Near-field imaging of light diffraction out of slab waveguides

A collection scanning near-field optical microscope (SNOM) is used to image the propagating of light at telecommunication wavelengths (1520-1570 nm) along photonic crystal (PhC) slabs, which combine slab waveguides with in-plane PhCs consisting of one- and two-dimensional gratings. The efficient out-of-plane light diffraction is directly observed for both 1D and 2D gratings (period 590 nm) fabricated on silicon-on-insulator wafers and the corresponding SNOM images are presented. Using the obtained SNOM images, we analyze light intensity distributions along diffraction gratings measured at different wavelengths and/or distances from the sample surface. Gray-scale (a) topographical and (b) near-field optical images (60 X 60 mum(2)) taken at the wavelength lambda approximate to 1520 nm for the 1D PhC grating. The presumable location of the PhC grating is marked by the white rectangle.