Off-axis directional beaming via photonic crystal surface modes

Abstract

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° with a beaming angle of 14° 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.