【作者】 郭以平；

【导师】 王肇颖；

【作者基本信息】 天津大学 ， 物理电子学， 2009， 硕士

【摘要】 光学相干层析(OCT)技术能够对活体组织进行实时、高分辨率断层成像,对活体组织内部机构的生理、病理变化过程作精确的分析和诊断,对它的开发研究,将为生物医学领域提供一种全新的重要诊断手段。本论文针对OCT硬件系统的核心部件OCT光源及系统本身,结合现有条件进行了如下的研究工作:一、非线性偏振旋转(NPR)被动锁模光纤激光器(PMLFL)的数值模拟和实验研究1.理论分析了被动锁模光纤激光器光腔参数对输出脉冲特性的影响。2.对NPR被动锁模光纤激光器进行了数值模拟分析,提出并分析了一种有效的避免多脉冲现象的方法。3.在环形腔PMLFL中,利用光谱边带测量法计算腔内总色散,通过改变腔内普通单模光纤(SMF)的长度实现色散匹配,获得了重复频率25MHz,脉宽520.5fs,中心波长1558.4nm,3dB带宽29.5nm的超短脉冲,输出功率1.81mW。4.在σ形PMLFL中实现了脉冲宽度670.5fs,重复频率为6.2MHz,中心波长1562.3nm的稳定锁模输出,输出功率为1.5mW,并将其封装成实验室样机。二、光纤中产生超连续谱的数值模拟分析和实验研究1.通过数值计算,从光纤的各种非线性效应、光纤参数以及泵浦脉冲参数等方面分析了影响超连续光谱特性的因素。2.将不同的光纤作为非线性介质产生超连续谱,对实验结果进行分析比较。3.采用不同种光纤匹配连接的方法产生超连续谱,比较光谱特性,得出了第一段被泵浦光纤的色散和非线性特性最大程度上影响光谱质量的结论,在高非线性光纤(HNLF)后接入色散位移光纤(DSF)或SMF来平衡光谱的平均功率,谱宽和平坦度等性能指标,以便应用于相关领域。在泵浦120m HNLF+4.57km DSF+2.04km SMF时得到生物体探测窗口～1300nm 3dB谱宽为140.6nm的宽带光谱。用该光源作为光学相干层析系统光源,理论上可以得到<4.1μm的纵向分辨率。三、频域OCT系统的实验研究1.讨论了一阶Born近似的傅里叶衍射层析定理及频域OCT的测量原理。2.根据频域OCT的基本原理,搭建起一套频域OCT系统。对平面镜和三层叠放在一起的盖玻片进行探测,对探测到的干涉信号进行处理从而得到被探测点的深度信息,发现系统纵向分辨率可以达到16.4μm或者更高。更多还原

【Abstract】 Optical coherence tomography (OCT) technology can carry out real-time and high-resolution imaging of living tissue. It can be used to analysis and diagnosis physiological and pathological changes of internal in-vivo tissues. It will provide a new important method of diagnosis for the biomedical field to research and develop the technology. This dissertation was focused on OCT optical source which was the key component of OCT system and system itself, which included:1. Nonlinear polarization rotation (NPR) passively mode-locked fiber laser (PMLFL).1) Influence of cavity parameters on output pulse width, chirp, bandwidth and stability was investigated numerically.2) NPR passively mode-locked fiber laser was numerical simulated and analysed, an effective method for avoiding multipulse was put forward.3) Dispersion-matched condition of PMLFL was determined by spectrum sideband measuring. By changing the length of total single mode fiber (SMF) in the ring cavity, self-starting 520.5fs mode-locked pulse train at 25MHz repetition rate with 1.81mW output power was obtained in PMLFL which was centered at 1558.4nm with 29.5nm 3dB spectrum width.4) Aσ-cavity PMLFL was presented. Experimentally, self-starting 670.5fs mode-locked pulse train at 6.2MHz repetition rate with 1.5mW average output power was obtained, which was centered at 1562.3nm with 19.2nm 3dB bandwidth.2. Supercontinuum (SC) generated in nonlinear fiber.1) The influences of nonlinear effects of fiber, fiber parameters and pump pulse parameters on SC spectrum were studied numerically.2) SC was generated in different fibers and the experimental results were analyzed and compared.3) SC generated from the combination of fiber with different characteristics was researched. It was showed that the spectrum quality was mainly affected by dispersion and nonlinear characteristics of the first segment fiber. Dispersion shifted fiber (DSF) was connected after highly nonlinear fiber (HNLF) to optimize spectral shape. Widely broadened SC spectra were generated in the combination of 120m HNLF+4.57km DSF+2.04km single mode fiber (SMF) with 55 mW average pump power. 140.6nm 3 dB bandwidth spectrum on the left side of pump wavelength was obtained. About 4.1μm longitudinal resolution could be obtained around ~1300nm by using this SC spectrum as the optical source of optical coherence tomography system.3. Frequency domain OCT (FDOCT) system.1) Fourier diffraction theorem for tomography which based on the first order Born approximation and measuring principle of FDOCT system were studied.2) A FDOCT system was put up based on the basic principle of FDOCT. Dielectric mirror and three-layer-covered-glass were used as OCT samples respectively. It was found that the vertical resolution of the system reached 16.4μm or even more precise by analyzing the depth information of the point detected from the interference signal.更多还原