Study of ultrafast optical signal processing using polarization bistable VCSELs

我们主要研究了以下三个课题，以基于垂直腔表面发射激光器（VCSEL）的干草叉分叉双稳操作和自旋极化电子注入来创建新型非线性光学功能器件。(1)We研究了方形波导VCSEL中两个正交偏振模之间的偏振态转换。作为一个重要的全光信号处理，我们已经通过我们的模拟表明，3R功能（Retiming，Reshaping，和Regenerating）可以使用这样的VCSEL。该3R再生对于10 Gbit/s具有16 dB的大的光增益，并且光增益随着比特率的增加而减小。通过3R再生提高了开关比，最高可达100 Gbit/s。(2)We已经提出了使用超快偏振VCSEL的二维阵列的光学缓冲存储器。光缓存是光分组交换的重要器件。首先，VCSEL的偏振被光学复位脉冲复位。超快光信号被转换为空间并行信号，并与光设置脉冲一起注入VCSEL。只有当光信号和光设置脉冲同时注入VCSEL时，VCSEL才改变它们的偏振。因此，VCSEL发射具有取决于输入信号的“0”和“1”的偏振的输出。输出信号脉冲由VCSEL的CW 0°输出产生，并转换为超快光信号。(3)We研究了10 K下GaAs中输运过程中电子自旋弛豫的电场依赖性。利用量子威尔斯的光致发光测量了GaAs中2μm区域光生电子漂移前后的自旋极化。我们发现了直接的证据，在漂移过程中的电子自旋弛豫加速在较高的电场。

We investigated mainly the following three topics to create new nonlinear optical functional devices based on the pitchfork bifurcation bistable operation of vertical-cavity surface-emitting lasers (VCSELs) and injection of spin-polarized electrons.(1)We studied the bistable switching between the two orthogonal polarization modes existing in the VCSEL with a squared shape waveguide. As one important all-optical signal processing, we have shown by our simulations that the 3R function (Retiming, Reshaping, and Regenerating) can be obtained using such a VCSEL. This 3R regeneration has a large optical gain of 16 dB for 10 Gbit/s and the optical gain was reduced with an increase in bit rate. The ON-OFF ratio is improved by the 3R regeneration up 100 Gbit/s.(2)We have proposed the optical buffer memory using a two-dimensional array of the ultrafast polarization bistable VCSELs. Optical buffer memory is an important device for photonic packet switching. First, the polarization of the VCSELs are reset by an optical reset pulse. Ultrafast optical signals are converted to spatially parallel signals and injected into the VCSELs together with optical set pulses. Only when the optical signals and the optical set pulses are simultaneously injected into the VCSELs, the VCSELs change their polarization. Therefore, the VCSELs emit the outputs with the polarizations which depend on '0' and '1' of the input signal. The output signal pulses are created from the CW 0°output of the VCSELs and are converted to an ultrafast optical signal.(3)We investigated the electric field dependence of electron spin relaxation during transport in GaAs at 10K. Spin polarizations of photogenerated electrons were measured before and after drifting in the 2μm region of GaAs under photoluminescence from quantum wells. We have found direct evidence that the electron spin relaxation during the drift is accelerated in the higher electric field.