Polarization Performances And Synchronization Performances Of VCSELs

Since 1960,a variety of different characteristics of the lasers have been created,vertical cavity surface emitting laser(VCSEL) is one of the most representative.VCSELs have wide potential applications in the areas of optical interconnects,optical communication,and other relevant fields owing to their desirable characteristics such as a low-threshold current,single-longitudinal-mode operation,circular output beam,and easy integration into two dimension arrays,and therefore have been paid much attention in recent years.Generally,typical VCSELs emit two perpendicular linear polarized lights along two crystallographic directions due to the weak cavity anisotropy.This unique property of the VCSEL can be exploited to create some novel applications and therefore has been studied theoretically and experimentally by many scholarst.In 1995,Miguel et al.proposed the well-known spin-flip model(SFM),which can be used to describe the polarization performances of VCSELs.In this paper,based on the framework of the spin-flip model(SFM) for GHz level modulation frequency,the polarization performances of current-modulated vertical-cavity surface-emitting lasers(VCSELs) subject to weak optical feedback have been theoretically investigated.The results show that,for typeⅠpolarization switching(PS),the influences of optical feedback intensity and the current modulation amplitude on the high-frequency modulation response is not obvious.For low-frequency modulation,optical feedback will result in the output of a VCSEL having rich dynamics.A new style PS can be obtained under large-signal modulation through adjusting the modulation frequency.For typeⅡPS the situation is more complex,and optical feedback increases the probability of polarization conversion and competition,while also affecting the PS point.The modulation amplitude also affects the output dynamics of the VCSEL.In addition,in this paper,based on the framework of the spin-flip model(SFM),the synchronization performances of two unidirectionally coupled vertical-cavity surface emitting lasers (VCSELs) subject to negative optoelectronic feedback has been theoretically investigated.The results show that,with the increase of the feedback intensity,the laser output power displays two different chaos regions,i.e.,Single polarized mode region and mixed mode region.The polarized mode in the single mode region can achieve a good synchronization,but sharply decline in the quality of synchronization close to the mixed mode region;within the mixed-mode region,the continuity and quality of synchronization of polarized modes are not ideal.The performance that the synchronization quality of the mixed mode is worse than that of the single mode,which is on the contrary compared with that reported on the scene of optical feedback.The reason may be due to that negative optoelectronic feedback has induced the competitive effects of the polarized modes.In addition,we have found that the inner parameters have a great impact on the selection of two.