Theoretical analysis of self-phase locking in a type II phase-matched optical parametric oscillator

We analyze a doubly-resonant type II phase-matched optical parametric oscillator that includes an intracavity waveplate for inducing mutual injection locking between the signal and the idler. The intracavity waveplate provides a linear coupling between the normally orthogonally polarized signal and idler fields and allows for mode locking at frequency degeneracy. Under mode locked conditions the signal–idler phase difference is locked and the optical parametric oscillator becomes self-phase locked. The signal–idler phase can be adjusted by changing the operating point within the locking range. Two self-phase locked modes with different thresholds and signal–idler phases are possible. Characteristics of the self-phase locked regime are presented for different linear coupling strengths.     

Self-phase locking in 3-to-1 triply and doubly resonant optical parametric oscillators

We have observed self-phase locking in a triply and doubly resonant optical parametric oscillator containing a periodically poled lithium niobate crystal with a two-section grating that is designed for an exact 3-to-1 frequency division.     

A LiB_3O_5 optical parametric oscillator generating simultaneously two pairs of signals and idlers

Type I LiB_3O_5 optical parametric oscillator pumped by 0.532μm laser were investigated. The phasematching retracing behavior was confirmed and two pairs of signal-idler wavelengths were generate simultaneously. By comparing the angle and temperature tuning curves some significant features were found and then illustrated based on the phase mismatch factor.     

Stable operation of a cw optical parametric oscillator near the signal-idler degeneracy

The frequency stability of a cw optical parametric oscillator (cw OPO) near the signal-idler degeneracy has been studied. The strong tendency of a near-degenerate OPO to mode hop has been suppressed by using a bulk Bragg grating as a spectral filter in the OPO cavity. An experimental demonstration of stable parametric oscillation in a single longitudinal mode of the OPO cavity is reported, together with the capability of tuning the signal-idler difference frequency from 1 to 4 THz. The OPO has potential use in cw terahertz generation.     

振幅耦合动态网络中相邻结点间的相同步

研究用适当的量化指标来刻画动态网络的相同步,为此定义了新的量化指标:相邻结点的网络平均锁相值和网络平均相频差.动态网络结点选择的是多旋转中心的Lorenz混沌振子,对Lorenz系统进行柱面坐标变换,用振幅耦合方法构造动态网络.分别对星形网络和小世界网络进行了仿真计算,结果表明随着耦合强度的增大,网络中相邻结点的两个系统之间存在相同步现象,而且相同步行为与定义的量化指标之间存在较准确的对应关系.     

Phase synchronization from noisy univariate signals

We present methods for detecting phase synchronization of two unidirectionally coupled, self-sustained noisy oscillators from a signal of the driven oscillator alone. One method detects soft phase locking; another hard phase locking. Both are applied to the problem of detecting phase synchronization in von Kármán vortex flow meters.     

高功率微波振荡器的相位控制

基于相对论返波管振荡器,提出了一种小信号牵引相位控制的方法,通过外加小信号对振荡器起振过程的引导,实现对输出微波的相位控制。相比于传统的方法,该方法可以利用ns量级的脉冲在较宽的带宽和较低的注入功率下实现对高功率微波振荡器的相位控制。在X波段相对论返波管振荡器相位控制实验中,利用百kW级的小信号,实现了对GW级高功率微波的输出相位控制,相位抖动小于15。     

高功率微波振荡器的相位控制

基于相对论返波管振荡器,提出了一种小信号牵引相位控制的方法,通过外加小信号对振荡器起振过程的引导,实现对输出微波的相位控制。相比于传统的方法,该方法可以利用ns量级的脉冲在较宽的带宽和较低的注入功率下实现对高功率微波振荡器的相位控制。在X波段相对论返波管振荡器相位控制实验中,利用百kW级的小信号,实现了对GW级高功率微波的输出相位控制,相位抖动小于±15°。     

