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Optical devices create, guide, and detect electromagnetic waves and include lasers, telescopes, and solar cells. Most of the materials used in these devices are challenging for certain applications because of a phenomenon known as optical reciprocity, an inherent symmetry which forces light to travel bidirectionally. One example of an application-based challenge is a high-powered laser, where back-scattered light caused by optical reciprocity can damage the instrument.
A new study published in Nature Communications describes how optical reciprocity can be broken using insights from topological physics. Induced topological states, infusing the material with new properties, can help create "one-way" systems for light to travel, making it possible to create more efficient optical devices in the future. The research was led by Assistant Professor Bo Zhen and postdoc Li He in collaboration with Professor Eugene Mele and graduate students Zachariah Addison and Jicheng Jin, as well as Professor Steven Johnson from MIT.
Materials - Reciprocity - Effect - Materials - Systems
While there are some naturally existing materials that can break optical reciprocity, this magneto-optical effect is often very weak, and the materials can only be used in static systems. These limitations mean that the materials are too bulky to use on small optoelectronic chips. "It's a technical barrier that exists," says Zhen. "Besides this magneto-optical effect, we're asking what other scientific possibilities can implement similar effects."
Zhen and He studied LiNbO3, an optical material that can be made into thin films and could be used as a coating on optoelectronic chips and small devices. As a class of optical material that physicists refer to as nonlinear, LiNbO3 can break optical reciprocity when placed in a dynamic setting, such as being shaken instead of left standing still, or a static system.
Materials - Classroom - Laser - Pointers - Crystals
Nonlinear optical materials are quite common; most classroom laser pointers have nonlinear optical crystals that convert...
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