Harnessing the Magnetic Nature of Light for Terahertz-driven Devices

https://incompliancemag.com/harnessing-the-magnetic-nature-of-light-for-terahertz-driven-devices/

BY LAUREN SACCONE

Scientists from The University of New South Wales Sydney and The University of Sydney have demonstrated a new way to enhance magnetic responses in a dipole emitter by a sub-wavelength fiver. This research, and additional studies on dielectric sub-wavelength particles have provided scientists with a new platform with which to work on magnetic light.

Researchers experimentally demonstrated an enhanced magnetic dipole source in the terahertz frequency range. The fiber is placed next to a hole in a metal screen, which enhances the radiation power more than one order of magnitude. This is due to the excitation of the Mie-type resonances found in the aforementioned fiber. The scientists when on to demonstrate that the system was roughly equivalent to a double-fiber system when excited by a magnetic source.

The optical fiber system is coupled with magnetic dipole. When combined, it can be construed as a unit cell of metasurfaces. The metasurfaces can then be used for the manipulation of terahertz radiation. This also provides proof-of-concept regarding the possibility to achieve enhanced radiation of a dipole source, once it it in proximity of a sub-wavelength fiber. Additionally, the unit cell can be easily scaled down to optical frequencies. This could provide a huge boon to scientists working on developing integrated nanophotonic devices including nanoantennas and lasers on fiber.

Further research proved that the aperture-fiber system created by the scientists was equivalent to that of an MD-double fiber system. This also confirmed the theory that the experimentally measured enhancement ratio was a fair approximation of the THz Purcell enhancement of an MD source in the vicinity of subwavelength fibers. Scientist were able to approximate field uniformity in the aperture as well as the representation of the aperture as an MD source.

Enhancing the forward emission relies on two distinct factors. These are the loss of the fiber material, as well as refractive index. A lower material loss and higher refractive index could also be used to enhance the emission further. Because of this, the ideal material in the experiments would be silicon. Silicon has lower losses and a high refractive index, especially when compared to the soft glass used in the scientist’s work. Unfortunately, the diameter required for such an enhancement has proven extremely difficult to achieve so far — a problem researchers continue to struggle with.

Despite some setbacks, scientists are optimistic about the future applications of their discoveries. Nanotechnologies in particular will significantly benefit from these advancements.

The future of wireless communications is terahertz

Electrical and optical engineers in Australia have designed a novel platform that could tailor telecommunication and optical transmissions. They experimentally demonstrated their system using a new transmission wavelength with a higher bandwidth capacity than those currently used in wireless communication. Reported this week in APL Photonics, these experiments open up new horizons in communication and photonics technology. Here, a schematic of the problem: Aperture in a metallic screen with a dielectric fiber placed on top acting as a magnetic dipole emitter when excited by a wave incident on the aperture. Credit: Andrey E. Miroshnichenko

 https://phys.org/news/2018-02-future-wireless-terahertz.html#jCp

Electrical and optical engineers in Australia have designed a novel platform that could tailor telecommunication and optical transmissions. Collaborating scientists from the University of New South Wales in Sydney and Canberra, the University of Adelaide, the University of South Australia and the Australian National University experimentally demonstrated their system using a new transmission wavelength with a higher bandwidth capacity than those currently used in wireless communication. Reported this week in APL Photonics, these experiments open up new horizons in communication and photonics technology.

Optical fibers are the frontrunners in fast data transmission, with data encoded as microwave radiation. Microwave radiation is a type of electromagnetic radiation with longer wavelengths, and therefore lower frequencies, than visible light. Current microwave wireless networks operate at a low gigahertz frequency bandwidth. In our current digital age that demands speedy transmission of large amounts of data, the limitations of microwave bandwidths become more increasingly more apparent.

In this study, scientists examined terahertz radiation, which has shorter wavelengths than microwaves and therefore has higher bandwidth capacity for data transmission. Furthermore, terahertz radiation provides a more focused signal that could improve the efficiency of communication stations and reduce power consumption of mobile towers. "I think moving into terahertz frequencies will be the future of wireless communications," said Shaghik Atakaramians, an author on the paper. However, scientists have been unable to develop a terahertz magnetic source, a necessary step to harness the magnetic nature of light for terahertz devices.

