# Extreme optical nonlinearities unveiled by ultrafast laser filamentation in semiconductors

## TL;DR

This paper shows that ultrafast laser filamentation in semiconductors reveals extreme optical nonlinearities, enabling better control for photonic device fabrication.

## Contribution

The study demonstrates universal filamentation in semiconductors and derives new scaling laws for nonlinear parameters.

## Key findings

- Filamentation universally governs ultrashort laser pulse propagation in semiconductors.
- Nonlinear parameters differ significantly from low-intensity pulse measurements.
- Temporal-spectral shaping is proposed for controlled energy deposition in semiconductors.

## Abstract

Sky-high optical nonlinearities make semiconductors ideal platforms for multifunctional photonic devices. The fabrication of such complex devices could greatly benefit from in-volume ultrafast laser writing for monolithic and contactless integration. Ironically, as exemplified for Si, nonlinearities act as an efficient immune system that self-protects the material from internal permanent modifications. Predicting high-intensity ultrashort-pulse propagation beyond Si is further limited by incomplete descriptions of carrier dynamics in narrow-gap materials. Here, we demonstrate that filamentation universally dictates ultrashort laser pulse propagation in various semiconductors. The effective key nonlinear parameters extracted differ markedly from past measurements with low-intensity pulses, while temporal scaling laws for these parameters are also derived. Based on these findings, appropriate temporal-spectral shaping is proposed for tailored energy deposition inside semiconductors. The effective parameters also provide predictive inputs for semiconductor backside processing, microelectronics security, and high-harmonic, supercontinuum and terahertz wave generation.

Energy deposition inside silicon with ultrashort laser pulses is intrinsically restricted. Here, authors demonstrate that this filamentation-driven ceiling is universal in semiconductors. Extreme nonlinearities are quantified to predict and optimize involume laser-semiconductor interaction.