened obviously above 300 °C annealing, which was suspected due to the reduction of oxygen defects during the crystallization process with sufficient oxygen. Scattering loss was investigated and found negligible for as-deposited and annealed samples. Additionally, film stress varied from compressive state to tensile state with increasing annealing temperature, and the zero-stress temperature is between 300-350 °C, which is due to the obvious crystallization behavior. Production methods and physical mechanisms for low absorption and scattering loss DIBS deposited HfO2 films were proposed and discussed in detail.
RESUMEN
Optimizing the atomic layer deposition (ALD) process of films is particularly important in preparing multilayer interference films. In this work, a series of Al2O3/TiO2 nano-laminates with a fixed growth cycle ratio of 1:10 were deposited on Si and fused quartz substrates at 300 °C by ALD. The optical properties, crystallization behavior, surface appearance and microstructures of those laminated layers were systematically investigated by spectroscopic ellipsometry, spectrophotometry, X-ray diffraction, atomic force microscope and transmission electron microscopy. By inserting Al2O3 interlayers into TiO2 layers, the crystallization of the TiO2 is reduced and the surface roughness becomes smaller. The TEM images show that excessively dense distribution of Al2O3 intercalation leads to the appearance of TiO2 nodules, which in turn leads to increased roughness. The Al2O3/TiO2 nano-laminate with a cycle ratio 40:400 has relatively small surface roughness. Additionally, oxygen-deficient defects exist at the interface of Al2O3 and TiO2, leading to evident absorption. Using O3 as an oxidant instead of H2O for depositing Al2O3 interlayers was verified to be effective in reducing absorption during broadband antireflective coating experiments.
