Tyler O'Neal, Staff Editor ASTRONOMY

Spin waves unlock the next generation of computer technology, a new component allows physicists to control them

Researchers at Aalto University have developed a new device for spintronics. The results mark a step towards the goal of using spintronics to make computer chips and devices for data processing and communication technology that are small and powerful.

Traditional electronics uses electrical charge to carry out computations that power most of our day-to-day technology. However, engineers are unable to make electronics do calculations faster, as moving charge creates heat, and we're at the limits of how small and fast chips can get before overheating. Because electronics can't be made smaller, there are concerns that supercomputers won't be able to get more powerful and cheaper at the same rate they have been for the past 7 decades. This is where spintronics comes in.

"Spin" is a property of particles like electrons in the same way that "charge" is. Researchers are excited about using spin to carry out computations because it avoids the heating issues of current computer chips. 'If you use spin waves, it's transfer of spin, you don't move charge, so you don't create heating,' says Professor Sebastiaan van Dijken, who leads the group that wrote the paper. Magneto-optical microscope used for imaging spin waves in a Fabry-Pérot resonator CREDIT Matt Allinson, Aalto University

Nanoscale magnetic materials

The device the team made is a Fabry-Pérot resonator, a well known tool in optics for creating beams of light with a tightly controlled wavelength. The spin-wave version made by the researchers in this work allows them to control and filter waves of spin in devices that are only a few hundreds of nanometres across.

The devices were made by sandwiching very thin layers of materials with exotic magnetic properties on top of eachother. This created a device where the spin waves in the material would be trapped and cancelled out if they weren't of the desired frequency. 'The concept is new, but easy to implement,' explains Dr Huajun Qin, the first author of the paper, 'the trick is to make good quality materials, which we have here at Aalto. The fact that it is not challenging to make these devices means we have lots of opportunities for new exciting work.'

Wireless data processing and analogue computing

The issues with speeding up electronics goes beyond overheating, they also cause complications in wireless transmission, as wireless signals need to be converted from their higher frequencies down to frequencies that electronic circuits can manage. This conversion slows the process down, and requires energy. Spin wave chips are able to operate at the microwave frequencies used in mobile phone and wifi signals, which means that there is a lot of potential for them to be used in even faster and more reliable wireless communication technologies in the future.

Furthermore, spin waves can be used to do computing in ways that are faster that electronic computing at specific tasks 'Electronic computing uses "Boolean" or Binary logic to do calculations,' explains Professor van Dijken, 'with spin waves, the information is carried in the amplitude of the wave, which allows for more analogue style computing. This means that it could be very useful for specific tasks like image processing, or pattern recognition. The great thing about our system is that the size structure of it means that it should be easy to integrate into existing technology'

Now that the team has the resonator to filter and control the spin waves, the next steps are to make a complete circuit for them. "To build a magnetic circuit, we need to be able to guide the spin waves towards functional components, like the way conducting electrical channels do on electronic microchips. We are looking at making similar structures to steer spin waves" explains Dr Qin.

EPFL scientist develops new tech to build ultralow-loss integrated photonic circuits

Tyler O'Neal, Staff Editor ASTRONOMY

Encoding information into light, and transmitting it through optical fibers lies at the core of optical communications. With an incredibly low loss of 0.2 dB/km, optical fibers made from silica have laid the foundations of today's global telecommunication networks and our information society.

Such ultralow optical loss is equally essential for integrated photonics, which enable the synthesis, processing and detection of optical signals using on-chip waveguides. Today, a number of innovative technologies are based on integrated photonics, including semiconductor lasers, modulators, and photodetectors, and are used extensively in data centers, communications, sensing and supercomputing. Integrated silicon nitride photonic chips with meter-long spiral waveguides. CREDIT Jijun He, Junqiu Liu (EPFL)

Integrated photonic chips are usually made from silicon that is abundant and has good optical properties. But silicon can't do everything we need in integrated photonics, so new material platforms have emerged. One of these is silicon nitride (Si3N4), whose exceptionally low optical loss (orders of magnitude lower than that of silicon), has made it the material of choice for applications for which low loss is critical, such as narrow-linewidth lasers, photonic delay lines, and nonlinear photonics.

