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Trump’s dispute with Musk shows the danger of private monopolies in space

The world recently watched an argument unfold on X between Elon Musk and Donald Trump. It was a surreal exchange, featuring one of the richest men ever to have lived […]
The post Trump’s dispute with Musk shows the danger of private monopolies in space appeared first on SpaceNews.
ESA signs agreement for potential use of Orbital Reef

The European Space Agency has signed an agreement regarding potential use of Orbital Reef as it refines its strategy for use of commercial space stations.
The post ESA signs agreement for potential use of Orbital Reef appeared first on SpaceNews.
The FDA Just Approved a Long-Lasting Injection to Prevent HIV
Landspace performs 9-engine static fire test for reusable Zhuque-3 rocket

Chinese launch startup Landspace carried out a breakthrough static fire test Friday as it builds towards an orbital launch attempt with its Zhuque-3 rocket.
The post Landspace performs 9-engine static fire test for reusable Zhuque-3 rocket appeared first on SpaceNews.
ESA and EU emphasize good relationship as they press forward on imaging constellation

The European Space Agency and European Commission say their relationship is closer than ever as they embark on a new satellite program.
The post ESA and EU emphasize good relationship as they press forward on imaging constellation appeared first on SpaceNews.
AI algorithms in radiology: how to identify and prevent inadvertent bias
Artificial intelligence (AI) has the potential to generate a sea change in the practice of radiology, much like the introduction of radiology information system (RIS) and picture archiving and communication system (PACS) technology did in the late 1990s and 2000s. However, AI-driven software must be accurate, safe and trustworthy, factors that may not be easy to assess.
Machine learning software is trained on databases of radiology images. But these images might lack the data or procedures needed to prevent algorithmic bias. Such algorithmic bias can cause clinical errors and performance disparities that affect a subset of the analyses that the AI performs, unintentionally disadvantaging certain groups of patients.
A multinational team of radiology informaticists, biomedical engineers and computer scientists has identified potential pitfalls in the evaluation and measurement of algorithmic bias in AI radiology models. Describing their findings in Radiology, the researchers also suggest best practices and future directions to mitigate bias in three key areas: medical image datasets; demographic definitions; and statistical evaluations of bias.
Medical imaging datasets
The medical image datasets used for training and evaluation of AI algorithms are reflective of the population from which they are acquired. It is natural that a dataset acquired in a country in Asia will not be representative of the population in a Nordic country, for example. But if there’s no information available about the image acquisition location, how might this potential source of bias be determined?

