Yoshihiro OHTSUKA, Satoshi TANAKA, Michiyuki KAMADA and Taiki KOBAYASHI

Department of Engineering Science, Faculty of Engineering, Hokkaido University, Sapporo, 060 Japan

(Received July 22, 1994; Accepted October 6, 1994)

This paper describes a change in optical spectrum on propagation in free space for a particular class of spatially partially coherent fields emanating from a polychromatic secondary source. A rectangular opening aperture in an opaque screen, illuminated with an extended incoherent polychromatic primary source, works as the secondary source. The spectral change is explored in detail theoretically and experimentally in association with spatial coherence in the secondary source as well as dispersive diffraction by the secondary source. The peak shift of the spectrum is associated with the coherence area for characterizing the secondary source. The peak shift becomes maximum if the secondary source is spatially coherent, but no shift occurs if the secondary source is spatially incoherent.

Key words : spectral change, polychromatic spatially partially coherent source, spatial coherence control, super-luminescent diode as a spectral source, red and blue shift of the spectrum, theory and experiments