Spatial parametric characterization of general polychromatic light beams

The ABCD law and the M-2 factor are generalized for the propagation of general polychromatic light beams through first-order optical systems by introducing a generalized complex radius of curvature Q, an average wavelength <(lambda)over bar> and a characterization width W-C. The real part and the imaginary part of the parameter 1/Q are related to the effective radius of curvature and the characterization width W-C respectively. The characterization width W-C and the generalized M-2 factor are shown to be appropriate for describing the propagation capability and the beam quality of a general polychromatic light beam respectively. Moreover, the relation M-2 greater than or equal to 1 is deduced, a novel approach for interpreting the physical meaning of the effective radius of curvature is presented, and several special examples such as the polychromatic diffraction-limited light beams are analysed. (C) 1997 Elsevier Science B.V.