Optical computing has been pursued for decades as a potential strategy for advancing beyond the fundamental performance limitations of semiconductor-based electronic devices, but feasible on-chip integrated logic units and cascade devices have not been reported. Here we demonstrate that a plasmonic binary NOR gate, a 'universal logic gate', can be realized through cascaded OR and NOT gates in four-terminal plasmonic nanowire networks. This finding provides a path for the development of novel nanophotonic on-chip processor architectures for future optical computing technologies.

We show that the local electric field distribution of propagating plasmons along silver nanowires can be imaged by coating the nanowires with a layer of quantum dots, held off the surface of the nanowire by a nanoscale dielectric spacer layer. In simple networks of silver nanowires with two optical inputs, control of the optical polarization and phase of the input fields directs the guided waves to a specific nanowire output. The QD-luminescent images of these structures reveal that a complete family of phase-dependent, interferometric logic functions can be performed on these simple networks. These results show the potential for plasmonic waveguides to support compact interferometric logic operations.

We design, fabricate, and experimentally demonstrate an ultrathin, broadband half-wave plate in the near-infrared range using a plasmonic metasurface. The simulated results show that the linear polarization conversion efficiency is over 97% with over 90% reflectance across an 800 nm bandwidth. Moreover, simulated and experimental results indicate that such broadband and high-efficiency performance is also sustained over a wide range of incident angles. To further obtain a background-free half-wave plate, we arrange such a plate as a periodic array of integrated supercells made of several plasmonic antennas with high linear polarization conversion efficiency, consequently achieving a reflection-phase gradient for the cross-polarized beam. In this design, the anomalous (cross-polarized) and the normal (copolarized) reflected beams become spatially separated, hence enabling highly efficient and robust, background-free polarization conversion along with broadband operation. Our results provide strategies for creating compact, integrated, and high-performance plasmonic circuits and devices.

Control of light transmission and reflection through nanostructured materials has led to demonstration of metamaterial absorbers that have augmented the performance of energy harvesting applications of several optoelectronic and nanophotonic systems. Here, for the first time, a broadband plasmonic metamaterial absorber is fabricated using two-dimensional titanium carbide (Ti 3 C 2 T x ) MXene. Arrays of nanodisks made of Ti 3 C 2 T x exhibit strong localized surface plasmon resonances at near-infrared frequencies. By exploiting the scattering enhancement at the resonances and the optical losses inherent to Ti 3 C 2 T x MXene, high-efficiency absorption (∼90%) for a wide wavelength window of incident illumination (∼1.55 μm) has been achieved.

absorption. Although photocatalysis is already used in small-scale abatement of both indoor and outdoor pollution, the low efficiency (5%-10%) of solar-to-chemical energy conversion limits further breakthroughs in strategic applications such as hydrogen production and photovoltaics (PVs). [1,2] The engineering of composite interfaces for optimized operation is a key step to increase the solar absorption, electron-hole separation, and collection, and finally to provide high reaction yield. [3,4] The use of plasmonic nanostructures in energy conversion applications has been recently demonstrated with the enhanced performance of solar-to-fuels and solar-to-electricity devices. [5][6][7][8][9][10][11] Surface plasmons concentrate light into nanoscale volumes at the interface of a dielectric or a semiconductor providing intense electromagnetic field localization and improved scattering. The possibility to harness hot electrons generated from the surface plasmon decay [12,13] has shown to be a promising route toward selective nanocatalysis, [14][15][16][17][18][19][20] full-spectrum solar water splitting, [21][22][23] and ultrafast photodetection. [24][25][26][27] The nonradiative decay of surface plasmons, occurring in the 40-150 fs timescale, [12] produces a population of highly energetic (hot) electrons that are stabilized through injection into the semiconductor conduction band across a Schottky barrier. [28] Plasmonic nanoparticles (NPs) enable the efficient conversion of solar light into electrons with an energy well below the band gap of the semiconductor but limited to energies higher than the potential barrier (φ B ). As of yet, these demonstrations have been limited to NPs made of plasmonic noble metals such as Ag and Au. Despite their good optical performance, several challenges remain for noble metal NPs including high cost, poor chemical (Ag) and thermal stability (Au, Ag), diffusion into surrounding structures, and CMOS incompatibility, which hinders the practical implementation of conventional plasmonic structures.Aluminum nanocrystals are alternative plasmonic photocatalysts that provide efficient hot electron generation at low cost (i.e., high abundance of Al on the earth crust). [29][30][31][32][33][34] Nevertheless, issues for large-scale applications are related to Al NPs preparation, due to explosive reactivity of Al molecular The use of hot electrons generated from the decay of surface plasmons is a novel concept that promises to increase the conversion yield in solar energy technologies. Titanium nitride (TiN) is an emerging plasmonic material that offers compatibility with complementary metal-oxide-semiconductor (CMOS) technology, corrosion resistance, as well as mechanical strength and durability, thus outperforming noble metals in terms of cost, mechanical, chemical, and thermal stability. Here, it is shown that plasmonic TiN can inject into TiO 2 twice as many hot electrons as Au nanoparticles. TiO 2 nanowires decorated with TiN nanoparticles show higher photocurrent enhancement than decorat...

