TIME-DEPENDENT SIMULATION OF A LASER-MODULATOR COMBINATION

We present a computer model of an injection laser that is optically co upled to an on-chip electroabsorption modulator, The laser is assumed to be either of the distributed feedback type (DFB-laser) or of the ca vity type with one of the mirrors formed by a diffraction grating (DBR -laser). Due to residual reflections at the output of the modulator th ere is coupling between the modulator and the laser so that the electr ical signal that drives the modulator may affect the behavior of the l aser. The temporal evolution of the laser is described by the usual ra te equations which are solved numerically. At every step of the time i ntegration the light distribution and oscillation frequency of the las er-modulator combination are obtained as solutions of an eigenvalue eq uation. In this initial study the modulator is driven by a sinusoidal electrical signal, The performance of the device is judged by how much frequency modulation is introduced by the coupling between the laser and the modulator, We find that DFB lasers are slightly more susceptib le than DBR lasers to optical feedback between the modulator and the l aser, The permissible end-facet reflectivities depend on the requireme nts of the system into which the laser-modulator is to be incorporated . For a specific DFB and DBR lasers, Fig. 12 provides information rela ting length-bit rate products to permissible end-facet reflectivities.