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Category: materials – Page 10

Imaginary Time Delays Are For Real

The time delay experienced by a scattered light signal has an imaginary part that was considered unobservable, but researchers have isolated its effect in a frequency shift.

A scattering material, such as a frosted window or a thin fog, will cause light to travel slower than it would if no material were in its path. The mathematical formula for this time delay has a real part—which is well studied—and a lesser-known imaginary part. “The imaginary time delay has been largely ignored and disregarded as unphysical,” says Isabella Giovannelli from the University of Maryland. But she and her advisor Steven Anlage have now measured this abstract quantity by recording a corresponding frequency shift in scattered light pulses [1].

The real part of the time delay has been observed in many experiments, particularly slow-light setups where light pulses can become effectively trapped inside a scattering medium (see Focus: Light Nearly Stopped in a Waveguide). By contrast, the imaginary part has been stuck in the realm of mathematics. Theoretical work from 2016, however, showed that the imaginary time delay can be related to a potentially observable frequency shift [2].

Researchers make key gains in unlocking the promise of compact X-ray free-electron lasers

New research by scientists from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), in collaboration with scientists from TAU Systems Inc., has brought the promise of smaller and more affordable X-ray free-electron lasers one step closer to reality.

X-ray free-electron lasers (XFELs) are powerful light sources and are typically large research instruments. Scientists use them to probe nature’s secrets at the atomic level, enabling advances in medicine, biology, physics, materials, and more. The push to develop more compact and less expensive XFELs is expected to increase the number of facilities that will be able to implement this technology, greatly expanding its impact across many areas of science.

“As part of this effort, we are applying our long-standing expertise in a type of advanced accelerator called laser plasma acceleration to shrink XFELs,” said Sam Barber, a staff scientist in Berkeley Lab’s Accelerator Technology & Applied Physics (ATAP) Division. “In addition to standalone light sources, exceptionally high-quality electron beams from plasma accelerators could be injected into existing XFELs to significantly extend their performance.”

Cost effective method developed for co-packaging photonic and electronic chips

The future of digital computing and communications will involve both electronics—manipulating data with electricity—and photonics, or doing the same with light. Together the two could allow exponentially more data traffic across the globe in a process that is also more energy efficient.

“The bottom line is that integrating photonics with electronics in the same package is the transistor for the 21st century. If we can’t figure out how to do that, then we’re not going to be able to scale forward,” says Lionel Kimerling, the Thomas Lord Professor of Materials Science and Engineering at MIT and director of the MIT Microphotonics Center.

Enter FUTUR-IC, a new research team based at MIT. “Our goal is to build a microchip industry value chain that is resource-efficient,” says Anu Agarwal, head of FUTUR-IC and a principal research scientist at the Materials Research Laboratory (MRL).

AI-designed 3D materials enable custom control over how light bends

Refraction—the bending of light as it passes through different media—has long been constrained by physical laws that prevent independent control over how light waves along different directions bend. Now, UCLA researchers have developed a new class of passive materials that can be structurally engineered to “program” refraction, enabling arbitrary control over the bending of light waves.

In a study published in Nature Communications, a team led by Dr. Aydogan Ozcan, the Chancellor’s Professor of Electrical & Computer Engineering at UCLA, has introduced a called a refractive function generator (RFG) that can independently tailor the output direction of refracted light for each input direction. This device allows light to be steered, filtered, or redirected according to custom-designed rules—far beyond what standard materials or traditional metasurfaces can achieve.

Standard refraction, described by Snell’s law, links the input and output directions of light using fixed material properties. Even advanced metasurface designs only allow limited tunability of refraction.

Direct electrolysis systems turns waste alkaline water into clean hydrogen

Dr. Sung Mook Choi and his research team at the Energy & Environmental Materials Research Division of the Korea Institute of Materials Science (KIMS) have successfully developed a highly durable non-precious metal-based hydrogen evolution catalyst for use in a direct electrolysis system employing waste alkaline water and anion exchange membranes (AEM). This breakthrough enables the production of clean hydrogen by directly utilizing alkaline wastewater generated from industrial processes.

Stainless-steel component boosts bacteria-based biobattery

Engineering innovations generally require long hours in the lab, with a lot of trial and error through experimentation before zeroing in on the best solution.

But sometimes, if you’re lucky, the answer can be right under your nose—or in this case, beneath your feet.

Binghamton University Professor Seokheun “Sean” Choi has developed a series of bacteria-fueled biobatteries over the past decade, building on what he has learned to improve the next iteration. The biggest limitation isn’t his imagination—he’s always juggling several projects at once—but the materials he has to work with.

New framework clears spin-orbit confusion in solids and unifies physics

The researchers came up with a new way to describe how an electron’s spin interacts with the material it moves through, without using the complicated and unreliable tool called the orbital angular momentum operator, which usually causes problems in crystals.

Instead, they introduced a new idea called relativistic spin-lattice interaction. This basically means they focused on how an electron’s spin reacts to the structure of the solid itself, using principles from Einstein’s theory of relativity.

Cosmic baby steps: For the first time, astronomers witness the dawn of a new solar system

For the first time, international researchers have pinpointed the moment when planets began to form around a star beyond the sun. Using the ALMA telescope, in which the European Southern Observatory (ESO) is a partner, and the James Webb Space Telescope, they have observed the creation of the first specks of planet-forming material—hot minerals just beginning to solidify. This finding marks the first time a planetary system has been identified at such an early stage in its formation and opens a window to the past of our own solar system.

“For the first time, we have identified the earliest moment when planet formation is initiated around a star other than our sun,” says Melissa McClure, a professor at Leiden University in the Netherlands and lead author of the new study, published in Nature.

Co-author Merel van ‘t Hoff, a professor at Purdue University, U.S., compares their findings to “a picture of the baby solar system,” saying, “We’re seeing a system that looks like what our solar system looked like when it was just beginning to form.”

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