Posted in | Laser

Researchers Create Holographic Images of Free-Flowing Air Particles

A recent Kansas State University study states that holographic images of free-flowing air particles may help climate change and biological weapons watchdogs to improve the monitoring of the atmosphere.

Two overlapping lasers are helping Kansas State University physics researchers create holographic images of free-flowing air particles, which may help climate scientists and biological weapons watchdogs monitor what's in the air. Credit: Kansas State University

Matthew Berg, Key Investigator and Associate Professor of Physics, said the study, featured in Nature's Scientific Reports, is key to understanding the aerosol composition of Earth's atmosphere.

We have these small little chunks of particles floating around in the air and people want to know what they are made of, but if we disrupt them, it might change their form. Until now, there hasn't been any unique and confident way to confirm particle size and shape properties in their natural form. We have solved the inverse problem.

Matthew Berg, Key Investigator and Associate Professor of Physics, Kansas State University

Berg, referring to a problem that is worked backward from results to cause, said prior to this study, the inverse problem with aerosol particles was greatly educated guesswork based on mathematical calculations. Researchers were not able to objectively define free-floating aerosol particles as merely capturing a particle and observing it under a microscope could change its physical size and shape. Now, they are able to bounce light waves off the particle and then measure the deflection.

The method that has been detailed in the publication takes holographic images of particles as they float through the air by using two overlapping lasers: one green and one red. The green laser is the standard method that can be employed for measuring the light deflection; by providing the red laser, they also obtain a 3D image that has the potential to subjectively account for a wide range of particle shapes.

We get the two properties — size and shape — that we've always wanted to get. We still have all the advantages that people had with the last 50 years — light scattering, contact free and measurements can be done rapidly — and then we can put it on an instrument and fly it around in the air.

Matthew Berg, Key Investigator and Associate Professor of Physics, Kansas State University

Berg is presently working to put the laser setup on an unmanned aircraft in order to measure free-flowing aerosol particles in the atmosphere. Berg said that the particle form can change by removing the particles from their natural environment. For instance, if the particles are frozen in the atmosphere and Scientists gather them to bring them back to the ground in order to study, the particles are likely to melt and change their sizes and shapes.

If we think about climate science, they want to know the size and shape of particles floating in the atmosphere. This information can help climate scientists account for how much sunlight those particles scatter back into space or absorb — and if they absorb, by how much will it heat up the surrounding atmosphere.

Matthew Berg, Key Investigator and Associate Professor of Physics, Kansas State University

The National Science Foundation funds this research through Berg's CAREER award and support is also provided by the Army Research Office for its capability of monitoring for biological weapons like anthrax.

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