LOCKING CONDITIONS AND STABILITY PROPERTIES FOR A SEMICONDUCTOR LASER WITH EXTERNAL LIGHT INJECTION.

Abstract

A theoretical and experimental investigation of injection locking of semiconductor lasers is presented. The theory is based on three coupled rate equations for the field amplitude and phase and the carrier density of a laser with external CW light injection. The theoretical analysis takes into account the dependence of refractive index on the carrier density, expressed by the linewidth enhancement factor alpha . Locking conditions and dynamic stability are analyzed. The nonzero value of alpha results in an increased locking bandwidth, where only part of the range corresponds to a dynamically stable state. Asymmetric characteristics are obtained for the locked power and phase as a function of frequency detuning between the master and slave laser. Outside the stable range, light injection gives rise to beat phenomena and intensity pulsations. The theoretical results were confirmed by experiments on 830 nm CSP lasers and 1. 3 mu m BH lasers. The experiments include the first measurements of locking bandwidth characteristics reported for 1. 3 mu m lasers. Power spectra are recorded under locked and near-locked conditions and compared with theory. The 1. 3 mu m lasers are found to have a better dynamic stability than 830 nm lasers.