Influence of aperture and bandwidth on fields of polychromatic laser

Fields of polychromatic laser passing through a hard edged aperture is derived and the influence of aperture and bandwidth on the fields is investigated. Transverse intensity of the polychromatic laser through aperture with different width has been illustrated by numerical calculation. It is shown that the spreading effect presents more obvious when the aperture width decreases and the bandwidth increases. Position of intensity peak increases when bandwidth increases but it increase rapidly from bandwidth 0 to 0.2 and slowly exceed 0.2. A physical explanation for the phenomenon that the position of peak intensity varies with bandwidth is also given.