Standard high reflectivity coatings consist of materials with high and low refractive indexes. Typically, optical resistivity of such elements is limited by the threshold value of material with high index. Combination of two deposition methods, namely ion-beam sputtering and oblique angle deposition, was used to form high reflectivity coatings for the wavelength of 355 nm. Variation of the design of standard coating and the number of top layers, deposited at oblique angle have been investigated. Laser induced damage thresholds, optical scattering, surface roughness, spectral performance etc. were tested for the experimental samples. Analysis indicate that combination of both deposition methods allows to enhance the optical resistivity of typical high reflictivity mirrors. Introducing standard method also allows to stabilize the spectra and reduce the losses of total optical component.
In present work, oblique angle deposition technique was employed to form nano-structured anisotropic layers evaporating amorphous materials. The combination of birefringent nano-structured and isotropic layers allows to form highly transparent (T ~ 99 %) wave-plates. Furthermore, such combination can be used to form two spectrally separated Bragg reflection zones for perpendicular polarizations. This feature allows to form polarizers for zero angle applications. Both elements can be manufactured using only one material by changing only its structural morphology what leads to superior LIDT value. In this work, the possibility to evaporate waveplates and polarizers for zero angle applications was shown.
Standard high reflectivity mirrors consist of layers with high and low refractive indexes. Typically, optical resistivity of such elements is limited by the threshold value of material with high index. Combination of two deposition methods, namely ion-beam sputtering and glancing angle deposition, was used to form high reflectivity mirrors for the wavelength of 355 nm. Variation of the design for standard coating and the number of top layers, deposited at oblique angle have been investigated. Laser induced damage thresholds, surface roughness, spectral performance etc. were tested for all the experimental samples. Analysis indicate that combination of both deposition methods allows to enhance the optical resistivity of typical high reflictivity mirrors. Fully sculptured thin film based mirrors also exhibit spectral instability and optical losses. Introducing standard method allows to stabilize the spectra and reduce the losses of total optical component.
Band-gap and refractive index are known as fundamental properties determining intrinsic optical resistance of multilayer dielectric coatings. By considering this fact we propose novel approach to manufacturing of interference thin films, based on artificial nano-structures of modulated porosity embedded in high band-gap matrix. Next generation all-silica mirrors were prepared by GLancing Angle Deposition (GLAD) using electron beam evaporation. High reflectivity (HR) was achieved by tailoring the porosity of highly resistant silica material during the thin film deposition process. Furthermore, the proposed approach was also demonstrated to work well in case of anti-reflection (AR) coatings. Conventional HR HfO2 and SiO2 as well as AR Al2O3 and SiO2 multilayers produced by Ion Beam Sputtering (IBS) were used as reference coatings. Damage performance of experimental coatings was also analyzed. All-silica based GLAD approach resulted in significant improvement of intrinsic laser damage resistance properties if compared to conventional coatings. Besides laser damage testing, other characteristics of experimental coatings are analyzed and discussed – reflectance, surface roughness and optical scattering. We believe that reported concept can be expanded to virtually any design of thin film coatings thus opening a new way of next generation highly resistant thin films well suited for high power and UV laser applications.
Laser induced damage of optical coatings has been one of the most important targets during many decades of intensive research. Different techniques were used and explored with the aim to increase the resistance of multilayer systems to laser pulses. In this work, LIDT results of different “base” structures made by ion beam sputtering of Al<sub>2</sub>O<sub>3</sub>, SiO<sub>2</sub> and their mixtures are presented, and further enhancement possibilities are discussed by applying additional layer structure using higher bandgap material – fluorides and glancing angle deposited SiO<sub>2</sub>.
Optical elements for polarization control are one of the main parts in advanced laser systems. The state and intensity of polarized light is typically controlled by optical elements, namely waveplates. Polymers, solid or liquid crystals and other materials with anisotropic refractive index can be used for production of waveplates. Unfortunately, most of aforementioned materials are fragile, unstable when environmental conditions changes, difficult to apply in microsystems and has low resistance to laser radiation. Retarders, fabricated by evaporation process, do not consist any of these drawbacks. In order to manufacture such optical components with high quality, characterisation of deposition parameters are essential. A serial bi-deposition method was employed to coat anisotropic layers for polarisation control. Such waveplate can be deposited on micro optics or other optical elements, essentially improving compact optical systems. The range of available materials is limited by absorption losses for waveplates in UV spectral region. Therefore, the investigation was accomplished with four eligible candidates – TiO<sub>2</sub>, LaF<sub>3</sub>, Al<sub>2</sub>O<sub>3</sub> and SiO<sub>2</sub>. Structural (XPS, XRD) and optical (spectrophotometry, ellipsometry) analysis have shown Al<sub>2</sub>O<sub>3</sub> and SiO<sub>2</sub> as the most applicable materials for UV spectral region.
Laser resistance of optical elements is one of the major topics in photonics. Various routes have been taken to improve optical coatings, including, but not limited by, materials engineering and optimisation of electric field distribution in multilayers. During the decades of research, it was found, that high band-gap materials, such as silica, are highly resistant to laser light. Unfortunately, only the production of anti-reflection coatings of all-silica materials are presented to this day. A novel route will be presented in materials engineering, capable to manufacture high reflection optical elements using only SiO<sub>2</sub> material and GLancing Angle Deposition (GLAD) method. The technique involves the deposition of columnar structure and tailoring the refractive index of silica material throughout the coating thickness. A numerous analysis indicate the superior properties of GLAD coatings when compared with standard methods for Bragg mirrors production. Several groups of optical components are presented including anti-reflection coatings and Bragg mirrors. Structural and optical characterisation of the method have been performed and compared with standard methods. All researches indicate the possibility of new generation coatings for high power laser systems.
Technological developments in laser technology require advancements in optical components. Such demand is particularly important in UV spectral region. Antireflection coatings (AR) and waveplates as a widely used optical elements were produced based on glancing angle deposition (GLAD) method. Superior optical performance was measured for AR thin films. Broadband and broad-angle antireflection coatings were manufactured by using multilayer system when changing the refractive index profile by varying the porosity of material. SiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub> and LaF<sub>3</sub> materials were used for formation of waveplates for UV region. An investigation of optical and resistant performance were conducted. All materials showed optical losses at the wavelength of 355 nm. Possible technological solutions are presented and investigated.
The stresses in thin films are one of the main problems in the development of small dimensions or thin optical components. In order to produce low-tension anisotropic coatings, the characterization of serial bideposition is essential. Structural and optical performance have been tested for anisotropic TiO2 thin films deposited by serial bideposition technique. Three-dimensional surface interferometric measurements were performed for samples deposited at various angles. Also experimental observations of anisotropic tensions in annealed two-dimensional sculptured thin films of TiO2 material are presented. The deposition angle of 80 deg is considered to be the most applicable for developing optical components due to the befitting optical performance and the lowest tensions before and after the annealing.