The Optical Security and Performance (OSP) division of VIAVI Solutions just celebrated its 75th anniversary. With over $300M annual revenue OSP is one of the largest optical coating providers worldwide. OSP’s market focus is on anti-counterfeiting, automotive, consumer electronics, government & aerospace, and spectral sensing. In this presentation we will highlight some of OSPs industrial challenges and recent accomplishments to serve our customers. One focus will be on consumer electronics filters with rapid innovation demand especially towards miniaturization, while demanding high volumes with exceptional optical performance, accompanied by large price pressure. A second focus will be on components for free-space optical communications, where optics tend to be larger form factors. Tight wavefront aberration requirements drive tight specifications for substrate quality and coating requirements. We will discuss metrology investments that enable development and product assurance.
In many coating chambers substrates are moved by simple or planetary rotary motion systems. Isaac Newton already
taught that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force. To
move a substrate on a rotary trajectory, centripetal and gravitational forces must act upon the substrate. The substrate
must be somehow confined. Confinement options range from firm attachment to a fixture to loose placement in a pocket.
Depending on the rotary motion pattern, a loosely held substrate may slide once against a confinement boundary and
then stay, or may constantly slide around. 'Rattling around' may be undesirable as it could lead to edge destruction,
debris formation, precession of the substrate, and other adverse effects. Firm attachment is advantageous in most cases,
but often adds process complexity. We examine the forces present on substrates in typical rotary motion systems and
discuss the implications of different confinement methods.
The measurement of total scatter losses is a major prerequisite for the development, optimization and commercialization of high quality optical components. Especially in laser technology, optical scattering gained of importance in the source of the development of laser system with ever increasing output power and improved beam parameters. Besides its influence on the efficiency of laser systems and the beam steering arrangement, total scattering is an important safety aspect for application of these laser systems in materials processing, medicine and fundamental research. As a consequence of this global trend, working groups of TC 172/SC 9 initialized the development of an International Standard for the measurement of total scattering in optical components.
Ion beam sputtered SiO2 and TiO2 optical thin films are investigated. The optical properties absorption, light scattering and refractive index and the mechanical properties thickness, density and stress are studied directly after deposition and the posttreatment by isochromal annealing up to 300 degree(s)C. Absorption losses of SiO2 single layers decrease under annealing. The corresponding extinction is reduced below 1 X 10-6 at 514 nm. The dynamics of this process is investigated. The density which is higher than bulk density decreases, while the thickness increases. TiO2 single layers show a more complex behavior under postannealing. At higher temperatures this behavior is dominated by crystallite growth in anatase and rutile modification. Compressive stress is reduced. The single layer results of both materials are compared with those of double layers and Fabry Perot multilayers. Differences in absorption are discussed. In double layer systems, lowest bulk extinction of TiO2 is estimated with 1.5 X 10-5 at 514 nm. An irreversible peak shift of Fabry Perot filters after annealing comes from changes in thickness and refractive index. The overall performance of multilayer systems can be improved by an adapted annealing procedure.
A software tool for the simulation of ion beam sputter deposition is presented. All calculations are performed in 3D space using the original deposition chamber geometry. Starting at the extraction grid of the ion gun the distribution of the ion beam at the target is determined. A special version of transport of ions in matter code is applied to simulate the sputtering process. Using the energy and angular distribution of all sputtered and reflected atoms, the energy deposition as well as growth rates and particle compositions at any location and orientation in the deposition chamber can be calculated. Some experimental results of growth rates and optical absorption losses of SiO2 and TiO2 layers are presented and are compared to the results of simulation.
Absorption losses in ion beam sputtered films of SiO2 and TiO2 were examined. Two different processes contribute to the absorption of the films. The first process is the incorporation of impurities from the target itself, the ion source and the target surroundings into the films. The second is the damage of the films if a too large amount of energy is transferred to them by the sputtered and reflected particles. Impurity incorporation was minimized by a special coating chamber configuration and the use of electron cyclotron resonance ion and electron sources. The contaminations are examined by Secondary Ion Mass Spectrometry, using ion implantations for quantification. The influence of the main impurity parts on absorption is determined by controlled addition of impurities to the films. Experimental results show a large influence of the sputter gas, the reactive gas flow and the kind of target on absorption. Numerical sputter simulations revealed the correlation of these results with energy transport to the films. Reducing energy deposition in the films reduces their absorption. Low absorption in ion beam sputtering can only be achieved using metal targets.
An instrument for direct optical monitoring of film grown during deposition was developed. The transmittances of the original substrates, rotating for homogeneity reasons, are measured. The instrument is equipped with a double detection system including a linear photodiode array and a photomultiplier tube, working at different variable wavelengths. The design of the instrument, the main features and first produced optical devices are described.
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