Generating EPR-entangled mechanical state via feeding finite-bandwidth squeezed light

Einstein–Podolski–Rosen(EPR) entanglement state is achievable by combining two single-mode position and momentum squeezed states at a 50:50 beam-splitter(BS). We investigate the generation of the EPR entangled state of two vibrating membranes in a ring resonator, where clockwise(CW) and counter-clockwise(CCW) travelling-wave modes are driven by lasers and finite-bandwidth squeezed lights. Since the optomechanical coupling depends on the location of the membranes, CW and CCW can couple to the symmetric and antisymmetric combination of mechanical modes for a suitable arrangement, which corresponds to a 50:50 BS mixing. Moreover, by employing the red-detuned driving laser and tuning the central frequency of squeezing field blue detuned from the driving laser with a mechanical frequency, the squeezing property of squeezed light can be perfectly transferred to the mechanical motion in the weak coupling regime. Thus, the BS mixing modes can be position and momentum squeezed by feeding the appropriate squeezed lights respectively, and the EPR entangled mechanical state is obtained. Moreover, cavity-induced mechanical cooling can further suppress the influence of thermal noise on the entangled state.     

Passive harmonic mode locking of twin-pulse solitons in an erbium-doped fiber ring laser

We report on the experimental observation of passive harmonic mode locking of twin-pulse solitons in an erbium-doped fiber ring laser. Experimental investigations on the passive harmonic mode locking of both the single-pulse and the twin-pulse solitons revealed that, apart from the gain recovery and acoustically induced soliton interactions, the global soliton interaction mediated through an unstable CW lasing in the laser cavity also plays an important role in the formation of the state in the laser.     

56 MHz重复频率端泵SESAM连续波锁模Nd∶YVO4激光器

为了增大皮秒注入种子激光的能量,获得较高的激光放大效率和信噪比,关键是要在保持较高的平均锁模激光功率下实现连续波锁模激光器的低重复频率运转。通过选取五镜折叠激光谐振腔腔型和参数设计,克服了随着腔长增加损耗加大而导致的激光锁模不稳定的困难。分析了较长腔长条件下工作物质和SESAM光斑尺寸的大小和变化,及其对激光器稳定性的影响。由于SESAM饱和工作和稳态条件的能量要求,在激光谐振腔调整过程中,对应臂长的光程互补变化。实验中采取腔长和晶体热控制方式,优化了激光谐振腔的工作参数,实现了脉冲能量10.7 nJ,重复频率56 MHz,平均功率1.2 W的SESAM连续波锁模激光输出。     

How white noise generates power-law switching in bacterial flagellar motors

The clockwise (CW) or counterclockwise (CCW) spinning of a bacterial flagellar motor is controlled by the concentration [Y] of a phosphorylated protein, CheY-P. Representing the stochastic switching behavior of the motor by a dynamical two-state (CW and CCW) model, whose energy levels fluctuate in time (t) as [Y](t) fluctuates, we show that temporal fluctuations in [Y](t) can generate a power-law distribution for the durations of the CCW states, in agreement with recent experiments. Correlations between the duration times of nearby CCW (CW) intervals are predicted by our model, and shown to exist in the experimental data and to affect the power spectrum for motor switching.     

基于半导体环形激光器的高速双向双信道混沌保密通信

提出了一种利用半导体环形激光器(SRLs)的新型高速双向、双信道混沌保密通信系统. 在该系统中, 首先利用交叉双光反馈对驱动激光器的顺时针模式和逆时针模式的混沌延时特征进行抑制. 然后将此混沌信号注入到一对响应激光器对应的顺时针模和逆时针模中, 以实现带宽的增强及混沌同步. 最后基于响应激光器之间的混沌同步, 实现高速率、双向、双信道的混沌保密通信. 通过对驱动激光器在交叉双光反馈作用下的混沌特性、以及响应激光器在不同条件下的同步特性进行了相关理论和仿真研究, 结果表明: 驱动激光器在合适的交叉双光反馈作用下可以产生延时特性被良好隐藏的顺时针模式和逆时针模式混沌信号; 在该混沌信号的注入下, 响应激光器输出的混沌信号带宽可以得到明显增强; 通过设置合适注入强度值和频率失谐值, 响应激光器之间可实现高质量的等时混沌同步. 最后, 对系统的双向、双信道混沌保密通信特性进行了讨论. 当10 Gbit/s信号传输距离为10 km时, 解调信息Q因子值仍可保持在6以上.     

