High-order optical processes: towards nonperturbative nonlinear optics

TL;DR

This paper introduces a nonperturbative approach to high-order nonlinear optical processes in strong fields, revealing new properties and potential for efficient XUV generation, supported by analytical and numerical results.

Contribution

It develops a theoretical framework for nonperturbative high-order nonlinear optics, including analytical solutions and new properties of these processes.

Findings

Agreement between numerical and analytical polarization calculations

Derivation of propagation equations for high-order wave-mixing and amplification

Identification of super-exponential growth solutions in high-order processes

Abstract

We develop an approach describing nonlinear-optical processes in the strong-field domain characterized by the nonperturbative field-with-matter interaction. The polarization of an isolated atom in the external field calculated via the numerical solution of the time-dependent Schr\"odinger equation agrees with our analytical findings. For the practically important case of one strong laser field and several weaker fields we derive and analytically solve propagation equations describing high-order (HO) wave-mixing, HO parametric amplification and HO stimulated scattering. These processes provide a way of efficient coherent XUV generation. Some properties of HO processes are new in nonlinear optics: essentially complex values of the coefficients in the propagation equations, the super-exponential (hyperbolic) growing solutions, etc. Finally, we suggest conditions for the practical realization of these processes and discuss published numerical and experimental results where such processes could have been observed.