Diffraction-induced spectral anomalies for information encoding and information hiding - Possibilities and limitations

It has been shown both theoretically and experimentally that drastic spectral changes take place around phase singularity and the shift in the spectral lines gives rise to the phenomenon called spectral switching. The shift of spectral lines towards the blue end or towards the red end of the spectrum might perhaps be used in free space communication applications. In more recent investigations, the possibility of information encoding with spectral anomalies have been discussed for two different optical systems. In this paper, we present schemes of information encoding and information hiding in the Airy pattern formed by diffraction of spatially coherent light after passing through a circular aperture. We propose a communication system that might be used to realize a new communication technique.