Ultra-broadband directional thermal emission

• Published in: Nanophotonics (Berlin, Germany) Germany), 2024-03, Vol.13 (5), p.793-801
• Main Authors: Wang, Qiuyu, Liu, Tianji, Li, Longnan, Huang, Chen, Wang, Jiawei, Xiao, Meng, Li, Yang, Li, Wei
• Format: Article
• Language: English
• Subjects: Bandwidths; Broadband; broadband directional thermal emission; Directional control; Effective medium theory; Efficiency; Emitters; Laboratories; metamaterial; Multilayers; Neutrons; Photonics; Physics; Radiation; Thermal emission; Thermal utilization
• ISSN: 2192-8614; 2192-8606; 2192-8614
• DOI: 10.1515/nanoph-2023-0742

Directional control of thermal emission over its broad wavelength range is a fundamental challenge. Gradient epsilon-near-zero (ENZ) material supporting Berreman mode has been proposed as a promising approach. However, the bandwidth is still inherently limited due to the availability of ENZ materials covering a broad bandwidth and additional undesired omnidirectional modes in multilayer stacking with increased thickness. Here, we show that broadband directional thermal emission can be realized beyond the previously considered epsilon-near-zero and Berreman mode region. We then establish a universal approach based on effective medium theory to realizing ultra-broadband directional thermal emitter. We numerically demonstrate strong (emissivity >0.8) directional (80 ± 5°) thermal emission covering the entire thermal emission wavelength range (5–30 μm) by using only two materials. This approach offers a new capability for manipulating thermal emission with potential applications in high-efficiency information encryption, energy collection and utilization, thermal camouflaging, and infrared detection.