Microscopy & Imaging News and Discussions

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Real-time molecular imaging of near-surface tissue using Raman spectroscopy
https://medicalxpress.com/news/2022-04- ... issue.html
by Thamarasee Jeewandara , Medical Xpress
Modern imaging modalities have facilitated a steady progress in medicine and treatment of diseases. Among them, Raman spectroscopy has gained attention for clinical applications as a label-free, non-invasive method to deliver a molecular fingerprint of a sample. Researchers can combine such methods with fiber optic-probes to allow easy-access to a patient's body. However, it is still challenging to acquire images with fiber optic probes. In a new report published in Nature Light: Science & Applications, Wei Yang and a team of scientists, at the Leibniz Institute of Photonic Technology in Germany, developed a fiber optic probe-based Raman imaging system to visualize real-time, molecular, virtual reality data and detect chemical boundaries.

The researchers developed the process around a computer-vision based positional tracking system with photometric stereo and augmented and mixed chemicals for molecular imaging and direct visualization of molecular boundaries of three-dimensional surfaces. The method provided an approach to image large tissue areas in a few minutes, to distinguish clinical tissue-boundaries in a range of biological samples.
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'Metalens' could disrupt vacuum UV market
https://phys.org/news/2022-05-metalens- ... um-uv.html
by Rice University
Rice University photonics researchers have created a potentially disruptive technology for the ultraviolet optics market.

By precisely etching hundreds of tiny triangles on the surface of a microscopic film of zinc oxide, nanophotonics pioneer Naomi Halas and colleagues created a "metalens" that transforms incoming long-wave UV (UV-A) into a focused output of vacuum UV (VUV) radiation. VUV is used in semiconductor manufacturing, photochemistry and materials science and has historically been costly to work with, in part because it is absorbed by almost all types of glass used to make conventional lenses.

"This work is particularly promising in light of recent demonstrations that chip manufacturers can scale up the production of metasurfaces with CMOS-compatible processes," said Halas, co-corresponding author of a metalens demonstration study published in Science Advances. "This is a fundamental study, but it clearly points to a new strategy for high-throughput manufacturing of compact VUV optical components and devices."

Halas' team showed its microscopic metalens could convert 394-nanometer UV into a focused output of 197-nanometer VUV. The disc-shaped metalens is a transparent sheet of zinc oxide that is thinner than a sheet of paper and just 45 millionths of a meter in diameter. In the demonstration, a 394-nanometer UV-A laser was shined at the back of the disc, and researchers measured the light that emerged from the other side.
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A zero-cost way to improve neutron scattering resolution by 500%
https://phys.org/news/2022-05-zero-cost ... ution.html
by Paul Boisvert, Oak Ridge National Laboratory

Scientists pushing the limits of the world's most advanced neutron scattering instruments know that a small amount of distortion in their measurements is inevitable. For some experiments, this distortion is easily accounted for, but in other types of research it can cause inaccurate findings.

Why does a small amount of distortion matter? It's similar to when a detective lifts a fingerprint from a glass of water. The curvature of the glass distorts the fingerprint slightly, making it difficult to match the print to a suspect's fingerprint on file. In such a case, it would be helpful if there was a way to remove the distortion from the fingerprint found on the glass.

Something like this occurred when scientists from Oak Ridge National Laboratory (ORNL) used the world-class SEQUOIA neutron scattering spectrometer at ORNL's Spallation Neutron Source (SNS). The researchers were measuring spin wave dispersions from a magnetic crystalline material. They discovered that the data (the fingerprint) obtained from SEQUOIA (the glass) was slightly distorted by the resolution limits of the instrument, despite its state-of-the-art design.
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Light traveling in a distorting medium can appear undistorted
https://phys.org/news/2022-06-distortin ... orted.html
by Wits University
A team led by researchers at the University of the Witwatersrand in Johannesburg, South Africa, with collaborators from the University of Pretoria (South Africa), as well as Mexico and Scotland, have made a new discovery on how light behaves in complex media, media that tends to distort light significantly. They demonstrated that "distortion" is a matter of perspective, outlining a simple rule that applies to all light and a vast array of media, including underwater, optical fiber, transmission in the atmosphere and even through living biological samples.

