Illustration of a photonic crystal, a material that can confine and direct light
J. Joannopoulous/SCIENCE PHOTO LIBRARY
Micrometer-sized devices that produce light by firing electron beams onto crystalline slabs could be used to build microparticle accelerators and X-ray machines. Such chip-sized devices can be manufactured faster, cheaper, and more compactly than current particle accelerators.
built by Yiyang His colleagues at the University of Hong Kong and the Massachusetts Institute of Technology, the new device consists of a special piece of silicon called a photonic crystal, a modified scanning electron microscope that shoots an electron beam onto it, and a device to detect it. It has been. gave off light. This setup takes advantage of the electromagnetic field that surrounds the electrons as they move, and can excite charged particles in nearby materials, in this case photonic crystals, to emit light.
From mathematical models, the researchers knew that the interaction between the crystal and electrons could be enhanced by adding patterns to the former, so they etched into it a grid of circular depressions, each about 100 nanometers wide. . Normally, light and electrons do not interact much, but by designing the energy and momentum of light to match the energy and momentum of electrons, an unusually large interaction between the two is possible. This matching method can ultimately boost the emission by up to a million times, says Yang.
That light has many potential uses, from spectroscopy to help scientists learn about the internal structure of various materials, to light-based communication.
In particular, it can be used to make small particle accelerators. Peter Hommelhoff at the University of Erlangen-Nuremberg, Germany. Instead of bombarding the particles with more common microwaves, researchers can use powerful light pulses to accelerate them, he says.
thomas kraus At the University of York in England, the new device could be a step not only to tiny particle accelerators, but also to smaller X-ray machines, says X-rays, which are basically too short in wavelength. Invisible waves of light. By matching the silicon patterns and electron velocities in the device, it may be possible to change the wavelength of the emitted light to X-rays.
“When you get a doctor to take an x-ray, it’s a big beast of a machine. Now you can imagine doing it with a tiny light source on a chip,” he says. It could make X-ray technology more accessible to medical facilities and portable for use by emergency first responders.
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