A motion-induced optical bistability is shown for a metal nanoparticle dimer that is plasmon coupled and bound with dispersion (colloidal) forces. The effect does not require any material nonlinearity.
Colloidally synthesized nanocubes strongly coupled to conducting films hold great promise for enhancing different nonlinear optical processes. They exhibit a robust and sensitive scattering response that can be easily controlled by their geometrical and material parameters. Strong local field enhancement is generated at the gap regions between the nanocubes and the metallic film. We show that strong optical bistability and all-optical switching behavior can be obtained by loading these nanogaps with Kerr nonlinear materials. Relatively low input intensities are required to obtain these nonlinear effects. The proposed design can lead to efficient, low-power, and ultrafast all-optical memories and scattering nanoswitches.
We conduct a theoretical study of the bistable optical response of a nanoparticle heterodimer comprised of a closely spaced semiconductor quantum dot and a metal nanoparticle. The bistable nature of the response results from the interplay between the quantum dot's optical nonlinearity and its self-action (feedback) originating from the presence of the metal nanoparticle. The feedback is governed by a complex valued coupling parameter G = G(R) + iG(I). We calculate the bistability phase diagram within the system's parameter space: spanned by G(R), G(I), and Δ, the latter being the detuning between the driving frequency and the transition frequency of the quantum dot. Additionally, switching times from the lower stable branch to the upper one (and vice versa) are calculated as a function of the intensity of the driving field. The conditions for bistability to occur can be realized, for example, for a heterodimer comprised of a closely spaced CdSe (or CdSe/ZnSe) quantum dot and a gold nanosphere.
We theoretically investigated optical third-order nonlinearity of a coherently coupled exciton-plasmon hybrid system under a strong control field with a weak probe field. The analytic formulas of exciton population and effective third-order optical susceptibility of the hybrid of a metal nanoparticle (MNP) and a semiconductor quantum dot (SQD) were deduced. The bistable exciton population and the induced bistable nonlinear absorption and refraction response were revealed. The bistability region can be tuned by adjusting the size of metal nanoparticle, interparticle distance and intensity of control field. Our results have perspective applications in optical information processing based on resonant coupling of exciton-plasmon.