Lead author Paul Yi, of St. Jude Children’s Research Hospital in Memphis, TN, and coauthors advise that many existing medical imaging databases lack a comprehensive set of demographic characteristics, such as age, sex, gender, race and ethnicity. Additional potential confounding factors include the scanner brand and model, the radiology protocols used for image acquisition, radiographic views acquired, the hospital location and disease prevalence. In addition to incorporating these data, the authors recommend that raw image data are collected and shared without institution-specific post-processing.
The team advise that generative AI, a set of machine learning techniques that generate new data, provides the potential to create synthetic imaging datasets with more balanced representation of both demographic and confounding variables. This technology is still in development, but might provide a solution to overcome pitfalls related to measurement of AI biases in imperfect datasets.
Defining demographics
Radiology researchers lack consensus with respect to how demographic variables should be defined. Observing that demographic categories such as gender and race are self-identified characteristics informed by many factors, including society and lived experiences, the authors advise that concepts of race and ethnicity do not necessarily translate outside of a specific society and that biracial individuals reflect additional complexity and ambiguity.
They emphasize that ensuring accurate measurements of race- and/or ethnicity-based biases in AI models is important to enable accurate comparison of bias evaluations. This not only has clinical implications, but is also essential to prevent health policies being established in error from erroneous AI-derived findings, which could potentially perpetuate pre-existing inequities.
Statistical evaluations of bias
The researchers define bias in the context of demographic fairness and how it reflects differences in metrics between demographic groups. However, establishing consensus on the definition of bias is complex, because bias can have different clinical and technical meanings. They point out that in statistics, bias refers to a discrepancy between the expected value of an estimated parameter and its true value.
As such, the radiology speciality needs to establish a standard notion of bias, as well as tackle the incompatibility of fairness metrics, the tools that measure whether a machine learning model treats certain demographic groups differently. Currently there is no universal fairness metric that can be applied to all cases and problems, and the authors do not think there ever will be one.
The different operating points of predictive AI models may result in different performance that could lead to potentially different demographic biases. These need to be documented, and thresholds should be included in research and by commercial AI software vendors.
Key recommendations
The authors suggest some key courses of action to mitigate demographic biases in AI in radiology:
- Improve reporting of demographics by establishing a consensus panel to define and update reporting standards.
- Improve dataset reporting of non-demographic factors, such as imaging scanner vendor and model.
- Develop a standard lexicon of terminology for concepts of fairness and AI bias concepts in radiology.
- Develop standardized statistical analysis frameworks for evaluating demographic bias of AI algorithms based on clinical contexts
- Require greater demographic detail to evaluate algorithmic fairness in scientific manuscripts relating to AI models.
Yi and co-lead collaborator Jeremias Sulam, of Johns Hopkins School of Medicine in Baltimore, MD, tell Physics World that their assessment of pitfalls and recommendations to mitigate demographic biases reflect years of multidisciplinary discussion. “While both the clinical and computer science literature had been discussing algorithmic bias with great enthusiasm, we learned quickly that the statistical notions of algorithmic bias and fairness were often quite different between the two fields,” says Yi.
“We noticed that progress to minimize demographic biases in AI models is often hindered by a lack of effective communication between the computer science and statistics communities and the clinical world, radiology in particular,” adds Sulam.
A collective effort to address the challenges posed by bias and fairness is important, notes Melissa Davis of Yale School of Medicine, in an accompanying editorial in Radiology. “By fostering collaboration between clinicians, researchers, regulators and industry stakeholders, the healthcare community can develop robust frameworks that prioritize patient safety and equitable outcomes,” she writes.
The post AI algorithms in radiology: how to identify and prevent inadvertent bias appeared first on Physics World.
A Rare Whale Tooth Reveals a Copper-Age Community’s Connection to the Sea
FDA Approves Breakthrough HIV Drug, but It Could Be Hard to Access
Earwax With an Unusual Odor May Help Detect Parkinson's Before It Worsens
French government to lead Eutelsat’s $1.56 billion capital boost

France would more than double its stake in Eutelsat to nearly 30% as part of a $1.56 billion capital raise backed by multiple shareholders, bolstering the French operator’s plans to refresh its OneWeb constellation amid Starlink’s growing dominance.
The post French government to lead Eutelsat’s $1.56 billion capital boost appeared first on SpaceNews.
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Discover Mag
- Repurposing Urine Into a Valuable Biomaterial Could Benefit Dental Implants, and Construction
Repurposing Urine Into a Valuable Biomaterial Could Benefit Dental Implants, and Construction
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SpaceNews
- Moog Now Accepting Orders for Software Development Units for New High-Speed Space Computers
Moog Now Accepting Orders for Software Development Units for New High-Speed Space Computers

Gilbert, AZ – Moog Inc. (NYSE: MOG.A and MOG.B), a worldwide designer, manufacturer and systems integrator of high-performance precision motion and fluid controls and control systems, is now accepting orders […]
The post Moog Now Accepting Orders for Software Development Units for New High-Speed Space Computers appeared first on SpaceNews.
146,000-Year-Old Dragon Man Skull Confirmed as Denisovan Through Dental DNA
No sour faces: How birds evolved to eat highly acidic fruits
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Science Magazine
- New approach enables body to engineer its own cells to fight cancer or autoimmunity
New approach enables body to engineer its own cells to fight cancer or autoimmunity
Portal Space Systems to build larger factory for Supernova vehicle

Portal Space Systems will create a second factory to scale up production of high-performance in-space vehicles as it gears up for initial test flights in 2026.
The post Portal Space Systems to build larger factory for Supernova vehicle appeared first on SpaceNews.
The ultimate backup drive: the moon

