Coming soon to a lab tabletop near you: a method of magneto-thermal imaging that offers nanoscale and picosecond resolution previously available only in synchrotron facilities.
This innovation in spatial and temporal resolution will give researchers extraordinary views into the magnetic properties of a range of materials, from metals to insulators, all from the comfort of their labs, potentially boosting the development of magnetic storage devices.
"Magnetic X-ray microscopy is a relatively rare bird," said Greg Fuchs, associate professor of applied and engineering physics, who led the project. "The magnetic microscopies that can do this sort of spatial and temporal resolution are very few and far between. Normally, you have to pick either spatial or temporal. You can't get them both. There's only about four or five places in the world that have that capability. So having the ability to do it on a tabletop is really enabling spin dynamics at nanoscale for research."
It's not exactly X-ray vision, but it's close. In research published in the journal Optica, University of California, Irvine researchers describe a new type of camera technology that, when aimed at an object, can rapidly retrieve 3D images, displaying its chemical content down to the micrometer scale. The new tech promises to help companies inspect things like the insides of computer chips without having to pry them open—an advancement the researchers say could accelerate the production time of such goods by more than a hundred times.
"This is a paper about a way to visualize things in 3D very fast, even at video rate," said Dmitry Fishman—director of laser spectroscopy labs in the UCI Department of Chemistry—who, along with Eric Potma, professor of chemistry, spearheaded the work. The novel imaging tech is based on a so-called nonlinear optical effect in silicon—a semiconductor material used in visible-light cameras and detectors.
Many substances around us, from table salt and sugar to most metals, are arranged into crystals. Because their molecules are laid out in an orderly, repetitive pattern, much is understood about their structure.
However, a far greater number of substances—including rubber, glass and most liquids—lack that fundamental order throughout, making it difficult to determine their molecular structure. To date, understanding of these amorphous substances has been based almost entirely on theoretical models and indirect experiments.
A UCLA-led research team is changing that. Using a method they developed to map atomic structure in three dimensions, the scientists have directly observed how atoms are packed in samples of amorphous materials. The findings, published today in Nature Materials, may force a rewrite of the conventional model and inform the design of future materials and devices using these substances.
"We believe this study is going to have a very important impact on the future understanding of amorphous solids and liquids—which are among the most abundant substances on Earth," said the study's senior author, Jianwei "John" Miao, a UCLA professor of physics and astronomy and a member of the California NanoSystems Institute at UCLA. "Understanding the fundamental structures may lead to dramatic advances in technology."
Vanderbilt and Penn State engineers have developed a novel approach to design and fabricate thin-film infrared light sources with near-arbitrary spectral output driven by heat, along with a machine learning methodology called inverse design that reduced the optimization time for these devices from weeks or months on a multi-core computer to a few minutes on a consumer-grade desktop.
The ability to develop inexpensive, efficient, designer infrared light sources could revolutionize molecular sensing technologies. Additional applications include free-space communications, infrared beacons for search and rescue, molecular sensors for monitoring industrial gases, environmental pollutants and toxins.
The research team's approach, detailed today in Nature Materials, uses simple thin-film deposition, one of the most mature nano-fabrication techniques, aided by key advances in materials and machine learning.
Standard thermal emitters, such as incandescent lightbulbs, generate broadband thermal radiation that restricts their use to simple applications. In contrast, lasers and light emitting diodes offer the narrow frequency emission desired for many applications but are typically too inefficient and/or expensive. That has directed research toward wavelength-selective thermal emitters to provide the narrow bandwidth of a laser or LED, but with the simple design of a thermal emitter. However, to date most thermal emitters with user-defined output spectra have required patterned nanostructures fabricated with high-cost, low-throughput methods.
The research team led by Joshua Caldwell, Vanderbilt associate professor of mechanical engineering, and Jon-Paul Maria, professor of materials science and engineering at Penn State, set out to conquer long-standing challenges and create a more efficient process. Their approach leverages the broad spectral tunability of the semiconductor cadmium oxide in concert with a one-dimensional photonic crystal fabricated with alternating layers of dielectrics referred to as a distributed Bragg reflector.
By merging two or more sources of light, interferometers create interference patterns that can provide remarkably detailed information about everything they illuminate, from a tiny flaw on a mirror, to the dispersion of pollutants in the atmosphere, to gravitational patterns in far reaches of the Universe.
