A terahertz isolator based on H-type metamaterials and an isolation performance testing system

Abstract

The present invention relates to the technical field of isolators, and particularly to a terahertz isolator based on H-type metamaterials and an isolation performance testing system. An embodiment of the present invention provides an isolator based on H-type metamaterials, which includes an H-type metamaterial and a polarizer; the H-type metamaterial includes a plurality of periodic units, and the periodic units are periodically arranged in two directions along the edges of adjacent units perpendicular to each other to form a metamaterial; the periodic unit is a cuboid including two square faces, and sequentially includes a first dielectric layer, a second dielectric layer, and a third dielectric layer along the thickness direction, and H-type metal layers are provided on the faces of the second dielectric layer and the third dielectric layer facing the first dielectric layer; the polarizer is used to transmit polarized light with a polarization direction perpendicular to the lines of the wire grid and reflect polarized light with a polarization direction parallel to the lines of the wire grid. An embodiment of the present invention provides an isolator based on H-type metamaterials and a testing system for its isolation performance of terahertz waves, which can provide an isolator for isolating terahertz electromagnetic waves.

Description

Technical Field

[0001] The present invention relates to the technical field of isolators, and particularly relates to an isolator based on H-shaped metamaterials and an isolation performance testing system. Background Art

[0002] Isolation devices are mainly used for inter-stage isolation, impedance matching, and decoupling between device units, preventing damage to active devices caused by reflected echoes and scattering in the system, and reducing additional noise brought by echoes, thereby improving the stability and reliability of the system.

[0003] In terahertz optical transmission, communication, and radar detection systems, it is often necessary to overcome the interference of backward reflected light. Therefore, there is an urgent need for an isolator for terahertz transmission to ensure the unidirectional and efficient transmission of terahertz waves. Summary of the Invention

[0004] Embodiments of the present invention provide a terahertz isolator based on H-shaped metamaterials and an isolation performance testing system, which can provide an isolator for isolating reflected terahertz electromagnetic waves.

[0005] In a first aspect, embodiments of the present invention provide an isolator based on H-shaped metamaterials, including H-shaped metamaterials and a polarizer;

[0006] The H-shaped metamaterials include a plurality of periodic units, and the periodic units are periodically arranged in two directions along the edges of adjacent units perpendicular to each other to form metamaterials;

[0007] The periodic unit is a cuboid including two square faces, and sequentially includes a first dielectric layer, a second dielectric layer, and a third dielectric layer along the thickness direction. H-shaped metal layers are provided on the surfaces of the second dielectric layer and the third dielectric layer facing the first dielectric layer;

[0008] The H-shaped metamaterials are used to convert linearly polarized light into circularly polarized light or convert circularly polarized light into linearly polarized light;

[0009] The polarizer includes a wire grid. The wire grid includes a plurality of lines parallel to each other in the same plane. Each line of the wire grid is parallel to the diagonal of the periodic unit of the H-shaped metamaterials. The polarizer is used to transmit polarized light with a polarization direction perpendicular to the lines of the wire grid and reflect polarized light with a polarization direction parallel to the lines of the wire grid;

[0010] Terahertz electromagnetic waves are incident on the polarizer. The terahertz electromagnetic waves pass through the polarizer to form a first linearly polarized light. The first linearly polarized light passes through the H-shaped metamaterial to form a first circularly polarized light. After the first circularly polarized light is reflected by a subsequent optical device, a second circularly polarized light is formed. The second circularly polarized light passes through the H-shaped metamaterial to form a second linearly polarized light. The polarization directions of the first linearly polarized light and the second linearly polarized light are perpendicular. The rotation directions of the first circularly polarized light and the second circularly polarized light around the propagation direction are opposite. The polarization direction of the second linearly polarized light is parallel to the lines of the wire grid and cannot pass through the polarizer. It is reflected by the polarizer to isolate the terahertz electromagnetic waves and prevent the reflected terahertz electromagnetic waves from affecting the incident light source.

[0011] In a possible design, the side length of the square face of the periodic unit is 50 - 70 μm, the thickness of the first dielectric layer is 3 - 7 μm, the thickness of the second dielectric layer is 15 - 25 μm, the thickness of the third dielectric layer is 5 - 15 μm, and the thickness of the H-shaped metal layer is 180 - 220 nm;

[0012] The H-shaped metal layer includes two mutually parallel first metal strips and a second metal strip connecting the midpoints of the two first metal strips. The lengths of the first metal strip and the second metal strip are both 30 - 42 μm, and the widths are both 2 - 4 μm.

