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Showing posts with label Electronics. Show all posts
Showing posts with label Electronics. Show all posts

Friday, 13 December 2019

Liquid crystal microlenses capture 4D images

The polarization of light brings a new world of information.

4D images

While most images captured by a camera lens are still flat and two-dimensional, more and more 3D imaging technologies are providing the crucial depth context for medical and scientific applications.

An additional step is in 4D images, whose additional dimension refers to information about light polarization.

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This may open even more application possibilities, but the first prototypes of this technology, such as a 4D microscope , consist of bulky, expensive and complicated equipment.

Now researchers at Nanjing University in China have developed liquid crystal microlenses that can reveal 4D information in a single photographic shot.

The microlenses do not have to be "fabricated" - they assemble themselves thanks to the liquid crystal.

Polarized light

Polarized light contains waves that oscillate in a single plane, while unpolarized light, such as that of the sun, contains waves that move in all directions. Light can become polarized upon reflection of objects, and detecting such light can reveal information that is not available just by looking at the object - for example, cancer cells may reflect polarized light differently from healthy tissues.

Ling-Ling Ma and his colleagues wanted to develop a portable, inexpensive, easy-to-use microlens to simultaneously capture 3D space information plus polarization producing 4D images.

They succeeded using liquid crystals. With a self-assembly process, they modeled microlens arrays in concentric circles, creating a new type of flat lens .

Microlenses capture light reflected by the object differently depending on the distance from the object (depth) and the direction of polarized light, producing 4D information in a single shot.

Although the resolution still needs to be improved, the technique could be used for medical imaging, telecommunications, screens and monitors, remote sensing and even encryption, the researchers say.


Article: Self-Assembled Asymmetric microlenses for Four-Dimensional Visual Imaging

Authors: Ling-Ling Ma Sai-Bo Wu, Wei Hu, Chao Liu, Peng Chen, Hao Qian, Yandong Wang Lifeng Chi, Yan-qing Lu

Magazine : ACS Nano

DOI: 10.1021 / acsnano.9b07104

Saturday, 23 November 2019

Structured light allows communication with infinite Photonic alphabet

Illustration shows the creation of hybrid interlaced photons combining polarization with a twisted light pattern that carries orbital angular momentum . This structured light allows you to use quantum protocols to create a larger coding alphabet, more security and better noise resistance.

Structured light

The creation of Structured Light beams - light in exotic patterns such as spirals - not only revealed a strange new world of light, but also opened new fields of technological exploration for photonics .

And it seems that these application possibilities have not even been scratched.

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Two South African researchers have already shown that it is possible to exploit helical beams of light to create an alphabet, which promises not only greater security and robustness in communications, but also a new way to explore the physics behind quantum computers. .

"What we really want is to do quantum mechanics with light patterns. By that we mean that light comes in a variety of patterns that can be differentiated - like our faces," explained Andrew Forbes of the University of Witwatersrand.

Since light patterns can be distinguished from each other, they can be used as an alphabet form. "The cool thing is that there is, at least in principle, an infinite set of patterns, so an infinite alphabet is available," said Forbes.

Different patterns of structured light - the "letters" of the infinite photonic alphabet.

Multidimensional States

Traditionally, quantum protocols have been implemented with light bias, which has only two values, which means a maximum photon information capacity of just 1 bit - remembering that one bit per photon is already incredibly better than the floods of light. electrons used today. Using structured light patterns as an alphabet, in turn, the information capacity is much greater, not to mention the gains in safety and noise resistance.

"Light patterns are a path to what we call large states," continues Forbes. "They are large because many standards are involved in the quantum process. Unfortunately, the toolkit for managing these patterns is still underdeveloped and requires a lot of work."

That's why he and his colleague Isaac Nape began working with hybrid states, which combine the traditional use of polarization with structured modes of light.

"It turns out that many protocols can be implemented efficiently with simpler tools, combining polarized patterns for the best of both worlds," said Forbes. "Instead of two pattern dimensions, hybrid states allow access to multidimensional states, for example an infinite set of two-dimensional systems. This seems to be a promising way to truly make a quantum lattice based on light patterns come true."


Article: Quantum mechanics with patterns of light: Progress in high dimensional and multidimensional entanglement with structured light

Authors: Andrew Forbes, Isaac Nape

Magazine: AVS Quantum Science

DOI: 10.1116 / 1.5112027

A strange new world of light

Structured light

Over the past ten years, the physical developed nanostructured materials that can produce light beams completely out of the standard, which exhibit unusual behaviors such as spiral bending , corkscrew shape or that share as a Y .

These so-called structured light beams are not only revealing unknown things about the physics of light, they also have a wide range of practical applications, from super resolution images to microscopes and telescopes, to light-beam molecular manipulation and communications. by light without optical fibers.

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Now researchers have developed a tool that generates new, more complex light states in a completely different and configurable way.

"We have developed a metasurface that is a new tool for studying unpublished aspects of light. This optical component enables much more complex operations and allows researchers to not only explore new states of light but also new applications for structured light," said the professor. Federico Capasso, from Harvard University, USA.

