Circular Grating Coupler for Creating Focused Azimuthally and Radially Polarized Beams

Here we show a planar optical circuit design that takes light from an input waveguide and creates a focused azimuthally or radially polarized beam emanating from the surface of the substrate. It is demonstrated using silicon-­‐on-­‐insulator waveguides and does not require any external components to focus the beam. The focal spot size can be sub wavelength[1] and is potentially useful for lithography, imaging, optical data storage, optical trapping, optical excitation of molecules, or coupling to optical fibers.