In this week's episode of Space Minds, we explore how microgravity accelerates aging—and guest Dr. Nadia Maroouf shares her insights on the phenomenon and what she’s doing to help protect astronauts.
The post The ultimate backup drive: the moon appeared first on SpaceNews.
RFK Jr.’s Appointees to CDC Vaccine Panel Are Not Good
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Physics World
- Helgoland: leading scientists reflect on 100 years of quantum physics and look to the future
Helgoland: leading scientists reflect on 100 years of quantum physics and look to the future
Last week, Physics World’s Matin Durrani boarded a ferry in Hamburg that was bound for Helgoland – an archipelago in the North Sea about 70 km off the north-west coast of Germany.
It was a century ago in Helgoland that the physicist Werner Heisenberg devised the mathematical framework that underpins our understanding of quantum physics.
Matin was there with some of the world’s leading quantum physicists for the conference Helgoland 2025: 100 Years of Quantum Mechanics – which celebrated Heisenberg’s brief stay in Helgoland.
He caught up with three eminent physicists and asked them to reflect on Heisenberg’s contributions to quantum mechanics and look forward to the next 100 years of quantum science and technology. They are Tracy Northup at the University of Vienna; Michelle Simmons of the University of New South Wales, Sydney; and Peter Zoller of the University of Innsbruck.
• Don’t miss the 2025 Physics World Quantum Briefing, which is free to read via this link.
This article forms part of Physics World‘s contribution to the 2025 International Year of Quantum Science and Technology (IYQ), which aims to raise global awareness of quantum physics and its applications.
Stayed tuned to Physics World and our international partners throughout the next 12 months for more coverage of the IYQ.
Find out more on our quantum channel.
The post Helgoland: leading scientists reflect on 100 years of quantum physics and look to the future appeared first on Physics World.
After Resilience’s moon landing attempt, why openness is key to the lunar economy

Last week, I looked at the faces of our guests at our moon landing event and watched as awe, wonder and hopefulness transformed into disappointment. Moments before the expected touch […]
The post After Resilience’s moon landing attempt, why openness is key to the lunar economy appeared first on SpaceNews.
How Much Energy Does AI Use? The People Who Know Aren’t Saying
Laser World of Photonics showcases cutting-edge optical innovation
Laser World of Photonics, the leading trade show for the laser and photonics industry, takes place in Munich from 24 to 27 June. Attracting visitors and exhibitors from around the world, the event features 11 exhibition areas covering the entire spectrum of photonic technologies – including illumination and energy, biophotonics, data transmission, integrated photonics, laser systems, optoelectronics, sensors and much more.
Running parallel and co-located with Laser World of Photonics is World of Quantum, the world’s largest trade fair for quantum technologies. Showcasing all aspects of quantum technologies – from quantum sensors and quantum computers to quantum communications and cryptography – the event provides a platform to present innovative quantum-based products and discuss potential applications.
Finally, the World of Photonics Congress (running from 22 to 27 June) features seven specialist conferences, over 3000 lectures and around 6700 experts from scientific and industrial research.
The event is expecting to attract around 40,000 visitors from 70 countries, with the trade shows incorporating 1300 exhibitors from 40 countries. Here are some of the companies and product innovations to look out for on the show floor.
HOLOEYE unveils compact 4K resolution spatial light modulator
HOLOEYE Photonics AG, a leading provider of spatial light modulator (SLM) devices, announces the release of the GAEA-C spatial light modulator, a compact version of the company’s high-resolution SLM series. The GAEA-C will be officially launched at Laser World of Photonics, showcasing its advanced capabilities and cost-effective design.

The GAEA-C is a phase-only SLM with a 4K resolution of 4094 x 2400 pixels, with an exceptionally small pixel pitch of 3.74 µm. This compact model is equipped with a newly developed driver solution that not only reduces costs but also enhances phase stability, making it ideal for a variety of applications requiring precise light modulation.
The GAEA-C SLM features a reflective liquid crystal on silicon (LCOS) display (phase only). Other parameters include a fill factor of 90%, an input frame rate of 30 Hz and a maximum spatial resolution of 133.5 lp/mm.
The GAEA-C is available in three versions, each optimized for a different wavelength range: a VIS version (420–650 nm), a NIR version (650–1100 nm) and a version tailored for the telecommunications waveband around 1550 nm. This versatility ensures that the GAEA-C can meet the diverse needs of industries ranging from telecoms to scientific research.
HOLOEYE continues to lead the market with its innovative SLM solutions, providing unparalleled resolution and performance. The introduction of the GAEA-C underscores HOLOEYE’s commitment to delivering cutting-edge technology that meets the evolving demands of its customers.
- For more information about the GAEA-C and other SLM products, visit HOLOEYE at booth #225 in Hall A2.
Avantes launches NIR Enhanced spectrometers
At this year’s Laser World of Photonics, Avantes unveils its newest generation of spectrometers: the NEXOS NIR Enhanced and VARIUS NIR Enhanced. Both instruments mark a significant leap in near-infrared (NIR) spectroscopy, offering up to 2x improved sensitivity and unprecedented data quality for integration into both research and industry applications.

