We present results of a cleaved‐coupled‐cavity laser analysis which, in contrast to previous studies, incorporates all the following: (1) a model of the gain variation with pumping current and photon energy; (2) the refractive index dependence on the active region injection current; and (3) traveling wave equations for each laser segment. Based on this realistic formulation, we solve for the precise current required by one segment to attain threshold when the current in the other segment is specified for various gap spacings between the segments, and show that device behavior is very sensitive to that dimension. In addition, we calculate quantitatively the spectral tuning and previously unreported jumps from one extreme of the gain spectrum to the opposite extreme in particular current ranges.