Low-cost Terahertz emitters developed at NUS could accelerate development of futuristic screening devices

Associate Professor Yang Hyunsoo (Right) and Dr Wu Yang (left) from the NUS Faculty of Engineering and NUS Nanoscience and Nanotechnology Institute

According to a press release from the National University of Singapore (NUS), a research team from the Department of Electrical and Computer Engineering at the NUS Faculty of Engineering and NUS Nanoscience and Nanotechnology Institute has achieved a breakthrough in Terahertz (THz) technology, which could transform security screening and medical imaging. The research was conducted in collaboration with researchers from the Institute of Materials Research and Engineering under Singapore’s Agency for Science, Technology and Research, and Tongji University in China. Findings of the study were published in the scientific journal, Advanced Materials, on 25 January 2017.

THz waves occupy the space between microwaves and infrared light waves in the electromagnetic spectrum, with a designated frequency range of 300 GHz to 3 THz and wavelength ranging from 1 mm to 100 μm. They can pass through non-conducting materials such as clothes, paper, wood and brick  and they are non-ionising (the photons don’t carry enough energy to completely remove an electron from an atom or molecule, making them safe for imaging the human body) and non-destructive. Applications have been explored in areas such as cancer diagnosis, detection of chemicals, drugs and explosives, coating analysis and quality control of integrated circuit chips.

But building compact yet powerful enough THz sources has proven to be challenging. Current THz sources are large, multi-component systems and are heavy and expensive. They are difficult to transport, operate, and maintain. In this context, the work done by the research team addresses a critical challenge for industrial application of THz technology.

The team, led by Associate Professor Yang Hyunsoo and Dr. Wu Yang, has successfully developed flexible, high performance and low-power driven THz emitters that could be mass-produced at low cost. Dr. Wu said, “Traditional methods of generating THz waves, such as through the exciting of electro-optical crystals or photoconductive antennas, often require expensive and bulky high power lasers or extremely expensive and sophisticated device fabrication processes. Our team’s THz emitters have displayed better performance compared to existing devices in many aspects. At the same time, we have also developed a fabrication process to produce these novel THz emitters in large quantities at a low cost.”

The novel radiation sources emit broadband THz waves with a higher power output than a standard 500-micrometre thick rigid electro-optical crystal emitter. The emitters can be powered by a low-power laser, substantially lowering the operating cost.

The research team also devised a low-cost fabrication technique to produce the emitters, involving the deposition of  a large wafer-scale film and subsequent dicing to produce a large quantity of ready-to-use devices. The method is commercially scalable. The performance of the device was not compromised on flexible surfaces, despite being subjected to a large bending curvature. This would mean that it can be incorporated into wearable devices.

The press release lists a series of applications which could be enabled by this breakthrough: portable handheld sensors for detecting explosives, wearable sensors for detecting chemical agents, compact devices for fast and accurate identification of defects in computing chips as well as advanced, non-invasive imaging techniques that could detect tiny tumours.

Moving ahead, the team plans to build a compact spectroscopy system using THz technology based on its advanced THz emitters. The researchers are also looking into enhancing THz emission for specific wavelengths. A patent has been filed for the invention. The research team hopes to work with industry partners to explore various applications of the technology.

Read the press release here

Featured image: NUS

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