Abstract-Robust and accurate terahertz time-domain spectroscopic ellipsometry

Xuequan Chen, Edward P. J. Parrott, Zhe Huang, Hau-Ping Chan, and Emma Pickwell-MacPherson

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-6-8-768

In this work, we show how fiber-based terahertz systems can be robustly configured for accurate terahertz ellipsometry. To this end, we explain how our algorithms can be successfully applied to achieve accurate spectroscopic ellipsometry with a high tolerance on the imperfect polarizer extinction ratio and pulse shift errors. Highly accurate characterization of transparent, absorptive, and conductive samples comprehensively demonstrates the versatility of our algorithms. The improved accuracy we achieve is a fundamental breakthrough for reflection-based measurements and overcomes the hurdle of phase uncertainty.

© 2018 Chinese Laser Press

Abstract-Experimental and theoretical study of DNA gyrotropy at THz frequencies

A.V. Semenov,   Yu. Yu. Choporova,   O.P Cherkasova,  V. L. Vaks,  O. A. Smolyanskaya,

http://ieeexplore.ieee.org/document/8067200/

The theoretical calculations predicted shift of the absorption spectra of DNA solution in lower frequencies from B- to A-form. The experiments were carried out for DNA dissolved in water and 25% ethanol. Two different technique, THz time domain spectroscopy and THz ellipsometry at NovoFEL facility, were applied for measuring difference in dielectrical properties caused by conformational transmission.

Abstract-Terahertz ellipsometry study of the soft mode behavior in ultrathin SrTiO3 films

P. Marsik1,a), K. Sen1, J. Khmaladze1, M. Yazdi-Rizi1, B. P. P. Mallett1 and C. Bernhard1

1 Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Chemin du Musée 3, CH-1700 Fribourg, Switzerland

a) Electronic mail: premysl.marsik@unifr.ch

Appl. Phys. Lett. 108, 052901 (2016); http://dx.doi.org/10.1063/1.4940976

We present a combined study with time-domain terahertz and conventional far-infrared ellipsometry of the temperature dependent optical response of SrTiO3thin films (82 and 8.5 nm) that are grown by pulsed-laser deposition on (La0.3Sr0.7)(Al0.65Ta0.35)O3 (LSAT) substrates. We demonstrate that terahertz ellipsometry is very sensitive to the optical response of these thin films, in particular, to the soft mode of SrTiO3. We show that for the 82 nm film the eigenfrequency of the soft mode is strongly reduced by annealing at 1200 °C, whereas for the 8.5 nm film it is hardly affected. For the latter, after annealing the mode remains at 125 cm−1 at 300 K and exhibits only a weak softening to about 90 cm−1 at 10 K. This suggests that this ultrathin film undergoes hardly any relaxation of the compressive strain due to the LSAT substrate.

Abstract-Terahertz ellipsometry study of the soft mode behavior in ultrathin SrTiO3 films

Premysl Marsik, Kaushik Sen, Jarji Khmaladze, Meghdad Yazdi-Rizi, Benjamin P.P. Mallett, Christian Bernhard

http://arxiv.org/abs/1511.04521

We present a combined study with conventional far-infrared and time-domain terahertz ellipsometry of the temperature dependent optical response of SrTiO3 thin films (85 and 8.5 nm) that are grown by pulsed-laser deposition on LSAT substrates. We demonstrate that terahertz ellipsometry is very sensitive to the optical response of these thin films, in particular, to the soft mode of SrTiO3. We show that for the 85 nm film the eigenfrequency of the soft mode is strongly reduced by annealing at 1200 C, whereas for the 8.5 nm film it is hardy affected. For the latter, after annealing the mode remains at 125 cm-1 at 300 K and exhibits only a weak softening to about 90 cm-1 at 10 K. This suggests that this ultrathin film undergoes hardly any relaxation of the compressive strain due to the LSAT substrate.