TABLE OF CONTENTS The lumped-element circuit models of the laser diode described in the preceding sections have many advantages over analytical or numerical solutions of the rate equations. For example, driving circuits and electrical parasitics can easily be included into the laser models to achieve a more realistic simulation environment. Moreover, general purpose circuit simulators such as PSPICE are widely available, and in some advanced simulation software such as HP-MDS, automated optimisation is also available. However, the lumped-element circuit models of the laser diode only allow us to simulate the optical intensity or power envelope of the optical radiation. Therefore, phase information of the time-varying optical fields is lost and thus the optical spectrum (from the multimode circuit model of the laser diode) only consists of unrealistic longitudinal modes that are free from any phase noise. The lumped-element circuits are also based on average values of photon and carrier densities, thereby neglecting any inhomogeneous distribution along the laser cavity. In other words, there is no spatial correspondence between the circuit model and the physical device.
All these limitations can be overcome by using the distributed-element circuit model the transmission-line laser model (TLLM). In this case, the operating wavelength is much smaller than the device elements, and propagation effects can be taken into account. The basic construction of the TLLM was explained earlier in Chapter 14. Further comparisons between the lumped-element circuit model and the distributed-element TLLM are given in Table 15.2. In a...
