Two-photon luminescence contrast by tip-sample coupling in femtosecond near-field optical microscopy

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• 作者：Anke Horneber ; Frank Wackenhut ; Kai Braun ; Xiao Wang ; Jiyong Wang…
• 刊名：Applied Physics B
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：123
• 期：1
• 全文大小：
• 刊物类别：Physics and Astronomy
• 刊物主题：Physics, general; Physical Chemistry; Optics, Lasers, Photonics, Optical Devices; Quantum Optics; Engineering, general;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-0649
• 卷排序：123

文摘

We investigate the role of tip-sample interaction in nonlinear optical scanning near-field microscopy. The experiment was performed by tightly focusing femtosecond laser pulses onto a sharp gold tip that was positioned in close proximity to the surface of a sample with gold nanostructures on a Si-substrate by shear force feedback. The nonlinear optical signal consists of two-photon photoluminescence and second harmonic signal from the gold tip and the gold nanostructures. These signals can be used to characterize different coupling parameters such as geometry, material and width of the tip-sample gap and enable to reveal the mechanism responsible for the image contrast. Under the excitation with 776-nm and 110-fs laser pulses nonlinear imaging is almost background free and yields super resolution showing features with dimensions significantly below the diffraction limit with a signal intensity following quadratic excitation power law.