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Nonreciprocal optical links based on time-modulated nanoantenna arrays: Full-duplex communication
摘要： Interference of transmitted and received signals hinders the simultaneous functionality of a conventional optical antenna as a transmitter and receiver which is required for full-duplex communication. The full-duplex communication schemes enabled by dense wavelength division multiplexed optical networks require distinct transmitter/receiver components operating at different wavelengths which increase the cost, complexity, and footprint of the physical layer. In this work, we demonstrate that an array of nanoantennas with leaky-wave architecture based on spatiotemporal modulation establishes nonreciprocal optical links which can reject the interference of transmitted and received signals by isolating the frequency of transmission and reception modes. For this purpose, we integrate indium-tin oxide into plasmonic nanodipoles which allows for realization of time-modulated nanoantennas in near-infrared frequency regime through electrical modulation of charge carrier density with radio-frequency signals. The radiation characteristics of individual nanoantennas and modal properties of nanoantenna arrays are rigorously studied through linking of charge transport and electromagnetic models. To this end, we extend the formulation of discrete dipole approximation as the standard modeling tool for electromagnetic scattering from nanoantenna arrays to treat realistic time-modulated structures with drastically different timescales between optical and modulation frequencies. The operation of spatiotemporally modulated array antennas in transmission and reception modes is investigated. Moreover, electrical beam-scanning functionality and dependence of antenna characteristics to modulation parameters and wavelength are demonstrated. It is rigorously established that such array antennas can operate as full transceivers by separating the transmitted and received signals propagating along the same direction through down conversion and up conversion of the frequency. Our results provide a route toward realization of optical antenna systems capable of full-duplex communication and real-time beam scanning which can increase the capacity and decrease the complexity of optical networks.
关键词： nonreciprocal optical links,indium-tin oxide,leaky-wave antenna,discrete dipole approximation,full-duplex communication,time-modulated nanoantenna arrays,spatiotemporal modulation
更新于2025-09-23 15:23:52
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Exploiting Evanescent Field Polarization for Giant Chiroptical Modulation from Achiral Gold Half-Rings
摘要： For applications seeking to realize on-chip polarization discriminating nanoantennas, efficient energy conversion from surface waves to far-field radiation is desirable. However, the response of individual nanoantennas to the particular polarization states achievable in surface waves, such as evanescent fields, has not yet been thoroughly investigated. Here, we report giant modulation of visible light scattering from achiral gold half-rings when switching between evanescent surface wave excitation produced from total internal reflection of left-handed and right-handed circularly polarized light. The effect is driven by a differing relative phase between the in-plane transverse and longitudinal field oscillations of the evanescent wave depending on the incident light handedness. As longitudinal field oscillations are not found in free-space excitation, this presents a fundamentally different mechanism for chiroptical responses as traditional mechanisms for circular dichroism only account for purely transversal field oscillations. Although the half-ring scattering modulation is dependent on the wave vector orientation, an orientation invariant response is also realized in planar chiral nanoantennas composed of eight half-rings in a rotationally symmetric arrangement, with up to 50% scattering modulation observed at 725 nm. Though both structures are found to produce scattering modulation when switching the handedness of free-space light, the distinct polarization properties of evanescent fields are shown to be strictly required to observe giant scattering modulation. These results ultimately deepen our understanding of the range of possible chiroptical effects in light-matter interactions.
关键词： nanoantenna,extrinsic chirality,evanescent fields,planar chirality,polarization discrimination,longitudinal field oscillations
更新于2025-09-23 15:21:21
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Nanoplasmonics || Plasmonic Nanoantenna Array Design
摘要： Recently, wireless optical communication system is developing toward the chip level. Optical nanoantenna array in optical communication system is the key component for radiating and receiving light. In this chapter, we propose a sub-wavelength plasmonic nanoantenna with high gain operating at the standard optical communication wavelength of 1550 nm. The designed plasmonic antenna has a good matching with the silicon waveguide in a wide band, and light is fed from the bottom of the nanoantenna via the silicon waveguide. Furthermore, we design two kinds of antenna arrays with the proposed plasmonic nanoantenna, including one- and two-dimensional arrays (1 × 8 and 8 × 8). The radiation characteristics of the antenna arrays are investigated and both arrays have high gains and wide beam steering range without grating lobes.