Their novel quantum approach to the problem resolves a standing debate on whether some forms of light are robust or not, correcting some misconceptions in the community. Importantly, the work outlines that all light has a property that remains unchanged, an insight that holds the key to unraveling the rest of the perceived distortion. To validate the finding, the team showed robust transport through otherwise highly distorting systems, using the outcome for error-free communication through noisy channels.
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New single-mode semiconductor laser delivers power with scalability
https://phys.org/news/2022-06-single-mo ... ility.html
by University of California - Berkeley
Berkeley engineers have created a new type of semiconductor laser that accomplishes an elusive goal in the field of optics: the ability to maintain a single mode of emitted light while maintaining the ability to scale up in size and power. It is an achievement that means size does not have to come at the expense of coherence, enabling lasers to be more powerful and to cover longer distances for many applications.

A research team led by Boubacar Kanté, Chenming Hu Associate Professor in UC Berkeley's Department of Electrical Engineering and Computer Sciences (EECS) and faculty scientist at the Materials Sciences Division of the Lawrence Berkeley National Laboratory (Berkeley Lab), showed that a semiconductor membrane perforated with evenly spaced and same-sized holes functioned as a perfect scalable laser cavity. They demonstrated that the laser emits a consistent, single wavelength, regardless of the size of the cavity.

The researchers described their invention, dubbed Berkeley Surface Emitting Lasers (BerkSELs), in a study published Wednesday, June 29, in the journal Nature.

"Increasing both size and power of a single-mode laser has been a challenge in optics since the first laser was built in 1960," said Kanté. "Six decades later, we show that it is possible to achieve both these qualities in a laser. I consider this the most important paper my group has published to date."
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World's first self-calibrated photonic chip: An interchange for optical data superhighways
https://phys.org/news/2022-07-world-sel ... hange.html
by Monash University
Research led by Monash and RMIT Universities in Melbourne has found a way to create an advanced photonic integrated circuit that builds bridges between data superhighways, revolutionizing the connectivity of current optical chips and replacing bulky 3D-optics with a wafer thin slice of silicon.

This development, published in the journal Nature Photonics, has the ability to warp-speed the global advancement of artificial intelligence and offers significant real world applications such as:

Safer driverless cars capable of instantly interpreting their surroundings
Enabling AI to more rapidly diagnose medical conditions
Making natural language processing even faster for apps such as Google Homes, Alexa and Siri
Smaller switches for reconfiguring optical networks that carry our internet to get data where it's needed faster
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A new way of fabricating high-efficiency diffraction gratings for astronomical spectroscopy
https://phys.org/news/2022-11-fabricati ... scopy.html
by SPIE
Today, astronomers seek to observe the faintest and most distant objects possible. Extremely Large Telescopes (ELTs), with apertures in the order of several dozen meters, are the next generation facilities to do so. However, building larger telescopes is only one part of the equation. The other part is the capability of detecting the gathered photons in the most efficient way possible.

This is where making all other optical components in astronomical instruments more efficient becomes crucial. One essential component used in modern astronomical science is the diffraction grating. Its role is to spatially spread incoming light into its constituent frequencies, similar to how a glass prism does.

Thanks to a precisely engineered structure that leverages the wave-like nature of photons, diffraction gratings can separate light of different wavelengths with very high resolution. When coupled with a telescope and a spectrometer, gratings allow scientists to analyze the spectral properties of celestial bodies.

Motivated by the somewhat stagnant progress made in grating technology over the past decade, researchers Hanshin Lee of the University of Texas at Austin and Menelaos K. Poutous of the University of North Carolina at Charlotte, focused on a completely different way of fabricating diffraction gratings.

In their paper recently published in the Journal of Astronomical Telescopes, Instruments, and Systems, they report their success on manufacturing proof-of-concept high-efficiency diffraction gratings using reactive ion-plasma etching (RIPLE), a plasma-based manufacturing technology normally used for semiconductors.
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New photoacoustic microscopy technique achieves depth of field nearly 14 times greater than previous technology
https://medicalxpress.com/news/2022-12- ... field.html
by Emily Velasco, California Institute of Technology

Photoacoustic microscopy (PAM) is a relatively new imaging technique that uses laser light to induce ultrasonic vibrations in tissue. These ultrasonic vibrations, along with a computer that processes them, can then be used to create an image of the structures of the tissue in much the same way ultrasound imaging works.

