单模激光混沌特性的理论研究

在光学中，激光是产生双稳态、振荡、混沌等多种自组织现象的典型例子。本文采用非线性理论分析了单模激光的混沌特性，对描述单模激光的非线性动力学方程进行了稳定性分析，从而确定了系统失稳后进入混沌态的分歧点，并利用计算机进行了数值计算，给出了系统呈现混沌态的模拟结果。计算机数值模拟的结果与理论分析的结果相吻合。     

Measurement of flow fluctuations in single longitudinal mode pulsed dye laser

A simple technique had been demonstrated for measuring flow-induced fluctuations in the single longitudinal mode (SLM) pulsed dye laser. Two prominent frequency components of 10.74 Hz and 48.83 Hz were present in the output of the Nd:YAG-pumped SLM dye laser. The flow-induced frequency component of 48.83 Hz was present due to the revolution per minute of the motor attached to the magnetically coupled gear pump. The time average bandwidth of 180 MHz has been obtained for this SLM dye laser. The effect of pump pulse energy on the bandwidth of the SLM dye laser was studied. The bandwidth of the SLM dye laser was increased to 285 MHz from 180 MHz, when the pump pulse energy was increased to 0.75 mJ from 0.15 mJ for a constant dye flow velocity of 0.5 m/s.     

Enhanced emission of single quantum dot formed by interface fluctuations in photonic-crystal microcavities

We fabricated photonic-crystal (PhC) microcavities tuned to GaAs quantum dots (QDs) formed by interface fluctuation for the first time and observed the spontaneous emission enhancement in a weak coupling regime. A QD is a very thin GaAs quantum well (QW), and its interface steps exhibit quantum dot-like behavior. The emission intensity from the PhC cavity was stronger than that from the area where no PhC pattern was fabricated and the overall shape of the photoluminescence (PL) agreed with the cavity mode calculated with the three-dimensional (3D) finite-difference time domain (FDTD) method. The spontaneous emission enhancement factor was 10.     

单模激光混沌系统的可视化模型及仿真研究

提出了一种直接用仿真软件建立单模激光混沌系统可视化模型的方法。分析了单模激光系统的混沌特性 ,并对单模激光系统的混沌同步与控制进行了仿真研究。该方法的优点是无需用传统的程序代码对模型和算法进行编程 ,且可实现混沌光学系统建模及仿真分析的全程可视化 ,是研究光学动力学系统的一种简便、有效的新方法     

Conductance fluctuations and quantum chaotic scattering in semiconductor microstructures

We review recent experiments on aperiodic conductance fluctuations in ballistic GaAs/AlGaAs microstructures in the shape of a stadium billiard and a circle with point-contact leads, measured at millikelvin temperatures. Much of the observed behavior can be analyzed within a semiclassical approach to quantum chaotic scattering. After a brief review of the Landauer-Buttiker formulation of coherent transport, a variety of novel experimental phenomena and comparisons to semiclassical theory are presented. In particular, we discuss quantum-enhanced backscattering, the power spectrum of conductance fluctuations, crossover to the high-magnetic-field and tunneling regimes, and an application allowing the rate of phase-randomizing scattering to be measured in chaotic ballistic microstructures.     

Mesoscopic fluctuations of nonlinear conductance of chaotic quantum dots

The nonlinear dc conductance of a two-terminal chaotic cavity is investigated. The fluctuations of the conductance (anti)symmetric with respect to magnetic-flux inversion through multichannel cavities are found analytically for arbitrary temperature, magnetic field, and interaction strength. For few-channel dots the effect of dephasing is investigated numerically. A comparison with recent experimental data is provided.     

Nonequilibrium diagrams of a single quantum well laser

We studied the operation of a single quantum well laser by examining the tested device with a scanning electron microscope (SEM) working in differential voltage contrast (DVC) mode. A MOCVD-grown structure consists of 60Å of In_0.2Ga_0.8As, positioned between layers of GaAs, each 100Å thick. The specially cleaved laser structure was forward biased to get through the inverse population, threshold, and stimulated emission mode. In various modes of operation of the laser, thein situDVC profiling of the quasi-Fermi energy across the device was performed. The intensity of the laser emission was simultaneously measured by a detector positioned in the SEM chamber. Starting with an equilibrium energy diagram of an unbiased laser, we reconstructed the complete nonequilibrium energy diagrams from the experimental profile of quasi-Fermi levels.     

Analysis of polarization mode dispersion fluctuations in single mode fibres due to temperature

We have studied the effect of temperature on the birefringence and polarization mode dispersion PMD in standard single mode fibre (SSMF) with elliptical core cross section by using numerical computations. On the basis of simulation we have concluded that PMD fluctuates more rapidly than the stress-induced birefringence. In addition, DGD is inversely proportional to temperature.     

