PHOTONIC CRYSTAL LENS WIDELY ADJUSTABLE IN FOCAL LENGTH AND DESIGN METHOD THEREFOR

摘要

A photonic crystal lens widely adjustable in focal length and a design method therefor. The method comprises: preliminarily selecting a photonic crystal material and structure to obtain an equal-frequency diagram, and finding a frequency-sensitive auto-collimation region; determining a working phase space according to an actually required working frequency interval and an incidence angle range; optimally designing structure parameters and material parameters of the photonic crystal, so that the sensitivity of an equal-frequency contour curvature to the refractive index of the photonic crystal material is as high as possible, and equal-frequency contour degeneracy is also prevented from occurring in the working phase space; and selecting, according to material characteristics, an appropriate mode to change the refractive index of a constituent material of the photonic crystal, thereby changing the position of a beam focus point or a virtual focus point. Under the same conditions, the refractive index change required by this scheme is multiple orders of magnitude smaller than that of a block material or a common photonic crystal, and is easy to be achieved. The designed photonic crystal lens has excellent integration and can be applied in the fields such as beam focusing, beam width control and sensitivity detection.