Spectral switches for a circular aperture with a variable wedge.

The far-field spectral anomalies of a short Gaussian pulse incident on a circular aperture with a variable wedge are theoretically studied, and some numerical examples are given to illustrate these effects. It is shown that some anomalous behaviors (such as red shift or blue shift for the spectral peak of the diffracted pulse) can be found under different conditions. Also, the important phenomenon called "spectral switches" is presented, which can be controlled by varying the angle of the wedge part in the circular aperture. Its potential application in information encoding and transmission for free-space communications is proposed, and this scheme has the benefit of easy implementation compared with other previous methods.