Optical bistability in BaTiO3

In this paper experimental results concerning the optical bistability of a ferroelectric monocrystal of BaTiO₃ are presented. Two laser beams were used to interact with the monocrystal which resulted in the bistability of the intensity of the transmitted wave. This was achieved without the application of any optical resonator. The feedback was provided by the electronic system through a mechanism typical to all photorefractive materials.     

Optical bistability and multistability in an open ladder-type atomic system

A novel scheme is proposed for controlling the optical bistability and multistability in an atomic system. In an open ladder-type three-level atomic system, it is shown that, by adjusting the ratio between atomic injections and exit rates from the cavity, the intensity threshold of optical bistability can be controlled. The effect of incoherent pumping field and spontaneously generated coherence (SGC) on optical bistability for different values of exit rates is also discussed. It is found that SGC makes the medium phase dependent, so the optical bistability and multistability threshold can be controlled via relative phase between applied fields. Moreover, it is shown that the optical bistability can be switched to optical multistability, which is favorable for the next generation of all-optical systems and quantum networks.     

Intrinsic optical bistability in doped polymer

One of the most interesting and applicable effects of nonlinear optics is optical bistability. This phenomenon is exhibited by certain resonant optical structures where it is possible to have two stable steady transmission states for the device, depending on the history of the input. Such a bistable device may be useful for optical computing elements as a result of its memory characteristics. Optical bistability behaviour is usually observed by inserting a nonlinear matter inside a Fabry–Perot interferometer. But in this study, it was shown that this can be achieved without the application of any optical resonator. Two laser beams were used to interact with the photorefractive media (doped PMMA polymer) which resulted in the bistability of the intensity of transmitted wave. Feedback was provided by a periodic grating created in the photorefractive polymer PMMA.     

Optical bistability of surface plasmon polaritons in nonlinear Kretschmann configuration

Optical bistability based on surface plasmon polaritons in the Kretschmann configuration involving a Kerr nonlinear medium is described by analytical solutions. The conditions of forming the optical bistability with different parameters are explored. The resonant angle of surface plasmon polaritons varying with the incident light intensity also generates the phenomenon of bistability. The system could form optical bistability with the special thickness of the metal film and incident angle. This kind of system has potential application in all-optical networks.     

环形腔中非线性周期结构介质的双稳态和光限

研究了环腔中的非线性周期结构介质的光学双稳态和光限现象，建立了输入光强与输出光强关系的表达式。理论上给出了临界入射光强低达１０＾７Ｗ／ｃｍ＾２的光学双的条件和非常有效的限光作用的条件。     

Kerr nonlinearity and optical multi-stability in a four-level Y-type atomic system

The nonlinear response to applied fields of a four-level Y-type atomic system is investigated. The effect of laser intensity and quantum interference induced by spontaneous emission on optical bistability, optical multi-stability and Kerr nonlinearity is then discussed. It is found that the threshold of the optical bistability can substantially be reduced by the quantum interference. So, an enhanced Kerr nonlinearity with reduced absorption can be achieved.     

Intracavity Optical Bistability Driven by Squeezed Light from a Parametric Amplifier

Abstract

We describe the theory of optical bistability when atoms are collectively excited within the cavity of a parametric oscillator. Both optical bistability and parametric amplification can squeeze significantly the cavity-field quantum noise. When they are coupled together we find significant changes both on the mean value bistability and on the spectrum of squeezing as the parametric coupling increases. These are calculated directly from the appropriate master equation for the density matrix using a quantum distribution function (positive P) to develop Fokker—Planck and Ito equations.     

Low-power optical switching with Kerr nonlinear material in two-dimensional photonic crystal nanocavity

We investigate numerically optical bistability in direct-coupled cavity–waveguide photonic crystal system using the finite-difference time-domain method. The quality factor of the cavity is optimized by engineering the geometrical parameters. Numerical results indicate that the threshold power of optical bistability can be reduced greatly due to the increased quality factor.     

Kerr bistability in an optical fiber ring resonator with a 3 × 3 planar fiber coupler

A theoretical study of bistability caused by the optical Kerr effect in a type 1 optical fiber ring resonator connected to a 3 × 3 planar coupler is presented. The dependence of the bistability on various parameters of the fiber and the coupler is investigated. A comparison between the bistable characteristics of this ring resonator and those of a fiber ring resonator with a 3 × 3 equilateral triangular (nonplanar) fiber coupler is made.     

Optical realization of bioinspired spiking neurons in the electron trapping material thin film

A thin film of electron-trapping material (ETM), when combined with suitable optical bistability, is considered as a medium for optical implementation of bioinspired neural nets. The optical mechanism of ETM under blue light and near-infrared exposure has the inherent ability at the material level to mimic the crucial components of the stylized Hodgkin-Huxley model of biological neurons. Combining this unique property with the high-resolution capability of ETM, a dense network of bioinspired neurons can be realized in a thin film of this infrared stimulable storage phosphor. When combined with suitable optical bistability and optical interconnectivity, it has the potential of producing an artificial nonlinear excitable medium analog to cortical tissue.     

