Jian-Bo Li

Plasmon-mediated radiative energy transfer across a silver nanowire array via resonant transmission and subwavelength imaging.

Efficient plasmon-mediated excitation energy transfer between the CdSe/ZnS semiconductor quantum dots (QDs) across the silver nanowire array up to 560 nm in length is observed. The subwavelength imaging and spectral response of the silver nanowire arrays with near-field point-source excitations are revealed by theoretical simulations. Our studies demonstrate three advantages of the nanosystem: efficient exciton-plasmon conversion at the input side of the array through near-field strong coupling, directional waveguidance and resonant transmission via half-wave plasmon modes of the nanowire array, and subwavelength imaging at the output side of the array. These advantages allow a long-range radiative excitation energy transfer with a high efficiency and a good directionality.

Four-wave mixing signal enhancement and optical bistability of a hybrid metal nanoparticle-quantum dot molecule in a nanomechanical resonator

We investigate theoretically four-wave mixing (FWM) response and optical bistability (OB) in a hybrid nanosystem composed of a metal nanoparticle (MNP) and a semiconductor quantum dot (SQD) coupled to a nanomechanical resonator (NR). It is shown that the FWM signal is enhanced by more than three orders of magnitude as compared to that of the system without exciton-phonon interaction, and the FWM signal can also be suppressed significantly and broadened due to the exciton-plasmon interaction. As the MNP couples strongly with the SQD, the bistable FWM response can be achieved by adjusting the SQD-MNP distance and the pumping intensity. For a given pumping constant and a fixed SQD-MNP distance, the enhanced exciton-phonon interaction can promote the occurrence of bistability. Our findings not only present a feasible way to detect the spacing between two nanoparticles, but also hold promise for developing quantum switches and nanoscale rulers.

Transport properties of a single plasmon interacting with a hybrid exciton of a metal nanoparticle–semiconductor quantum dot system coupled to a plasmonic waveguide

The transport properties of a single plasmon interacting with a hybrid system composed of a semiconductor quantum dot (SQD) and a metal nanoparticle (MNP) coupled to a one-dimensional surface plasmonic waveguide are investigated theoretically via the real-space approach. We considered that the MNP-SQD interaction leads to the formation of a hybrid exciton and the transmission and reflection of a single incident plasmon could be controlled by adjusting the frequency of the classical control field applied to the MNP-SQD hybrid nanosystem, the kinds of MNPs and the background media. The transport properties of a single plasmon interacting with such a hybrid nanosystem discussed here could find applications in the design of next-generation quantum devices, such as single-photon switching and nanomirrors, and in quantum information processing.

Tunable Plasmon Resonance and Enhanced Photocatalytic Activity of Au–CdS Core–Shell Nanodogbones

Au–CdS core–shell nanodogbones with controllable shell thickness were facilely synthesized by one-pot method. Their tunable optical properties have been investigated with UV-Vis spectra and finite-difference time-domain method. With CdS shell thickness increasing, the red-shifted and enhanced surface plasmon resonance (SPR) peak is observed as expected, while a new transverse SPR (T-SPR) gradually appeared at the visible region and two T-SPR bands overlap with each other, which broaden absorption band of the corresponding components in the solar spectrum. In addition, Au–CdS NDBs exhibited excellent photocatalytic performance in the photodegradation tests of rhodamine B, and their photocatalytic activities enhanced with CdS shell thicknesses increasing. We believe that the finding will have great potential applications in the solar energy fields.

Coherent Controllable Transport of a Surface Plasmon Coupled to a Plasmonic Waveguide with a Metal Nanoparticle-Semiconductor Quantum Dot Hybrid System

By using the real-space method, the switching of a single plasmon interacting with a hybrid nanosystem composed of a semiconductor quantum dot (SQD) and a metallic nanoparticle (MNP) coupled to a 1D surface plasmonic waveguide is investigated theoretically. We discussed that the dipole coupling between an exciton and a localized surface plasmon results in the formation of a hybrid exciton and the transmission and reflection of the propagating single plasmon could be controlled by changing the interparticle distance between the SQD and the MNP and the size of the nanoparticles. The controllable transport of the propagating single surface plasmon by such a nanosystem discussed here could find significant potential in the design of next-generation quantum devices such as plasmonic switches, single photon transistors, and nanolasers, and quantum information.

