| Abstract [eng] |
An era of lasers began on the May 16th, 1960 [1] when Theodore Maiman demonstrated the first laser. His setup consisted of a ruby rod coated with silver on its surfaces, exposed to a high-power flash lamp to produce laser radiation. Shortly after, Paul D. Maker and colleagues [2] observed the first instance of laser-induced damage in dielectric films, as reported in their groundbreaking work. This discovery opened a new field of studies focused on the development and optimization of optical coatings. During the laser systems development the need for advanced optical coatings also grew. Techniques such as physical vapor deposition (PVD) [3] and chemical vapor deposition (CVD) [4] emerged, enabling the fabrication of increasingly complex and precise optical elements. The continuous enhancement of laser intensity and the reduction in pulse durations have driven demands for coatings with higher performance and reliability. The evolution of laser systems had a huge impact on many other fields of research, telecommunications, medicine, high-tech industry and others. Despite significant advancements, the optical elements in laser systems – such as anti-reflection (AR) coatings, mirrors, polarizers etc. remain a limiting factor in achieving further improvements. Modern deposition techniques now allow for the production of optical elements with exceptional sub-nm thickness precision, low absorption and stable refractive indices [5], [6]. Standard configuration using alternating high- and low-refractive-index materials provide the necessary optical properties. However, the high-refractive-index materials typically have lower band gap energy values, which reduce their resistance to laser radiation [7]. An innovative approach is needed in order to apply laser systems in everyday life more as the laser system dimensions are reduced by replacing existing optical components with more compact. A unique solution is proposed to form multilayer coating directly on existing elements in the microlaser systems (nonlinear crystals). The glancing angle deposition (GLAD) method presents a promising approach to address these challenges [8]. By adjusting the substrate tilt in terms of vapor flux during deposition process, GLAD enables control over the effective refractive index of materials. This allows for the creation of multilayer structures using only a single material, with refractive index contrast achieved through substrate deposition geometry manipulation. Such versatility facilitates the fabrication of AR coatings, high-reflection (HR) mirrors and other optical elements [8], [9]. Moreover, combining standard and nanostructured layers can further enhance the optical performance of existing components, making them more suitable for modern laser systems [10]. 9 The ability to engineer coatings with modified inner structure and effective refractive indices opens new technological possibilities for optical element design. A notable example is the application of nanostructured coatings to enhance total internal reflection (TIR) in YAG crystals, a critical component for zigzag cavity architectures in slab laser systems. These advanced coatings extend the range of the TIR phenomenon, enabling robust and efficient laser operations. However, challenges such as refractive index instability and environmental degradation – caused by humidity or the absorption of harmful particles – must be addressed. This thesis explores the design, fabrication and characterization of nanostructured coatings with a focus on their optical properties and durability. Firstly, various materials are analyzed to understand their potential for high-performance coatings. Secondly, fabrication techniques of all-silica mirrors and strategies how to prevent degradation, including environmental stabilization and annealing, are investigated. Thirdly, nanostructured coatings are deposited directly on YAG crystals and investigated. Unique designs are developed to induce the TIR phenomenon, demonstrating the feasibility of these coatings for zig-zag cavity architectures in slab laser systems. By addressing the technical and environmental challenges of nanostructured coatings, this research aims to contribute to the development of more robust and efficient optical elements for next-generation laser systems. |
