Fresnel lens fabrication

Claim 1

A method of fabricating a Fresnel lens, said lens having an electromagnetic radiation focusing cross-sectional geometry, comprising a plurality of concentric zones and wherein each of said zones has a predetermined width with the width of each zone decreasing with increasing radius, said method comprising the steps of providing a first material and a second material different from the first, at least one of said materials propagating electromagnetic radiation impinging thereon, forming alternating layers of said first material and layers of said second material on a substrate, all of said first and said second material layers being concentric and each of said second material layers being formed over an immediately preceding one of said first material layers, each of said first and second material layers having a predetermined thickness in a direction substantially perpendicular to a longitudinal axis of said substrate, drawing the substrate and said first and second material layers down until the thickness of each of said first and second material layers is substantially equal to the width of a different one of said zones, where each layer corresponds to each zone, taken in the radially outward direction, said drawing providing a Fresnel lens preform of predetermined diameter having said radiation focusing cross-sectional geometry upon subsequent cutting, etching and depositing, cutting a predetermined length of said preform to define two planar end faces, etching alternate ones of said layers, the unetched layers being material which propagates the electromagnetic radiation propagating therethrough, and depositing a third material into said etched layers, said third material being different from said first and second materials and said third material either absorbing or phase-shifting the electromagnetic radiation impinging thereon so that said third material and the unetched material provide focusing of electromagnetic radiation propagating through said two end faces and thereby form said Fresnel lens.

Claim 2

A method of fabricating a Fresnel lens, said lens having an electromagnetic radiation focusing cross-sectional geometry, comprising a plurality of concentric zones and wherein each of said zones has a predetermined width with the width of each zone decreasing with increasing radius, said method comprising the steps of providing a first material and a second material different from the first, at least one of said materials propagating electromagnetic radiation impinging thereon, forming alternating layers of said first material and layers of said second material on a substrate, all of said first and said second material layers being concentric and each of said second material layers being formed over an immediately preceding one of said first material layers, each of said first and second material layers having a predetermined thickness in a direction substantially perpendicular to a longitudinal axis of said substrate, drawing the substrate and said first and second material layers down until the thickness of each of said first and second material layers is substantially equal to the width of a different one of said zones, where each layer corresponds to each zone, taken in the radially outward direction, said drawing providing a Fresnel lens preform of predetermined diameter having said radiation focusing cross-sectional geometry upon subsequent cutting, etching and depositing, cutting a predetermined length of said preform to define two planar end faces, etching alternate ones of said layers, the unetched layers being material which propagates the electromagnetic radiation propagating therethrough, and depositing a third material into said etched layers, said third material being different from said first and second materials and said third material either absorbing or phase-shifting the electromagnetic radiation impinging thereon so that said third material and the unetched material provide focusing of electromagnetic radiation propagating through said two end faces and thereby form said Fresnel lens.