A wavelength widely tunable optical band-rejection filter

Abstract

The application discloses a wavelength widely adjustable optical band-stop filter, comprising an optical transparent medium grating, a two-dimensional material layer, an optical medium layer and a metal film substrate, characterized in that the optical transparent medium grating and the two-dimensional material layer are arranged at the top of the structure, the two-dimensional material layer is laid on the top of the optical transparent medium grating or the optical medium layer, and the metal film substrate is bonded to the bottom surface of the optical medium layer. The two-dimensional material light absorption structure is designed into a single port by the metal film substrate to block the transmitted light, so that the structure realizes perfect absorption under the condition of meeting the critical coupling. The application can widely adjust the working wavelength by changing the angle of the incident light, and keep the filtering capacity above 99%.

Description

Technical Field

[0001] This invention relates to the field of optical bandstop filter technology, and more particularly to an optical bandstop filter with a wide wavelength tunable range. Background Technology

[0002] Optical filters are fundamental optical components with crucial applications in optical measurement, optical communication, and optical sensing. The function of an optical filter is frequency selection, and they are primarily classified into four types: low-pass, high-pass, band-pass, and band-stop. Ordinary optical filters operate at a fixed wavelength, typically filtering only one fixed band. However, wavelength-tunable optical filters can adjust their operating wavelength according to different requirements. Therefore, a single optical filter with a wide range of adjustable operating wavelengths can function as multiple filters with different operating wavelengths, achieving cost savings and a simplified device structure.

[0003] Two-dimensional materials are crystals composed of a single layer of atoms or molecules, with a thickness only at the atomic level. They can be considered as the basic two-dimensional structural units of other dimensional materials, such as being coated into zero-dimensional materials, rolled into one-dimensional materials, or stacked into three-dimensional materials. Since graphene was exfoliated from graphite crystals by Novoselov KS and Geim AK in 2004 using a mechanical exfoliation method, more and more two-dimensional materials have been discovered and prepared, greatly expanding the breadth of the materials science field. Due to their unique structure, two-dimensional materials possess many properties that traditional materials do not have. For example, graphene, as the world's first two-dimensional material, has an ultra-wide absorption spectrum, an ultra-fast photoresponse rate, an ultra-high carrier mobility, and tunable conductivity, making it an ideal material for optical and optoelectronic devices.

[0004] However, due to their thinness, two-dimensional materials typically have weak light absorption, which severely limits their practical application in optical and optoelectronic devices. Summary of the Invention

[0005] 1. Technical problems to be solved

[0006] The purpose of this invention is to address the problem that two-dimensional materials have weak light absorption in existing technologies, making them difficult to apply in optical and optoelectronic devices. This invention proposes an optical bandstop filter with a wide wavelength tunable range. The optical bandstop filter proposed in this invention solves the problem of the non-adjustable operating wavelength of traditional optical filters and enables device miniaturization.

[0007] 2. Technical Solution

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A wide-range tunable optical bandstop filter includes an optically transparent dielectric grating, a two-dimensional material layer, an optical dielectric layer, and a metal thin film substrate. The optically transparent dielectric grating and the two-dimensional material layer are disposed on the top of the structure, the two-dimensional material layer is laid flat on top of the optically transparent dielectric grating or the optical dielectric layer, and the metal thin film substrate is bonded to the bottom surface of the optical dielectric layer.

[0010] Preferably, the optical bandstop filter operates in the 300nm-30μm band, the incident light source is a broadband light source, the magnetic field polarization direction of the incident light is perpendicular to the one-dimensional optical transparent medium grating, and the operating wavelength is continuously adjusted by changing the incident light angle (θ).

[0011] Preferably, the optically transparent medium grating is a one-dimensional grating composed of a large number of identical optically transparent medium strips arranged in parallel.

[0012] Preferably, the period P1 of the optically transparent dielectric grating is 100nm-10μm.

[0013] Preferably, the material of the optically transparent dielectric grating is any one of transparent polymethyl methacrylate, fluororesin, cyclic olefin polymer, tetrafluoroethylene / hexafluoropropylene copolymer, fluoroethylene propylene, silicon dioxide, etc., wherein the length L1>30μm, the thickness D1 satisfies 10nm≤D1≤10μm, and the duty cycle W1 / P1 of the grating satisfies 0≤W1 / P1≤1.

