The fractional oscillator as an open system

A dynamical system governed by equations with derivatives of non-integer order, such as the fractional oscillator, can be considered as an open (non-isolated) system with memory. Fractional equations of motion are obtained from the interaction between the system and the environment with power-law spectral density.     

Nonlinear dynamics study of an open resonant A-type system

A way resulting in lasing without inversion (LWI) in an open resonant A-type system from a nonlinear dynamics viewpoint is investigated. The destabilization of the non-lasing solution can occur not only through pitchfork bifurcation, giving rise to continuous wave LWI, but also through Hopf bifurcation,giving rise to self-pulsing LWI. This is much different from that of the corresponding closed resonant A-type system in which the destabilization of the non-lasing solution can occur only through pitchfork bifurcation. The effects of the unsaturated gain coefficient, cavity loss coefficient, atomic injection and exit rates on the two bifurcations are discussed.     

具有腔内光放大的单共振光参量振荡器

推导了描述稳态运行，具有腔内光放大的环形腔单共振光参量振荡器(ICOASRO)的功率特性的高斯光束理论.在这种结构的单共振光参量振荡器(SRO)中，适当地选择光放大器的参数，可以很大程度地降低单共振光参量振荡器的抽运阈值.在平均场近似下无二阶非线性交叉耦合作用的具有腔内光放大的环形腔单共振光参量振荡器的工作范围分成四个工作区域，且存在最小的单共振光参量振荡器的抽运阈值.文中的分析考虑了作为光放大器的激光增益介质的端面抽运特性，考虑了一般化单共振光参量振荡器的特性. 关键词： 单共振光参量振荡器 光放大 阈值     

Theory of resonant relativistic oscillator with nonuniform focusing field

The two-dimensional model of millimeter wave resonant O-type oscillator (as orotron, ledatron, resonant BWO, etc.) with a relativistic electron beam is analyzed. The selfconsistent nonlinear simultaneous equations have been obtained for the arbitrary space distribution of the magnetic guide field. The start generation characteristics are analyzed under small-signal conditions with an analytical solution taken for the case of inclined focusing magnetic field. It is found that the efficiency of electron-wave interaction appreciably depends on the focusing field strength and the relativistic mass factor. The results of numerical optimization of the guide field structure are presented to show possibility of improvement of the start characteristics of the oscillator.     

Theory of harmonic gyrotron oscillator with slotted resonant structure

A small signal theory is presented of the harmonic gyrotron oscillator with a slotted resonator. The magnetron-type wall structure has the effect of creating a strong harmonic field near the electron orbits and, as a result, greatly reducing the beam voltage and start-oscillation power required for harmonic operations. Characteristics of operation and methods of optimization are studied and numerically illustrated. It is shown that at a given harmonic the startoscillation beam power is lower at a lower beam voltage.     

Parametric oscillator based on a single-layer resonant metamaterial

We perform numerical simulations demonstrating parametric generation and oscillation processes in a single-layer of metamaterial composed of split ring resonators (SRRs). In general, a parametric resonance is achieved by introducing a time-modulation of one of the energy-storing parameters of a resonant system. An individual SRR is a resonant system that can be modeled as an RLC-circuit inductively coupled to an applied time-varying magnetic field. The relatively simple circuit model can be employed to establish the range of parameters providing the growth of parametric oscillations within the SRR medium. We relate the numerically predicted circuit parameters that ensure the buildup of parametric oscillations to those parameters expected to be available in a modified SRR medium, in which lumped element varactors integrated into the SRRs are used as modulable capacitance elements.     

2.5-GHz repetition-rate singly resonant optical parametric oscillator synchronously pumped by a mode-locked diode oscillator amplifier system

We report on an optical parametric oscillator (OPO) that is synchronously pumped directly by a diode laser. This laser is an actively mode-locked master-oscillator power-amplifier system that produces 20-ps pulses at 927 nm with a repetition rate of 2.5 GHz and an average power of 0.9 W. The OPO, which is a singly resonant device based on periodically poled lithium niobate, generates 7.8-ps pulses. The OPO threshold is 300 mW of average pump power, and the maximum average idler output power is 78 mW at a wavelength of 2100 nm. By changing the crystal temperature we can wavelength tune the output in the ranges 1530-1737 nm (signal) and 1986-2348 nm (idler). Rapid wavelength tuning of the OPO over 46 nm (signal) and 74 nm (idler) is achieved through tuning the cavity length over 28 microm by use of a piezoelectric transducer.     

