基于一维耦合腔光子晶体的声光可调谐平顶滤波器的研究

本文利用一维耦合腔光子晶体,提出了一种声光可调谐平顶滤波器.该滤波器利用声光效应,通过改变超声波频率使一维耦合腔光子晶体透射谱的平顶滤波器的中心波长产生漂移,从而实现可调谐的滤波功能.基于传输矩阵法和声光效应理论,建立了这种平顶滤波器的理论模型;利用COMSOL软件,对平顶滤波器的矩形度、通带带宽、插入损耗、可调谐特性、加工精度进行仿真研究.研究结果表明,通过施加频率为6-11 MHz的超声波,可实现通带带宽为5-6 nm及中心波长在1514-1562 nm范围内可调谐的平顶滤波器;在可调谐范围内通带带宽内插入损耗不超过2.23 dB,最低仅为0.78 dB,矩形度最低可达1.4;加工误差在±10 nm内平顶滤波器的中心波长、矩形度、插入损耗、通带带宽出现的偏差很小.该平顶滤波器具有易于设计和集成、通带平坦、可调谐范围宽、通带带宽稳定、插入损耗低、品质因素高的特点,在光开关、可调谐光纤激光器、光纤传感等光通信领域有重要应用.     

基于光纤简并四波混频的可调谐波长转换器的优化设计

分析了光纤零色散波长、光纤长度、信号光频率及泵浦功率对基于光纤简并四波混频的可调谐波长转换器调谐带宽和转换效率的影响.结果表明对应不同的零色散波长都存在唯一的最优信号光频使得调谐带宽达到最大,进而推导了最优信号光频和最大调谐带宽的解析表达式,给出了提高此类器件调谐带宽和泵浦效率,减少调谐中输出信号功率起伏的优化设计方法.与以往实验结果相比优化后同等泵浦功率下调谐带宽可增加10 nm,若保证同样的调谐带宽则可将泵浦功率降低4.6 dB.     

改型Wollaston棱镜的光程差及其特性分析

简述了改型Wollaston棱镜的偏光结构和分光机理;应用波法线追迹法分析了光在棱镜中的传播规律与波矢轨迹;推导出了任意入射面内、以任意角入射时光在棱镜中的传播方向及出射点坐标;给出了改型Wollaston棱镜中o光和e光光程差的理论表达公式;采用计算机模拟,给出了光程差随入射角、入射面与棱镜主截面的夹角、棱镜结构角及波长的变化曲线,并对其变化特性进行了深入的分析. 该研究对偏光棱镜的理论研究具有普遍的指导意义,为偏振分光器件及干涉成像光谱仪的研制和应用提供了重要的理论依据和实践指导. 关键词： 改型Wollaston棱镜 波法线追迹法 光程差     

旋转光纤圆起偏器的特性分析

基于旋转光纤耦合模理论,对窄带和宽带旋转光纤圆起偏器的特性进行了计算分析.研究了注入光的偏振态、光纤固有线双折射和旋转速率对窄带圆起偏器最小工作长度的影响,并借助多包层光纤的分析方法,分析了旋转光纤各参量变化对宽带圆起偏器工作带宽的影响.结果表明:窄带圆起偏器的最小工作长度与光纤固有线双折射和光纤旋转速率有关,而与注入光的偏振态无关|改变光纤旋转速率可调节宽带圆起偏器的工作带宽,改变应力区到纤芯的距离可改变宽带圆起偏器的中心波长.     

基于光纤简并四波混频的可调谐波长转换器的优化设计

分析了光纤零色散波长、光纤长度、信号光频率及泵浦功率对基于光纤简并四波混频的可调谐波长转换器调谐带宽和转换效率的影响．结果表明对应不同的零色散波长都存在唯一的最优信号光频使得调谐带宽达到最大,进而推导了最优信号光频和最大调谐带宽的解析表达式,给出了提高此类器件调谐带宽和泵浦效率,减少调谐中输出信号功率起伏的优化设计方法．与以往实验结果相比优化后同等泵浦功率下调谐带宽可增加10nm,若保证同样的调谐带宽则可将泵浦功率降低4．6dB．     

液体透镜的透射波前特性研究

液体透镜是一种新型光学元件,通过改变表面曲率而调整光焦度。液体透镜的透射波前质量会影响成像质量,将液体透镜应用于精密光学系统需要探明其透射波前变化特性。通过理论和仿真分析液体透镜通光孔径内不同高度入射光线的光程差随曲率半径的变化,以及光程差对光焦度的敏感性,以此研究光瞳空间内光程差微变的一致性。分别测量液体透镜在零、正、负光焦度下的透射波前,通过分析实验数据验证液体透镜的光程差微变的一致性。实验结果表明:光程差微变的空间最大差异约为0.22λ～0.36λ,空间分布离散程度约为0.01λ～0.02λ,得出液体透镜随电流微变产生的光程差微变一致性较好,为液体透镜在精密光学系统中的应用和像差补偿提供了技术支撑。     

计算机模拟在高温超导滤波器调谐中的应用

本文通过使用电磁模拟软件对滤波器的滤波特性和电磁场分布进行了研究,模拟结果显示通过插入介质钉可以在基本不影响滤波器带内特性的条件下实现中心频率可调.在研究了螺钉对谐振器和谐振器间耦合的影响后,我们对一5节前向耦合型带通超导滤波器的调谐特性进行了模拟计算,其中心频率为3030MHz,带宽220MHZ,中心频率可调范围+20MHz.对另一4节C形滤波器调谐计算显示,其中心频率2190MHz,带宽55MHz,中心频率可调范围±4MHz.     

