Saturation of the all-optical Kerr effect in solids

Abstract

We discuss the influence of the higher-order Kerr effect (HOKE) in wide bandgap solids at extreme intensities below the onset of optically induced damage. Using different theoretical models, we employ multiphoton absorption rates to compute the nonlinear refractive index by a Kramers-Kronig transform. Within this theoretical framework we provide an estimate for the appearance of significant deviations from the standard optical Kerr effect predicting a linear index change with intensity. We discuss the role of the observed saturation behavior in practically relevant situations, including Kerr lens mode-locking and supercontinuum generation in photonic crystal fibers. Furthermore, we present experimental data from a multiwave mixing experiment in BaF2, which can be explained by the appearance of the HOKE.

High-order nonlinear refractive indices for He, Ne, Kr, and Xe atoms

“…This comparison indicates that the frequency dependence of fourth-order nonlinear response becomes more dispersive when a smaller number of photons is required to reach the continuum. (15). The curve for argon is taken from data in Ref.…”

“…This observation prompted the HOKE hypothesis, ascribing the primary cause of defocusing to a crossover, a negative sign of the n 4 coefficient. To study the origins of the proposed saturation theoretically, Brée et al [14][15][16][17] exploited the nonlinear Kramers-Kronig (KK) relation [18] which expresses nonlinear refractive index in terms of the optical absorption coefficient derived from the Keldysh theory [19,20]. Finding evidence for the HOKE hypothesis, they proposed that the nonlinear index of refraction for noble gases saturates and becomes negative at intensities well below the threshold for ionization.…”

Third- and fifth-harmonic generation in transparent solids with few-optical-cycle midinfrared pulses

“…in the perturbative regime of laser-matter interaction provides a possibility of direct measurements of nonlinearoptical constants of the material, such as nonlinear-optical susceptibilities and optical nonlinearities. In the meantime, generation of low-order odd harmonics is attracting growing attention, since it might serve as an indicator enabling a test of the alleged role of the high-order Kerr effect and saturating nonlinearities in gaseous [20,21] and in solid-state media [22] in particular.…”

Modeling of ultrafast laser pulse propagation

“…However, to enable simulations on realistic scales corresponding to laboratory-scale NLO experiments, different methods must be devised, and a number of research groups pursue efforts in this direction (see e.g. [20][21][22][23][24][25][26] ). Here we want to describe a method proposed recently, that aims to bypass the need for repetitive solution of quantumsystem evolution.…”