Controlling water giant low-inertia nonlinear refractive index in the THz frequency range via temperature variation

To create self-controlled radiation photonics systems, it is necessary to have complete information about the nonlin-ear properties of the materials used. In this Letter, the vibrational mechanism of the giant low-inertia cubic non -linearity of the refractive index of water in the terahertz (THz) frequency range is experimentally proven. Its domi-nance, which manifests itself when the temperature of the liquid changes, is demonstrated. The measured nonlinear refractive index in the THz frequency range for a water jet at temperatures from 14 degrees C to 21 degrees C demonstrates a cor-relation with the theoretical approach, varies in the range 4-10 x 10(-10) cm(2)/W, and is characterized by an inertial time constant of less than 1 ps. (c) 2023 Optica Publishing Group

Automated summary

In order to create self-controlled radiation photonics systems, it is essential to understand the nonlinear properties of the materials used. This study experimentally proves the vibrational mechanism of the giant low-inertia cubic nonlinearity of the refractive index of water in the terahertz frequency range. It demonstrates the dominance of this phenomenon when the temperature of the water changes.