Soliton Lattice and Gas in Passive Fiber-Ring Resonators

We consider multisoliton patterns in the model of a synchronously pumped fiber-loop resonator. An essential difference of this system from its long-line counterpart is that, due to the finite length, dynamical regimes may be observed that would be unstable in the infinitely long line. For the case when the effective instability gain, produced by competition of the modulational instability (MI) of the flat background and losses, is small, we have consistently derived a special form of the complex Ginzburg-Landau equation for a perturbation above the continuous wave (cw) background. It predicts bound states of pulses with a uniquely determined ratio of the pulse width to the separation between them. Direct numerical simulations have produced regular soliton lattices at small values of the feeding pulse power, and irregular patterns at larger powers. Evidence for a phase transition between the lattice and gas phases in the model is found numerically. At low power, the width-to-sep aration ratio as found numerically proves to be quite close to the analytically predicted value. We also compare our results with recently published experimental observations of MI-stimulated formation of a pulse array in a mode-locked fiber laser.     

Temperature dependence of pressure broadening of the N = 1− fine structure oxygen line at 118.75 GHz

The absorption profile of the N = 1− fine structure line of oxygen was recorded by a resonator spectrometer at a frequency range of 110-130 GHz at atmospheric pressure and different temperatures ranging from −21 °C up to +22 °C. Analysis of the observed line shape allowed determination of the temperature dependence of the line pressure broadening. The measured value of the temperature exponent is n = 0.74(5) for self-broadening. Consistency of the measurements is supported by simultaneous measurements of the line intensity, the line mixing parameter and the line center frequency, and by comparison of obtained values with previously known data.     

Chalcogenide glass photonic crystals

All-optical switching devices are based on a material possessing a nonlinear optical response, enabling light to control light, and are enjoying renewed interest. Photonic crystals are a promising platform for realizing compact all-optical switches operating at very low power and integrated on an optical integrated circuit. In this review, we show that by making photonic crystals from a highly nonlinear chalcogenide glass, we have the potential to integrate a variety of active devices into a photonic chip. We describe the fabrication and testing of two-dimensional Ge₃₃As₁₂ Se₅₅ chalcogenide glass photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to post-tune the devices using the material photosensitivity. In one proposal we hope to introduce a double-heterostructure microcavity using the photosensitivity alone.     

基于半圆形与矩形谐振腔耦合结构的Fano共振

设计了一种基于金属-介质-金属波导的半圆形谐振腔与矩形谐振腔的耦合结构,采用有限元方法研究了该结构的传播特性.结果表明:透射光谱中产生一个类似Fano共振线型的共振谷,该Fano共振由半圆形谐振腔的宽谱共振和矩形谐振腔的窄谱共振相互耦合所导致.变化谐振腔的结构参量,发现该Fano共振谷位置依赖于矩形谐振腔的几何参量,而对两谐振腔相对位置的微小移动不敏感;同时,改变两谐振腔的并联方式,研究了两种衍生结构的传播特性,发现这些结构均可产生明显的Fano共振.此外,通过在谐振腔中填充不同折射率的介质材料,研究了三种结构基于Fano共振效应的折射率传感特性,其折射率敏感度最高达到750 nm/RIU.研究结果可为未来芯片上基于表面等离极化激元波导的高灵敏折射率传感器的设计提供理论依据.     

Full investigation of the backscattering in resonator fiber optic gyro

Resonator Fiber optic gyro (RFOG) is a high accuracy inertial rotation sensor based on the Sagnac effect. The optical fiber ring resonator (OFRR) is the key rotation sensing element. The backscattering characteristics of the OFRR are fully investigated. The Rayleigh backscattering dominates the backscattering spectrum with the input power below the threshold. High carrier suppression is crucial to reduce this Rayleigh backscattering error. Being different from the intrinsic Rayleigh scattering of the fiber, the stimulated Brillouin scattering (SBS) in the OFRR should be avoided. This is because the finesse and the resonance notch depth of the OFRR decrease for the pump depletion through the SBS process. The shot noise limited sensitivity (SLS) of the RFOG is improved by increasing the input power. Through analysis, it is found that the threshold input power is improved after phase modulation. The SLS of the RFOG is analyzed at different modulation parameters and its relevant SBS threshold. Accordingly, the optimized modulation frequency and the corresponding maximum input power are all obtained. A simple method of testing the frequency shift in the SBS is also proposed. In this method, the central frequency of the laser source is locked to the resonance frequency of the OFRR in one direction. A steady SBS light is observed and its frequency shift is measured together.     

四分之一波长锥形谐振管共振频率的研究

在热声发动机系统中,谐振管用来调节系统的超振频率.通常的四分之一波长谐振管由一段谐振管后面连接一个比较大的气体容积构成,与二分之一波长谐振管相比,在相同的起振频率下前者可以有相对短的管长.锥形谐振管除了调节频率外,还可以提高热声发动机输出压力波的压比.本文通过数值计算软件Fluent6.0中的K-ε湍流模型模拟了不同长度、不同的进出口直径的一系列锥形谐振管,得出了近似四分之一波长锥形谐振管的共振频率与其长度、锥度之间的关系,并初步与实验进行了对照.     

激光光腔内光场空间相干性的演化

基于激光谐振腔的理想开腔模型及其在空间频率域的相干模式理论,通过数值模拟分析了光腔内光场空间相干性的演化规律.以强度均匀的非相干光束为例,考虑了一系列硬边光阑的衍射效应对腔内光场相干性演化的影响,再现了腔内光场空间相干性的演化过程.数值计算结果表明：空间相干性随光场在腔内振荡次数的增加逐渐趋于完全相干,但对不同的光腔参量(如腔镜结构和腔镜面度),空间相干性在腔内的演化规律有很大的区别.     

Investigation of 2D-photonic crystal resonant cavity based WDM demultiplexer

In this attempt, Two Dimensional Photonic Crystal (2DPC) Quasi Square Ring Resonator (QSRR) based four channel demultiplexer is proposed and designed for Wavelength Division Multiplexing systems. The performance parameters of the demultiplexer such as transmission efficiency, passband width, line spacing, Q factor and crosstalk are investigated. The proposed demultiplexer is composed of bus waveguide, drop waveguide and QSRR. In the proposed demultiplexer, the output ports are arranged separately in odd and even number, where an odd number of ports are located on the right side and even number of ports are located on the left side of the bus waveguide that are used to reduce the channel interference or crosstalk. Further, the refractive index of rods around the center rod is increased linearly one to another in order to improve the signal quality. The resonant wavelengths of the proposed demultiplexer are of 1521.1?nm, 1522.0?nm, 1523.2?nm and 1524.3?nm, respectively. The footprint of the device is of 180.96?μm². Then, a four channel point to point network is designed and the proposed four channel demultiplexer is implemented by replacing a conventional demultiplexer. Finally, functional parameters of the network, namely, BER, receiver sensitivity and Q factor are estimated by varying the link distance. This attempt could create new dimensions of research in the domain of photonic networks.     

高频热声驻波发动机性能的实验研究

热声驻波发动机由于内禀的不可逆性而热效率较低,但其系统结构简单和可靠性高的优点使其仍具有一定的应用前景。目前,对高频驻波系统研究较少,搭建了一台高频热声驻波发动机,研究了板叠和谐振管对系统的重要作用,另外,初步探讨了系统热腔内的温度演化过程和稳定振荡时的温度分布特性,这对高频热声驻波发动机实验和数值研究具有指导意义。