# Absorption and opacity threshold for a thin foil in a strong circularly polarized laser field

## TL;DR

This paper refines the transparency threshold for thin foils in strong circularly polarized laser fields by introducing a new analytical model that accounts for laser absorption, aligning well with simulations and impacting experimental configurations.

## Contribution

A new analytical model for laser absorption in thin foils that refines the transparency threshold considering multiple parameters beyond laser amplitude.

## Key findings

- Refined transparency threshold matches PIC simulations.
- Opaque foils steepen pulse fronts, affecting applications.
- Multiple parameters influence laser foil transparency.

## Abstract

We show that a commonly accepted transparency threshold for a thin foil in a strong circularly polarized normally incident laser pulse needs a refinement. We present a new analytical model, which correctly accounts for laser absorption. The refined threshold is determined not solely by the laser amplitude, but other parameters are equally or even more important. Our predictions are in a perfect agreement with PIC simulations. The refined criterion is crucial for configuring laser plasma experiments in the high field domain. Besides, an opaque foil steepens the pulse front, this can be important for numerous applications.