We study the spectral property of a composite field superposed by a polychromatic Gaussian beam and a polychromatic Gaussian beam with an embedded mth-order vortex. It is shown that, in the overall spectral shift distribution, there exist m small areas where sharp spectral anomaly takes place, similarly and respectively, which are related with the ratio of the respective amplitudes of the two composite beams and the relative phase between them. Detailed investigation reveals that, for each small area, there exists a “main line”, along which spectral switch can be observed.
© 2014 Optical Society of America
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