KR20220168091A - All-Dielectric Metasurface-based Fiber Meta-Tip Device Enabling Vortex Generation and Beam Collimation - Google Patents

Abstract

A dielectric metasurface-based optical fiber meta-tip device comprises: a metasurface formed by a combination of nanobrick unit cells, wherein one surface is formed with a substrate of the nanobrick unit cells and the other surface is formed with nanobricks of the nanobrick unit cells; an optical fiber connected to the center of the one surface of the metasurface and having an input or output optical signal transmitted thereto; and a fiber block which surrounds the end of the optical fiber, is connected to the one surface of the metasurface together with the optical fiber, and maintains the connection with the metasurface. The substrate is formed of silicon dioxide (SiO_2), and the nanobrick is formed of hydrogenated amorphous silicon (a-Si:H). The present invention can achieve sufficiently high transmission efficiency due to the low optical loss of a dielectric material.

Description

[0001] All-Dielectric Metasurface-based Fiber Meta-Tip Device Enabling Vortex Generation and Beam Collimation}

The present invention relates to an optical fiber metatip device based on a dielectric metasurface capable of generating a vortex beam and a collimated beam, and a data transmission system to which the same is applied.

In view of the planar structural configuration, metasurface elements have recently been steadily researched because they can be used to supplement or replace conventional refractive/diffractive optical elements, which are disadvantageous in constructing a miniaturized integrated optical system.

Optical metasurfaces are made of subwavelength nanostructures, especially composed of metallic or dielectric materials, and consist of so-called metaatoms known to be capable of locally controlling optical properties such as phase, amplitude and polarization at subwavelength scales.

In addition to forming an optical wavefront, metasurfaces have great advantages over conventional optical components such as waveplates for achieving efficient polarization conversion over a broadband.

A platform with such excellent optical modulation properties not only enables device miniaturization, but also opens the way to realizing multipurpose/multifunctional planar optical components that cannot be achieved with conventional methods. Recently, much research effort has been devoted to the creation of multifunctional metasurface devices, which are a type of single device that can perform multitasking.

Metamaterials are man-made composites whose unique properties can be achieved through careful structural alignment of dielectric and/or metallic subwavelength-sized components rather than chemical composition. . Like the reflection array and transmission array in radio frequency, the optical metasurface can perform a function of spatially adjusting the phase and amplitude distribution of the incident wave field using a two-dimensional array of resonant elements. Optical implementations, unlike high-frequency implementations, may rely on plasmonic or dielectric elements to exhibit deep subwavelength profiles.

Korean Patent Registration No. 10-2143535 discloses a two-function dielectric metasurface formed by a set of unit cells formed of a set of 8 horizontal and vertical (dx, dy) nanobricks of different sizes and capable of adjusting deflection or polarization tuned focusing It has been introduced about the element.

In addition, by processing the polarization of incident light projected forward or backward on the metasurface, three distinct functions can be obtained in the transmissive or reflective space.

In order to simplify the process of integrating multiple functions, a lot of research has been devoted to the combination of the two previous spatial multiplexing approaches (segmentation and interleaving) with the harmonic response.

For example, the paper [E. Arbabi, A. Arbabi, S. Mahsa Kamali, Y. Horie, A. Faraon, Sci. Rep. 2016, 6, 32803.], [E. Arbabi, A. Arbabi, S. M. Kamali , Y. Horie, A. Faraon, Optica 2016, 3, 628.], [D. Lin, A. L. Holsteen, E. Maguid, G. Wetzstein, P. G. Kik, E. Hasman, M. L. Brongersma, Nano Lett. 2016, 16 , 7671.]) and ([B. Wang, F. Dong, Q.-T. Li, D. Yang, C. Sun, J. Chen, Z. Song, L. Xu, W. Chu, Y.- F. Xiao, Q. Gong, Y. Li, Nano Lett. 2016, 16, 5235.], [W. Zhao, B. Liu, H. Jiang, J. Song, Y. Pei, Y. Jiang, Opt. Lett. 2016, 41, 147.]) introduces these technologies.

Also papers ([K. Yang, M. Pu, X. Li, X. Ma, J. Luo, H. Gao, X. Luo, Nanoscale 2016, 8, 12267.], [M. Q. Mehmood, S. Mei, S. Hussain, K. Huang, S. Y. Siew, L. Zhang, T. Zhang, X. Ling, H. Liu, J. Teng, A. Danner, S. Zhang, C.-W. Qiu, Adv. Mater. 2016 , 28, 2533.]), a wavelength and helicity-controlled metadevice technology for a multiplex optical vortices beam has been introduced.

(여기서 Φ는 방위각을 나타내고 l은 소용돌이 강도 프로파일의 링 반경을 결정하는 위상적 전하(topological charge)를 나타낸다.)을 갖는 나선형 파면(helical wavefront)을 나타내는 소용돌이빔(optical vortex beam.)에 관해 소개되고 있다. (Y. Zhang, W. Liu, J. Gao, X. Yang, Adv. Opt. Mater. 2018, 6, 1701228. 참조).In addition, the orbital angular momentum is transmitted and the azimuthal phase term

(Where Φ denotes the azimuthal angle and l denotes the topological charge that determines the ring radius of the vortex intensity profile.) An introduction to an optical vortex beam representing a helical wavefront. It is becoming. (See Y. Zhang, W. Liu, J. Gao, X. Yang, Adv. Opt. Mater. 2018, 6, 1701228.).

Also, recently, a transmissive metalens composed of identical plasmon nanorods having spatially varying orientations has been proposed to generate three focal points for circularly polarized light. Here, the metalens area is divided into three areas, each area consisting of one sub-metalens that is considered to focus incident left or right circularly polarized light at a designated focal plane.

Optical fiber plays an important role in many fields such as optical communication, remote sensing, and endoscopy because of its large data transmission capacity, imperviousness to electromagnetic interference, and light weight. there is. In order to alleviate these disadvantages, a method of controlling the beam emitted from the end face of the optical fiber has been performed by utilizing compact optical components including an optical fiber collimator, a lensed optical fiber and an expanded beam connector. From the point of view of a new integrated photonics platform called “lab-on-fiber,” metasurfaces built on the sides of optical fibers could enable the manipulation of traveling light in terms of spatial modes, phase, amplitude and polarization. there is. In particular, based on the “lab-on-fiber” method, research including fiber-tip lenses, surface plasmon resonance sensors, optical tweezers, polarimeters, and polarization converters has been conducted. However, these The research results are vulnerable to inherent ohmic losses associated with the metal structure.

Republic of Korea Patent Registration No. 10-2143535 (Double functional dielectric metasurface element capable of deflection or focusing control)

Khant Minn, Ho Wai Howard Lee, and Zhenrong Zhang, "Enhanced subwavelength coupling and nano-focusing with optical fiber-plasmonic hybrid probe: erratum," Opt. Express 28, 21855-21855 (2020).

An object of the present invention is to provide an optical fiber metatip device based on a dielectric metasurface capable of generating a vortex beam and a collimated beam.

Another object of the present invention is to provide a fiber optic metatip device having a polarization selective optical interconnection feature for optical interconnection.

According to one aspect of the present invention, a dielectric metasurface-based optical fiber metatip device is formed of a combination of nanobrick unit cells, one side of which is formed as a substrate of nanobrick unit cells, and the other side of nanobrick unit cells. a metasurface formed of nanobricks; an optical fiber connected to the center of one side of the metasurface and transmitting an input or output optical signal; and a fiber block surrounding the end of the optical fiber at the end of the optical fiber, connected to one side of the metasurface together with the optical fiber, and maintaining a connection state with the metasurface. The substrate is formed of silicon dioxide (SiO ₂ ), and the nanobricks are formed of hydrogenated amorphous silicon (a-Si:H).

In addition, the optical fiber metachip device is characterized in that the optical fiber metachip device is output as a vortex beam or a collimated beam according to the TE polarization (E-) or TM polarization (H-) of the optical signal input to the optical fiber.

In addition, the optical fiber metachip device characterized in that the phase profile for TE polarization (E-) or TM polarization (H-) of the nanobrick unit cell of the metasurface is calculated by the following formula.

및

은 각각 TE 및 TM에 대한 초점 거리이고, n은 주변 매체의 굴절률이며

은 소용돌이의 위상 전하를 의미하는 것임.Where (x, y) is the coordinates corresponding to the center of each unit cell relative to the center of the metasurface (MS) (when the center coordinates x ₀ , y ₀ , x=x ₀ -x ₁ , y= x ₀ -x ₁ ) and

and

are the focal lengths for TE and TM respectively, n is the refractive index of the surrounding medium and

represents the topological charge of the vortex.

In addition, the nano brick of the nano brick unit cell is formed in a bar shape, the height is 900 nm, the nano brick unit cell is formed in a square of 700 mm, and the horizontal and vertical length of the nano brick is in the range of 150 to 600 nm, It is characterized in that it is set according to the phase profile according to the position of the metasurface.