Compact, robust and highly modular, the NEXOS NIR Enhanced spectrometer redefines performance in a small form factor. It features enhanced NIR quantum efficiency in the 700–1100 nm range, with up to 2x increased sensitivity, fast data transfer and improved signal-to-noise ratio. The USB-powered spectrometer is designed with a minimal footprint of just 105 x 80 x 20 mm and built using AvaMation production for top-tier reproducibility and scalability. It also offers seamless integration with third-party software platforms.
The NEXOS NIR Enhanced is ideal for food sorting, Raman applications and VCSEL/laser system integration, providing research-grade performance in a compact housing. See the NEXOS NIR Enhanced product page for further information.
Designed for flexibility and demanding industrial environments, the VARIUS NIR Enhanced spectrometer introduces a patented optical bench for supreme accuracy, with replaceable slits for versatile configurations. The spectrometer offers a dual interface – USB 3.0 and Gigabit Ethernet – plus superior stray light suppression, high dynamic range and enhanced NIR sensitivity in the 700–1100 nm region.
With its rugged form factor (183 x 130 x 45.2 mm) and semi-automated production process, the VARIUS NIR is optimized for real-time applications, ensuring fast data throughput and exceptional reliability across industries. For further information, see the VARIUS NIR Enhanced product page.
Avantes invites visitors to experience both systems live at Laser World of Photonics 2025. Meet the team for hands-on demonstrations, product insights and expert consultations. Avantes offers free feasibility studies and tailored advice to help you identify the optimal solution for your spectroscopy challenges.
- For more information, visit www.avantes.com or meet Avantes at booth #218 in Hall A3.
HydraHarp 500: a new era in time-correlated single-photon counting
Laser World of Photonics sees PicoQuant introduce its newest generation of event timer and time-correlated single-photon counting (TCSPC) unit – the HydraHarp 500. Setting a new standard in speed, precision and flexibility, the TCSPC unit is freely scalable with up to 16 independent channels and a common sync channel, which can also serve as an additional detection channel if no sync is required.

At the core of the HydraHarp 500 is its outstanding timing precision and accuracy, enabling precise photon timing measurements at exceptionally high data rates, even in demanding applications.
In addition to the scalable channel configuration, the HydraHarp 500 offers flexible trigger options to support a wide range of detectors, from single-photon avalanche diodes to superconducting nanowire single-photon detectors. Seamless integration is ensured through versatile interfaces such as USB 3.0 or an external FPGA interface for data transfer, while White Rabbit synchronization allows precise cross-device coordination for distributed setups.
The HydraHarp 500 is engineered for high-throughput applications, making it ideal for rapid, large-volume data acquisition. It offers 16+1 fully independent channels for true simultaneous multi-channel data recording and efficient data transfer via USB or the dedicated FPGA interface. Additionally, the HydraHarp 500 boasts industry-leading, extremely low dead-time per channel and no dead-time across channels, ensuring comprehensive datasets for precise statistical analysis.
The HydraHarp 500 is fully compatible with UniHarp, a sleek, powerful and intuitive graphical user interface. UniHarp revolutionizes the interaction with PicoQuant’s TCSPC and time tagging electronics, offering seamless access to advanced measurement modes like time trace, histogram, unfold, raw and correlation (including FCS and g²).
Step into the future of photonics and quantum research with the HydraHarp 500. Whether it’s achieving precise photon correlation measurements, ensuring reproducible results or integrating advanced setups, the HydraHarp 500 redefines what’s possible – offering precision, flexibility and efficiency combined with reliability and seamless integration to achieve breakthrough results.
For more information, visit www.picoquant.com or contact us at info@picoquant.com.
- Meet PicoQuant at booth #216 in Hall B2.
SmarAct showcases integrated, high-precision technologies
With a strong focus on turnkey, application-specific solutions, SmarAct offers nanometre-precise motion systems, measurement equipment and scalable micro-assembly platforms for photonics, quantum technologies, semiconductor manufacturing and materials research – whether in research laboratories or high-throughput production environments.

