研究目的
Investigating the enhancement of the second harmonic generation (SHG) from WS2 monolayers by cooperating with SiO2 dielectric microspheres (MSs) and its potential applications in photonic sensing and functional nanodevices.
研究成果
The study successfully demonstrated a 20-fold enhancement of the optical SHG from WS2 monolayers by cooperating with SiO2 dielectric MSs. The enhancement is attributed to the increased field intensity and enlarged collection efficiency produced by the SiO2 MSs. The SHG enhancement was found to be sensitive to the surrounding refractive index of the SiO2 MS, indicating potential for photonic sensing applications. The hybrid dielectric structure offers a low-cost and efficient approach to enhancing SHG emission in nanostructures.
研究不足
The study is limited by the requirement that the SHG emission is well overlapped with the resonant spectra of the nanostructures, which may limit the available spectral range. Additionally, the fabrication processes of metal nanostructures and microcavities are complex and costly.
1：Experimental Design and Method Selection:
The study involved the fabrication of WS2–MS hybrid dielectric structures and the measurement of SHG enhancement using a femtosecond-pulsed Ti:sapphire laser. Numerical simulations based on the finite-element method were performed to understand the underlying mechanisms.
2：Sample Selection and Data Sources:
WS2 monolayers were grown on a sapphire substrate by chemical vapor deposition. The SHG measurements were conducted on these monolayers with and without SiO2 MSs.
3：List of Experimental Equipment and Materials:
A femtosecond-pulsed Ti:sapphire laser (centered at 804 nm, ≈8 fs, 80 MHz), a 40 × objective (NA = 0.65), a CCD camera, a spectrometer, and a 720 nm short-pass filter were used. SiO2 MSs of various diameters (1, 2, 5, and 10 μm) were employed.
4：65), a CCD camera, a spectrometer, and a 720 nm short-pass filter were used. SiO2 MSs of various diameters (1, 2, 5, and 10 μm) were employed.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The laser beam was focused onto the samples, and the reflected optical signal was collected by the same objective. The SHG spectra were measured with and without the SiO2 MSs under identical conditions.
5：Data Analysis Methods:
The SHG enhancement factor was calculated as the ratio between the SHG intensity of the WS2 monolayer with and without the SiO2 MS. Numerical simulations were used to analyze the field distribution and collection efficiency.
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