四种典型旋转型干涉仪的光程差分析和仿真

从经典迈克尔逊干涉仪结构出发,主要分析了四种旋转型干涉仪的结构特点,以及干涉仪的光程差与旋转角度之间的关系。通过设定参数,使用干涉仪光程差表达式对这四种旋转型干涉仪的光程差作了模拟仿真。在干涉仪光程差表达式基础上,对这四种旋转型干涉仪的旋转速度与旋转角度之间关系也作了模拟仿真。通过对干涉仪光程差的模拟仿真和比较,能够直观地反映出干涉仪光程差与旋转角度之间的关系。在要求运动速度误差控制在3%以内情况下,讨论了四种旋转型干涉仪的旋转角度范围。通过对干涉仪的光程差分析和仿真,这对于研究干涉仪的结构和性能分析具有很好的借鉴意义。     

外部光注入混沌激光器产生超宽带微波信号的研究

利用外部光注入混沌激光器产生了完全符合美国联邦通信委员会关于室内无线通信频谱限定的超宽带(UWB)微波信号.基于外部光注入光反馈半导体激光器的速率方程组,理论研究了外部及内部参量对半导体激光器输出混沌UWB脉冲信号的影响.研究表明,UWB信号的-10 dB带宽随着光注入强度、注入失谐量以及线宽增强因子的增大而增大,随着激光器偏置电流的增大而减小.同时,UWB信号的中心频率在5–8 GHz范围内变化.在实验中,通过设定其他参量和调节光注入强度,得到中心频率及带宽可调谐的混沌UWB微波信号,传输速率达到500 Mbit/s.实验结果与理论分析相符合. 关键词： 半导体激光器 混沌激光 光生微波技术 超宽带信号     

横向受激布里渊散射的抑制

 从非线性光学的耦合波理论出发，结合流体力学的连续性方程，建立了光学元件中窄带泵浦的横向受激布里渊散射的二维理论模型，并在此基础上，利用数值模拟考察泵浦光带宽增加对受激散射过程的影响。研究表明:在一定的条件下，当泵浦光带宽略大于布里渊线宽时，受激散射过程的Stokes增益将显著降低；带宽越大，Stokes增益降低得越多；当带宽大于20GHz时，可以抑制横向受激布里渊散射带来的不良影响。另外，当带宽一定时，调制频率的改变也会影响受激散射过程，可以通过数值模拟确定最佳的调制频率。     

Low-noise, tunable diode laser for ultra-high-resolution spectroscopy

We demonstrate the excellent spectral properties of a diode laser setup that combines good tunability with superb short-term frequency stability and controllability. It is based on merging two concepts, the diode laser with resonant optical feedback and the grating stabilized diode laser. To characterize the short-term performance we beat two essentially identical diode lasers and find a short-term linewidth of ~11 kHz. Phase locking between these lasers is achieved with a servo bandwidth as small as 46 kHz, although an analog phase detector is used that requires subradian residual phase error. Despite small phase error detection range and small servo bandwidth, cycle-slip-free phase locking is accomplished for typically many 10 min, and the optical power is essentially contained in a spectral window of less than 20 mHz relative to the optical reference. Due to the excellent performance this laser concept is well suited for atomic or molecular coherence experiments, which require phase locking of different lasers to each other, and as part of a flywheel for optical clocks.     

基于双折射晶体的光交叉波分复用器

光交叉波分复用器能够把一组DWDM光信号分解成两组奇偶信道输出 ,或反之。双折射晶体的设计关健部分由两个光轴成 45°的波片A和B组成。入射光信号经过偏振分束器和偏振元件处理后 ,在A波片中形成o光、e光并产生位相差。在B波片中再次分解并发生干涉形成奇偶信道光输出。A波片厚度决定位相差从而决定输出信道间隔。用两片光轴垂直或相同但不同材料的波片按一定的厚度组合代替波片A可消除输出频率间隔的温度漂移。基于双折射晶体的设计是实现商用化光交叉波分复用器的有效途径。     

Theoretical analysis of self-phase locking in a type II phase-matched optical parametric oscillator

We analyze a doubly-resonant type II phase-matched optical parametric oscillator that includes an intracavity waveplate for inducing mutual injection locking between the signal and the idler. The intracavity waveplate provides a linear coupling between the normally orthogonally polarized signal and idler fields and allows for mode locking at frequency degeneracy. Under mode locked conditions the signal–idler phase difference is locked and the optical parametric oscillator becomes self-phase locked. The signal–idler phase can be adjusted by changing the operating point within the locking range. Two self-phase locked modes with different thresholds and signal–idler phases are possible. Characteristics of the self-phase locked regime are presented for different linear coupling strengths.     

