Optimization-free two-dimensional focal spot array generated by the use of radiation pattern from a planar antenna array

We propose an optimization-free method for creating a two-dimensional (2-D) identical focal spot array with a prescribed number, tunable interval, and controllable position. This can be realized easily by backward focusing of the field radiated from a planar antenna array situated at the foci of two high-numerical-aperture objective lenses. It is demonstrated here that the number of spots in the focal field array is equal to the number of elements in the planar antenna array; the intervals between the two adjacent spots along the x and y directions depend solely on the gaps between the two corresponding elements, and the position for each spot is determined totally by the location of the corresponding element. Furthermore, the intensity distribution of each spot in the 2-D focal array is identical. These kinds of 2-D focal spot arrays with controllable characteristics may find applications in parallel optical micromanipulation, multifocal multiphoton microscopy, and multiparticle parallel acceleration.