基于PbSe胶体量子点的长波长全光纤扫频OCT光源研究

Compared with computed tomography (CT) or other conventional medical diagnostic technologies, optical coherence tomography (OCT) offers the much higher spatial resolution, although its penetration depth is at present insufficient. Recently, the penetration depth of OCT has been improved through using supercontinuum source operating at a long wavelength of 1.7 µm, however, this sort of light source is not compatible with swept-source OCT (SS-OCT) systems. In this case, the SS-OCT ability of detecting deep tissues at a high sensitivity, is unavailable. To address this problem and another that the wavelengths emitted from frequency-swept laser sources are limited by their gain media, a long-wavelength operated all-fiber frequency-swept light source based on a gain medium of lead selenide (PbSe) colloidal quantum dots (CQDs) is proposed in this project, considering that PbSe CQDs have the advantages of tuning emission wavelength conveniently, broad gain bandwidth, low preparation cost, etc. By means of numerical simulation along with experimental investigation, (1) The dynamics of rapid tuning, as well as the relationship between the resonator parameters and the output properties of the light source, would be illuminated. After that, a mathematical model would be established accurately. These achievements obtained would be served as the theoretical basis while PbSe CQDs would be applied to the region of all-fiber light source of SS-OCT in the future. (2) 1.7 µm operated broadband rapid tunable laser would be obtained, and would be further applied to the field regarding the detection of deep biology tissues.

与CT等传统医学诊断技术相比，光学相干层析（OCT）成像技术能够获得更高的空间分辨率，但也存在穿透深度不足的问题。近年来，长波长1.7µm超连续谱光源的出现增加了穿透深度，然而这类光源难以应用于扫频OCT系统，无法发挥扫频OCT对深层组织探测时的高灵敏度优势。针对这一问题，并考虑到现有扫频OCT光源的增益介质辐射波长受限的问题，项目利用硒化铅（PbSe）胶体量子点辐射波长调谐灵活、增益带宽大、制备成本低等多项优势，提出基于PbSe胶体量子点的长波长全光纤扫频OCT光源。采用数值模拟与实验研究相结合的思路，①探明光源的快速调谐动力学过程、明确谐振腔参数与光源输出特性的依赖关系，准确建立数值计算模型，为今后PbSe胶体量子点在全光纤扫频OCT光源领域的应用提供理论基础；②产生1.7µm宽带快速可调谐激光，可望用于OCT深层组织探测研究中。

光学相干层析成像（OCT）是一种无损检测方式，在生物医疗领域已经得到了重要应用，但可惜的是OCT的穿透深度停留在1mm左右，限制了它的应用范围。项目通过考量OCT关键部件在提高穿透深度方面的作用，发现了工作波长的选择具有十分重要的意见。由于前期申请人积累了大量光纤激光器相关的研究经验，对项目的研究起到了很大的帮助。项目考虑到光纤激光器光束质量好的优势，并通过引入PbSe量子点来改善现有光纤激光器辐射特殊波长困难的问题，建立了PbSe量子点光纤激光器数值计算模型，分析了量子点尺寸、浓度、尺寸分布等PbSe量子点参数对激光器输出特性的影响，揭示了不同参数条件下的弛豫振荡特性；掌握了注胶量子点光纤的制备方法，并成功构建基于PbSe胶体量子点的光纤激光器；明确了PbSe胶体量子点具有良好的饱和吸收特性，构建了基于PbSe胶体量子点饱和吸收体的锁模光纤激光器，实现了稳定的皮秒脉冲激光输出。项目的实施为量子点在光纤激光器领域的应用提供了理论基础和技术支持。