"If you want to measure something with very high precision, you almost always use an optical interferometer, because light makes for a very precise ruler," says Jaime Cardenas, assistant professor of optics at the University of Rochester.
Now, the Cardenas Lab has created a way to make these optical workhorses even more useful and sensitive. Meiting Song, a Ph.D. student, has for the first time packaged an experimental way of amplifying interferometric signals—without a corresponding increase in extraneous, unwanted input, or "noise"—on a 1 mm by 1 mm integrated photonic chip. The breakthrough, described in Nature Communications, is based on a theory of weak value amplification with waveguides that was developed by Andrew Jordan, a professor of physics at Rochester, and students in his lab.
Biomedical engineers at Duke University have demonstrated a method for increasing the depth at which optical coherence tomography (OCT) can image structures beneath skin.
The gold standard for imaging and diagnosing diseases within the retina, OCT has yet to find widespread use as an imaging technique for other parts of the body due to its inability to return clear images from more than a millimeter beneath the skin's surface.
Duke researchers found that tilting the light source and detector used in the technique increases OCT's imaging depth by almost 50%, putting skin diagnoses within reach. The "dual-axis" approach opens new possibilities for OCT to be used in applications such as spotting skin cancer, assessing burn damage and healing progress, and guiding surgical procedures.
The results appear online on December 1 in the open access journal Biomedical Optics Express.
"It's actually a fairly simple technique that sounds like something out of Ghostbusters—you get more power when you cross the beams," said Adam Wax, professor of biomedical engineering at Duke. "Being able to use OCT even 2 or 3 millimeters into the skin is extremely useful because there are a lot of biological processes happening at that depth that can be indicative of diseases like skin cancer."
A new imaging technique, allowing 3D imaging at video rates through a fiber the width of a human hair, could transform imaging for a wide range of applications in industrial inspection and environmental monitoring. In the longer term the technique could be further developed for applications in medical imaging.
The system was developed by an international team of scientists led by the University of Glasgow's Optics Group. In a new paper published today in the journal Science, the team describe how they have been able to create video images from a single multimode optical fiber using a process known as time-of-flight 3D imaging.
Professor Miles Padgett, Royal Society research professor at the University of Glasgow and principal investigator for QuantIC, the UK Hub for Quantum Enhanced Imaging, said: "In applications like endoscopy and boroscopy imaging is traditionally achieved by using a bundle of optical fibers, one fiber for every pixel in the image, resulting in devices the thickness of a finger.
"As an alternative, we are developing a new technique for imaging through a single fiber the width of a human hair. Our ambition is to create a new generation of single-fiber imaging devices that can produce 3D images of remote scenes.
Optical interference is not only a fundamental phenomenon that has enabled new theories of light to be derived, but it has also been used in interferometry for the measurement of small displacements, refractive index changes, and surface irregularities. The Michelson interferometer is a commonly used interferometer, by which the equal-inclination and equal-thickness interference fringes of light can be easily observed. Historically, this interferometer has been used in many famous physical experiments, such as the Michelson-Morey experiment and gravitational wave detection.
In a new paper published in Light Science & Application, a team of scientists led by Professor Bao-Sen Shi and associate professor Zhi-Yuan Zhou from CAS Key Laboratory of Quantum Information, University of Science and Technology of China, has demonstrated a special equal-inclination interference by using non-monochromatic photons in a Michelson interferometer, manifested as the number of ring-like fringes increasing much more rapidly with increasing optical-path-difference (OPD) than the corresponding fringes for equal-inclination interference.
Researchers have developed an adaptive liquid lens based on a new electrically responsive fluid called dibutyl adipate (DBA) that changes focal length when a voltage is applied. The lens is lightweight, compact and simple to fabricate, which makes it ideal for mobile phone cameras, endoscopes, eyeglasses and machine vision applications.
"The human eye can arbitrarily focus on objects at different distances at incredibly fast speeds," said research team leader Miao Xu from Hefei University of Technology in China. "Inspired by this functionality, we developed an eye-like adaptive liquid lens that can be used to diverge or converge light by changing the shape of the DBA liquid."
In the Optica Publishing Group journal Optics Letters, the researchers describe their new DBA-based adaptive liquid lens, which weighs just a few grams, and show that it exhibits high optical performance with good stability. DBA's electronegative molecular structure allows an applied voltage to be used to rapidly change the lens's shape to modify its focal length. DBA is also transparent, non-volatile and inexpensive, making it ideal for use in adaptive liquid lenses.
