Ultra-broadband and efficient surface plasmon polariton launching through metallic nanoslits of subwavelength period

Ultra-broadband, efficient and unidirectional surface plasmon polariton (SPP) launching is of great concern in plasmonic devices and circuits. To address this challenge, a novel method adopting deep-subwavelength slits of subwavelength period (lambda(SPP)/4 similar to lambda(SPP)/3) in a thick metal film and under backside illumination is proposed. A new band pattern featuring broadband and wide angular characteristics, which is due to the coupling of the zeroth-order SPP resonance at the superstrate-metal interface and the first-order SPP resonance at the metal-substrate interface, is observed for the first time in the dispersion diagram. Unidirectional SPP launching efficiency of similar to 50%, ultra-broad bandwidth of up to 780 nm, covering the entire optical fiber communication bands, and relatively wide angular range of 7 degrees are achieved. This remarkable efficient, ultra-broadband and wide angular performance is demonstrated by carefully designed experiments in the near infrared regime, showing good agreement with numerical results.Multidisciplinary SciencesSCI(E)PubMed2ARTICLEjszhang@pku.edu.cn5914