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1.
两表面镀有高反射膜,自身形成F-P腔的CdSSe玻璃薄片置于环形腔中.在一定的输入光强参数下,反射光信号出现其有某种规律性的振荡.实验观测了作为输入光强函数的不同振荡模式.由于所用样品的光双稳回线宽阔,上下两支有较大的倾斜度,我们观察到较大数目的输出强度上升与下降台阶.简单的绝热模拟表明,自振荡的模式遵从Farey-tree结构. 相似文献
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By using polarization-rotated optical feedback from the transverse-electric (TE) mode to the transverse-magnetic (TM) mode,
chaotic oscillations for both polarization modes are excited in a semiconductor laser. We find different correlations between
these chaotic oscillations than those found in previous studies. In this study, the dynamics are strongly dependent on their
radio-frequency (RF) components and they are divided into three RF regions. For low-pass filtered signals lower than the laser
relaxation oscillation, there is an antiphase correlation between the two polarization modes. On the other hand, the two polarization
modes have an in-phase correlation for the RF components of the high-pass filtered signals, which are higher than the relaxation
oscillation. However, no correlations were observed between the two modes for the intermediate RF components that include
the relaxation oscillation frequency. We also perform numerical calculations for the model and obtain good agreement between
the theoretical and experimental results. 相似文献
4.
The influence of the relaxation time of a saturable absorber on the dynamics of a quasi-continuous ring laser is investigated. It is shown that in a dye laser with a fast absorber, bistability arises; thus two multimode regimes coexist. The regime of shallow stochastic modulation is established spontaneously. Transition to the mode-locking regime accompanied by a sharp increase in the number of generated modes is feasible only under the action of an initiating pulse (hard mode locking). The analytical criterion for hard locking has been obtained. If the criterion is not satisfied, the only stable regime of a laser is mode locking. In this case the transient process is the longer the smaller the relaxation time of a saturable absorber. 相似文献
5.
Optical bistability is realized in GaInAsP/InP coupled-circular resonator microlasers, which are fabricated by planar technology. For a coupled-circular resonator microlaser with the radius of 20?μm and a 2?μm-wide bus waveguide, hysteresis loops are observed for the output power coupling into an optical fiber versus the cw injection current at room temperature. The laser output spectra of the upper and lower states of the hysteresis loop indicate that the bistability is related to mode competitions. The optical bistability can be explained as the mode competition between the symmetry and antisymmetry coupled modes relative to the bus waveguide. 相似文献
6.
M. Wegener C. Klingshirn G. Müller-Vogt 《Zeitschrift für Physik B Condensed Matter》1987,68(4):519-525
In contrast to a dispersive nonlinearity, induced absorption may without a cavity lead to intrinsic optical bistability. If however such an absorber is placed in a ring-cavity with a round trip time larger than the relaxation time constant of the medium, oscillatory instabilities have been (theoretically) predicted. We investigate CdS at room temperature (photo-thermal effects) in a hybrid ring-cavity. A Farey-tree structure of the oscillation period as a function of the incident intensity is observed. In the present paper we discuss the influence an external modulation of the incident intensity has on the oscillation modes both, experimentally and with simple model calculations. Again a Farey-tree structure of the average period of the oscillation modes in multiples of the modulation period is obtained both as a function of the modulation frequency and the modulation amplitude. 相似文献
7.
研究了三种掺Yb钒酸盐晶体Yb:LuVO4,Yb:YVO4和Yb:GdVO4的激光振荡中所呈现的光学双稳态效应.以晶体所吸收的抽运功率表征的双稳区宽度ΔPabs可超过1W,在双稳区高功率一侧的边界,即激光振荡的上阈值点,出现激光输出功率的不连续变化或跃变,同时发生亚毫秒时间尺度上的大幅度强度涨落.谐振腔的输出耦合透过率、晶体长度、晶体中的热效应等对双稳态效应均具有重要影响. 相似文献
8.
Transmission properties of one-dimensional photonic crystal with two nonlinear defects were investigated based on the nonlinear transfer matrix method. From the inspection of the optical bistabilities around different defect modes, it was found that the threshold of bistability for the bonding mode is always lower than that for the anti-bonding mode. When intensity of the incident wave increases bistability could happen at any wavelength larger than the resonance wavelength of the linear anti-bonding mode in the gap. The threshold of bistability increases initially with the wavelength, then decreases sharply in reaching the resonance wavelength of the linear bonding mode. The coupling behavior of the two defects was also discussed, and it was found that the threshold of bistability increases with the distance between the two defects. A flat spectrum similar to that formed in the photonic crystal molecules was obtained under certain incident intensity. 相似文献
9.