Continuous radio-frequency tuning of an optoelectronic oscillator with dispersive feedback

We describe and demonstrate a novel technique for continuously tuning the frequency of a dual-loop-configuration optoelectronic rf oscillator. The rf tunability is obtained from a tunable diode laser and dispersive optical fibers. Results are presented for three ranges of frequency, centered at 550 MHz, 3 GHz, and 9 GHz. The frequency can be tuned electrically with constant rf power within a range of 0.1-1.9 MHz, depending on the center oscillation frequency. The tuning range can be increased eightfold through the use of highly dispersive fibers.     

2-mm resonance oscillator operating on the second spatial harmonic of a two-row periodic orotron structure

Orotron generation in the resonance BWO mode on the second spatial harmonic of a two-row periodic structure with the parameters l= 0.6 mm and d/l ～ 0.8 (l is the period and d is the groove width) has been observed for the first time. With a change in the voltage from 4.7 to 11 kV and the corresponding adjustment of the open resonator, frequency tuning in the range 94–140 GHz was obtained.     

带有反射腔的相对论返波管的数值模拟

 阐述了带有反射腔的相对论返波管的数值模拟研究。利用线性理论[1]设计了返波管的慢波结构，应用SUPERFISH软件设计了谐振反射器。用KARAT软件对谐振反射腔返波管进行了宏观粒子模拟，得到了优化的返波管结构参数，并研究了外加磁场对输出效率的影响。模拟结果表明：谐振反射腔不仅起到截止颈的作用，还有预调制的作用；在低外加磁场条件下，该返波管也能输出较高功率的微波。显示了其在重复频率工作方面的重要意义。     

分数阶质量涨落谐振子的共振行为

针对黏性介质引起的Brown粒子质量存在随机涨落以及阻尼力对历史速度具有记忆性等问题, 本文首次提出分数阶质量涨落谐振子模型, 以考察黏性介质中Brown粒子的动力学特性. 首先, 将Shapiro-Loginov 公式分数阶化, 使之适用于对含指数关联随机系数的分数阶随机微分方程的求解. 然后, 利用随机平均法和分数阶Shapiro-Loginov公式推导系统稳态响应振幅的解析表达式, 并据此研究系统的共振行为; 最后, 通过仿真实验验证理论结果的可靠性. 研究表明: 1)质量涨落噪声可诱导系统产生随机共振行为; 2)记忆性阻尼力可诱导系统产生参数诱导共振行为; 3)不同参数条件下, 系统表现出单峰共振、双峰共振等多样化的共振形式. 关键词： 黏性介质 质量涨落 阻尼记忆性 分数阶谐振子     

带有反射腔的相对论返波管初步实验研究

 阐述了带有反射腔的相对论返波管的初步实验研究进展。反射腔是一段不规则的圆波导,在相对论返波管中起到截止颈的作用。初步实验的结果为：外加磁场B_z =0.82T时,输出微波功率为170MW,微波频率8.874GHz,脉宽为10ns;外加磁场B_z =1.7T时,微波功率为370MW,频率与脉宽不变;根据辐射场功率密度分布判定传输模式为TM₀₁模。结果表明：带有反射腔的返波管在较低外加磁场下也能够工作。     

Low-pump-threshold continuous-wave singly resonant optical parametric oscillator

We describe a compact all-solid-state continuous-wave singly resonant optical parametric oscillator (SRO) with a minimal pump-power requirement. The SRO is based on periodically poled LiNbO(3) as the nonlinear material and is pumped by a 1-W diode-pumped Nd:YVO(4) minilaser at 1.064 microm . By exploiting the intracavity pumping technique in a 50-mm crystal, we have achieved SRO operation threshold at a diode pump power of only 310 mW.At 1 W of input diode power, the SRO delivers 70 mW of output power in the nonresonant idler at 3.66 microm , at a photon conversion efficiency of 55%. Multiparameter tuning of the SRO yields a signal wavelength range from 1.45 to 1.60 microm and an idler wavelength range from 3.16 to 4.02 microm in the mid infrared. The device is characterized by robust turnkey operation and long-term amplitude-stable performance.     

