Liu Tiegen

All-fiber optical modulator based on no-core fiber and magnetic fluid as cladding

An all-fiber optical modulator, which is composed of a piece of no-core fiber spliced between two sections of single-mode fibers and uses magnetic fluid (MF) as the cladding of the no-core fiber section, is proposed and investigated experimentally. Due to the tunable refractive index and absorption coefficient of MF, the output intensity can be modulated by controlling an applied magnetic field. The dependences of the modulator’s temporal response on the working wavelength, the magnetic field strength (H), and the MF’s concentration are investigated experimentally. The results are explained qualitatively by the dynamic response process of MF under the action of a magnetic field. The findings are helpful for optimizing this kind of modulator.

Research on Personal Identity Verification Based on Hand Vein Iris and Fingerprint

Personal identity recognition is vital to information society. Multimodal biometric is proved to be a promising authentication technique. The fusion recognition algorithms were studied based on three biometric traits, hand vein, iris and fingerprint. The independent feature extraction and matching modules were designed for each unimodal biometric to output matching scores. The fusion operation was implemented at the matching score level after score normalization. Simple average fusion recognition algorithm was finally employed to realize the personal identity authentication. The experiments were carried out to verify availability of the proposed algorithm. The experiment results showed the multimodal biometric system had much higher recognition accuracy than any unimodal biometric system.

Temporal overlap estimation based on interference spectrum in CARS microscopy

Coherent Anti-Stokes Raman Scattering (CARS) microscopy has attracted lots of attention because of the advantages, such as noninvasive, label-free, chemical specificity, intrinsic three-dimension spatial resolution and so on. However, the temporal overlap of pump and Stokes has not been solved owing to the ultrafast optical pulse used in CARS microscopy. We combine interference spectrum of residual pump in Stokes path and nonlinear Schrodinger equation (NLSE) to realize the temporal overlap of pump pulse and Stokes pulse. At first, based on the interference spectrum of pump pulse and residual pump in Stokes path, the optical delay is defined when optical path difference between pump path and Stokes path is zero. Then the relative optical delay between Stokes pulse and residual pump in PCF can be calculated by NLSE. According to the spectrum interference and NLSE, temporal overlap of pump pulse and Stokes pulse will be realized easily and the imaging speed will be improved in CARS microscopy.Coherent Anti-Stokes Raman Scattering (CARS) microscopy has attracted lots of attention because of the advantages, such as noninvasive, label-free, chemical specificity, intrinsic three-dimension spatial resolution and so on. However, the temporal overlap of pump and Stokes has not been solved owing to the ultrafast optical pulse used in CARS microscopy. We combine interference spectrum of residual pump in Stokes path and nonlinear Schrodinger equation (NLSE) to realize the temporal overlap of pump pulse and Stokes pulse. At first, based on the interference spectrum of pump pulse and residual pump in Stokes path, the optical delay is defined when optical path difference between pump path and Stokes path is zero. Then the relative optical delay between Stokes pulse and residual pump in PCF can be calculated by NLSE. According to the spectrum interference and NLSE, temporal overlap of pump pulse and Stokes pulse will be realized easily and the imaging speed will be improved in CARS microscopy.

Intravascular Frequency-domain optical coherence tomography imaging system

We present a Frequency-domain optical coherence tomography (FD-OCT) system for intravascular imaging. The whole system consists of 4 parts: imaging catheter (IC), motion controller (MC), optical engine (OE) and data acquisition and processing module (DAPM). By using swept laser source with 50 KHz sweep speed and high speed optical rotary jiont, we can get 100 frames per second (fps) and scan 20 mm vessel per second.

Multi-Bus Fiber Sensor Protection Network Operation With Robustness Analysis

This paper proposes a multi-bus fiber-optic sensor network, which could multiplex different types of fiber sensors, locate the failure position, and recover the sensing services of sensors in a network immediately and automatically to keep them working without being interrupted. It is composed of master and slave nodes, as well as working and backup fibers connecting them. We introduce the operation of the network and two light source distributions by explaining the internal structures of the master and slave nodes along with the sensor protection and the fault location process. Then, we analyze the probability distribution of working status for both distributions and propose a quantitative evaluation criterion called weighted average robustness for the robustness analysis of any fiber sensor network. Meanwhile, this paper demonstrates its feasibility by multiplexing three fiber sensor systems: a distributed fiber-optic vibration sensor based on dual Mach-Zehnder interferometer architecture; an optical frequency domain reflectometry sensor; and three Fiber Bragg Grating sensors in this network at the same time detecting different parameters. We test the performance of the network in three scenarios by fabricating failures of the sensing and backup fibers intentionally to prove the feasibility of the structure. Furthermore, all the status of the network will be uploaded to the human-computer interface of supervisory computer by the master processor through USB in real time. Operators can also control the network through the interface remotely.

Near-Infrared Spectroscopic Properties and Judd-Ofelt Theory Analysis of Er3+/Yb3+Co-Doped Fluoride Particles

制备了Er^3＋/Yb^3＋共掺氟化物基质颗粒并对其吸收光谱进行测试。研究了不同基质、煅烧温度以及不同的Er^3＋/Yb^3＋共掺比例对颗粒在980nm及1550nm波段附近吸收特性的影响。应用Judd-Ofelt（J-O）理论对样品光谱进行了分析,拟合得到强度参数为Ω2=9.9887,Ω4=2.7333,Ω6=0.4868。结果表明,样品通过高温热处理提高了声子辅助跃迁几率,提高了能量转化效率。Er^3＋/Yb^3＋以1：6比例混合共掺时吸收性能最好。J-O理论分析表明,氟化物颗粒有较低的声子能量,Er^3＋/Yb^3＋共掺氟化物材料具有较好的红外吸波特性,是一种很好的红外上转换材料。