A bistable liquid crystal electro-optic modulator

A new liquid crystal hybrid bistable optical device is described. Optical bistability has been observed and the use of this device for optical logic elements and ultralinear modulation applications demonstrated. The transient response of the device for optical logic elements and ultralinear modulation applications demonstrated. The transient response of the device has also been studied and a “critical slowing down” phenomenon observed.     

Plasmonic all-optical bistable device based on nematic liquid crystal

Low-power all-optical bistable liquid crystal (LC) devices are reported in which surface plasmons propagate along a metallic grating. The threshold switching illumination was 1.4 mW/mm² in the device with the twisted-nematic LC cell. This is a lower value than for all-optical bistable devices reported previously. This low-power bistability device can be used in two-dimensional optical memories or spatial light modulators.     

光学双稳态和混沌运动中的临界现象

本文以具有反馈时间延迟的非线性系统弛豫方程为出发点,讨论了双稳态临界点的临界现象。发现双稳区边沿的临界慢化与混沌运动中切分叉点附近阵发混沌时间间隔发散具有一致性,临界指数为1/2。在双稳区(尖顶突变模型)的尖顶处,与双稳区边沿临界点不同,它与混沌运动中倍周期分叉点及劈分叉点的临界慢化具有一致性,临界指数为1。上述结果具有普适性。以液晶混合光学双稳系统为例,进行了计算机实验,其结果与分析相一致。 关键词：     

双稳液晶电光调制器

本文介绍了一种新的液晶混合双稳光学装置(LCBOD),观察到了液晶BOD两种运用方式的光学双稳态,描述了液晶BOD在光学逻辑元件和超线性调制上的应用,还研究了液晶BOD的瞬态响应,观察到了“临界延迟”现象,测量了开关时间,实验结果与Garmire的理论相符。 关键词：     

ZnSe－CdZnSe多量子阱F－P腔光双稳器件的室温皮秒反射式激子光双稳

近年来,半导体超晶格的光双稳器件由于功耗低、体积小、易于集成优点,引起国内外人们的广泛重视,特别是经优化的F-P腔光双稳器件,其反射式光双稳比透射式光双稳有很多的优点.     

Optical bistability effects in a Tm,Ho:YLF laser at room temperature

We demonstrate strong optical bistability in a 2 microm continuous-wave Tm,Ho:YLF laser pumped by a 792 nm laser diode near room temperature. The bistable region is as much as 100 mW wide at 283 K and can be controlled by the temperature of the laser crystal. The influence of crystal temperature on the characteristics of optical bistability is obtained. The influence of the pump-to-mode ratio on the bistable characteristics of the laser is also discussed. To our knowledge this is the first report of optical bistability effects in Tm,Ho:YLF lasers.     

室温CdxZn1—xTe／ZnTe多量子阱光学双稳态的研究

研制了室温ＣｄｘＺｎ１－ｘＴｅ／ＺＮＴｅ多量子阱法布里－珀罗腔光双稳器件，并在该器件上观察到皮秒一级的室温激子光双稳。研究结果表明，ＣｄＺｎ１－ｘＴｅ／ＺｎＴｅ多量子阱光双稳器件的光双稳值和对比度分别为３６３ｋＷ／ｃｍ＾２和４：１。根据ＣｆｘＺｎ１－ｘＴｅ／ＺｎＴｅ多量子阱的吸收谱和激子非线性理论，归结了ＣｄｘＺｎ１－ｘＴｅ／ＺｎＴｅ多量子阱光双稳的主要非线性机理为激子的饱和和吸收。     

Orientational transitions in ferromagnetic liquid crystals with bistable coupling between colloidal particles and the matrix

We study the orientational response of a ferromagnetic liquid crystal that is induced by magnetic and electric fields. A modified form of the energy of the orientational interaction between magnetic impurity particles and the liquid crystal matrix that leads to bistable coupling is considered. It is shown that apart from magnetic impurity segregation, first-order orientational transitions can be due to the bistability of the potential of the orientational coupling between the director and the magnetization. The ranges of material parameters that lead to optical bistability are determined. The possibility of first-order orientational transitions is analyzed for the optical phase difference between the ordinary and extraordinary light rays transmitted through a ferronematic cell. It is shown that an electric field applied in the given geometry considerably enhances the magneto-orientational response of the ferronematic.     

Logical and relational operations of optical bistable devices operating without external bias

We report successful optical realization of both logical and relational functionality using a multiple quantum well optical bistable device operating without external bias and a simple experimental setup. For the nonbiased optical bistability, we employed extremely shallow quantum wells and asymmetric Fabry-Perot cavity structure in self electro-optic effect device. The change between logical and relational mode was simply realized by controlling the intensity of the optical bias beam into devices following the basic operation principle of the optical bistability.     

Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.     

