Off-axis directional beaming via photonic crystal surface modes

We investigated off-axis directional beaming from a photonic crystal (PC) waveguide. We theoretically and experimentally demonstrated that it is possible to control beaming from a PC waveguide via PC surface modes using a gratinglike layer with different periods on different sides of the waveguide. We observed off-axis directional beaming with full width at half maximum of 10 degrees with a beaming angle of 14 degrees from a PC waveguide. Since the beaming angle only depends on the periods of the gratinglike layer on the output side, this beaming angle can be easily changed by arranging the grating periods asymmetrically. (C) 2008 American Institute of Physics.