Wavelength-dependent linear and nonlinear optical absorption of triangular silver nanoplates
摘要
This work presents an experimental investigation of the wavelength-dependent linear and nonlinear optical absorption properties of triangular silver nanoplates. The nanoplates, synthesized with edge lengths in the range of 20–50 nm, exhibit two distinct localized surface plasmon resonance peaks around 410 nm and 690 nm, arising from their anisotropic geometry. Linear absorption coefficients were experimentally determined at laser wavelengths of 405 nm, 532 nm, and 655 nm using transmission measurements, yielding values of 2.30, 1.64, and 1.78 cm−1, respectively. Nonlinear absorption behavior was systematically investigated using the open-aperture Z-scan technique with continuous-wave diode laser excitation. The normalized transmission profiles exhibited clear and symmetric signatures of saturable absorption, and the nonlinear absorption coefficients (β) were evaluated to be − 22.6 × 10−3, − 1.0 × 10−3, and − 5.8 × 10−3 cm/W at 405 nm, 532 nm, and 655 nm, respectively. The strongest nonlinear response was observed at 405 nm, in close proximity to the dominant localized surface plasmon resonance mode of the nanoplates. These results highlight the critical role of excitation wavelength and plasmonic resonance coupling in governing the third-order nonlinear optical response, and demonstrate the potential of triangular silver nanoplates for wavelength-selective photonic and optoelectronic applications.