  We consider design optimization of passively mode-locked two-section
semiconductor lasers that incorporate intracavity grating spectral filters. Our
goal is to develop a method for finding the optimal wavelength location for the
filter in order to maximize the region of stable mode-locking as a function of
drive current and reverse bias in the absorber section. In order to account for
material dispersion in the two sections of the laser, we use analytic
approximations for the gain and absorption as a function of carrier density and
frequency. Fits to measured gain and absorption curves then provide inputs for
numerical simulations based on a large signal accurate delay-differential model
of the mode-locked laser. We show how a unique set of model parameters for each
value of the drive current and reverse bias voltage can be selected based on
the variation of the net gain along branches of steady-state solutions of the
model. We demonstrate the validity of this approach by demonstrating
qualitative agreement between numerical simulations and the measured
current-voltage phase-space of a two-section Fabry-Perot laser. We then show
how to adapt this method to determine an optimum location for the spectral
filter in a notional device with the same material composition, based on the
targeted locking range, and accounting for the modal selectivity of the filter.
