Development of Ultra-broadband Wavelength Tunable Semiconductor Lasers

波长可调谐半导体激光器是下一代光传送网的核心，其中波长路由和寻址是核心功能。在广泛部署的波分复用光纤通信系统以及先进的数据传输系统中，为了节约成本和解决多波长激光库存中涉及的复杂问题，迫切需要可调谐激光器作为后备光源。用于计算机数据交换的芯片级光互连依赖于可调谐激光器来建立节点或核心之间的完全连接，因为添加波长作为额外维度可以大大简化交叉链路拓扑结构。精密的激光雷达系统，特别是在无人驾驶汽车中，需要可调激光来获得更高的精度，并确保其在恶劣天气条件下的运行。在医疗和安全目的的传感器应用中，以及在光学测量系统中，可调谐激光器能够实现波长扫描，因此系统性能可以在许多方面得到极大的提高。传统的改变激光波长的方法都是基于调谐材料的折射率。然而，这些方法的一个主要问题在于它们的调谐范围很窄，因为材料的折射率很难调谐到1%以上。扩大调谐范围的一项优雅技术是利用游标效应。然而，调谐是准连续的，更严重的问题源于激光波长对调谐力的非单调依赖，这使得为所需的激光波长寻找合适的偏置组合既冗长又乏味。提出的研究计划的目标是开发具有全新调谐方法的超宽带波长可调谐半导体激光器。所提出的方法的根本区别是通过改变光波的属性而不是通过改变材料的属性来执行调谐。为了调谐目的而改变波特性的例子包括旋转场偏振状态、或控制光束角度、或改变波分布的简并状态。通过利用材料的各向异性和结构的不对称性，我们的目标是迫使波经历显著的有效折射率变化，从而以连续和单调的方式产生超过100 nm的波长调谐范围。这项研究计划将建立的概念，它将发明的结构，它将展示的装置，以及我们将通过其获得的知识，不仅将促进可调谐激光器的发展，还将使相关领域的一些加拿大公司受益，如Enablence、Lumentum/Oclaro(加拿大)、Ciena(加拿大)和华为(加拿大)。该项目还将为加拿大工业培养一批高技能和急需的研究生。

Wavelength tunable semiconductor laser is the heart of the next generation optical transport networks where wavelength routing and addressing serve as core functions. In widely deployed wavelength division multiplexed fiber-optic telecommunication systems as well as in advanced data transmission systems, tunable lasers are much wanted as the backup source for saving the cost and solving complicated issues involved in multiple wavelength laser inventory. Chip level optical interconnects for computer data exchange relies on tunable lasers to establish full connections among nodes or cores, as the cross-link topology can be greatly simplified with wavelength added as an extra dimension. Sophisticated LiDAR systems, especially in driverless cars, need tunable lasers to gain more accuracy and to secure their functioning in adverse weather conditions. In sensor applications for medical and security purposes, and in optical measurement systems, tunable lasers enable wavelength scanning hence the system performance can be greatly enhanced in many aspects. Conventional approaches to change the lasing wavelength are all based on tuning the material refractive index. A major problem with these approaches, however, lies in their narrow tuning ranges, for the fact that the material refractive index can hardly be tuned beyond 1%. An elegant technology to expand the tuning range is to exploit the Vernier effect. However, the tuning is quasi-continuous with an even more serious issue rooted from the non-monotonic dependence of the lasing wavelength on the tuning force, which makes the searching of a proper bias combination for a required lasing wavelength lengthy and tedious. The objective of the proposed research program is to develop ultra-broadband wavelength tunable semiconductor lasers with completely new tuning methodologies. The fundamental difference in the proposed approach is to perform tuning by changing the properties of the optical wave, rather than by changing the properties of the material. Examples of changing wave properties for the tuning purpose include rotating the field polarization status, or steering the beam angle, or altering the degenerate status of the wave distribution. By exploiting the material anisotropicity and structural asymmetry, we aim at forcing the wave to experience significant effective index changes that will lead to a wavelength tuning range beyond 100 nm in a continuous and monotonic fashion. The concept that this research program will establish, the structure that it will invent, the device that it will demonstrate, and the knowledge through which we will acquire, will not only prompt the development of tunable lasers, but will also benefit a number of Canadian companies in relevant areas, such as Enablence, Lumentum/Oclaro (Canada), Ciena (Canada), and Huawei (Canada). The program will also generate a stream of highly skilled and much needed graduate students for Canadian industry.