Mode evolution and nanofocusing of grating-coupled surface plasmon polaritons on metallic tip

We present a detailed analysis on mode evolution of gratingcoupled surface plasmonic polaritons （SPPs） on a conical metal tip based on the guidedwave theory. The eigenvalue equations for SPPs modes are discussed, revealing that cylindrical metal waveguides only support TM01 and HEm1 surface modes. During propagation on the metal tip, the gratingcoupled SPPs are converted to HE31, HE21, HE11 and TM01 successively, and these modes are sequentially cut off except TM01. The TM01 mode further propagates with drastically increasing effective mode index and is converted to localized surface plasmons （LSPs） at the tip apex, which is responsible for plasmonic nanofocusing. The gapmode plasmons can be excited with the focusing TM01 mode by approaching a metal substrate to the tip apex, resulting in further enhanced electric field and reduced size of the plasmonic focus.

The hard X-ray nanoprobe beamline at the SSRF

The hard X-ray nanoprobe beamline BL13U is a phase-Ⅱ beamline project at the Shanghai Synchrotron Radiation Facility.The beamline aims to enable comprehensive experiments at high spatial resolutions ranging from 50 to 10 nm. The X-ray energy range of the beamline, 5–25 keV, can detect most elements in the periodic table. Two operating modes were designed to accommodate the experimental requirements of high-energy resolution or high photon flux, respectively. X-ray nanofluorescence, nanodiffraction, and coherent diffraction imaging are developed as the main experimental techniques for BL13U. This paper describes the beamline optics, end station configurations, experimental methods under development, and preliminary test results. This comprehensive overview aims to provide a clear understanding of the beamline capabilities and potential applications.

Electronic manipulation of near-field nanofocusing in few-layer graphene-based hybrid nanotips

In this Letter, we propose the electronic manipulation of localized surface plasmon resonance for active tuning in near-field nanofocusing.We theoretically studied the excited graphene tuning of the nanofocusing field in fewlayer graphene(FLG)-based hybrid nanotips.It is revealed that the normalized enhanced electric field can be significantly promoted to more than 300 times.It is also observed that resonant peaks can be unprecedently modified by the electron state of excited graphene that is embedded in the substrate.It shows the possibility of flexible tuning of plasmon resonances via controlling the electron excitation state of graphene for specific advanced near-field nanofocusing applications.

Hard X-ray focusing resolution and efficiency test with a thickness correction multilayer Laue lens

The multilayer Laue lens(MLL) is a diffractive focusing optical element which can focus hard X-rays down to the nanometer scale. In this study, a WSi_(2)/Si multilayer structure consisting of 1736 layers, with a 7.2-nm-thick outermost layer and a total thickness of 17 μm, is prepared by DC magnetron sputtering. Regarding the thin film growth rate calibration, we correct the long-term growth rate drift from 2 to 0.6%, as measured by the grazing incidence X-ray reflectivity(GIXRR). A one-dimensional line focusing resolution of 64 nm was achieved,while the diffraction efficiency was 38% of the-1 order of the MLL Shanghai Synchrotron Radiation Facility(SSRF) with the BL15U beamline.

辉门动力总成携手NanoFocus AG研发创新型非接触式活塞环测量系统

辉门动力总成携手NanoFocus AG研发一种用于测量活塞环粗糙度和微观结构的非接触式光学共聚焦自动测量系统。该系统结合NanoFocus光学测量系统、软件及辉门活塞环产品数据库,能够帮助公司在位于德国布尔沙伊德的工厂生产活塞环时,加强生产控制与质量保证。

A flat-based plasmonic fiber probe for nanoimaging

The difficulty of obtaining high-intensity localized light spots for optical probes leads to their lack of good applications in nanoimaging.Here we demonstrate a Fabry–Pérot resonance flat-based plasmonic fiber probe(FPFP).The simulation results show that the probe can obtain a nanofocusing spot at the tip with the radially polarized mode.The Fabry–Pérot interference structure is used to control the plasmon propagation on the surface of the probe,it effectively improves the local spot intensity at the tip.Furthermore,the experimental results verify that the FPFP(tip curvature radius is 20 nm)prepared by chemical etching method can obtain a nanofocusing spot at the tip.The nanoimaging of the gold slit structure demonstrates the nanoimaging capability of the FPFP,the 36.9 nm slit width is clearly identified by the FPFP.

Recent advances in tip-enhanced Raman spectroscopy probe designs

Tip-enhanced Raman spectroscopy(TERS)imaging is a super-resolution imaging technique that features the merits of both surface-enhanced Raman spectroscopy(SERS)and scanning probe microscopy(SPM),such as the high chemical sensitivity from the former and the nanoscale spatial resolution from the latter.These advantages make TERS an essential nanospectroscopic characterization technique for chemical analysis,materials science,bio-sensing,etc.TERS probes,the most critical factor determining the TERS imaging quality,are expected to provide a highly confined electromagnetic hotspot with a minimized scattering background for the generation of Raman signals with high spatial resolution.After two decades of development,numerous probe design concepts have been proposed and demonstrated.This review provides a comprehensive overview of the state-of-the-art TERS probe designs,from the working mechanism to the practical performance.We start with reviewing the recent development of TERS configurations and the corresponding working mechanisms,including the SPM platforms,optical excitation/collection techniques,and probe preparation methods.We then review the emerging novel TERS probe designs,including the remote-excitation probes,the waveguide-based nanofocusing probes,the metal-coated nanofocusing probes,the nanowire-assisted selective-coupling probes,and the tapered metal-insulator-metal probes.Our discussion focuses on a few critical aspects,including the surface-plasmon-polariton(SPP)hotspot excitation technique,conversion efficiency,working frequency,and controllability.In the end,we review the latest TERS applications and give a perspective on the future of TERS.