The tremendous growth of Internet traffic has created increasing demand on high capacity optical communications networks. Dense wavelength division multiplexing (DWDM) networks has emerged as a very attractive option. Systems for optical wavelength demultiplexing have generated much interest in research and development. Since its first appearance, the Arrayed Waveguide Grating (AWG) has become the mainstay for the high channel count demultiplexing applications. In classical AWG design, the number of wavelength channels to be resolved is directly limited by the Free Spectral Range (FSR), and ultimately the channel count of an AWG is limited by the number of arrayed waveguides that could be fit on the substrate on which the AWG is fabricated. The harmonic images generated outside the FSR limit additional channels beyond FSR. In this work, a novel array waveguide grating (AWG) design method is proposed to achieve large channel count in a single stage. The Method of Irregularly Sampled Zero Crossings (MISZC) with a spherical wave applies non-periodic/irregular placement of apertures of the grating structure combined with holographic techniques based on zero crossings with a virtual spherical reference wave. As a result, the restriction of free spectral range (FSR) for the regular AWG is eliminated. Thus, high channel count (>500) can be achieved in a single stage with reasonable noise level. Theoretical derivation and analysis of MISZC is presented. Detailed simulations using BeamPROP™ and Matlab™ tools are reported to show good agreement with the theory and analysis.