Study of ultrafast optical signal processing using polarization bistable VCSELs

基于垂直腔面发射激光器(VCSEL)的干叉分叉双稳工作和自旋极化电子的注入，我们主要研究了以下三个方面的内容，以创造新的非线性光学功能器件。(1)研究了正方形波导垂直腔面发射激光器中存在的两个垂直偏振模之间的双稳开关。作为一种重要的全光信号处理，我们的模拟表明，使用这种VCSEL可以获得3R功能(重定时、整形和再生)。这种3R再生对于10Gbit/S具有16db的大的光增益，并且光增益随着码率的增加而减小。通过3R再生，开关比提高了100Gbit/S。(2)提出了一种基于超快偏振双稳VCSEL二维阵列的光缓冲存储器。光缓冲存储器是光分组交换的重要器件。首先，通过光学重置脉冲来重置VCSEL的偏振。超快光信号被转换成空间上平行的信号，并与光学设置脉冲一起注入VCSEL。只有当光信号和光设置脉冲同时注入到VCSEL中时，VCSEL才改变其偏振。因此，VCSEL发射具有取决于输入信号‘0’和‘1’的偏振的输出。输出信号脉冲由垂直腔面发射激光器的0°连续输出产生，并被转换成超快光信号。(3)我们研究了10K下电子自旋驰豫在GaAs中输运过程中的电场依赖性。在量子井光致发光下测量了GaAs2μm区漂移前后光生电子的自旋极化。我们发现了电子漂移过程中电子自旋弛豫在较高电场中加速的直接证据。

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.