Abstract

The recent rapid advances in performance of vertical cavity surface emitting lasers (VCSELs) have permitted consideration to be given to novel applications of such devices in, for example, optical data links and two-dimensional optical switching. In such applications consideration must be given to the effects of optical feedback on device operating characteristics. The transverse mode structure of stand-alone VCSELs has been studied quite extensively but modifications of that mode structure due to optical feedback have received rather less attention. This contributing reports a theoretical study which has been performed of the multi mode dynamics and steady state transverse mode selection in Vertical Cavity Surface Emitting Lasers (VCSELs) subject to weak optical feedback in an external cavity configuration. Attention is focused on the competition between the two lowest order models (LP_o, and LP,) appropriate to circularly symmetric VCSEL structures. It is shown that preferential excitation of either mode can be effected by appropriate choice of optical feedback delay. Opportunities for enhancing modal discrimination by adjusting the strength of optical feedback are also presented. The model utilised in the work reported here incorporates both spatial dependence of carrier and optical field profiles and time delay effects associated with weak optical feedback. In the former respect the model is seen as an extension of earlier work on VCSEL transverse mode dynamics [1-3] whilst the incorporation of optical feedback using the Lang-Kobayashi equations makes contact with complementary work on edge emitting lasers [4-6].

© 1996 Optical Society of America