关键词： localized surface plasmon,radiation characteristics,integrated photonic devices,plasmonic nanoantenna,integrated optical antenna arrays
更新于2025-09-23 15:21:01
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Boosting Perovskite Photodetector Performance in NIR Using Plasmonic Bowtie Nanoantenna Arrays
摘要： Triple-cation mixed metal halide perovskites are important optoelectronic materials due to their high photon to electron conversion efficiency, low exciton binding energy, and good thermal stability. However, the perovskites have low photon to electron conversion efficiency in near-infrared (NIR) due to their weak intrinsic absorption at longer wavelength, especially near the band edge and over the bandgap wavelength. A plasmonic functionalized perovskite photodetector (PD) is designed and fabricated in this study, in which the perovskite ((Cs0.06FA0.79MA0.15)Pb(I0.85Br0.15)3) active materials are spin-coated on the surface of Au bowtie nanoantenna (BNA) arrays substrate. Under 785 nm laser illumination, near the bandedge of perovskite, the fabricated BNA-based plasmonic PD exhibits ≈2962% enhancement in the photoresponse over the Si/SiO2-based normal PD. Moreover, the detectivity of the plasmonic PD has a value of 1.5 × 1012 with external quantum efficiency as high as 188.8%, more than 30 times over the normal PD. The strong boosting in the plasmonic PD performance is attributed to the enhanced electric field around BNA arrays through the coupling of localized surface plasmon resonance. The demonstrated BNA-perovskite design can also be used to enhance performance of other optoelectronic devices, and the concept can be extended to other spectral regions with different active materials.
关键词： near infrared,bowtie nanoantenna arrays,perovskite photodetectors,localized surface plasmon resonance
更新于2025-09-23 15:21:01
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Optical Trapping of Nanoparticles Using All-Silicon Nanoantennas
摘要： The ability to optically trap nanoscale particles in a reliable and noninvasive manner is emerging as an important capability for nanoscience. Different techniques have been introduced, including plasmonic nanostructures. Nano-optical tweezers based on plasmonics face the problem of Joule heating however due to high losses in metals. Here we experimentally demonstrate the optical trapping and transport of nanoparticles using a non-plasmonic approach, namely a silicon nanoantenna. We trap polystyrene nanoparticles with diameters of 20 and 100 nm, and use fluorescence microscopy to track their positions as a function of time. We show that multiple nanoparticles can be trapped simultaneously with a single nanoantenna. We show that the infrared trapping laser beam also produces fluorescent emission from trapped nanoparticles via two-photon excitation. We present simulations of the nanoantenna that predict enhanced optical forces with insignificant heat generation. Our work demonstrates that silicon nanoantennas enable nanoparticles to be optically trapped without deleterious thermal heating effects.
关键词： Optical trapping,silicon nanoantenna,thermal effect,optical force,nanoparticle
更新于2025-09-23 15:21:01
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Interferometric Evanescent Wave Excitation of a Nanoantenna for Ultrasensitive Displacement and Phase Metrology
摘要： We propose a method for ultrasensitive displacement and phase measurements based on a nanoantenna illuminated with interfering evanescent waves. We show that with a proper nanoantenna design, tiny displacements and relative phase variations can be converted into changes of the scattering direction in the Fourier space. These sensitive changes stem from the strong position dependence of the orientation of the purely imaginary Poynting vector produced in the interference pattern of evanescent waves. Using strongly confined evanescent standing waves, high sensitivity is demonstrated on the nanoantenna’s zero-scattering direction, which varies linearly with displacement over a wide range. With weakly confined evanescent wave interference, even higher sensitivity to tiny displacement or phase changes can be reached near a particular location. The high sensitivity of the proposed method can form the basis for many metrology applications. Furthermore, this concept demonstrates the importance of the imaginary part of the Poynting vector, a property that is related to reactive power and is often ignored in photonics.