Hopping of chaotic dynamics in a doubly resonant parametric oscillator

We study a doubly resonant optical parametric oscillator where the pump can feed two pairs of signal-idler modes. We assume the presence of gain at the pump frequency. We investigate the various oscillation states of interest, namely, when only the first pair oscillates with the other pair having null amplitudes and vice versa. We demonstrate the exchange of dynamics between the mode pairs when the relevant parameters of the cavity, namely, the phase mismatch factors or the decay rates switch because of fluctuations. The exchange of dynamics is shown to be independent of the nature of dynamics, i.e. independent of whether the motion isn-periodic or chaotic. We also investigate the case where both the pairs can exhibit chaotic dynamics though these states are difficult to realize because of fluctuations.     

Theoretical study of misalignment analysis of the holophote and self-phase locking of axisymmetrical-structural CO2 laser

Based on the principle of the reflection-injection-locking of the external cavity, the self-phase locking mechanisms of the transversal mode and longitudinal mode are studied, respectively. And the excellent coherent beams are obtained. Unfortunately, the misalignment is inevitable, the new cavity axis is established by the 4×4 augmented matrixes when the holophote is in the misaligned state. The overlapping rate, the energy coupling coefficient and the fluctuation of the equiphase surfaces can be considered the main factors of the influence of the misalignment on self-phase locking. And then the distributions of the light intensity are given by the numerical simulation under the condition of the normal and misaligned states, respectively. The results have shown that the effect of the self-phase locking is excellent when the misaligned angle is in a range of tolerance.     

Passive mode locking with slow saturable absorbers

We give a comprehensive overview on passive mode locking of solid-state lasers with slow saturable absorbers, based on analytical and numerical calculations. For picosecond lasers, we present a simple equation to estimate the obtained pulse duration and compare the results to those for mode locking with fast saturable absorbers. We also discuss how much shorter the pulse duration can be compared to the absorber recovery time and present a simple rule. The effect of self-phase modulation is found to be qualitatively different compared to the case of a fast saturable absorber, and the effect of phase changes in the absorber is also discussed. Finally, we discuss various issues concerning soliton mode-locked lasers. Received: 20 July 2001 / Revised version: 28 September 2001 / Published online: 7 November 2001     

高性能注入锁相光电振荡器

提出一种基于注入锁定和锁相环技术的注入锁相光电振荡器.利用注入锁定来改善光电振荡器的近载频相噪以及杂散抑制度.将光电振荡器的输出信号与外注入源进行鉴相,通过锁相环来提升频率稳定性,并进一步改善光电振荡器的近载频相噪.实验结果表明:注入锁相光电振荡器在电滤波器中心频率为9.5GHz、3dB带宽为20 MHz和光纤环长度为6km的情况下,实现了输出信号频率为9.5GHz的单模振荡;当注入锁定带宽为1.98kHz时,光电振荡器输出信号在1kHz频偏处的相位噪声为-125dBc/Hz,在10kHz频偏处的相位噪声为-147dBc/Hz,杂散抑制度高于80dB,阿伦偏差接近1.37×10~(-11)@1s和1.22×10~(-11)@1000s.     

Two-level injection in fiber-delay line based oscillator

Two-level injection-locked opto-electronic oscillator is proposed for low phase noise. Dielectric resonator oscillator (DRO) is used as the first injection source, injection locking a long-fiber loop based opto-electronic oscillator, then its output is injection locking another long-fiber opto-electronic oscillator for getting a lower-phase noise output carrier. After the first injection, the single side band (SSB) phase noise at 10 kHz offset frequency decreases from −123 dBc/Hz to −135 dBc/Hz, then through the second injection the SSB phase noise drops down to −146 dBc/Hz.     

