Generation of a single-lobe radiation pattern from a phased-array laser using a near-contact variable phase-shift zone plate

A very simple and practical technique to generate a stable, narrow-angle single-lobe far-field radiation pattern from an ordinary twin-lobe phase-locked laser diode array is demonstrated. A variable phase-shift zone plate mounted close to the laser output facet is used to readjust the phase distribution of the array into an all-in-phase distribution producing the desired single narrow-lobe far-field pattern.