Optical anapole modes in hybrid metal–dielectric nanoantenna for near-field enhancement and optical sensing

Metal–dielectric nanostructures in the optical anapole modes are essential for light–matter interactions due to the low material loss and high near-field enhancement. Herein, a hybrid metal–dielectric nanoantenna composed of six wedgeshaped gold(Au) nanoblocks as well as silica(SiO2) and silicon(Si) nanodiscs is designed and analyzed by the finite element method(FEM). The nanoantenna exhibits flexibility in excitation and manipulation of the anapole mode through the strong coupling between the metal and dielectrics, consequently improving the near-field enhancement at the gap. By systematically optimizing the structural parameters, the electric field enhancement factors at wavelengths corresponding to the anapole modes(AM1 and AM2) can be increased to 518 and 1482, respectively. Moreover, the nanoantenna delivers great performance in optical sensing such as a sensitivity of 550 nm/RIU. The results provide guidance and insights into enhancing the coupling between metals and dielectrics for applications such as surface-enhanced Raman scattering and optical sensing.

Overview of refractive index sensors comprising photonic crystal fibers based on the surface plasmon resonance effect[Invited]

Optical fibers have been widely applied to telecommunication,imaging,lasers,and sensing.Among the different types of fibers,photonic crystal fibers(PCFs),also called microstructured optical fibers,characterized by air holes arranged along the length of fibers have experienced tremendous advance due to their unique advantages.They are regarded as a desirable platform to excite surface plasmon resonance(SPR)because of easy realization of phase matching conditions between the fundamental core mode and the plasmonic mode,which plays a critical role in miniaturization and integration of SPR sensors.In this mini-review,the current status of PCF sensors based on SPR is summarized.The theory of SPR is discussed,and simulation methods for PCF-SPR sensors are described.The important parameters including the refractive index detection range,resonance wavelength,and spectral sensitivity responsible for the sensing properties of PCF-SPR sensors are reviewed.The fabrication and the comparison of performances are also illustrated,and,finally,the challenges and future perspectives are outlined.

Revenue-maximizing online stable task assignment on taxi-dispatching platforms

1 Introduction and contributions With the rapid development of mobile Internet,taxi-dispatching platforms have become increasingly popular and important.For example,UBer and Didi are both famous O2O platforms covering the dominating portion of the taxidispatching market over the world.A central issue in taxidispatching platforms is task assignment.