[0013] In a possible design, the preparation material of the H-shaped metal layer includes gold;

[0014] The preparation materials of the first dielectric layer, the second dielectric layer, and the third dielectric layer include polyimide.

[0015] In a second aspect, an embodiment of the present invention further provides an isolation performance test system, based on the isolator described in any one of the above first aspects, including two such isolators, and the H-shaped metamaterials of the two isolators are sequentially placed on the same optical axis;

[0016] Terahertz electromagnetic waves are incident on one of the polarizers. After transmission, the first linearly polarized light is formed. The first linearly polarized light passes through one of the H-shaped metamaterials to form the first circularly polarized light. The first circularly polarized light passes through the other H-shaped metamaterial to form the second linearly polarized light. The polarization directions of the second linearly polarized light and the first linearly polarized light are perpendicular. The second linearly polarized light is reflected out of the optical path by the other polarizer;

[0017] Measuring the light intensity ratio of the second linearly polarized light reflected out of the optical path to the incident light can know the isolation effect. The linear polarization direction of the first linearly polarized light is the diagonal direction of the periodic unit of the H-shaped metamaterial. The isolation degree is obtained by testing the transmittance of the electromagnetic waves passing through the two isolators.

[0018] In a possible design, the directions of two adjacent sides of the square surface of the H-shaped metamaterial are the first direction and the second direction respectively. The transmittance of the second linearly polarized light in the first direction and the second direction is measured respectively, and the average of the two transmittances is calculated to obtain the insertion loss along the diagonal direction of the periodic unit of the H-shaped metamaterial.

[0019] In a possible design, the diameter of the wires of the wire grid is 8 - 12 μm, and the interval between the wires of the wire grid is 25 - 35 μm.

[0020] In a possible design, the material for preparing the wires of the wire grid is tungsten wire.

[0021] In a possible design, the incident angle of the terahertz electromagnetic wave is 40°. The insertion loss is 2.17 dB at 1.51 THz, the blocking bandwidth is 280 GHz at 1.37 THz - 1.65 THz, and the blocking efficiency is 20 dB.

[0022] In a possible design, the incident angle of the terahertz electromagnetic wave is 10°. The insertion loss is reduced to 1.65 dB at 1.51 THz, and the bandwidth of the 20 dB blocking efficiency is 170 GHz at 1.42 THz to 1.59 THz.

[0023] The present invention has at least the following beneficial effects compared with the prior art:

[0024] In this embodiment, since there is a lack of magneto-optical materials with gyromagnetic or gyrotropic responses in the terahertz band in nature itself, the present invention provides an artificial H-shaped metamaterial that can have gyromagnetic or gyrotropic responses in the terahertz band. The H-shaped metamaterial provided by the present invention is composed of a plurality of periodically arranged periodic units. The cross-section of the periodic unit is a square, and the periodic units are arranged along two adjacent sides perpendicular to the square with the side length as the period to form the metamaterial. The periodic unit is composed of a first dielectric layer, a second dielectric layer, and a third dielectric layer stacked in sequence along the thickness direction. H-shaped metal layers are respectively provided on the surfaces of the second dielectric layer and the third dielectric layer facing the first dielectric layer, and these two H-shaped metal layers are completely aligned up and down. The metamaterial formed by the periodic units provided with H-shaped metal layers can change the polarization state of the terahertz electromagnetic wave when the terahertz electromagnetic wave passes through. Specifically, the H-shaped metal layer includes two mutually parallel first metal strips and a second metal strip connecting the midpoints of the two first metal strips. When the terahertz electromagnetic wave passes through the metamaterial, the terahertz electric field component along the extension direction of the second metal strip increases in phase, thereby changing the polarization state of the terahertz electromagnetic wave.

