Nonlinear dynamics of vertical-cavity surface-emitting lasers

The dependence of the transient response of a vertical-cavity surface-emitt ing laser (VCSEL) on its aperture size is investigated subject to direct cu rrent modulation and external optical feedback. It is shown that lasers wit h small aperture size suppress higher order bifurcations and chaos even und er large-signal modulation and external optical feedback. Furthermore, the noise characteristics of VCSEL's under the influence of external optical fe edback are studied via the calculation of relative intensity noise. It is f ound that the level of external optical feedback for the onset of coherence collapse is high for devices with small aperture size. On the other hand, the small-signal response of lasers is also analyzed through the calculatio n of third-order harmonic distortion. It is shown that harmonic distortion is minimized in small devices. Therefore, VCSEL's with small aperture size have better immunity to irregular response under direct current modulation and external optical feedback.