The Photon-Number Distribution of the Lasers with Binomial Pump Model

A method on how to take into account pump statistics and spontaneous atomic decays when calculating the photon-number distribution of lasers in photon-number representation is presented. The intracavity phonon-number and extracavity photocount distributions with binomial pump and spontaneous atomic decays are calculated. In two limit cases, the results of calculations transit respectively to the photon-number distributions of systems with common Poissonian pump and regular pump, and both with the spontaneous atomic decays being suppressed.     

Quantum Nondemolition Measurement of Photon-Number Distribution for a Two-Mode Field

We propose a quantum nondemolition measurement of the photon-number distribution for a two-mode cavity field. In the scheme two sequences of two-level atoms interact dispersively with the respective cavity modes and resonantly with two classical fields, and then are detected continually. The field finally reduces to a two-mode Fock state. The probability of collapsing to a given Fock state is determined by the initial photon-number distribution. The scheme can be easily generalized to a field with N modes.     

泵浦统计,原子相干性及多单光子激光场光子数压缩效应

利用朗之万方程理论证明，在多单光子激光振荡的线性区域，泵浦统计、原子相干性及原子位相起伏可导致光子数压缩效应。     

算符a^K本征态热迭加光场的光子数统计分布

利用密度矩阵方法，导出了光子湮没算符高次幂ａ＾Ｋ（ｋ≥２）本征态热迭加光场光子数统计分布的一般表达式，讨论了热噪声对非经典光场态光数统计分布振荡行为的影响。     

Photon-Number Tomography of Multimode States and Positivity of the Density Matrix

For one-mode and multimode light, the photon-number tomograms of Gaussian quantum states are explicitly calculated in terms of multivariable Hermite polynomials. Positivity of the tomograms is shown to be a necessary condition for positivity of the density matrix.     

Spectrally Adjustable Picosecond Dye Laser Pulses Generated with Nanosecond Nitrogen Lasers

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Detecting a Photon-Number Splitting Attack in Decoy-State Measurement-Device-Independent Quantum Key Distribution via Statistical Hypothesis Testing

Measurement-device-independent quantum key distribution (MDI-QKD) is innately immune to all detection-side attacks. Due to the limitations of technology, most MDI-QKD protocols use weak coherent photon sources (WCPs), which may suffer from a photon-number splitting (PNS) attack from eavesdroppers. Therefore, the existing MDI-QKD protocols also need the decoy-state method, which can resist PNS attacks very well. However, the existing decoy-state methods do not attend to the existence of PNS attacks, and the secure keys are only generated by single-photon components. In fact, multiphoton pulses can also form secure keys if we can confirm that there is no PNS attack. For simplicity, we only analyze the weaker version of a PNS attack in which a legitimate user’s pulse count rate changes significantly after the attack. In this paper, under the null hypothesis of no PNS attack, we first determine whether there is an attack or not by retrieving the missing information of the existing decoy-state MDI-QKD protocols via statistical hypothesis testing, extract a normal distribution statistic, and provide a detection method and the corresponding Type I error probability. If the result is judged to be an attack, we use the existing decoy-state method to estimate the secure key rate. Otherwise, all pulses with the same basis leading to successful Bell state measurement (BSM) events including both single-photon pulses and multiphoton pulses can be used to generate secure keys, and we give the formula of the secure key rate in this case. Finally, based on actual experimental data from other literature, the associated experimental results (e.g., the significance level is 5%) show the correctness of our method.     

Modulation Induced Low-Frequency Fluctuations in Semiconductor Lasers with Optical Feedback and Their Suppression by Synchronous Modulation

Modulation induced low-frequency fluctuations (LFFs) of a semiconductor laser in the presence of optical feedback are investigated. LFFs are controlled to a synchronous oscillation when an appropriate modulation very close to the resonance frequency of the external cavity is applied to the injection current. The dependence of the frequency locking on the modulation frequency and depth is studied.     

Phase-sensitive nonclassical properties of photon-added-then-subtracted coherent squeezed states

We investigate the nonclassical properties of the photon-added-then-subtracted coherent squeezed state(PASCSS) via the sub-Poissonian statistics,the photon-number distribution,and the negativity of the Wigner function.It is found that the PASSCS is a superposition state of D(β)S(ζ)|0>,D(β)S(ζ)|1>,and D(β)S(ζ)|2>.We find that the Mandel Q parameter,the photon-number distribution,and the negative volume of the Wigner function of the PASCSS are all periodic functions of the compound φ-θ/2 with a period π involved with squeezing and displacement parameters.     

Influence of Phase-Shift on Side-Mode Suppression Ratio in Fiber Grating External Cavity Semiconductor Lasers

Effects of system parameters on the side-mode suppression ratio of the fiber grating external cavity semiconductor laser are investigated by the numerical method, and the variation of the side-mode suppression ratio is discussed. It is found that an excellent anti-reflection coating provides the significant reduction of the variation due to the phase shift and the change of the internal cavity length. The laser with the low anti-reflection coating, the high coupling efficiency and the short cavity will exhibit the excellent side-mode suppression ratio.     

Oscillation behaviour in the photon-number distribution of squeezed coherent states

From the normally ordered form of the density operator of a squeezed coherent state(SCS),we directly derive the compact expression of the SCS’s photon-number distribution(PND).Besides the known oscillation characteristics,we find that the PND is a periodic function with a period of π and extremely sensitive to phase.If the squeezing is strong enough,and the compound phase which is relevant to the complex squeezing and displacement parameters are assigned appropriate values,different oscillation behaviours in PND for even and odd photon numbers appear,respectively.     

