Broadband Omni-resonant Coherent Perfect Absorption in Graphene

Abstract

Coherent perfect absorption (CPA) refers to interferometrically induced complete absorption of incident light by a partial absorber independently of its intrinsic absorption (which may be vanishingly small) or its thickness. CPA is typically realized in a resonant device, and thus cannot be achieved over a broad continuous spectrum, which thwarts its applicability to photodetectors and solar cells, for example. Here, we demonstrate broadband omni-resonant CPA by placing a thin weak absorber in a planar cavity and pre-conditioning the incident optical field by introducing judicious angular dispersion. We make use of monolayer graphene embedded in silica as the absorber and boost its optical absorption from ≈ 1.6% to ∼ 60% over a bandwidth of ∼ 70 nm in the visible. Crucially, an analytical model demonstrates that placement of the graphene monolayer at a peak in the cavity standing-wave field is not necessary to achieve CPA, contrary to conventional wisdom.

Ultra-thin metal-free terahertz absorber for electromagnetic shielding

“…The research work reported in this manuscript provides a way to implement the absorber based-on graphene for offering the broad absorption covering the lower THz frequency 0.1 10 -THz. The physical properties of isolated standing graphene sheet can dictate its utilization in obtaining the coherent perfect absorption (CPA) by the creation of quasi-CPA point in the lower THz regime [55,56]. The periodic array of the graphene patches can induce CPA in the isolated graphene sheet [57].…”

Spatial resolution of omni-resonant imaging

“…Resonantly enhanced linear and nonlinear optical effects can be consequently harnessed over a broad bandwidth. Indeed, we have utilized omni-resonance to realize broadband resonant coherent perfect absorption [15,16]. Omni-resonance is not to be confused with omni-directional resonances in metaldielectric-metal structures in which a wavelength resonates with the structure regardless of its incident angle [17,18].…”