)각을 0 ~ 2π 범위로 변화하도록 제어하고, 입사광에 대한 전송 진폭(A_TE, A_TM) 비를 0~1범위로 제어하는 것을 특징으로 하는 광섬유 메타칩 장치.In addition, the optical fiber metachip device has a phase shift on the metasurface with respect to the input optical signal (

) Angle is controlled to change in the range of 0 to 2π, and the transmission amplitude (A _TE, A _TM ) ratio for incident light is controlled in the range of 0 to 1.

In addition, when an optical signal having a wavelength of λ = 1550 nm is input, the optical fiber metachip device outputs a vortex beam for TE polarized light (E-) and outputs a collimated beam for TM polarized light (H-). to be

In addition, the fiber optic metachip device is characterized in that the optical fiber is bonded to one side of the metasurface by epoxy, the substrate thickness of the nano-brick unit cell is 430 μm, and the adhesive thickness of the epoxy is characterized in that 30㎛.

In addition, the optical fiber metachip device is characterized in that transmission efficiency is 57% when an optical signal having a wavelength of λ = 1550 nm is input.

According to another aspect of the present invention, a data transmission system using a dielectric metasurface-based optical fiber metatip device includes a laser device for generating an input optical signal; a first optical fiber transmitting the pressure optical signal from the laser device; A first optical fiber meta tip device connected to the first optical fiber; a second fiber optic meta tip device having a predetermined distance from the first fiber optic meta tip device and installed so that the meta surface including the nano brick faces each other; a second optical fiber transmitting an output optical signal from the second optical fiber meta tip device and an optical receiver receiving an output optical signal transmitted from the second optical fiber and generating an output signal; Including, but the first fiber optic metachip device is formed by a combination of nano-brick unit cells, one side is formed of a substrate of nano-brick unit cells, and the other side is formed of nano-brick of nano-brick unit cells metasurface ; and c a fiber block surrounding the end of the first optical fiber at the end of the first optical fiber and maintaining a connection state with the metasurface, wherein the substrate is made of silicon dioxide (SiO ₂ ). formed, and the nanobricks are characterized in that they are formed of hydrogenated amorphous silicon (a-Si:H).

In addition, further comprising a polarizer for controlling polarization between the first fiber optic meta tip device and the second fiber optic meta tip device, and controlling on / off of data transmission according to the polarization control of the polarizer characterized by

In addition, the data transmission system is characterized in that an “on” signal is transmitted for the TM polarization of the input optical signal, and an “off” signal is transmitted for the TM polarization of the input optical signal.

In addition, the data transmission system includes an electro-optical modulator electrically connected to a polarization controller and a signal generator to the laser device and the first optical fiber meta tip device, and the signal generator includes the laser It is characterized in that data is transmitted by modulating an optical signal generated from a device, and on/off control is performed according to TE and TM polarization by the polarization controller.

In addition, the data transmission system is characterized in that extinction ratios for data rates in the range of 1 to 5 Gbps are 9 to 11 dB.

According to another aspect of the present invention, a method of manufacturing a fiber optic metachip device, a) preparing a substrate made of SiO ₂ material; b) depositing a hydrogenated amorphous silicon layer on the front surface of the substrate by a plasma enhanced chemical vapor deposition (PECVD) method; c) a first spin coating step of forming a first resist layer on the hydrogenated amorphous silicon layer; d) forming a first resist pattern layer corresponding to a metasurface pattern established on the first resist layer through an electron beam lithography process; e) forming an Al layer by depositing Al on the top surface of the first resist pattern layer and on the concave groove; f) lifting and removing all of the first resist pattern layer protruding from the top of the substrate using a lift-off solvent, and forming a patterned Al layer on the front surface of the substrate with the Al layer remaining in the concave groove portion; ; g) etching a hydrogenated amorphous silicon layer on the front surface of the substrate with the set metasurface pattern using the patterned Al layer as a hard mask; h) forming a metasurface by removing the patterned Al layer remaining at the end of the hydrogenated amorphous silicon layer on the front surface after the etching step; i) mounting a fiber block on an end of an optical fiber; and j) aligning the center of the formed metasurface substrate to coincide with the end of the optical fiber to which the fiber block is mounted, and bonding the metasurface substrate and the fiber block with UV curable epoxy; It is characterized in that it includes.

In an embodiment of the present invention, a dielectric metasurface arranged in a specific pattern of unit cells is connected to a single-mode optical fiber for optical control of dual functions including generating a vortex beam and a collimated beam. meta-tip, FMT) device.

In the optical fiber meta-tip (FMT) device configured by connecting to a single-mode optical fiber according to an embodiment of the present invention, distinct light control operations including generation of vortex beams and collimated beams include transverse electric polarization and transverse magnetic This can be done by adjusting the phase profile encoded in the metasurface for polarization.

In addition, in the optical fiber meta-tip (FMT) device configured by connecting to a single-mode optical fiber according to an embodiment of the present invention, first, a polarization selection metasurface is manufactured through lithography nano-manufacturing, and then, As a customized vision system, it can be attached to the optical fiber by giving an interval considering the focal interval. In addition, an optical fiber meta-tip (FMT) device according to an embodiment of the present invention may be applied as an application device such as optical interconnection.

In addition, an optical fiber meta-tip (FMT) device according to an embodiment of the present invention can be applied to lab-on-fiber technology for applications such as optical communication, optical trapping, and biological sensing. .

In addition, an optical fiber meta-tip (FMT) device according to an embodiment of the present invention can promote various lighting control and functional diversity by utilizing the integration of a multifunctional metasurface and an optical fiber. This could build a promising bridge between existing fiber optic technologies and new "flat" optics and photonics.

In one embodiment of the present invention, we provide a theoretical analysis of a new optical fiber meta-tip (FMT) that integrates a dual-functional dielectric meta-surface (MS) in a single-mode fiber (SMF), This theoretical analysis can enable various lighting manipulations and communication controls including vortex beam generation and beam collimation.

In addition, an optical fiber meta-tip (FMT) device according to an embodiment of the present invention is an efficient polarization selective type in which a pair of optical fiber meta-tips (FMT) are combined to pursue potential applications for data transmission. Optical interconnection can be established. In addition, the nanobricks of the sub-wavelength elements constituting the metasurface (MS) included in the optical fiber meta-tip (FMT) device according to an embodiment of the present invention are designed in a rectangular shape and have a transverse electric field ( TE) and transverse magnetic field (TM) polarization. In addition, a sufficiently high transmission efficiency can be obtained due to the low optical loss of the dielectric material.

)의 변화를 도시한 것이다.
도 6은 본 발명의 일 실시 예에 따른 광섬유 메타팁(optical fiber meta-tip, FMT) 장치의 메타표면을 구성하는 나노브릭 유닛셀의 나노브릭의 가로(w)와 세로(l) 길이에 따른 입사광에 대한 TE 편광빔의 전송 진폭(A_TE) 변화를 도시한 것이다.
도 7은 본 발명의 일 실시 예에 따른 광섬유 메타팁(FMT) 장치의 메타표면을 구성하는 나노브릭 유닛셀의 나노브릭의 가로(w)와 세로(l) 길이에 따른 TM 편광 빔의 위상 편이(

