Spectral anomalies of focused hollow Gaussian beams at the geometrical focal plane

On the basis of diffraction integral and the expansion of the hard-aperture function into a finite series of complex Gaussian functions, an approximate expression for spatially fully coherent polychromatic hollow Gaussian beams passing through aperture lens is obtained. Detailed numerical results indicate that remarkable spectral changes always occurs near the points where the field amplitude has zero value. The effects of truncation parameter, Fresnel number and the beam order on spectral shifts and spectral switches are investigated numerically. (C) 2008 Elsevier B.V. All rights reserved.

National Natural Science Foundation of China [10474004]; National Nature Science Foundation of China [60572002]; National Key Basic Research Program [2006CB921401]; DAAD exchange program [D/05/06972]; Projektbezogener Personenaustausch mit China (Germany/China joint Research Program)