Chiro-plasmonic refractory metamaterial with titanium nitride (TiN) core–shell nanohelices

Abstract

Chiral metamaterials are obtained by assembling plasmonic elements in geometries with broken mirror symmetry, which can have promising applications pertaining to generation, manipulation and detection of optical polarisation. The materials used to fabricate this promising nanosystem, especially in the visible-NIR regime, are limited to noble metals such as Au and Ag. However, they are not stable at elevated temperatures and in addition, incompatible with CMOS technologies. We demonstrate that it is possible to develop a chiro-plasmonic system based on a refractory material such as titanium nitride (TiN) which does not have these disadvantages. The building block of our metamaterial is a novel core-shell helix, obtained by coating TiN over silica nanohelices. These were arranged in a regular two-dimensional array over cm-scale areas, made possible by the use of scalable fabrication techniques such as laser interference lithography, glancing angle deposition and DC magnetron sputtering. The measured chiro-optical response was extremely broadband (<500 nm to >1400 nm), and had contributions from individual, as well as collective plasmon modes of the interacting nanohelices, whose spectral characteristics could be easily controlled by varying the direction of the incident radiation.

Gallium chiral nanoshaping for circular polarization handling

“…33,36 This effect can be exploited to envision controlled Ga-based 17,37-41 complex shape nanostructures with extremely high transmission selectivity with respect to circularly polarized light in the visible range. 30,42 In this work we employed silicon dioxide and amorphous carbon as host materials for the focused ion beam induced deposition and we obtained complex chiral deposits incorporating a high percentage of metallic Ga in the core alloy and dielectric host material in the shell alloy. Detailed structural composition analysis is presented to address the material complexity and as input for a customized numerical model, translating the observed nanocomposite structures into artificial material dispersions, to predict and fit optical experiments upon interaction with circularly polarized light.…”

Focused Ion Beam Processing for 3D Chiral Photonics Nanostructures

“…In what follows, we make a short comparison with other methods currently available for the fabrication of 3D chiral nanostructures or metasurfaces at the nanoscale: Glancing angle deposition (GLAD) [ 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 ], multi-step electron beam lithography (EBL) [ 136 , 137 , 138 , 139 , 140 , 141 ], DNA Self-assembly [ 142 , 143 , 144 , 145 , 146 ], nanoimprint lithography (NIL) [ 147 , 148 ], and direct laser writing (DLW) [ 149 , 150 , 151 , 152 , 153 , 154 ].…”

“…GLAD provides a large material choice, varying from metals to dielectrics exploited to modulate the chiro-optical response from visible to UV [ 129 , 130 , 131 , 132 ]. Recently, for example, chiral nanostructures in refractory material (titanium nitride) arranged in a regular large-area array and dispersed in solution have been studied [ 127 ]. The measured chiro-optical response is demonstrated to be very broadband (from 500 to 1400 nm) with contributions from individual and collective plasmon modes.…”

Self-Assembled Dichroic Plasmonic Nitride Nanostructures with Broken Centrosymmetry for Second-Harmonic Generation

“…Consequently, plasmonic nanostructures consisting of Au or Ag that are capable of SHG are based on metamaterials with non-centrosymmetric shapes [98,[100][101][102]. In the same context, TiN was implemented as a conventional metal component of noncentrosymmetric metamaterials, such as split-ring resonators [103] and chiral core-shells [104] for SHG, regardless of its own intrinsic broken centrosymmetry. So far, there is no report on optical non-linearities of ZrN whatsoever.…”