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    Researchers develop all-optical approach to pumping chip-based nanolasers

    Researchers have developed a new all-optical method for driving multiple highly dense nanolaser arrays. The approach could enable chip-based optical communication links that process and move data faster than today’s electronic-based devices.
    “The development of optical interconnects equipped with high-density nanolasers would improve information processing in the data centers that move information across the internet,” said research team leader Myung-Ki Kim from Korea University. “This could allow streaming of ultra-high-definition movies, enable larger-scale interactive online encounters and games, accelerate the expansion of the Internet of Things and provide the fast connectivity needed for big data analytics.”
    In Optica, Optica Publishing Group’s journal for high-impact research, the researchers demonstrate that densely integrated nanolaser arrays — in which the lasers are just 18 microns apart — can be fully driven and programmed with light from a single optical fiber.
    “Optical devices integrated onto a chip are a promising alternative to electronic integrated devices, which are struggling to keep up with today’s data processing demands,” said Kim. “By eliminating the large and complex electrodes typically used to drive laser arrays, we reduced the overall dimensions of the laser array while also eliminating the heat generation and processing delays that come with electrode-based drivers.”
    Replacing electrodes with light
    The new nanolasers could be used in optical integrated circuit systems, which detect, generate, transmit and process information on a microchip via light. Instead of the fine copper wires used in electronic chips, optical circuits use optical waveguides, which allow much higher bandwidths while generating less heat. However, because the size of optical integrated circuits is quickly reaching into the nanometer regime, there is a need for new ways to drive and control their nano-sized light sources efficiently.
    To emit light, lasers need to be supplied with energy in a process called pumping. For nanolaser arrays, this is typically accomplished using a pair of electrodes for each laser within an array, which requires significant on-chip space and energy consumption while also causing processing delays. To overcome this critical limitation, the researchers replaced these electrodes with a unique optical driver that creates programmable patterns of light via interference. This pump light travels through an optical fiber onto which nanolasers are printed.
    To demonstrate this approach, the researchers used a high-resolution transfer-printing technique to fabricate multiple photonic crystal nanolasers spaced 18 microns apart. These arrays were applied onto the surface of a 2-micron-diameter optical microfiber. This had to be done in a way that precisely aligned the nanolaser arrays with the interference pattern. The interference pattern could also be modified by adjusting the driving beam’s polarization and pulse width.
    Laser driving with a single fiber
    The experiments showed that the design allowed multiple nanolaser arrays to be driven using light traveling through a single fiber. The results matched well with numerical calculations and showed that the printed nanolaser arrays could be fully controlled by the pump beam interference patterns.
    “Our all-optical laser driving and programming technology can also be applied to chip-based silicon photonics systems, which could play a key role in the development of chip-to-chip or on-chip optical interconnects,” said Kim. “However, it would be necessary to prove how independently the modes of a silicon waveguide can be controlled. If this can be done, it would be a huge leap forward in the advancement of on-chip optical interconnects and optical integrated circuits.”
    Story Source:
    Materials provided by Optica. Note: Content may be edited for style and length. More

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    Researchers develop wireless, ultrathin 'Skin VR' to provide a vivid, 'personalized' touch experience in the virtual world

    Enhancing the virtual experience with the touch sensation has become a hot topic, but today’s haptic devices remain typically bulky and tangled with wires. A team led by the City University of Hong Kong (CityU) researchers recently developed an advanced wireless haptic interface system, called WeTac, worn on the hand, which has soft, ultrathin soft features, and collects personalised tactile sensation data to provide a vivid touch experience in the metaverse.
    The system has application potential in gaming, sports and skills training, social activities, and remote robotic controls. “Touch feedback has great potential, along with visual and audial information, in virtual reality (VR), so we kept trying to make the haptic interface thinner, softer, more compact and wireless, so that it could be freely used on the hand, like a second skin,” said Dr Yu Xinge, Associate Professor in the Department of Biomedical Engineering (BME) at CityU, who led the research.
    Together with Professor Li Wenjung, Chair Professor in the Department of Mechanical Engineering (MNE), Dr Wang Lidai, Associate Professor in the Department of Biomedical Engineering (BME) and other collaborators, Dr Yu’s team developed WeTac, an ultra-flexible, wireless, integrated skin VR system. The research findings were published in the scientific journal Nature Machine Intelligence as the cover article, titled “Encoding of tactile information in hand via skin-integrated wireless haptic interface.”
    Light-weight, wireless, wearable hand patch instead of bulky gloves
    Existing haptic gloves rely mostly on bulky pumps and air ducts, powered and controlled through a bunch of cords and cables, which severely hinder the immersive experience of VR and augmented reality (AR) users. The newly developed WeTac overcomes these shortcomings with its soft, ultrathin, skin-integrated wireless electrotactile system.
    The system comprises two parts: a miniaturised soft driver unit, attached to the forearm as a control panel, and hydrogel-based electrode hand patch as a haptic interface. More

