# Simultaneous polarization transformation and amplification of multi-petawatt laser pulses in magnetized plasmas

## TL;DR

This paper introduces a plasma waveplate that can simultaneously transform laser polarization and amplify petawatt laser pulses using magneto-optical effects in plasma, enabling high-power laser manipulation beyond solid-state limits.

## Contribution

It proposes a novel plasma-based waveplate capable of polarization transformation and power amplification for ultra-high-power lasers, demonstrating numerical feasibility for petawatt-scale pulses.

## Key findings

- Converts 5 PW linearly polarized laser to >10 PW circularly polarized pulse.
- Achieves about 98% energy conversion efficiency.
- Waveplate thickness scales inversely with plasma density and magnetic field strength.

## Abstract

With increasing laser peak power, the generation and manipulation of high-power laser pulses becomes a growing challenge for conventional solid-state optics due to their limited damage threshold. As a result, plasma-based optical components which can sustain extremely high fields are attracting increasing interest. Here, we propose a type of plasma waveplate based on magneto-optical birefringence under a transverse magnetic field, which can work under extremely high laser power. Importantly, this waveplate can simultaneously alter the polarization state and boost the peak laser power. It is demonstrated numerically that an initially linearly polarized laser pulse with 5 petawatt peak power can be converted into a circularly polarized pulse with a peak power higher than 10 petawatts by such a waveplate with a centimeter-scale diameter. The energy conversion efficiency of the polarization transformation is about $98\%$. The necessary waveplate thickness is shown to scale inversely with plasma electron density $n_e$ and the square of magnetic field $B_0$, and it is about 1 cm for $n_e=3\times 10^{20}$ cm$^{-3}$ and $B_0=100$ T. The proposed plasma waveplate and other plasma-based optical components can play a critical role for the effective utilization of multi-petawatt laser systems.