[0025] In this embodiment, the extension direction of the wire grid is parallel to the diagonal of the periodic unit of the metamaterial. The polarized light is decomposed into two linearly polarized lights with equal amplitudes and the same phase in the y and x directions (the directions of two adjacent sides of the square surface of the metamaterial). After passing through the metamaterial, near 1.5 THz, the transmittances in the two directions are close. The metamaterial advances the polarized light in the y direction by 90°. The linearly polarized light is converted into left-handed circularly polarized light. The left-handed circularly polarized light becomes right-handed circularly polarized light through the reflection unit. The right-handed circularly polarized light forms a linearly polarized light polarized in the 135° direction after passing through the metamaterial and is reflected out of the optical path by the polarizer. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a schematic diagram of the application structure of a terahertz isolator provided by an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the structure of an isolation performance test system provided by an embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the structure of an isolator provided by an embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of the structure of a polarizer provided by an embodiment of the present invention;

[0031] Figure 5 It is a schematic diagram of the side sectional structure of a periodic unit provided by an embodiment of the present invention;

[0032] Figure 6 It is a schematic diagram of the top view structure of a periodic unit provided by an embodiment of the present invention;

[0033] Figure 7 It is an isolation degree diagram of an isolator provided by an embodiment of the present invention;

[0034] Figure 8 It is an insertion loss diagram of an isolator provided by an embodiment of the present invention.

[0035] In the figure:

[0036] 1 - wire grid fixing ring;

[0037] 2 - wire grid;

[0038] 3 - H-shaped metamaterial;

[0039] 4 - Metamaterial fixing ring;

[0040] 5 - First dielectric layer;

[0041] 6 - Second dielectric layer;

[0042] 7 - Third dielectric layer;

[0043] 8 - H - shaped metal layer;

[0044] 9 - First metal strip;

[0045] 10 - Second metal strip. Detailed implementation manners

[0046] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "plurality" means two or more; the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] In the description of this specification, it should be understood that the orientation terms such as "upper" and "lower" described in the embodiments of the present invention are described from the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. In addition, in the context, it should also be understood that when it is mentioned that an element is connected "above" or "below" another element, it can not only be directly connected "above" or "below" another element, but also be indirectly connected "above" or "below" another element through an intermediate element.

[0049] As shown in Figure 1 、 3 、4, 5, 6, the embodiments of the present invention provide an isolator based on H - shaped metamaterials, including H - shaped metamaterials and polarizers;

[0050] The H-type metamaterial includes multiple periodic units, and the periodic units are periodically arranged in two directions along the edges of adjacent units perpendicular to each other to form the metamaterial;

[0051] The periodic unit is a cuboid including two square faces, and sequentially includes a first dielectric layer, a second dielectric layer, and a third dielectric layer along the thickness direction. H-type metal layers are provided on the faces of the second dielectric layer and the third dielectric layer facing the first dielectric layer;

[0052] The H-type metamaterial is used to convert linearly polarized light into circularly polarized light or convert circularly polarized light into linearly polarized light;

[0053] The polarizer includes a wire grid. The wire grid includes multiple wires parallel to each other in the same plane. Each wire of the wire grid is parallel to the diagonal of the periodic unit of the H-type metamaterial. The polarizer is used to transmit polarized light with a polarization direction perpendicular to the wires of the wire grid and reflect polarized light with a polarization direction parallel to the wires of the wire grid;

[0054] Terahertz electromagnetic waves are incident on the polarizer. The terahertz electromagnetic waves pass through the polarizer to form a first linearly polarized light. The first linearly polarized light passes through the H-type metamaterial to form a first circularly polarized light. After the first circularly polarized light is reflected by a subsequent optical device, a second circularly polarized light is formed. The second circularly polarized light passes through the H-type metamaterial to form a second linearly polarized light. The polarization directions of the first linearly polarized light and the second linearly polarized light are perpendicular. The rotation directions of the first circularly polarized light and the second circularly polarized light around the propagation direction are opposite. The polarization direction of the second linearly polarized light is parallel to the wires of the wire grid and cannot pass through the polarizer. It is reflected by the polarizer to isolate the terahertz electromagnetic waves and prevent the reflected terahertz electromagnetic waves from affecting the incident light source.

