Summary form only given. Optical bistability is basically a nonlinear response of the medium (here confined electrons in a QW) to an external oscillating field, in which there are three possible responses (two stable and one unstable). Which one the system chooses depends on the history of the adiabatically varying control parameters (usually electric field amplitude). The OB we consider is an intrinsic feature of the electron gas in the QW, and does not rely on the use of a Fabry-Perot resonator. Another feature of OB is that it is not a ubiquitous nonlinear response such as superharmonic generation; it can be observed only at some restricted values of the parameters. Furthermore the nonlinear response changes abruptly from one value of the output to the other. This effect can be measured by detecting the different transmitted intensities of the FIR field to the same input field. These features of OB make it a relevant choice for applications to optical switching and the realization of optical logic gates.
Summary form only given. Optical bistability is basically a nonlinear response of the medium (here confined electrons in a QW) to an external oscillating field, in which there are three possible responses (two stable and one unstable). Which one the system chooses depends on the history of the adiabatically varying control parameters (usually electric field amplitude). The OB we consider is an intrinsic feature of the electron gas in the QW, and does not rely on the use of a Fabry-Perot resonator. Another feature of OB is that it is not a ubiquitous nonlinear response such as superharmonic generation; it can be observed only at some restricted values of the parameters. Furthermore the nonlinear response changes abruptly from one value of the output to the other. This effect can be measured by detecting the different transmitted intensities of the FIR field to the same input field. These features of OB make it a relevant choice for applications to optical switching and the realization of optical logic gates.
Optical bistability (OB) can be defined as the existence of two stable states for one set of optical input conditions. It can be seen in many different systems which generally combine some microscopic nonlinearity (e.g., intensity-dependent refractive index) with some macroscopic feedback (e.g., a Fabry-Perot cavity). OB shows not only hysteresis but also switching transitions. By adjusting the degree of feedback various related effects are also possible (e.g., optical limiters, optical transistors, and several kinds of oscillation phenomena).
The effects of optical field on the phenomenon of optical bistability (OB) are investigated in a K-type semiconductor double quantum well (SDQW) under various parametric conditions. It is shown that the OB threshold can be manipulated by increasing the intensity of coupling field. The dependence of the shift of OB hysteresis curve on probe wavelength detuning is then explored. In order to demonstrate controllability of the OB in this SDQW, we compare the OB features of three different configurations which could arise in this SDQW scheme, i.e., K-type, Y-type, and inverted Y-type systems. The controllability of this semiconductor nanostructure medium makes the presented OB scheme more valuable for applications in all-optical switches, information storage, and logic circuits of all optical information processing.
Abstract Optical bistability (OB) is a phenomenon that describes a light induced phase transition in the non-equilibrium state. It is vital for all-optical computing and communication, serving as the basis for switches, logic gates, transistors, and memory. By enabling two stable light states, OB allows storage and fast switching, making high-speed, energy-efficient data processing possible. In this work we study the phenomenon in a two-band semiconductor in an optical cavity. Starting from a many-body Hamiltonian of optically generated electrons, holes and light-semiconductor interaction and Coulomb electron–electron, hole–hole and electron–hole interactions, we obtain the optical Bloch equations, in the mean field approximation, where relaxation is included phenomenologically. We obtain expressions for particle density, excitonic pair density and output intensity as non-linear functions of input light intensity. All these quantities show bistable behaviour, with two stable phases, and hysteresis in the non-equilibrium state. Equilibrium is ensured by introducing damping terms for the particle density amplitude, excitonic density amplitude, and cavity photon amplitude phenomenologically. The electron–hole pairs increase with light intensity, shows bistable features and then disappears with further increase in the input light intensity. The bistable behaviour becomes pronounced as we pass from low Coulomb interaction strengths to high Coulomb interaction strengths between electrons and holes. For sub-bandgap excitations, the output light versus incident light shows a complex behaviour.
When the output parameter of an optical device could be a multivalued function of the input parameter, this device can be working in an optical bistable status. The most typical optical bistable device is a Fabry–Perot cavity containing a nonlinear optical medium, the refractive index of which depends on the light intensity. Upon the action of an intense input optical beam, the transmitted (or reflected) intensity of this device may exhibit a nonlinear response to the incident light intensity variation and, especially under appropriate working conditions, the characteristic output/input curve may manifest a single (or multiple) hysteresis loop(s). Such type of optical bistable device can be used as an optical differential amplifier, optical switch, optical limiter, optical clipper, optical discriminator, or an optical memory element, depending on the chosen nonlinear medium and operation conditions.
Abstract Optical bistability (OB) and optical multistability (OM) due to wide applications in all-optical switching and transistors is studied in this paper. Here, we study the OB and OM properties of incident light in a defect slab doped by a GaAs quantum well (QW) nanostructure. It is shown that OB and OM features can be manipulated by spin coherence created by circular polarized laser fields in GaAs QWs. The impacts of laser field features, such as intensity, frequency detuning, and relative phase, on OB and OM are simulated. Moreover, the dependence of OB and OM features of a probe light on the thickness of the slab, then, are analyzed. It is found that the thickness of the slab can provide a new way to optimize the intensity threshold of OB and OM. We hope that our proposed model may be useful for developing all-optical devices on nanoscales.
A compact design for semiconductor cavities including coupled AlGaN/AlGaAs quantum wells is proposed for all-optical switching of the bistability process. First, physical and geometrical parameters are optimized to engineer the conducting electrons' energy levels in the quantum wells. Then, finite element simulations based on Schrödinger equations are executed to estimate the states of the charge carriers for AlGaN/AlGaAs as the active region. Next, the optical coupling and pumping fields are applied to the active region to both initiate the bistability and facilitate its real-time control. The Maxwell-Bloch approach based on rotating-wave approximation is employed to analyze the optimal conditions for controlling the behavior of optical bistability (OB). It is found that the threshold of OB can be optimized to have low values by tuning the intensity of coupling fields and the rate of an incoherent pumping field. This provides a fast real-time switching facility to control output intensity of the systems. The proposed scheme could have potential applications in optical memories, in which it is paramount to have active control over the readout of the system's quantum states. Thanks to the high nonlinear response of semiconductors, the featured device would be a prospective candidate for on-chip ultrasubluminal wave propagation studies and narrowband real-time switching and filtering applications.