Materials Sciences and Applications, 2015, 6, 445-455 Published Online May 2015 in SciRes. http://www.scirp.org/journal/msa http://dx.doi.org/10.4236/msa.2015.65048 How to cite this paper: Guenther, K., Sonntag, F., Roch, T. and Lasagni, A.F. (2015) Optical Properties of Tetrahedral Amorphous Carbon Films and Their Potential for Lab-on-a-Chip. Materials Sciences and Applications, 6, 445-455. http://dx.doi.org/10.4236/msa.2015.65048 Optical Properties of Tetrahedral Amorphous Carbon Films and Their Potential for Lab-on-a-Chip Katja Guenther 1* , Frank Sonntag 2 , Teja Roch 2,3 , Andrés Fabián Lasagni 2,3 1 University of Applied Sciences Mittweida, Mittweida, Germany 2 Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany 3 TU Dresden, Institute of Manufacturing Technology, Dresden, Germany Email: * guenther@creavac.de , Frank.Sonntag@iws.fraunhofer.de , Teja.Roch@iws.fraunhofer.de , Andres-Fabian.Lasagni@iws.fraunhofer.de Received 1 April 2015; accepted 24 May 2015; published 27 May 2015 Copyright © 2015 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract In this study, tetrahedral amorphous carbon (ta-C) films with thicknesses between several 100 nm and several micrometers have been deposited onto polished tungsten carbide and steel substrates by pulsed laser deposition (PLD) using an excimer laser (248 nm wavelength). We investigate the optical properties (e.g. the refractive index (n) and extinction coefficient (k) in the visible and near-infrared wavelength range) of these layers in dependence of the used laser ablation fluence on the target. It is shown that n of ~2000 nm thick ta-C films can be tuned, depending on the sp 3 -content, between n = 2.5 and 2.8 at a wavelength of 632 nm. Besides of this k reduces with the sp 3 -content and is as low as 0.03 at sp 3 -contents of more than 75%. We proof that this gives the opportunity to prepare coating with tailored optical properties. Furthermore, it is shown that the ta-C films have low background fluorescence in the wavelengths range of 380 - 750 nm, which make this thin films attractive for certain optical, medical and biotechnological applications. We present for the first time that one possible application is the use in Lab-on-a-Chip-systems (LOC). Within these systems, the ultrasensitive detection of fluorescence markers and dyes is a challenge. In order to increase the signal-to-noise-ratio, a setup was developed, that used the specific optical properties of ta-C films produced by PLD. We used the ta-C film as an integrated reflector that combined low background fluorescence, a low reflectivity at the excitation wavelength and the high reflectivity at the emission wavelength. We prove that this setup improves the detection of fluorescence photons. * Corresponding author.