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