Artificial Propeller Chirality and Counterintuitive Reversal of Circular Dichroism in Twisted Meta-molecules

Abstract

Here we demonstrate an optical propeller chirality in artificially twisted meta-molecules, which is remarkably different from conventional optical helical chirality. Giant circular dichroism (CD) is realized in a single layer of meta-molecule array by utilizing the surface lattice resonances that are formed by the coupling of chiral electric quadrupole modes to the diffractive lattice mode. Due to the special twist of the propeller blades, the periodic meta-molecule array is hybridized by unit cells with two different chiral centers. As a result, the CD response is readily reversed by tailoring the interference phase through engineering the structural blades without inverting the geometric chirality. Importantly, the enhanced CD and its sign reversal are demonstrated in experiments by using a nano-kirigami fabrication technique.

Tunable Reversal of Circular Dichroism in the Seed-Mediated Growth of Bichiral Plasmonic Nanoparticles

“…Bichiral structures normally exhibit two CD responses with opposite signs at different wavelengths when consisting of two isolated chiral centers with opposite handedness. 61,62 Interestingly, the two chiral centers are not completely isolated from each other in our cases; their chiral units share the same twisted blade edge as marked with both red-and blue-dotted lines (Figure S7). Therefore, the CD responses of the overall plasmonic structure could be the results of the plasmon hybridization of two chiral units because they are intertwined and coupled with each other.…”

“…64,69,70 More interestingly, by tuning the coupling and competition between two chiral centers with opposite handedness, the CD signal of the propeller meta-molecules array can be reversed without the inversion of the geometric chirality. 61,62 The propeller structure with bichiral centers was designed and fabricated by using a focused ion beam (FIB) based nanokirigami method. 61 For chiral plasmonic NPs prepared by seedmediated growth method, a single chiral center was proposed in most cases with the limitation of tuning the CD reversal.…”

“…61,62 The propeller structure with bichiral centers was designed and fabricated by using a focused ion beam (FIB) based nanokirigami method. 61 For chiral plasmonic NPs prepared by seedmediated growth method, a single chiral center was proposed in most cases with the limitation of tuning the CD reversal. 11,20,44,45,49 How to create multiple chiral centers on an individual plasmonic NPs using wet chemical approaches, particularly the seed-mediated chiral growth method, remains a fundamentally intriguing open question.…”

Switchable Multifunctional Terahertz Metamaterials Based on the Phase-Transition Properties of Vanadium Dioxide

“…In 2007, Hao et al [ 22 ] proposed a reflective metamaterial for polarization conversion. Due to the advantages of thin thickness, low loss, and easy integration, metamaterial polarization converters quickly caught the attention of researchers [ 23 , 24 ]. In 2013, Grady et al [ 25 ] proposed a metamaterial polarization converter suitable for the THz frequency band, which greatly expanded the application frequency range of metamaterial polarization converters.…”

Metasurfaces Assisted Twisted α-MoO3 for Spinning Thermal Radiation

“…Greffet et al demonstrated that periodic microstructures could emit a coherent and linearly polarized wave [ 5 ], which offers significant promise for controlling the spectral, coherent and polarization properties of thermal radiation [ 11 , 12 , 13 ]. Spin polarized (circularly polarized) wave has gained extensive attention in chiral optics [ 14 , 15 , 16 ] and spin-controlled nanophotonics [ 17 , 18 , 19 ]; spin angular momentum is used to engineer spin-dependent nanoscale light-matter interactions. Recently, studies regarding chiral microstructures have demonstrated the feasibility of spin thermal radiation for engineering, including thermal detection [ 20 , 21 , 22 ].…”