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Simultaneous Realization of Ultrafast and High-Nonlinearity Optical Response Characteristics by Shape-Controlled Quantum Dots

通过形状控制的量子点同时实现超快和高非线性光学响应特性

基本信息

批准号：
14350167
负责人：
WADA Osamu
金额：
$ 8.19万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

Quantum dots are expected to play a key role in future optical communications due to their advantages in enhancing linear optical gain and nonlinear optical response, as well as ultrafast response speed, which result from the three dimensionally confined electron states. However, quantum dots formed by SK-mode growth have flattened shape much different from the ideal sphere, and this causes polarization sensitiveness, usually being heavily TE-polarized, and also there are no precise understanding of the effect of dot shape on the optical response speed and nonlinearity.In this study, it has been shown from polarization discriminating photoluminescence measurements that the polarization property can be controlled by optimizing the dot shape using columnar dot structure, in which SK-dot layers are stacked. Also it has been shown that the polarization properties are controlled by changing the composition of InGaAs capping layer on InAs dots primarily due to the effect of dot aspect ratio, which is enhanced by the introduction of InGaAs capping layer resulting in TM dominant polarization. This indicates that the polarization insensitiveness, which is one of the most important device characteristics in practical application, can now be controlled by designing the dot shape.Our previous results have demonstrated that quntum dot optical amplifier exhibits ultrafast absorption recovery time in the range of 1-3 ps. Also it has been shown from degenerate four-wave mixing (DFWM) experiments that large size dots show phase relaxation time larger that that for small size dots, indicating the possibility of enhanceing nonlinearity in larger dots.Combining all these results obtained, it is concluded that polarization insensitive, ultarafast and high-nonlinearity optical response can be simultaneously achieved by adopting isotropically shaped, large size dots.

量子点因其在增强线性光学增益和非线性光学响应方面的优势，以及三维受限电子态带来的超快响应速度而有望在未来光通信中发挥关键作用。然而，SK模式生长形成的量子点的扁平形状与理想球体有很大不同，这导致了偏振敏感性，通常是严重的TE偏振，而且对于点形状对光学响应速度和非线性的影响也没有精确的理解。在本研究中，通过偏振判别光致发光测量表明，可以通过使用柱状点优化点形状来控制偏振特性。结构，其中SK-dot层堆叠。还表明，偏振特性是通过改变 InAs 点上的 InGaAs 覆盖层的成分来控制的，这主要是由于点长宽比的影响，而点长宽比的影响通过引入 InGaAs 覆盖层而得到增强，从而导致 TM 主导偏振。这表明，偏振不敏感是实际应用中最重要的器件特性之一，现在可以通过设计点形状来控制。我们之前的结果表明，量子点光学放大器表现出1-3 ps范围内的超快吸收恢复时间。简并四波混频（DFWM）实验表明，大尺寸点的相位弛豫时间大于小尺寸点的相位弛豫时间，这表明大尺寸点的非线性增强的可能性。综合所有这些结果，得出结论：采用各向同性形状的大尺寸点可以同时实现偏振不敏感、超快和高非线性光学响应。