弹道靶开式微波谐振腔测量系统研究

The principle and experimental results of the open microwave resonant cavity measurement system were introduced. The models were steel ball models and the ball models coated with copper. The diameter of the models was 10mm. The models were launched in ballistic range. The model velocity was 5.44 km.s^-1. The wake electron density of the models was obtained. The experimental results presents that the response time of the open microwave resonant cavity measurement system was quicker than 1ms. The results showed the wake electron density ranged from 10⁹cm^-3 to 10¹¹cm^-3 could be achieved.     

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介绍了开式微波谐振腔测量系统的工作原理及试验结果,获得了Æ10mm钢球模型在6.65kPa干燥空气中以速度5.44km.s-1飞行时的尾迹电子密度测量结果,并且与国外弹道靶试验数据进行了比较。试验结果表明,该系统能够满足模型尾迹电子密度变化对测量系统响应时间的要求,能很好地反映尾迹电子密度变化细节,电子密度测量范围达到109~1011cm-3。     

Fiber-laser-pumped continuous-wave singly resonant optical parametric oscillator

We report on what is to our knowledge the first continuous-wave (cw) optical parametric oscillator (OPO) that is pumped by a tunable fiber laser. The OPO is singly resonant for the signal wave and consists of a 40-mm-long periodically poled LiNbO(3) crystal in a four-mirror ring cavity. At a pump power of 8.3 W provided by the wavelength-tunable Yb-doped fiber laser, the singly resonant OPO generates 1.9 W of 3200-nm cw idler radiation. The singly resonant OPO was tuned from 1515 to 1633 nm (signal) and from 3057 to 3574 nm (idler) by means of the crystal temperature and poling period. We obtained a wide idler tuning range, from 2980 to 3700 mn, by tuning the wavelength of the fiber laser from 1032 to 1095 nm.     

具有涨落质量的线性谐振子的共振行为

Brown运动中,环境分子的吸附能力使Brown粒子的质量存在涨落. 本文将这一质量涨落建模为对称双态噪声, 以考察其对系统共振行为的影响. 首先,利用Shapiro-Loginov公式和Laplace变换推导系统稳态响应振幅的解析表达式, 并根据相应数值结果, 研究系统的共振行为; 然后, 通过仿真实验对理论与实际的符合情况进行对比分析, 验证理论结果的可靠性及其对实际应用的指导意义. 理论结果和仿真实验均表明: 1) 系统稳态响应为频率与外部驱动相同的简谐振动; 2) 稳态响应振幅随外部驱动频率、振子质量、噪声强度及相关率的变化分别相应出现真实共振、参数诱导共振、随机共振现象; 3) 质量涨落噪声导致系统共振形式出现多样化现象, 包括单峰共振、单峰单谷共振、双峰共振等. 关键词： 质量涨落噪声 随机共振 双峰共振     

Passive cooling of a micromechanical oscillator with a resonant electric circuit

We cool the fundamental mode of a miniature cantilever by capacitively coupling it to a driven rf resonant circuit. Cooling results from the rf capacitive force, which is phase shifted relative to the cantilever motion. We demonstrate the technique by cooling a 7 kHz cantilever from room temperature to 45 K, obtaining reasonable agreement with a model for the cooling, damping, and frequency shift. Extending the method to higher frequencies in a cryogenic system could enable ground state cooling and may prove simpler than related optical experiments in a low temperature apparatus.     

带有反射腔的双频相对论返波管的粒子模拟

 设计了一种带有反射腔的能在X波段实现稳定双频输出的圆柱结构相对论返波管,采用2.5维相对论全电磁PIC粒子模拟软件行粒子模拟研究。仿真结果表明:在输入电压433 kV、引导磁场2.2 T的条件下,实现了9.53,10.09 GHz的双频稳定输出,平均输出功率340 MW,平均功率效率24.1%。