基于硅基可调谐滤波器的MHz频域锁模激光器研究

We propose a high-speed wavelength-tunable optical filter based on silicon photonics to overcome the imaging speed limitation of current swept-source optical coherence tomography (OCT) system imposed by the inertia of moving part. Design method for the tunable filter will be studied, the device will be fabricated and tested. A novel type of Fourier-domain mode-locked laser (FDML), i.e. discrete-frequency Fourier-domain mode-locked lasers based on the proposed filter will be made to provide an Ascan rate in the order of MHz. Lasing mechanism of such FDML and its imaging characteristics will be investigated. In order to solve the stability problem associated with FDML, as well as to reduce the cost, we proposed a self-feedback, self-stabilized FDML which is expected to greatly increase the acceptance of the FDML technology. The works in this project will provide a solid technical foundation for the future implementation of video-rate 4D-OCT imaging.

提出一种基于硅基光子学技术实现高速可调滤波器的新思路，以突破当前扫频相干光学层析成像中由于机械调谐机制所造成的滤波器调谐速率瓶颈。项目将研究硅基可调谐滤波器的设计方法，制作器件并测试其性能。利用这种硅基高速可调谐滤波器，研制出基础扫频速率达到MHz的一种新型频域锁模激光器，即离散频率频域锁模激光器，将对这种激光器的工作机理及成像特性进行研究。项目还针对频域锁模激光器的稳定性差和成本高的缺点，提出了基于频率自反馈的自稳定频域锁模方法，该方法将极大增强频域锁模激光器的实用性。项目将突破现有扫频激光器的扫频速率限制瓶颈，为未来视频帧率4D光学相干层析成像提供基础技术支持。

为突破扫频激光器中波长调谐器件惯性限制的速率瓶颈，提出采用级联硅基微环电流调谐透过峰的解决思路。利用低损耗多模波导实现了环长为3.4mm，本征Q值高达2,180,000的硅基微环，并以此构建了调谐速率为45kHz的频域锁模激光器(FDML)。建立了分立频率频域锁模激光器(DF-FDML)的理论模型，给出了相干长度的理论公式，搭建了扫频速率为45kHz的DF-FDML,获得了与传统FDML质量无差别的图像，证明了DF-FDML的可用性。实现了无需外部时钟驱动，实时跟踪环长变化的自稳定自主振荡频域锁模激光器，研究了其调制谱宽自限制作用。实现了基于C-Lens和MEMS的OCT内窥镜，可在内窥镜位置固定下实现360度全方位光学扫描。开发了扫频OCT基于压缩采样的图像重建算法，等效成像速率提高了3倍。