RIA: Novel Electroabsorption in Stained-Layer Hetero- structures A New Effect with Potential Applications in Optoelectronics Devices

光电光调制器，即可以通过施加的控制电压的变化来调制光的传输的装置，对于需要对导波进行电子控制的应用(例如，光纤通信系统)是有意义的。目前这类器件中最先进的是多量子阱(MQW)波导调制器，它利用一种称为量子受限斯塔克效应(QCSE)的电吸收效应。然而，通过利用这里提出的电吸收增强机制--场诱导吸收边缘混合(AEM)效应，MQW调制器性能的显著改善是可能的。实现这一效应所需的独特的价带结构只适用于某些类型的应变层异质结构，这些结构尚未在电吸收研究中考虑到。这项提案的主题是对迄今未被探索的AEM效应进行详细调查。我们将首先建立与场相关的近能隙吸收特性的理论模型，并将其用于优化结构以获得最大的AEM效应。然后，将通过金属有机化学气相沉积(MOCVD)生长合适的应变层MQW结构，使用低温发光技术进行评估，并用于制造测试结构。然后将尝试演示AEM效应，如果观察到该效应，将进一步表征该效应并评估其在光学调制器中的潜在用途。在合理的控制电压下观察大的AEM效应--根据本提案中描述的基本考虑，这似乎是有希望的--可能会导致现有MQW波导调制器的改进，也可能导致新的光电子器件，如压控偏振器。

Optoelectronic light modulators, i.e. devices through which the transmission of light may be modulated by variation of an applied control voltage, are of interest for applications in which electronic control of guided light waves is required (e.g. fiber-optic commlunications systems). The current state-of-the-art in such devices is the multiple-quantum-well (MQW) waveguide modulator, which makes use of an electroabsorption effect called the quantum-confined Stark effect (QCSE). Significant improvements in MQW modulator performance may be possible, however, by exploiting an electroabsorption enhancement mechanism proposed here and termed the "field-induced absorption-edge mixing" (AEM) effect. The unique valence-band configuration required to achieve this effect is available only in certain types strained-layer heterostructures which have not yet been considered in electroabsorption studies. A detailed investigation of the hitherto unexplored AEM effect is the topic of this proposal. Theoretical models of the field-dependent near-gap absorption characteristics will first be developed and used to design optimum structures for maximum AEM effect. Appropriate strained-layer MQW structures will then be grown by metalorganic chemical vapor deposition (MOCVD), evaluated using low-temperature luminescence techniques, and used to fabricate test structures. Demonstration of the AEM effect will then be attempted and, if observed, the effect will be further characterized and its potential usefulness in optical modulators assessed. Observation large AEM effects at reasonable control voltages - which seems promising based on fundamental considerations described in this proposal - could lead both to improvements in existing MQW waveguide modulators and to new optoelectronic devices such as voltage-controlled polarizers as well.