电子薄膜与集成器件国家重点实验室，电子科技大学 光电科学与工程学院，四川 成都 611731
采用非线性放大环形镜的被动锁模机制，通过加入手动可调滤波器及光纤光栅等实现单波长光谱输出，设计出一种可调谐纳秒脉冲光纤激光器。纳秒矩形脉冲由被动锁模掺铒光纤激光器产生，激光器的腔长为430 m，脉冲的重复频率为465 kHz。被动锁模光纤激光器中实现可调谐脉冲输出的关键器件包括宽带锁模器件和可调谐滤波器，其中宽带锁模器件是反射式的非线性放大环形镜。结果表明，当激光器工作在1560 nm，泵浦功率为400 mW时，脉冲宽度为10.58 ns，单脉冲能量为70.28 nJ。激光器的可调谐范围为1523.4 nm～1575 nm，比此前报道的可调谐范围要宽10 nm。
光纤激光器 可调谐 锁模 纳秒脉冲 fiber laser tunable mode-locking nanosecond pulse
电子科技大学光电科学与工程学院，电子薄膜与集成器件国家重点实验室，四川 成都 611731
对谱域光学相干层析系统(SD-OCT)采用色散补偿方法进行优化，是提高系统成像质量的重要方式。本文提出了一种基于数值多项式拟合的色散补偿方法。该方法通过提取干涉信号的相位并解包裹，利用数值多项式对解包裹后的相位进行拟合，然后根据拟合出的高阶色散因子对干涉信号做相位补偿。本文利用SD-OCT系统测量出不同光程差位置处的轴向分辨率和信噪比，通过比较分析色散补偿前后系统的轴向分辨率及信噪比，来验证该方法的有效性和可靠性。结果表明，本文设计的色散补偿技术可以使系统具有良好的轴向分辨率，三阶多项式拟合相位的色散补偿方法在约1.5 mm的成像深度范围内有明显的优化效果。
谱域光学相干层析系统 色散补偿 分辨率 信噪比 成像质量 SD-OCT dispersion compensation polynomial fitting resolution imaging quality
1 电子科技大学光电科学与工程学院, 四川 成都 610054
2 中国科学院苏州生物医学工程技术研究所, 江苏 苏州 215163
眼底视网膜病变是大部分眼科疾病的来源。光学相干层析成像(OCT)具有无创性、成像安全快速等特点,在临床上被广泛用于眼科疾病的诊断。针对OCT视网膜三维图像因抖动产生的扭曲变形问题,提出一种基于曲线拟合的OCT视网膜三维重建图像去抖动方法,即通过预处理提取OCT视网膜图像的边界,再利用最小二乘法曲线拟合来计算各帧切片图像的偏移量。结果表明:所提方法对OCT视网膜三维重建图像扭曲变形具有明显的校正作用。
测量 曲线拟合 三维重建 去抖动 光学相干层析成像 视网膜
Author Affiliations
Abstract
1 School of Optoelectronic Information, University of Electronic Science and Technology of China, No. 4, Section 2, North Jianshe Road, Chengdu 610054, P. R. China
2 College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu 610225, P. R. China
3 Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, P. R. China
4 School of Electronic and Communication Engineering, Guiyang University, Guiyang 550005, P. R. China
5 Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, P. R. China
6 Chinese Academy of Sciences, The Key Laboratory on Adaptive Optics, Chengdu 610209, P. R. China
According to the speckle feature in Optical coherence tomography (OCT), images with speckle indicate not only noise but also signals, an improved wavelet hierarchical threshold filter (IWHTF) method is proposed. At first, a modified hierarchical threshold-selected algorithm is used to prevent signals from being removed by assessing suitable thresholds for different noise levels. Then, an improved wavelet threshold function based on two traditional threshold functions is proposed to trade-off between speckle removing and sharpness degradation. The de-noising results of an OCT finger skin image shows that the IWHTF method obtains better objective evaluation metrics and visual image quality improvement. When α=0.2, β=5.0 and K=1.2, the improved method can achieve 9.58 dB improvement in signal-to-noise ratio, with sharpness degraded by 3.81%.