Tunable beam focusing based on optical bistability with a composite Kretschmann configuration involving a Kerr medium

A beam focuser with a composite Kretschmann configuration involving a Kerr medium is investigated theoretically. The structure employs a silver film with four slits filled with the Kerr medium. Optical bistability and beam focusing are demonstrated, and changes to the incident intensity result in optical bistability characteristics in the reflection, focused intensity, spot size, and depth of focus. The proposed structure has the potential to be applied for optical switching and nano-illumination.     

Mirrorless optical bistability in a semiconductor-doped-glass plate as a result of oblique incidence

A procedure to obtain optical bistability in a third-order nonlinear film (or parallel plate) of low refractive index without any external mirrors is investigated both theoretically and experimentally. If an s-polarized light is incident obliquely at a large angle of incidence on the film, the generation of optical bistability can be expected because of the resulting increase in the reflectivity at the surfaces. Arigorous analysis of the stationary transmission characteristics of the nonlinear film is done for both positive and negative nonlinear coefficients with a plane-wave model. In the experimental demonstration, a CdS(x)Se(1-x)doped glass (Hoya Y-52) plate and a cw Ar(+) laser are used as the nonlinear material and the light source, respectively. It is shown that three operations of optical bistability, optical limiting, and differential gain can be easily obtained through adjustment of the angle of incidence as an initial detuning. The measured nonlinearity is thermal, and the magnitude and sign of the nonlinear refractive index are determined.     

Optical Bistability and Reversed Switching Effect in a Three-photon Resonant Medium

We have developed, ab initio, a theory for the interaction of coherent laser light in three-photon resonance with two effective levels of a multilevel atom. The theory is developed to consider the optical bistability of homogeneously broadened, three-photon, resonant multilevel atoms inside a ring cavity. It is shown that optical bistable behaviour in the fundamental and the generated third harmonic can be obtained using, for example, Na atoms. The device may be useful in constructing two-channel, optical bistable switches. In certain nonlinear regimes it may be possible to obtain reversed switching between the fundamental and the third harmonic bistability.     

Optical bistability in metal-insulator-metal plasmonic Bragg waveguides with Kerr nonlinear defects

We numerically investigate the characteristics of the defect mode and the nonlinear effect of optical bistability in metal-insulator-metal (MIM) plasmonic Bragg grating waveguides with Kerr nonlinear defects. By means of finite-difference time-domain simulations, we find that the defect mode peak exhibits a blueshift and height-rise by enlarging the width of the defect layer, and it has a redshift and height-fall with the increase of the dielectric constant of defect layer. Obvious optical bistability is obtained in our waveguides with a length of less than 2 μm. The results show that our structure could be applied to the design of all-optical switching in highly integrated optical circuits.     

Phase optical bistability in structures with surface plasmons

A theoretical analysis is made of the phenomenon of phase optical bistability in structures with surface plasmons. It is shown that in an optical waveguide with a nonlinear layer, not only amplitude but also phase bistability may occur when p-polarized radiation is reflected from the nonlinear waveguide. Pis’ma Zh. Tekh. Fiz. 24, 60–65 (August 26, 1998)     

Optical bistability in metal-insulator-metal plasmonic waveguide with nanodisk resonator containing Kerr nonlinear medium

We numerically investigate the optical bistability effect in the metal-insulator-metal waveguide with a nanodisk resonator containing a Kerr nonlinear medium. It is found that the increase of the refractive index, which is induced by enhancing the incident intensity, can cause a redshift for the resonance wavelength. The local resonant field excited in the nanodisk cavity can significantly increase the Kerr nonlinear effect. In addition, an obvious bistability loop is observed in the proposed structure. This nonlinear structure can find important applications for all-optical switching in highly integrated optical circuits.     

Comparison of optical properties between ladder and lambda-type EIT medium with Er3+ ion concentration in Er3+:YAG crystal

The effect of Er³⁺ doped ion concentration on optical properties of two type three-level schemes in 35 nm Er³⁺:YAG (yttrium aluminum garnet) crystal is studied. It is found that intensity threshold of optical bistability and multistability can be changed by Er³⁺ doped ion concentration. Moreover, switching from optical multistability to optical bistability can be done differently by Er³⁺ concentration in two types of three-level schemes. The steady-state and transient behaviors of absorption, dispersion and group index of weak probe field in two schemes are also discussed. In this study, we will report an initial study on optical properties in Er³⁺:YAG crystal and propose a basis for selecting the suitable concentration to carry out experimental investigations in the future.     

Elimination of Kerr bistability in an optical fiber ring resonator with a 3 × 3 planar fiber coupler

A special property of a type 3 optical fiber ring resonator with a 3 × 3 planar coupler in which the circulating intensity is independent of the phase change of the ring resonator can be used to eliminate unwanted Kerr bistability. At the same time the device can be used as a two-channel frequency division multiplexer or demultiplexer or a switch. Another method for the elimination of Kerr bistability is the use of two fibers whose nonlinear refractive-index coefficients have opposite signs to build the ring resonator.     

Intrinsic optical bistability in layered crystals

The parametric excitation of the low-frequency overtone in GaSe crystal by a biharmonic optical field is shown to lead to bistability of both the crystal refractive index and the optical field generated in the four-wave-mixing process. The effect appears to be much stronger in layered crystals than in crystals of higher symmetry.