Experimental observation of the phenomenon of spectral switching for a class of partially coherent light

Experimental observations of the phenomenon of spectral switching are made for a class of partially coherent light incident on a circular aperture. The on-axis spectrum of the light in the far-field is different from the spectrum of the light at the aperture. It is shown that, depending on the value of the parameter a/L¯(ω) (a is the radius of the aperture and L¯(ω) is the effective correlation length of the light at the aperture at the central frequency ω₀ of the source spectrum), the spectral shift shows a gradual change but for a particular value of a/L¯(ω) the spectral shift exhibits a rapid transition and the phenomenon of spectral switching occurs. The generation of many spectral lines, from a single spectral line, in the far-field is also demonstrated