# Ultrafast tunable modulation of light polarization at terahertz frequencies

## TL;DR

This paper demonstrates ultrafast, tunable control of visible light polarization using nonlinear interactions with terahertz pulses in LiNbO₃, enabling potential applications in material profiling and optical modulation.

## Contribution

It presents the first experimental evidence of nonresonant, noncollinear χ(2) nonlinear optical interaction for ultrafast polarization modulation at terahertz frequencies.

## Key findings

- Achieved efficient THz-induced polarization modulation of visible light.
- Validated theoretical models with experimental results.
- Potential for THz depth-profiling of materials.

## Abstract

Controlling light polarization is one of the most essential routines in modern optical technology. Since the demonstration of optical pulse shaping by spatial light modulators and its potential in controlling the quantum reaction pathways, it paved the way for many applications as a coherent control of the photoionization process or as polarization shaping of terahertz (THz) pulses. Here, we evidenced efficient nonresonant and noncollinear $\chi^{(2)}$-type light-matter interaction in femtosecond polarization-sensitive time-resolved optical measurements. Such nonlinear optical interaction of visible light and ultrashort THz pulses leads to THz modulation of visible light polarization in bulk LiNbO$_3$ crystal. Theoretical simulations based on the wave propagation equation capture the physical processes underlying this nonlinear effect. Apart from the observed tunable polarization modulation of visible pulses at ultrahigh frequencies, this physical phenomenon can be envisaged in THz depth-profiling of materials.