The researchers investigated how the pattern of terahertz waves changes on interaction with an object. In previous work, Atakaramians and collaborators proposed that a magnetic terahertz source could theoretically be produced when a point source is directed through a subwavelength fiber, a fiber with a smaller diameter than the radiation wavelength. In this study, they experimentally demonstrated their concept using a simple setup—directing terahertz radiation through a narrow hole adjacent to a fiber of a subwavelength diameter. The fiber was made of a glass material that supports a circulating electric field, which is crucial for magnetic induction and enhancement in terahertz radiation.

"Creating terahertz magnetic sources opens up new directions for us," Atakaramians said. Terahertz magnetic sources could help the development of micro- and nanodevices. For example, terahertz security screenings at airports could reveal hidden items and explosive materials as effectively as X-rays, but without the dangers of X-ray ionization.

Another advantage of the source-fiber platform, in this case using a magnetic terahertz source, is the proven ability to alter the enhancement of the terahertz transmissions by tweaking the system. "We could define the type of response we were getting from the system by changing the relative orientation of the source and fiber," Atakaramians said.

Atakaramians emphasized that this ability to selectively enhance radiation isn't limited to terahertz wavelengths. "The conceptual significance here is applicable to the entire electromagnetic spectrum and atomic radiation sources," said Shahraam Afshar, the research director. This opens up new doors of development in a wide range of nanotechnologies and quantum technologies such as quantum signal processing.

Remote Antarctic telescope reveals gas cloud where stars are born

A UNSW-led team has used a telescope in Antarctica to identify a giant gas cloud in our galaxy which appears to be in an early stage of formation. Image is of the PLATO-R observatory at Ridge A. The HEAT telescope is the black object on stilts at left, the instrument module is the yellow box and the solar panel array is on the right. Credit: Geoff Sims

 http://phys.org/news/2014-02-remote-antarctic-telescope-reveals-gas.html#jCp

Using a telescope installed at the driest place on earth - Ridge A in Antarctica – a UNSW-led team of researchers has identified a giant gas cloud which appears to be in an early stage of formation.

Giant clouds of molecular gas – the most massive objects in our galaxy – are the birthplaces of stars.

"This newly discovered gas cloud is shaped like a very long filament, about 200 light years in extent and ten light years across, with a mass about 50,000 times that of our sun," says team leader, Professor Michael Burton, an astronomer at UNSW Australia.

"The evidence suggests it is in the early stages of formation, before any stars have turned on."

The results are published in The Astrophysical Journal.

The team is using the High Elevation Antarctic Terahertz telescope, or HEAT, at Ridge A, along with the Mopra telescope at Coonabarabran in NSW, to map the location of gas clouds in our galaxy from the carbon they contain.

At 4000 metres elevation, Ridge A is one of the coldest places on the planet, and the driest. The lack of water vapour in the atmosphere there allows terahertz radiation from space to reach the ground and be detected.

The PLATO-R robotic observatory with the HEAT telescope was installed in 2012 by a team led by UNSW physicist, Professor Michael Ashley, and Dr Craig Kulesa of the University of Arizona.

A UNSW-led team has used a telescope in Antarctica to identify a giant gas cloud in our galaxy which appears to be in an early stage of formation. Image is of the HEAT telescope at Ridge A. Credit: Geoff Sims

"We now have an autonomous telescope observing our galaxy from the middle of Antarctica and getting data, which is a stunning new way of doing science. Ridge A is more than 900 kilometres from the nearest people, who are at the South Pole, and is completely unattended for most of the year," says Professor Burton.

The HEAT telescope detects atomic carbon and the Mopra telescope detects carbon monoxide. "I call it following the galactic carbon trail," says Professor Burton.

The discovery of the new galactic cloud, which is about 15,000 light years from earth, will help determine how these mysterious objects develop in the interstellar medium.

One theory is that they are formed from the gravitational collapse of an ensemble of small clouds into a larger one. Another involves the random collision of small clouds that then agglomerate. Or it may be that the molecular gas filament is condensing out of a very large, surrounding cloud of atomic gas.

About one star per year, on average, is formed in the Milky Way. Stars that explode and die then replenish the gas clouds as well as moving the gas about and mixing it up