研究目的
To investigate the electromagnetic coupling and hybridization of plasmonic and Mie-resonant modes in hybrid metal-dielectric nanodimers, and to demonstrate reshaping of second-harmonic generation polarization dependence and signal enhancement.
研究成果
The hybridization of plasmonic and Mie-resonant modes in hybrid metal-dielectric nanodimers leads to significant reshaping of second-harmonic generation polarization dependence and up to two orders of magnitude signal enhancement compared to isolated dielectric nanoparticles. This enables tunable nonlinear sources and potential applications in near-field control, sensing, and light manipulation.
研究不足
Uncertainties in nanoparticle sizes and distances measured by electron microscopy affect peak positions in scattering spectra. The spherical shape approximation may not fully capture real nanoparticle geometries. The pick-and-place technique limits control over crystalline orientation of BTO nanoparticles, influencing SHG signals. Enhancements are wavelength-dependent and may vary with specific dimer configurations.
1：Experimental Design and Method Selection:
The study uses a bottom-up assembly approach with pick-and-place technique under a scanning electron microscope to fabricate hybrid nanodimers of gold and barium titanate nanoparticles. Linear scattering spectroscopy and nonlinear second-harmonic generation (SHG) spectroscopy with polarimetry are employed to probe hybridized modes. Theoretical modeling is done using Mie theory and finite-element-method simulations in COMSOL Multiphysics.
2：Sample Selection and Data Sources:
Samples include single gold nanoparticles (diameters around 200-210 nm), single barium titanate (BTO) nanoparticles (diameters around 240-330 nm), and hybrid nanodimers composed of one gold and one BTO nanoparticle (e.g., D1: 213 nm Au / 314 nm BTO, D2: 200 nm Au / 298 nm BTO, D3: 200 nm Au / 330 nm BTO). Data is collected from fabricated samples on indium tin oxide (ITO) covered glass substrates.
3：List of Experimental Equipment and Materials:
Equipment includes a scanning electron microscope for fabrication and imaging, a home-built dark-field spectroscopy setup for linear scattering measurements, a home-built transmission optical setup for SHG measurements with a Ti:Sapphire laser (800-1080 nm) and an optical parametric oscillator (OPO, 1040-1400 nm), Glan-Taylor polarizer, half-wave plates, lenses, objectives, scientific CMOS camera, bandpass/short-pass filters, and an imaging spectrometer. Materials include gold nanoparticles, barium titanate nanoparticles, ITO-covered glass substrates, and a sharp metallic tip for manipulation.
4：Experimental Procedures and Operational Workflow:
Fabrication involves electrostatic manipulation of nanoparticles under an electron microscope to assemble dimers. Linear scattering is measured in dark-field mode with halogen lamp illumination, collecting forward and backward scattering. SHG measurements involve exciting samples with tunable laser light, controlling polarization with polarizers and waveplates, collecting SHG signal with an objective and camera, and filtering out pump light. Polarization dependencies are recorded by rotating the excitation polarization.
5：Data Analysis Methods:
Data is normalized by experimental parameters (e.g., laser power, integration time, transmission of optics). Numerical simulations use COMSOL Multiphysics for scattering cross-sections and SHG responses, accounting for material dispersion and collection numerical aperture. Multipole decomposition is performed using Mie theory.
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