光反馈诱发长波长垂直腔面发射激光器低功耗偏振开关

基于扩展的自旋反转模型,对光反馈诱发下长波长垂直腔面发射激光器中的低功耗偏振开关进行了理论研究.研究表明:长波长垂直腔面发射激光器在自由运行下未能获得的偏振开关现象,可以通过引入中等强度的偏振旋转光反馈来实现.对比强弱两种不同的线性色散效应,发现了一些有趣的现象:弱线性色散条件下更易于在低注入电流下获得偏振开关,并且产生偏振开关所需的反馈强度具有更大的调控范围;强色散效应中未能始终获得偏振开关,会出现两模共存区,并且偏振开关出现的注入电流值较高.同时,观察到的偏振模跳变和多偏振开关现象类似于短波长垂直腔面发射激光器,因而证实这两类激光器在偏振开关的本质规律上是相似的.此外,还对长波长垂直腔面发射激光器不易在低注入电流下获得偏振开关的原因进行了分析,并给出了合理的解释.

Polarization switching with low power consumption induced by optical feedback in long-wavelength vertical-cavity surface-emitting lasers

The polarization switching (PS) characteristics of vertical cavity surface emitting lasers(VCSELs) have received sustained attention for the past years. With the development of manufacturing technology, the performances of 1550 nm VCSELs have been improved, however the researches on the PS of 1550 nm VCSELs are relatively inadequate for the PS characteristics in the long-wavelength VCSELs may have wide application prospects in optical information processing and optical communications. In this paper, based on the extended spin-flip model (SFM), we theoretically investigate the PS with low power consumption induced by optical feedback in long-wavelength VCSELs. Results show that the PS, which is failed to realize in free-running long-wavelength VCSELs, can be achieved by introducing a moderate-strength polarization-rotation optical feedback. By comparing two different linear dispersion effects, some interesting phenomena have been found. For weak linear dispersion, the PS is relatively easy to realize for a low injection current level, and the range of feedback strength used to control the PS is wide. However, for strong dispersion effect, the PS cannot be obtained all the time since two mode-coexisting zones will appear, and the value of injection current where the PS happens is relatively high. Meanwhile, as observed in short-wavelength VCSELs, the polarization mode hopping and multiple PS have also been found in long-wavelength VCSELs, indicating that the physics nature thet induces the PS is similar for both long and short wavelength VCSELs. In addition, because the PS in long-wavelength VCSEL is more difficult to realize as compared with that in short-wavelength VCSELs, reasonable analyses and explanations may be as follows: since the linear dispersion effect in 1550 nm-VCSEL is much stronger than that of short wavelength VCSEL, the frequency difference between the two linear polarization modes is up to 60 GHz (or 0.48 nm), thus leading to the decrease of the correlation between two linear polarization modes. As a result, it is relatively difficult to obtain the PS phenomenon at low injection current level in long-wavelength VCSEL; while using suitable polarization-rotated optical feedback can partially compensate the deficiency of this correlation. We believe that the results obtained in this work will be helpful in investigation of low power consumption for all optical buffers by using long-wavelength VCSELs.