Unlike silver and gold, aluminum has material properties that enable strong plasmon resonances spanning much of the visible region of the spectrum and into the ultraviolet. This extended response, combined with its natural abundance, low cost, and amenability to manufacturing processes, makes aluminum a highly promising material for commercial applications. Fabricating Al-based nanostructures whose optical properties correspond with theoretical predictions, however, can be a challenge. In this work, the Al plasmon resonance is observed to be remarkably sensitive to the presence of oxide within the metal. For Al nanodisks, we observe that the energy of the plasmon resonance is determined by, and serves as an optical reporter of, the percentage of oxide present within the Al. This understanding paves the way toward the use of aluminum as a low-cost plasmonic material with properties and potential applications similar to those of the coinage metals.

/pdf/aluminum-for-plasmonics-oy8t9f6wgd.pdf

Aluminum for Plasmonics

Even though the mesoporous-type perovskite solar cell (PSC) is known for high efficiency, its planar-type counterpart exhibits lower efficiency and hysteretic response. Herein, we report success in suppressing hysteresis and record efficiency for planar-type devices using EDTA-complexed tin oxide (SnO2) electron-transport layer. The Fermi level of EDTA-complexed SnO2 is better matched with the conduction band of perovskite, leading to high open-circuit voltage. Its electron mobility is about three times larger than that of the SnO2. The record power conversion efficiency of planar-type PSCs with EDTA-complexed SnO2 increases to 21.60% (certified at 21.52% by Newport) with negligible hysteresis. Meanwhile, the low-temperature processed EDTA-complexed SnO2 enables 18.28% efficiency for a flexible device. Moreover, the unsealed PSCs with EDTA-complexed SnO2 degrade only by 8% exposed in an ambient atmosphere after 2880 h, and only by 14% after 120 h under irradiation at 100 mW cm−2. The development of high efficiency planar-type perovskite solar cell has been lagging behind the mesoporous-type counterpart. Here Yang et al. modify the oxide based electron transporting layer with organic acid and obtain planar-type cells with high certified efficiency of 21.5% and decent stability.

/pdf/high-efficiency-planar-type-perovskite-solar-cells-with-473dsp8iad.pdf

High efficiency planar-type perovskite solar cells with negligible hysteresis using EDTA-complexed SnO2

Modern electronics based on semiconductors is meeting the fundamental speed limit caused by the interconnect delay and large heat generation when the sizes of components reach nanometer scale. Photons as a carrier of the information are superior to electrons in bandwidth, density, speed, and dissipation. More over, photons could carry intensity, polarization, phase, and frequency information which could break through the limitation of binary system as in electronic devices. But due to the diffraction limitation, the photonic components and devices can not be fabricated small enough to be integrated densely. Surface plasmon polariton is quanta of collective oscillations of free electrons excited by photons in metal nanostrucrures, which offers a promising way to manipulate light at the nanoscale and to realize the miniaturization of photonic devices. Hence, plasmonic circuits and devices have been proposed for some time as a potential strategy for advancing semiconductor-based computing beyond the fundamental performance limitations of electronic devices, as epitomized by Moore's law. A variety of individual plasmonic nanodevices have been intensively studied recently, but the crucial and necessary step to enable nanophotonic circuits for future information technology, namely cascade logics integrated on-chip, has not been achieved. Here we demonstrate that a nanophotonic binary logic NOR gate can be realized by cascading plasmonic OR and NOT gates in four-terminal nanowire networks. We explain the operating principle for the device based on quantum dot luminescence imaging, which reveal the interferences for different logic functions between propagating plasmon wave packets in the nanowire network in great detail. Since the NOR gate is logic complete, i.e. any Boolean logic gate can be constructed from it, our results could have a key role in defining a viable path for the development of novel subwavelength optical processor architectures.

Cascaded Logic Gates in Nanophotonic Plasmon Networks

As stated in the text, Figs. 3 and 4 (transmission versus probe laser detuning) were taken at an energy of 10 nJ in a 0.5-mm-diam beam. We should have noted that when the probe energy is increased to 150 n3 (— 10" W/cm ) the absorption cross section at the transmission maximum increases by a factor of approximately 2. At this energy density, with or without the coupling laser present, transmitted probe energy is no longer linear with incident probe energy.

