Intersubband Electro-optic modulators

光调制器是光收发信机的关键器件。数十亿美元的光收发器市场日益要求具有更高性能和可持续成本的设备。磷化铟(InP)技术需要提供超过100G的下一代光通信系统，而最近的InP光子学创新确实承诺在带宽、功耗和端口密度方面具有高性能。在当前一代的基于InP的电吸收调制器中，通过带间吸收工作，报告的吸收恢复时间被限制在5ps。另一方面，基于InP的量子阱中的子间跃迁具有亚皮秒载流子弛豫时间和大的光学非线性的固有特性，在实现超高速光调制方面具有很好的应用前景。对于通过子带间跃迁以及其他并行过程操作的设备，带宽也有望大幅提高，包括热电子发射和隧道效应。此外，基于子带间跃迁的器件利用了传统的III-V材料以及先进的InP工程能力和可靠的器件技术，因此可以简单地将不同的光子组件集成在一块芯片上，从而实现更高的集成密度和更低的成本。最后但并非最不重要的一点是，标准的带间EAM是温度相关的，因为带边随温度以约0.5 nm/C的速率移动，而在子带间电光调制器中，这一速率估计减少了一个数量级，即跃迁能量将以约0.05 nm/C的速度移动，使其适合用作非制冷器件。在这个项目中，将探索InP衬底上的子带间电光调制器用于下一代数据通信系统的潜力，这与EPSRC的主题领域、信息和通信技术(ICT)保持一致。目的和目标：该项目将致力于开发基于子带间转换的高速调制器。该项目的主要目标是：目标1：了解InGaAs/AlAsSb量子阱中子带间跃迁的电光效应。目标2：研制界面陡峭、晶体质量高的1550 nm光学活性高质量量子阱。目标3：优化装置结构。实现高电光系数和量子阱的高速调制。潜在的应用和好处：在该项目的早期阶段，工业和学术导师将通过广泛的文献查阅指导博士生在该领域发展必要的知识。项目期间将为博士生的培训提供设施通道和设备，包括外延生长设备和器件加工净化室。博士生还将接受一些材料和设备表征设备的培训。在项目结束时，将开发一种新型的电光调制器，使数据通信更快，并推动英国ICT产业的发展。博士生将有机会参加国内和国际会议，传播在该项目中取得的任何科学进展。

Optical modulators are the key elements of optical transceivers. The multi-billion market of optical transceivers increasingly demands devices with higher performance with sustainable cost. Indium phosphide (InP) technology need to deliver next generation optical-communication systems beyond 100 G, and recent InP photonics innovations indeed promise high performance in terms of bandwidth, power consumption, and port density. In current generation InP based electro-absorption modulators that operate by interband absorption, the absorption recovery time reported is limited to 5 ps. On the other hand, intersuband transitions in InP based quantum wells is quite promising to achieve ultra-high speed optical modulation due to its intrinsic characteristics of sub-picosecond carrier relaxation time and large optical nonlinearities. Substantial improvements in the bandwidth can also be expected for devices operated by intersubband transitions along with other parallel processes, including thermionic emission and tunnelling. Moreover, the devices based on intersubband transitions take advantages of conventional III-V materials and the advanced InP engineering capability and reliable device technology, and thus different photonic components can be simply integrated on a single chip, leading to higher integration density and lower cost. Last but not least, standard interband EAMs are temperature dependent because the band edge moves with temperature at a rate around 0.5nm/C, while in intersubband electro-optic modulators, this rate is estimated to be reduced by one order, i.e. transition energy will move at around 0.05 nm/C, making it suitable for use as an uncooled device.In this project, the potential of intersubband electro-optic modulators on InP substrates will be explored for the next generation data communication systems, which is aligned with the EPSRC thematic area, Information and communication technologies (ICT). Aims and objectives:The studentship project will focus on developing high speed modulators based on intersubband transitions. The main objectives of the project are:Objective 1: To understand the electro-optic effects of intersubband transitions in InGaAs/AlAsSb QWs. Objective 2: Develop high quality quantum wells with abrupt interface and high crystal quality that are optically active at 1550 nm. Objective 3: Optimise the device structure. Achieve high electro-optic coefficient and high speed modulation of the quantum wells.Potential applications and benefits:During the early stage of this project, both industrial and academic supervisors will guide the PhD student to develop necessary knowledge in this field by extensive literature review. Facility access and equipment will be provided for the training of the PhD student during the project, including epitaxy growth equipment and device processing cleanroom. The PhD student will also be trained for a number of material and device characterization equipment. At the end of the project, a new type of electro-optic modulator will be developed that can make the data communication faster and advance the ICT industry in UK. The PhD student will be provided the opportunities to attend domestic and international conferences to disseminate any scientific advance made in the project.