[0014] Preferably, the two-dimensional material layer is a light-absorbing thin-film material, which can be any one of graphene, transition metal sulfide, black phosphorus, hexagonal boron nitride or other thin film materials, with a length L2>30μm, a width W2>30μm, and a thickness D2 that is the actual thickness of the thin-film material.

[0015] Preferably, the optical dielectric layer is a dielectric material, which is any one of the following dielectric materials: silicon dioxide, aluminum oxide, magnesium oxide, magnesium difluoride, titanium dioxide, niobium pentoxide, hafnium dioxide, etc., wherein the length L3>30μm, the width W3>30μm, and the thickness D3 satisfies 10nm≤D3≤100μm.

[0016] Preferably, the metal thin film substrate is a metal material that totally reflects incident light. The metal material includes any one or any combination of gold, silver, aluminum, copper, platinum, palladium, chromium, titanium, and nickel. The length and width of the metal thin film substrate are usually consistent with the optical medium layer, and the thickness D4 > 20 nm.

[0017] 3. Beneficial effects

[0018] Compared with the prior art, the advantages of this invention are:

[0019] (1) In this invention, the two-dimensional material light absorption structure is designed as a single port by blocking the transmitted light through a metal thin film substrate, so that the structure can achieve perfect absorption under the condition of satisfying critical coupling. The designed band-stop filter achieves a filtering capability of more than 99% in the working band.

[0020] (2) In this invention, by changing the incident angle of the light source, the wavelength of the resonant mode of the light absorption structure is adjusted, thereby changing the absorption band of the band-stop filter and realizing a wide range of adjustable band operating bands.

[0021] (3) In this invention, by changing the structural parameters, the absorption bandwidth of the light absorption structure is adjusted, thereby realizing the control of the working bandwidth of the band-stop filter.

[0022] (4) In this invention, the size of the optical bandstop filter is only at the micrometer level, realizing the miniaturization of the optical bandstop filter, which has important application prospects in the fields of micro optoelectronic devices and flexible optoelectronic devices. Attached Figure Description

[0023] Figure 1 This is a three-dimensional structural schematic diagram of Embodiment 1 of the present invention;

[0024] Figure 2 This is the absorption spectrum of Embodiment 1 of the present invention under vertical incident conditions;

[0025] Figure 3 This is a schematic diagram of the electric field mode distribution characteristics under vertical incidence conditions in Embodiment 1 of the present invention;

[0026] Figure 4 The relationship between the peak absorptivity and peak wavelength of the absorption peak in Example 1 of this invention as a function of the incident angle is shown.

[0027] Figure 5 The absorption spectra of Embodiment 2 of the present invention are shown at different incident angles.

[0028] Figure 6 This is a front view of Embodiment 3 of the present invention.

[0029] In the figure: 1 Optical transparent dielectric grating, 2 Two-dimensional material layer, 3 Optical dielectric layer, 4 Metal thin film substrate. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0031] Example 1:

[0032] An optical bandstop filter with a wide wavelength range is disclosed, comprising an optically transparent dielectric grating 1, a two-dimensional material layer 2, an optical dielectric layer 3, and a metal thin film substrate 4. The optically transparent dielectric grating 1 is located on the top layer of the structure, covering the two-dimensional material layer 2, which is laid flat on the optical dielectric layer 3. The metal thin film substrate 4 is located at the bottom and acts as a reflector, directly in physical contact with the optical dielectric layer 3.

[0033] In this embodiment, the incident light is broadband linearly polarized light, which shines onto the optical bandstop filter from above the structure.

[0034] In this embodiment, Figure 1 In the diagram, xyz represents the three-dimensional coordinate system orientation of the structure. E represents the electric field polarization direction of the incident light wave. H represents the magnetic field polarization direction of the incident light wave, which is always perpendicular to the length direction of the optical transparent medium grating 1, i.e., parallel to the x-axis. k represents the wave vector direction when the incident light is perpendicularly incident. k' represents the wave vector direction when the incident light is obliquely incident, which lies on the xoz plane and is always perpendicular to H. The angle between k' and k is the incident angle θ.

[0035] In this embodiment, Figure 1 The optically transparent dielectric grating 1 has a length of L1, a thickness of D1, and a duty cycle of W1 / P1, where W1 is the width of a single optically transparent dielectric strip and P1 is the grating period. The two-dimensional material layer 2 has a length of L2, a width of W2, and a thickness of D2.