)의 변화를 도시한 것이다.
도 8은 본 발명의 일 실시 예에 따른 광섬유 메타팁(FMT) 장치의 메타표면을 구성하는 나노브릭 유닛셀의 나노브릭의 가로(w)와 세로(l) 길이에 따른 입사광에 대한 TM 편광빔의 전송 진폭(A_TM) 변화를 도시한 것이다.
도 9는 본 발명의 일 실시 예에 따른 광섬유 메타팁 장치의 선택된 나노브릭 유닛셀에서 TE 편광에 대한 전기장(E-) 필드 및 자기장(H-) 필드 프로파일을 도시한 것이다.
도 10은 본 발명의 일 실시 예에 따른 광섬유 메타팁(optical fiber meta-tip, FMT) 장치의 메타표면의 선택된 나노브릭 유닛셀에서 TM 편광에 대한 E- 필드 및 H- 필드 프로파일을 도시한 것이다.
도 11은 본 발명의 일 실시 예에 따른 메타팁(FMT) 장치에서 편광 맞춤형 위상 프로파일을 도시한 것이다.
도 12는 본 발명의 일 실시 예에 따른 메타팁(FMT) 장치에 입사되는 TE- 및 TM 편광에 응답하여 메타표면의 제1 전방(z= 200㎛)의 yz- 평면에 있는 E_X 장 강도 분포를 도시한 것이다.
도 13은 본 발명의 일 실시 예에 따른 메타팁(FMT) 장치에 입사되는 TE- 및 TM 편광에 응답하여 메타표면의 제2 전방(z= 315㎛)의 yz- 평면에 있는 E_y 장 강도 분포를 도시한 것이다.
도 14는 본 발명의 일 실시 예에 따른 광섬유 메타팁(FMT) 장치의 광 출력 특성의 테스트를 위한 측정 시스템을 도시한 것이다.
도 15는 도 14의 시스템으로부터 본 발명의 일 실시 예에 따른 광섬유 메타팁(optical fiber meta-tip, FMT) 장치 제1 샘플의 측정된 이미지의 yz 평면의 TE 편광에 대한 광 강도 분포를 나타낸다.
도 16은 본 발명의 일 실시 예에서는 소용돌이빔(vortex beam)의 특성의 분석을 위해 광학 축(z)을 따라 이미징 시스템을 100㎛ 단위로 이동하여 일련의 이미지를 연속적으로 측정한 것이다.
도 17은 본 발명의 일 실시 예에 따른 광섬유 메타팁(FMT) 제1샘플 장치에서 TM 편광에 대한 yz- 및 xy- 평면에서 측정된 광 강도 프로파일을 도시한 것이다.
도 18은 본 발명의 일 실시 예에 따른 광섬유 메타팁(FMT) 제1샘플 장치에서 TM 편광에 대해 z = 9mm에서 측정된 시준된 빔 프로파일을 도시한 것이다.
도 19는 본 발명의 일 실시 예에 따른 광섬유 메타팁(FMT) 제1샘플 장치에서 메티표면을 제거한 상태에서 TM 편광에 대한 yz- 및 xy- 평면에서 측정된 광 강도 프로파일을 도시한 것이다.
도 20은 발명의 일 실시 예에 따른 광섬유 메타팁 장치를 이용한 데이터 전송시스템을 간략한 구조를 도시한 것이다.
도 21은 본 발명의 일 실시 예에 따른 광섬유 메타팁 장치를 이용한 데이터 전송시스템에 광학펄스를 송신하여 수신된 광신호를 도시한 것이다.
도 22는 본 발명의 또 다른 실시 예에 따른 광섬유 메타팁 장치를 이용한 데이터 전송시스템에 대한 구조를 도시한 것이다.
도 23은 본 발명의 또 다른 실시 예에 따른 광섬유 메타팁 장치를 이용한 데이터 전송시스템에 의한 데이터 전송 속도에 따른 아이 패턴(eye pattern)을 도시한 것이다.
도 24는 도 23에서 전송된 1 ~ 5Gbps 범위의 데이터 속도에 대해 측정된 소광비(extinction ratios)을 도시한 것이다.
도 25는 본 발명의 일 실시 에에 따른 광섬유 메타팁 장치에서 유전체 메타표면의 제조 과정을 도시한 것이다.1 and 2 are structural diagrams for explaining the structure of an optical fiber meta-tip (FMT) device including a single-mode optical fiber according to an embodiment of the present invention.
3 is a second side surface of a metasurface 200 arranged in unit cells including nanobricks formed in a specific pattern in the case of an optical fiber meta-tip (FMT) device according to a preferred embodiment of the present invention. It shows a scanning electron microscope image of .
4 illustrates the structure of a nanobrick unit cell forming a metasurface of an optical fiber metatip (FMT) device according to an embodiment of the present invention.
5 is a phase of a TE polarized beam according to the horizontal (w) and vertical (l) lengths of nanobricks of a nanobrick unit cell of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention. side (

) is shown.
6 is a graph showing the horizontal (w) and vertical (l) lengths of nanobricks of nanobrick unit cells constituting the metasurface of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention. It shows the change in the transmission amplitude (A _TE ) of the TE polarized beam with respect to the incident light.
7 is a phase shift of a TM polarized beam according to the horizontal (w) and vertical (l) lengths of nanobricks of nanobrick unit cells constituting the metasurface of a fiber optic metatip (FMT) device according to an embodiment of the present invention. (

) is shown.
8 is a TM polarized beam for incident light according to the horizontal (w) and vertical (l) lengths of the nanobricks of the nanobrick unit cells constituting the metasurface of the fiber optic metatip (FMT) device according to an embodiment of the present invention. It shows the change in the transmission amplitude (A _TM ) of
9 illustrates electric (E-) field and magnetic (H-) field profiles for TE polarization in a selected nanobrick unit cell of an optical fiber metatip device according to an embodiment of the present invention.
10 illustrates E-field and H-field profiles for TM polarization in selected nanobrick unit cells of the metasurface of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention. .
11 illustrates a polarization tailored phase profile in a meta tip (FMT) device according to an embodiment of the present invention.
12 is an E _X field intensity in the yz-plane of the first front (z = 200 μm) of the metasurface in response to TE- and TM polarization incident on the metatip (FMT) device according to an embodiment of the present invention. distribution is shown.
13 is an E _y field intensity in the yz- plane of the second front (z = 315 μm) of the metasurface in response to TE- and TM polarization incident on the metatip (FMT) device according to an embodiment of the present invention. distribution is shown.
14 illustrates a measurement system for testing light output characteristics of a fiber optic metatip (FMT) device according to an embodiment of the present invention.
FIG. 15 shows a light intensity distribution for TE polarization in a yz plane of a measured image of a first sample of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention from the system of FIG. 14 .
FIG. 16 shows a series of images continuously measured by moving the imaging system in units of 100 μm along the optical axis z for analyzing characteristics of a vortex beam according to an embodiment of the present invention.
17 illustrates light intensity profiles measured in yz- and xy-planes for TM polarization in a first sample device of an optical fiber metatip (FMT) according to an embodiment of the present invention.
18 illustrates a collimated beam profile measured at z = 9 mm for TM polarization in a first sample device of a fiber optic metatip (FMT) according to an embodiment of the present invention.
FIG. 19 illustrates light intensity profiles measured in yz- and xy-planes for TM polarized light in a state in which the MET surface is removed from a first sample device of a fiber optic meta tip (FMT) according to an embodiment of the present invention.
20 shows a simple structure of a data transmission system using an optical fiber meta tip device according to an embodiment of the present invention.
21 illustrates an optical signal received by transmitting an optical pulse to a data transmission system using an optical fiber metatip device according to an embodiment of the present invention.
22 shows the structure of a data transmission system using an optical fiber meta tip device according to another embodiment of the present invention.
23 illustrates an eye pattern according to a data transmission rate by a data transmission system using an optical fiber metatip device according to another embodiment of the present invention.
FIG. 24 shows measured extinction ratios for data rates in the range of 1 to 5 Gbps transmitted in FIG. 23 .
25 illustrates a manufacturing process of a dielectric metasurface in an optical fiber metatip device according to an embodiment of the present invention.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

In addition, terms such as "...unit", "...unit", "module", and "device" described in the specification mean a unit that processes at least one function or operation, which is hardware or software, or a combination of hardware and software. can be implemented as

Also, terms such as first and second may be used in describing components of an embodiment of the present invention. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term. When an element is described as being 'connected', 'coupled' or 'connected' to another element, the element may be directly connected, coupled or connected to the other element, but not between the element and the other element. It should be understood that another component may be 'connected', 'coupled' or 'connected' between elements.

Hereinafter, an optical fiber metatip device based on a dielectric metasurface capable of generating a vortex beam and a collimated beam according to an embodiment of the present invention will be described in detail.

Small multifunctional metasurfaces that facilitate simultaneous operation are an important research challenge for integrated optical modules and systems due to their potential to realize multifocal metalenses, holograms, vortex beam generation, and various beam manipulations. .

Among the studies on this, it has been reported that within the framework, a 'lab-on-fiber' paradigm can envision an optical fiber platform integrated with nanostructured photonic and/or plasmonic materials capable of controlling light at the nanoscale. This has the advantage of being able to pursue the ultra-small 'all-in-fiber' function that can destructively expand the function of the existing optical fiber. In addition, several fabrication processes have been developed to process anomalous substrates such as fiber tips for optical processing, environmental and life sciences, home security, etc., resulting in multifunctional and multi-response nanoprobes for applications such as fiber optic tweezers, in vivo single molecule imaging, etc. realization became possible.

Plasmon-based fiber metatips (FMTs) may have limited light manipulation efficiency due to the inherent ohmic loss of metal structures, but “Lab-on-fiber” technology, which combines the inherent advantages of optical fibers with nanophotonic platforms, is It was analyzed to have an improved ability to control light at the nanoscale, which greatly improved its function.

Integrating metasurfaces with fiber optic technology is a strategically important endeavor.

In an embodiment of the present invention, a dielectric metasurface arranged in a specific pattern of unit cells is connected to a single-mode optical fiber for optical control of dual functions including generating a vortex beam and a collimated beam. meta-tip, FMT) device.

In this specification, polarization refers to a phenomenon in which electric and magnetic fields constituting light vibrate in a specific direction when electromagnetic waves propagate. TE (Transverse Electric Field) polarization means vertical polarization in which the electric field vibration direction is perpendicular to the incident plane, and TM (Transverse Magnetic Field) polarization means horizontal polarization in which the electric field vibration direction is parallel to the incident plane.

