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

主要目标是设计一种可以安装在无人机（UAV）上的调制器，以提供快速、安全和强大的光数据链。仅在过去十年中，对自由空间光通信系统进行了大量的研究，而调制后向反射器系统是轻量级和高效调制器的最佳解决方案。由于更大的CCR在尺寸和速度上的限制，这项工作主要集中在猫眼反射器（CER）系统上，而不是更简单的角立方反射器（CCR）。由于镜头定位精度要求高，潜在的光学像差和相当严重的视场限制，CER系统的鲁棒性通常不如CCR系统。本项目的主要目标是利用现代制造和制造技术来构建一个大型的像素化电吸收CCR调制器。制造技术的进步为ii型半导体系统创造了更多的可能性，这些将为进一步的研究、建模和测试奠定基础。锑基化合物在1.55um波段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，可以设计用于此特定用途。将砷化镓量子阱与砷化镓势垒结合在一起的材料体系似乎是最适用的。该多量子阱有源区将在P-I-N二极管结构中制造。ii类材料对电子和空穴的约束较强，具有空间分离性，一般空穴局限于阱材料，电子局限于势垒材料。当处于电偏压下时，这可能导致材料的光学吸收发生非常大的变化。这是提供高消光比的理想方法。此外，通过对这种材料进行像素化处理，可以在不影响后向反射器视野的情况下实现高速数据传输。该项目的另一个目标是创造“智能”像素，只有在波长1.55微米的入射光下才会激活。这将大大降低调制器的整体功耗。优化系统的其他考虑因素包括材料的温度稳定性、对比度和插入损耗。其目的是博士学位也将表征生长结构的性能。

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.