Frequency and phase synchronization in stochastic systems

The phenomenon of frequency and phase synchronization in stochastic systems requires a revision of concepts originally phrased in the context of purely deterministic systems. Various definitions of an instantaneous phase are presented and compared with each other with special attention paid to their robustness with respect to noise. We review the results of an analytic approach describing noise-induced phase synchronization in a thermal two-state system. In this context exact expressions for the mean frequency and the phase diffusivity are obtained that together determine the average length of locking episodes. A recently proposed method to quantify frequency synchronization in noisy potential systems is presented and exemplified by applying it to the periodically driven noisy harmonic oscillator. Since this method is based on a threshold crossing rate pioneered by Rice the related phase velocity is termed the Rice frequency. Finally, we discuss the relation between the phenomenon of stochastic resonance and noise-enhanced phase coherence by applying the developed concepts to the periodically driven bistable Kramers oscillator.     

Observations of Phase Locking in a Single-Cavity Gyrotron Oscillator

Observations of phase locking in a single-cavity gyrotron oscillator operating at 35 GHz are reported. Injection of the locking power was made via a circulator into the gyrotron output guide. Locking was observed with input power levels as low as 35 dB below the gyrotron power. For low input powers, good agreement is found with theory based on lumped-element circuit modeling and a new distributed oscillator model.     

一个不连续映象中的混沌稳定或混沌抑制

借助于一个张弛振子模型和与之相应的不连续映象说明了在这类系统中瞬态集的映蔽效应会产生三种区域：1）稳定混沌区，在此区域中不存在周期窗口，混沌轨道是结构稳定的；2）完全锁相区，在此区域中混沌被抑制，只存在周期运动；3）准周期区域，在此区域中混沌被抑制，只存在准周期或临界稳定的周期运动．这种思想被用来解释在一个实际张弛振子电路中观察到的稳定混沌区和完全锁相区 关键词：     

Optical frequency measurement across a 104-THz gap with a femtosecond laser frequency comb

The frequency-domain mode comb of a Ti:sapphire femtosecond laser centered at 350 THz is broadened to 150 THz (full width at -30 dBc) by self-phase modulation in a single-mode optical fiber. By phase locking continuous-wave lasers to elements of the comb near 1064 and 778 nm, we measure the 104-THz frequency gap between these two lasers with a relative uncertainty of 2.7 x 10(-11) in 1 s.     

Characterization and suppression of self-phase modulation in a commercial modelocked and Q-switched Nd:YLF oscillator

Spectral broadening up to 20 GHz has been measured in the pulsed output of a commercial actively-modelocked and Q-switched Nd:YLF oscillator operating at a modelocked pulse duration of 150 ps. The source of the broadening is self-phase modulation occurring in the acousto-optic modulators, as confirmed by modeling which has reproduced the observed spectra. With the CW lamp-pumped oscillator redesigned for a large mode volume in the modulators, the self-phase modulation is suppressed and near-transform-limited bandwidths at pulse durations of 85 ps are measured.     

Frequency locking by external force from a dynamical system with strange nonchaotic attractor

Usually, phase synchronization is studied in chaotic systems driven by either periodic force or chaotic force. In the present work, we consider frequency locking in chaotic Rössler oscillator by a special driving force from a dynamical system with a strange nonchaotic attractor. In this case, a transition from generalized marginal synchronization to frequency locking is observed. We investigate the bifurcation of the dynamical system and explain why generalized marginal synchronization can occur in this model.     

飞秒钛宝石放大激光脉冲的载波包络相位测量与控制

通过对重复频率为1 kHz的放大飞秒激光脉冲的光谱干涉实验,结合傅里叶变换进行了载波包络相位漂移的实验研究.在此基础上利用锁相环反馈控制技术实现了对载波包络相位的精密锁定,锁定后的激光脉冲稳态相位均方根误差小于80mrad,锁定时间超过3h.同时在理论上分析了光谱干涉测量放大激光脉冲载波包络相位的原理,给出了光谱干涉信号与载波包络相位的关系. 关键词： 飞秒钛宝石放大器 载波包络相位 光谱干涉 超连续