Monopulse ladar: super-resolved 3D localization with Si-photonic serpentine optical phased arrays.

We present an optical ranging and super-resolution object localization method, monopulse ladar, used to determine the angle of a point target in two dimensions to a few percent of an optical beam width from differential measurements of four just-resolved waveform-encoded beams while simultaneously providing target range via either coherent or incoherent coded waveform correlation. A common optical carrier is shifted by four GHz-scale tones, each modulated with distinct ranging waveforms, which when transmitted from a Si-photonic 2D wavelength-steered serpentine optical phased array (SOPA) aperture form an encoded rectangular beam cluster that propagates to and scatters from a distant point target. Superposed backscattered target returns from each beam are decoded by correlation with reference waveforms at the receiver.