Tag Archives: terahertz

Researchers Develop Transparent Flexible Terahertz Sensors With Graphene

The researchers of the Swedish Chalmers University of Technology have developed a new design of terahertz sensor using Graphene. This flexible sensor can be integrated into wearable materials. Most importantly, it can be manufactured very cheaply and also it is practically transparent. This new type of sensor could be a major breakthrough by opening doors of many new applications.

Flexible Graphene sensor by Chalmers University
Flexible Graphene sensor by Chalmers University

The terahertz frequency band ranges from 100 to 10,000 GHz. Terahertz radiation is able to penetrate materials that block visible and mid-infrared light. This technology opened up a range of potential applications in medical diagnostics, process control, and even intelligent vehicles. Jan Stake, the head of the Terahertz and Millimetre Wave Laboratory at Chalmers, said,

Terahertz graphene-based FET detectors have been demonstrated on rigid substrates such as SiO2/Silicon, and flexible devices such as graphene and other concepts have been demonstrated at RF/microwave frequencies.

This band is also used by the so-called “nude-scanners” used at airport check-in desks to look for illegal items carried by passengers. THz waves penetrate normal clothing hence it can detect weapons made of plastic. As Non-metallic weapons cannot be detected by ordinary metal detectors used at the entry gates and by hand-held scanners. Thus these new inexpensive sensors can enhance security for everyone.

Terahertz transmissions have enormous bandwidth available. THz signals can be used as carriers for high-speed information links over short distances allowing data speeds up to 100 Gb/s. On the other hand, THz waves allow uninterrupted visibility in fog or rain for motorized vehicles.

There are many medical applications of the technology using sensors that are cheap to produce and are physically small. One important example is in the field of dermatology. Skin regions affected by cancer have a different reflective index to THz waves which makes the sensor a useful diagnostic tool.

Although being under development for a long time, conventional THz sensors were always large and expensive. With this new design, the Swedish research team has enabled the tech world with mass production of the sensors. New sensors will be small, flexible and cost-effective. Development of the sensors was funded by the European Union under the Graphene Flagship Initiative.

What the Chalmers team has done to combine flexibility and terahertz detection could also make it possible to build an Internet of Things connected via high-bandwidth 5G technologies.

Terahertz Electronics – Way To Bridge The largely-untapped Region Between 100GHz and 10THz

The terahertz (THz) region, which is based on 1THz frequency, separates electronics from photonics and has been difficult to access for ages. Semiconductor electronics cannot handle frequencies equal to or greater than 100GHz due to various transport-time related limitations. In other hand, photonics devices fail to work below 10THz as photon’s energy significantly drops to thermal energy. Terahertz Electronics (TE) is a new technology that extends the range of electronics into the THz-frequency region.

The Terahertz Gap
The Terahertz Gap

The main goal of Terahertz Electronics is to build a bridge between low-frequency “Electronics” and high-frequency “Photonics”. Since these devices use photon-electron particle interactions, as photon energy “hv” decreases below thermal energy “kT”, the device ceases to operate efficiently unless it is cooled down. At the low-frequency end, electronics cannot operate above 100GHz as transport time is dependent on drift and diffusion speeds of electrons/holes. As a result, a large region between 100GHz and 10THz remained inaccessible. Terahertz Electronics solves this problem efficiently by cleverly incorporating electronics with photonics.

Terahertz electronics technology offers practical applications in high-speed data transfer, THz imaging, and highly-integrated radar and communication systems. Surprisingly enough, It does not use semiconductors. Instead, it is based on metal-insulator tunneling structures to form diodes for detectors and ultra-high-speed transistors for oscillator based transmitters.

One drawback of the Terahertz Electronics is, it requires high-frequency radiation sources. Lack of a small, low-cost, moderate-power THz source is one of the main reasons that THz applications have not fully materialized yet. Scientists are trying to find a solution to this problem. They created a compact device that can lead to portable, battery-operated sources of THz radiation. This new solid-state T-ray source uses high-temperature superconducting crystals that contain stacks of Josephson junctions. So, even a small voltage, around two millivolts per junction, can induce frequencies in the THz range.

Mercury arc lamps generate light in terahertz
Mercury arc lamps generate light in terahertz

TE devices are extremely fast and they are made entirely of thin-film materials—metals and insulator. Hence, it is possible to fabricate Terahertz Electronics devices on top of complementary metal oxide semiconductor (CMOS) circuitry—a technology for creating integrated-circuits circuitry or on an extensive variety of substrate materials. In TE devices, charge transport through the junction occurs via electron tunneling. Further research and development will make Terahertz Electronics a reality in not-so-distant future.