Contribution of dipolar interactions to third-order nonlinear dielectric susceptibility of nanocomposites

Abstract

We consider an ensemble of identical semiconductor nanoparticles randomly embedded into dielectric matrix. The nanoparticles are polarized by the laser irradiation having linear polarization. The contribution of dipole-dipole interactions to third-order dielectric susceptibility is calculated by using mean random field method. It is shown that this contribution always has a negative sign, and it can be comparable with the values of optical nonlinearity observed experimentally.

Impact of interparticle dipole–dipole interactions on optical nonlinearity of nanocomposites

“…The expression for χ (3) calculated in Ref. [12] for the case of c → 0 is almost twice than χ (3) computed with Eq. (17) but the first was obtained under the rather rough limitation of the maximum field value in the use of the Cauchy-Lorentzian distribution.…”

“…A model describing the effect of the dipole-dipole interactions on the nonlinear optical properties of such nanocomposites was proposed in Ref. [12]. This model deals with the system of semiconductor nanoparticles randomly arranged in the dielectric matrix.…”

“…In Ref. [12], previously obtained distribution functions of the net dipolar field projection E [13] was utilized. For volume concentrations (volume fractions) of the excited nanoparticles c > 0.1 the Gaussian distribution was used as distribution functions of the random field E. In this work, we employ for bulk samples the negative cumulant expansion proposed for the two-dimensional distribution of dipoles [14,15].…”

Effect of dipolar interactions on optical nonlinearity of two-dimensional nanocomposites

“…This field is random since the quantum dots are polarized arbitrarily and placed haphazardly. After obtaining the probability distribution function W (E) for the projection E of the field E onto the selected direction, the contribution of the dipole-dipole interactions to the nonlinear dielectric susceptibility of the nanocomposite can be calculated with the help of the statistical mechanics methods [9]. Let us consider the monolayer of cylindrical particles that lie randomly in a plane.…”

“…Hence, we cannot apply directly the approach of Ref. [9] exploiting the Gaussian distribution for the calculation of the third-order dielectric susceptibility as such high surface nanoparticle concentrations are hardly achievable in practice. In order to obtain W (E) at c < 0.6, making use of the negative cumulant expansion followed by the inverse Fourier transform was proposed [15]:…”