Design of diamond-shape photonic crystal fiber polarization filter based on surface plasma resonance effect

A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber(PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio(ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems.     

啁啾sinc取样光纤光栅研究

提出了一种特殊的取样光纤光栅：啁啾sinc取样光纤光栅.研究表明,对于均匀光纤光栅进行啁啾sinc取样,可以实现色散斜率补偿和获得精确的反射波长数控制;对啁啾光纤光栅进行啁啾sinc取样,则能够实现色散和色散斜率的同时补偿,并且可以进行精确的波长数控制及获得各信道一致的反射率.利用啁啾sinc取样光纤光栅,可以对各种传输光纤进行色散和色散斜率的补偿.     

Numerical investigation of slow solitons in Bragg gratings with a hyperbolic tangent apodization

This paper numerically and analytically investigates the formation and propagation motion of optical soliton in the Bragg grating.We choose the fibre Bragg grating with hyperbolic tangent apodization in the middle section in order to obtain slower solitons.Optical fibre soliton but not Bragg grating soliton is used as input pulse in the discussion,which is much more approximate to the light source for the practical purpose.We discuss in detail the effects of the soliton’s velocity with some parameters in the process of transmission.The results show that by choosing special parameters,one can make the soliton slow-down with a little distortion and energy decay and obtain tunable time-delay on a small scale.     

Highly sensitive digital optical sensor with large measurement range based on the dual-microring resonator with waveguide-coupled feedback

We propose a novel high-performance digital optical sensor based on the Mach-Zehnder interferential effect and the dual-microring resonators with the waveguide-coupled feedback. The simulation results show that the sensitivity of the sensor can be orders of magnitude higher than that of aconventional sensor, and high quality factor is not critical in it. Moreover, by optimizing the length of the feedback waveguide to be equal to the perimeter of the ring, the measurement range of the proposed sensor is twice as much as that of the conventional sensor in the weak coupling case.     

中国学生在学习英语语音上的困难及对策

由于中英文之间不同的发音系统，中国学生在学习英语语音时常常面临很多难题。为了帮助中国学生更好地学习英语语音，教师要善于总结学生在语音学习过程中所遇到的具体困难，采用交际教学法，即以交流的方式进行教学，不能只让学生学习发音规则或练习句型。     

快速成型技术及发展

快速成型技术是一项发展迅速的高新制造技术,具有传统制造技术不可替代的优点,拥有广泛的应用市场。文中根据国内外最新的研究资料,对快速成型技术的工作原理、具体的工艺形式,以及优点和应用进行了较为详实的介绍和论述。     

匹配光纤光栅温度传感解调系统

实验了一种基于一维调节器的光纤光栅静态温度(温度缓变)探测系统。在系统中,一维调节器与步进电机相连,步进电机由PC(计算机)通过PLC(可编程逻辑控制器)进行控制,匹配光纤光栅被固定在一维调节器上用来解调增敏光纤光栅传感器探测到的温度信号,匹配光栅的Bragg周期可通过调节一维调节器进行控制,其透射的光信号经光电检测电路检测并与调节架形成闭环控制。实验测得,在10℃~70℃范围内系统温度传感探测精度为±0.3℃。     

单模光纤色散的解析形式

根据波导标量解本征值方程及其递推关系,提出一种利用Gloge关系求解单模光纤中波导色散的理论方法,给出了色散的解析形式,通过分析归一化传输常数的近似解与精确解间的差别论证了这种解析法具有精确求解的计算精度,给出普通单模光纤（G．652）光纤色散的实验数据,并与计算的色散解析解曲线加以比较,二者达到极好的吻合,利用所得到的结果,分析了数值微分法和经验公式的计算精度。     

折射率直流分量调制对光纤Bragg光栅的影响

从耦合模理论出发,推导了折射率直流分量调制函数与光纤Bragg光栅相位之间的关系式,分析了折射率直流分量调制对光纤Bragg光栅时延特性的影响.利用传输矩阵法进行了数值仿真,仿真结果与理论分析一致.在理论分析基础上,提出采用同一块均匀相位掩膜版灵活制作具有不同线性或非线性时延特性的啁啾光纤光栅的方法,可用于高速光通信系统中不同色散和色散斜率的补偿.     

铋/铒共掺光纤荧光特性实验研究

分别用980nm和830nm的半导体激光器作为泵浦源激发铋/铒共掺光纤,采用前向和背向泵浦方式分析放大的自发辐射谱特性.实验结果表明:随着泵浦功率的增大,荧光强度显著增强.利用980nm半导体激光器,采用前向泵浦方式可激发以1 142nm和1 536nm为中心的两个辐射带,以1 142nm为最高辐射峰的3dB带宽是141nm,以1 536nm为最高辐射峰的3dB带宽是29nm.利用830nm半导体激光器,采用前向泵浦方式可激发以1 421nm为中心的荧光谱,3dB带宽是447nm.980nm和830nm激光器分别前向泵浦铋/铒共掺光纤时,随着光纤长度的增加,荧光先增强后减弱;分别背向泵浦铋/铒共掺光纤时,随着光纤长度的增加,荧光强度先逐渐增强后保持稳定.在25~80℃的温度范围内,铋/铒共掺光纤的荧光强度几乎不受温度的影响.使用980nm和830nm泵浦源同时激发铋/铒共掺光纤,结果表明铋/铒共掺光纤的发光中心具有相对独立性,发光范围存在部分重叠.