研究目的
To generate and actively control chiral optical near fields using a simple system of an achiral gold nanorod and linearly polarized light, enabling switchable handedness without relying on chiral nanomaterials.
研究成果
The research successfully demonstrates active control of chiral optical near fields on a single gold nanorod by adjusting the incident polarization angle, achieving high degrees of circular polarization. This provides a foundation for developing nanoscale polarization modulators, enhancing chiral molecule detection, and advancing spintronic devices, with future work needed to refine models and explore broader applications.
研究不足
The dipole model is an oversimplification, leading to quantitative inconsistencies in distance parameters. The method cannot distinguish absolute azimuth angles beyond ±45 degrees due to instrumental limitations. The study is limited to gold nanorods and specific excitation conditions, and practical applications may require optimization for different materials or environments.
1：Experimental Design and Method Selection:
The study uses near-field polarimetry based on an aperture-type scanning near-field optical microscope to measure the polarization state of optical fields near a gold nanorod. A point dipole model is employed for theoretical simulations.
2：Sample Selection and Data Sources:
Gold nanorods with dimensions of 160 nm length, 40 nm width, and 55 nm thickness are fabricated on a glass substrate using electron-beam lithography and lift-off techniques.
3：List of Experimental Equipment and Materials:
Equipment includes a near-field aperture probe (aperture diameter ≈ 60 nm), objective lens (NA =
4：4), photoelastic modulator (PEM), linear polarizer, half-wave plate, quarter-wave plate, photomultiplier tube, and lock-in amplifier. Materials include gold and chromium for nanorod fabrication. Experimental Procedures and Operational Workflow:
Linearly polarized light (wavelength 850 nm) illuminates the nanorod through the probe, and the scattered field's polarization is analyzed in the far field using PEM modulation and lock-in detection. The azimuth angle of incident polarization is varied to control chirality.
5：Data Analysis Methods:
Data is analyzed using lock-in detection for demodulation, and theoretical fits are performed using equations derived from the point dipole model to estimate parameters like polarizability.
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