At Laser World of Photonics, SmarAct presents a new modular multi-axis positioning system for quantum computing applications and photonic integrated circuit (PIC) testing. The compact system is made entirely from titanium and features a central XY stage with integrated rotation, flanked by two XYZ modules – one equipped with a tip-tilt goniometer.
For cryogenic applications, the system can be equipped with cold plates and copper braids to provide a highly stable temperature environment, even at millikelvin levels. Thanks to its modularity, the platform can be reconfigured for tasks such as low-temperature scanning or NV centre characterization. When combined with SmarAct’s interferometric sensors, the system delivers unmatched accuracy and long-term stability under extreme conditions.
Also debuting is the SGF series of flexure-based goniometers – compact, zero-backlash rotation stages developed in collaboration with the University of Twente. Constructed entirely from non-ferromagnetic materials, the goniometers are ideal for quantum optics, electron and ion beam systems. Their precision has been validated in a research paper presented at EUSPEN 2023.
Targeting the evolving semiconductor and photonics markets, SmarAct’s optical assembly platforms enable nanometre-accurate alignment and integration of optical components. At their core is a modular high-performance toolkit for application-specific configurations, with the new SmarAct robot control software serving as the digital backbone. Key components include SMARPOD parallel kinematic platforms, long-travel SMARSHIFT electromagnetic linear stages and ultraprecise microgrippers – all seamlessly integrated to perform complex optical alignment tasks with maximum efficiency.
Highlights at Laser World of Photonics include a gantry-based assembly system developed for the active alignment of beam splitters and ferrules, and a compact, fully automated fibre array assembly system designed for multicore and polarization-maintaining fibres. Also on display are modular probing systems for fast, accurate and reliable alignment of fibres and optical elements – providing the positioning precision required for chip- and wafer-level testing of PICs prior to packaging. Finally, the microassembly platform P50 from SmarAct Automation offers a turnkey solution for automating critical micro-assembly tasks such as handling, alignment and joining of tiny components.
Whether you’re working on photonic chip packaging, quantum instrumentation, miniaturized medical systems or advanced semiconductor metrology, SmarAct invites researchers, engineers and decision-makers to experience next-generation positioning, automation and metrology solutions live in Munich.
- Visit SmarAct at booth #107 in Hall B2.
The post Laser World of Photonics showcases cutting-edge optical innovation appeared first on Physics World.
Liquid carbon reveals its secrets
Thanks to new experiments using the DIPOLE 100-X high-performance laser at the European X-ray Free Electron Laser (XFEL), an international collaboration of physicists has obtained the first detailed view of the microstructure of carbon in its liquid state. The work will help refine models of liquid carbon, enabling important insights into the role that it plays in the interior of ice giant planets like Uranus and Neptune, where liquid carbon exists in abundance. It could also inform the choice of ablator materials in future technologies such as nuclear fusion.
Carbon is the one of the most abundant elements on Earth and indeed the universe, but we still know very little about how it behaves in its liquid state. This is because producing liquid carbon is extremely difficult: at ambient pressures it sublimes rather than melts; and the liquid phase requires pressures of at least several hundred atmospheres to form. What is more, carbon boasts the highest melting temperature (of roughly 4500 °C) of all known materials under these high-pressure conditions, which means that there is no substance that can contain it for long enough to be studied and characterized.
