Beam steering for wireless optical links based on an optical phased array in silicon

The ability to steer optical beams, crucial to the operation of high-speed optical wireless links may be achieved using optical phased array antennas which have significant potential in this application. The beam formed by the phased array antennas is steered by tuning the relative phase difference between the adjacent antenna elements which may be achieved nonmechanically. In this paper, the characteristics and behaviour of two dimensional optical phased arrays with a structure composed of 2×2, 4×4, and 16×16 antenna elements in beam steering are verified. The wavelength beam steering of −0.16°/nm is measured along the θ direction with a required steering range (between main lobes) of 1.97° within a −3 dB envelop of 5° extent in the θ direction and 7° extent in the Φ direction. To achieve twodimensional beam steering, thermo-optic beam steering can be used in Φ direction. It is found that the thermooptic phase tuning departs the expected quadratic dependence and is well characterised by a quartic dependence upon heater current or voltage.