Metal nanowires supporting propagating surface plasmons (SPs) can be used as nanowaveguides and nanoantennas for light manipulation beyond the diffraction limit. Here the control of the propagation and radiation of SPs on silver nanowires is investigated. By covering an Al 2 O 3 layer onto a silver nanowire to change the local dielectric environment, the wave vector of the propagating SPs is increased. Thus, the radiation direction of SPs into the substrate is changed according to the phase matching condition, which is experimentally shown by Fourier imaging method. The radiation angle is sensitively dependent on the Al 2 O 3 thickness. By depositing 1 nm Al 2 O 3 , the increase of the radiation angle can be close to 1 degree. These results show that dielectric-layer-coating provides a simple and effective method to control the propagation and radiation of SPs, which will be of great importance for designing plasmonic circuits, antennas and sensors based on silver nanowires.

Plasmonics has brought revolutionary advances to laser science by enabling deeply subwavelength nanolasers through surface plasmon amplification. However, the impact of plasmonics on other promising laser systems has so far remained elusive. Here, we present a class of random lasers enabled by three-dimensional plasmonic nanorod metamaterials. While dense metallic nanostructures are usually detrimental to laser performance due to absorption losses, here the lasing threshold keeps decreasing as the volume fraction of metal is increased up to ∼0.07. This is ∼460 times higher than the optimal volume fraction reported thus far. The laser supports spatially confined lasing modes and allows for efficient modulation of spectral profiles by simply tuning the polarization of the pump light. Full-field speckle-free imaging at micron-scales has been achieved by using plasmonic random lasers as the illumination sources. Our findings show that plasmonic metamaterials hold potential to enable intriguing coherent optical sources.

Nanoplasmonic devices are promising for next generation information and communication technologies because of their capability to confine light at subwavelength scale and transport signals with ultrahigh speeds. However, ohmic losses are inherent to all plasmonic devices so that further development of integrated plasmonics requires efficient in situ loss compensation of signals with a wavelength and polarization of choice. Here we show that CdSe nanobelt/Al2O3/Ag hybrid plasmonic waveguides allow for efficient broadband loss compensation of propagating hybrid plasmonic signals of different polarizations using an optical pump and probe technique. With an internal gain coefficient of 6755 cm−1 at ambient condition, almost 100% of the propagation loss of TM-dominant plasmonic signals is compensated. From comparison with a similar photonic structure we attribute the fast-increasing gain at low pump intensity in hybrid plasmonic waveguides to the transfer across the metal-oxide-semiconductor interface of ‘hot' electrons photogenerated by the pump light.