Electrically reconfigurable polarization control with double tri-layer black phosphorus heterostructures

Accessing diverse polarization states across the Poincaré sphere via electrical control is highly desirable in optical communications, bio-imaging and quantum information processing, where fast continuous switching, compactness, and ease of integration into photonikic circuits are essential. Layered anisotropic 2D materials enable polarization modulation in a fast and compact manner, thereby overcoming the speed and size limitations of liquid-crystal based spatial light modulators and electro-optic Pockels cell modulators. Here, we report a Fabry-Perot cavity that integrates two cross-aligned black phosphorus layers, with each layer being independently gated to access the inherently two-dimensional range of polarization states across the Poincaré sphere surface. Our heterostructure design predicts electronic access to 86% of the Poincaré sphere at its S-band operating wavelength. We experimentally validate the design by fabricating and testing such a device in reflection, where we demonstrate independent, two-parameter electronic control of the output polarization. Layered anisotropic 2D materials hold potential for the realization of compact polarization modulators. Here, the authors realize a Fabry-Perot cavity integrating two orthogonally stacked and independently gated black phosphorus trilayers, showing tunable polarization control and predicting electronic access to up to 86% of the Poincaré sphere.