Advanced Infrared Spectroscopy Co.

Hachiōji, Japan

Advanced Infrared Spectroscopy Co.

Hachiōji, Japan
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Tani M.,University of Fukui | Yamamoto K.,University of Fukui | Estacio E.S.,University of Fukui | Que C.T.,University of Fukui | And 5 more authors.
Journal of Infrared, Millimeter, and Terahertz Waves | Year: 2012

Recent studies on the techniques and development of photoconductive (PC) semiconductor devices for efficient generation and detection of terahertz (THz) pulsed radiation are reported. Firstly, the optimization of PC antenna design is discussed. The PC detection of THz pulsed radiation using low-temperature grown GaAs with 1.55-μm wavelength probe is then described. Finally, the enhancement of THz radiation from InSb by using a coupling lens and magnetic field is investigated. These results reveal valuable insights on the design of an efficient, compact, and cost-effective THz time-domain spectroscopy system based on 1.55-μm fs laser sources. © Springer Science+Business Media, LLC 2012.


Estacio E.S.,University of Fukui | Estacio E.S.,University of the Philippines at Diliman | Hibi M.,University of Fukui | Saito K.,University of Fukui | And 7 more authors.
Journal of Infrared, Millimeter, and Terahertz Waves | Year: 2013

The characteristics of low temperature-grown GaAs photoconductive antenna (PCA) terahertz detectors probed by 1.56 μm laser pulses are investigated. The influence of TM and TE polarized probe, as well as the saturation characteristics are studied for 2 μm- and 5 μm-gap PCA's. Different polarization characteristics at low probe powers and at the saturation regimes were observed. Results are explained in terms of the polarization-dependent photocarrier distribution at the PCA gap arising from tight focusing. This work also demonstrates using a 1.56 μm probe for a GaAs PCA to achieve ∼60 dB SNR; matching its performance characteristics for above-bandgap probes. © 2013 Springer Science+Business Media New York.


Furuya T.,University of Fukui | Estacio E.S.,University of Fukui | Horita K.,University of Fukui | Que C.T.,University of Fukui | And 5 more authors.
Japanese Journal of Applied Physics | Year: 2013

We propose a high-speed scanning terahertz (THz) time-domain spectrometer (TDS) based on optical sampling by repetition frequency modulation (OSREFM) using a repetition-frequency-tunable femtosecond fiber laser. Repetition frequency modulation is controlled by a highly stabilized external sweep generator. The fast scan of the time-delay between the pump and probe pulses is similar to an optical sampling with cavity tuning (OSCAT) THz-TDS system. However, the advantage of this technique is that it does not require physically moving components and uses only one laser system having an electronically modulated repetition rate. The time window and scanning time of this system depend on the modulation frequency range and the sweeping speed of the laser. In this study, we demonstrate the acquisition of a ̃300 ps-window THz time waveform within 3ms at a scan rate of 333Hz. © 2013 The Japan Society of Applied Physics.


Miyamaru F.,Shinshu University | Miyamaru F.,Japan Science and Technology Agency | Saito Y.,Shinshu University | Saito Y.,Hokkaido University | And 5 more authors.
Applied Physics Letters | Year: 2010

The dependence of the emission spectrum of terahertz (THz) radiation on the geometrical parameters of the dipole antenna, and the relationship between these parameters and the temporal characteristics of the transient current that generate THz radiation, is reported. The emission intensity and the peak frequency strongly depend on these geometrical parameters. This dependence varies significantly with changes in the temporal characteristics of the transient current. We have also found that the emission efficiency can be increased by increasing the aspect ratio for the dipole. © 2010 American Institute of Physics.


Miyamaru F.,Shinshu University | Miyamaru F.,Japan Science and Technology Agency | Yamamoto K.,University of Fukui | Furuya T.,University of Fukui | And 2 more authors.
IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide | Year: 2010

The dependence of the emission spectrum of terahertz (THz) radiation on the geometrical parameters of the dipole antenna, and the relationship between these parameters and the temporal characteristics of the transient input field is reported. The emission intensity and the peak frequency strongly depend on these geometrical parameters. © 2010 IEEE.


