Dynamics of electrooptic bistable devices with delayed feedback

The dynamic behavior of electrooptic bistable devices with delayed feedback is investigated theoretically and experimentally. The operation principle of the system is analyzed by the method of iterated maps. Stable, bistable, periodic, higher periodic, and chaotic solutions are discussed and realized experimentally by using an integrated Mach-Zehnder interferometer on LiNbO3as a basic nonlinear element. Taking into account the periodic modulator characteristic, the application of this device as a simple and fast bistable and monostable multivibrator is demonstrated. In addition, the synchronization properties of the astable multivibrator are investigated.     

Optical regenerative oscillation and monostable pulse generation in electrooptic bistable devices

Optical regenerative oscillation is discussed theoretically and experimentally in three types of mirrorless bistable optical devices based on the electrooptic light modulator. The devices have two feedback signals proportional to the optical output power, and the oscillation condition and oscillation frequency depend on the time constants and conversion factors for two feedback voltages and biasing phase retardation in the light modulator. Analysis is done by treating the coupled differential equations for the time dependent feedback signals. The experimental results agree with the theoretical prediction. We show also that optical monostable pulses can be generated in the three types of bistable optical devices.     

Ion-implanted ESFI MOS devices with short switching times

Switching times of complementary MOS devices realized with epitaxial silicon films on insulators (ESFI) are reduced by using a self-aligning technique with ion implantation, since the gate overlapping capacitances and therefore the so-called Miller capacitances, are reduced thereby. Switching times and power dissipation have been measured using multistage ring oscillators. Stage-delay times of 500 ps at a supply voltage of 10 V (800 ps at 5 V), and power-delay products of 0.5 pJ at 5 V, have been obtained at five-stage ring oscillators with a channel length of about 3 /spl mu/m. Calculated and measured results are compared, and a simple formula for calculating the influence of the Miller capacitance on the switching times is indicated.     

An electrooptic and optoelectric bistable interconnect at 514 nm:the photothermal CdS self-electrooptic effect devices

Illumination of CdS at room temperature with the green (514 nm) line of an Ar⁺ laser may lead to intrinsic photothermal-induced absorption optical bistability. If the samples are covered with two metal contacts resulting in a small slit, the additional feedback introduced through the photocurrent by Joule's heat may lead to a reduction of the necessary optical input power. In particular, CdS single-crystal platelets, CdS epitaxial layers, or CdS evaporated layers contacted with either Au or In are used. The experimental characteristics are compared with detailed model calculations, which explain deviations from ideal behavior. Special emphasis is laid upon the modulator characteristics (i.e. controlling photonics by electronics) and the possibility of controlling electronics by photonics     

Optical multistability in the mirrorless electrooptic device with feedback

Optical multistable operations are controllably accomplished in the mirrorless electrooptic device with feedback by arranging the polarizer and/or analyzer at appropriate angles with respect to the crystallographic axes of an electrooptic crystal. Moreover, different operating characteristics in two optical output powers with orthogonal polarizations separated from each other by an analyzer are examined theoretically and experimentally.     

热-光双稳态器件中的温度梯度

本文从热传导理论出发,讨论了产生热-光双稳态的F-P腔内的纵向温度分布及其对临界温升的影响。提出并讨论了减少或消除纵向温度梯度的腔内夹层介质的吸收和后反射镜的吸收匹配条件。     

High-speed electrooptic modulation in GaAs/GaAlAs waveguide devices

A figure of merit is constructed for broad-band electrooptic modulators which compares bandwidth with launched generator voltage standardized to a common wavelength. Comparison of various published results in terms of this figure shows that a lumped-element III-V semiconductor device performance may be no more than a factor of two below that of typical (i.e., LiNbO3) traveling wave devices and are probably easier to implement-especially in an integrated format. Accurate modeling, which incorporates all transit time and velocity match effects, is described and found to agree well with experimental results. Experimental GaAs/GaAlAs modulators have been made, using a Mach-Zehnder interferometer configuration. At a wavelength of 1.15 μm and with unterminated drive a bandwidth of 6.5 GHz was obtained with Vpiof 17.3 V. A shorter (34.6-v) device was ∼ 1.25-dB down at 8.4 GHz. The corresponding figures of merit are close to the maximum expected for the configurations used.     

Fast bistable wavelength switching characteristics in two-electrodedistributed feedback laser

Fast bistable wavelength switching between two longitudinal modes separated by 1.7 nm was achieved in a two-electrode distributed feedback laser with inhomogeneous excitation. As a result, a fast wavelength switching time less than 200 ps was observed in this device. In addition, high-speed repetitive wavelength switching operation up to 1 GHz was achieved. This indicates that the device is capable of repetitive wavelength switching within 1 ns, including delay time and rise time     

Charge trapping models of resistance switching in organic bistable devices with embedded nanoparticles

We discuss three different models of switching between the high conductivity and low conductivity state in organic bistable devices (OBD) with embedded nanoparticles. All models assume the same basic mechanism: charge trapping and de-trapping in metal nanoparticles. We show trapped charges can both induce an increase or a reduction of the total current depending on device configurations. The influence of energy disorder is investigated.     

