Abstract-Verification of Non-thermal Effects of 0.3–0.6 THz-Waves on Human Cultured Cells

Noriko Yaekashiwa, Hisa Yoshida, Sato Otsuki, Shin’ichiro Hayashi,  Kodo Kawase

https://www.mdpi.com/2304-6732/6/1/33


Recent progress has been made in the development of terahertz (THz) waves for practical applications. Few studies that have assessed the biological effects of THz waves have been reported, and the data currently available regarding the safety of THz waves is inadequate. In this study, the effect of THz wave exposure on two cultured cells was assessed using a widely tunable THz source with a 0.3–0.6 THz frequency range, which can be used and increased in one GHz increments. The THz waves applied to the cultured cells were weak enough such that any thermal effects could be disregarded. The influence of THz wave exposure on both the proliferative and metabolic activities of these cells was investigated, as well as the extent of the thermal stress placed on the cells. In this work, no measurable effect on the proliferative or metabolic activities of either cell type was observed following the exposure to THz waves. No differences in the quantity of cDNA related to heat shock protein 70 was detected in either the sham or exposure group. As such, no differences in cellular activity between cells exposed to THz waves and those not exposed were observed

Abstract-Terahertz-wave parametric gain of stimulated polariton scattering

Yuma Takida, Jun-ichi Shikata, Kouji Nawata, Yu Tokizane, Zhengli Han, Mio Koyama, Takashi Notake, Shin’ichiro Hayashi, and Hiroaki Minamide

https://journals.aps.org/pra/accepted/9b07fY8bY8f1004d36744e58e4d414a59136e3566

We have experimentally determined the terahertz (THz)-wave parametric gain of stimulated Raman scattering (SRS) by phonon-polaritons in LiNbO3. Our approach is based on ultra-bright THz-wave generation from SRS under stimulated Brillouin scattering suppression with sub-nanosecond pump pulses. To obtain the frequency dependence of the parametric gain, we measured the crystal-length dependence of the THz-wave output directly using a surface-coupling configuration. We found that the product of the parametric gain and the threshold crystal length is constant throughout the tuning range. Our result provides a physical basis for the design and performance enhancement of SRS-based ultra-bright table-top THzwave sources for various applications.

Abstract-Kilowatt-peak Terahertz-wave Generation and Sub-femtojoule Terahertz-wave Pulse Detection Based on Nonlinear Optical Wavelength-conversion at Room Temperature

• Hiroaki Minamide, 
• Shin’ichiro Hayashi, 
• Koji Nawata, 
• Takunori Taira, 
• Jun-ichi Shikata, 
• Kodo Kawase

http://link.springer.com/article/10.1007%2Fs10762-013-0041-0

Intense Terahertz (THz)-wave generation and highly sensitive THz-wave detection were obtained by wavelength conversion with nonlinear optical susceptibility χ(2) of LiNbO3 crystals. Maximum peak output of about 50 kW (5 μJ/pulse) was demonstrated in an injection-seeded THz-wave parametric generator pumped by post-amplified emission from a microchip Nd:YAG laser. Using the sub-nanosecond pulse duration of the laser proposed herein provides effective mitigation of stimulated Brillouin scattering in LiNbO3, producing higher gain for wavelength conversion between near-infrared (near-IR) pump light and THz waves. Monochromatic THz radiation was obtained in the continuous tuning range of 0.7–2.9 THz. Additionally, highly sensitive THz-wave detection was demonstrated based on up-conversion from THz waves to near-IR light as well as efficient THz-wave generation. The signal generated with non-collinear phase-matching condition showed spectroscopic detection on the screen apart from the LiNbO3 crystal. Highly sensitive detection with minimum energy of about 80 aJ/pulse (0.8 μW at peak) and a large dynamic range of more than 100 dB were achieved in this experiment.