For an optical fiber or waveguide, a radiation mode or unbound mode is a mode which is not confined by the fiber core. Such a mode has fields that are transversely oscillatory everywhere external to the waveguide, and exists even at the limit of zero wavelength.
Specifically, a radiation mode is one for which
where β is the imaginary part of the axial propagation constant, integer l is the azimuthal index of the mode, n(r) is the refractive index at radius r, a is the core radius, and k is the free-space wave number, k = 2π/λ, where λ is the wavelength. Radiation modes correspond to refracted rays in the terminology of geometric optics.
Famous quotes containing the words radiation and/or mode:
“There are no accidents, only nature throwing her weight around. Even the bomb merely releases energy that nature has put there. Nuclear war would be just a spark in the grandeur of space. Nor can radiation “alter” nature: she will absorb it all. After the bomb, nature will pick up the cards we have spilled, shuffle them, and begin her game again.”
—Camille Paglia (b. 1947)
“The only mode of obtaining an answer to these questions of the senses is to forego all low curiosity, and, accepting the tide of being which floats us into the secret of nature, work and live, work and live, and all unawares the advancing soul has built and forged for itself a new condition, and the question and the answer are one.”
—Ralph Waldo Emerson (1803–1882)