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US-12620686-B2 - Metalens

US12620686B2US 12620686 B2US12620686 B2US 12620686B2US-12620686-B2

Abstract

A metalens capable of concentrating terahertz waves having a high light concentration efficiency. The metalens includes a first region that has a plurality of microstructures disposed therein to concentrate terahertz waves; and a second region that is a region that surrounds the first region and that is a region different from the first region, in which in a case where terahertz waves having a wavelength of 0.3 mm, a wavelength of 1 mm, and a wavelength of 3 mm are incident, assuming that a wavelength having a highest light concentration efficiency is a wavelength X, a transmittance of the terahertz waves having the wavelength X in the first region is a transmittance T1, and a transmittance of the terahertz waves having the wavelength X in the second region is a transmittance T2, the transmittance T2 is lower than the transmittance T1.

Inventors

  • Hideki Yasuda
  • Yukito Saitoh

Assignees

  • FUJIFILM CORPORATION

Dates

Publication Date
20260505
Application Date
20240924
Priority Date
20220329

Claims (10)

  1. 1 . A metalens comprising: a first region that has a plurality of microstructures disposed therein to diffract and concentrate terahertz waves; and a second region that surrounds the first region and that is a region different from the first region, wherein in a case where terahertz waves having a wavelength of 0.3 mm, a wavelength of 1 mm, and a wavelength of 3 mm are incident, assuming that a wavelength having a highest light concentration efficiency is a wavelength X, a transmittance of the terahertz waves having the wavelength X in the first region is a transmittance T1, and a transmittance of the terahertz waves having the wavelength X in the second region is a transmittance T2, the transmittance T2 is lower than the transmittance T1.
  2. 2 . The metalens according to claim 1 , wherein the transmittance T1 and the transmittance T2 satisfy “the transmittance T2/the transmittance T1<0.5”.
  3. 3 . The metalens according to claim 2 , wherein the transmittance T2 is 10% or less.
  4. 4 . The metalens according to claim 3 , wherein the transmittance T2 is 0%.
  5. 5 . The metalens according to claim 2 , wherein assuming that a diameter of the first region is R1 [mm], the R1 and the wavelength X satisfy “R1/X<25”.
  6. 6 . The metalens according to claim 1 , wherein the transmittance T2 is 10% or less.
  7. 7 . The metalens according to claim 6 , wherein the transmittance T2 is 0%.
  8. 8 . The metalens according to claim 7 , wherein assuming that a diameter of the first region is R1 [mm], the R1 and the wavelength X satisfy “R1/X<25”.
  9. 9 . The metalens according to claim 6 , wherein assuming that a diameter of the first region is R1 [mm], the R1 and the wavelength X satisfy “R1/X<25”.
  10. 10 . The metalens according to claim 1 , wherein assuming that a diameter of the first region is R1 [mm], the R1 and the wavelength X satisfy “R1/X<25”.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Continuation of PCT International Application No. PCT/JP2023/011398 filed on Mar. 23, 2023, which was published under PCT Article 21(2) in Japanese, and which claims priority under 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2022-053533 filed on Mar. 29, 2022. The above applications are hereby expressly incorporated by reference, in their entirety, into the present application. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metalens using a metasurface structure. 2. Description of the Related Art The metalens is an optical element capable of realizing a lens function such as light concentration and collimation in a substantially flat plate shape by imparting desired phase characteristics to transmitted waves. Such a metalens is usually configured by arrangement of microstructures formed of a metal or a dielectric substance, which is provided on a flat plate. A 6G communication system (sixth-generation mobile communication system) has been attracting attention as a next-generation communication standard of a 5G communication system (fifth-generation mobile communication system). In the 6G communication system, electromagnetic waves of so-called terahertz waves (terahertz band) are used for communication. In order to control the terahertz waves with a normal lens made of glass or the like, it is necessary to use an extremely thick dome-like lens. In consideration of a size of the communication system or the like, it is preferable that the optical element used in the system is thin. Therefore, in the 6G communication system, a metalens that can be implemented by an optical element having a substantially flat plate shape has been attracting attention as an optical element for concentrating and collimating the terahertz waves. For example, a metalens, which collimates diffusive terahertz waves emitted from a resonant tunneling diode, is described in “Metalens mounted on a resonant tunneling diode for collimated and directed terahertz waves” Takehito Suzuki et al. Vol. 29, No. 12/7 Jun. 2021/Optics Express 18988. The metalens is formed by symmetrically arranging microstructures consisting of metal wires on both surfaces of a substrate made of a dielectric substance such as a cycloolefin polymer. SUMMARY OF THE INVENTION As described in “Metalens mounted on a resonant tunneling diode for collimated and directed terahertz waves” Takehito Suzuki et al. Vol. 29, No. 12/7 Jun. 2021/Optics Express 18988, the metalens is able to concentrate and collimate terahertz waves by a thin optical element having a flat plate shape. However, according to the studies by the present inventors, there is a problem in that a metalens that concentrates terahertz waves has a lower light concentration efficiency than a lens that concentrates visible light. An object of the present invention is to solve the above-mentioned problem of the related art and to provide a metalens corresponding to terahertz waves, the metalens having a high light concentration efficiency in a case where the terahertz waves are incident. In order to solve the above-mentioned problem, the present invention has the following configurations. [1] A metalens according to an aspect of the present invention comprises:a first region that has a plurality of microstructures disposed therein to diffract and concentrate terahertz waves; anda second region that surrounds the first region and that is a region different from the first region,in which in a case where terahertz waves having a wavelength of 0.3 mm, a wavelength of 1 mm, and a wavelength of 3 mm are incident, assuming that a wavelength having a highest light concentration efficiency is a wavelength X,a transmittance of the terahertz waves having the wavelength X in the first region is a transmittance T1, anda transmittance of the terahertz waves having the wavelength X in the second region is a transmittance T2,the transmittance T2 is lower than the transmittance T1. [2] In the metalens according to [1], the transmittance T1 and the transmittance T2 satisfy “the transmittance T2/the transmittance T1<0.5”.[3] In the metalens according to [1] or [2], the transmittance T2 is 10% or less.[4] In the metalens according to [3], the transmittance T2 is 0%.[5] In the metalens according to any one of [1] to [4], assuming that a diameter of the first region is R1 [mm], the R1 and the wavelength X satisfy “R1/X<25”. According to the present invention, in the metalens, it is possible to concentrate and collimate terahertz waves having a high light concentration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view conceptually showing an example of a metalens according to an embodiment of the present invention. FIG. 2 is a side view conceptually showing the example of the metalens according to the embodiment of the present invention. FIG. 3 is a graph conceptually showing a transmitta