| 主权项 |
1. An optical element comprising a transmissive layer comprising first and second optical media, wherein:
(a) the first and second optical media are substantially transparent over an operational wavelength range including a design vacuum wavelength λ0 and are characterized by differing respective first and second wavelength-dependent bulk refractive indices n1(λ) and n2(λ), and the first optical medium comprises a substantially solid material; (b) the first and second optical media are arranged within the layer as a contiguous multitude of discrete volumes, including a subset of volumes of the multitude having a largest transverse dimension less than about λ0, wherein each discrete volume comprises either the first optical medium or the second optical medium, but not both; (c) the contiguous multitude of discrete volumes is arranged so that (i) any given simply connected sample volume of the transmissive layer, said sample volume having transverse dimensions about equal to λ0 and extending from the first surface through the transmissive layer to a second surface of the transmissive layer, includes only the first optical medium, only the second optical medium, or both the first and second optical media of at least portions of two or more of the discrete volumes, and (ii) any straight-line path, extending substantially perpendicularly from a first surface of the transmissive layer to a second surface of the transmissive layer, passes through only the first optical medium, through only the second optical medium, or through only one discrete volume of each of the first and second optical media; (d) the discrete volumes of the multitude are distributed on the transmissive layer so that (2π/λ0)·(n1(λ0)·d1(x,y)+n2(λ0)·d2(x,y)), as a function of two-dimensional position coordinates x and y along the first surface of the transmissive layer, averaged over a sampling area having a largest transverse dimension about equal to λ0 along the first surface of the transmissive layer, is substantially equal to a specified position-dependent effective phase transformation function φeff(x,y), or substantially equal to ½·φeff(x,y), where (i) d1(x,y) and d2(x,y) are the respective local distances through the first and second optical media along the straight-line path through a given position (x,y), and (ii) φeff(x,y) varies with both x and y; and (e) the optical element is structurally arranged to as to receive an optical signal incident on the first surface within the transmission region and to transmit or reflect at least a portion of the incident optical signal transformed substantially according to the effective phase transformation function φeff(x,y). |
