This is a study of the potential of IBS for the production of high-quality ITO layers for optical applications with additional electrical requirements. The electrical properties of ITO layers combined with underlying optical interference layers and their optical properties and surface roughness are presented.
Femtosecond and picosecond pulses can find many applications if they can be produced with laser sources that are not only powerful and efficient but also compact and reliable. In continuous wave operation, diode pumping of solid-state lasers has allowed for a rapid progress towards powerful, compact and reliable sources, while the often used technique of Kerr lens modelocking for pulsed operation tends to be in conflict with requirements for diode-pumpable high power designs. Passive modelocking with semiconductor saturable absorber mirrors solves this problem as it relaxes the restrictions on the cavity design. We report on our recent achievements in this field. In particular we present a novel semiconductor device for dispersion compensation and various improved diode-pumped passively modelocked lasers. Also we show which laser parameters determine the stability of a passively modelocked lasers against Q-switching instabilities.
We have fabricated InGaAs/InP PIN diodes with a coplanar waveguide design. The diodes have been integrated in a two- chip wavelength-selective Fabry-Perot filter for the use as wavelength-selective PIN receivers for dense wavelength division multiplex systems.
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.
In this presentation the design concept of an instrument for measuring total integrated scattering with a resolution limit of 0.1 ppm will be described. Furthermore the result of a theoretical model will be given which includes the scattering contributions from the front and the back surface of a transparent substrate. With the result obtained, surface roughness and power spectral density functions of the individual substrate surfaces can be calculated from scatter measurements. The improved measurement facility of the instrument in conjunction with the developed theoretical model allows surface characterization of transparent substrates in case of negligible volume scattering of the bulk material. Measurement results will be presented verifying the results of the model and showing the instrument's ability to characterize polishing quality of transparent substrates. Scatter losses as low as 0.6 ppm corresponding to 1 angstrom rms surface roughness have been determined measuring a `superpolished' transparent fused quartz substrate.
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.
A laser calorimeter, which is able to measure absorption as los as 1 - 10-6 of incident laser power even with the use of an argon laser of less than 1 W at 514.5 nm, was developed. The required stability of the temperature background is achieved by a special design of the measurement system minimizing heat flow. Evaluation of absorption is realized by numerical simulations taking into account all relevant processes of heat generation and dissipation. Furthermore, absorption is determined according to ISO/DIS 11 551. Interference influences from the substrate are taken into account.
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