Step towards sum frequency generation spectromicroscopy at a submicronic spatial resolution

A near-field optical device has been developed to collect sum frequency signal, generated in an AsGa single crystal sample by two pulsed lasers, one fixed at a wavelength of 532 nm and the other tunable in midinfrared. The sum frequency signal was collected with an uncoated silica tip. When the tip sample distance was increased, a strong decrease of the collected sum frequency signal was observed: the signal was divided by 2 for an increase of about 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 generation spectroscopy. (C) 2001 American Institute of Physics.