In the optical fiber meta-tip (FMT) device configured by connecting to a single-mode optical fiber according to an embodiment of the present invention, distinct light control operations including generation of vortex beams and collimated beams include transverse electric polarization and transverse magnetic This can be done by adjusting the phase profile encoded in the metasurface for polarization.

In addition, in the optical fiber meta-tip (FMT) device configured by connecting to a single-mode optical fiber according to an embodiment of the present invention, first, a polarization selection metasurface is manufactured through lithography nano-manufacturing, and then, As a customized vision system, it can be attached to the optical fiber by giving an interval considering the focal interval. In addition, an optical fiber meta-tip (FMT) device according to an embodiment of the present invention may be applied as an application device such as optical interconnection.

In addition, an optical fiber meta-tip (FMT) device according to an embodiment of the present invention can be applied to lab-on-fiber technology for applications such as optical communication, optical trapping, and biological sensing. .

In addition, an optical fiber meta-tip (FMT) device according to an embodiment of the present invention can promote various lighting control and functional diversity by utilizing the integration of a multifunctional metasurface and an optical fiber. This could build a promising bridge between existing fiber optic technologies and new "flat" optics and photonics.

In one embodiment of the present invention, we provide a theoretical analysis of a new optical fiber meta-tip (FMT) that integrates a dual-functional dielectric meta-surface (MS) in a single-mode fiber (SMF), This theoretical analysis can enable a variety of lighting manipulations including vortex beam generation and beam collimation.

In addition, an optical fiber meta-tip (FMT) device according to an embodiment of the present invention is an efficient polarization selective type in which a pair of optical fiber meta-tips (FMT) are combined to pursue potential applications for data transmission. Optical interconnection can be established. In addition, the nanobricks of the sub-wavelength elements constituting the metasurface (MS) included in the optical fiber meta-tip (FMT) device according to an embodiment of the present invention are designed in a rectangular shape and have a transverse electric field ( TE) and transverse magnetic field (TM) polarization. In addition, a sufficiently high transmission efficiency can be obtained due to the low optical loss of the dielectric material.

1 and 2 are structural diagrams for explaining the structure of an optical fiber meta-tip (FMT) device including a single-mode optical fiber according to an embodiment of the present invention.

Referring to FIG. 1, an optical fiber meta-tip (FMT) device 10 including a single-mode optical fiber according to an embodiment of the present invention includes an optical fiber 110 through which an input or output optical signal is transmitted, a center It is connected to the end of the optical fiber 100 and includes a metasurface 200 formed by a combination of nano-brick unit cells.

In addition, the end of the optical fiber 110 surrounds the end of the optical fiber 110, is connected to one side of the metasurface together with the optical fiber, and guides the optical fiber and maintains the connection state. (fiber block, 120) is further included.

The metasurface according to an embodiment of the present invention is characterized in that one side is formed of a substrate of nano-brick unit cells and the other side is formed of nano bricks of nano-brick unit cells.

The fiber block 120 surrounds the outside of the end of the optical fiber 110, the end surface is aligned with the end surface of the optical fiber, and the first surface of the flat substrate 210 of the metasurface 200 It is attached to the side surface of the substrate by means of an adhesive.

The second side of the flat substrate 210 of the metasurface 200 is formed by a combination of unit cells 250 including nanobricks arranged in a specific pattern.

1 and 2 show an SMF (single-mode fiber) connected to a first metasurface 200 formed by a combination of unit cells including dielectric nanobricks made of hydrogenated amorphous silicon (a-Si: H). ) Represents the structure of an optical fiber meta-tip (FMT) device including a.

1 and 2, the TE- and TM-polarized light beams from the input light (λ = 1550 nm) emitted from the end surface of the single-mode optical fiber (SMF) generate an electric field (E-) by the first metasurface 200. is parsed as output oriented along the x-axis and y-axis.

Among the TE- and TM-polarized light beams from the input light (λ = 1550 nm) in the optical fiber meta-tip (FMT) device according to an embodiment of the present invention, in the case of TE, the phase charge is l ₀ = +15, a collimated beam is obtained for the TM case, whereas a divergent vortex beam is obtained.

The metasurface of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention performs functions of a convex lens and an optical vortex phase plate.

An optical fiber meta-tip (FMT) device according to an embodiment of the present invention can realize focused vortex and beam collimation by adjusting the phase profile encoded on the metasurface for transverse electric polarization and transverse magnetic polarization. can

Therefore, the sharp contrast between the collimated beam and the highly charged divergent vortex beam in the optical fiber meta-tip (FMT) device according to an embodiment of the present invention is considered to have a characteristic function in polarization selective optical interconnection. analyzed

According to an embodiment of the present invention, a beam generated from a single-mode optical fiber (SMF) may be modeled as a Gaussian profile representing a divergence angle θ. In addition, the effective area of the first metasurface 200 for a given divergence angle of the single-mode optical fiber (SMF) may be determined according to the thickness of the substrate.

Referring to FIG. 2, in the case of an optical fiber meta-tip (FMT) device according to a preferred embodiment of the present invention, the foot print of the meta-surface 200 is a disc having a diameter of d = 85 μm. was made with

3 is a second side surface of a metasurface 200 arranged in unit cells including nanobricks formed in a specific pattern in the case of an optical fiber meta-tip (FMT) device according to a preferred embodiment of the present invention. It shows a scanning electron microscope image of .

Referring to FIG. 3 , the metasurface 200 of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention is a nanobrick unit cell 250 having a specific pattern for vortex and beam collimation. ) is formed by a combination of

4 illustrates the structure of a nanobrick unit cell forming a metasurface of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention.

Referring to FIG. 4, the nanobrick unit cell 250 according to an embodiment of the present invention is made of SiO ₂ formed It is formed as a vertical square pillar of a certain height (h) at the center of the upper part of the square substrate, and the cross section includes nanobricks formed of horizontal and vertical (w, l) square faces having a direction corresponding to the xy direction of the square substrate. do.

The nano-brick of the nano-brick unit cell 250 according to an embodiment of the present invention is formed in a columnar shape, made of hydrogenated amorphous silicon (a-Si:H), and for vortexing and beam collimation for input light. The horizontal and vertical (w, l) lengths are arranged in a specified size so that the function is performed.

에 해당하는 900nm로 형성되었다. 또한, 나노브릭의 가로(w)와 세로(l) 길이는 150 ~ 600nm 범위에서 요구되는 위상 프로파일 특성에 따라 각각 특정된 크기로 형성된다. 또한, 나노브릭 유닛셀(250)은 정사각형으로 Λ = 700nm의 동일한 피치로 형성된다.In the case of a nanobrick unit cell constituting the metasurface of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention, the height (h) of the nanobrick is about 0.58 of the input light wavelength.

was formed at 900 nm corresponding to In addition, the horizontal (w) and vertical (l) lengths of the nanobricks are each formed to a specific size according to phase profile characteristics required in the range of 150 to 600 nm. In addition, the nanobrick unit cells 250 are formed in a square shape with the same pitch of Λ = 700 nm.

)의 변화를 도시한 것이다.5 is a phase of a TE polarized beam according to the horizontal (w) and vertical (l) lengths of nanobricks of a nanobrick unit cell of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention. side (

) is shown.

6 is a graph showing the horizontal (w) and vertical (l) lengths of nanobricks of nanobrick unit cells constituting the metasurface of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention. It shows the change in the transmission amplitude (A _TE ) of the TE polarized beam with respect to the incident light.

)의 변화를 도시한 것이다.7 is a phase shift of a TM polarized beam according to the horizontal (w) and vertical (l) lengths of nanobricks of nanobrick unit cells constituting the metasurface of a fiber optic metatip (FMT) device according to an embodiment of the present invention. (

) is shown.

8 is a TM polarized beam for incident light according to the horizontal (w) and vertical (l) lengths of the nanobricks of the nanobrick unit cells constituting the metasurface of the fiber optic metatip (FMT) device according to an embodiment of the present invention. It shows the change in the transmission amplitude (A _TM ) of

Simulation of the phase characteristics of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention was performed using FDTD Solutions (Lumerical, Canada), a commercially available finite-difference time-domain tool. .

) 및 전송 진폭(A _TE)이 각각 도 4, 5와 같이 w 및 l의 함수로 표시될 수 있다.5 and 6, in the case of an incident TE polarized plane wave, the accumulated phase shift (

) and transmission amplitude ( A _TE ) can be expressed as functions of w and l as shown in FIGS. 4 and 5, respectively.

Meanwhile, the phase delay and amplitude characteristics of the incident TM polarized beam can be expressed by folding the dotted lines in FIGS. 4 and 5 as reference lines.

및 전송 진폭 A _TM은 각각 도 6, 7과 같이 w 및 l의 함수로 표시될 수 있다.7 and 8, in the case of an incident TM polarized plane wave, the accumulated phase shift

and transmission amplitude A _TM can be expressed as a function of w and l as shown in FIGS. 6 and 7, respectively.

