Experimental observation of spectral switch of partially coherent light focused by a lens with chromatic aberration

In this paper, the effects of chromatic aberration of a focusing lens on the normalized spectrum of the partially coherent light at the geometrical-image plane are investigated experimentally. The experimental results show that, compared to the source spectrum, the normalized spectrum of the partially coherent light at the geometrical-image plane shifts either towards the red side or towards the blue side, which is dependent on the position of the observation point. In particular, the normalized spectrum splits into two peaks at some points and the spectral switch occurs at the critical point. Furthermore, each of the two peaks of the normalized spectrum still split into two subpeaks respectively at some points and the spectral switch occurred in the short-wavelength range of the normalized spectrum is also observed at another critical point.