Study on temperature sensitivity of topological insulators based on long-period fiber grating

Abstract. Based on a long-period fiber grating, we conducted experimental research on the temperature sensitivity of topological insulators. The long-period fiber grating and topological insulators solution were encapsulated in a capillary tube using UV glue, and the temperature response was measured. Within a range of 35 to 75 centigrade, one resonance dip of a long-period fiber grating exhibits a redshift of 1.536 nm. The temperature sensitivity is about 7.7 times of an ordinary long-period fiber grating’s sensitivity (0.005  nm/°C). A numerical simulation is also performed on the basis of the experiments.

Plasmon resonances in a periodic square coaxial hole array in a graphene sheet

We present a computational study of the plasmon resonances in a periodic square coaxial hole array in a graphene sheet, which consists of a square hole array and a square strip array. According to charge oscillation picture, we find that a new plasmon mode, which locates on the edges of square hole along the polarization direction of incident light, emerges in our proposed structure. Two hybridized plasmon resonance modes (i.e., symmetric and asymmetric plasmon resonance modes) are formed due to two different manners of coupling between the new plasmon mode of square hole and the plasmon mode of square strip. The two plasmon resonance modes can be tuned over a wide wavelength range by a small change in the chemical potential of graphene. Furthermore, the two plasmon resonances can also be controlled by changing Lx and Ly (which are the strip offsets from the hole center perpendicular and parallel to the polarization direction of incident light, respectively), originating from the change in the strength of electromagnetic coupling between square hole and square strip. Our study gives an insight into the physical mechanism of plasmon resonances in square graphene coaxial hole array, and our findings will be useful for designing graphene-based plasmonic devices and metamaterials.

Plasmonic Effect on the Optical Properties in a Hybrid V-Type Three-Level Quantum Dot-Metallic Nanoparticle Nanosystem

We investigated theoretically the exciton–plasmon coupling effects on the population dynamics and the absorption properties of a hybrid nanosystem composed of a metal nanoparticle (MNP) and a V-type three-level semiconductor quantum dot (SQD), which are created by the interaction with the induced dipole moments in the SQD and the MNP, respectively. Excitons of the SQD and the plasmons of the MNP in such a hybrid nanosystem could be coupled strongly or weakly to demonstrate novel properties of the hybrid system. We also find that the gain happens in such a hybrid system, because of the coherent interaction between the SQD and the MNP. Our results show that the non-linear optical response of the hybrid nanosystem can be greatly enhanced or depressed due to the exciton–plasmon couplings.

Interparticle Coupling Effects of Two Quantum Dots System on the Transport Properties of a Single Plasmon

Transport properties of a single plasmon interacting with two quantum dots (QDs) system coupled to one-dimensional surface plasmonic waveguide are investigated theoretically via the real-space approach. We mainly focus on the coupling effects of the two QDs on the transmission properties of a single incident plasmon. We demonstrated that switching of a single plasmon can be achieved by controlling the interparticle distance, the interparticle coupling strength, and the QD-waveguide coupling strength, as well as spectral detuning. We also showed that the coupling between the continuum excitations and the discrete excitations results in the Fano-type transmission spectrum. The transport properties of a single plasmon interacting with such a two direct coupled QDs system could find the applications in the design of plasmonic nanodevices, such as single photon switching and nanomirrors, and in quantum information processing.

Optimized field confinement and plasmon-induced SERS activity of Janus-like Au–AgAuS hybrid nanoboats

Janus-like Au–AgAuS hybrid nanoboats (NBs) with controllable half shells were prepared by using seed-mediated growth method. Their tunable plasmon properties were investigated by using UV-Vis spectra and finite-difference time-domain (FDTD) method. With the shell thicknesses increasing, the red shifting of surface plasmon resonance (SPR) peaks and an obvious enhancement of transverse SPR band have been observed for the Janus-like NBs. The effects of shell thicknesses and covered areas on local electric field of Janus-like Au–AgAuS NBs were further studied by FDTD simulation, which proposed an effective method to manipulate the electromagnetic field distributions of metal plasmonic nanostructures. In addition, served as solution-based active SERS substrates, the SERS performances of Au NRs and Janus-like Au–AgAuS NBs with different shell thicknesses have been further estimated by using rhodamine B as probe molecules. Compared with the others, Au–AgAuS NBs with about 2.82-nm shell displayed the best SERS performance with good reproducibility in our experiments, owing to the effective plasmonic enhancement and load capability.