Birefringence measurement in the THz range based on double Fourier analysis

This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.39.000809. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law"A method for obtaining the average refractive indexes of a birefringent material in the terahertz region in a single measurement with a standard terahertz time-domain spectrometer is presented. The method is based on processing the frequency-domain interference between terahertz pulses and echoes through the Fourier transform of the terahertz spectrum. The technique also allows the determination of the optical axis orientation of the material by making two measurements with different angles of the sample optical axis. (C) 2014 Optical Society of AmericaThe authors thank the Erasmus Mundus scholarship and the Consejo Nacional de Investigaciones Cientificas y Tecnicas (Conicet) that support the work of Federico Sanjuan at Universitat Politecnica de Valencia and the Spanish Ministerio de Economia y Competitividad for partially supporting this work through project TEC2012-35797. Federico Sanjuan also thanks Dr. Jorge Tocho for his encouragement and support.Sanjuan, F.; Bockelt, AS.; Vidal Rodriguez, B. (2014). Birefringence measurement in the THz range based on double Fourier analysis. Optics Letters. 39(4):809-812. https://doi.org/10.1364/OL.39.000809809812394Wiesauer, K., & Jördens, C. (2013). Recent Advances in Birefringence Studies at THz Frequencies. Journal of Infrared, Millimeter, and Terahertz Waves, 34(11), 663-681. doi:10.1007/s10762-013-9976-4Jördens, C., Scheller, M., Wietzke, S., Romeike, D., Jansen, C., Zentgraf, T., … Koch, M. (2010). Terahertz spectroscopy to study the orientation of glass fibres in reinforced plastics. Composites Science and Technology, 70(3), 472-477. doi:10.1016/j.compscitech.2009.11.022Jördens, C., Scheller, M., Wichmann, M., Mikulics, M., Wiesauer, K., & Koch, M. (2009). Terahertz birefringence for orientation analysis. Applied Optics, 48(11), 2037. doi:10.1364/ao.48.002037Kim, Y., Yi, M., Kim, B. G., & Ahn, J. (2011). Investigation of THz birefringence measurement and calculation in Al_2O_3 and LiNbO_3. Applied Optics, 50(18), 2906. doi:10.1364/ao.50.002906Reid, M., & Fedosejevs, R. (2006). Terahertz birefringence and attenuation properties of wood and paper. Applied Optics, 45(12), 2766. doi:10.1364/ao.45.002766Katletz, S., Pfleger, M., Pühringer, H., Mikulics, M., Vieweg, N., Peters, O., … Wiesauer, K. (2012). Polarization sensitive terahertz imaging: detection of birefringence and optical axis. Optics Express, 20(21), 23025. doi:10.1364/oe.20.023025Duvillaret, L., Garet, F., & Coutaz, J.-L. (2000). Influence of noise on the characterization of materials by terahertz time-domain spectroscopy. Journal of the Optical Society of America B, 17(3), 452. doi:10.1364/josab.17.000452Grischkowsky, D., Keiding, S., van Exter, M., & Fattinger, C. (1990). Far-infrared time-domain spectroscopy with terahertz beams of dielectrics and semiconductors. Journal of the Optical Society of America B, 7(10), 2006. doi:10.1364/josab.7.00200