,

) 각을 0 ~ 2π 범위로 변화하도록 제어하고, 입사광에 대한 전송 진폭(A_TE, A_TM) 비를 0~1범위로 제어할 수 있다.An optical fiber meta-tip (FMT) device according to an embodiment of the present invention selectively selects the horizontal width (w) and vertical length (l) of nanobrick unit cells to have desired phase shift and transmission amplitude characteristics. It is characterized in that the array is applied by applying. According to an embodiment of the present invention, the phase shift (

,

) angle can be controlled to change in the range of 0 to 2π, and the ratio of transmission amplitude (A _TE, A _TM ) to incident light can be controlled in the range of 0 to 1.

It is analyzed that full 2*?* phase control is possible due to the high refractive index difference between a-Si: H, the dielectric material of nanobricks, and air. Accordingly, in an embodiment of the present invention, 64 nano-brick unit cells capable of providing sufficiently high transmittance and 8-step 2π phase shift are selectively arranged based on the minimum Euclidean distance between the target and the realized phase in the phase domain. It is characterized by being composed of

9 illustrates electric (E-) field and magnetic (H-) field profiles for TE polarization in a selected nanobrick unit cell of an optical fiber metatip device according to an embodiment of the present invention.

10 illustrates E-field and H-field profiles for TM polarization in selected nanobrick unit cells of the metasurface of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention. .

9 and 10 are E- for TE polarization and TM polarization observed in selected nanobrick unit cells (w = 348 nm and l = 209 nm, which are marked with stars in FIGS. 5, 6, 7, and 8). Field and H-field profiles are shown.

The operating wavelength of the phase characteristic simulations of FIGS. 5 to 10 is 1550 nm.

Referring to FIGS. 9 and 10 , it is analyzed that the spiral electric field and enhanced magnetic field distribution in the cross section of the nanobrick unit cell occurs when the incident light is TE polarized light or TM polarized light, as shown in FIGS. 9 and 10 .

In addition, it is analyzed that the difference in electromagnetic response for the two polarizations in the unit cell including the nanobrick of a-Si:H material results in the resonant nanobrick exhibiting a distinct phase shift.

As shown in Figs. 9 and 10, vortex-like E-field and reinforced H-field profiles are observed at the cross-section of the nanobrick unit cell in response to both TE- and TM-polarized incident light rays. can be observed. Therefore, the simulation results indicate that the nanobrick unit cell can generate different electromagnetic responses for the two polarizations. As a result, it is analyzed that the phase profile encoded by the metasurface according to an embodiment of the present invention can be adjusted according to polarization.

An optical fiber meta-tip (FMT) device according to an embodiment of the present invention can facilitate manipulation of a polarization control beam through numerical simulation of the horizontal (w) and vertical (l) lengths of nanobricks. . According to an embodiment of the present invention, a metasurface serving as a convex lens converges a collimated plane wave to a focal point. Conversely, if the end face of the optical fiber corresponds to the focal plane of the metasurface of the convex lens, the outgoing beam can be collimated with the metasurface. Otherwise, the beam diverges greatly. Beam collimation depends on the relative focal length in the gap between the fiber and the metasurface.

In addition, the metasurface of the fiber optic metatip (FMT) device according to an embodiment of the present invention further imposes a spiral phase profile function so that the beam can induce orbital angular momentum.

In the metatip (FMT) device according to an embodiment of the present invention, the desired phase profile for TE and TM polarization can be expressed by the following equation.

및

은 각각 TE 및 TM에 대한 초점 거리이고, n은 주변 매체의 굴절률이며

은 소용돌이의 위상 전하를 나타낸다.Where (x, y) is the coordinates corresponding to the center of each unit cell relative to the center of the metasurface (MS) (when the center coordinates x ₀ , y ₀ , x=x ₀ -x ₁ , y= x ₀ -x ₁ ) and

and

are the focal lengths for TE and TM respectively, n is the refractive index of the surrounding medium and

represents the topological charge of the vortex.

11 illustrates a polarization tailored phase profile in a meta tip (FMT) device according to an embodiment of the present invention.

= 200㎛,

= +15 나타내는 집중된 소용돌이 및 b)

= 315 ㎛를 나타내는 광 포커싱을 얻기 위해 계산된 위상 프로파일에 나타낸다. 11 is a) in a meta tip (FMT) device according to an embodiment of the present invention

= 200 μm,

= +15 indicating concentrated eddies and b)

= 315 μm is shown in the calculated phase profile to obtain an optical focusing.

12 is an E _X field intensity in the yz-plane of the first front (z = 200 μm) of the metasurface in response to TE- and TM polarization incident on the metatip (FMT) device according to an embodiment of the present invention. distribution is shown.

13 is an E _y field intensity in the yz- plane of the second front (z = 315 μm) of the metasurface in response to TE- and TM polarization incident on the metatip (FMT) device according to an embodiment of the present invention. distribution is shown.

According to an embodiment of the present invention, when illuminating a collimated beam at a designated wavelength of 1550 nm, polarization dependent electric field intensity distributions in the yz- and xy- planes in front of the metasurface (MS) as shown in FIGS. 11 to 13 From this, the characteristics of the function of vortex generation and light focusing can be found.

Therefore, in the metatip (FMT) device according to an embodiment of the present invention, the metasurface converts the light emitted from the end surface of the optical fiber into a divergent vortex beam for TE and TM polarization, respectively, and a collimated parallel beam along the central axis. do

In addition, in the metatip (FMT) device according to an embodiment of the present invention, the thickness of the substrate of the nanobrick unit cell has a divergence characteristic of the beam generated while propagating from the end surface of the single-mode optical fiber (SMF) to the metasurface. intervals can be determined.

460㎛의 간격으로 형성되었다. 이 간격의 크기는 공기 대신 기판 재료인 고 굴절률 이산화규소(SiO₂)로 대체하여 결정된다.In the fiber optic metatip (FMT) device according to an embodiment of the present invention, the distance between the end face of the optical fiber and the front face of the metasurface is

It was formed at intervals of 460 μm. The size of this gap is determined by replacing air with high refractive index silicon dioxide (SiO ₂ ) as the substrate material.

)= 1.44) 제조되었으며, 광섬유 끝 면과 메타표면 전면 사이는 입력 파장(λ= 1550 nm)을 고려하여 기판 430㎛ 두께 및 접착용 에폭시 두께 30㎛가 포함하여 형성된다.In the meta tip (FMT) device according to an embodiment of the present invention, the substrate of the nanobrick unit cell is a quartz substrate (refractive index (

) = 1.44), and the space between the end face of the optical fiber and the front surface of the metasurface is formed by including a substrate of 430 μm thickness and an adhesive epoxy thickness of 30 μm in consideration of the input wavelength (λ = 1550 nm).

1 and 2, the fiber block 120 surrounding the end of the optical fiber in the fiber optic metatip (FMT) device according to an embodiment of the present invention is connected to the end face of the optical fiber and the metasurface due to the expanded contact area. It is easy to assemble and can stably maintain the device.

In the manufacturing process of the fiber optic metatip (FMT) device according to an embodiment of the present invention, the metasurface was firmly fixed using a holder, and the fiber block (length: 3.3mm, width: 10.5mm, height: 2.0mm) was powered by power. It was fixed with a vacuum mount above the translation stage. A single-mode optical fiber (SMF) was prepared with a length of 50 cm. Finally, the metasurface substrate with a footprint of ~ 2 cm ² was bonded to the fiber block with UV curable epoxy.

14 illustrates a measurement system for testing light output characteristics of a fiber optic metatip (FMT) device according to an embodiment of the present invention.

Referring to FIG. 14, the light source is an optical fiber meta-tip (FMT) according to an embodiment of the present invention using a distributed feedback laser (M-TECH, MSMT-10A) outputting a light beam with a wavelength of 1550 nm. The device was irradiated, and the output light beam passed was a shortwave infrared camera (AVAL DATA, ABA-001IR) equipped with a 10×/20× objective lens (SEIWA OPTICAL, PEIR-Plan-10) × / Mitutoyo, 20 × Plan Apo NIR ) and monitored the beam profile through the connected computer.

In addition, polarization-selective dual functions including vortex generation and beam collimation were measured using a linear polarizer (Thorlabs, LPNIR050-MP2).

In addition, a series of images (intensity distribution in the xy plane) was measured by translating the imaging system along the optical axis (z-axis) in increments of 5 μm.

In the optical fiber metatip device manufactured as the first sample according to an embodiment of the present invention, the arrangement of nanobrick unit cells on the metasurface is each nanobrick unit to have divergence for TE polarized light and collimated beam formation for TM polarized light. It shows the width and height of the cell.

및 전송 진폭 A_TE, A_TM, 으로부터 각각 가로(w), 세로(l)의 길이를 결정한다.Each nanobrick unit cell arranged on the metasurface has a phase shift of FIGS. 5, 6, 7, and 8 according to the phase profile set according to the required characteristics.

