Abstract-Terahertz tag identifiable through shielding materials using machine learning

Ryoya Mitsuhashi, Kosuke Murate, Seiji Niijima, Toshinari Horiuchi, Kodo Kawase,

(a) Tags used for real-time identification. Natural leather was used as the shielding material. Tags are shown for Chemicals A, B, and C (from the right) and were attached to the shielding material. Tags were moved in the direction of the arrow. (b) Images of the detection beams of the multi-wavelength is-TPG without tag insertion. For this measurement, we selected three wavelengths to match the absorption peaks of each tag. (c) The intensity spectrum of each tag measured with a conventional is-TPG. The symbols show the intensities of the three frequencies selected in this study; the red and blue symbols represent the transmission and absorption frequencies, respectively. (d) We took screenshots showing the timing of the measurement of each tag’s position from the video of tag sweeping. The names of tags identified by convolutional neural network (CNN), and the identification probability, are shown in the upper right corner.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-3-3517

In recent years, there has been great interest in chipless radio-frequency identification (RFID) devices that work in the terahertz (THz) frequency range. Despite advances in RFID technology, its practical use in the THz range has yet to be realized, due to cost and detection accuracy issues associated with shielding materials. In this study, we propose two types of low-cost THz-tags; one is based on the thickness variation of coated polyethylene and the other on the fingerprint spectra of reagents. In the proposed approach, machine learning, specifically a deep-learning method, is used for high-precision tag identification even with weak signals, or when the spectrum is disturbed by passing through shielding materials. We achieved almost 100% identification accuracy despite using an inexpensive tag placed under thick shielding materials with an attenuation rate of about −50 dB. Furthermore, real-time tag identification was demonstrated by combining a multiwavelength injection-seeded THz parametric generator and a convolutional neural network.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Adaptive spatiotemporal optical pulse front tilt using a digital micromirror device and its terahertz application

Kosuke Murate, Mehraveh Javan Roshtkhari, Xavier Ropagnol, and François Blanchard

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-9-2090&origin=search

We report a new method to temporally and spatially manipulate the pulse front tilt (PFT) intensity profile of an ultrashort optical pulse using a commercial microelectromechanical system, also known as a digital micromirror device (DMD). For our demonstration, we show terahertz generation in a lithium niobate crystal using the PFT pumping scheme derived from a DMD chip. The adaptive functionality of the DMD could be a convenient alternative to the more conventional grating required to generate a laser beam with a PFT intensity profile that is typically used for efficient optical rectification in noncollinear phase-matching conditions. In contrast to a grating, PFT using DMD does not suffer from wavelength dispersion, and exhibits overlap properties between grating and a stair-step echelon mirror.

© 2018 Optical Society of America

Abstract-Injection-seeded THz parametric generator/amplifier

Kodo Kawase,  Kosuke Murate,

http://ieeexplore.ieee.org/document/8083975/

We report a THz-wave amplifier using nonlinear optical effects in MgO:LiNbO3 crystals. The amplifier operates at room temperature and has a gain of 55 dB based on the fundamental principle of injection-seeded THz parametric generator/detector.

Non-destructive drug inspection in covering materials using a terahertz spectral imaging system with injection-seeded terahertz parametric generation and detection

Mikiya Kato,1 Saroj R. Tripathi,1,* Kosuke Murate,1 Kazuki Imayama,1 and Kodo Kawase1,2

 Graduate School of Engineering, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya, 464-8603 Japan 2 RIKEN, 519-1399, Aramaki-Aoba, Aoba, Sendai 980-0845, Japan
 * tripathi@nuee.nagoya-u.ac.jp

https://www.osapublishing.org/view_article.cfm?gotourl=https%3A%2F%2Fwww%2Eosapublishing%2Eorg%2FDirectPDFAccess%2FCA54CE12-0741-BABF-8F2A4AF83A0398A0_338151%2Foe-24-6-6425%2Epdf%3Fda%3D1%26id%3D338151%26seq%3D0%26mobile%3Dno&org=

Abstract: In 2003, we reported the first-ever development of a spectral imaging system for illicit drugs detection using a terahertz (THz) wave parametric oscillator (TPO) [K. Kawase et al., Opt. Exp. 11(20), 2549 2003]. The system has a dynamic range below four orders of magnitude, which enables it to identify reagents only through thin envelopes using spectral imaging. Recently, we succeeded in developing a high power and high sensitivity THz wave spectral imaging system using injection-seeded THz parametric generation and detection. A dynamic range in excess of 80 dB has been obtained, which is much higher than that of the 2003 system. In this study, the new spectral imaging system successfully identified reagents through thicker material than the thin envelopes used previously.
 ©2016 Optical Society of America

Abstract-Terahertz wave three-dimensional computed tomography based on injection-seeded terahertz wave parametric emitter and detector

Saroj R. Tripathi, Yuya Sugiyama, Kosuke Murate, Kazuki Imayama, and Kodo Kawase

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-6-6433

We demonstrate a high dynamic range, three-dimensional (3-D) terahertz (THz) wave computed tomography system in which frequency tunable, Fourier transform-limited, high-power THz waves are emitted by an injection-seeded parametric source and ultrasensitive detection of THz waves is accomplished by heterodyne detection. This system covers the frequency range of 0.95 to 2.7 THz and has a maximum dynamic range in excess of nine orders of magnitude, enabling the acquisition of high-resolution 3-D tomographic images of samples with strong THz absorption. As an illustration, we obtained 3-D computed tomographic images of a pencil and a plastic product with an internal defect that demonstrates the potential applications of our imaging system in non-destructive testing and evaluation of industrial products.

© 2016 Optical Society of America

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