The nonlinear refraction coefficient of silica aerogel was estimated to be ∼−1.5×10−15 m2/W (∼−3.67×10−9 esu) with a signal-beam z-scan spectroscopy. The third-order nonlinear refraction coefficient of nanostructure silica aerogel was almost five orders larger than the nonlinear refraction (χ3) of bulk material. The large nonlinear refraction with high nonlinear figure of merit is an ideal optical property for nonlinear optical applications.
Articles you may be interested inTip-enhanced near-field Raman spectroscopy with a scanning tunneling microscope and side-illumination optics Rev. Sci. Instrum. 79, 073706 (2008);The sample imperfection induced distortions in the closed Z-scan curve are analyzed. It is found that both the magnitudes of the peak and valley transmittances and the shape of the curve are distorted significantly by the inhomogeneous thickness, the nonuniform nonlinearity, and the curved surfaces of the sample. The results suggest that the I-scan method is a more practical choice for the measurement of the third-order nonlinear susceptibility of an inhomogeneous sample.
Cadmium chalcogenide nanocrystals at ~2-10 nm were synthesized using with a chemical colloidal reaction technique. Strong blue-shifts of the CdTe, CdSe and CdS nanocrystals absorption bandedge and the atomic-like discrete energy states indicate an exciton quantum confinement. Z-scan and I-scan nonlinear spectroscopy revealed that the CdTe nanocrystals quantum dot in toluene (~8 x 10 -5 mol/L) has the negative nonlinearity (self-defocusing) with ~ -1 x 10 -13 m 2 /W and a high nonlinear figure of merit of ~200. For the optical power self-limiting experiment, the CdTe nanocrystals was almost opaque above ~0.8 MW/cm 2 at near valley (z~6.9 cm) of Z-scan. The nonlinear optical applications include optical power self-limiting for homeland security of human-eye and sensor protection against potential laser terror threats, and agile laser threats on the battle field, optical switching, and pulse shaping in optical parametic oscillator/optical parametic generator.
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