连续可变偏振光注入垂直腔面发射激光器的偏振开关及双稳特性

Characteristics of Polarization Switching and Bistability in Vertical-Cavity Surface-Emitting Laser Subject to Continuous Variable-Polarization Optical Injection

基于垂直腔面发射激光器(VCSELs)的自旋反转模型(SFM),理论研究了连续可变偏振光注入VCSEL所产生的偏振开关及双稳特性。研究结果表明,在合适的注入参数设置下,通过连续正向扫描和反向扫描注入光偏振角,VCSEL的偏振分量可产生由偏振角度诱导产生的偏振开关(PS)及偏振双稳(PB)效应,且正反向PS点位置随扫描周期的变化而发生偏移,进而导致PB区域宽度发生改变。当注入强度一定时,正反向PS点位置随扫描周期的增大呈现相反的变化趋势,且更小的扫描周期和更大的频率失谐均有助于增加PB区域的宽度;对于频率失谐给定的情形,注入光强度的变化对PS和PB宽度也有着较大的影响,较小的注入强度及扫描周期更易于PB宽度的扩展。当给定注入强度和频率失谐时,正反向PS点所对应的偏振角度随偏置电流的增强均呈现近似增大的趋势,而PB区域宽度则表现出较大的起伏,且扫描周期越大,对应的PB宽度越小。此外,自旋反转速率也会影响VCSEL输出偏振分量的PS和PB特性,当注入参数一定时,较小的自旋反转速率更易于产生较大的PB宽度。

Based on a spin-flip model(SFM) of vertical-cavity surface-emitting lasers(VCSELs),this paper theoretically investigates the characteristics of polarization switching(PS) and polarization bistability(PB) in the VCSEL subject to continuous variable-polarization optical injection.The results show that in the case of reasonable injection parameters,PS and PB effects of the polarization components of the VCSEL can be induced by the polarization angle of the injection light when the angle is continuously scanned along the forward and reverse routes.Meanwhile,the forward and reverse PS points shift with the scan period,leading to a variable width of the PB region.For a given injection intensity,the forward and reverse PS points exhibit opposite changing patterns with the increase in scanning period.Moreover,a shorter scanning period and a larger frequency detuning are both conducive to a wider PB region.When the frequency detuning is fixed,the change in injection light intensity also has a great influence on the PS position and the PB width.A weak injection intensity and a short scanning period are both conducive to expanding the PB width.When injection intensity and frequency detuning are fixed,both the polarization angles corresponding to forward and reverse PS points demonstrate an approximate uptrend with an increasing bias current,whereas the width of the PB region experiences violent fluctuations.Furthermore,a longer scanning period leads to a smaller PB width.Additionally,the spin-flip rate also has an impact on the PS and PB characteristics of the output polarization components of the VCSEL.A lower spin-flip rate is more liable to result in a larger PB width for given injection parameters.