# US 7,746,550 B2 · Terahertz or infrared filter using shape resonance

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- Number: US 7,746,550 B2
- Document ID: US7746550B2
- Status: Granted
- Kind: B2
- Application number: 11/491,961
- Filed: 2006-07-25
- Published: 2007-07-19
- Granted: 2010-06-29
- Earliest claimed: 2006-01-18
- Assignees: Seoul National University Industry Foundation
- Inventors: Dae-Sik Kim; Sae Chae Jeoung; Joong Wook Lee; Min Ah Seo
- Web page: https://patentgrep.com/patent/US7746550B2

## CPC

- G02B 5/204: {in which spectral selection is performed by means of a conductive grid or array, e.g. frequency selective surfaces (for use with wavelengths longer than the infrared light H01Q15/0006)}
- G02B 5/208: {for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation}
- G02B 5/30: Polarising elements (light-modulating devices with active elements G02F1/00)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A filter having a high transmittance. The filter includes a substrate having a first surface and a second surface, and a periodic or random array of through-holes formed so as to pass through the first surface and the second surface. The through-hole has a size of subwavelength at a range of infrared and terahertz wave. Here, transmission resonance characteristic of incident light on the first surface is controlled by a shape of the through-hole.

## Claims

### Claim 1

A single resonance filter having a single transmission resonance wavelength using shape resonance with a high transmittance, the resonance filter comprising:
a substrate having a first surface and a second surface; and
a periodic or random array of through-holes formed so as to pass through the first surface and the second surface, the through-hole having a size of subwavelength and a symmetrical shape with respect to a polarization direction of incident light toward the first surface,
wherein a single transmission resonance wavelength is determined by the shape of the through-hole, and wherein the symmetrical shape includes a square shape, a rectangular shape, a circular shape, a slit shape, or a combination thereof,
the resonance filter further comprising two metallic layers placed on the first surface of the substrate, one metallic layer being fixed and the other metallic layer being adjusted along a direction perpendicular to the polarization direction such that incident light can continuously recognize the variations in length of the rectangular shape in the direction perpendicular to the polarization directions, thereby the single transmission resonance wavelength is continuously varying.

### Claim 2 (depends on 1)

The single resonance filter as claimed in claim 1, wherein the single resonance filter exhibits non-variable omni-directional function regardless of an angle of the incident light with respect to the first surface since the length thereof perpendicular to the polarization direction of the incident light is adjusted to be made so long that transmission resonance wavelength becomes far away from Rayleigh line due to periodicity.

### Claim 3 (depends on 1)

The single resonance filter as claimed in claim 1, wherein the substrate is formed of a material having free electrons.

### Claim 4 (depends on 3)

The single resonance filter as claimed in claim 3, wherein the material having free electrons includes a metal or a semiconductor.

### Claim 5 (depends on 1)

The single resonance filter as claimed in claim 1, wherein the symmetrical shape has a wavelength transformation function by varying the ratio of two lengths along two polarization directions of the incident light perpendicular to each other.

### Claim 6 (depends on 1)

The single resonance filter as claimed in claim 1, wherein the array of the through-holes having the symmetrical shape is configured such that same shapes are disposed at regular intervals along advancing direction of the incident light to thereby transmit more than 90% of quasi-monochromatic wavelength having a narrow line width among the incident light.

### Claim 7 (depends on 1)

The single resonance filter as claimed in claim 1, wherein the single resonance filter exhibits a high transmittance capable of transmitting more than 90% of the incident light.