外部微扰反馈对Bragg声光双稳系统混沌的控制

针对Bragg路声光双稳系统的混沌态,提出了利用外部微扰反馈的方法对其进行控制。数值分析表明,适当选择反馈强度可将原本混沌的系统控制到各种不同的周期轨道上,同时计算了噪声对系统状态演化的影响。结果表明,系统对小幅度噪声具有一定抗干扰能力。     

延迟反馈法对Bragg声光双稳系统混沌的控制

针对Bragg声光双稳系统的混沌态,提出了利用延迟反馈的方法对系统参量进行控制的方法,并讨论了连续、间隙两种控制方法下系统的状态演化。数值分析表明,适当选择反馈强度可将系统的混沌态稳定到各种不同的周期轨道上。间隙反馈控制不仅具有可控范围大、控制代价小的优势,还能将系统的稳态周期数控制为间隙反馈周期的整数倍。     

Accurate time-domain analysis of microwave and optical signal interaction in electrooptic devices

This paper presents a novel formalism based on the application of the generalized telegrapher's equations to the modeling and designing of integrated electrooptical devices. In this approach, we eliminate the restrictions commonly introduced in the past, such as a weakly guiding condition and isotropic unperturbed medium, while evaluating the modulator time response to an arbitrary modulating signal. Small dielectric perturbations and a large difference between the optical and modulating signal frequencies are the only hypotheses used in deriving the linear model. By applying a multiple-scale perturbation method, we reach an analytical solution to the problem of multipolarization interaction. Some applications are discussed.     

Thermal feedback in power semiconductor devices

Thermal feedback (TF) is an important aspect for the thermal management of semiconductor devices and high-power density integrated circuits. Different features of positive and negative TF in transistors are reviewed and summarized for the macroscopic domain. The thermal feedback mechanism is applied to the microscopic domain of noise fluctuations in semiconductor devices. It is argued that TF may be responsible for a major part of 1/fflicker or excess noise. Some experimental evidence is presented which supports this thermal feedback 1/f-noise theory for bipolar and MOS field effect transistors. Device and circuit design rules for the minimization of transmitter noise are given.     

Linewidth determination from self-heterodyne measurements with subcoherence delay times

The behavior of the power spectrum of an external cavity semiconductor laser has been studied using a delayed self-heterodyne interferometric technique that uses delay times less than the laser's coherence time. Experimental results show that the resulting power spectrum is consistent with the theoretical model. However, there is evidence that additional frequency fluctuations are present that cause the delta function portion of the power spectrum to have a finite width.     

一种连续状态反馈方法控制混合光学双稳系统混沌

本文设计了一种连续状态反馈(CSF)方法控制非线性混沌系统,并将此方法应用到混合光学双稳(MOB)系统混沌的控制上,验证其有效性。文中给出了CSF控制方法的构建依据、控制原理以及控制参数的选择技巧并使用计算机数值模拟了MOB系统混沌被控制后的动力学行为。数值分析结果表明,适当地调整控制参数不仅可以实现原混沌系统内部的非稳定周期轨道稳定化,还可以将原混沌系统控制到其它的目标周期轨道上去。此种控制方法稳定性好,控制速度快,且可以方便灵活地获得1p、2p、3p…2mp×3np(m,n为整数)等多种稳定的周期轨道。同时,CSF方法对低周期和高周期轨道的控制都很有效。     

Turn-on delay for Josephson logic devices with high damping

Josephson logic devices exhibit, before switching from superconducting to voltage state, a turn-on delay which depends on current overdrive and damping coefficient. A novel expression describing turn-on delay for heavily damped circuits is proposed. A comparison with numerical calculation is made. As an example of application for this expression, the turn-on delay appearing in the simulation of a damped logic gate switching is discussed.     

单环掺铒光纤激光器光延迟反馈的混沌控制

为了找到更加简单稳定激光系统的混沌化方法,采用光延迟反馈方法对单环掺铒光纤激光器特性进行了数值仿真,得到了各种周期现象而且产生了混沌现象。结果表明,利用单模单环掺铒光纤激光器,在附加光延迟反馈环路的方法下可以实现混沌控制。这一结果对应用于保密通信的混沌化简化具有重要意义。     

反馈延迟对光纤陀螺振动误差特性的影响

振动环境导致光纤陀螺引入较大的扰动。由于非线性因素,陀螺跟踪扰动的能力严重影响着其误差特性,而反馈延迟的存在使得跟踪性能变得更加复杂。因此,分析反馈延迟对于解决陀螺振动问题极其重要。首先,分析了非线性因素作用时不同反馈延迟对陀螺闭环跟踪能力和扰动稳定性的影响;然后在线性控制模型的基础上加入陀螺非线性环节,保证稳定裕度不变,仿真分析了不同反馈延迟下陀螺的跟踪性能以及输出。仿真及实验结果表明,减小反馈延迟,提高系统的跟踪扰动能力,可以减小非线性误差,改善振动环境下陀螺的输出性能。     

Hot carriers' effects in short channel devices

Experimental evidence for the impact of hot holes injection under pulsed voltage stress on the device degradation are presented. The transconductance lowering was supposed to be caused by an increase of the interface states density near the drain region. A field effect mobility decrease and an increase of the surface scattering factor by an amount larger for the shorter channel lengths were observed.     

Negative group delay times in frustrated Gires-Tournois andFabry-Perot interferometers

It is demonstrated in this paper that a Gires-Tournois interferometer illuminated with an angle of incidence greater than the critical angle for total internal reflection introduces a negative group delay time, whatever the orientation of the electric field vector of the wave with respect to the plane of incidence, when the evanescent wave in the dielectric layer is reflected by a dielectric substrate whose refractive index is between those of the incident medium and of the dielectric layer. When the evanescent wave in the dielectric layer is reflected by a nonabsorbing metal, the group delay time is negative when the electric field vector is in the plane of incidence and positive when the electric field vector is perpendicular to the plane of incidence. Similarly, a frustrated Fabry-Perot interferometer shows negative group delay times for angles of incidence greater than specific p-wave and s-wave critical angles