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    New robot does 'the worm' when temperature changes

    A new gelatinous robot that crawls, powered by nothing more than temperature change and clever design, brings “a kind of intelligence” to the field of soft robotics.
    The inchworm-inspired work is detailed today in Science Robotics.
    “It seems very simplistic but this is an object moving without batteries, without wiring, without an external power supply of any kind — just on the swelling and shrinking of gel,” said senior author David Gracias, a professor of chemical and biomolecular engineering at Johns Hopkins University. “Our study shows how the manipulation of shape, dimensions and patterning of gels can tune morphology to embody a kind of intelligence for locomotion.”
    Robots are made almost exclusively of hard materials like metals and plastics, a fundamental obstacle in the push to create if not more human-like robots, than robots ideal for human biomedical advancements.
    Water-based gels, which feel like gummy bears, are one of the most promising materials in the field of soft robotics. Researchers have previously demonstrated that gels that swell or shrink in response to temperature can be used to create smart structures. Here, the Johns Hopkins team demonstrated for the first time, how swelling and shrinking of gels can be strategically manipulated to move robots forward and backward on flat surfaces, or to essentially have them crawl in certain directions with an undulating, wave-like motion.
    The gelbots, which were created by 3D printing for this work, would be easy to mass produce. Gracias forsees a range of practical future applications, including moving on surfaces through the human body to deliver targeted medicines. They could also be marine robots, patrolling and monitoring the ocean’s surface.
    Gracias hopes to train the gelbots to crawl in response to variations in human biomarkers and biochemicals. He also plans to test other worm and marine organism-inspired shapes and forms and would like to incorporate cameras and sensors on their bodies.
    Authors included Aishwarya Pantula, Bibekananda Datta, Yupin Shi, Margaret Wang, Jiayu Liu, Siming Deng, Noah J. Cowan, and Thao D. Nguyen, all of Johns Hopkins.
    The work was supported by: National Science Foundation (EFMA-1830893).
    Story Source:
    Materials provided by Johns Hopkins University. Original written by Jill Rosen. Note: Content may be edited for style and length. More

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    Chaos gives the quantum world a temperature

    A single particle has no temperature. It has a certain energy or a certain speed — but it is not possible to translate that into a temperature. Only when dealing with random velocity distributions of many particles, a well-defined temperature emerges.
    How can the laws of thermodynamics arise from the laws of quantum physics? This is a topic that has attracted growing attention in recent years. At TU Wien (Vienna), this question has now been pursued with computer simulations, which showed that chaos plays a crucial role: Only where chaos prevails do the well-known rules of thermodynamics follow from quantum physics.
    Boltzmann: Everything is possible, but it may be improbable
    The air molecules randomly flying around in a room can assume an unimaginable number of different states: Different locations and different speeds are allowed for each individual particle. But not all of these states are equally likely. “Physically, it would be possible for all the energy in this space to be transferred to one single particle, which would then move at extremely high speeds while all the other particles stand still,” says Prof. Iva Brezinova from the Institute of Theoretical Physics at TU Wien. “But this is so unlikely that it will practically never be observed.”
    The probabilities of different allowed states can be calculated — according to a formula that the Austrian physicist Ludwig Boltzmann set up according to the rules of classical physics. And from this probability distribution, the temperature can then also be read off: it is only determined for a large number of particles.
    The whole world as a single quantum state
    However, this causes problems when dealing with quantum physics. When a large number of quantum particles are in play at the same time, the equations of quantum theory become so complicated that even the best supercomputers in the world have no chance of solving them. More

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    2022’s biggest climate change bill pushes clean energy

    The world needed bold climate action this year, and we got it.

    California and other states announced plans to phase out gas-powered cars after 2035. The United States ratified an international treaty to slash production of the climate-warming hydrofluorocarbons used in cooling and refrigeration. The European Union is finalizing its plan to cut greenhouse gas emissions by 55 percent relative to 1990s levels by 2030. The list of legislative victories goes on.

