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Polymer-based optical waveguide circuits for photonic phased-array antennas

Photonic phased array antennas represent one of the most critical technologies for both national defense and civilian wireless communications. In this paper, we present a novel compact detector-switched polymeric waveguide true-time- delay module, which is a crucial building block for advanced wideband photonic phased array antennas. The photolithographically defined ultra-low-loss polymeric waveguides provide us an attractive solution for achieving ultra long delay time over tens of nsec with ultra fine resolution of less than 1 ps. The 2D distributed waveguide grating couplers tap the optically encoded microwave signal, propagating along the polymeric channel waveguide, to high- speed photodetectors. These photodetectors can be electrically switched on and off independently for selecting different delay times. The appropriate delay time is equal to the time of flight along the waveguide. We have demonstrated that such optical true-time-delays can be implemented in such a device scheme with the RF spectrum of 11 GHz to 40 GHz. The optically encoded microwave signals are obtained by using semiconductor-laser-based optical heterodyne technique. Such a monolithic integrated module not only reduces the cost associated with optoelectronic packaging, but also reduces the system payload with an improved reliability.