Optical coherence tomography wavelets speckle Journal of Innovative Optical Health Sciences
2018, 11(3): 1850012
Author Affiliations
Abstract
1 State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054, China
2 School of Electronic and Communication Engineering, Guiyang University, Guiyang 550005, China
3 Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China
4 College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu 610225, China
In this work, we investigate the methods to improve the performance of the swept source at 1.0 μm based on a polygon scanner, including in-cavity parameters and booster structures out of the cavity. The three in-cavity parameters are the cavity length, the rotating speed of the polygon scanner, and the in-cavity energy. With the decrease of cavity length, the spectrum bandwidth becomes wider and the duty cycle becomes higher. With the increase of the rotating speed of the polygon, the spectrum bandwidth becomes narrower, and the duty cycle becomes lower but the repetition rate becomes higher. With more energy in-cavity, the spectrum bandwidth becomes wider and the duty cycle becomes higher. The booster structures include the buffered structure, secondary amplifier, and dual-semiconductor optical amplifier configuration, which are used to increase the sweep frequency to 86 kHz, the output power to 18 mW, and the tuning bandwidth to 131 nm, respectively.
Optical coherence tomography Lasers, tunable Semiconductor lasers Photonics Research
2017, 5(3): 03000245
电子科技大学光电信息学院, 四川 成都 610054
分析了崖层在单行载流子光电探测器（UTC-PD）中的作用，以及其对UTC-PD的3 dB带宽的影响。研究结果表明，崖层使得异质结处电场强度增加，且电场向吸收区延伸，使电子在吸收区的渡越时间和积累程度降低，从而导致3 dB带宽和饱和电流增加；崖层的掺杂浓度和厚度都会对3 dB带宽产生显著的影响；当崖层厚度与掺杂浓度的乘积一定，且收集区保持耗尽时，随着崖层厚度的增加（掺杂浓度减小），3 dB带宽下降，但是，只要崖层的厚度不是太厚(通常为十几纳米到几十纳米)，则无论是改变崖层厚度，还是改变掺杂浓度，3 dB带宽的下降都可以忽略不计，即3 dB带宽基本相等。
探测器 崖层 单行载流子 3 dB带宽
研究了导带不连续性对InGaAsP/InGaAs单行载流子高速光探测器(UTCPD)的3dB带宽的影响。研究结果表明，由于导带不连续性的存在，使得3dB带宽降低。导带不连续性越大，3dB带宽越低。通过增加隧穿系数、收集层厚度、收集层掺杂浓度和减小吸收层掺杂浓度可以在一定程度上消除导带不连续性带来的不利影响。研究结果还表明，增加隧穿系数、收集层厚度和减小吸收层掺杂浓度这三种方法在消除导带不连续性不利影响的同时又有各自的缺点，而适当增加收集层掺杂浓度是最为有效的一种方式。该研究结果可以为UTCPD的设计提供理论指导，特别是采用UTC结构的波导型光电二极管。
高速光探测器 导带不连续性 单行载流子 带宽 highspeed photodetector conduction band discontinuity unitravelingcarrier bandwidth
Author Affiliations
Abstract
1 Institute of Optics and Photonics, National Laboratory on Fiber Optic Communication Networks &
2 Advanced Optical Communication Systems, Shanghai Jiao Tong University, Shanghai 200240
In conventional rational harmonic mode-locking, optical pulse trains with the repetition rate of (pn+1)f_(c) are generated when the modulation frequency of the in-cavity modulator is set at f_(m)=(n+1/p)f_(c), where n and p are both integers, f_(c) is the fundamental cavity frequency. In this paper, we report that rational harmonic mode locking phenomenon takes place in the fiber lasers when the modulation frequency is set at f_(m)=(n+2/p)f_(c). The pulse generations are experimentally demonstrated when the numerator of the rational corresponds to 2 in 5th and 7th order rational harmonic mode-locking.
140.4050 mode-locked lasers 140.3510 lasers fiber Chinese Optics Letters
2004, 2(9): 09534