All-optical set-reset flip-flop based on frequency bistability in semiconductor microring lasers

The electric field of the modes of semiconductor microring lasers (SMRLs) in the presence of bus waveguide reflections are linear combinations of the clock wise (CW) and the counter clock wise (CCW) electric fields. The mode structures can be controlled by the waveguide reflection coefficients. The power ratio and phase difference of the CW and CCW fields of one mode is proportional to the ratio of the reflection coefficients of the left and right waveguides. It is shown that the degenerate CW and CCW modes in the presence of bus waveguide reflections are split into two modes with different frequencies. Employing these new modes, SMRL can be used as an element to design flip-flops used in photonic integrated circuits. For a symmetric structure, the inter-frequencies of CW and CCW waves relating to each mode can be considered as the output of the optical flip-flop. Output of asymmetric mode is zero while the symmetric mode has a nonzero output.     

连续简并量子拍频激光器的工作特性

采用饰缀(dressed)原子方法,讨论了被共振微波场驱动的三能级原子系统简并量子拍频激光器的增益系数,小信号增益系数、饱和光强、阈值条件和稳态光强.     

Rotational power loss of magnetic steel sheets in a circular rotational magnetic field in CCW/CW directions

This paper presents rotational power loss properties of magnetic steel sheets under high flux density conditions using two-dimensional vector magnetic properties measurement. Recently it was reported by some research groups that the magnetic power loss measured in a counter clockwise (CCW) rotating field differed from that in a clockwise (CW) rotating field. This phenomenon was only observed in case of higher magnetic flux density excitation condition. We call this the CCW/CW problem. To clarify the reasons why the disagreement exists in the CCW/CW direction, we have examined angle errors of H- and B-coils by using geometrical, optical and magnetic methods. Then we compensated the measured vector components including different signals due to the angle errors. In the components of irremovable small angle error, we have also used the measured field strength waveforms in CCW/CW conditions. We have applied the compensation method to measurement of a grain-oriented electrical steel sheet.     

Locking of a flashlamp-pumped dye laser at small injection powers

Experiments have been carried out on the injection-locking of a pulsed dye laser to an argon-laser-pumped CW dye laser of 50 MHz linewidth without longitudinal mode matching. With the inclusion of a Fabry-Perot etalon within the ring laser arrangement of the pulsed laser, the initiation of injection locking and saturation occur at low injection powers.     

First-Order-Like Transition in Inhomogeneously Broadened Two-Mode Ring Laser Gain-Noise Model

An inhomogeneously broadened two-mode ring laser gain-noise model taking account of both full saturation effects and multiplicative noise induced by gain fluctuations is investigated. By using a corresponding Fokker-Planck equation and perturbation theory proposed by Graham et al. the joint stationary distribution for light intensities is obtained. It is found that a first-order-like transition occurs when laser is operated off resonance.     

Diode-end-pumped continuous-wave Nd:YAG laser at 946 nm of single-frequency operation

We report a diode-end-pumped continuous-wave (CW) Nd:YAG laser at 946 nm of single frequency operation. A ring laser resonator was designed and the output coupler transmission was optimized based on the investigation of the influence of the output coupler transmission on the thermal lens effect induced by energy-transfer upconversion. A maximum output power of 1.5 W CW single-frequency laser at 946 nm was achieved. The stability of the laser output power was better than ±1% in the given four hours.     

半导体光放大器引起的串扰及其抑制技术

由于半导体光放大器(SOA)的增益饱和效应,在波分复用系统中.每个信道的增益受到复用的其它信道的影响.SOA引起的各信道之间的串扰严重限制了其应用.理论研究了SOA增益饱和效应引起的信道间串扰.数值模拟了多路信道复用时系统的误码率随复用信道数和光功率的变化情况,发现随着复用信道数的增加SOA增益饱和引起的信道间串扰越来越严重.对SOA中串扰的抑制方法进行了理论和实验研究.数值模拟发现连续光注入可以抑制输出功率的波动,从而减小误码率,当复用10个信道时,连续光注入可以使功率代价减小2 dB;实验验证了两信道的40 Gb/s系统中,注入连续光可以减少SOA引起的信道间串扰.     

Resonance asymmetry phenomenon in waveguide-type optical ring resonator gyro

The intensity output of a silica waveguide ring resonator (WRR) was found to show an asymmetric resonance characteristic. To further analyze and better design the resonator micro optic gyro (RMOG) with a waveguide-type ring resonator, in-depth research of the characteristics of the resonance asymmetry is fully developed for the first time, to the best of our knowledge. Four possible sources of the resonance asymmetry are analyzed and their respective contributions are compared. These four error sources are differential normal mode losses in the coupler, the backscattering induced noises, the polarization fluctuations and the optical Kerr effect. The differential normal mode loss is suspected to be the major contributor to the observed resonance asymmetry in the fabricated silica WRR. Asymmetric resonance curve produces a large output bias error in the RMOG based on the phase modulation technique, which is related to the modulation frequency differences between the CW and CCW lightwaves. Theoretical analysis shows that replacing the reflector WRR with a transmitter one is helpful to eliminate the effect of the different normal mode losses in the coupler on the resonance asymmetry.     

