Y. Ino

Numerical phase correction method for terahertz time-domain reflection spectroscopy

We propose a numerical method for the misplacement phase error correction in terahertz time-domain reflection spectroscopy (THz-TDRS). The developed algorithm is based on the maximum entropy principle and can be readily implemented into data processing, allowing one to reveal material parameters of the opaque materials from the THz reflection measurements. The method resolves the phase retrieval problem in the THz-TDRS and dramatically simplifies the experimental procedure.

Terahertz frequency Hall measurement by magneto-optical Kerr spectroscopy in InAs

We report on the time-domain terahertz (THz) magneto-optical Kerr spectroscopy in the frequency range from 0.5 to 2.5 THz. The developed technique employs reflection geometry, enabling high-frequency noncontact Hall measurements in opaque samples. We also present a method to reveal the off-diagonal component of the complex dielectric tensor from the measured polarization-dependent THz wave forms. At a static magnetic field of 0.48 T, a large Kerr rotation over 10° originating from magnetoplasma resonance is observed in an n-type undoped InAs wafer at room temperature. This indicates the strong potential of this material for the polarization modulator in the THz regime.

Detection and correction of the misplacement error in terahertz spectroscopy by application of singly subtractive Kramers-Kronig relations

In THz reflection spectroscopy the complex permittivity of an opaque medium is determined on the basis of the amplitude and phase of the reflected wave. There is usually a problem of phase error due to misplacement of the reference sample. Such experimental error brings inconsistency between phase and amplitude invoked by the causality principle. We propose a rigorous method to solve this relevant experimental problem by using an optimization method based upon singly subtractive Kramers-Kronig relations. The applicability of the method is demonstrated for measured data on an

Terahertz radiation emission from GaMnAs

n

Testing the validity of terahertz reflection spectra by dispersion relations

-type undoped (100) InAs wafer in the spectral range from

Reflection-type pulsed terahertz imaging with a phase-retrieval algorithm

0.5\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}2.5\phantom{\rule{0.3em}{0ex}}\mathrm{THz}

Power dissipation spectra and terahertz intervalley transfer gain in bulk GaAs under high electric fields

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Efficient dispersion relations for terahertz spectroscopy

Terahertz radiation is observed from ferromagnetic GaMnAs samples excited with 400nm wavelength pump pulses and is related to the sample magnetization M. The emission can be explained by the strong influence of M on the photogenerated carrier motion, a phenomenon related to the dc anomalous Hall effect. Results illustrate the potential of ferromagnetic materials to be used as compact terahertz sources emitting in a direction normal to the surface.

Determination of the time origin by the maximum entropy method in time-domain terahertz emission spectroscopy

Complex response function obtained in reflection spectroscopy at the terahertz range is examined with algorithms based on dispersion relations for integer powers of complex reflection coefficient, which emerge as a powerful and yet uncommon tools in examining the consistency of the spectroscopic data. It is shown that these algorithms can be used in particular for checking the success of the correction of the spectra by the methods of Vartiainen et al. [J. Appl. Phys. 96, 4171 (2004)] and Lucarini et al. [Phys. Rev. B. 72, 125107 (2005)] to remove the negative misplacement error in the terahertz time-domain spectroscopy.

Causality-based method for determining the time origin in terahertz emission spectroscopy

We propose and demonstrate a scheme for two-dimensional terahertz reflection imaging using a time-domain phase-retrieval algorithm based on the dispersion relations of complex reflection coefficients. With this scheme, topographic images—as well as the dielectric functions of a structured sample—can be obtained. A composite sample made of a semiconductor and metals is characterized within depth and lateral errors of 50μm and 100μm.