First of all, it should be explained what we mean by circulating light. The circulating light is the light wave that can be considered as a particular case of the more general wave of whispering gallery type. It is known that a faint sound can be heard in a round room if the source and receiver of the sound are located near the round wall and the sound in the form of a sound wave propagates along the wall with a minimal decrease in the energy density (wave intensity) This is due to the fact that the volume occupied by the wave does not increase in this case, unlike a conventional sound wave, the volume of which increases in proportion to the square of the distance from the sound source. As a result, the energy density of the conventional sound wave and therefore its intensity decreases in inverse proportion with square of the distance. Note that the whispering gallery sound wave contains a frequency spectrum that is perceived by the receiver without distortion. Whispering gallery light waves are used also in optics. Usually, the light wave propagates along the surface of a glass ball. The role of the wall in this case plays the free space surrounding the ball. The wave is reflected from the boundary between the glass and the surrounding space due to the phenomenon of total internal reflection. Such balls have found application in the form of optical resonators for separating the WDM optical signal to direct signals of different wavelengths into different separate channels.
Torchigin V. P. (Wed,) studied this question.
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