硅基高速波长可调激光器

It is ungently demanded to build high-speed optical routing systems among CPUs of high performance computers (HPCs). Silicon photonic integrated circuits, which are compact and CMOS compatible, are regarded as the most promising solution on this issue. However, the conventional optical routing systems based on large matrices consist of 2x2 Mach-Zehnder switches or micro-ring resonators have complicate topologies, controlling systems and many controlling units, which degrades their system stability and reliability. On the other hand, the systems realizing wavelength routing with wavelength tunable laser sources (TLSs) and passive wavelength select devices are ideal, since they have much less controlling units, simple controlling mechanism and simple structures. Thus, TLSs based on silicon photonic technology with ultra-high wavelength tuning speed, which are the key devices in wavelength routing systems, are highly demanded, since the silicon TLSs reported before are all based on thermos-optic effect with tuning speeds of microseconds. Here, for the first time we propose an ultra-high speed silicon TLS integrated on a silicon-on-insulator substrate, which consists a III-V semiconductor optical amplifier and an external resonator based on silicon waveguides. The TLS wavelength is tuned by using free carrier dispersion effect in silicon waveguides of external resonators. The research will focus on the study of high efficiency coupling of optical/electric/thermal field in hybrid integrated photonic devices, the ultra-high speed TLS tuning with high-speed and low-loss optic-electronic modulation in silicon waveguides, as well as the technology of CMOS compatible heterogeneous integration of III-V compound photonic devices and the silicon waveguide devices. The TLS will be fabricated with CMOS compatible processes. It will have a tuning speed of less than dozens nanoseconds, with a laser power output of more than 5mW. The development of this ultra-high speed silicon wavelength tunable laser will be a significant progress for building high-speed optical routing systems in next generation Exascale high performance computers.

高性能计算机(HPC)面临内部单元超节点CPU间要求大容量、低延迟数据交换的发展瓶颈，基于硅基光子集成技术的光交换集成度高、容量大、延迟时间短，被公认为最理想解决方案之一。其中光开关阵列型和微环路由型光交换方案拓扑结构复杂、控制单元多、稳定性可靠性较差，而利用波长可调激光器(TLS)的载波波长切换实现波长路由的方案因系统简洁、控制单元少被广泛关注，因此为满足CPU间低延迟、易控制的高速交换需求，本项目在国际上首次提出利用载流子色散效应的高速硅基电光调谐TLS设计方案并研究，将重点探索硅基高速低损耗电光调谐激射机理、异质器件光/电/热高效互耦/作用/隔离机制等科学问题，开发III-V族光电子器件的CMOS兼容硅基集成技术，实现高速低损耗电光调谐外腔和III-V族半导体光放大器的硅基单片集成TLS器件，波长切换速度达到10ns量级或以下，输出功率5mW以上，为HPC可持续发展奠定核心硬件基础。

目前数据中心和高性能计算机面临低功耗、大容量、低延迟数据交换的发展瓶颈，基于硅基光子集成芯片的光交换因集成度高、容量大、延迟短、低能耗被公认为理想方案之一。其中光开关和微环路由方案网络结构复杂、单元多、工艺稳定性差，而利用波长可调激光器（TLS）可以通过载波波长切换实现波长路由系统简洁，为实现低延迟、易控制高速交换，本项目计划开展高速波长可调激光器研究。.本项目在国际上首次提出利用载流子色散效应的高速硅基电光调谐TLS方案，申请专利并获得授权，研究了硅基高速低损耗电光调谐机理，通过对硅基PIN结波导可调外腔及其与半导体光放大器（SOA）组合的系统仿真，理论验证了利用硅基载流子色散效应制作可调外腔实现高速TLS的可行性，仿真验证波长可调30nm、调谐速度可达10ns。因工艺等问题，同想法被诺基亚III-V实验室于2018年底抢先实现，间接验证了该方案的意义和可行性。.硅PIN结波导外腔的载流子吸收光损耗将影响激光器稳定工作，我们创新性改用硅基铌酸锂薄膜材料研制光波导外腔并申请了专利。硅基铌酸锂薄膜具有电光效应强、调谐快、无载流子吸收损耗等优点，是新兴的理想光电子器件材料。因此，项目转入硅基铌酸锂薄膜外腔高速TLS研制。研究确定了硅基铌酸锂薄膜光波导、方向性耦合器及调谐电极的结构。在没有经验参考下经过反复工艺试制，突破了铌酸锂薄膜加工关键工艺。成功制备了硅基铌酸锂薄膜电光调谐微环外腔，测得调谐效率6.97pm/V，以单环谱线叠加推出双环外腔波长可调10nm，经双环谐振器外腔和SOA耦合实验，在国际上首次验证了硅基铌酸锂薄膜外腔激光器产生激光激射，并可实现波长调谐，波长调谐范围达3nm。项目研究发表SCI论文5篇，申请专利7项，授权5项，培养博士生5人，硕士生1人。项目成果验证了硅基高速可调激光器方案和工艺的可行性，为数据中心和高性能计算机可持续发展提供了核心硬件解决方案。