And the horizontal (w) and vertical (l) lengths are determined from transmission amplitudes A _TE , A _TM , respectively.

Table 1 selects a total of 64 nanobricks formed from the center of the metasurface that can provide a sufficiently high transmittance and an 8-step 2π phase shift based on the minimum Euclidean distance between the target and the realized phase in the phase domain. it is composed

FIG. 15 shows a light intensity distribution for TE polarization in a yz plane of a measured image of a first sample of an optical fiber meta-tip (FMT) device according to an embodiment of the present invention from the system of FIG. 14 .

In FIG. 15, the input angle (θ) input from the end face of the optical fiber to the metasurface is 16°.

Referring to FIG. 15 , the light intensity distribution of the TE polarized light in the yz plane corresponding to the center appears in a diverging form.

와 일치하지 않는다. 결과적으로 제1샘플의 메타표면은 입사광의 TE 편광에 대해 시준하지 못하고 발산 소용돌이빔을 생성하게 된다.The substrate thickness of the first sample device of an optical fiber meta-tip (FMT) according to an embodiment of the present invention is the focal length

does not match As a result, the metasurface of the first sample fails to collimate the TE polarization of the incident light and generates a diverging vortex beam.

16 shows the spatial intensity distribution observed in the yz plane at different positions along the z axis for Sample 1.

FIG. 16 shows a series of images continuously measured by transforming the imaging system in units of 100 μm along the optical axis (z) in order to analyze the characteristics of a vortex beam in an embodiment of the present invention.

The spiral pattern in Fig. 16 may be due to the interference between the divergent optical vortex and the unwanted incoming light, which is presumably larger than the footprint of the metasurface (MS) of the fabricated sample 1. The number of interference fringes corresponding to the generated optical vortex was calculated as 15 as intended. In the case of TM polarization in the sample 1 device, it is analyzed that it serves as a small beam collimator.

15 and 16, the light intensity distribution for TE polarization in the first sample device of the optical fiber metatip according to an embodiment of the present invention is a vortex beam with a topological charge l ₀ = 15 was measured to be generated, and the MET surface was analyzed to play the role of a convex lens and an optical vortex phase plate. The transmission efficiency measured in FIGS. 15 and 16 was ~57%.

17 illustrates light intensity profiles measured in yz- and xy-planes for TM polarization in a first sample device of an optical fiber metatip (FMT) according to an embodiment of the present invention.

18 illustrates a collimated beam profile measured at z = 9 mm for TM polarization in a first sample device of a fiber optic metatip (FMT) according to an embodiment of the present invention.

In FIG. 18, a shows the intensity distribution captured in the xy plane, and b shows the intensity distribution measured along the x and y axes.

Referring to Figs. 17 and 18, a fiber optic metatip device established within a distance of ~10 mm from the metasurface (MS) is shown to efficiently collimate a diverging Gaussian-like beam emanating from an optical fiber to produce a well-defined symmetric far-field pattern. analyzed

FIG. 19 illustrates light intensity profiles measured in yz- and xy-planes for TM polarized light in a state in which the MET surface is removed from a first sample device of a fiber optic meta tip (FMT) according to an embodiment of the present invention.

Referring to FIG. 19, it can be seen that in the device without the MET surface, the light beam for TM polarization is rapidly diffused.

d= 85㎛ 및 w2 = 452㎛)를 참조하여 측정하였다. 시준된 빔의 발산각은 θ_div.

2.1°였다.17 and 18, the divergence angle (θ _div ) of the collimated beam is the beam width (w1) at different positions, including z1 = 0 mm and z2 = 10 mm.

d = 85 μm and w2 = 452 μm). The divergence angle of the collimated beam is θ _div .

It was 2.1°.

57%로 측정되었다.In addition, the transmission efficiency of the optical fiber metatip device, which is defined as the ratio of transmitted light power to normalized incident power for each target polarization according to an embodiment of the present invention, for both TE and TM polarizations

measured at 57%.

The associated insertion loss can be accounted for by the Fresnel loss associated with interfaces including fiber, epoxy, SiO ₂ and air.

According to an embodiment of the present invention, it was analyzed that the change in the distance between the end surface of the optical fiber and the metasurface (MS) has a direct effect on the divergence. Accordingly, beam collimation can be controlled by adjusting the thickness of the metasurface (MS) substrate and the thickness of the epoxy.

The optical fiber metatip device according to an embodiment of the present invention enables the development of optical trapping, optical measurement, optical processor, and optical communication, considering prominent features such as polarization mediating function, miniaturized spatial area, and improved optical throughput. expected to do

In one embodiment of the present invention, as shown in FIG. 14, the transmission efficiency of the implemented fiber optic metatip (FMT) device, which is defined as the ratio of transmitted light power to normalized incident power for each target polarization, is measured using a polarization controller and a polarizer. did

For TE-polarized light, the measurement procedure is summarized as follows.

i) Referring to the alignment mark engraved on the metasurface (MS), set the polarizer to the target polarization.

ii) monitor the transmitted beam profile and manipulate the polarization controller to maximize the observed optical vortex intensity.

iii) Using a photodiode power sensor (Thorlabs, S132C), the transmitted light power of the FMT (P _TE - _out ) is measured.

iv) Replace the fiber optic metatip (FMT) device with a bare fiber block with the metasurface removed in the same polarization state.

v) Measure the output optical power of the fiber block (P _TE-in ).

vi) The resulting transmission efficiency for TE-polarized light is obtained from P _TE - _out /P _TE-in .

In addition, the numerical simulation of the fiber optic meta tip (FMT) device according to an embodiment of the present invention was calculated as follows.

i) To characterize the nanobrick unit cell (UC) using the FDTD solution, the amplitude and phase contour maps shown in Figs. It is calculated by scanning the cross-sectional dimensions.

Periodic boundary conditions were applied along the x- and y-axes, while perfectly matched layer (PML) boundary conditions were applied along the z-axis. The unit cell UC was illuminated with a plane wave source of λ = 1550 nm.

80000 나노브릭으로 구성된 메타표면(MS)이 스크립트를 통해 가상으로 구성된다.ii) for the simulation of the polarization control dual function metasurface (MS), with the horizontal, vertical length and height respectively designed

A metasurface (MS) composed of 80000 nanobricks is virtually constructed through a script.

PML boundary conditions are set along the x, y, and z axes. The computational domain is set equal to 200 μm along the x-axis and y-axis and 10 μm along the z-axis to cover the enlarged metasurface (MS) with a diameter d = 200 μm.

A full-field scattering field source for the input light (λ = 1550 nm) is used to feed the MS from the SiO ₂ side. The far-field intensity distributions depicted in Figs. 12 and 13 were obtained using script commands based on the surface equivalence theorem provided by the FDTD simulation tool.

iii) In the case of simulation related to the fiber optic metatip device (FMT) according to an embodiment of the present invention, the core and cladding of the used optical fiber (model SMF-28) have refractive indices of 1.449 and 1.444 and diameters of 8.2 and 125 μm, respectively. It was made with eggplant.

The distance between the end face of the optical fiber and the metasurface was fixed at 460 μm including the thickness of the quartz substrate. Periodic boundary conditions are applied along the y-axis, while perfectly matched layer (PML) boundary conditions are imposed along the x- and z-axes.

20 shows a simple structure of a data transmission system using an optical fiber meta tip device according to an embodiment of the present invention.

Referring to FIG. 20, a data transmission system using an optical fiber meta tip device according to an embodiment of the present invention includes a laser device generating an input optical signal, a first optical fiber transmitting the pressure optical signal from the laser device, A first fiber optic meta tip device (FMT#1) connected to the first optical fiber, a second fiber optic meta tip device (FMT#1) and the second fiber optic meta tip device (FMT#1) are installed so that the meta surfaces including nano bricks face each other. A tip device (FMT#2), a second optical fiber that transmits an output optical signal from the second fiber meta tip device (FMT#2), and an optical receiver that receives the output optical signal transmitted from the second optical fiber and generates an output signal (Photoreceiver) included.

In addition, the data transmission system is characterized by controlling data transmission by installing a polarizer for controlling polarization between the first fiber optic meta tip device (FMT # 1) and the second fiber optic meta tip device (FMT # 2) do.

In the data transmission system using the fiber optic meta tip device according to an embodiment of the present invention, the on/off state for data transmission can be controlled by the polarization state.

21 illustrates an optical signal received by transmitting an optical pulse to a data transmission system using an optical fiber metatip device according to an embodiment of the present invention.

Referring to FIG. 21, output optical signals transmitted for TM and TE polarizations in response to input optical pulses are shown.

21 shows a laser device, a first fiber optic meta tip device (FMT#1) and a transmitter combined with a polarizer, a second fiber optic meta tip device (FMT#2), and an optical receiver (New Focus, 2011-FC-M). ) and the receiver composed of an oscilloscope (Keysight, EDUX1002A) was measured by forming a distance of 10 cm.

