Broadband Directive Thermal Emission with Dual Polarization

Achieving highly directive thermal emission across a broad spectral range remains a fundamental challenge in photonics. While recent advances have demonstrated broadband directional emission via Berreman modes, their operation is restricted to transverse-magnetic polarization. In this work, we present a framework for dual-polarized, spectrally broadband directive thermal emission by identifying the role of phase-matching leaky modes. By engineering the relative permittivity ratio between adjacent layers, broadband angular confinement is achieved without relying on strongly dispersive epsilon-near-zero resonances. A Si/Ge tandem structure supports dual-polarized directive emission inside a high-index medium, and a hemispherical extraction geometry preserves the emission angle upon outcoupling. This work provides a scalable strategy for broadband directional thermal emission in mid-infrared systems.