Unidirectional ultrabroadband and wide-angle absorption in graphene-embedded photonic crystals with the cascading structure comprising the Octonacci sequence

Abstract

Using the transfer matrix method, a unidirectional absorber with an ultrabroadband absorption bandwidth and angular stability is realized in the graphene-embedded photonic crystals (GPCs) arranged by the cascading structure formed with the periodic sequence and the quasi-periodic Octonacci sequence in the terahertz regime. As a result, the surface conductivity of the graphene sheet can be modulated via the chemical potential, and the characteristics of the proposed absorber are tunable. Compared to the structure spliced by the diverse periodic sequences, the relative absorption bandwidth of the proposed composite construction is up to 94.53%, which far outweighs that of the periodic one. We compare the Octonacci sequence, the Fibonacci sequence, and the Thue–Morse sequence, and the calculated results reveal the advantage of the Octonacci sequence in the expansion of the absorption bandwidth. Under the optimization of the related parameters, the incident wave is primarily reflected in the forward propagation and absorbed in a wide range of θ under the TM mode in backward propagation, which shows the splendid unidirectionality and angular stability. The impacts of the chemical potential, structural thicknesses, and stack numbers on the absorption properties are also investigated in detail. Additionally, the impedance match theory and the interference field theory are introduced to explain the intrinsic absorption mechanism of the presented GPCs. In short, the unidirectional broadband and angle-insensitive absorber has extensive application prospects in optical sensing, optical filtering, photodetection, and solar energy collection.

Multiplication of photonic band gaps in one-dimensional photonic crystals by using hyperbolic metamaterial in IR range

“…Photonic crystals (PCs) have received a lot of interest since their invention because of their ability to control light propagation 1 – 3 . One key characteristic of PCs is the photonic bandgap (PBG) which prevents light propagation in its waveband 4 , 5 . Because of their unique features, PCs are utilized to create optical devices such as reflectors 6 – 8 , lasers 9 , 10 , fibers 11 , 12 , and tunable optoelectronic devices 13 – 15 .…”

Pattern-free solar absorber driven by superposed Fabry–Perot resonances

“…Multilayer structures have attracted significant attention in the past few years because of the advantages of simple structures and enhanced absorption. [37][38][39][40][41][42][43] It has been demonstrated that most previous studies into structures have focused on narrowband absorption. [44][45][46][47] Recently, Xie et al proposed a stacked Fabry-Perot (FP) multilayer structure for spacecraft thermal control that achieves a highly enhanced infrared emittance as well as emittance tunability.…”

Spatial Dispersion in Hypercrystal Distributed Feedback Lasing

“…Despite increasing number of studies in the field of nonlocal metamaterials, the effect of spatial dispersion on optical properties of photonic hypercrystals has not been yet discussed. Photonic hypercrystals (PHCs) are a novel class of metamaterials combining properties of photonic crystals and hyperbolic media [ 20 ] and revealing interesting properties, such as difractionless imaging [ 21 ], optical bistability [ 22 ], cloaking [ 23 ], or tunable broadband unidirectional absorption [ 24 ]. Recently, it has also been demonstrated that tunable lasing with voltage-controllable single mode generation is also possible in this class of structure [ 25 ].…”