Controllable Optical Bistability in a Crystal of Molecular Magnets System

We investigate the formation of optical bistability (OB) in a crystal of molecular magnets contained in a unidirectional ring cavity. The crystal is subjected to one dc magnetic field and two (probe and coupling) ac resonant magnetic field. The results show that OB can be controlled efficiently by adjusting the intensity of the control field, the detuning of probe magnetic field and the cooperation parameter. Furthermore, within certain parameter range, the optical multistablity (OM) can also be observed in the crystal medium. This investigation can be used for designing new types of nonelectronic devices for realizing switching process.     

Incoherent control of optical bistability in an InGaN/GaN quantum dot nanostructure

The manipulation of bistable curve in the infrared (IR) region has been investigated theoretically in a unidirectional ring cavity doped by a four-level InGaN/GaN quantum dot nanostructure. The four-level quantum dot nanostructure is designed numerically by using the Schrödinger and Poisson equations. By controlling the size of the quantum dot and external voltage, one can design a four-level quantum dot with appropriate energy levels which can be suitable for interaction with IR signals. It is realized that the incoherent pumping fields play an essential role in controlling the intensity threshold of optical bistability. Decoherence effects such as the dephasing rate and electron density of the quantum dot are also analyzed at the threshold of optical bistability. Our proposed model due to its important application in all-optical systems may be favorable for real experimental evolution in infrared regions.     

Optical bistability and differential amplification in a tapered fiber coupler — microsphere resonator with nonlinear medium

We propose and study a coupling system composed of the tapered fiber and the microsphere with nonlinear medium. The optical bistability and differential amplification caused by optical Kerr effect is demonstrated using a geometrical method. We show that their operation characteristics can be controlled by parameters: linear phase detuning, attenuation coefficient and real amplitude coupling coefficient.     

非线性光学薄膜输出特性的研究

对单层、双层非线性光学薄膜的输出特性进行数值计算,发现材料非线性特性对光学双稳态输出特性影响较大,而选择合适的双层结构可以获得较低的双稳态阈值光强以及光放大作用。双层非线性光学薄膜间的距离以及入射光的准直性极大地影响着双稳态输出特性.     

非线性包层多量子阱波导的TE波

给出用以分析非线性包层多量子阱波导ＴＥ模光学非线性与双稳性的理论公式与计算方法。指出用均方根等效折射率法解本征方程是有效的简化方法。用本文方法分析了模折射率对波导总功率的依赖关系,芯区功率与总功率之间的双稳性以及模场分布与模折射率的关系。讨论了波导参数对光学非线性、双稳性及模场的分布的影响。     

Ultra-Low Threshold Optical Bistability and Multi-Stability in Dielecrtric Slab Doped with Semiconductor Quantum Well

A scheme for switching of the optical bistability (OB) and multi-stability (OM) in a dielectric slab doped with a three-level ladder-configuration n-doped semiconductor quantum well is simulated. It is shown that the bistable behavior of the system in dielectric slab can be controlled via amplitude or relative phase of applied fields. This optical system may provide some new possibilities for test the switching process.     

Optical bistability and multistability via double dark resonance in graphene nanostructure

Electrons in graphene nanoribbons can lead to exceptionally strong optical responses in the infrared and terahertz regions owing to their unusual dispersion relation.Therefore,on the basis of quantum optics and solid-material scientific principles,we show that optical bistability and multistability can be generated in graphene nanostructure under strong magnetic field.We also show that by adjusting the intensity and detuning of infrared laser field,the threshold intensity and hysteresis loop can be manipulated efficiently.The effects of the electronic cooperation parameter which are directly proportional to the electronic number density and the length of the graphene sample are discussed.Our proposed model may be useful for the nextgeneration all-optical systems and information processing based on nano scale devices.     

A bistable system with an electromagnetically induced grating

We propose a scheme of a bistable system with an electromagnetically induced grating and analyse the optical bistabilities in the system.The stationary equations describing the system have been derived.This bistable system shows typical hysteresis behaviour.     

A discrete-time model with non-monotonic functional response and strong Allee effect in prey

In this paper, we investigate the impact of strong Allee effect on the stability of a discrete-time predator–prey model with a non-monotonic functional response. The dynamics of discrete-time predator–prey models with strong Allee effect is studied earlier. But, the mathematical investigations of predator–prey dynamics in discrete-time set up with Holling type-IV functional response and strong Allee effect in prey are lacking. The proposed model supports the coexistence of two steady states, and the mathematical features of the model are analyzed based on local stability and bifurcation theory. By considering the Allee parameter as the bifurcation parameter, we provide sufficient conditions for the flip and the Neimark–Sacker bifurcations. We observe that Allee parameter plays a significant role in the dynamics of the system.     

Bistability of an iron-cobalt binuclear complex

Bistability of the four cis/trans isomers of the proposed iron-cobalt binuclear complex [(CO)₂(benzoate-)Fe^II/III(-terephthalate-)Co^III/II(-benzoate)(CO)₂]¹⁺, arising from the Fe^II/III ↔ Co^III/II intramolecular charge transfer (IMCT) is investigated computationally at (TD)DFT-B3LYP/LanL2DZ level of theory. Energies, geometries, atomic charges, and the UV-Vis spectra are considered in this investigation. Results approve IMCT bistability of all cis/trans isomers by locating two stable states with distinctly different structures and charge distributions (Fe^II-Co^III and Fe^III-Co^II oxidation states). Also, well-defined first-order saddle points between these two IMCT states are found and characterized using QST2/QST3 method. Based on the analysis of the calculated charge distributions and the 0.35-1.66 eV activation (barrier) energies of the Fe^II-Co^III ↔ Fe^III-Co^II IMCT reactions, it can be predicted that electric field or NIR radiation may be used to switch between the two IMCT states of this bistable binuclear complex. It is also found that the cis/trans isomerization has significant effects on the energetics of this IMCT reaction, and that the trans-Fe^II/III-trans-Co^III/II isomer is the best candidate for prospective switching application due to having the least energy dissipation and the largest charge transfer.