【作者】 陈明惠；

【导师】 丁志华；

【作者基本信息】 浙江大学 ， 光学工程， 2011， 博士

【摘要】 光学相干层析成像(Optical Coherence Tomography, OCT)技术是一种微米级分辨率的成像技术,通过测量散射光的振幅和回波时延,从而获得生物样品内部层析结构信息。本文的研究工作主要解决了光学相干层析实时成像系统研究的一个关键技术问题——高性能快速扫频激光光源的设计与搭建。提出三种不同调谐滤波设计新方案,研制了四套扫频激光光源,并将该扫频激光光源应用于光学频域成像(optical frequency domain imaging, OFDI)系统,实现了对生物组织内部高分辨实时成像研究。具体研究内容以及创新性研究成果包括：1、研制基于光纤法布里珀罗调谐滤波器(fiber Fabry-Perot tunable filter, FFP-TF)的全光纤型环形腔扫频激光光源。该扫频激光光源中心波长为1320 nin,整个扫频范围为120 nm,光谱半高全宽为65 nm,瞬时线宽的3 dB带宽为0.08nm,扫频速度8 kHz,平均光功率输出9 mW。全光纤型扫频激光光源具有结构紧凑,抗干扰能力强,易于便携等特点。2、光纤法布里珀罗全光纤型扫频激光光源应用于光学频域成像,得到轴向分辨率为13.6μm(空气中),最大成像深度为3.4 mm(空气中),最大灵敏度为112 dB,实时获得了生物组织和散射样品的高分辨率实时在体成像。通过改变法布里珀罗调谐滤波器不同驱动函数,研究OCT成像变化,同时还实验研究了腔的长度与扫频速度和光功率关系,为优化扫频激光光源提供参考意义。3、研制基于光栅/多面镜调谐滤波器的短腔宽带快速扫频激光光源,中心波长为1312 nm,扫频速度50 kHz,扫频范围为170 nm,半高全宽为116 nm,平均光功率输出2 mW。调谐滤波器由光栅和旋转多面镜组成,采用了非望远镜型利特罗结构,以简化滤波光学系统。在激光谐振腔中采用了放大自发辐射光谱范围互为拓展的双半导体光放大器为增益介质,并将二者并联使用以确保宽光谱范围。4、研制了基于光栅/多面镜调谐滤波器的傅里叶域锁模(Fourier domain mode locking, FDML)长腔线性扫频激光光源。激光谐振腔主要包含增益介质、调谐滤波器和延迟线。增益介质采用了两个串联的半导体光放大器以确保大的增益系数。FDML扫频激光光源的中心波长为1290 nm,扫频速度为14.8 kHz,扫频范围为108 nm,半高全宽为61 nm,输出平均功率达3 mW。5、研制基于组合型调谐滤波器的超宽带窄瞬时线宽线性扫频激光光源。组合型调谐滤波器由自由光谱范围宽、光谱分辨率低的光栅/多面镜调谐滤波器和工作在非谐振条件下的自由光谱范围窄、光谱分辨率高的法布里珀罗调谐滤波器级联而成,兼备宽的自由光谱范围和高光谱分辨率双重优势。研制的扫频激光光源的中心波长为1290 nm,扫频光谱范围为180 nm,半高全宽为114nm,瞬时线宽可达到0.03 nm,扫频速度为23.3 kHz,相应的激光输出平均功率为3 mW。更多还原

【Abstract】 Optical coherence tomography (OCT) is a micrometer-resolution imaging technique that produces cross-sectional images of sample microstructure by measuring the amplitude and echo time delay of backscattered light. In this dissertation, the research is focused on development of high performance swept laser source which is the key technique of real-time optical coherence tomography imaging. Three different tuning filters design are proposed, four sets of swept laser source based on different methods are developed. Implementing the laser source in optical frequency domain imaging system, real-time and high resolution structural imaging of biological tissue is demonstrated. The main work and innovations are summarized as follows:1. All-fiber ring-cavity wavelength swept laser source based on fiber Fabry-Perot tunable filter is demonstrated. The developed laser source provides up to 8,000 sweeps per second over a full-width wavelength tuning range of 120 nm, full width at half maximum of 65 nm at center wavelength of 1320 nm.3 dB bandwidth of the instantaneous linewidth is about 0.08 nm and average power is 9 mW. All-fiber swept laser is compact, portable and easy to maintenance.2. Implementing the all-fiber Fabry-Perot tunable filter based swept laser source in optical frequency domain imaging system, the axial resolution is 13.6μm (in air), the axial range is 3.4 mm (in air) and maximum sensitivity is about 112 dB. Real-time in vivo structural imaging of biological tissue and scattering medium is obtained. For optimization consideration based on this custom-built swept laser, experimental study on imaging quality relevant parameters of the swept laser with sine and ramp driving waveforms to the FFP-TF is conducted, and investigation of the repetition rate and output power on the cavity length is done.3. A broad-band high-speed short-cavity swept laser source based on grating & polygon mirror tunable filter is reported. Center wavelength of the developed swept laser source is 1312 nm with a turning range of 170 nm and 3dB bandwidth of 116 nm. A repetition frequency up to 50 kHz with an average output power of 2 mW is realized. In order to facilitate the filtering system, the tunable filter consists of polygon scanner and grating in Littrow telescope-less configuration. Parallel implementation of two semiconductor optical amplifiers with different wavelength range is adopted in the laser resonator for broad-band light amplification.4. A Fourier domain mode locking (FDML) long-cavity linearized swept laser source is presented. The laser resonator includes gain medium, tunable filter and delay line. Serial implementation of two semiconductor optical amplifiers is adopted in the laser for gain amplification. The tunable speed of the FDML swept laser centered at 1290 nm is 14.8 kHz with an average output power of 3 mW. The turning range is 108 nm with 3dB bandwidth of 61 nm.5. A novel broad tunable bandwidth and narrow instantaneous line-width linear swept laser source using combined tunable filter is proposed. The combined filter consist of a fiber Fabry-Perot tunable filter working at the non-resonant frequency and a tunable filter based on diffractive grating with scanning polygon mirror. The trade-off between bandwidth and instantaneous line-width is alleviated. The swept laser working at 1290 nm center wavelength provides a tuning range of 180 nm with 3dB line-width of about 114 nm at sweeping rate of 23.3 kHz. The instantaneous linewidth can be reach to 0.03 nm and output power is 3 mW.更多还原