Abstract-Terahertz radiation induced by coherent phonon generation via impulsive stimulated Raman scattering in paratellurite

M. Sotome, N. Kida, R. Takeda, and H. Okamoto
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.90.033842

We report on the observation of terahertz radiation in a noncentrosymmetric insulating oxide, paratellurite (α−TeO2), by irradiation of a femtosecond laser pulse at room temperature. In the power spectrum of the terahertz radiation, an intensity fringe pattern with a period of ∼0.25 THz shows up below 3 THz. It can be reproduced by taking into account the effective generation length for the terahertz radiation with a poor phase-matching condition. In addition, a temporal oscillation component appears in the radiated terahertz wave with a frequency of ∼3.71 THz, which is in good agreement with the center frequency of the Raman active longitudinal optical E mode. On the basis of comprehensive polarized optical and Raman spectroscopic studies, we explain the generation mechanism of the temporal oscillation component in terms of the coherent phonon generation via impulsive stimulated Raman scattering.

DOI: http://dx.doi.org/10.1103/PhysRevA.90.033842

• 
• 
• 
• 
• 
• 
• 

Abstract-Visualization of ferroelectric domains in boracite using emission of terahertz radiation

http://arxiv-web3.library.cornell.edu/abs/1409.2960

Y. Kinoshita, N. Kida, M. Sotome, R. Takeda, N. Abe, M. Saito, T. Arima, H. Okamoto

(Submitted on 10 Sep 2014)

We report on the emission of terahertz radiation by irradiation of femtosecond laser pulses in non-centrosymmetric paraelectric and ferroelectric phases of Co3B7O13I boracite. The Generation of the terahertz waves in both phases is caused by optical rectification via a second-order nonlinear optical effect. In the ferroelectric phase, we successfully visualized ferroelectric domains by analyzing the polarization state of the terahertz wave radiated from the crystal. In a large area of the crystal (∼ 500 × 500 μm2), the observed polarization vector of the radiated terahertz wave was tilted from directions of spontaneous polarization, i.e., [100]cub, [010]cub, and [001]cub in cubic setting, which can be explained by the presence of a ferroelectric 90∘ domain wall of the (101)cub plane.

Abstract-Terahertz radiation by optical rectification in a hydrogen-bonded organic molecular ferroelectric crystal, 2-phenylmalondialdehyde

http://arxiv-web3.library.cornell.edu/abs/1409.2958v1

W. Guan, N. Kida, M. Sotome, Y. Kinoshita, R. Takeda, A. Inoue, S. Horiuchi, H. Okamoto

(Submitted on 10 Sep 2014)

Terahertz radiation by optical rectification has been observed at room temperature in a hydrogen-bonded organic molecular ferroelectric crystal, 2-phenyl malondialdehyde (PhMDA). The radiated electromagnetic wave consisted of a single-cycle terahertz pulse with a temporal width of ∼ 0.5 ps. The terahertz radiation amplitude divided by the sample thickness in PhMDA was nearly equivalent to that in a typical terahertz wave emitter ZnTe. This is attributable to a long coherence length in the range of 130 ∼ 800 μm for the terahertz radiation from PhMDA. We also discussed the possibility of PhMDA as a terahertz wave emitter in terms of the phase-matching condition.

Abstract-Circularly polarized narrowband terahertz radiation from a eulytite oxide by a pair of femtosecond laser pulses

Phys. Rev. A

R. Takeda, N. Kida, M. Sotome, Y. Matsui, and H. Okamoto

Accepted

3 March 2014

http://journals.aps.org/pra/accepted/ed072KfeZ5916c08a0998fc42cdd38fcd3e7d7fe5

We report on terahertz radiation induced by an optical rectification process in a non-centrosymmetric and insulating oxide, eulytite Bi4Ge3O12, at room temperature. The radiated terahertz pulse consists mainly of a temporal oscillation component with a frequency of 2.01 THz. The generation of this oscillation is ascribed to an increase in the effective generation length for the terahertz radiation up to about 2 mm at 2.01 THz. By using a pair of femtosecond laser pulses with an appropriate interval, polarization, and power, we succeeded in controlling the trajectory of the radiated terahertz wave. This method also enabled us to generate circularly polarized narrowband terahertz radiation with 2.01 THz