Terahertz radiation, which lies between microwaves and infrared light in the electromagnetic spectrum, has long been hailed as the next frontier for technological innovation. Terahertz frequencies hold great promise for applications ranging from security scanning to biomedical imaging. However, developing practical terahertz devices has proven technically challenging. Recent advances are now starting to unlock the potential of terahertz technologies.
What is Terahertz Radiation?
Terahertz radiation occupies the region of the electromagnetic spectrum with frequencies between 0.1 and 10 terahertz (THz), corresponding to wavelengths between 3mm and 30 micrometers. This “terahertz gap” sits between the well-established technologies of microwaves and infrared light. Terahertz frequencies exhibit properties of both electromagnetic waves and photons, making them suitable for both wireless communication and optical imaging applications.
Terahertz Technologies radiation was first discovered in the 1960s but remained largely unexplored until the 1990s when new sources and detectors started to become available. Early experiments demonstrated terahertz’s potential for trace gas detection, chemical spectroscopy, and biomedical imaging. However, obstacles like a lack of efficient terahertz sources hindered further progress for many years.
Advances in Terahertz Sources and Detectors
A major breakthrough came in the late 2000s with the development of photoconductive antennas which can efficiently generate and detect pulsed terahertz radiation using femtosecond lasers. By sampling beams of ultrafast laser pulses, these “antenna arrays” enabled entirely new classes of terahertz time-domain spectroscopy and imaging systems.
Continuous wave terahertz sources then advanced rapidly based on oscillators using semiconductors like gallium arsenide and indium gallium arsenide. Techniques like optical rectification of ultrashort laser pulses in nonlinear crystals and electron tunneling effects in semiconductor structures can now produce coherent continuous terahertz waves up to several THz.
On the detection side, advances in materials like low-temperature gallium-doped germanium have drastically lowered noise levels. Cryogenic bolometers can now detect single terahertz photons. Combined with terahertz cameras utilizing focal plane arrays of microbolometer detectors, this has enabled real-time terahertz imaging.
Security and Non-Destructive Testing
One highly visible application is security scanning of objects like mail, packages, and luggage for concealed explosives, drugs, or contraband. Terahertz pulses can penetrate many non-metallic and non-polar barrier materials like clothing, paper, cardboard, wood, ceramics and plastics. Reflections reveal the contents inside without being ionizing like X-rays.
Terahertz techniques are also used for non-destructive evaluation of industrial components. Pulsed terahertz imaging can detect defects, inclusions, or delamination in materials like composites, plastics, and pharmaceutical tablets which are transparent to terahertz radiation. Applications include quality control of aircraft parts, detection of fatigue cracks in metals, identification of counterfeit medications, and inspection of artwork for restoration. Systems incorporating industrial robotics have moved terahertz into manufacturing facilities.
Biomedical Imaging and Spectroscopy
Perhaps the most promising and rapidly developing application is in biomedical sciences. Terahertz frequencies are well suited for clinical imaging since biological tissues have a low absorption. At the same time, the interactions of terahertz radiation with molecular vibrations provides a “fingerprint” spectrum for identification of biomolecules, pathogens and tissues.
Terahertz imaging has been explored for breast cancer detection by utilizing the water content contrast between malignant and healthy tissues. Meanwhile, terahertz spectroscopy has identified disease biomarkers and studied the molecular structure of tissues, opening new insights into pathological conditions. Other areas of research include detection of skin cancer, arthritis, burns, and analysis of ex vivo samples for histopathology. Portable terahertz devices could transform medical diagnostics by providing non-invasive, spectroscopic techniques without the cost or radiation risks of X-rays or MRI.
Regulatory and Standardization Challenges
Widespread commercialization of terahertz technologies still faces some key hurdles. Lack of standardization has hindered development of interoperable systems and precluded many consumer applications. Health and safety regulations have not yet been established for devices emitting continuous terahertz fields at high powers. However, research suggests terahertz poses minimal risk to human tissues at levels used today for imaging and spectroscopy.
The Future of Terahertz
Recent progress indicates the future potential of terahertz applications is vast. With advancements in terahertz components like sources, detectors, antennas and optical elements, systems for spectroscopy, imaging and spectroscopy are becoming more compact, affordable, and practical. New concepts are exploring wireless data transmission, security scanners integrated into smartphones, and portable molecular sensors for rapid disease diagnostics.
The commercial potential spans medical devices, process monitoring, quality control and nondestructive testing across multiple industries. Integration with 5G networks could enable new wireless sensing capabilities. With ongoing improvements resolving the technical and regulatory challenges, terahertz technologies may soon transform sectors from healthcare to communications to manufacturing. The “terahertz gap” is primed to become a hub of innovation over the coming decades.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it