Retrieving nonlinear refractive index of nanocomposites using finite-difference time-domain simulations

Abstract

In this Letter, a method is proposed that utilizes three-dimensional finite-difference time-domain simulations of light propagation for restoring the effective Kerr nonlinearity of nanocomposite media. In this approach, a dependence of the phase shift of the transmitted light on the input irradiance is exploited. The reconstructed values of the real parts of the nonlinear refractive index of a structure of randomly arranged spheres are in good agreement with the predictions of the effective medium approximations.

Giant Enhancement and Sign Inversion of Optical Kerr Nonlinearity in Random High Index Nanocomposites near Mie Resonances

“…As the size of particles approaches the Mie resonances, the shape of the Gaussian beam transmitted through the specimen is considerably distorted so the size of the FDTD computational domain should be enlarged in comparison to ref. [9] in order to obtain the stable results. The size of the computational domain for simulations was µm with the space resolution of 5 nm.…”

“…Recently, there was proposed a method of restoration of the effective Kerr nonlinearity of nanocomposite media on the base of 3D finite‐difference time‐domain (FDTD) simulations of light propagation. [ 9 ] This technique exploits the phase change induced by the studied sample to the transmitted Gaussian beam. This phase change is computed for different intensities of the Gaussian beam enabling one to estimate the real parts of the nonlinear refractive index of the sample.…”

“…In this work, the procedure presented in ref. [9] is applied to evaluation of the effective nonlinear refractive index of the random nanocomposite containing identical spherical high index inclusions with sizes close to the lowest Mie resonances. The term “effective” for inclusions with sizes close to the Mie resonances should not be understood in the sense of the effective medium.…”

Possibility of negative refraction for visible light in disordered all-dielectric resonant high index metasurfaces

“…To obtain the similar accuracy of n, the method based on the calculation of the S parameters requires approximately twice the computational domain compared to that used in Ref. [12]. Moreover, the error of restoration of the effective extinction coefficient of GaP nanocomposite using S parameters always ex- * Electronic mail: panov@iacp.dvo.ru ceeds the estimated value owing to low GaP extinction coefficient in the visible range.…”

Optical Kerr Nonlinearity of Disordered All-Dielectric Resonant High Index Metasurfaces with Negative Refraction

“…The procedure of computation of the real part of the effective nonlinear refractive index of the monolayer nanocomposites is described in depth in Ref. [10]. In this procedure, the simulated Gaussian beam falls at normal incidence on the slab specimen with intensity-dependent index of refraction n = n 0 + n 2 I, where n 0 is the linear refractive index, n 2 is the secondorder nonlinear refractive index, and I is the intensity of the wave.…”