Atomic Layer Deposition coatings for complex substrates

Atomic layer deposition (ALD) is a promising method for depositing conformal thin films on complex structure substrates leveraging the self-limiting nature of surface reactions inherent in the ALD process. The application of ALD is especially important for manufacturing of optical coatings on complex structure substrates (small dimensions (1-3 mm and less), low-radius, multi-prism prisms, gratings, etc.) as well as temperature and environment sensitive substrates. During the past few years ALD was used to deposit coatings on substrates such as DKDP, KYW, KGW, synthetic diamond, YLF, CaF, GaSe, GaAs based solar cells, fiber optics and free-form multi-level micro-optics.

Dense coatings with controlled dispersion for ultrashort pulses

Dispersive mirrors for ultrashort pulse compression require high precision deposition ensuring sub nanometer accuracy of deposited layers. Ion beam sputtering technology enables us to form dense layers and deposit homogenous multilayer coatings featuring negative or low GDD values.

Additionally, we have expertise to predict and optimize various other parameters including but not limited to: stress induced curvature, LIDT, light absorption.

Currently, possibilities to merge IBS deposition technology with GLAD deposited layers were tested in order to expand the application range even further.

Periodically modulated coatings

Coatings deposition on periodically modulated surfaces enables the fabrication of 2D and 3D photonic crystals. Our advanced control of the layer growth on periodically modulated structures improves and provides new possibilities to manipulate optical characteristics of optics. Our current applications include but not limited to spatial filtering, the development of high-contrast 0 AOI polarizers and enhanced phase retardation.

Sculptured coatings

GLAD (Glancing Angle Deposition) technology allows precise control over the angle between the vapor flux and the substrate surface. This control enables the creation of multilayer coatings with varied porosity and structural characteristics for each layer. In ODL, sculptural coatings are formed and investigated using different materials (SiO2, LaF3, Al2O3, etc.). In the laboratory, we focus on further investigating three main GLAD topics:

• High-reflectance all-silica mirrors with super resistivity to laser radiation
• Anti-reflective coatings for high-power lasers
• Anisotropic coatings for zero-order waveplates and zero-angle polarizers

Plasma ion assisted deposition of metal oxides

Plasma ion assisted deposition (PIAD) technology is very attractive, since it allows to form dense, environment-stable films and tweak other important optical, mechanical film properties by adjusting plasma parameters. Research is based on plasma source Copra IS300 (CCR Technology GmbH) which is installed in PVD coating chamber VERA1100.

Current research activities are focused on HfO_2, SiO₂ films and corresponding multilayer structures by modification and optimization of optical properties, stress and LIDT.

Advanced substrate preparation for high power laser optics

Polished optical substrates usually have a so-called Beilby layer, which absorbs laser radiation. Therefore, potential of optical resistance of bare substrate or transparent optical coating is limited by occurring sub-surface damage within the Beilby layer. Research activities are targeted for investigating oxygen and argon plasma properties, other important factors to effectively remove this subsurface layer without any negative impact, such as increased surface roughness, additional contamination, etc. Main activities are related to:

• Plasma etching of fused silica and different laser crystals, such as YAG, MALO (Co dopped spinel), BSO.
• Deposition and investigation of anti-reflective, polarizing coatings by different coating technologies on plasma etched substrates.

Transparent conducting films

Transparent conducting films (TCFs) are very thin coatings, characterized by good electrical conductivity and optical transparency. These coatings are widely used in various electronic devices such as liquid crystal displays, light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), touch screens, or photovoltaic cells. Also, these coatings can be applied in laser systems, smart windows, or other photonic technologies. Such coatings are usually used as transparent electrodes, capacitive sensors, and electrochromic or electrochemical layers that can change their transparency depending on voltage or change their electrical conductivity depending on environmental changes. According to the application area, we can design and optimize the spectral transmittance of the coating with electrical conductivity. We can produce ultra-thin metallic coatings and transparent electrically conductive coatings from various materials.