Relaxation cavityless optical bistability is studied when a semiconductor is exposed to light quanta with an energy exceeding
the transition energy and the free-electron relaxation time depends on temperature. The numerical analysis of dynamic equations
for temperature and free-electron density demonstrates that 11 regimes of light-semiconductor interaction are possible. The
regimes are classified in terms of the features of temperature-intensity characteristic curves, namely, by the number and
arrangement of instability and quasistability segments and by the presence or absence of bistability. It is found that both
the upper and the lower branch of a bistable characteristic curve may be unstable, which results in spontaneous switchings
between the respective states. Similarly, if the upper state is unstable and the lower state is stable, a small perturbation
of the parameters (free-electron temperature and density) near the former causes the transition to the oscillatory regime.
If the upper state is unstable and a small perturbation of the lower (stable) state excites a damped oscillation, spontaneous
switchings result if the fluctuating temperature exceeds some critical value for the lower state. 相似文献
10.
Shear waves with finite amplitude in a one-dimensional resonator in the form of a layer of a rubber-like medium with a rigid
plate of finite mass at the upper surface of the layer are investigated. The lower boundary of the layer oscillates according
to a harmonic law with a preset acceleration. The equation of motion for particles in a resonator is determined using a model
of a medium with a single relaxation time and cubical dependence of the shear modulus on deformation. The amplitude and form
of shear waves in a resonator are calculated numerically by the finite difference method at shifted grids. Resonance curves
are obtained at different acceleration amplitudes at the lower boundary of a layer. It is demonstrated that, as the oscillation
amplitude in the resonator grows, the value of the resonance frequency increases and the shape of the resonance curve becomes
asymmetrical. At sufficiently large amplitudes, a bistability region is observed. Measurements were conducted with a resonator,
where a layer with the thickness of 15 mm was manufactured of a rubber-like polymer called plastisol. The shear modulus of
the polymer at small deformations and the nonlinearity coefficient were determined according to the experimental dependence
of mechanical stress on shear deformation. Oscillation amplitudes in the resonator attained values when the maximum shear
deformations in the layer were 0.4–0.6, which provided an opportunity to observe nonlinear effects. Measured dependences of
the resonance frequency on the oscillation amplitude corresponded to the calculated ones that were obtained at a smaller value
of the nonlinear coefficient. 相似文献
11.
Jeong Eun Kim Matthias-Reńe Dachner Alexander Wilms Marten Richter Ermin Malic 《Photonics and Nanostructures》2011,9(4):337-344
We propose a theoretical model to investigate the switch-on dynamics of electrically pumped quantum dot vertical-cavity surface-emitting lasers. The model is based on the self-consistently combined quantum dot-wetting layer Maxwell–Bloch equations incorporating microscopically calculated Coulomb and phonon-assisted scattering processes between the quantum dot and the quantum dot-embedding wetting layer states. Our approach allows the calculation of the time delay before lasing as well as of the frequency and damping rate of the appearing relaxation oscillation. We study their dependence on the strength of the injection current density and on the number of QD-layers and DBR-layers by using the finite-difference time-domain method. The results show that switch-on delay time is in inversely proportion to the injection current density while the frequency and the damping rate of relaxation oscillation are proportional to the current density. If we increase the numbers of QD-layers and DBR-layers the delay time becomes shorter, and the frequency and the damping rate become larger. 相似文献
12.
The dynamic behaviors of nonlinear periodic waveguides with a finite material response time have been investigated by numerically solving both the coupled-mode equations and Debye relaxation equation. When the response time of the nonlinearity is more than the transit time through the grating, a modulational instability is sufficiently suppressed and one can obtain optical bistability. Unlike a nonlinear Fabry-Perot resonator or ring resonators, overshoot in the transmission never takes place in the case of zero detuning. However, a relaxation (or damped) oscillation always takes place in the presence of detuning. It is also found that the switch-on time depends on the material response time and the switch-off time is almost independent of it. 相似文献
13.
Superconducting quantum point contacts are known to possess two subgap states per propagating mode. In this note we compute
the low-temperature relaxation rate of the upper subgap state into the lower one with the emission of an acoustic phonon.
