Efficient terahertz-wave generation and its ultrafast optical modulation in charge ordered organic ferroelectrics

• Published in: Applied physics letters Vol. 104; no. 17
• Main Authors: Itoh, Hirotake, Itoh, Keisuke, Goto, Kazuki, Yamamoto, Kaoru, Yakushi, Kyuya, Iwai, Shinichiro
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 28-04-2014
• Subjects: Applied physics; Deoxidizing; Domains; FERROELECTRIC MATERIALS; Ferroelectricity; MATERIALS SCIENCE; Modulation; NONLINEAR PROBLEMS; Organic compounds; POLARIZATION; Terahertz frequencies; TETRATHIAFULVALENE; Wave generation; ZINC TELLURIDES
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4871735

Efficient terahertz (THz) wave generation in strongly correlated organic compounds α-(ET)2I3 and α′-(ET)2IBr2 (ET:bis(ethylenedithio)-tetrathiafulvalene) was demonstrated. The spontaneous polarization induced by charge ordering or electronic ferroelectricity was revealed to trigger the THz-wave generation via optical rectification; the estimated 2nd-order nonlinear optical susceptibility for α-(ET)2I3 is over 70 times larger than that for prototypical THz-source ZnTe. Ultrafast (<1 ps) and sensitive (∼40%) photoresponse of the THz wave was observed for α-(ET)2I3, which is attributable to photoinduced quenching of the polarization accompanied by insulator(ferroelectric)-to-metal transition. Modulation of the THz wave was observed for α′-(ET)2IBr2 upon the poling procedure, indicating the alignment of polar domains.