Electroabsorption modulators and laser diodes for free space optics and on-chip applications

主要目标是设计一种可安装在无人机（UAV）上的调制器，以提供快速、安全和鲁棒的光学数据链。仅在过去十年中，人们就对自由空间光通信系统进行了大量研究，调制回复反射器系统是轻型高效调制器的最佳解决方案。这项工作的大部分集中在猫眼回射器（CER）系统，而不是简单的角隅棱镜回射器（CCR），由于尺寸和速度的限制，与较大的CCR。由于透镜定位所需的高精度、潜在的光学像差和对视场的相当严重的限制，CER系统通常不如CCR稳健。本计画的主要目的是利用现代制造技术来建构一个大型的像素化电吸收CCR调变器。制造技术的进步为II型半导体系统创造了更多的可能性，这些将成为进一步研究、建模和测试的基础。锑基化合物在1.55um波长下显示出巨大的应用潜力。制造和制造的发展允许构建精确的II型多量子阱异质结构，可以设计用于这种特定用途。材料系统，这似乎是最适用的结合GaSb量子威尔斯与AlGaSb的障碍。然后将在P-I-N二极管结构内制造该多量子阱有源区。II型材料具有空间分离的电子和空穴的强限制，因此通常空穴被限制到阱材料，而电子被限制到势垒材料。当在电偏压下时，这可能导致材料的光学吸收发生非常大的偏移。此外，通过对这种材料进行像素化，可以实现高速数据传输，而不会损害回射器的视场。该项目的另一个目标是创建“智能”像素，仅在波长为1.55 μ m的入射光下才有效。这将大大降低调制器的总功耗。优化系统的其他考虑因素将是材料的温度稳定性、对比度和插入损耗。其目的是，博士学位也将测试生长结构的性能。

The main objective is to design a modulator that can be fitted to an unmanned aerial vehicle (UAV) to provide an optical datalink that is fast, secure and robust. There has been a significant amount of research conducted into free space optical communication systems in the last decade alone and a modulating retro-reflector system is the best solution for a lightweight and efficient modulator. The bulk of this work has focussed on cat's eye retro-reflector (CER) systems, rather than the simpler corner-cube retro-reflector (CCR), due to limitations on size and speed that come with the larger CCR. CER systems are generally less robust than CCR due to high precision required in lens positioning, potential optical aberrations and quite severe limitations on field of view. The primary aim for this project is to utilize modern manufacturing and fabrication techniques to construct a large, pixelated electro absorption CCR modulator. Advances in manufacturing techniques have created more possibilities in type-II semiconductor systems and these will form the basis for further research, modelling and testing. Antimony based compounds show great potential for application at 1.55um wavelength. Manufacturing and fabrication developments allow for the construction of precise type-II multiple quantum well heterostructures that can be engineered to this specific use. The material system which appears to be the most applicable combines GaSb quantum wells with AlGaSb barriers. This multiple quantum well active region will then be fabricated within a P-I-N diode structure. Type-II materials have strong confinement of electrons and holes with spatial separation, thus generally holes are confined to the well material and electrons to the barrier material. This can lead to very large shifts in the optical absorption of the material when under an electrical bias. This is ideal for providing a high extinction ratio.Furthermore, by pixelating this material, high speed data transmission can be achieved without compromising the field of view of the retro-reflector. Another aim for the project is to create 'smart' pixels that will only be active upon incident light of wavelength 1.55um. This will greatly reduce the overall power consumption of the modulator. Other considerations to optimise the system will be the temperature stability of the material, contrast ratio and insertion loss. The intention is that the PhD will also characterise the performance of as-grown structures.