Quantum nondemolition measurement of photon—number distribution for a weak cavity field with resonant atoms

We propose a quantum nondemolition measurement of the photon-number distribution for a weak cavity field with no more than two photons. The scheme is based on the resonant interaction of atoms with the cavity field, and thus the required interaction time is much shorter than that using dispersive interaction. This is important in view of decoherence. Our scheme can also be used to generate even and odd coherent states for a weak cavity field with resonant atoms.     

激光器稳定性分析

本文介绍一种分析激光器稳定性特性的线性化方程方法。由Poincar啨非线性理论 ,首先将非线性速率方程在阈值处线性化 ,再由线性方程的系数矩阵的特征量给出四种稳定性类型     

纵向泵浦Tm：YAG激光器的理论研究

用准三能级系统速率方程对纵向泵浦Ｔｍ：ＹＡＧ激光器的阈值，效率和激活介质最佳长度进行了计算和分析，讨论了温度对Ｔｍ：ＹＡＧ激光器输出特性的影响。     

Dynamic Memory Model Based on the Fermi–Pasta–Ulam Interacting Spectra Generated by Interconnected Ring Lasers

A model of a memory system consisting of three neuron networks based on three interacting ring lasers–neurons is suggested. The neurons are considered as carriers of the Fermi–Pasta–Ulam recurrence spectra described within the framework of the modified Zabusky and Kruskal approach. The interaction of the FPU spectra is studied using both fluid and optical models. Physical evaluation shows that such a memory system does not have apparent quantity limits for the information stored.     

LD侧面泵浦固体激光器泵浦光分布模拟

利用Gauss光束通过光学系统的变换规律,将激光二极管阵列发出的光作为Gauss光束处理.应用矩阵光学方法,解析分析与数值模拟相结合,给出了激光二极管阵列侧面泵浦棒状固体激光介质内泵浦光的强度分布.比较了侧面环绕激光二极管阵列数量不同时泵浦光分布的均匀性;以及考虑准直系统后,不同准直透镜焦距时,晶体内泵浦光半径的大小;同时针对泵浦光在晶体内聚焦时的情况进行了简单讨论.将半解析法与光线追迹法所得结果进行了比较,二者十分相近,但前者计算要简单得多.     

数值模拟980nm锥形半导体激光器输出特性

具有高功率及高亮度激光特性的锥形半导体激光器在激光加工、自由空间通信、医疗等领域具有广泛的应用前景.本文基于广角差分光束传播法(WA-FD-BPM),对980 nm锥形半导体激光器进行了仿真模拟,详细分析了不同结构参数(脊形区刻蚀深度、锥形角度、不同脊形区/锥形区长度比、锥形区刻蚀深度、前腔面反射率)对器件光束质量和P...     

Bimodal Nanoparticle Size Distributions Produced by Laser Ablation of Microparticles in Aerosols

Silver nanoparticles were produced by laser ablation of a continuously flowing aerosol of microparticles in nitrogen at varying laser fluences. Transmission electron micrographs were analyzed to determine the effect of laser fluence on the nanoparticle size distribution. These distributions exhibited bimodality with a large number of particles in a mode at small sizes (3–6-nm) and a second, less populated mode at larger sizes (11–16-nm). Both modes shifted to larger sizes with increasing laser fluence, with the small size mode shifting by 35% and the larger size mode by 25% over a fluence range of 0.3–4.2-J/cm². Size histograms for each mode were found to be well represented by log-normal distributions. The distribution of mass displayed a striking shift from the large to the small size mode with increasing laser fluence. These results are discussed in terms of a model of nanoparticle formation from two distinct laser–solid interactions. Initially, laser vaporization of material from the surface leads to condensation of nanoparticles in the ambient gas. Material evaporation occurs until the plasma breakdown threshold of the microparticles is reached, generating a shock wave that propagates through the remaining material. Rapid condensation of the vapor in the low-pressure region occurs behind the traveling shock wave. Measurement of particle size distributions versus gas pressure in the ablation region, as well as, versus microparticle feedstock size confirmed the assignment of the larger size mode to surface-vaporization and the smaller size mode to shock-formed nanoparticles.     

Dynamics of Two-Photon Lasers with A Atomic Level Configuration

We derive the dimensionless dynamic equations of two-photon lasers with A atomic level configuration by using the quantum Langevin equation method with the considerations of atomic coherence and injected classical fields. Then we analyze the stability and the chaotic dynamics of the two-photon laser by calculating the bifurcation diagram and the maximum Lyapunov exponent （MLE）. Our results show that the Lorenz strange attractors and one-focus strange attractors can exist in this system, and the chaos can be induced or inhibited by the injected classical fields via Hopfbifurcations or crises, while the atomic coherence induces chaos via crises, and inhibit chaos via Hopf bifurcation or crises.     

光栅耦合外谐振腔调谐的半导体量子级连激光器

本文研究了由InGaAs/InAlAs材料组成,波长为4.6和5.1微米的量子级连中红外半导体激光器的光栅外耦合谐振腔的特性。在温度是80K时波长可调制宽度是激光中心波长的1.5%左右。对于这两个激光器而言,它们的波长可调制宽度随温度升高而减低。被调制的单模激光器的输出光功率是几个毫瓦,激光的谱线宽度是1到2个微米。激光阈值电流随波长缓慢变化,然而激光输出效率在短波长时更加优化。