Surface mode coupling in GaAs/AlGaAs laser diodes - a new concept for a single laser mode emission

We present a new concept for a single mode laser diode. This concept is based on the strong coupling between the laser mode propagating in the active region and a surface mode on top of the laser diode. By this we achieve both a single-mode-like operation and a surface emission. We present a model which explains qualitatively the emission spectrum and which allows an optimization with respect to real single mode operation. The major advantage of this type of laser diode is its simple fabrication.The device utilizes the well established technique of the conventional striped laser and requires no regrowth.     

Suppression of interference by quantum fluctuations in a Josephson interferometer with a single small junction

The geometric inductance of a single-junction interferometer at which quantum fluctuations suppress interference and the Coulomb blockade of Cooper pairs is observed is found.     

Linewidth of a detuned single mode laser near threshold

The linewidth of a detuned single mode laser is calculated. Using the Fokker-Planck equation method, the problem is reduced to a nonhermitian eigenvalue problem. Numerical results near threshold and an approximate linewidth formula are given.     

A single mode flashlamp-pumped dye laser

A flashlamp-pumped dye laser capable of single transverse and longitudinal mode operation is described. The maximum untuned power output is 2 MW cm^-2, TEM₀₀ mode. By employing three intracavity Fabry—Pérot etalons, a minimum spectral width of 4 MHz, stable to within 12 MHz, has been obtained.     

Homogeneous broadening in a 0.63 μm single mode He-Ne laser

The expression for inversion density in a gas laser includes an additional term if one allows elastic and/or resonant collisions among the active atoms. This term is a function of the line parameters ₁, and ₂ and describes the effect of homogeneous broadening on the saturated gain profile. Measurements of these parameters show that the homogeneous broadening in a 0.63 m He-Ne laser plays an important role.     

Observation of chaotic polarization attractors from a graphene mode locked soliton fiber laser

We have demonstrated an all-fiber passively mode locked erbium-doped fiber laser(EDFL) based on graphene–polyvinyl-alcohol film. By watchfully adjusting the polarization controller, two different polarization attractors, including polarization locked vector solitons and a circular attractor, can be observed. This is first time, to the best of our knowledge, to explore the dynamics polarization attractors exhibited by a vector soliton generated from an EDFL based on graphene.     

Stability of a detuned single mode homogeneously broadened ring laser

We study analytically the influence of detuning on the properties of a homogeneously broadened single mode ring laser. In the good cavity domain the stationary output is stable. In the bad cavity domain the stationary output becomes unstable via a Hopf bifurcation. Near line center this Hopf bifurcation is subcritical, leading to unstable small amplitude oscillations. Far from line center this Hopf bifurcation is supercritical and leads to stable small amplitude output.     

Delay signatures in the chaotic intensity output of a quantum dot laser with optical feedback

Delay identification from the chaotic intensity output of a quantum dot laser with optical feedback is done using numerical and information theoretic techniques. Four quantifiers, namely autocorrelation function, delayed mutual information, permutation entropy and permutation statistical complexity, are employed in delay estimation. A detailed comparison of these quantifiers with different feedback rates and delay is undertaken. Permutation entropy and permutation statistical complexity are calculated with different dimensions of symbolic reconstruction to obtain the best results.     

Fluctuation theory of detuned single mode laser

Spectral analyses of fluorescence in unannealed and annealed alkali chlorides, bromides and iodides with lead are compared with the results of absorption measurements and of ultramicroscopic and electron-microscopic study of these crystals. The relations (3)–(8) which are of the Mollwo-Ivey type were obtained for the positions of the emission bands. The precipitates show their own luminescence.     

1028 nm single mode Ytterbium-doped fiber laser

An efficient Ytterbium-doped fiber laser (YDFL) operating at 1028 nm is demonstrated using a fiber Bragg grating (FBG). The Ytterbium-doped fiber (YDF) is drawn from Yb₂O₃-doped preform, fabricated through deposition of porous layer of composition SiO₂-GeO₂ by the MCVD process in conjunction with a solution doping technique. The fabricated YDF has a 0.1 mol % of Yb₂O₃ in the core, a Ytterbium ion lifetime of 1.1 ms, an absorption of 7.65 dB/m at 976 nm. The fiber laser has the maximum efficiency of 51% with pump power threshold of 19 mW using a FBG in conjunction with a Fresnel reflection to form a linear cavity resonator. The efficiency and threshold are better compared to the similar YDFL configuration using a commercial YDF.