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Unexplored light: THz Waves with Excellent Transparency Has Great Potential for Use in Applications

Terahertz radiation, which is commonly defined as the region of the electromagnetic spectrum between radio and optical frequencies (0.3 THz and to 10 THz), is extremely attractive for a variety of applications in science and technology such as sensing, imaging, and telecommunication. THz waves, are categorized as far infrared light, which is also referred to as sub-millimeter waves in the field of telecommunication. The frequency of 1 THz corresponds to the wavelength of 300 µm. As the frequency increases, it begins to enter the infrared region. THz waves, although similar to the microwaves used to detect guns and knives at airport security checks, has superior characteristics of propagation. THz waves, which yields high-resolution images due to its short wavelength compared to the microwaves and is even capable of imaging the water content in objects, may be applied to non-destructive inspection. Contrary to the X-rays, inspection using THz radiation does not require special considerations. THz waves may also be used to identify chemical substances due to the fact that the characteristic absorption spectrum of substances, known as the “fingerprint spectrum” is located in the THz frequency- region, for example, identification of chemical substances such as aspirin, stimulants or drugs in an envelope - without opening.
Dr. Okada is engaged in the field of the THz spectroscopies. “I have been intrigued by light since I was small. This motivated me to research optical properties as I entered the University.” He reminisces, “Under my mentor, Professor Tadashi Ito (currently an professor emeritus at the Institute for NanoScience Design, Osaka University), I devoted into the study of interactions between light and electrons, magnetic spins in materials, which is very complex and interesting phenomena.” Later he encountered the spectroscopy using THz waves at Kyoto University and embarked upon a journey in research of potential uses of this “unexplored electromagnetic waves.” Although THz radiation is discovered before in itself, it has just begun to be used for the optical studies in recent years, and we are still in an uncharted territory.

The frequency of 1 THz corresponds to the wavelength of 300 µm. THz waves are suitable for non-contact or non-destructive inspections. It is possible to identify chemical substances inside an envelope using their unique fingerprint spectrum.

THz electromagnetic wave