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Abstract

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract. Recently published studies suggest that terahertz pulsed imaging will have applications in medicine and biology, but there is currently very little information about the optical properties of human tissue at terahertz frequencies. Such information would be useful for predicting the feasibility of proposed applications, optimising acquisition protocols, providing information about variability of healthy tissue and supplying data for studies of the interaction mechanisms. Research ethics committee approval was obtained, and measurements made from samples of freshly excised human tissue, using a broadband terahertz pulsed imaging system comprising frequencies approximately 0.5 to 2.5 THz. Refractive index and linear absorption coefficient were found. Reproducibility was determined using blood from one volunteer, which was drawn and measured on consecutive days. Skin, adipose tissue, striated muscle, vein and nerve were measured (to date, from one individual). Water had a higher refractive index (2.04 ± 0.07) than any tissue. The linear absorption coefficient was higher for muscle than adipose tissue, as expected from the higher hydration of muscle. As these samples came from a single subject, there is currently insufficient statistical power to draw firm conclusions, but results suggest that in vivo clinical imaging will be feasible in certain applications.

Tutorial: Terahertz beamforming, from concepts to realizations

“…26 This is useful because many molecules in biology and chemistry are chiral and respond differently to left-and right-hand circularly polarized terahertz waves. [27][28][29] Terahertz-range imaging applications 30 such as safe, subdermal medical imaging, [31][32][33] security screening, 34 and non-destructive imaging of priceless artifacts and art 35,36 are envisaged, as terahertz waves are non-ionising, and can penetrate to a modest depth in soft tissues 37 and clothing. 38 Such non-contact imaging applications typically rely on some form of beam control-either fine beamfocusing 30,39 or Bessel beams, 40 to provide adequate resolution.…”

Biological Sensing with Terahertz Circular Dichroism Spectroscopy

“…A reference pyroelectric detector is employed to monitor the fluctuations in incident laser power. A precision variable path length cell 1,10 , accurate to ~ 0.5 μm, allows for reproducible control of the sample thickness. The cell windows are made of high density polyethylene, which is highly transparent and has an index of refraction that closely matches that of liquid water over the frequency range of interest 11 .…”

Optical feedback effects on terahertz quantum cascade lasers: modelling and applications

“…[9][10][11] Due to the inherently low penetration depth of THz radiation in hydrated biological tissue, biological and particularly superficial skin imaging are applications to which THz frequency imaging is well suited. [17][18][19][20][21][22][23][24][25][26][27][28][29][30] As such, imaging of superficial skin employing THz QCLs in confocal reflection-mode system geometry is an ideal application for the technique. 31,32 Laser feedback interferometry (LFI) with THz QCLs exploits the interferometric nature of optical feedback in a THz QCL to create a homodyning THz transceiver operating in confocal configuration.…”