Near-field nonlinear optical spectroscopy of Langmuir-Blodgett films

摘要

Using an uncoated fiber tip as a light source and a multilayer Langmuir-Blodgett film of 2-docosylamino-5-nitropyridine as a sample, we obtain near-field images at the fundamental-harmonic (FH) and secondharmonic (SH) wavelengths for different polarizations and wavelengths of the pump light. The spatial resolution of-100 nm is achieved in near-field SH images that are not correlated with either the topographical or the FH images. It is directly demonstrated that SH generation is most concentrated inside submicrometersized (300-500 nm) crystallike domains, which are oriented differently but predominantly in the dipping direction and whose SH efficiency is maximum for pump wavelengths in the range of 770-800 nm. # 1998 Optical Society of America [S0740-3232(98)01308-8] OCIS codes: 170.5810, 190.4350, 190.4710, 240.0310, 300.6320, 310.6860.