Observation of Electromagnetically Induced Transparency in Collisionally Broadened Lead Vapor

Tunable localized surface plasmon graphene metasurface for multiband superabsorption and terahertz sensing

A perfect ultra-narrow band infrared metamaterial absorber based on the all-metal-grating structure is proposed. The absorber presents a perfect absorption efficiency of over 98% with an ultra-narrow bandwidth of 0.66 nm at normal incidence. This high efficient absorption is contributed to the surface plasmon resonance. Moreover, the surface plasmon resonance-induced strong surface electric field enhancement is favorable for application in biosensing system. When operated as a plasmonic refractive index sensor, the ultra-narrow band absorber has a wavelength sensitivity 2400 nm/RIU and an ultra-high figure of merit 3640, which are much better than those of most reported similar plasmonic sensors. Besides, we also comprehensively investigate the influences of structural parameters on the sensing properties. Due to the simplicity of its geometry structure and its easiness to be fabricated, the proposed high figure of merit and sensitivity sensor indicates a competitive candidate for applications in sensing or detecting fields.

/pdf/infrared-plasmonic-refractive-index-sensor-with-ultra-high-yzce5yg79w.pdf

Infrared Plasmonic Refractive Index Sensor with Ultra-High Figure of Merit Based on the Optimized All-Metal Grating.

In this paper, three Fano resonances based on three different physical mechanisms are theoretically and numerically investigated in a plasmonic resonator system, comprised of two circular cavities. And the multimode interference coupled mode theory (MICMT) including coupling phases is proposed to explain the Fano resonances in plasmonic resonator system. According to MICMT, one of the Fano resonances originates from the interference between different resonant modes of one resonator, the other is induced by the interference between the resonant modes of different resonators. Mode degeneracy is removed when the symmetry of the system is broken, thereby emerging the third kind of Fano resonance which is called degenerate interference Fano resonance, and the degenerate interference coupled mode theory (DICMT) is proposed to explain this kind of Fano resonance. The sensitivity and FOM* (figure of merit) of these Fano resonances can be as high as 840 nm/RIU and 100, respectively. These are useful for fundamental study and applications in sensors, splitters and slow-light devices.

Fano resonances based on multimode and degenerate mode interference in plasmonic resonator system.

Multiple Fano resonances are numerically investigated based on different waveguide modes in a nanoscale plasmonic waveguide resonator system, which consists of two grooves coupled with a metal–insulator–metal (MIM) waveguide. Simulation results show that by introducing a small structural breaking in the plasmonic resonator, both symmetric and antisymmetric waveguide modes can be excited. Due to the interaction of the symmetric and antisymmetric waveguide modes, the transmission spectra possess a sharp asymmetrical profile. Because of different origins, these Fano resonances exhibit different dependence on the parameters of the structure and can be easily tuned. These characteristics offer flexibility to design the device. This nanosensor yields a sensitivity of $\sim$ 820 nm/RIU and a figure-of-merit of $\sim\! 3.2\times 10^{5}$ . The utilization of the antisymmetric mode in the MIM waveguide provides a new possibility for designing high-performance plasmonic devices.

Multiple Fano Resonances Based on Different Waveguide Modes in a Symmetry Breaking Plasmonic System

A novel and compact refractive index sensor based on Fano resonance in the plasmonic waveguide system, which comprises with a stub and groove resonator coupled with a metal–insulator–metal waveguide, is proposed and investigated by the finite-element method. Due to the interaction of the narrow discrete resonance and a broad spectrum caused by the stub resonator and the groove, respectively, the transmission spectrum exhibits a sharp asymmetrical profile. Simulation results show that the Fano resonance can be easily tuned by changing the parameters of the structure. These characteristics offer flexibility to design the devices. This nanosensor yields a sensitivity of $\sim 1260$ nm/RIU and a figure of merit of $\sim 2.3\,\times \, 10^{\mathrm {\mathbf {4}}}$ . This letter is significant for design and application of the sensitive nanoscale refractive index sensor.

A Refractive Index Nanosensor Based on Fano Resonance in the Plasmonic Waveguide System

A sharp and asymmetric line shape is numerically predicted in a novel and compact plasmonic waveguide system This system consists of a groove and a ring resonator coupled with a metal–insulator–metal waveguide Due to the interaction of the narrow discrete resonance and a broad spectrum caused by the ring resonator and the groove, respectively, the transmission spectrum exhibits a sharp asymmetrical profile Simulation results show that the spectral line shape can be easily tuned by changing the parameters of the structure The physical features contribute to a highly efficient plasmonic nanosensor for refractive index sensing with the sensitivity of 1160 nm/RIU and a figure of merit of 3200 This plasmonic structure with such high figure of merits may find important applications in the on-chip nanosensors

Li Yu

Papers

Infrared Plasmonic Refractive Index Sensor with Ultra-High Figure of Merit Based on the Optimized All-Metal Grating.

Fano resonances based on multimode and degenerate mode interference in plasmonic resonator system.

Multiple Fano Resonances Based on Different Waveguide Modes in a Symmetry Breaking Plasmonic System

A Refractive Index Nanosensor Based on Fano Resonance in the Plasmonic Waveguide System

Sharp Asymmetric Line Shapes in a Plasmonic Waveguide System and its Application in Nanosensor