Absorption studies in dipole–dipole interacting nanoparticles doped in nonlinear photonic crystals

Abstract

The dipole–dipole interaction has been studied in nonlinear photonic crystals doped with nanoparticles. The crystal is made from nonlinear dielectric spheres and the refractive index of spheres can be changed upon application of a strong pulsed laser (pump) field. The background material is taken as a linear dielectric material whose refractive index does not change. Three energy levels of nanoparticles are considered in the study of the absorption process. One of the transitions of the nanoparticles is resonantly coupled with a defect mode located at the middle of the gap. The time-dependent Schrödinger equation method is used to calculate the absorption coefficient. Numerical simulations for the absorption coefficient are carried out. It is observed that the absorption spectrum has two peaks and a minimum at zero detuning in the absence of the DDI. However, in the presence of the DDI, two peaks disappear and a peak appears near the zero detuning. When the pump field is applied, the peak near the zero detuning disappears and a new peak appears at a different detuning location. This happens because the refractive index of the system changes due to the pump field and in turn the location of the defect mode changes. This means that pump field and the dipole–dipole interaction can be used to switch the location of the absorbing peak. These properties can be used to make new types of optical devices.