关键词： nanoantenna,Poynting vector,evanescent waves,displacement metrology,phase metrology
更新于2025-09-23 15:21:01
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Steering second-harmonics
摘要： The phase control and shaping of the second-harmonic radiation generated from an AlGaAs nanodisk antenna has now been accomplished by a team of researchers from Italy, France and Australia. Lavinia Ghirardini and co-workers used electron-beam lithography to fabricate a pair of gratings located either side of a nonlinear nanoantenna. Phase engineering then made it possible to redirect and control the emission angle of second-harmonic light generated from the optically pumped structure. The precise angle of emission can be engineered by employing gratings with different symmetry, or by varying the polarization of the optical pump beam. The control of the emission direction is important because it means that two orders of magnitude more power can be collected out of the antenna plane and arbitrary emission angles could be useful for certain applications. Another key point is that the AlGaAs structures can exhibit lower losses than metallic nanoantennas, which aid efficiency. Such efficient shaping of the nonlinear beams may have applications to, for example, single-photon sources and nonlinear imaging.
关键词： phase control,AlGaAs,nanoantenna,second-harmonics,nonlinear imaging
更新于2025-09-23 15:21:01
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Application of Plasmonic Nanoantennas in Enhancing the Efficiency of Organic Solar Cells
摘要： It is known that the periodic use of silver nanoantennas in organic solar cells increases the e?ciency of light absorption. In this study, we performed a geometric parametric analysis of nanoantennas using the ?nite element method. Based on the study of the convex truncated cone nanoantenna, we have found that a nanoantenna arrangement formed by the convex truncated cone nanoantenna along with a pyramidal nanoantenna provides a better solution for di?erent angles of light incidence compared to a single nanoantenna. We obtained a mean increase in the absorption e?ciency of this organic solar cell, both for the TM and TE polarizations, compared to the use of the conventional nanoantenna in the wavelength range of 300–800 nm.
关键词： convex truncated cone nanoantenna,organic solar cells,finite element method,pyramidal nanoantenna,plasmonic nanoantennas,light absorption
更新于2025-09-23 15:19:57
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Terahertz Metalens for Multifocusing Bidirectional Arrangement in Different Dimensions
摘要： Metasurface lenses are typically investigated for a lot of characteristics, but the design method for conventional devices is comparatively simple in terms of controlling the quantity, position, and size of focal spots. Herein, ultra-thin-phase metasurface structures based on complementary square-split-ring (SSR) nanoantennas have been proposed to achieve terahertz (THz) optical metalenses with multidimensionality and multifocusing. The principle of beam propagation and efficient transmission can be effectively explained through the Fabry–Pérot resonance mode. The THz metalens can efficiently transfer linear cross-polarization under the effects of gratings in the incident plane. By locally tailoring edge lengths and opening the angles of the split rings, full control over abrupt phase changes can be achieved. Two symmetrically distributed parallel focal spots and two vertical focal spots with arbitrary distance can be obtained by arranging the SSR units on the metalenses. Furthermore, we apply the concept of a partitioned-phase mode to realize a double-focusing metalens in the longitudinal direction, which provides a flexible and convenient method to achieve the desired focusing properties. The simulation results are expected to pave the way for practical use of metasurfaces in optical holography, optical-information coding, and parallel-particle trapping.
关键词： nanoantenna,phase shift,Multifocusing metalens,Fabry-Pérot-like resonance,terahertz
更新于2025-09-19 17:15:36
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Duplicating Plasmonic Hotspots by Matched Nanoantenna Pairs for Remote Nanogap Enhanced Spectroscopy
摘要： Plasmonic nanoantennas are capable of reversibly interconverting free-space radiation with localized modes at the nanoscale. However, optical access to a single nanoantenna, through a laser beam, is always accompanied by disruptive background perturbations and heating effects. Remote spectroscopy is one promising route to overcome these effects. Here, we demonstrate excitation-collection-separated enhanced spectroscopy using a matched nanoantenna pair. The receiving and transmitting antennas are geometrically separated, but bridged by the propagating surface plasmon polaritons (SPPs) on the metal film. The receiving antenna, consisting of a silver nanowire on mirror, ensures a high light-to-plasmon conversion efficiency. The transmitting antenna consists of a silver nanocube over mirror and is impedance matched to free space photons and the propagating SPPs. As a proof-of-principle, we demonstrate remote surface-enhanced Raman scattering with a high signal-to-noise ratio. This matched nanoantenna pair may have applications for remote entanglement of quantum emitters, biochemistry detection, or optical interconnects.
关键词： surface plasmon polaritons,directional launching,remote spectroscopy,Nanoantenna,nanoparticle over mirror
更新于2025-09-19 17:13:59