Abstract-Terahertz emission from gold nanorods irradiated by ultrashort laser pulses of different wavelengths

Keisuke Takano, Motoki Asai, Kosaku Kato, Hideaki Komiyama, Akihisa Yamaguchi, Tomokazu Iyoda, Yuzuru Tadokoro, Makoto Nakajima, Michael I. Bakunov

https://www.nature.com/articles/s41598-019-39604-5

Electron photoemission and ponderomotive acceleration by surface enhanced optical fields is considered as a plausible mechanism of terahertz radiation from metallic nanostructures under ultrafast laser excitation. To verify this mechanism, we studied experimentally terahertz emission from an array of gold nanorods illuminated by intense (~10–100 GW/cm2) femtosecond pulses of different central wavelengths (600, 720, 800, and 1500 nm). We found for the first time that the order of the dependence of the terahertz fluence on the laser intensity is, unexpectedly, almost the same (~4.5–4.8) for 720, 800, and 1500 nm and somewhat higher (~6.6) for 600 nm. The results are explained by tunneling currents driven by plasmonically enhanced laser field. In particular, the pump-intensity dependence of the terahertz fluence is more consistent with terahertz emission from the sub-cycle bursts of the tunneling current rather than with the ponderomotive mechanism.

Abstract-Terahertz wave emission from plasmonic chiral metasurfaces

Takahiro Matsui, Satoshi Tomita , Motoki Asai, Yuzuru Tadokoro, Keisuke Takano, Makoto Nakajima, Masanori
http://link.springer.com/article/10.1007%2Fs00339-016-9657-y

Plasmonic chiral metasurfaces with pinwheel-like structures are fabricated on silver films using a focused ion-beam milling technique. In time-domain spectroscopy, we observe terahertz (THz) wave emission from metasurfaces irradiated by a near-infrared Ti:sapphire ultrashort pulsed laser. The origin of the THz wave generation is likely to be tunnelling ionization accompanied with photoelectron acceleration by ponderomotive force. Numerical simulation is carried out toward improvement of the chiral metasurfaces for better emission of circularly polarized THz waves.

Abstract-Study of terahertz field induced coherer

Makoto Nakajima, Yuzuru Tadokoro, Keisuke Takano, and Masanori Hangyo
https://www.osapublishing.org/abstract.cfm?URI=nlo-2015-NTh2B.6

The electrical resistance falls down several orders for aluminum particles by single-shot terahertz intense pulse irradiation. We confirmed that the electron conduction paths are induced in a direction parallel to polarization of incident terahertz pulse.

© 2015 OSA

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Abstract-Coherent time-domain detection of terahertz pulses generated from noncollinear phase-matched, picosecond terahertz parametric oscillator

Yuzuru Tadokoro1, Yuma Takida2, Hiroshi Kumagai3, Shigeki Nashima4 and Masanori Hangyo1

http://iopscience.iop.org/1882-0786/7/2/022701/pdf/1882-0786_7_2_022701.pdf
tadokoro-y@ile.osaka-u.ac.jp

1 Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871, Japan
2 Tera-Photonics Laboratory, RIKEN Center for Advanced Photonics, Sendai 980-0845, Japan
3 Graduate School of Medical Sciences, Kitasato University, Sagamihara 252-0373, Japan
4 Graduate School of Engineering, Osaka City University, Osaka 558-8585, Japan
 

Yuzuru Tadokoro et al 2014 Appl. Phys. Express 7 022701. doi:10.7567/APEX.7.022701
Received 30 October 2013, accepted for publication 6 December 2013. Published 6 January 2014.
© 2014 The Japan Society of Applied Physics

With a photoconductive antenna, we demonstrate time-domain detection of terahertz (THz) pulses generated from a noncollinear phase-matched, picosecond THz parametric oscillator. Since time-domain detection enables us to detect THz waves sensitively, the dynamic range of the power spectrum is ~1000 times improved in comparison with that of a pyroelectric detector. Furthermore, multiple THz pulses are observed because of the time delay between arrayed Si prism couplers. When a single, larger Si prism coupler or a trapezoidal MgO:LN crystal is employed instead, single monocycle THz pulses are observed.