双重滤波扫频光源的研制

扫频光源是目前光学相干层析成像的关键部分,其光谱带宽和瞬时线宽分别影响着成像系统的轴向分辨率和成像深度。在单一滤波器中,这两者相互制约。针对这一情况,提出了一个利用两种滤波器组合优化的扫频光源系统。以双半导体光放大器并联作为增益介质,将声光可调滤波器(AOTF)和法布里-珀罗可调滤波器(FFP-TF)串联接入环形腔内进行双重滤波。其中AOTF的调谐范围和瞬时线宽均较宽,FFP-TF与之相反,经同步匹配设置后,两者协调工作,能够发挥各自的优势。通过搭建系统,获得了中心波长为1 316 nm的扫频激光输出,其光谱是1 235～1 380 nm,调谐范围是145 nm,瞬时线宽小于0.02 nm,扫频速度为1.35 kHz,输出光功率为0.48 mW。该扫频光源能够克服单一滤波器的固有缺陷,实现宽光谱带宽与窄瞬时线宽的有效统一,对成像综合性能的优化具有重要意义。

Development of swept source based on dual filtering

Swept source is a key component of optical coherence tomography; its spectral bandwidth and instantaneous linewidth directly affect the axial resolution and imaging depth of the imaging system. In a single filter, the two parameters are mutually exclusive. Here, a swept source system with two filters combined for optimization was proposed. Two semiconductor optical amplifiers in parallel were used as the gain medium. An acousto-optic tunable filter (AOTF) and a Fiber Fabry-Perot Tunable Filter (FFP-TF) were connected in series in a ring cavity. The tuning range and instantaneous linewidth of the AOTF were relatively wide, while those of the FFP-TF were comparatively narrower. Post synchronization and matching setting, the two filters worked in coordination with mutual advantage. The system delivers a swept output with a center wavelength of 1 316 nm. The spectral range is between 1 235-1 380 nm, while the tuning range, instantaneous linewidth, sweep speed, and output optical power are 145 nm, less than 0.02 nm, 1.35 kHz, and 0.48 mW, respectively. The swept light source can overcome the inherent defects of a single filter and achieve an effective compromise between the broad spectral bandwidth and narrow instantaneous linewidth. This is of great significance for optimizing the overall imaging performance.