Ultra-broadband, lithography-free, omnidirectional, and polarization-insensitive perfect absorber

Abstract Perfect absorbers (PAs) at near infrared allow various applications such as biosensors, nonlinear optics, color filters, thermal emitters and so on. These PAs, enabled by plasmonic resonance, are typically powerful compact, but confront inherent challenges of narrow bandwidth, polarization dependence, limited incident angles well requires using expensive lithographic process, which limit their practical mass production. In this work, we demonstrate a non-resonant PA that is comprised six continuous layers magnesium fluoride (MgF 2 ) chromium (Cr) in turns. Our device absorbs more than 90% light broad range 900–1900 nm. addition, planar design lithography-free, certainly independent with polarization, presents further advantage wide incidence up to 70°. The measured performance our optimized agrees analytical calculations transfer matrix method (TMM) numerical simulations finite element method, can be readily implemented for applications.