[0036] In this embodiment, the optical medium layer 3 has a length of L3, a width of W3, and a thickness of D3. The metal thin film substrate 4 has a length of L4, a width of W4, and a thickness of D4, wherein L4 and W4 are generally equal to L3 and W3, and therefore are not included in the design. Figure 1 The bid was successful.

[0037] In this embodiment, the optical transparent medium grating 1 on the two-dimensional material light absorption structure is made of polymethyl methacrylate, with a length L1 of 400 μm, a thickness D1 of 170 nm, a grating period P1 = 1300 nm, and a grating duty cycle W1 / P1 = 0.5; the two-dimensional material layer 2 is made of monolayer graphene, with a length L2 of 400 μm, a width W2 of 400 μm, and a thickness D2 that is the thickness of the monolayer graphene, approximately 0.34 nm; the optical medium layer 3 is made of silicon dioxide, with a length L3 of 500 μm, a width W3 of 500 μm, and a thickness D3 of 540 nm; the metal thin film substrate 4 is made of gold, with a length L4 of 500 μm, a width W4 of 500 μm, and a thickness D4 of 200 nm.

[0038] In this embodiment, from Figure 2 As can be seen, the absorption peak wavelength of the two-dimensional material light absorption structure is 1538.5 nm, the absorption rate is close to 100%, and the bandwidth of the absorption peak is 17.5 nm.

[0039] In this embodiment, Figure 3 The basic structural unit of the two-dimensional material light absorption structure is shown in the middle. From top to bottom, it consists of an air layer, an optically transparent medium grating 1, a two-dimensional material layer 2, an optical medium layer 3, a metal thin film substrate 4, and an air layer. The color legend on the right represents the normalized electric field intensity.

[0040] In this embodiment, from Figure 3 As can be seen, a strong local electric field is excited in the two-dimensional material light-absorbing structure. The electric field mode distribution is elliptical, with the strong electric field region located at the center of the ellipse. The two-dimensional material layer 2 is located at the center of the strong electric field region, so the energy of the incident light is mainly absorbed by the graphene. At this time, the light-absorbing structure achieves perfect absorption, the frequency of the incident light is equal to the resonant frequency of the mode, and the leakage rate of the mode is equal to the absorption rate of the light-absorbing structure, satisfying the critical coupling condition.

[0041] In this embodiment, Figure 4 The horizontal axis represents the incident angle, the vertical axis on the left represents the wavelength, the vertical axis on the right represents the peak absorptivity, and the arrows indicate the vertical axis corresponding to the curves. The total absorption curve represents the light absorption rate of the light-absorbing structure, and the graphene absorption curve represents the light absorption rate of graphene in the light-absorbing structure.

[0042] In this embodiment, due to the wavelength of the resonant mode in the optical absorption structure being different from the wave vector component k of the mode... x Closely related, k x The value of is k'·sinθ. Therefore, the wavelength of the resonant mode excited by the external incident light will change under different incident angles, and the absorption wavelength of the light absorption structure will also change accordingly.

[0043] In this embodiment, from Figure 4 As can be seen, when the incident angle gradually increases from 0° to 45°, the peak wavelength of the absorption peak of the optical bandstop filter continuously decreases from 1538.5nm to 1332.4nm. During this process, the peak absorption rate of the filter is higher than 99%. Therefore, the filter can achieve a good filtering effect in a wavelength range of more than 200nm. At the same time, the peak absorption rate of the absorption peak changes very slowly when the incident angle increases, and near-perfect absorption can be achieved in a wide range of incident angles. Among them, the peak absorption rate of graphene is close to 90%.

[0044] Example 2:

[0045] It has the implementation content of the above embodiments, wherein the specific implementation methods of the above embodiments can be referred to the above description, and the embodiments here will not be described in detail again; however, the difference between the embodiments in this application and the above embodiments is that:

[0046] In this embodiment, the optically transparent dielectric grating 1 on the two-dimensional material light absorption structure is made of polymethyl methacrylate, with a length L1 of 400 μm, a thickness D1 of 160 nm, a grating period P1 = 1150 nm, and a grating duty cycle W1 / P1 = 0.5; the two-dimensional material layer 2 is made of monolayer graphene, with a length L2 of 400 μm, a width W2 of 400 μm, and a thickness D2 that is the thickness of the monolayer graphene, approximately 0.34 nm.

