Plasmon-Induced Transparency in the Visible Region via Self-Assembled Gold Nanorod Heterodimers

Abstract

The phenomenon of plasmon-induced transparency holds immense potential for high sensitivity sensors and optical information processing due to the extreme dispersion and slowing of light within a narrow spectral window. Unfortunately plasmonic metamaterials demonstrating this effect has been restricted to infrared and greater wavelengths due to requisite precision in structure fabrication. Here we report a novel metamaterial synthesized by bottom-up self-assembly of gold nanorods. The small dimensions (≤ 50/20 nm, length/diameter), atomically smooth surfaces, and nanometer resolution enable the first demonstration of plasmon-induced transparency at visible wavelengths. The slow-down factors within the reduced symmetry heterodimer cluster are comparable to longer wavelength counterparts. The inherent spectral tunability and facile large-scale integration afforded by self-assembled metamaterials will open a new paradigm for physically realizable on-chip photonic device designs.

An actively ultrafast tunable giant slow-light effect in ultrathin nonlinear metasurfaces

“…A very large group index of 4 3 10 3 was obtained for the metasurface sample, one order of magnitude larger than those of previous reports. [6][7][8][9][10][11] Under the excitation of a 1.5 kW cm 22 pump laser (l 5 1300 nm), only when the probe wavelength was reduced to 1180 nm could the interference fringes be obtained under the same time delay of 500 fs, as shown in Figure 4d. The effective refractive index of the multilayer-graphene micro-sheet/ZnO nanoparticle layer and the monolayer graphene/polycrystalline ITO layer was decreased, resulting from the optical Kerr effect under the excitation of the pump laser.…”

“…11, 24 Biswas et al noted that the electric field distributions of different dipole plasmonic modes is different even though they may have similar current density distributions. 11 To investigate the slow-light effect brought about by MIT, we first calculated the linear transmission spectrum and group refractive index of the metasurfaces with different gap distances for the gold nanoprism dimer unit, which is shown in Figure 3a and 3b. The group refractive index was not directly obtained from the transmission spectrum (the detailed calculation methods are shown in the Supplementary Information).…”

“…The acquisition of the giant group index in an ultrathin metasurface may results from three aspects. First, the gold nanoprism has stronger localization due to its sharper corner compared to a cuboid; 10,11 second, the variety of modes existing in the gold nanoprism makes coupling between the two nanoprisms much easier; 32 third, if the plasmonic microstructure is compared with the ''optical microcavity'', it is easy to see that the quality factor value (Q / 1/Dv) increases with the decrease of the linewidth of the transparency window brought about by the increased gap distance, as shown in Figure 3b, i.e., the photon lifetime increase corresponds to the strengthened slow-light effect. 33,34 We also investigated the dependence of the MIT lineshapes on the structural parameters, including the period of the dimers, the lateral length of the nanoprisms, the thickness of the gold nanoprisms, and different incident polarizations (detailed in the Supplementary Information).…”

“…[1][2][3][4][5] Recently, the slow-light effect has been realized based on metamaterial-induced transparency (MIT). [6][7][8][9][10][11] However, only a small group index of 100 was obtained in photonic metamaterials because of the relatively large intrinsic loss of metal. [6][7][8][9][10][11] Moreover, various functional integrated photonic devices, including ultrafast all-optical buffers and all-optical switches, require ultrafast control of the slow-light effect.…”

“…[6][7][8][9][10][11] However, only a small group index of 100 was obtained in photonic metamaterials because of the relatively large intrinsic loss of metal. [6][7][8][9][10][11] Moreover, various functional integrated photonic devices, including ultrafast all-optical buffers and all-optical switches, require ultrafast control of the slow-light effect. Photonic metasurfaces offer a variety of opportunities to control light using flat and surface components and have attracted wide attention for their great practical applications in the field, such as optical computing, optical communications, and integrated photonic circuits.…”