# Optical Intensity Discrimination with Engineered Interface States in Topological Photonic Crystals

## TL;DR

This paper introduces a new photonic crystal design using graphene that can control light intensity, offering potential for advanced laser technologies.

## Contribution

The novelty lies in using topological photonic crystals with nonlinear graphene layers to achieve intensity-dependent transmission.

## Key findings

- The structure supports a topologically protected Tamm plasmon polariton in the THz range.
- The design enables intensity-selective feedback for laser pulse shaping and passive pulse formation.
- The platform offers spectral scalability and electrical tunability via graphene biasing.

## Abstract

We propose a 1D photonic crystal with nonlinear graphene–spacer–graphene truncation, which enables a tunable, non-monotonic, and intensity-dependent transmission response. By employing synthetic geometrical space to obtain Fermi arc states, the structure is designed to support a real-space topologically protected Tamm plasmon polariton, revealing an intensity-dependent transmission peak within the THz spectral range. As such, the proposed thin-film structure may serve as a nonlinear DBR element that can be integrated into a laser cavity to provide intensity-selective feedback, thereby facilitating controllable pulse shaping and enabling passive pulse formation mechanisms such as mode-locking or Q-switching. Due to its topological robustness, spectral scalability, and electrical tunability via graphene biasing, the platform provides a new route toward compact, reconfigurable nonlinear reflectors for efficient and controllable laser pulse generation, thereby extending the functionality of conventional saturable absorbers and semiconductor DBRs.