If the reflection at the contact is small, the relaxation time may become much longer than the characteristic lifetime of
a bulk quasiparticle.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 11, 847–851 (10 December 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
14.
We report on realization of an efficient triply resonant coupling between two long lived optical modes and a high frequency surface acoustic wave (SAW) mode of the same monolithic crystalline whispering gallery mode resonator. The coupling results in an opto-mechanical oscillation and generation of a monochromatic SAW. A strong nonlinear interaction of this mechanical mode with other equidistant SAW modes leads to mechanical hyperparametric oscillation and generation of a SAW pulse train and associated frequency comb in the resonator. We visualized the comb by observing the modulation of the light escaping the resonator. 相似文献
15.
The switching time of an optically switched laser diode between a locked mode and free oscillation mode is studied. By starting with linear stability analysis, analytical expressions are developed to predict the switching time. It is shown that the switching of optical output between the locked and unlocked modes is governed by two relaxation processes with different time constants, and the change in the first relaxation process, dependent on the carrier density in the initial state, gives a strong effect on the total switching time, in contrast to the dynamic behavior of the carrier density dominated by a single relaxation process. Our analytical results show that larger detuning and power of optical input are effective in shortening the switching time and are believed useful to estimate the switching time of an optically switched bistable laser diode. 相似文献
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van Dijk EM Hernando J García-López JJ Crego-Calama M Reinhoudt DN Kuipers L García-Parajó MF van Hulst NF 《Physical review letters》2005,94(7):078302
We report the first experimental study of individual molecules with femtosecond time resolution using a novel ultrafast single-molecule pump-probe method. A wide range of relaxation times from below 100 up to 400 fs is found, revealing energy redistribution over different vibrational modes and phonon coupling to the nanoenvironment. Addressing quantum-coupled molecules we find longer decay times, pointing towards inhibited intramolecular decay due to delocalized excitation. Interestingly, each individual system shows discrete jumps in femtosecond response, reflecting sudden breakup of the coupled superradiant state. 相似文献
18.
In this paper, we demonstrate the dynamic simulation of light traveling in a fiber ring resonator with a single coupler. Optical nonlinear phenomena including bistability, the Ikeda instability, bifurcation and chaos are studied. The Ikeda instability in ring resonator arises from the ring-cavity lifetime being much longer than the Kerr-effect response time of the fiber. The transmission curves of the bistability and the instability as function of the insertion losses (γ) and the coupling coefficients (κ) of the coupler are derived. 相似文献
19.
Xiaobin Yang Youhe Zhou Shandong Tu 《Physica C: Superconductivity and its Applications》2010,470(2):109-114
The influence of the magnetization and relaxation time on flux jumps in high temperature superconductors (HTSC) under varying magnetic field is studied using the fundamental electromagnetic field equations and the thermal diffusion equation; temperature variety corresponding to flux jump is also discussed. We find that for a low sweep rate of the applied magnetic field, the measurement and relaxation times can reduce flux jump and to constrain the number of flux jumps, even stabilizing the HTSC, since much heat produced by the motion of magnetic flux can transfer into coolant during the measurement and relaxation times. As high temperature superconductors are subjected to a high sweep rate or a strong pulsed magnetic field, magnetization undergoes from stability or oscillation to jump for different pause times. And the period of temperature oscillation is equal to the measurement and relaxation time. 相似文献
20.
Mechanisms behind the oscillations of a charged spheroidal drop deformed at the zero time and the sequence of oscillation
modes are investigated. It is shown that two modes adjacent to those governing the initial deformation are also excited on
either side due to interaction between the spheroidal deformation and oscillation modes. If the charge of the drop is so close
to a value critical for electrostatic instability that the finite-amplitude virtual initial deformation makes the fundamental
mode unstable, its amplitude, as well as the amplitude of the nearest neighbor coupled to the fundamental mode through deformation,
starts to exponentially grow with time. If the charge is equal to, or slightly exceeds the critical value, the amplitudes
of the fundamental mode and all modes deformation-coupled with it lose stability almost simultaneously. This qualitatively
changes the conditions under which the charged drop becomes unstable against the self-charge. The superposition of higher
oscillation modes at the vertices of the spheroidal drop generates dynamic (i.e., time-oscillating) hillocks emitting an excessive
charge. 相似文献