    But the biggest win came August 16, when President Joe Biden signed into law the Inflation Reduction Act.

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    The historic legislation marks the first major move by the United States, which has emitted more carbon dioxide than any other country, toward neutralizing greenhouse gas emissions. It gets the ball rolling by investing $369 billion into accelerating the adoption of wind, solar and other renewable energy sources and decarbonizing the economy. By the end of the decade, the act will help cut U.S. greenhouse gas emissions by around 40 percent of the levels in 2005, when U.S. emissions nearly peaked, scientists project, bringing the nation within reach of fulfilling its pledge to halve emissions by 2030.

    The legislation is no panacea for the climate emergency, but researchers and activists are optimistic that it will be the helping hand that clean energy needs to flourish. “There would be no way to really mitigate the climate crisis without the investments in this bill,” says Raul Garcia, a legislative director at Earthjustice, a nonprofit environmental law organization.

    Here’s a look at some of the law’s major provisions and a few of its limitations.

    Cheaper clean energy

    The law aims to ease and incentivize the transition away from fossil fuels by creating tax credits that reduce the cost for companies to adopt clean energy. For instance, small businesses can qualify for credits that support up to 30 percent of the cost of transitioning to solar power.

    The act also aims to help consumers, with $9 billion for rebates that help people ditch gas and buy appliances powered by electricity, such as electric induction cooktops and heat pump water heaters. Households can also get up to $7,500 in tax credits for electric vehicle purchases.

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    “It’s huge,” Denise Mauzerall, an atmospheric scientist at Princeton University, says of the law’s potential to advance clean energy. But if the United States is to take full advantage of the increased clean energy capacity, it will be crucial to also construct sufficient infrastructure to deliver that energy, she notes. The bill offers only some support to build overhead power lines and other ways to transmit energy. “Without transmission,” she says, “we will really slow ourselves down.”

    Clean energy jobs and goods

    A major goal is to build up a clean energy economy by promoting high-quality jobs in industries such as solar and wind. To maximize tax credits, companies must pay workers a “prevailing wage” and employ apprentices to work a minimum number of hours on clean energy projects.

    The legislation also invests in the domestic manufacturing of clean energy goods. Tax credits of up to 30 percent are available to companies that build or recycle wind turbine blades, solar panels, energy storage equipment and other clean energy products, and funds grants to retool factories to make electric vehicles.

    Through tax credits, the Inflation Reduction Act promotes high-quality jobs in the wind and energy industries, like workers at solar power stations.Sinology/Moment/Getty Images

    Reducing pollution

    Methane — a greenhouse gas that can trap more than 25 times as much heat as CO2 — is another target. The legislation devotes $850 million to the monitoring and mitigation of methane emissions from fossil fuel operations. It also establishes a fine for operations that annually release amounts of methane that exceed 25,000 metric tons of CO2 equivalent.

    And CO2 is legally defined as an “air pollutant,” cementing the Environmental Protection Agency’s authority to regulate its production under the Clean Air Act.

    But there’s more to the climate problem than decarbonizing today’s pollutive energy industry, Mauzerall says. “Going forward, we need to pay more attention to reducing emissions from the agricultural sector,” she says. About 11 percent of U.S. greenhouse gas emissions and about a third of global emissions come from agriculture (SN: 5/7/22 & 5/21/22, p. 22).

    Climate justice

    Billions of dollars are slated to go toward climate justice, a movement that confronts the disproportionate impacts of climate change on marginalized communities. Funding includes $2.8 billion in grants for community-based projects, such as those that increase energy efficiency in affordable housing developments or monitor air quality in marginalized communities.

    “But there are some troubling provisions,” Garcia says. The law authorizes new offshore oil and gas leases and provides fossil fuel companies with carbon capture and sequestration tax credits. These could prolong the life of pollutive oil and gas operations, which are often located near marginalized communities.

