Terahertz Emission
- 1. Kutluhan Utku TUMEN 2018 / 2019 TERAHERTZ EMISSION
- 2. 1- History of Terahertz 2- Introduction about Terahertz Emission 3- Properties of Terahertz 4- Terahertz Generation and Detection 5- Applications of Terahertz K.U.TUMEN 2018/2019 1 Outline
- 3. K.U.TUMEN 2018/2019 2 History of Terahertz •It has been several decades since electromagnetic radiation in the THz band was first scientifically studied. •In the beginning, such radiation was called far-infrared waves or millimeter/submillimeter waves. •It was through the development of ultrafast optoelectronics, which led to the successful generation and detection of THz pulses in the middle 1980s, that interest in this particular electromagnetic wave widely emerged. •Early researchers were focused on developing technologies in generating, detecting, and manipulating THz waves. •Lately, interest has become more focused on the real-world application of THz waves. https://en.wikipedia.org/wiki/Terahertz_radiation
- 4. K.U.TUMEN 2018/2019 3 Introduction about Terahertz Various frequencies are spaced along the frequently used electromagnetic spectrum. • Microwaves • Infrared Radiations • Visible Lights • Ultraviolet • X-Rays Between the microwave and infrared frequencies lies terahertz (THz) radiation. https://en.wikipedia.org/wiki/Terahertz_radiation
- 5. K.U.TUMEN 2018/2019 4 Introduction about Terahertz •Terahertz radiation is also known as submillimeter radiation. •Terahertz waves, tremendously high frequency (THF), T-rays, T-waves, T-light, T-lux or Thz is consists of electromagnetic waves within the designated band of frequencies from 0.3 to 30 terahertz. •Wavelengths (𝞴) of radiation in the terahertz band correspondingly range from 1 mm to 0.1 mm. •If we take generally Radiation at 1 THz has; i. Period of 1 ps, ii. Wave number (hv) of 33 cm¯¹, iii. Photon Energy of 4.1 meV, iv. Equivalent Temperature (T) of 47.6 K . https://en.wikipedia.org/wiki/Terahertz_radiation
- 6. K.U.TUMEN 2018/2019 5 Introduction about Terahertz •1 THz : 10¹² Hz https://en.wikipedia.org/wiki/Terahertz_radiation
- 7. Interactions of Terahertz waves with matter : • Rotation of molecules • Bond vibrations • Stretching and torsion • Phonons • Free carrier acceleration K.U.TUMEN 2018/2019 6 Introduction about Terahertz https://en.wikipedia.org/wiki/Terahertz_radiation
- 8. K.U.TUMEN 2018/2019 7 Properties of Terahertz •Terahertz radiation travels in a line of sight. •It is non-ionizing. •Like microwave radiation, terahertz radiation can penetrate a wide variety of non-conducting materials. •Terahertz radiation can pass through I. Clothing II. Paper, III. Cardboard, IV. Wood, V. Plastic and ceramics. •Terahertz radiation has limited penetration through fog and clouds and can not penetrate liquid water or metal. •Due to extreme water absorption, THz waves cannot penetrate into the human body like microwaves can. Therefore, even if THz waves do cause any harm, it is limited to skin level. https://en.wikipedia.org/wiki/Terahertz_radiation
- 9. K.U.TUMEN 2018/2019 8 Properties of Terahertz •The penetration depth is typically less than that of microwave radiation. •THz is not ionizing yet can penetrate some distance through body tissue, so it is of interest as a replacement for medical X-rays. •However, due to their specific location on the electromagnetic spectrum, THz waves are much more difficult to handle than waves adjacent to them. •THz waves have low photon energies and thus can not lead to photo-ionization in biological tissues as can X-rays. •As a result, THz waves are considered safe for both the samples and the operator. •The earth's atmosphere is a strong absorber of terahertz radiation, so the range of terahertz radiation in air is limited to tens of meters, making it unsuitable for long-distance communications. https://en.wikipedia.org/wiki/Terahertz_radiation
- 10. K.U.TUMEN 2018/2019 9 Terahertz Sources •There generation and detection is still not as good as it should have. •We can not measure terahertz via electronic counters. Generation and detection become impossible by conventional electronic devices. So we require new devices and techniques. •Tera-Hertz Sources are divided into two sources : 1 - Natural : Naturally terahertz frequencies are emitted by black bodies with above 2K Temperature. We measure these frequencies from objects like cold matter, dust particle and distant starburst galaxies. 2- Artificial : Gyrotron Oscillator, Backward wave oscillator Organic gas far infrared laser, Free electron laser (FEL) Schottky diode multipliers, Quantum cascade laser https://en.wikipedia.org/wiki/Terahertz_radiation
- 11. K.U.TUMEN 2018/2019 10 Terahertz Generation&Detection •We detect tera hertz pulses by two methods. 1)Photoconductive Antennas Operation principle of photoconductive antennas is the laser beam is focused on the dipole gap which generating electron-hole pairs, and the transient current conditioned by the applied voltage emits an electromagnetic pulse of sub picosecond duration into the free space. (the THz pulse) The emitted wavelengths are much longer compared to the size of their source, the dipole; hence, they diffract strongly in the form of a wide cone filling out almost the whole solid angle behind the antenna (dark grey area marked THz). http://entsphere.com/pub/pdf/%5BYun-Shik_Lee%5D_Principles_of_Terahertz_Science_and(BookFi.org).pdf
- 12. K.U.TUMEN 2018/2019 11 •We detect terahertz pulses by two methods. 2)Electro-Optic Sampling The laser pulses of some tens of femtoseconds width pass through the scanning delay enabling a time-resolved acquisition of the electric field of the THz pulse over multiple shots. The analyzer consists of a retarder and a Wollaston beam splitter. The photodetectors acquire the modulated intensities of the laser pulses depending on the phase retardation. Terahertz Generation&Detection http://entsphere.com/pub/pdf/%5BYun-Shik_Lee%5D_Principles_of_Terahertz_Science_and(BookFi.org).pdf
- 13. K.U.TUMEN 2018/2019 12 Terahertz Applications •X-rays can see shapes within the human body so Terahertz waves (also called as T-rays) can create pictures and transmit information. •With T-rays that do not harm biological tissues, it will be possible for the passengers to be screened without leaving their belongings. https://www.slideshare.net/lodro-ahmed/tera-hertz-electromagnetic-waves?from_action=save
- 14. K.U.TUMEN 2018/2019 13 •It has also been shown that it is possible to detect landmines at a distance of up to 30 m using T-ray reflection spectroscopy. https://www.slideshare.net/lodro-ahmed/tera-hertz-electromagnetic-waves?from_action=save
- 15. K.U.TUMEN 2018/2019 14 •The THz Band can also enable ultra-broadband secure communication links in the military and defense fields. https://en.wikipedia.org/wiki/Terahertz_radiation
- 16. • 5G Cellular Networks • Terabit Wireless Local Area Networks (T-WLAN) • Terabit Wireless Personal Area Networks (T-WPAN) • Secure Terabit Wireless Communication • Health Monitoring Systems • Nuclear, Biological and Chemical Defenses • The Internet of Nano-things • Ultra-high-speed On-chip Communication K.U.TUMEN 2018/2019 16 Also another axamples are; https://en.wikipedia.org/wiki/Terahertz_radiation Macroscale Nanoscale
- 17. THANK YOU FOR PARTICIPATING AND LISTENING K.U.TUMEN 2018/2019