In situ probing laser compression technique
There is an alternative, though, which involves using X-ray free electron laser pulses – such as those produced at the European XFEL – to transform solid carbon into a liquid for a few nanoseconds. The next challenge is to make measurements during this very short period of time. But this is exactly what a team led by Dominik Kraus of the University of Rostock and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has succeeded in doing.
In their work, Kraus and colleagues transiently created liquid carbon by driving strong compression waves into solid carbon samples using the pulsed high-energy laser DIPOLE 100-X, which is a new experimental platform at the European XFEL. In this way, the researchers were able to achieve pressures exceeding one million atmospheres, with the compression waves simultaneously heating the samples to around 7000 K to form liquid carbon. They then obtained in situ snapshots of the structure using ultrabright X-ray pulses at the European XFEL that lasted just 25 fs – that is, about 100,000 times shorter than the already very short lifetime of the liquid carbon samples.
Relevance to planetary interiors and inertial fusion
Studying liquid carbon is important for modelling the interior of planets such as the ice giants Neptune and Uranus, as well as the atmosphere of white dwarfs, in which it also exists, explains Kraus. The insights gleaned from the team’s experiments will help to clarify the role that liquid carbon plays in the ice giants and perhaps even comparable carbon-rich exoplanets.
Liquid carbon also forms as a transient state during some technical processes, like in the synthesis of carbon-based materials such as carbon nanotubes, nanodiamonds or “Q-carbon”, and may be key for the synthesis of new carbon materials, such as the long sought after (but still only predicted) “BC-8” structure. The team’s findings could also help inform the choice of materials for inertial fusion implosions aiming for clean and reliable energy production, where carbon is used as an ablator material.
“Because of its relevance in these areas, I had already tried to study liquid carbon during my doctoral work more than 10 years ago,” Kraus says. “Without an XFEL for characterization, I could only obtain a tiny hint of the liquid structure of carbon (and with large error bars) and was barely able to refine any existing models.”
Until now, however, this work was considered as being the best attempt to characterize the structure of liquid carbon at Mbar pressures, he tells Physics World. “Using the XFEL as a characterization tool and the subsequent analysis was incredibly simple in comparison to all the previous work and, in the end, the most important challenge was to get the European XFEL facility ready – something that I had already discussed more than 10 years ago too when the first plans were being made for studying matter under extreme conditions at such an installation.”
The results of the new study, which is detailed in Nature, prove that simple models cannot describe the liquid state of carbon very well, and that sophisticated atomistic simulations are required for predicting processes involving this material, he says.
Looking forward, the Rostock University and HZDR researchers now plan to extend their methodology to the liquid states of various other materials. “In particular, we will study mixtures of light elements that may exist in planetary interiors and the resulting chemistry at extreme conditions,” reveals Kraus. “This work may also be interesting for forming doped nanodiamonds or other phases with potential technological applications.”
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Starship destroyed in test stand explosion