基于场变换的毫米波半波片设计

极化转换是电磁波调控的重要研究方向之一.本文基于场变换理论提出一种宽入射角的宽带毫米波半波片.基于等效媒质理论,该半波片可由亚波长厚度的两种介电常数不同的材料周期性排布后旋转45°得到.通过设计控制两种材料的介电常数、高度比值以及整个半波片的厚度可以在毫米波段实现极化转换的功能,此设计具有低损耗和高转化效率的特点.此半波片能实现横电波与横磁波的相互转换以及圆极化波的相互转换,极化转换-3 dB相对带宽达49%.仿真和实测结果相符,验证了该半波片宽带高效的极化转换效果.在入射角为60°时,极化转换-3 dB带宽依然能够达到36%左右.     

On the use of stimulated Brillouin scattering as a calibration method for group delay and differential group delay measurements

We propose a novel group delay and differential group delay calibration method for polarization-dependent optical spectral characterization measurements. The calibration method is based on the dispersive nature of stimulated Brillouin scattering and its polarization dependent spectral response. The main advantage of the calibration method is its tunability in wavelength, bandwidth and magnitude, what makes it suitable for different measurement setups.     

Neurosensory tissue morphology with intraoperative optical fiber probe in aqueous medium

In this work, the author has demonstrated cross-sectional imaging of a retina of an ex vivo fish sample using a common path frequency domain optical coherence tomography at 0.8 μm range. It has been introduced that an integrated surgical hypodermic needle fiber probe can stabilize the flexible glass optical fiber and provides a close proximity to the specimen for intraoperative image guiding. In addition, the light source characteristics were matched to the common path interferometer while operating in the aqueous medium (saline solution), in order to mimic the in vivo condition, in that it shows greater bandwidth and shorter center wavelength for larger input current or output power to sustain the appropriate level of coherence reference peak by the partial reflection at the glass fiber probe interface.     

Multiple parameter tuning of the bandwidth, wavelength and attenuation of a fiber-based acousto-optic tunable filter

In this paper we presented a method, which will allow multiple parameter control of the 3-dB bandwidth, center notch wavelength and attenuation level in a fiber-based acousto-optic tunable filter (AOTF). The method basically involves the variation of the interaction length, RF frequency and RF power on a single-fiber device to achieve multiple parameters tuning of the optical filter. The acousto-optic (AO) interaction inside a single-mode fiber (SMF) was studied theoretically and experimentally.     

A multi-band atomic candle with microwave-dressed Rydberg atoms

Stabilizing important physical quantities to atom-based standards lies at the heart of modern atomic, molecular and optical physics, and is widely applied to the field of precision metrology. Of particular importance is the atom-based microwave field amplitude stabilizer, the so-called atomic candle. Previous atomic candles are realized with atoms in their ground state, and hence suffer from the lack of frequency band tunability and small stabilization bandwidth, severely limiting their development and potential applications. To tackle these limitations, we employ microwave-dressed Rydberg atoms to realize a novel atomic candle that features multi-band frequency tunability and large stabilization bandwidth. We demonstrate amplitude stabilization of microwave field from C-band to Ka-band, which could be extended to quasi-DC and terahertz fields by exploring abundant Rydberg levels. Our atomic candle achieves stabilization bandwidth of 100 Hz, outperforming previous ones by more than two orders of magnitude. Our simulation indicates the stabilization bandwidth can be further increased up to 100 kHz. Our work paves a route to develop novel electric field control and applications with a noise-resilient, miniaturized, sensitive and broadband atomic candle.     

可变可转单波片偏振控制器研究

基于PLZT波片的相对相位延迟量可变性和其折射率椭球主光轴的可转性,提出后反馈单个PLZT可变可转波片偏振控制器.采用模拟退火算法进行扰动寻优,仿真结果显示这种控制器是有效的：能将任意输入偏振态转换为稳定的线偏振光而其光强达到总光强的98%以上,在控制过程中相移能在限定范围内变化,避免了由复位重置可能引起的波动.     

Analyzing wavelength behavior of a cubic phase mask imaging system based on modulation transfer function

The wavefront coding technology is an effectively method for extending the depth of field. However, the phase delayed by the phase mask changes with light wavelength, and the chromatic aberration is caused by chromatic dispersion of the optical elements. The modulation transfer function (MTF) of the cubic phase mask (CPM) system is derived with considering the axial chromatic aberration and optical path difference variation with wavelength, and the wavelength behavior of CPM system is analyzed in details. We yield that the MTF is approximately wavelength invariant within a certain frequency bandwidth, and the bandwidth is nearly inverse proportional to wavelength and varies with axial chromatic aberration. The effect induced by dispersion of the CPM material is very weak. If the CPM system is illuminated by wideband spectral light and the ACA exists, then the frequency bandwidth may become narrower than the monochromatic case, and the position of image sensor can be relocated to balance frequency bandwidth among all wavelengths.