An optimization-free approach is proposed for generating optical needle and bright spot arrays with controllable distributions. This is achieved by inversely focusing the radiation pattern from a collinear antenna array whose elements are placed along an optical axis and whose currents in each element also flow along that direction, situated at the focus of a 4pi configuration. The shape and central location of the n th focusing field only depend on the length l _n and coordinate z _n of the n th element in collinear array, respectively. The number of focal fields is determined by the number of elements in the array.

A photonic nanojet (PNJ) is a highly confined light beam that focuses from the shadow side of microparticles. In $46.47\lambda $ this work, we propose a PNJ with ultrahigh quality factor formed by dielectric truncated microtoroid. The key properties of PNJ, such as the maximum intensity, the length of PNJ, the full-width at half maximum (FWHM), are studied in detail using finite-difference time-domain (FDTD) analysis. The results show that a PNJ with an enhanced intensity of 55.21 times to the incident light, superlong length of $46.47\lambda $ and subwavelength FWHM of $0.77\lambda $ is formed by semi-microtoroid, thus, an ultrahigh quality factor of 3308.68 is achieved. More importantly, the properties of the PNJ are tunable by changing the truncated proportions of the microtoroid. The structure we proposed has the advantages of compact structure and simple experimental operation, which is expected to apply in many research fields, including optical detection, optical data storage, super-resolution image, nanopattern, nanolithography, and so on.