Creation of subwavelength light needle, equidistant multi-focus, and uniform light tunnel

A versatile method is presented for the creation of ultra-long subwavelength light needles with high-purity longitudinal polarization, uniform light tunnels of variable length and with narrow dark channel, or coaxially equidistant multi-focus with prescribed number and spacing. This is achieved by modulating the radially or azimuthally polarized vector beams using the same kind of amplitude apodization filter under a high numerical aperture aplanatic lens system. These peculiar focusing patterns may suit a variety of potential applications, such as optical trapping, particle acceleration, atom optical experiments, and near-field scanning optical microscopy.