A Gas Made From Light Becomes Easier To Compress as You Squash It

Particles of light called photons can be trapped inside mirrors to form a gas with unusual properties, New Scientist reports. From the report: A gas made of particles of light, or photons, becomes easier to compress the more you squash it. This strange property could prove useful in making highly sensitive sensors. While gases are normally made from atoms or molecules, it is possible to create a gas of photons by trapping them with lasers. But a gas made this way doesn't have a uniform density -- researchers say it isn't homogeneous, or pure -- making it difficult to study properly. Now Julian Schmitt at the University of Bonn, Germany, and his colleagues have made a homogeneous photon gas for the first time by trapping photons between two nanoscale mirrors. They then moved one of the mirrors to measure the compressibility of the photon gas and derive basic properties about it. "We can consider the system to be like an air pump, but it's not filled with air, it's filled with light," says Schmitt. "We compress it and look at how it responds. In this way, we can learn about very fundamental properties." Journal reference: Science, DOI: 10.1126/science.abm2543.

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