Abstract-Non-invasive, near-field terahertz imaging of hidden objects using a single pixel detector

R. I. Stantchev, B. Sun, S. M. Hornett, P. A. Hobson, G. M. Gibson, M. J. Padgett, E. Hendry

http://arxiv.org/abs/1509.03138#

Terahertz (THz) imaging has the ability to see through otherwise opaque materials. However, due to the long wavelengths of THz radiation ({\lambda}=300{\mu}m at 1THz), far-field THz imaging techniques are heavily outperformed by optical imaging in regards to the obtained resolution. In this work we demonstrate near-field THz imaging with a single-pixel detector. We project a time-varying optical mask onto a silicon wafer which is used to spatially modulate a pulse of THz radiation. The far-field transmission corresponding to each mask is recorded by a single element detector and this data is used to reconstruct the image of an object placed on the far side of the silicon wafer. We demonstrate a proof of principal application where we image a printed circuit board on the underside of a 115{\mu}m thick silicon wafer with ~100{\mu}m ({\lambda}/4) resolution. With subwavelength resolution and the inherent sensitivity to local conductivity provided by the THz probe frequencies, we show that it is possible to detect fissures in the circuitry wiring of a few microns in size. Imaging systems of this type could have other uses where non-invasive measurement or imaging of concealed structures with high resolution is necessary, such as in semiconductor manufacturing or in bio-imaging.

CHTM research in compressive sensing reported in Nature Photonics

Potential applications in medical and security imaging
By Karen Wentworth 
http://news.unm.edu/news/chtm-research-in-compressive-sensing-reported-in-nature-photonics

Center for High Technology Materials at the University of New Mexico.

In a collaborative effort, researchers at the University of New Mexico have broken new ground in Terahertz imaging through the development of a new metamaterial which allows manipulation of light in the Terahertz region of the electromagnetic spectrum and enables compressive sensing similar to what is possibly being undertaken in the human eye.

Metamaterials are engineered materials that have special properties that are not found in nature. It uses shapes and orientation to manipulate light waves. The metamaterial was grown and fabricated at the Center for High Technology Materials says director Sanjay Krishna.

Sanjay Krishna, CHTM director

Krishna’s research group, including his graduate student John Montoya, along with researchers from the Department of Physics, Boston College, and the Center for Metamaterials and Integrated Plasmonics, Department of Electrical and Computer Engineering, Duke University, has developed a spatial light modulator whose reflection can be changed by using an applied voltage. The structure can interact with the light waves in new ways, which have longer wavelengths than visible light. The compressed images displayed with a single-pixel detector paves the way for novel research in THz imaging.

This research fills a gap in long-wavelength imaging because it supplies a material that functions to concentrate images within a narrow band. It has implications for applications that can range from security screening, to all weather to skin cancer detection.