Abstract-d carrier-density dependence of electron-hole scattering in silicon investigated by optical-pump terahertz-probe spectroscopy

T. Terashige, H. Yada, Y. Matsui, T. Miyamoto, N. Kida, and H. Okamoto

Phys. Rev. B 91, 241201(R) – Published 5 June 2015

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.241201

We measured the optical conductivity σ̃(ω) spectra of photodoped silicon by optical-pump terahertz-probe spectroscopy and analyzed them with a two-carrier Drude model. Taking into account the values of electron (hole)-phonon scattering rates previously reported in chemically doped silicon, we evaluated the electron-hole scattering rates γe-h. From 293 to 90K, the magnitudes and temperature dependence of γe-hwere successfully reproduced by a theoretical model including the effects of Rutherford scattering, Coulomb screening, and Pauli exclusion. This suggests that these three factors dominate electron-hole scattering processes in silicon. Below 90K, γe-hbecomes larger than that of the theoretical curve, which is attributable to a prolongation of the relaxation time of hot carriers.

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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