Optics & Laser Technology 37 (2005) 438–443 Suppressingnonlineardynamicsinducedbyexternalopticalfeedback in vertical-cavity surface-emitting lasers X.F. Li à ,W.Pan,B.Luo,D.Ma,N.H.Li,Y.Wang School of Computer & Communication Engineering, Southwest Jiaotong University, Chengdu 610031, China Received 2 June 2004; accepted 4 July 2004 Available online 2 October 2004 Abstract Anumericalstudyofusingexternalopticalinjectiontosuppressthenonlineardynamicsintroducedbyexternalopticalfeedback in vertical-cavity surface-emitting lasers (VCSELs) has been undertaken. The model under consideration is a master–slave configuration where the master VCSEL provides the continuous wave to control the nonlinear behaviors arising in the slave VCSEL.Simulationresultsindicatethatthefeedback-inducednonlineardynamics(e.g.chaotic,single-periodic,andmulti-periodic oscillations),relativeintensitynoise(RIN)aswellasthecoherencecollapsecanbesuppressedeffectivelyaslongastheinjectionis strong enough to overcome the nonlinear effects of the feedback. r 2004 Elsevier Ltd. All rights reserved. Keywords: Nonlinear dynamics; VCSEL; Optical injection; Optical feedback; Bifurcation diagram; Relative intensity noise (RIN); Chaos 1. Introduction Over the past few years, vertical-cavity surface- emitting lasers (VCSELs) have received considerable attention because of their intrinsic advantages such as low threshold current, single-longitudinal-mode opera- tion, circular output beam, and wafer-scale integration [1–2]. Due to these attractive advantages, VCSELs are widely used in optical communications, information processes, and interconnects. In these applications, consideration must be given to the effects of external optical feedback on the device performance character- istics. It is demonstrated both theoretically and experi- mentallythatopticalfeedbackcaninducedetrimentalor beneficial effects, which depend on the level of the feedback [3–9].Fortheveryloworstrongfeedbackcase (regimes I, III, and V [3]), optical feedback can be used to purify the spectrum, reduce the operation threshold, and increase the side-mode suppression ratio (SMSR) [3,4]. For VCSELs, the reflectivity of distributed Bragg reflector (DBR) is so high (499%) that the device cannot operate at regime V. This indicates that increasing feedback strength to exceed a critical degree, VCSELs always operate at the so-called ‘‘coherence collapse’’ region (regime IV), where the linewidth is broadened dramatically and the intensity noise is enhancedgreatly [5–9].Tocombatthisunwantedeffect, various possible schemes have been proposed. Agrawal etal.haveputforward,fromthechaoscontrolpointof view,thatthefeedback-inducednonlineardynamicscan be suppressed through high-frequency injection (HFI) [10].Liuetal.havealsopointedoutthattheseunwanted instabilities can be stabilized by appending another external reflector [11].Tosumup,thebasicprincipleof these two methods is the same: introducing an addi- tional degree of freedom. In other words, for a given feedback level, the device working at nonlinear states can be driven into steady-state through optimizing the appended degree of freedom. However, most research has focused on edge-emitting lasers (EELs) and there has been little research on VCSELs. With the startling development of VCSELs, it is more necessary to investigate minutely on how to control the nonlinear ARTICLE IN PRESS www.elsevier.com/locate/optlastec 0030-3992/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlastec.2004.07.012 à Corresponding author. E-mail address: xfl79@163.com (X.F. Li).