Berlin 2012 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 22: Trends in atomic layer deposition I (Focused session – Organizer: Nielsch)
DS 22.4: Vortrag
Mittwoch, 28. März 2012, 16:30–16:45, H 0111
Highly Efficient Embedded Transmission Gratings — Stephan Ratzsch1, •Frank Fuchs2, Adriana Viorica Szeghalmi1, Ernst-Bernhard Kley1, and Andreas Tünnermann2 — 1Institut für Angewandte Physik, Friedrich-Schiller-Universität Jena, 07745 Jena — 2Institut für optische Feinwerktechnik, Fraunhofer-Gesellschaft, 07745 Jena
We present a new approach for realization of a highly efficient transmission grating for TM polarized light operating at 1030 nm wavelength. It had been theoretically shown that it is possible to reach 100 % diffraction efficiency for a fused silica grating embedded within a high refractive index material. High quality, homogenous and void free coatings are required to achieve high optical efficiency. Plasma enhanced atomic layer deposition (PEALD) meets the enormous demands posed by these embedded gratings; however, film thickness homogeneity (less than 2% non-uniformity) and low surface roughness are essential. Titanium (IV) oxide (TiO2) is a potential candidate for the high index embedding material because of its adequate optical properties in the near infrared spectral range. The grating parameters (period, height, line width, etc.) have been optimized by rigorous coupled wave analysis (RCWA). These parameters depend on the refractive index of the titania layer. Therefore the refractive index and extinction should be precisely controlled. The refractive index of titania deposited by thermal ALD processes is generally highly sensitive to the temperature of the substrate. In contrast, the titania films produced by PEALD between 80°C and 210°C have a high refractive index.