Discover Top Posts Tagged with #refractive index

Silicon nitride-based electromagnetic metamaterial with industrial potential developed

Electromagnetic metamaterials with negative physical parameters such as negative dielectric constant and negative magnetic permeability have attracted widespread attention in the academic community. In 2010, they were praised by Materials Today as one of the top ten advances in materials science in the past 50 years. Different from traditional electromagnetic materials, they exhibit negative refractive index, perfect imaging and super absorption, and are widely used in optical stealth, wireless communication, electromagnetic wave absorption and shielding. Introducing randomly distributed carbon or metal conductive phases into insulating matrix is one of the important methods for preparing metamaterials.

Clear as MAX

To really understand the complexity of our tissues, you need to peel back the layers to see what’s happening on the inside. 3D imaging allows researchers to do this while keeping tissues perfectly intact. However, to get the clearest images, tissues must first be made transparent using a laborious process called tissue clearing. In a bid to simplify this process, researchers focused on one crucial stage that usually involves multiple steps – changing the tissue's refractive index, that is, how it bends light. The team developed a new recipe for the solution into which tissues are placed during the clearing process. This solution, called MAX, allowed the refractive index to be changed in one simple step. MAX was successfully tested on tissues from humans, mice, rats, chickens and zebrafish, as pictured here using fluorescence microscopy of the blood vessels (red) and neurons (green) of a whole mouse brain.

Written by Lux Fatimathas

Image from work by Boram Lee and colleagues

Department of Anatomy, Brain Korea 21 Plus Program for Biomedical Science, Korea

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Scientific Reports, November 2022

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#science #biomedicine #tissue clearing #immunofluorescence #refractive index #fluorescence microscopy #neurons #brains #neuroscience

Double Refraction This is a crystal of the mineral calcite, a mineral with an extremely high birefringence. Birefringence is a property of how some transparent materials interact with light. A birefringent crystal like calcite has one direction where light moves rapidly through the crystal and another direction where light moves more slowly. When a beam of light enters a crystal of calcite, it splits into 2 separate rays, each vibrating (or polarized) in a different direction. When light moves into a crystal from the air, it refracts or bends, and the path it takes depends on how fast it moves. In other words, light enters a crystal of calcite and splits into 2 different beams. The light coming in from behind this crystal started as a single beam, but as it entered the calcite it split into 2 separate rays, each taking a different path through the crystal. When the light exits the crystal to head towards your eyes, each ray exits at a different point, so the image that you see behind the crystal is duplicated when the light comes out. -JBB Image credit: https://flic.kr/p/22SFK4v Read more: http://bit.ly/2P1NIWO

#Science #calcite #light #refraction #double refraction #birefringence #icelandic spar #sunstone #physics #refractive index #the earth story

Cross polarized Acetaminophen photographed at 3X.

#acetaminophen #cross polarization #birefringence #refractive index #stress #chem lab #high mag photo #polarized #photographers on tumblr #original photographers

Novel gel proves itself to be a highly tunable color filter

Color these scientists happy. An exotic gel they studied at the National Institute of Standards and Technology (NIST) has an unexpected property: The material's temperature determines which color of light can pass through it.

The material, which the research team calls "SeedGel," already has shown promise as a multipurpose tool, with applications ranging from batteries to water filters to tissue engineering. The team's new paper, appearing in Nature Communications, highlights the gel's newfound capability as a temperature-sensitive light filter. Shine white light at the gel, and depending on the gel's temperature, only a specific wavelength, or color, will pass through it. A temperature change of less than a tenth of a degree Celsius can be enough to alter the permitted wavelength, which can be any color in the visible range as well as parts of the ultraviolet and infrared.

"Our previous work showed that the SeedGel can transform from clear to opaque and back again, but we did not explore what it can do with color," said Yun Liu, who is both a scientist at the NIST Center for Neutron Research (NCNR) and a professor at the University of Delaware. "Its ability to control color precisely was a new discovery."

Zero-index metamaterials offer new insights into the foundations of quantum mechanics

In physics, as in life, it's always good to look at things from different perspectives.

Since the beginning of quantum physics, how light moves and interacts with matter around it has mostly been described and understood mathematically through the lens of its energy. In 1900, Max Planck used energy to explain how light is emitted by heated objects, a seminal study in the foundation of quantum mechanics. In 1905, Albert Einstein used energy when he introduced the concept of photon.

But light has another equally important quality, known as momentum. And as it turns out, when you take momentum away, light starts behaving in really interesting ways.

An international team of physicists led by Michaël Lobet, a research associate at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Eric Mazur, the Balkanski Professor of Physics and Applied Physics at SEAS, are re-examining the foundations of quantum physics from the perspective of momentum and exploring what happens when the momentum of light is reduced to zero.

The research is published in Nature Light: Science & Applications.

Side-polished SMS-based RI sensor employing perfluorinated POF

In a new publication from Opto-Electronic Advances, Xuezhi Zhang, Boyue Yang, Junfeng Jiang, Kun Liu, Xiaojun Fan, Zhaozhu Liu, Min Peng, Guanlong Chen and Tiegen Liu from Tianjin University, Tianjin, China discuss a side-polished SMS based RI sensor employing perfluorinated POF.

Refractive index is an inherent property of material, which can reflect the concentration, purity and other important information about a material under certain conditions. When the external refractive index changes, some parameters (amplitude, wavelength, intensity, etc.) in the optical fiber will change accordingly. The change of refractive index can be calculated by the change of the parameters mentioned above. Refractive index sensors are widely used in chemical analysis, environmental pollution monitoring, medical diagnosis, food detection and other fields.

Polymer optical fiber has been used in optical fiber sensing, Internet of things, lighting systems and other fields. Compared with SiO2 optical fiber, polymer optical fiber has many advantages, such as light weight, high flexibility, strong plasticity and so on. In recent years, polymer materials have developed rapidly, and there is great potential to improve the material characteristics and fabrication processes. Some research groups have already begun to study and apply polymer optical fiber. In the field of optical fiber sensing, polymer optical fiber has the potential to replace SiO2 optical fiber in some areas, which has a high value and potential for wide application.

3-D-printed glass enhances optical design flexibility

Lawrence Livermore National Laboratory (LLNL) researchers have used multi-material 3-D printing to create tailored gradient refractive index glass optics that could make for better military specialized eyewear and virtual reality goggles.

The new technique could achieve a variety of conventional and unconventional optical functions in a flat glass component (with no surface curvature), offering new optical design versatility in environmentally stable glass materials.

The team was able to tailor the gradient in the material compositions by actively controlling the ratio of two different glass-forming pastes or "inks" blended together inline using the direct ink writing (DIW) method of 3-D printing. After the composition-varying optical preform is built using DIW, it is then densified to glass and can be finished using conventional optical polishing.

"The change in material composition leads to a change in refractive index once we convert it to glass," said LLNL scientist Rebecca Dylla-Spears, lead author of a paper appearing today in Science Advances.

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