Coherent Multispectral LIDAR in Silicon Photonics using Optical Phased Arrays

使用光学相控阵的硅光子学相干多光谱激光雷达

• 批准号: 1930085
• 金额: --
• 依托单位: Queen's University Belfast
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1930085
• 关键词: Coherent; Multispectral; LIDAR; Silicon; Photonics

The project will investigate the different aspects of developing a LIDAR sensor on a low-cost, compact silicon chip under the established CMOS fabrication foundry model. The resulting photonic integrated circuit will comprise a large variety of optical components including an on-chip laser, waveguides, metal heaters, amplifiers and photodetectors, but the early focus will be on developing an optical phased array (OPA) to steer and shape the beam in the far-field. In order to have a viable LIDAR sensor with an acceptable system performance using OPAs, certain criteria must be met and satisfied. The potential impact of a fully-integrated LIDAR device on a silicon chip is huge; these devices could replace the bulky LIDAR systems seen on autonomous vehicles and drones up until now at a fraction of the SWaP (Size, weight and power requirements).An optical phased array requires splitting light from a bus waveguide via a multi-mode interference coupler, for example, into an array of waveguides with optical phase shifters attached to each channel to control the phase of each beam separately, and hence steer the beam in free-space in the desired far-field direction. Several issues have to be addressed in order to produce a high quality, narrow divergence output beam via constructive interference of the different beams from each waveguide channel in the array.The first problem is that the phase shifters, operating using the thermo-optic effect, will incur thermal crosstalk issues between adjacent waveguides and disrupt the phases of beams in adjacent channels. This problem can be alleviated by increasing the gap between the waveguides at the location of the shifters. However, this leads to a second problem in that the waveguides will be spaced too far apart at the output of the array, leading to a large beam width in the far-field. At small spacings however the modes between adjacent waveguides will interact and transfer power as in directional waveguide couplers. The waveguides will also have different optical path lengths due to the divergent and convergent path sections. Solutions to all of these problems in order to realise a large optical phased array will be investigated, simulated and then fabricated. The factors will be simulated in Lumerical MODE solutions. There will also be phase nonuniformities induced due to fabrication errors in addition to various other factors. These factors will be monitored and tested post-fabrication to find optimum voltage values for the phase shifters to counter phase nonuniformities. The later parts of the project could involve looking at different wavelengths of lasers for a multispectral analysis of a scene, which would deliver additional target information. Frequency chirping of a continuous wave source will also be studied and its feasibility of on-chip operation compared to using a pulsed source considering factors such as eye-safe operation and efficiency of target detection.

该项目将研究在低成本、紧凑的硅芯片上根据已建立的CMOS制造模型开发LIDAR传感器的不同方面。由此产生的光子集成电路将包括大量的光学部件，包括片上激光器、波导、金属加热器、放大器和光电探测器，但早期的重点将是开发一种光学相控阵(OPA)，以在远场控制和整形光束。为了有一个可行的激光雷达传感器与可接受的系统性能使用OPAS，必须满足和满足某些标准。全集成激光雷达装置在硅芯片上的潜在影响是巨大的；这些装置可以取代迄今为止在自动驾驶汽车和无人机上看到的笨重的激光雷达系统(尺寸、重量和功率要求)。光学相控阵需要通过多模干涉耦合器将来自总线光导管的光分成一组光，每个通道上都连接有光学移相器，以分别控制每束光束的相位，从而将光束在自由空间中引导到所需的远场方向。为了通过阵列中来自每个波导通道的不同光束的建设性干涉来产生高质量、窄发散的输出光束，必须解决几个问题。第一个问题是，利用热光效应工作的移相器将在相邻的波导之间引起热串扰问题，并且扰乱相邻通道中的光束的相位。这一问题可以通过增加移位器位置处的波导之间的间隙来缓解。然而，这导致了第二个问题，在阵列的输出端，波导的间隔太远，导致远场中的波束宽度很大。然而，在较小的间距时，相邻波导之间的模式将相互作用并传递能量，这与定向波导耦合器中的情况相同。由于发散路径部分和会聚路径部分的不同，波导还将具有不同的光路长度。为了实现大型光学相控阵，将对所有这些问题的解决方案进行研究、模拟和制作。这些因素将在Lumerical模式解中模拟。除了各种其他因素外，还将存在由于制造误差而引起的位相不均匀。这些因素将在制造后进行监测和测试，以找到移相器的最佳电压值，以对抗相位不均匀。该项目的后期部分可能包括观察不同波长的激光，对场景进行多光谱分析，这将提供额外的目标信息。还将研究连续波源的频率啁啾及其在芯片上运行的可行性，并与使用脉冲源进行比较，考虑到眼睛安全运行和目标检测效率等因素。