Nishizawa S.,Advanced Infrared Spectroscopy Co. | Nishizawa S.,Shinshu University | Suzuki Y.,Zensei Pharmaceutical Industries Co. | Iwamoto T.,Shinshu University | And 2 more authors.
IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide | Year: 2010

Terahertz time-domain spectroscopy technique has recently been in progress with advantages over other conventional techniques and with a wide range of industrial applications. One of the latest industrial applications focusing on the quality control on pharmaceutical products will be described. © 2010 IEEE.


Furuya T.,University of Fukui | Horita K.,University of Fukui | Quea Ch.T.,University of Fukui | Yamamoto K.,University of Fukui | And 4 more authors.
IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide | Year: 2010

In order to completely prevent the mixture of different medicines and also their contamination by foreign objects it is necessary to inspect all medicines in the manufacturing process. In line with this, THz time-domain spectroscopy (THz-TDS) is considered to be a promising technique applicable to the quality-control inspection system along the production line of chemicals and medicinal tablets. However, previous THz-TDS utilizes mechanical type time-delay scanning stage that requires several minutes in order to acquire a THz time waveform. Therefore, it is difficult to introduce this THz-TDS into the system. In the present study, we aim to develop a method for high-speed sampling of the THz waveform to significantly shorten the measurement time in the THz-TDS by changing the repetition rate of the femtosecond laser. The high-speed sampling method proposed was applied to a THz-TDS and the proof of principal experiment was done.


Itoh K.,Waseda University | Ikeda A.,Advanced Infrared Spectroscopy Co. | Iwamoto T.,Advanced Infrared Spectroscopy Co. | Nishizawa S.,Advanced Infrared Spectroscopy Co.
Journal of Molecular Structure | Year: 2011

Density functional theory (DFT) calculation was applied to simulate the far infrared (far-IR) spectra in the 700-0 cm-1 region of α-helical l-alanine oligomer models with the number of peptide bonds (n) of 24-8. The simulation for the model with n = 24 is in reasonable agreement with the dichroic IR spectra in the 700-60 cm-1 region already reported [K. Itoh and T. Shimanouchi, Biopolymers 9 (1970) 383], indicating the high reliability of the calculation. Terahertz (THz) time-domain spectroscopy was used to measure the far-IR spectra in the 160 - ca. 5 cm-1 region for poly-l-alanine in powder and film states. On treatment of the α-helical poly-l-alanine film with formic acid for 5 min a parallel band at 127 cm-1 and perpendicular bands at 116 and 82 cm-1 shift to 116, 109 and 73 cm-1, respectively, with concomitant intensity diminution, and on further treatment for 1 h the bands disappear and the far-IR spectrum in the region of 160 - ca. 5 cm-1 becomes almost transparent. On the other hand, the film treated with formic acid for 1 h still gives rise to the amides I and II bands due the α-helical structure with appreciable intensity. The calculated frequencies and intensities of bands corresponding to the observed bands at 127, 116 and 82 cm-1 decrease with decreasing the number of peptides bonds from 24 to 8, suggesting that the observed frequency lowering and intensity diminution are due to the decrease in the average number of the l-alanine residues forming the α-helix. After the treatment for 1 h the average number becomes too small to give the far-IR bands, resulting in the almost transparent spectral feature. The simulation also predicted the appearance of the accordion-like modes of the α-helical rod at 23 (n = 24), 26.5 (n = 20), 32 (n = 16), 39 (n = 12) and 48.5 cm -1 (n = 8) and the bending modes at 14 (n = 24), 19 (n = 20) and 27 cm-1 (n = 16). The observation of these modes, which should be called as "collective modes" in the strict sense of the word, will give information about static as well as dynamical structures of the α-helical sequences in polypeptides and proteins. © 2011 Elsevier B.V. All rights reserved.

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