Gradient index lens using effective refractive index of microstructure arranged in radial pattern, and method for manufacturing same

• US 9,772,476 B2
• Filed: 12/14/2012
• Issued: 09/26/2017
• Est. Priority Date: 01/20/2012
• Status: Active Grant

• Current Assignee: Korea Advanced Institute of Science and Technology
• Original Assignee: Korea Advanced Institute of Science and Technology
• Inventors: Jeong, Ki-Hun, Park, Sang-Gil, Lee, Youngseop
• Primary Examiner(s): Allen, Stephone B
• Assistant Examiner(s): FISSEL, TRAVIS S
• Application Number:
  US14/372,047
• Publication Number:
  US 20150002927A1
• Time in Patent Office: 1,747 Days
• Field of Search: 359653, 359652, 359654, 348 59, 348 49, 427515
• CPC Class Codes: B29C 45/372 provided with means for marking or patterning, e.g. numbering articles
• CPC Class Codes: B29D 11/00028 Bifocal lenses; Multifocal lenses
• CPC Class Codes: B29L 2011/0016 Lenses
• CPC Class Codes: G02B 13/14 for use with infrared or ultraviolet radiation G02B13/008, G02B13/16 take precedence
• CPC Class Codes: G02B 2207/107 Porous materials, e.g. for reducing the refractive index
• CPC Class Codes: G02B 3/0087 with index gradient

Abstract

Provided are a gradient index lens using the effective refractive index of a microstructure operating in the terahertz frequency regions and mid-infrared regions at wavelengths of 0.8 m to 3 mm and a method for manufacturing the same. Based on the effective medium theorem, the effective refractive index is controlled by using a structure smaller than the mid-infrared and terahertz wavelength, and a gradient can be provided for the refractive index in a radial direction and in an axial direction. Thus, beams in the mid-infrared and terahertz frequency region can be converged.

Claims

1. A gradient index lens using an effective refractive index of a microstructure converging an electromagnetic wave from mid-infrared to terahertz wave, comprising:

a flat plate type substrate consisting of Si or GaAs and having a predetermined thickness; and

microstructures formed in the substrate to control an effective refractive index of the flat plate type substrate,

wherein the microstructures include through-holes arranged in the substrate, the through-holes having a circular shape, a polygonal shape, or a composite shape, the through-holes having a diameter smaller than a wavelength of the electromagnetic wave,

wherein each of the through-holes does not enclose one another, and

wherein the diameter of the through-holes or an interval therebetween is gradually increased or reduced radially from a center of the substrate such that the refractive index of the microstructure gradually changes radially from the center of the substrate.

2. The gradient index lens of claim 1, wherein the substrate is a single dielectric substrate.

3. The gradient index lens of claim 1, wherein the microstructure is a structure that is formed by dry etch or wet etch.

4. The gradient index lens of claim 1, wherein the microstructure is arrayed so that a distribution of refractive index of the substrate has one of parabolic equation, multi-order equation, square root of a multi-order equation, and sphere distributions, in a surface direction and a depth direction.

10. The gradient index lens of claim 1, wherein the electromagnetic wave travels parallel to the direction to which the through-holes are extended such that the electromagnetic wave is converged.

5. A method for manufacturing a gradient index lens using an effective refractive index of a microstructure converging an electromagnetic wave from mid-infrared to terahertz wave, the method comprising:

providing a flat plate type master substrate consisting of Si or GaAs;

forming a mask layer on the master substrate;

forming an etch pattern for forming the microstructure having a diameter smaller than a wavelength of the electromagnetic wave on the mask layer;

etching the substrate using the patterned mask layer as an etch mask;

removing the remaining mask layer;

injecting a polymer into the etched substrate;

hardening the injected polymer; and

separating the hardened polymer from the etched substrate to form a polymer lens in which the microstructure is formed,

wherein in the forming of the etch pattern of the microstructure, the etch pattern is formed so that through-holes having a circular shape, a polygonal shape, or a composite shape are arranged in the substrate, the through-holes having a diameter being smaller than the wavelength of the electromagnetic wave,

wherein each of the through-holes does not enclose one another, and

wherein the diameter of the through-holes or an interval therebetween is gradually increased or reduced radially from a center of the substrate such that the refractive index of the microstructure gradually changes radially from the center of the substrate.

6. The method of claim 5, wherein in the etching of the substrate, the substrate is etched by dry etch or wet etch.

7. The method of claim 6, wherein the dry etch uses at least one of reactive ion etch, deep reactive ion etch, and plasma etch.

8. The method of claim 6, wherein the wet etch uses isotropic wet etch or anisotropic wet etch.

9. The method of claim 5, wherein the microstructure is arrayed so that a distribution of refractive index of the substrate has one of parabolic equation, multi-order equation, square root of a multi-order equation, and sphere distributions, in a surface direction and a depth direction.

11. The method of claim 5, wherein the electromagnetic wave travels parallel to the direction to which the through-holes are extended such that the electromagnetic wave is converged.