Angular momentum and polarization

The metasurface connects two aspects of light: orbital angular momentum and circular polarization (or angular rotation pulse). In comparison to a planet, orbital momentum describes how the planet orbits the sun and circular polarization describes how the planet rotates about its own axis (rotation).

Light bias could already be used to control the size and shape of these exotic beams, but the connection was limited because only certain polarizations could be converted at certain orbital moments.

The new metamaterial significantly widens this connection. It can be designed so that any input bias can result in any orbital angular momentum output. In other words, any polarization can produce any kind of structured light, from spirals and corkscrews to vortices of any size.

Another great advantage is that the metasurface is multifunctional and can be programmed so that a polarization results in one vortex and a different polarization results in another completely different vortex.

Examples of structured light showing cross sections of beams.


Potential applications of this device include molecular manipulation and optical tweezers, which use light to move molecules and nanoparticles - the orbital momentum of light is strong enough to rotate and move microscopic particles.

Other fields of application include high resolution images, light beams for quantum computing, free space optical communication, and new light states in lasers.


Article: Arbitrary spin-to-orbital angular momentum of light conversion

Authors: Robert C. Devlin, Antonio Ambrosio, Noah A. Rubin, JP Balthasar Mueller, Federico Capasso

Magazine: Science

Vol .: eaao5392

DOI: 10.1126 / science.aao5392

Tuesday, 25 June 2019

Negative capacitor takes power only where it is needed

This image shows the motion of the domain wall (ac and bd) in a capacitor when a charge is added to one side (c). The resulting redistribution of the domain wall causes a negative capacitive effect

Negative capacitor

After exploring the negative capacitance to create a transistor that spends less energy, researchers are now exploring the strange phenomenon to create new ways of storing and redistributing energy on the scale of microchips.

Igor Lukyanchuk and his colleagues from the USA, France, and Russia created a static and permanent negative capacitor, a component that up to 10 years ago was seen as a violation of the laws of physics.

While the previously proposed projects for negative capacitors operated on a temporary and transient basis, the new concept functions as a steady-state reversible device.

In traditional capacitors, the component's electrical voltage is proportional to its stored electrical charge - increasing the amount of stored charge increases the voltage. In negative capacitors, the opposite happens - increasing the amount of charge decreases the voltage.

Since the negative capacitor is a part of a larger circuit, this does not violate the law of energy conservation.

Electricity on demand

The team found that by pairing a negative capacitor in series with a standard positive capacitor, it is possible to locally increase the voltage on the positive capacitor to a point higher than the total system voltage.

In this way, it becomes possible to distribute electricity to regions of a circuit that require more voltage, while the bulk of the circuit remains running at low voltage.

This allows to rationalize the use of electricity inside chips and electronic circuits, using only what is strictly necessary, while still meeting the variable demands of each part of the circuit.

With this, it becomes possible to build circuits that consume less energy - the battery lasts longer - and heat less.


 Harnessing ferroelectric domains for negative capacitance
I. Lukyanchuk, Y. Tikhonov, A. SenΓ©, A. Razumnaya, VM Vinokur
 Nature Communications Physics Vol .: 2, Article number: 22
DOI: 10.1038 / s42005-019-0121-0

Monday, 24 June 2019

Superefficient memory for future computers uses T-rays

The necktie structure acts as an antenna to capture the T rays and change the state of the spin. [Image: Schlauderer et al. - 10.1038 / s41586-019-1174-7]

Data recording with T-rays

A team from Germany, Russia and the Netherlands was able to reverse the magnetic polarization of a material in the smallest time scales ever obtained, at a minimal energy cost.

When you take into account that 3% of all electricity produced in the world is already spent on data centers - the so-called cloud - any gain in the storage efficiency of each bit of information can make a big difference to the economy and the environment environment. This is one of the great objectives of the field of spintronics .

Computers store data in bits that alternate between two basic states, interpreted as zeros and ones. Remagnetizing the bit, making it change state, requires a lot of energy - and it's not as fast as we'd like.

The team developed a route for the ultrafast spinning of the spin in a material called thulium orthoferrite, one of the elements of the rare earth family.

The great news is that the switching is done by T rays, or terahertz radiation .


The new technique was possible because there seems to be a special connection between the spin states and the electrical component of a T-ray pulse. This allowed us to remagnetize the memory bits faster and more efficiently than is possible using pulses of magnetic field.

The terahertz pulses last in the range of the picoseconds, which corresponds to a cycle of light oscillation, that is, it is much faster than any current technology.

The switching of each spin was completed in only 3 picoseconds and almost no dissipation of energy - the team ensures that the dissipation of energy is at the minimum level of loss imposed by the fundamental laws of thermodynamics.

The next step is to move from proof of concept to components closer to end use.


 Temporal and spectral fingerprints of ultrafast all-coherent spin switching
S. Schlauderer, C. Lange, S. Baierl, T. Ebnet, CP Schmid, DC Valovcin, AK Zvezdin, AV Kimel, RV Mikhaylovskiy, R. Huber
 Nature Vol. : 569, pages 383-387
 DOI: 101038 / s41586-019-1174-7