研究目的
To investigate the nanoscale local properties of an arm-terminated log-spiral antenna for near-field coupling with infrared detectors, focusing on amplitude and phase distributions under different IR polarizations.
研究成果
The arm-terminated log-spiral antenna exhibits rotationally symmetric electric field distributions and a π phase reversal between probes for all polarization directions, indicating efficient near-field coupling potential with nanoscale IR detectors. s-SNOM with QCL provides high-quality data for such investigations, supporting future enhancements in detector performance.
研究不足
The study is limited to a specific antenna design (log-spiral with arm termination) and a single IR wavelength (7.73 μm). The experimental setup may have constraints in terms of resolution and signal-to-noise ratio, and the findings might not generalize to other antenna types or wavelengths without further investigation.
1：Experimental Design and Method Selection:
The study used a scattering-type near-field optical microscope (s-SNOM) combined with a quantum cascade laser (QCL) for high-resolution imaging. The method involved tapping-mode atomic force microscopy (AFM) with Si tips coated with platinum, and a pseudoheterodyne technique for phase measurements.
2：Sample Selection and Data Sources:
The sample was a fabricated log-spiral antenna with an arm termination, made of a 100 nm-thick Au film on a Si substrate, with an outer diameter of 20 μm.
3：List of Experimental Equipment and Materials:
Equipment included an s-SNOM system, AFM cantilever with Si tips coated with platinum, QCL at
4：73 μm wavelength, parabolic mirror, Michelson interferometer, quarter-wave plate, polarizer, and mid-IR detector. Materials included Au film and Si substrate. Experimental Procedures and Operational Workflow:
The antenna was illuminated with vertically polarized mid-IR light at a 30° angle. The tip oscillated at 250 kHz, and signals were measured at second-order harmonics. The sample was rotated to vary the polarization angle θ. Phase and amplitude distributions were mapped using interferometry.
5：Data Analysis Methods:
Data were analyzed by fitting line profiles with polynomials to remove noise, and simulations were performed using the finite-difference time-domain method to compare with experimental results.
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