Optical microsphere

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Optical microspheres, also known as photonic atoms, are tiny glass spheres that trap light. They are a type of optical microresonator or microcavity. Light can circulate inside them for a long time, giving a very high quality factor (Q), up to about 10^11. Because of this strong light confinement, microspheres are used in many photonic applications, including microlaser cavities, optical filters, sensors, and other experiments that require precise control of light in a small structure.