ABSTRACT
Control of directionality of emissions is an important task for the realization of novel nanophotonic devices based on nanowires. Most of the existing approaches providing high directionality of the light emitted from nanowires are based on the utilization of the tapered shape of nanowires, serving as nanoantenna coupling with the light waveguided in nanowire and the directional output beam. Here we report the beaming of the emitted light with wavelength near 800 nm by naturally formed core-shell AlGaAs NW with multiply GaAs quantum dots (QDs) diameter 30 nm and height 10 nm, while the diameter of NW 130 nm, what does not support efficient emission into waveguided modes, including the mode HE11. Experimental measurements show that intensity of emission for directions in the vicinity of the axis of NW is about two orders of magnitude higher than for perpendicular directions. The developed theoretical approach allowed us to calculate the probability of spontaneous emission for various directions and into waveguided modes and showed that highly directional radiation can be provided by the intrinsic emission properties of cylindrical NW. Our results suggest that for the small diameter of NW, directional emissions are associated with an TM0 leaky mode (when electric field oriented in axial direction) and therefore manifests in an existence of axial electric dipole transitions in quantum dots.
ABSTRACT
Interaction of cavity modes with an exciton in a meso-cavity (the structure supporting several cavity modes separated by an energy interval comparable to Rabi-splitting of an exciton and cavity modes) has been analyzed using a quantum-mechanical approach. Simultaneous interaction of an exciton and several cavity modes results in few novel effects such as ladder-like increase of the exciton population in the system, quantum beating and non-monotonic dependence of the ground polariton state in the system on the pumping.
ABSTRACT
The scheme of a generation of ultrasound waves based on optically excited Tamm plasmon structures is proposed. It is shown that Tamm plasmon structures can provide total absorption of a laser pulse with arbitrary wavelength in a metallic layer providing the possibility of the use of an infrared semiconductor laser for the excitation of ultrasound waves. Laser pulse absorption, heat transfer and dynamical properties of the structure are modeled, and the optimal design of the structure is found. It is demonstrated that the Tamm plasmon-based photoacoustic generator can emit ultrasound waves in the frequency band up to 100 MHz with predefined frequency spectrum.
ABSTRACT
The interaction of an exciton and cavity modes is considered in planar meso-cavities, which have lateral sizes corresponding to few wavelengths. In meso-cavities, the frequency interval between the optical modes is comparable or smaller than the value of the Rabi splitting between the exciton and the optical modes. The Hamiltonian of the interaction between the exciton and the cavity modes is constructed, and it is shown that such an interaction between the cavity modes and the exciton can occur both in weak and in strong coupling regimes. The latter case can be accompanied by a pronounced splitting of the emission peaks as shown for modelled meso-cavities of triangular, square and hexagonal shapes, where it is demonstrated that Q-factors for the adjacent cavity modes as well as the strength of interaction with excitons can differ by few orders of magnitude.