非线性一维光子晶体波导光双稳

利用非线性折射率系数较大且非线性时间响应较快的CdS_xSe_1-x玻璃为材料,设计并制备了非线性一维光子晶体波导光双稳器件,该器件的折射率空间分布呈正弦形式。实验测得双稳开关的阈值功率密度为1.60×10⁵W/cm²,开关时间为63ps。采用时域有限差分方法讨论了光子晶体带隙随入射光强变化而移动的情况,随着入射光功率密度的增加,光子晶体的带隙中心向短波方向移动。同时计算了该器件的双稳特性,理论计算得到双稳开关的阈值功率密度为1.40×10⁵W/cm²,开关时间约为50ps。获得了理论与实验基本一致的结果。     

Dispositif bistable à laser He-Ne à cristal liquide dans la cavité couplée

A hybrid bistable optical device is realised by using a liquid crystal light modulator (based on dynamic scattering), placed in a passive cavity which is coupled to a He-Ne laser cavity. The liquid crystal transmission is driven electronically by means of a feedback loop in the device.     

Optical bistability in fiber ring resonator containing an EDFA

In this paper, we study on optical bistability behaviors in a double-coupler ring resonator, in which an erbium-doped fiber amplifier (EDFA) is inserted into the ring for counteracting the loss by the gain of EDFA. The two groups of transmitted and reflected optical bistability loops under different parameters are investigated symmetrically. According to our optimum design of this new optical bistable device, the switching power can be less than 60 mW.     

End-pumped optical bistability Tm,Ho:YLF laser

We experimentally demonstrate strong optical bistability in a 2 μm continuous wave Tm,Ho:YLF laser with a bulk crystal. The laser is end-pumped by a 792 nm fiber-coupled laser diode. The bistable region is as wide as 1.6 W and the jump power at the turning point is as high as 82.5 mW when the temperature of the laser crystal is kept at 253 K. The influences of the cavity length and the transmission of the output coupler on the characteristics of optical bistability are obtained. The theoretical analysis shows that the bistable output in the Tm,Ho:YLF lasers comes from the combined effects of the nonlinear saturation of ground state reabsorption, the energy transfer upconversion, and the excited state absorption.     

掺CdS_xSe_（1－x）玻璃波导分布反馈光学双稳器件

本文给出了掺ＣｄＳ_ｘＳｅ_(１－ｘ)玻璃平面波导分布反馈（ＤＦＢ）光学双稳器件的设计和制备方法，实现了低功耗、快速的本征光学双稳。     

Vertical and direct integration of heterojunction phototransistors and laser diodes

An optoelectronic integrated device based on the concept of vertical and direct integration is described. Four types of integrated devices composed of multiple heterojunction phototransistors and laser diodes are developed and the devices successfully achieve thirteen functions: optical switching, amplification, thresholding, bistability, light-controlled optical bistability, light-controlled optical thresholding, tristability, set and reset functions in tristable states, set and reset functions in tetrastable states, and bistable and tristable flip-flop functions.     

液晶光学双稳态中离子电荷飘移引起的自脉冲振荡

在液晶混合光学双稳装置中,实验上观察到了由于直流电场引起的液晶中离子电荷飘移与液晶分子再取向之间竞争相互作用导致的自脉冲振荡现象。给出了该系统的弛豫方程。通过数值分析,得到了与实验定性一致的结果。 关键词：     

Control and managing of localized states in two-dimensional systems with periodic forcing

We study the formation of localized structures in two-dimensional systems with periodic forcing, showing that these types of systems provide an adequate framework for the study and control of localized structures. Theoretically, we introduce a dissipative ϕ ⁴ model as a prototype for a bistable spatially forced system, and we show that with different spatial forcings of small amplitudes, such as square or hexagonal grids, this model exhibits a family of localized structures. By changing the forcing parameters, we control the bistability between the various induced patterns. Experimentally, based on an optical feedback with spatially amplitude-modulated beam, we set-up a two-dimensional forced experiment in a nematic liquid crystal cell. By changing the forcing parameters, the system exhibits a family of localized structures that are confirmed by numerical simulations for the average liquid crystal tilt angle.     

Bistable properties of spatial light modulator with internal feedback

A bistable spatial optical device has been developed on the basis of a spatial light modulator which contains photosensitive and electrooptical liquid crystal layers, where an internal feedback loop is established.     

Optical bistability in plasmonic nanoparticles: Effect of size,shape and embedding medium

We theoretically investigate the optical bistability, which one input signal allows two possible outputs, from single spherical/cylindrical nanoparticles and also nanoshells in the frame work of quasi-static formalism. It is shown that the bistability behavior greatly depends on several parameters such as the nanoparticle size, material and the surrounding dielectric environment. We demonstrated the width of the bistability region and also the bistable threshold depends on the geometrical parameters, and can be tuned by adjusting the size of nanoparticle, the shell thickness and the dielectric constant of the embedding medium. It is also shown that the optical bistable behavior depends strongly on the shape of plasmonic nanoparticles and nanoshells. However, these dependences of optical bistability of spherical/cylindrical nanoparticles and nanoshells on changing of their geometrical parameters can be used for realize optical switching and sensing purposes.