Abstract-Terahertz-wave generation from surface phonons at forbidden frequencies of lithium niobate

Jun-ichi Shikata, Seigo Ohno, Hiroaki Minamide,

https://www.jstage.jst.go.jp/article/elex/advpub/0/advpub_17.20200133/_article

This paper describes terahertz (THz)-wave generation within forbidden bands in polar crystals, focusing on the A1 phonon modes in lithium niobate. This material exhibits two negative-permittivity frequency ranges at 7.4-12.7 THz and 18.8-25.6 THz for the lowest and highest A1 modes, respectively. Exploiting the finite-difference time-domain simulations, we demonstrate that both the surface phonon modes can be radiative with a structured grating. Fourier analyses of the radiative fields reveal the relevant peaks in the spectrum as well as the dispersion relations. Our results provide a novel method for coherent THz-wave sources at unexplored THz frequencies.

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/abstract/10.1103/PhysRevA.93.043836

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 ultrabright THz-wave generation from SRS under stimulated Brillouin scattering suppression with subnanosecond 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 ultrabright tabletop THz-wave sources for various applications.

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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.