We develop a unified theory to analyze the modal properties of surface emitting chirped circular grating lasers. Based on
solving the resonance conditions which involve two types of reflectivities of chirped circular gratings, this theory is both
easy to understand and convenient to apply to different configurations of circular grating lasers. Though in a more
concise format, this approach is shown to be in agreement with previous derivations which use the characteristic
equations. With this unified analysis, the modal properties of circular DFB, disk-, and ring- Bragg resonator lasers are
obtained, and the threshold gains, single mode ranges, quality factors, emission efficiencies, and modal areas of these
types of circular grating lasers are compared.