Ultra‐narrowband and highly‐directional THz thermal emitters based on the bound state in the continuum
Kaili Sun, Zongshan Zhao, Yangjian Cai, Uriel Levy, Zhanghua Han
Abstract
Abstract The development of novel and cost‐effective THz emitters, with properties superior to current THz sources, is an active and important field of research. In this work, we propose and numerically demonstrate a simple yet effective approach of realizing terahertz sources working in continuous‐wave form, by incorporating the new physics of bound state in the continuum (BIC) into thermal emitters. By deliberately designing the structure of slotted disk array made of high‐resistivity silicon on top of a low index dielectric buffer layer supported by a conducting substrate, a quasi‐BIC mode with ultra‐high quality factor (∼10 4 ) can be supported. Our results reveal that the structure can operate as an efficient terahertz thermal emitter with near‐unity emissivity and ultranarrow bandwidth. For example, an emitter working at 1.3914 THz with an ultranarrow linewidth less than 130 MHz, which is roughly 4 orders of magnitude smaller than that obtained from a metallic metamaterial‐based thermal emitter, is shown. In addition to its high monochromaticity, this novel emitter has additional important advantages including high directionality and linear polarization, which makes it a promising candidate as the new generation of THz sources. It holds a great potential for practical applications where high spectral resolving capability is required.