Elliptically polarized terahertz radiation from a chiral oxide

• Published in: Applied physics letters Vol. 107; no. 13
• Main Authors: Takeda, R., Kida, N., Sotome, M., Okamoto, H.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 28.09.2015
• Subjects: Applied physics; CHIRALITY; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CONTROL; Ellipticity; Femtosecond pulses; Instrumentation industry; IRRADIATION; LASERS; Linear polarization; OPTICAL ACTIVITY; OXIDES; POLARIZATION; PULSES; TEMPERATURE RANGE 0273-0400 K; Terahertz frequencies; VARIATIONS; VELOCITY
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4932378

Polarization control of terahertz wave is a challenging subject in terahertz science and technology. Here, we report a simple method to control polarization state of the terahertz wave in terahertz generation process. At room temperature, terahertz radiation from a noncentrosymmetric and chiral oxide, sillenite Bi12GeO20, is observed by the irradiation of linearly polarized femtosecond laser pulses at 800 nm. The polarization state of the emitted terahertz wave is found to be elliptic with an ellipticity of ∼0.37 ± 0.10. Furthermore, the ellipticity was altered to a nearly zero (∼0.01 ± 0.01) by changing the polarization of the incident linearly polarized femtosecond laser pulses. Such a terahertz radiation characteristic is attributable to variation of the polarization state of the emitted terahertz waves, which is induced by retardation due to the velocity mismatch between the incident femtosecond laser pulse and generated terahertz wave and by the polarization tilting due to the optical activity at 800 nm.