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Radiation mode

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(Redirected from Unbound mode)

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.

See also

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References

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  • Public Domain This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. (in support of MIL-STD-188).