An arbitrarily designed main focus with high intensity generated by a composite fractional fractal zone plate

In this paper a composite fractional fractal zone plate (CFFZP) based on the corresponding fractional fractal zone plate is proposed to enhance the intensity of the arbitrarily designed main focus. The construction method of the CFFZP has been illustrated in the simulation. It has been also proved in the simulations and experiments that the CFFZP generates the main focus with higher intensity. The proposed zone plate can be applied to stably trap a particle at an arbitrary plane and generate a clearer image at an arbitrary axial position.