DYNAMIC AND NOISE PROPERTIES OF TUNABLE MULTIELECTRODE SEMICONDUCTOR-LASERS INCLUDING SPATIAL HOLE BURNING AND NONLINEAR GAIN

A general formalism based on the Green's function method is given for multielectrode semiconductor lasers. The effects of both spatial hole burning and nonlinear gain are included in this formalism. An effective nonlinear gain is introduced by taking into account the influence of the laser structure and the associated distribution of the mode intensity along the cavity length. The results obtained for Fabry-Perot and distributed feedback lasers show that the effective nonlinear gain could be considerably enhanced. Affected by the laser structure, the nonlinear gain has a different power dependence than expected from material considerations alone. By including this effective nonlinear gain, the frequency and intensity modulation properties of multielectrode semiconductor lasers are studied. A general linewidth expression is given which includes contributions from spontaneous emission and carrier shot noise. It is found that the effective alpha-factor affecting the linewidth is in general different from its counterpart affecting modulation and injection locking properties due to spatial hole burning and nonlinear gain. For lasers with uniform intensity distribution, the effective alpha-factor affecting the linewidth increases or remains constant with increasing output power depending on the model used for the nonlinear gain. For lambda/4 phase-shifted distributed feedback (DFB) lasers, the effective alpha-factor affecting the linewidth is slightly larger or smaller than that for uniform lasers depending on the value of the normalized grating coupling coefficient. The linewidth due to various contributions is calculated for both uniform intensity distributed lasers and phase-shifted DFB lasers.