Nanoscale-resolved subsurface imaging by scattering-type near-field optical microscopy

We demonstrate that scattering-type scanning near-field optical microscopy (s-SNOM) allows nanoscale-resolved imaging of objects below transparent surface layers at both visible and mid-infrared wavelengths. We show topography-free subsurface imaging at lambda= 633 nm. At lambda= 10.7 mu m, gold islands buried 50 nm below a polymer surface are imaged with a lateral resolution < 120 nm, corresponding to lambda/90. Studying oxide layers with systematically varied thicknesses we provide experimental evidence of mid-infrared near-field probing in depths > 80 nm. (c) 2005 Optical Society of America.