Small signal gain and loss measurement of a CW Nd:YAG laser using an antiresonant ring interferometer

An antiresonant ring (ARR) interferometer configuration is introduced for the characterization of a continuous wave (CW) Nd:YAG laser output. The output of the ARR device is precisely characterized todetermine the gain and loss of a laboratory CW Nd:YAG laser by using the Findlay-Clay approach. TheARR arm is then experimentally arranged inside the cavity of an arranged high power side-pumped CWNd:YAG laser. A coated beam splitter with 50–50% reflectivity at normal incidence is placed inside thecavity to provide a wide range of reflectivity from 0 to 100%. This is performed by a rotatable stage and tilting the beam splitter by 10°with the steps of 0.05. By changing the input electrical power of the laser pump the variation of the output laser power is monitored for 20 individual reflectivity of ARR arm.Average pump threshold power of about 180 W is obtained. With the help of the derived equations and obtained threshold power, small signal gain and loss associated with the emerging beam is estimated. It is verified that the former is very dependent to the input parameters. Laser efficiency is also measures 5.6% which is quite comparable with the reported values.     

掺铒光纤中的双稳态现象的研究

在以掺铒光纤为增益介质的环形光纤激光器中观察到了光学双稳态现象,定性分析了双稳态形成的机理,即掺铒光纤不同位置分别存在增益饱和和吸收饱和,而且吸收饱和有着更低的饱和阈值。通过理论衍生的公式对增益特性曲线进行了拟合,并结合增益特性曲线对光双稳态的产生给出了定量的解释。     

双模环型激光增益噪声模型的非线性效应

讨论了一个双模环型激光增益噪声模型，其中考虑了完全饱和效应且乘法噪声由增益系数涨落引起。在共振及两模具有相同泵参数时，获得了光强联合定态分布的精确解析表达式。通过与现有的双模激光摸型（其中乘法噪声由损失系数涨落引起）的比较，发现乘法噪声系数的非线性效应减弱了乘法噪声给激光光强统计性质带来的反常特性，并且这种减弱随着乘法噪声增强或损失系数减小而愈加明显。     

气体激光中的对流效应

介质流动对于气体激光功率输出的大幅度提高,起着决定性的作用。分析表明:表征连续波激光的饱和强度和光功率密度(或小信号增益系数)均随流速而非线性地增大,并趋向各自的极限值;饱和强度的增加量约不超过10倍;光功率密度的大幅度增加起因于激励能在气流中的累积。这些结论与常用理论关于饱和强度随流速线性且无限地增大,光功率密度增大起因于饱和强度增大的结论并不相同。本文关于饱和强度随气流渡越时间变化的定量结果与流动CO₂气体激光饱和强度的测试结果相符。 关键词：     

Dual-wavelength S-band erbium-doped fiber double-ring laser

We propose and demonstrate an S-band CW dual-wavelength erbium-doped fiber (EDF) dual-ring laser using a compound-ring filter (CRF) with various coupling losses inside the gain cavity. Employing a ring filter combined within the cavity, the fiber laser can lase a dual wavelength without any filter inside the ring loop. The dual-wavelength output exhibits a good performance having optical side-mode suppression ratios (SMSRs) of 31.6 and 31.8 dB and output powers of ?9.6 and ?9.3 dBm at 1505.58 and 1506.43 nm, respectively, when the coupling loss is 30% inside the cavity. In addition, the output stabilities of the dual-wavelength laser have also been analyzed.     

Mode selection in CW laser with homogeneously broadened gain

The gain calculated for a laser with ring and Fabry-Perot resonators respectively is given in a general formulation which shows clearly the influence of the spatially inhomogeneous saturation due to the standing wave pattern and the resulting Bragg scattering. When selecting a single mode in a Fabry-Perot resonator, the losses necessary to quench the modes are equal to those losses which the selected mode suffers due to the self-induced Bragg grating in the active medium. In a unidirectional ring laser, the losses only need exceed the gain of additional separate gain reservoirs of the modes. Also possible reasons are dealt with which cause stable bidirectional operation in a ring laser with homogeneously broadened gain.     

Theory and experiment of CW dye laser injection locking and its application to second harmonic generation

High-power single-mode operation of a cw ring dye laser has been obtained by injection of cw single-mode radiation. The intracavity power of this system was used to generate tunable single-mode uv radiation by frequency doubling in a temperature phase-matched ADA crystal: up to 45 W intracavity fundamental power and up to 70 mW extracted uv power have been observed. A theoretical treatment of the injection locked cw ring dye laser system is given for the stationary state. Expressions for the intracavity intensities as a function of the small-signal gain and the saturation intensity are derived.