Sofia Evangelou

Strongly modified four-wave mixing in a coupled semiconductor quantum dot-metal nanoparticle system

We study the four-wave mixing effect in a coupled semiconductor quantum dot-spherical metal nanoparticle structure. Depending on the values of the pump field intensity and frequency, we find that there is a critical distance that changes the form of the spectrum. Above this distance, the four-wave mixing spectrum shows an ordinary three-peaked form and the effect of controlling its magnitude by changing the interparticle distance can be obtained. Below this critical distance, the four-wave mixing spectrum becomes single-peaked; and as the interparticle distance decreases, the spectrum is strongly suppressed. The behavior of the system is explained using the effective Rabi frequency that creates plasmonic metaresonances in the hybrid structure. In addition, the behavior of the effective Rabi frequency is explained via an analytical solution of the density matrix equations.

Modifying free-space spontaneous emission near a plasmonic nanostructure

We study theoretically the effects of the presence of a plasmonic nanostructure on free-space spontaneous emission in a four-level quantum system, where one V-type transition is influenced by the interaction with surface plasmons and the other V-type transition occurs in free space. The plasmonic nanostructure that we consider is a two-dimensional array of metal-coated dielectric nanospheres. We show that the spectrum of spontaneous emission in the free-space modes is strongly influenced by the presence of the plasmonic nanostructure, and we explore the dependence of the spectrum on different initial conditions of the quantum system and on the distance from the nanostructure.

Using interference effects for controlled light propagation in four-waveguide directional couplers

Abstract We explore interference effects that lead to interesting phenomena in arrays of four circularly coupled waveguides. These phenomena are shown by analytical solutions of the coupled mode equations and are verified by numerical solutions of the same equations. The interference is realized by proper design of the waveguides structure such that the propagation and the coupling constants obey specific conditions. We show that interference effects may lead to interesting phenomena, such as controlled light transfer as well as light trapping due to destructive interference.

Pulsed Four‐Wave Mixing in Intersubband Transitions of a Semiconductor Quantum Well: Effects of Pulse Shape

We study theoretically the phenomenon of pulsed four‐wave mixing in intersubband transitions of a symmetric semiconductor quantum well structure. In the theoretical model we consider two quantum well subbands that are coupled by a strong pulsed pump electromagnetic field and a weak pulsed probe electromagnetic field. For the description of the system dynamics we use the density matrix equations obtained from the effective nonlinear Bloch equations. We calculate the time‐integrated four‐wave mixing spectrum for various pulse shapes and electron sheet densities and study the effects of pulse shape on four‐wave mixing.