Step towards sum frequency generation spectromicroscopy at a submicronic spatial resolution

A near-field optical device has been developed to collect sum frequency sig nal, generated in an AsGa single crystal sample by two pulsed lasers, one f ixed at a wavelength of 532 nm and the other tunable in midinfrared. The su m frequency signal was collected with an uncoated silica tip. When the tip sample distance was increased, a strong decrease of the collected sum frequ ency signal was observed: the signal was divided by 2 for an increase of ab out 100 nm of the distance between the nanoprobe end and the sample surface . Without demonstrating submicronic lateral spatial resolution, this letter is, however, a first step towards a microscopic device of sum frequency ge neration spectroscopy. (C) 2001 American Institute of Physics.