研究目的
Investigating the extraordinarily large third-order optical nonlinearity in Au nanorods under nanowatt laser excitation.
研究成果
The study demonstrated that a 60-nm thin film of randomly distributed gold nanorods exhibits extraordinarily large third-order nonlinear optical absorption under an excitation power as low as 100 nanowatts. The sign of the nonlinear absorption could be controlled by changing the excitation wavelength or pump power. The optical Kerr effect measurement showed that the intrinsic third-order optical susceptibility of the sample is quite large compared to other nanostructures. These findings offer new opportunities for plasmonic nanostructures in applications of integrated photonic devices.
研究不足
The nonlinear refraction was too weak to be obtained under low power excitation. The contribution of transient absorption to the OKE signal could be neglected, but this requires verification.
1：Experimental Design and Method Selection:
The study involved preparing a 60-nm thick gold nanorod thin film (GNRF) on a glass substrate and investigating its nonlinear optical properties using Z-scan, optical Kerr effect (OKE), and pump-probe techniques.
2：Sample Selection and Data Sources:
GNRF was obtained from a commercial company (NanoSeedz), and its absorbance spectra and morphologies were recorded using a UV?vis?NIR spectrophotometer and a scanning electron microscope (SEM), respectively.
3：List of Experimental Equipment and Materials:
A Ti:Sapphire laser (Coherent, Mira 900, 76 MHz, 130 fs) was used as a light source for Z-scan measurements. Homemade pump-probe setups were used for OKE and transient transmission measurements.
4：Experimental Procedures and Operational Workflow:
The laser beam was focused onto the GNRF sample, and both open-aperture and closed-aperture Z-scan curves were produced. For OKE measurement, the laser beam was divided into two branches with a power ratio of 10:1, and the polarization angle between the pump and probe beams was set to 45°.
5：5°.
Data Analysis Methods:
5. Data Analysis Methods: The nonlinear absorption coefficient and third-order optical susceptibility were calculated using theoretical expressions and fitting functions.
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