In the transmitter, a series of optical pulses at λ = 1550 nm are supplied and transmitted so that the TE and TM polarization components are evenly distributed, and the data transmission state can be controlled by adjusting the polarization state of the input optical signal.

Referring to FIG. 21, in the case of TM polarization, the TM polarized beam generated by the laser device is highly collimated through the first fiber optic metatip device (FMT#1) and the second fiber optic metatip device (FMT#2) The reciprocal pulse connection is "on" since the beam can safely access the photoreceiver. In the case of TEQ polarization, since the TE-polarized beam generated by the laser device (Lazer) is diverged as a vortex beam from the first fiber optic metatip device (FMT#1), the intensity is 0 along the beam axis. Therefore, in the case of TE polarization, the beam output through the second fiber optic metatip device (FMT#2) does not reach the receiver, and the interconnection becomes "off".

The on/off contrast can be controlled with reference to the sensed optical power for TE and TM polarization cases. The contrast achieved as a result of the simulation according to an embodiment of the present invention is about 15 dB, which means that data transmission based on optical interconnection is sufficiently polarization selective as intended (ie, TM polarization is “on” and TE polarization is “off”). It can be seen that it can be controlled by

In addition, polarization selective control for this may be performed by a polarizer.

22 shows the structure of a data transmission system using an optical fiber meta tip device according to another embodiment of the present invention.

Referring to FIG. 22, a data transmission system using an optical fiber meta tip device according to an embodiment of the present invention includes a laser device for generating an input optical signal, a first optical fiber for transmitting the pressure optical signal from the laser device, An electro-optic modulator (EOM) connected to the first optical fiber - a first fiber optic meta tip device (FMT#1) connected to the electro-optic modulator (EOM), and the fiber optic meta tip device (FMT#1) A second optical fiber metatip device (FMT#2) having a predetermined interval and installed so that the metasurfaces including the nano bricks face each other, and a second optical fiber metatip device (FMT#2) that transmits an output optical signal. and a photoreceiver receiving an optical fiber and an output optical signal transmitted from the second optical fiber and generating an output signal.

An electro-optical modulator (EOM) is electrically connected to a signal generator.

In addition, the electro-optic modulator (EOM) may further include a polarization controller and an erbium doped fiber amplifier (EDFA) for amplifying an optical signal.

In one embodiment of the present invention, an experiment for optical interconnection was conducted using a data transmission system using an optical fiber metatip device as shown in FIG. 21.

In the simulation according to an embodiment of the present invention, a light beam of λ = 1550 nm is generated from a laser device, connected to an electro-optical modulator (iXblue, MX-LN-10) through a first optical fiber, and the electro-optical modulator (iXblue, MX-LN-10) is connected to the first optical fiber meta tip device (FMT#1). After installing the second fiber optic meta tip device (FMT#2) at a distance of 5 mm from the first fiber optic meta tip device (FMT#1), the second fiber optic meta tip device (FMT#2) transmits light to the second optical fiber. It is connected to the photoreceiver.

In one embodiment of the present invention, a digital communication analyzer ((Agilent, DAC-J 86100C)) was used as the receiver for optical signal analysis.

In the simulation according to an embodiment of the present invention, light from a laser of λ = 1550 nm is modulated by an electro-optical modulator (EOM) driven by a signal generator together with a radio frequency amplifier, and a first fiber optic metatip device (FMT#1). ) and the optical signal transmitted through the second optical fiber meta tip device (FMT#2) is analyzed in a digital communication analyzer (DCA).

Referring to FIG. 22, data can be transmitted by generating a signal to be transmitted by the signal generator and modulating it with a laser light signal by an electro-optical modulator (EOM).

In addition, on/off control according to TE and TM polarization can be performed by the polarization controller.

23 illustrates an eye pattern according to a data transmission rate by a data transmission system using an optical fiber metatip device according to another embodiment of the present invention.

23 shows the first fiber optic metatip device (FMT# 1) and the second fiber optic metatip by maintaining the 'on' state of the 2 ³¹ -1 pseudorandom bit sequence signal to measure the performance of the optical interconnection. It is transmitted as high-speed data of ~5 Gbps through the device (FMT#2).

Referring to FIG. 23, it shows a clear eye pattern at a data rate of ~ 5 Gbps, which is analyzed to mean stable data transmission.

FIG. 24 shows measured extinction ratios for data rates in the range of 1 to 5 Gbps transmitted in FIG. 23 .

Referring to FIG. 24, it shows extinction ratios measured for digital signals transmitted for data rates ranging from 1 to 5 Gbps. Extinction ratios, which are the ratio of the minimum and maximum values that can take the output light intensity, are formed at 9 to 11 dB, which is around 10 dB for data rates in the range of 1 to 5 Gbps, and analyzed for stable data transmission.

In addition, a dielectric metasurface (MS) integrated into an optical fiber may further accommodate other salient functions of data transmission besides vortex generation and beam collimation described above.

For example, a fiber optic metatip (FMT) according to an embodiment of the present invention can be applied to fiber optic imaging or optical trapping by arranging nanobricks according to a computer-generated hologram or a lens exhibiting a high numerical aperture.

And by applying advanced manufacturing techniques such as machining, chemical etching, focused ion beam (FIB) etching, laser machining, self-assembly, chemical/physical deposition, and material transfer, various types of fiber optic tips can be fabricated.

For example, in the case of a plasmonic fiber metatip (FMT), a metal nanostructure prepared through a focused ion beam (FIB) can be precisely positioned on a fiber core to activate nanoprobes that can operate in harsh environments.

EBL has also been used to directly create metal nanorings or hybrid metal-dielectric nanostructures on fiber faces.

Electron beam lithography (EBL) is generally preferred over focused ion beam (FIB) lithography [44]. Additionally, all-dielectric MS has been demonstrated to be amenable to large-scale manufacturing via EBL.

Compared to direct writing patterning of fiber tips, it is more advantageous to fabricate the metasurface independently on a separate substrate and tether it to the fiber tip. Considering that the size of the fiber is standardized and the pigtailing process is well established, the manufacturing method according to an embodiment of the present invention can be produced in a very suitable form.

In addition, in the manufacturing method according to an embodiment of the present invention, a multi-channel optical interconnect or fiberscope can be stably implemented in a subminiature footprint by simultaneously adding several metasurfaces (MS) to an optical fiber bundle.

The fiber optic metatip device according to an embodiment of the present invention, due to the polarization-tailored propagation phase modulation enabled by the low-loss nanobrick, highly efficient dual-function spatial light manipulation, including vortex generation and beam collimation, is suitable for optical communication in the communication band of 1550 nm wavelength. can be applied effectively.

Additionally, a pair of fiber optic metatip devices can be deployed to form a polarization-selective optical interconnect, providing satisfactory on/off contrast and extinction ratios for high-speed data transmission of 5 Gbps.

A fiber optic metatip (FMT) device according to an embodiment of the present invention serves as a promising bridge between fiber optic technology and new planar optics and photonics fields by implementing a dielectric metasurface (MS) on an optical fiber, thereby enabling the development of highly integrated miniaturized photonics. direction can be given.

25 illustrates a manufacturing process of a dielectric metasurface in an optical fiber metatip device according to an embodiment of the present invention.

2cm²의 면적을 가진 석영(이산화 규소, SiO₂)이 준비된다. 준비단계에서 기판은 석영 기판과 a-Si: H 층 사이의 접착을 촉진하기 위해 먼저 아세톤/ 이소 프로필 알코올 /탈 이온수로 세척하는 과정을 포함한다.Referring to FIG. 25, first, a substrate preparation step is performed. In one embodiment of the present invention, the thickness of 430㎛

Quartz (silicon dioxide, SiO ₂ ) with an area of 2 cm ² is prepared. In the preparation step, the substrate is first cleaned with acetone/isopropyl alcohol/deionized water to promote adhesion between the quartz substrate and the a-Si:H layer.

Next, a step (PECVD) of depositing a hydrogenated amorphous silicon (a-Si: H) layer on the front and rear surfaces of the quartz substrate by a plasma enhanced chemical vapor deposition (PECVD) method is performed. In the PECVD step, a 900 nm thick a-Si:H film layer is deposited on the quartz substrate side using plasma-enhanced chemical vapor deposition (PlasmaLab 100, Oxford) under optimal conditions. After the PECVD step, a spin coating step (Spin coating step) of forming a first resist layer by spin-coating an electron beam resist (ZEP520A from Zeon Chemicals) on the front surface a-Si:H layer is performed. In one embodiment of the present invention, an electron beam (e-beam) resist (ZEP520A from Zeon Chemicals) is spin-coated on the a-Si:H layer, and then a thin layer of e-spacer ( The process of building Showa Denko's 300Z) is further included.

Forming a first resist pattern layer corresponding to the metasurface pattern set on the front surface of the substrate through an electron beam lithography (EBL) process on the first resist layer after the spin coating step (electron beam lithography (EBL step) )) is performed.