Now, scientists in the group of Professor Tobias J. Kippenberg at EPFL's School of Basic Sciences have developed a new technology for building silicon nitride integrated photonic circuits with record low optical losses and small footprints. The work is published in an academic journal.

Combining nanofabrication and material science, the technology is based on the photonic Damascene process developed at EPFL. Using this process, the team made integrated circuits of optical losses of only 1 dB/m, a record value for any nonlinear integrated photonic material. Such low loss significantly reduces the power budget for building chip-scale optical frequency combs ("microcombs"), used in applications like coherent optical transceivers, low-noise microwave synthesizers, LiDAR, neuromorphic computing, and even optical atomic clocks. The team used the new technology to develop meter-long waveguides on 5x5 mm2 chips and high-quality-factor microresonators. They also report high fabrication yield, which is essential for scaling up to industrial production.

"These chip devices have already been used for parametric optical amplifiers, narrow-linewidth lasers and chip-scale frequency combs", says Dr. Junqiu Liu who led the fabrication at EPFL's Center of MicroNanoTechnology (CMi). "We are also looking forward to seeing our technology being used for emerging applications such as coherent LiDAR, photonic neural networks, and quantum computing."

Russian physicist finds a method to more effectively predict properties of ClO2 isotopologues

Tyler O'Neal, Staff Editor ASTRONOMY

Scientists of Tomsk Polytechnic University have researched the 35ClO2 isotope and developed a mathematical model and software that predicts characteristics by 10 folds more accurately than already known results. The research work was conducted by a research team of Russian, German, and Swiss scientists. The research findings are published in the Physical Chemistry Chemical Physics (IF: 3,4; Q1) academic journal and listed as one of the best articles.

The ClO2 molecule is extremely important for medicine and biophysics, as well as for the Earth's atmosphere. It is used in medicine for disinfection and sterilization. On a global scale, ClO2 plays a crucial role in the formation and migration of ozone holes.

"The theoretical background for nonlinear molecules in so-called non-singlet electronic states, including ClO2, has been poorly developed until very recently. To study such molecules, scientists use a mathematical apparatus for linear molecules. As the molecule and its structure are different, there are large observational errors. 

We created a mathematical model that takes into account subtle effects, the interaction of rotations, and spin-rotational interactions in nonlinear molecules. The mathematical model gives the results with high accuracy that allows obtaining unique data and, the most important is that predicting the properties of molecules with high accuracy," Oleg Ulenekov, Professor of the TPU Research School of High-Energy Physics, the co-author of the article, says.

The TPU scientists compiled the mathematical model of the 35ClO2 molecule for double electronic states and included it in computer codes. This software application can read and predict experimental data, that is properties of a molecule in the given range and its state transitions. Spectral analysis of the molecule based on the compiled model possesses the result by 10 folds accurately than already known ones.

The scientists conducted an analysis of rotational-vibrational spectra in a degenerate electronic state based on the created model. The experimental basis of the research work was conducted in the Laboratory for Molecular Spectroscopy at Technical University of Braunschweig (Germany) and ETH Zurich (Switzerland).

According to the scientists, the compiled model possesses a more unique character and it can be developed and adapted to the other ranges.

"Having published the results, the editorial staff of the journal reported that the article was selected and put in the hot topic section, the so-called pool of the best articles. Such recognition of the work of the international research team is very important and valuable. We are planning to continue the research work and apply the model for analysis of the 37ClO2 isotope," Elena Bekhtereva and Olga Gromova, Professors of the TPU Research School of High-Energy Physics, the co-authors of the article, add.