Abstract-Spectroscopy and sensing of fluid using terahertz waves

Toshiaki Hattori,  Katsuyoshi Aoki,  Borwen You,  Ja-Yu Lu,  Chin-Ping Yu

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10826/108260K/Spectroscopy-and-sensing-of-fluid-using-terahertz-waves/10.1117/12.2505842.short?SSO=1

Understanding of terahertz spectroscopic properties of materials is crucially important for applications of terahertz waves in sensing. Spectroscopic properties of water-rich media, such as biological tissues, gels, and aqueous solutions, are strongly affected by the amount and the dynamics of water in them. Terahertz spectroscopical measurements can clarify the dynamical and/or structural characteristics of water molecules in the hydrogen-bond network in these media. We studied the dynamical properties of water around protein molecules and polymers in aqueous solutions using terahertz spectroscopic measurements. Sensing of liquid using a terahertz waveguide composed of a metal rod array will also be described.

© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Abstract-Frequency-dependent skin penetration depth of terahertz radiation determined by water sorption–desorption

Borwen You, Ching-Yu Chen, Chin-Ping Yu, Pei-Hwa Wang, and Ja-Yu Lu

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-18-22709

A multilayered water–skin model is used to experimentally verify a new sensing method for determining the skin penetration depth of radiation with 0.1–0.9 terahertz (THz) frequencies. A water overlayer is dripped on a skin sample to form a multilayered structure for dynamically measuring the reflected THz-wave amplitude during water desorption. Skin penetration depths can be successfully derived by using the multilayered water–skin model and by considering the measured reflectivity, water dielectric constants, and effective thicknesses of the water overlayer on the skin sample. The maximum penetration depth is approximately 0.3 mm and is obtained with wave frequencies of 0.4–0.6 THz. This penetration depth encompasses the stratum corneum (SC) and part of the epidermis. The high penetration depth of 0.4–0.6 THz waves is also confirmed in the dried and damaged SC.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Terahertz artificial material based on integrated metal-rod-array for phase sensitive fluid detection

Borwen You, Ching-Yu Chen, Chin-Ping Yu, Tze-An Liu, Toshiaki Hattori, and Ja-Yu Lu

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-8-8571

A terahertz artificial material composed of metal rod array is experimentally investigated on its transmission spectral property and successfully incorporated into microfluidics as a miniaturized terahertz waveguide with an extended optical-path-length for label-free fluidic sensing. Theoretical and experimental characterizations of terahertz transmission spectra show that the wave guidance along the metal rod array originates from the resonance of transverse-electric-polarized waves within the metal rod slits. The extended optical path length along three layers of metal-rod-array enables terahertz waves sufficiently overlapping the fluid molecules embedded among the rods, leading to strongly enhanced phase change by approximately one order of magnitude compared with the blank metal-parallel-plate waveguide. Based on the enhanced phase sensitivity, three kinds of colorless liquid analytes, namely, acetone, methanol, and ethanol, with different dipole moments are identified in situ using the metal-rod-array-based microfluidic sensor. The detection limit in molecular amounts of a liquid analyte is experimentally demonstrated to be less than 0.1 mmol, corresponding to 2.7 μmol/mm2. The phase sensitive terahertz metal-rod-array-based sensor potentially has good adaptability in lab-chip technology for various practical applications, such as industrial toxic fluid detection and medical breath inspection.

© 2017 Optical Society of America

Abstract-Terahertz plasmonic waveguide based on metal rod arrays for nanofilm sensing

Borwen You, Chien-Chun Peng, Jia-Shing Jhang, Hungh-Hsuan Chen, Chin-Ping Yu, Wei-Chih Lai, Tze-An Liu, Jin-Long Peng, and Ja-Yu Lu  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-9-11340

Optics Express, Vol. 22, Issue 9, pp. 11340-11350 (2014)
http://dx.doi.org/10.1364/OE.22.011340

A high-aspect-ratio metallic rod array is demonstrated to generate and propagate highly confined terahertz (THz) surface plasmonic waves under end-fire excitation. The transverse modal power distribution and spectral properties of the bound THz plasmonic wave are characterized in two metallic rod arrays with different periods and in two configurations with and without attaching a subwavelength superstrate. The integrated metallic rod array–based waveguide can be used to sense the various thin films deposited on the polypropylene superstrate based on the phase-sensitive mechanism. The sensor exhibits different phase detection sensitivities depending on the modal power immersed in the air gaps between the metallic rods. Deep-subwavelength SiO₂ and ZnO nanofilms with an optical path difference of 252 nm, which is equivalent to λ/3968 at 0.300 THz, are used as analytes to test the integrated plasmonic waveguide. Analysis of the refractive index and thickness of molecular membranes indicates that the metallic rod array–based THz waveguide can integrate various biochip platforms for minute molecular detection, which is extremely less than the coherent length of THz waves.

© 2014 Optical Society of America