Near-field second-harmonic microscopy of thin ferroelectric films

Summary form only given. We present a near-field optical technique for second harmonic imaging using bare tapered optical fiber tips illuminated with femtosecond laser pulses. We show theoretically and experimentally that under illumination with P-polarized light the local SHG from the sample region under the tip is strongly enhanced even in the case of a dielectric tip. At the same time, the glass tip itself does not generate any measurable SH light. The local SH emission from the sample region under the tip is collected by the same tapered fiber which has a field of view on the order of the half of the wavelength of SH: light /spl lambda//sub 2/spl omega///2 in diameter, where /spl lambda//sub 2/spl omega//=400 nm (this is the resolution limit of a linear near-field microscope using bare tapered fibers). This configuration automatically solves one of the main problems in apertureless near-field microscopy: rejection of the background signal from the entire illuminated sample area. As a result, a spatial resolution of the order of 80 nm has been achieved in imaging of thin ferroelectric films.