Abstract-Total Internal Reflection Geometry: Exploiting Total Internal Reflection Geometry for Terahertz Devices and Enhanced Sample Characterization

Qiushuo Sun, Xuequan Chen, Xudong Liu, Rayko I. Stantchev, Emma Pickwell‐MacPherson

https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201900535

To promote potential applications of terahertz (THz) technology, more advanced functional THz devices with high performance are needed, including modulators, polarizers, lenses, wave retarders, and antireflection coatings. This work summarizes recent progress in THz components built on functional materials including graphene, vanadium dioxide, and metamaterials. The key message is that, while the choice of materials used in such devices is important, the geometry in which they are employed also has a significant effect on the performance achieved. In particular, devices operating in total internal reflection geometry are reviewed, and it is explained how this geometry is able to be exploited to achieve a variety of THz devices with broadband operation.

Abstract-Exploiting Total Internal Reflection Geometry for Terahertz Devices and Enhanced Sample Characterization

Qiushuo Sun, Xuequan Chen, Xudong Liu, Rayko I. Stantchev 

https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201900535

To promote potential applications of terahertz (THz) technology, more advanced functional THz devices with high performance are needed, including modulators, polarizers, lenses, wave retarders, and antireflection coatings. This work summarizes recent progress in THz components built on functional materials including graphene, vanadium dioxide, and metamaterials. The key message is that, while the choice of materials used in such devices is important, the geometry in which they are employed also has a significant effect on the performance achieved. In particular, devices operating in total internal reflection geometry are reviewed, and it is explained how this geometry is able to be exploited to achieve a variety of THz devices with broadband operation.

Abstract-Design and fabrication of 3-D printed conductive polymer structures for THz polarization control

A. I. Hernandez-Serrano, Qiushuo Sun, Elizabeth G. Bishop, Elliott R. Griffiths, Christopher P. Purssell, Simon J. Leigh, J. Lloyd-Hughes, and Emma Pickwell-MacPherson

Fig. 1 (a) Diagram of the proposed polarizer; (b) Photograph of the printed devices; (c) and (d) show the refractive index and absorption coefficient of CPLA, respectively.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-8-11635

In this paper, we numerically and experimentally demonstrate the inverse polarization effect in three-dimensional (3-D) printed polarizers for the frequency range of 0.5 - 2.7 THz. The polarizers simply consist of 3-D printed strip lines of conductive polylactic acid (CPLA, Proto-Pasta) and do not require a substrate or any further metallic deposition. The experimental and numerical results show that the proposed structure acts as a broadband polarizer between the range of 0.3 THz to 2.7 THz, in which the inverse polarization effect is clearly seen for frequencies above 0.5 THz. In the inverse polarization effect, the transmission of the transverse electric (TE) component exceeds that of the TM component, in contrast to the behavior of a typical wire-grid polarizer. We show how the performance of the polarizers depends on the spacing and thickness of the CPLA structure; extinction ratios higher than 20 dB are achieved. This is the first report using CPLA to fabricate THz polarizers, demonstrating the potential of using conductive polymers to design THz components efficiently and robustly.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-THz in vivo measurements: the effects of pressure on skin reflectivity

Jiarui Wang, Rayko I. Stantchev, Qiushuo Sun, Tor-Wo Chiu, Anil T. Ahuja, and Emma Pickwell MacPherson

Fig. 1 Experimental setup and stratified media model illustration. (a) The THz beam is focused onto the top interface of the quartz window, and the reflected signal is collected and then detected by a photoconductive antenna. (b) Schematic illustration of the layers within human skin: each layer has a different permittivity. The hydration profile of skin is approximately linear in the SC and epidermis, and constant in the dermis.

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-9-12-6467

Terahertz (THz) light is non-ionizing and highly sensitive to subtle changes in water concentration which can be indicative of disease. The short THz penetration depth in bio-samples restricts in vivo measurements to be in a reflection geometry and the sample is often placed onto an imaging window. Upon contacting the imaging window, occlusion and compression of the skin affect the THz response. If not appropriately controlled, this could cause misleading results. In this work, we investigate and quantify how the applied pressure affects the THz response of skin and employ a stratified model to help understand the mechanisms at play. This work will enable future THz studies to have a more rigorous experimental protocol, which in turn will facilitate research in various potential biomedical applications under investigation.

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