Graphene-tuned nonreciprocal thermal emitter under near-normal illumination

• A thermal radiator is presented with dual-band nonreciprocal properties at an near-normal incidence angle of 0.65°. • The performance can be dynamically tuned by the external magnetic field and graphene's Fermi level, offering precise control over the operational wavelength. • The nonreciprocal thermal radiation is elucidated through the analysis of normalized magnetic field energy distribution and validated using coupled mode theory. • The thermal radiator provides a robust approach for thermal management and energy conversion applications, especially suitable for small-angle incidence scenarios. Nonreciprocal thermal radiation has emerged as a research hotspot in recent years, with the majority of studies focusing on TM polarization and large-angle incidence. In this paper, we introduce a nonreciprocal thermal radiator composed of graphene integrated with a two-dimensional silicon-based grating, magneto-optical material (InAs), and a metallic reflective layer (Al). We demonstrate dual-band nonreciprocal thermal radiation under TE polarization at an incidence angle of 0.65°. The physical properties of nonreciprocal thermal radiation are elucidated and validated using the coupled mode theory (CMT). Additionally, the peak position can be dynamically adjusted within the operational wavelength range by controlling the external magnetic field and the Fermi level of graphene. This work holds potential for applications in the field of energy conversion and provides a novel approach for nonreciprocal thermal radiation devices at small angles of incidence.