Study of ultrafast optical signal processing using polarization bistable VCSELs

基于垂直腔面发射激光器（VCSELs）的干草叉分岔双稳态工作和自旋极化电子注入，我们主要研究了以下三个主题，以创建新的非线性光学功能器件。(1)研究了方形波导VCSEL中存在的两种正交偏振模式之间的双稳态切换。作为一个重要的全光信号处理，我们已经通过我们的仿真表明，使用这种VCSEL可以获得3R函数（重新定时，重塑和再生）。这种3R再生具有10gbit /s的大光增益16db，并且光增益随着比特率的增加而降低。3R再生高达100gbit /s，提高了开关比。(2)利用超快偏振双稳态vcsel的二维阵列提出了光缓冲存储器。光缓冲存储器是实现光子分组交换的重要器件。首先，利用光复位脉冲对vcsel的偏振进行复位。将超快光信号转换成空间并行信号，与光集脉冲一起注入到vcsel中。只有当光信号和光集脉冲同时注入到vcsel中时，vcsel的偏振才会发生改变。因此，vcsel发射的输出具有依赖于输入信号的“0”和“1”的极化。输出信号脉冲是由vcsel的连续波0°输出产生的，并被转换成超快光信号。(3)研究了10K下GaAs输运过程中电子自旋弛豫的电场依赖性。在量子阱的光致发光作用下，测量了光生电子在GaAs 2μm区域漂移前后的自旋极化。我们发现了电子自旋弛豫在高电场中加速漂移的直接证据。

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.