We investigate the Goos-Hänchen-like shifts for Dirac fermions in transmission through a monolayer graphene barrier. The lateral shifts, as the functions of the barrier's width and the incidence angle, can be negative and positive in Klein tunneling and classical motion, respectively. Due to their relations to the transmission gap, the lateral shifts can be enhanced by the transmission resonances when the incidence angle is less than the critical angle for total reflection, while their magnitudes become only the order of Fermi wavelength when the incidence angle is larger than the critical angle. These tunable beam shifts can also be modulated by the height of potential barrier and the induced gap, which gives rise to the applications in graphene-based devices.
We have investigated the transmission in monolayer graphene barrier at non-zero angle of incidence. Taking the influence of parallel wave vector into account, the transmission as the function of incidence energy has a gap due to the evanescent waves in two cases of Klein tunneling and classical motion. The modulation of the transmission gap by the incidence angle, the height and width of potential barrier may lead to potential applications in graphene-based electronic devices.
Defect-embedded chiral nematic organizations are attractive due to their light manipulation ability that is crucial for photonic applications. Self-assembly of cellulose nanocrystals (CNC) forms a left-handed chiral nematic structure, which makes simultaneous reflection of left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light a challenging task. Herein, we present unprecedented evidence that self-organized CNC films with left-handed helical sense and photonic bandgaps (PBG) display ambidextrous CP light reflection with peak reflectivity up to 68% and transform spontaneous photoluminescence to RCP and LCP luminescence with respective |g lum | values up to 0.796 and 0.120. These ambidextrous chiroptical properties originate from a left-handed chiral nematic structure consisting of a nematic-like phase, acting as a half-wave retarder, sandwiched between two PBG layers. The latter are spontaneously intercalated into the left-handed helicoids by rapid gelation of CNC colloidal suspensions. We demonstrate that the ambidextrous chiroptical properties can be manipulated by changes in evaporation temperatures, concentrations, and characteristics of CNC suspensions. We showcase the potential of defect-embedded chiral nematic CNC films for the sustainable and scalable development of anti-counterfeiting optical labels.
Hierarchical zeolite sponges with a nanotube scaffolding architecture, nanotube-trimodal connectivity and self-generated nanotubes with tunable geometry.
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