In the last few years, Lihong Wang, Caltech's Bren Professor of Medical Engineering and Electrical Engineering, has developed PAM technologies that can image changing blood flow in the brain, detect cancerous tissue, and even identify individual cancer cells.

However, one limitation of high-resolution (i.e., optical-resolution) PAM has been its narrow depth of field, meaning that it can only focus on a thin layer (approximately 30 micrometers, or about the length of one skin cell, with one to two micrometers of resolution) of tissue at a time. To see something above or below the plane that the device is viewing, it needs to refocus above or below that plane. For comparison, imagine a person putting on reading glasses to do a crossword puzzle.
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Ultrafast control of spins in a microscope
https://phys.org/news/2023-01-ultrafast-microscope.html
by Nik Papageorgiou, Ecole Polytechnique Federale de Lausanne
Researchers at EPFL have developed a new technique that can visualize and control the rotation of a handful of spins arranged in a vortex-like texture at the fastest speed ever achieved. The breakthrough can advance "spintronics," a technology that includes new types of computer memory, logic gates, and high-precision sensors.

"Technological advancements in computation, data storage and sensing all require new techniques to control the nanoscaled magnetic properties of materials," says Professor Fabrizio Carbone at EPFL's School of Basic Sciences. One of these properties is "spin," which refers to the magnetic orientation of individual atoms.

Spin has attracted a lot of interest in recent years, giving rise to the field of spin electronics or "spintronics." Apart from the fundamental study of spin, the more practical aim of spintronics is to exploit not just the charge of electrons—as in traditional electronics—but also their spin, adding and extra degree of freedom that can improve the efficiency of data storage and transfer.

However, this first requires that we can control small numbers of spins. "The visualization and deterministic control of very few spins has not yet been achieved at the ultrafast timescales," says Dr. Phoebe Tengdin, a postdoc in Carbone's lab, pointing out the very tight timeframes that this control needs to happen for spintronics to ever make the leap into applications.

Now, Tengdin along with Ph.D. student Benoit Truc and fellow postdoc Dr. Alexey Sapozhnik have developed a new technique that can visualize and control the rotation of a handful of spins arranged in a vortex-like texture, a kind of spin "nano-whirlpool" called a skyrmion.

To do this, the scientists used sequences of laser pulses at a femtosecond timeframe (10-15 or a quadrillionth of a second). By arranging the laser pulses apart just right, they were able to control the rotation of spins in a selenium-copper mineral known in the field by its chemical composition, Cu2OSeO3. The mineral is quite popular in the field of spintronics, as it provides an ideal testbed for studying spins.

Controlling the spins with laser pulses, the researchers found that they could even switch their orientation at will by simply changing the delay time between successive driving pulses and adjusting the laser polarization.
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Researchers devise new membrane mirrors for large space-based telescopes
https://phys.org/news/2023-04-membrane- ... copes.html
by Optica
Researchers have developed a new way to produce and shape large, high-quality mirrors that are much thinner than the primary mirrors previously used for telescopes deployed in space. The resulting mirrors are flexible enough to be rolled up and stored compactly inside a launch vehicle.

"Launching and deploying space telescopes is a complicated and costly procedure," said Sebastian Rabien from Max Planck Institute for Extraterrestrial Physics in Germany. "This new approach—which is very different from typical mirror production and polishing procedures—could help solve weight and packaging issues for telescope mirrors, enabling much larger, and thus more sensitive, telescopes to be placed in orbit."

In the journal Applied Optics, Rabien reports successful fabrication of parabolic membrane mirror prototypes up to 30 cm in diameter. These mirrors, which could be scaled up to the sizes needed in space telescopes, were created by using chemical vapor deposition to grow membrane mirrors on a rotating liquid inside a vacuum chamber. He also developed a method that uses heat to adaptively correct imperfections that might occur after the mirror is unfolded.

"Although this work only demonstrated the feasibility of the methods, it lays the groundwork for larger packable mirror systems that are less expensive," said Rabien. "It could make lightweight mirrors that are 15 or 20 meters in diameter a reality, enabling space-based telescopes that are orders of magnitude more sensitive than ones currently deployed or being planned."
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