In the EBL step, the metasurface pattern and alignment marks are written to the first resist layer via e-beam lithography (Raith150 EBL) with subsequent development (ZED-N50).

Next, Al deposition is performed to form a hard mask on the upper surface of the first resist pattern layer including the concave groove. A 60 nm thick Al layer used as a hard mask is deposited on the resist developed area by electron beam evaporation.

Next, the first resist pattern layer protruding from the top of the substrate is lifted and removed by the lift-off solvent (ZDMAC of Zeon Co.), and the front surface is patterned with the Al layer remaining in the concave groove. Lift-off step (lift-off step) is performed.

After the lift-off step, an etching step (Etching step) of etching the front-side a-Si:H layer with the front-side metasurface pattern designed using the patterned Al layer as a hard mask is performed. In the etching step, the patterned Al is utilized as a hard mask during dry etching to transfer the designed pattern to the underlying a-Si:H layer via fluorine-based inductively coupled plasma reactive ion etching (Oxford Plasmalab System 100). For example, in the step, the a-Si:H layer is etched with the designed pattern through fluorine-based inductively coupled plasma reactive ion etching (Oxford PlasmaLab System 100) to form a patterned front a-Si:H layer.

Etching conditions are optimized to ensure a vertical side profile for the a-Si:H nanobrick.

Next, an Al removing step (Al removing step) of forming a metasurface by performing wet etching to remove the patterned AL layer used as a hard mask remaining at the end of the a-Si:H layer is performed.

After the metasurface on which the nanobricks are formed is manufactured by the above process, an optical fiber attachment process for attaching an optical fiber is performed.

In the optical fiber attachment process, first, a step of mounting a fiber block to an end of an optical fiber is performed.

Next, the completed planar metasurface (MS) is accurately aligned with the fiber block-mounted optical fiber (SMF) using a vision system. In one embodiment of the present invention, the optical fiber (SMF) was prepared in a length of 50 cm.

The completed metasurface is firmly fixed using a holder, and then a fiber block (length: 3.3mm, width: 10.5mm, and height: 2.0mm) surrounding the optical fiber is fixed by vacuum mounting on a motorized translation stage. A step of fixing in position and aligning is performed. In the aligning step, the center of the rear surface of the metasurface (MS) board is aligned to coincide with the end of the optical fiber to which the fiber block is mounted.

2cm²의 풋프린트의 메타표면을 UV 경화형 에폭시로 파이버블록에 접착하여 완성시킨다. 에폭시 두께는 30㎛이다.And lastly

The metasurface of the 2cm ² footprint is completed by bonding to the fiber block with UV curing epoxy. The epoxy thickness is 30 μm.

In the completed optical fiber metatip device, the distance between the end surface of the optical fiber and the nanobricks is 460 μm, including the height of the quartz substrate and the thickness of the epoxy.

10: fiber optic metatip device
110: optical fiber
120: fiber block
200: metasurface
250: unit cell

Claims (14)

In the dielectric metasurface-based optical fiber metatip device,
The optical fiber metachip device
A metasurface formed by a combination of nano-brick unit cells, one side of which is formed of a substrate of nano-brick unit cells, and the other side of which is formed of nano-brick of nano-brick unit cells;
an optical fiber connected to the center of one side of the metasurface and transmitting an input or output optical signal;
A fiber block surrounding the end of the optical fiber at the end of the optical fiber, connected to one side of the metasurface together with the optical fiber, and maintaining a connection state with the metasurface,
The optical fiber metachip device, characterized in that the substrate is formed of silicon dioxide (SiO ₂ ), and the nanobrick is formed of hydrogenated amorphous silicon (a-Si: H). According to claim 1,
The fiber optic metachip device is characterized in that the optical fiber metachip device is output as a vortex beam or a collimated beam according to the TE polarization (E-) or TM polarization (H-) of the optical signal input to the optical fiber. According to claim 2,
The optical fiber metachip device, characterized in that the phase profile for TE polarization (E-) or TM polarization (H-) of the nanobrick unit cell of the metasurface is calculated by the following equation.

Where (x, y) is the coordinates corresponding to the center of each unit cell relative to the center of the metasurface (MS) (when the center coordinates x ₀ , y ₀ , x=x ₀ -x ₁ , y= x ₀ -x ₁ ) and

and

are the focal lengths for TE and TM respectively, n is the refractive index of the surrounding medium and

represents the topological charge of the vortex. According to claim 3,
The nano-brick of the nano-brick unit cell is formed in a bar shape,
The height is 900 nm, the nanobrick unit cell is formed in a square of 700 mm,
The optical fiber metachip device, characterized in that the horizontal and vertical lengths of the nanobricks are set according to the phase profile according to the position of the metasurface in the range of 150 to 600 nm. According to claim 4
The optical fiber metachip device
Phase shift on the metasurface for the input optical signal (

) Angle is controlled to vary in the range of 0 to 2π, and the transmission amplitude (A _TE, A _TM ) ratio for incident light is controlled in the range of 0 to 1. According to claim 4,
The optical fiber metachip device,
When an optical signal of wavelength λ = 1550 nm is input,
For TE polarization (E-), a vortex beam is output,
An optical fiber metachip device characterized in that output as a collimated beam for TM polarization (H-). According to claim 4,
The optical fiber metachip device
Connecting the optical fiber to one side of the metasurface is characterized in that it is bonded by epoxy,
The optical fiber metachip device, characterized in that the substrate thickness of the nano-brick unit cell is 430㎛, and the adhesive thickness of the epoxy is 30㎛. According to claim 7,
The optical fiber metachip device
When an optical signal of wavelength λ = 1550 nm is input,
Meta tip device characterized in that the transfer efficiency is 57% In a data transmission system using an optical fiber metatip device based on a dielectric metasurface,
The data transmission system,
a laser device generating an input optical signal;
a first optical fiber transmitting the pressure optical signal from the laser device;
A first optical fiber meta tip device connected to the first optical fiber;
a second fiber optic meta tip device having a predetermined distance from the first fiber optic meta tip device and installed so that the meta surface including the nano brick faces each other; and
a second optical fiber transmitting an output optical signal from the second optical fiber meta tip device and an optical receiver receiving an output optical signal transmitted from the second optical fiber and generating an output signal; Including,
The first optical fiber metachip device,
A metasurface formed by a combination of nano-brick unit cells, one side of which is formed of a substrate of nano-brick unit cells, and the other side of which is formed of nano-brick of nano-brick unit cells; and a fiber block surrounding the end of the first optical fiber at the end of the first optical fiber and maintaining a connection state with the metasurface,
The data transmission system, characterized in that the substrate is formed of silicon dioxide (SiO ₂ ), and the nano-brick is formed of hydrogenated amorphous silicon (a-Si:H). According to claim 9,
Further comprising a polarizer for controlling polarization between the first fiber optic meta tip device and the second fiber optic meta tip device,
A data transmission system characterized in that on / off of data transmission is controlled according to the polarization control of the polarizer. According to claim 9,
The data transmission system,
An “on” signal is transmitted for the TM polarization of the input optical signal,
A data transmission system characterized in that an “off” signal is transmitted for the TM polarization of the input optical signal. According to claim 9,
The data transmission system
An electro-optical modulator electrically connected to a polarization controller and a signal generator to the laser device and the first fiber optic metatip device,
Transmitting data by modulating an optical signal generated from the laser device by the signal generator,
A data transmission system characterized in that on / off control is performed according to TE and TM polarization by the polarization controller. According to claim 9,
The data transmission system
A data transmission system characterized in that extinction ratios for data rates in the range of 1 to 5 Gbps are 9 to 11 dB. In the manufacturing method of the optical fiber metachip device,
The manufacturing method,
a) preparing a substrate of SiO ₂ material;
b) depositing a hydrogenated amorphous silicon layer on the front surface of the substrate by a plasma enhanced chemical vapor deposition (PECVD) method;
c) a first spin coating step of forming a first resist layer on the hydrogenated amorphous silicon layer;
d) forming a first resist pattern layer corresponding to a metasurface pattern established on the first resist layer through an electron beam lithography process;
e) forming an Al layer by depositing Al on the top surface of the first resist pattern layer and on the concave groove;
f) lifting and removing all of the first resist pattern layer protruding from the top of the substrate using a lift-off solvent, and forming a patterned Al layer on the front surface of the substrate with the Al layer remaining in the concave groove portion; ;
g) etching a hydrogenated amorphous silicon layer on the front surface of the substrate with the set metasurface pattern using the patterned Al layer as a hard mask;
h) forming a metasurface by removing the patterned Al layer remaining at the end of the hydrogenated amorphous silicon layer on the front surface after the etching step;
i) mounting a fiber block on an end of an optical fiber; and
j) aligning the center of the formed metasurface substrate to coincide with the end of the optical fiber to which the fiber block is mounted, and bonding the metasurface substrate and the fiber block with UV curable epoxy; Method of manufacturing a fiber optic metachip device comprising a.

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