Tailoring Quasi-Bound States in the Continuum for Infrared Photodetection in Black Phosphorus

TL;DR

This paper introduces a metasurface design with quasi-BICs to significantly enhance light absorption in black phosphorus, improving infrared photodetectors by leveraging high-quality resonances and preserving anisotropic properties.

Contribution

It demonstrates the integration of quasi-BIC resonances in dielectric metasurfaces with black phosphorus to boost optical absorption and device performance in infrared photodetection.

Findings

Enhanced electromagnetic field confinement within BP layer.

High-quality-factor resonances achieved through symmetry breaking.

Significant increase in photocarrier generation in BP.

Abstract

High-performance infrared photodetection underpins various applications spanning surveillance, environmental monitoring, optical communications and biomedical imaging. However, conventional bulk detectors remain limited by poor spectral tunability, mechanical rigidity, and high dark currents, motivating the pursuit of low-dimensional material platforms such as graphene and transition metal dichalgenides. Black phosphorus (BP) is particularly compelling in this context, owing to its thickness-tunable direct bandgap, high carrier mobility, and pronounced in-plane anisotropy. Nevertheless, its atomically thin nature inherently restricts light absorption, posing a fundamental bottleneck for device performance. Here, we demonstrate quasi-bound states in the continuum (quasi-BICs) within a dielectric metasurface integrated with BP, enabling strongly enhanced and spectrally selective light-matter interactions. By introducing controlled symmetry breaking at the unit-cell level, high-quality-factor resonances are realized, resulting in pronounced electromagnetic field confinement within the BP layer. This resonant enhancement substantially increases photocarrier generation while preserving the intrinsic polarization anisotropy of BP, which elucidates a robust pathway for overcoming the optical absorption bottleneck in anisotropic 2D optoelectronics via quasi-BIC platforms.