    It will be crucial to follow these investments with laws that enforce both climate justice and the clean energy transition, Garcia says. “We need rules and regulations that hold industries’ feet to the fire, to make sure that those investments are going where they need to.” More

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    Quantum dots at room temp, using lab-designed protein

    Nature uses 20 canonical amino acids as building blocks to make proteins, combining their sequences to create complex molecules that perform biological functions.
    But what happens with the sequences not selected by nature? And what possibilities lie in constructing entirely new sequences to make novel, or de novo, proteins bearing little resemblance to anything in nature?
    That’s the terrain Princeton University’s Hecht Lab works in. And recently, their curiosity for designing their own sequences paid off.
    They discovered the first known de novo protein that catalyzes, or drives, the synthesis of quantum dots. Quantum dots are fluorescent nanocrystals used in electronic applications from LED screens to solar panels.
    Their work opens the door to making nanomaterials in a more sustainable way by demonstrating that protein sequences not derived from nature can be used to synthesize functional materials — with pronounced benefits to the environment.
    Quantum dots are normally made in industrial settings with high temperatures and toxic, expensive solvents — a process that is neither economical nor environmentally friendly. But Hecht Lab researchers pulled off the process at the bench using water as a solvent, making a stable end-product at room temperature. More

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    Particles of light may create fluid flow, data-theory comparison suggests

    A new computational analysis by theorists at the U.S. Department of Energy’s Brookhaven National Laboratory and Wayne State University supports the idea that photons (a.k.a. particles of light) colliding with heavy ions can create a fluid of “strongly interacting” particles. In a paper just published in Physical Review Letters, they show that calculations describing such a system match up with data collected by the ATLAS detector at Europe’s Large Hadron Collider (LHC).
    As the paper explains, the calculations are based on the hydrodynamic particle flow seen in head-on collisions of various types of ions at both the LHC and the Relativistic Heavy Ion Collider (RHIC), a DOE Office of Science user facility for nuclear physics research at Brookhaven Lab. With only modest changes, these calculations also describe flow patterns seen in near-miss collisions, where photons that form a cloud around the speeding ions collide with the ions in the opposite beam.
    “The upshot is that, using the same framework we use to describe lead-lead and proton-lead collisions, we can describe the data of these ultra-peripheral collisions where we have a photon colliding with a lead nucleus,” said Brookhaven Lab theorist Bjoern Schenke, a coauthor of the paper. “That tells you there’s a possibility that, in these photon-ion collisions, we create a small dense strongly interacting medium that is well described by hydrodynamics — just like in the larger systems.”
    Fluid signatures
    Observations of particles flowing in characteristic ways have been key evidence that the larger collision systems (lead-lead and proton-lead collisions at the LHC; and gold-gold and proton-gold collisions at RHIC) create a nearly perfect fluid. The flow patterns were thought to stem from the enormous pressure gradients created by the large number of strongly interacting particles produced where the colliding ions overlap.
    “By smashing these high-energy nuclei together we’re creating such high energy density — compressing the kinetic energy of these guys into such a small space — that this stuff essentially behaves like a fluid,” Schenke said. More

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    Model shows how intelligent-like behavior can emerge from non-living agents

    From a distance, they looked like clouds of dust. Yet, the swarm of microrobots in author Michael Crichton’s bestseller “Prey” was self-organized. It acted with rudimentary intelligence, learning, evolving and communicating with itself to grow more powerful.
    A new model by a team of researchers led by Penn State and inspired by Crichton’s novel describes how biological or technical systems form complex structures equipped with signal-processing capabilities that allow the systems to respond to stimulus and perform functional tasks without external guidance.
    “Basically, these little nanobots become self-organized and self-aware,” said Igor Aronson, Huck Chair Professor of Biomedical Engineering, Chemistry, and Mathematics at Penn State, explaining the plot of Crichton’s book. The novel inspired Aronson to study the emergence of collective motion among interacting, self-propelled agents. The research was recently published in Nature Communications.
    Aronson and a team of physicists from the LMU University, Munich, have developed a new model to describe how biological or synthetic systems form complex structures equipped with minimal signal-processing capabilities that allow the systems to respond to stimulus and perform functional tasks without external guidance. The findings have implications in microrobotics and for any field involving functional, self-assembled materials formed by simple building blocks, Aronson said. For example, robotics engineers could create swarms of microrobots capable of performing complex tasks such as pollutant scavenging or threat detection.
    “If we look to nature, we see that many living creatures rely on communication and teamwork because it enhances their chances of survival,” Aronson said.
    The computer model conceived by researchers from Penn State and Ludwig-Maximillian University predicted that communications by small, self-propelled agents lead to intelligent-like collective behavior. The study demonstrated that communications dramatically expand an individual unit’s ability to form complex functional states akin to living systems. More