A SpaceX Starship upper stage being prepared for the company’s next flight exploded June 19 during preparations for a static-fire test.
The post Starship destroyed in test stand explosion appeared first on SpaceNews.
Trump officially nominates Space Force Gen. Guetlein to lead ‘Golden Dome’

The nomination, submitted to the Senate Armed Services Committee, elevates Guetlein from his current role as vice chief of space operations
The post Trump officially nominates Space Force Gen. Guetlein to lead ‘Golden Dome’ appeared first on SpaceNews.
You May Think Animals Are More Human-Like Because of Your Social Life
Early Farming Societies Forged Bonds with Ancient Dogs in the Americas
Firefly announces commercial lunar imagery service

Firefly Aerospace says it plans to offer a commercial lunar imaging service for use by governments and companies, one that could supplement or replace an existing, but aging, NASA orbiter.
The post Firefly announces commercial lunar imagery service appeared first on SpaceNews.
Regulators clear Starlink-enabled texting trial in war-torn Ukraine

Local regulators have approved Ukrainian telco Kyivstar’s plans to start testing space-enabled texting services this summer using SpaceX’s Starlink constellation, targeting areas crippled by Russian strikes and other terrestrial coverage gaps.
The post Regulators clear Starlink-enabled texting trial in war-torn Ukraine appeared first on SpaceNews.
Discover the Handfish: A Bizarre Fish That Walks With Finger-Like Fins
The EPA Plans to ‘Reconsider’ Ban on Cancer-Causing Asbestos
White Sands' Footprints Confirmed as the Oldest Evidence of Humans in the Americas
‘Dragon Man’ skull belongs to mysterious human relative
U.S. National Academies adopts new business model to weather a financial storm
For the first time, women scientists win $1 million climate research prize
This giant, all-seeing telescope is set to revolutionize astronomy
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Science Magazine
- Updated: Trump administration unfreezes, then refreezes, NIH funding to Columbia University
Updated: Trump administration unfreezes, then refreezes, NIH funding to Columbia University
Will long-lasting HIV preventive be a game changer—or a missed opportunity?
Tiny laser delivers high-quality, narrowband light for metrology
A new solid-state laser can make a vast number of precise optical measurements each second, while sweeping across a broad range of optical wavelengths. Created by a team led by Qiang Lin at the University of Rochester in the US, the device can be fully integrated onto a single chip.
Optical metrology is a highly versatile technique that uses light to gather information about the physical properties of target objects. It involves illuminating a sample and measuring the results with great precision – using techniques such as interferometry and spectroscopy. In the 1960s, the introduction of lasers and the coherent light they emit boosted the technique to an unprecedented level of precision. This paved the way for advances ranging from optical clocks, to the detection of gravitational waves.
Yet despite the indispensable role they have played so far, lasers have also created a difficult challenge. To ensure the best possible precision, experimentalists much achieve very tight control over the wavelength, phase, polarization and other properties of the laser light. This is very difficult to do within the tiny solid-state laser diodes that are very useful in metrology.
Currently, the light from laser diodes is improved externally using optical modules. This added infrastructure is inherently bulky and it remains difficult to integrate the entire setup onto chip-scale components – which limits the development of small, fast lasers for metrology.
Two innovations
Lin and colleagues addressed this challenge by designing a new laser with two key components. One is a laser cavity that comprises a thin film of lithium niobate. Thanks to the Pockels effect, this material’s refractive index can vary depending on the strength of an applied electric field. This provides control over the wavelength of the light amplified by the cavity.
The other component is a distributed Bragg reflector (DBR), which is a structure containing periodic grooves that create alternating regions of refractive index. With the right spacing of these grooves, a DBR can strongly reflect light at a single, narrow linewidth, while scattering all other wavelengths. In previous studies, lasers were created by etching a DBR directly onto a lithium niobate film – but due to the material’s optical properties, this resulted in a broad linewidth.
“Instead, we developed an ‘extended DBR’ structure, where the Bragg grating is defined in a silica cladding,” explains team member Mingxiao Li at the University of California Santa Barbara. “This allowed for flexible control over the grating strength, via the thickness and etch depth of the cladding. It also leverages silica’s superior etchability to achieve low scattering strength, which is essential for narrow linewidth operation.”
Using a system of integrated electrodes, Lin’s team can adjust the strength of the electric field they applied to the lithium niobate film. This allows them to rapidly tune the wavelengths amplified by the cavity via the Pockels effect. In addition, they used a specially designed waveguide to control the phase of light passing into the cavity. This design enabled them to tune their laser over a broad range of wavelengths, without needing external correction modules to achieve narrow linewidths.
Narrowband performance
Altogether, the laser demonstrated an outstanding performance on a single chip – producing a clean, single wavelength with very little noise. Most importantly, the light had a linewidth of just 167 Hz – the smallest range achieved to date for a single-chip lithium niobate laser. This exceptional performance enabled the laser to rapidly sweep across a bandwidth of over 10 GHz – equivalent to scanning quintillions of points per second.
“These capabilities translated directly into successful applications,” Li describes. “The laser served as the core light source in a high-speed LIDAR system, measuring the velocity of a target 0.4 m away with better than 2 cm distance resolution. The system supports a velocity measurement as high as Earth’s orbital velocity – around 7.91 km/s – at 1 m.” Furthermore, Lin’s team were able to lock their laser’s frequency with a reference gas cell, integrated directly onto the same chip.
By eliminating the need for bulky control modules, the team’s design could now pave the way for the full miniaturization of optical metrology – with immediate benefits for technologies including optical clocks, quantum computers, self-driving vehicles, and many others.
“Beyond these, the laser’s core advantages – exceptional coherence, multifunctional control, and scalable fabrication – position it as a versatile platform for transformative advances in high-speed communications, ultra-precise frequency generation, and microwave photonics,” Lin says.
The new laser is described in Light: Science & Applications.
The post Tiny laser delivers high-quality, narrowband light for metrology appeared first on Physics World.