Analysis and design of coupled-cavity lasers - Part II: Transient analysis

The analysis and design of two-section and multisection coupled-cavity lasers is treated in two parts. In this second part, a numerical analysis of the transient behavior is given. The first part presented a formalism to derive wavelength-dependent threshold gains and device design criteria based thereon. Part II consists of two numerical approaches for the study of spurious mode suppression and general device behavior under pulsed current excitation. The first employs an approximate but useful multimode rate equation which incorporates all the coupled-cavity characteristics into the wavelength-dependent threshold gains derived in Part I. The importance of the design formulas in Part I is illustrated by showing the time-dependent spurious mode suppression as various device parameters are changed. Examples are given showing simulated AM and frequency shift keying (FSK) operation. In the second more rigorous approach, each of the two cavities is spatially subdivided into fine segments, and traveling wave rate-equations relate the complex amplitudes of the forward and backward propagating waves in each segment. This approach is not limited to certain regimes of device operation, but generally supports the simpler approach in most cases of interest. The conclusion is drawn that for realizable device geometries, with the proper device geometries and electrical device control, excellent spurious mode suppression (≳ 25 dB) should be readily attainable with coupled-cavity lasers.