[0047] In this embodiment, the optical dielectric layer 3 is made of silicon dioxide, with a length L3 of 500 μm, a width W3 of 500 μm, and a thickness D3 of 1100 nm; the metal thin film substrate 4 is made of gold, with a length L4 of 500 μm, a width W4 of 500 μm, and a thickness D4 of 200 nm. Figure 5 As can be seen, within the incident angle range of 0° to 20°, the peak absorptivity and absorption bandwidth of the light absorption structure remain basically unchanged, with the peak absorptivity approaching 100% and the bandwidth of the absorption peak being approximately 5 nm.

[0048] Example 3:

[0049] It has the implementation content of Embodiment 1, wherein the specific implementation methods of the above embodiments can be referred to the above description, and the embodiments here will not be repeated in detail; however, the difference between the embodiments in this application and the above embodiments is that:

[0050] In this embodiment, the two-dimensional material layer 2 is located on the top layer of the structure and is laid flat on the optically transparent dielectric grating 1. The optically transparent dielectric grating 1 is on the optical dielectric layer 3. The metal thin film substrate 4 is at the bottom and acts as a reflector, directly in physical contact with the optical dielectric layer 3. The front structural schematic diagram is shown below. Figure 6 As shown.

[0051] In this embodiment, the two-dimensional material layer 2 is made of monolayer graphene with a length L2 of 400 μm, a width W2 of 400 μm, and a thickness D2, which is the thickness of the monolayer graphene, approximately 0.34 nm. The optically transparent dielectric grating 1 is made of polymethyl methacrylate with a length L1 of 400 μm, a thickness D1 of 140 nm, a grating period P1 = 1300 nm, and a grating duty cycle W1 / P1 = 0.5. The remaining structural parameters are the same as in Example 1. At this point, the absorption peak wavelength of the two-dimensional material light absorption structure is 1530.2 nm, the absorptivity is close to 100%, and the bandwidth of the absorption peak is 10.9 nm.

[0052] In this invention, the operating band and bandwidth of the band-stop filter can be controlled by changing the structural parameters, and the operating band of the band-stop filter can be controlled over a wide range by changing the incident angle.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A wide-range tunable optical bandstop filter, comprising an optically transparent dielectric grating, a two-dimensional material layer, an optical dielectric layer, and a metal thin film substrate, characterized in that, The optically transparent dielectric grating and the two-dimensional material layer are disposed on the top of the structure. The two-dimensional material layer is laid flat on top of the optically transparent dielectric grating or the optical dielectric layer. The metal thin film substrate is bonded to the bottom surface of the optical dielectric layer. The optical bandstop filter operates in the 300nm-30μm band. The incident light source is multi-wavelength light. The magnetic field polarization direction of the incident light source is perpendicular to the one-dimensional optically transparent dielectric grating. The operating wavelength is continuously adjusted by changing the incident light angle (θ). The optically transparent dielectric grating is a one-dimensional grating composed of a large number of identical optically transparent dielectric strips arranged in parallel. The period P1 of the optically transparent dielectric grating is 100. The optically transparent dielectric grating is made of any one of the following materials: transparent polymethyl methacrylate, fluoropolymer, cyclic olefin polymer, tetrafluoroethylene / hexafluoropropylene copolymer, fluoroethylene propylene, and silicon dioxide. The length L1 is greater than 30 μm, the thickness D1 satisfies 10 nm ≤ D1 ≤ 10 μm, and the duty cycle W1 / P1 of the grating satisfies 0 ≤ W1 / P1 ≤ 1. The two-dimensional material layer is a light-absorbing thin-film material, which is any one of graphene, transition metal sulfide, black phosphorus, hexagonal boron nitride, or other thin-film materials. The length L2 is greater than 30 μm, the width W2 is greater than 30 μm, and the thickness D2 is the actual thickness of the thin-film material.

2. The optical bandstop filter with a wide wavelength range adjustable according to claim 1, characterized in that, The optical dielectric layer is a dielectric material, which can be any one of silicon dioxide, aluminum oxide, magnesium oxide, magnesium difluoride, titanium dioxide, niobium pentoxide, or hafnium dioxide, wherein the length L3 > 30 μm, the width W3 > 30 μm, and the thickness D3 satisfies 10 nm ≤ D3 ≤ 100 μm.

3. The optical bandstop filter with a wide wavelength range adjustable according to claim 1, characterized in that, The metal thin film substrate is a metal material that totally reflects incident light. The metal material includes any one or any combination of gold, silver, aluminum, copper, platinum, palladium, chromium, titanium, and nickel. The length and width of the metal thin film substrate are consistent with the optical medium layer, and the thickness D4 > 20 nm.

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