[0055] In this embodiment, since there is a lack of magneto-optical materials with gyromagnetic or gyrotropic responses in the terahertz band in nature itself, the present invention provides an artificial H-type metamaterial that can have a gyromagnetic or gyrotropic response in the terahertz band. The H-type metamaterial provided by the present invention is composed of multiple periodically arranged periodic units. The cross-section of the periodic unit is square, and the periodic units are arranged with the side length as the period along two perpendicular sides of the square to form the metamaterial. The periodic unit is composed of a first dielectric layer, a second dielectric layer, and a third dielectric layer stacked in sequence along the thickness direction. H-type metal layers are provided on the upper surfaces of the second dielectric layer and the third metal layer. The metamaterial formed by the periodic units provided with H-type metal layers can change the polarization state of terahertz electromagnetic waves when the terahertz electromagnetic waves pass through. Specifically, the H-type metal layer includes two parallel first metal strips and a second metal strip connecting the midpoints of the two first metal strips. When terahertz electromagnetic waves pass through the metamaterial, the electric field component of the terahertz electromagnetic waves along the extension direction of the second metal strip increases in phase, thereby changing the polarization state of the terahertz electromagnetic waves.

[0056] In this embodiment, the extension direction of the wire grid is parallel to the diagonal of the periodic unit of the metamaterial. For example, asFigure 1 At the position shown, after passing through the polarizer, the polarization direction of the terahertz electromagnetic wave forms an angle of 45° with the x-axis. The polarized light is decomposed into two linearly polarized lights with equal amplitudes and the same phase in the y and x directions (the directions of two adjacent sides of the square surface of the metamaterial). After passing through the metamaterial, near 1.5 THz, the transmittances in the two directions are close. The metamaterial makes the polarized light in the y direction lead by 90°. The linearly polarized light is converted into a left-handed circularly polarized light. The left-handed circularly polarized light becomes a right-handed circularly polarized light through the reflection unit. The right-handed circularly polarized light forms a linearly polarized wave polarized in the 135° direction after passing through the metamaterial and is reflected out of the optical path by the polarizer.

[0057] It should be noted that after the reflection unit reflects the terahertz electromagnetic wave, the rotation direction of the circularly polarized light remains unchanged, but the propagation direction of the light changes. Therefore, relative to the propagation direction, after the terahertz electromagnetic wave is reflected by the reflection unit, the rotation direction relative to the propagation direction changes, changing from left-handed to right-handed or from right-handed to left-handed.

[0058] In this embodiment, if the incident angle is not 0, the second linearly polarized light is reflected out of the optical path, and the isolation effect of the isolation system can be obtained by testing the light reflected out of the optical path. When the incident angle is 45°, the terahertz wave is just deflected out of the system in a direction perpendicular to the incident optical path. A receiver perpendicular to the deflected optical path is set to test the properties of the terahertz wave with a 0° reflection angle. It should be noted that testing the backward-propagating electromagnetic wave with a reflection angle of 0 is of great significance in the study of radar backscattering. If the reflection angle is 0, the incident optical path and the reflection optical path will coincide, resulting in the oscillation of light waves in the system. In practical applications, the coincidence of the optical paths does not affect the application of the optical system and the isolation of terahertz electromagnetic waves.

[0059] In some embodiments of the present invention, the side length of the square surface of the periodic unit is 50 - 70 μm, the thickness of the first dielectric layer is 3 - 7 μm, the thickness of the second dielectric layer is 15 - 25 μm, the thickness of the third dielectric layer is 5 - 15 μm, and the thickness of the H-shaped metal layer is 180 - 220 nm;

[0060] The H-shaped metal layer includes two mutually parallel first metal strips and a second metal strip connecting the midpoints of the two first metal strips. The lengths of the first metal strip and the second metal strip are both 30 - 42 μm, and the widths are both 2 - 4 μm.

[0061] In this embodiment, the side length of the square surface of the periodic unit is 50 - 70 μm, the thickness of the first dielectric layer is 3 - 7 μm, the thickness of the second dielectric layer is 15 - 25 μm, the thickness of the third dielectric layer is 5 - 15 μm, and the thickness of the H-shaped metal layer is 180 - 220 nm. The parameters of the periodic unit can affect the performance of the metamaterial. Within the above ranges of the parameters, the metamaterial has an excellent effect on changing the polarization state of the terahertz wave.

[0062] In this embodiment, the H-shaped metal layer includes two mutually parallel first metal strips and a second metal strip connecting the midpoints of the two first metal strips. The lengths of the first metal strip and the second metal strip are both 30 - 42 μm, and the widths are both 2 - 4 μm. The parameters of the H-shaped metal layer can affect the performance of the metamaterial. Within the above range of parameters, the metamaterial has an excellent effect on changing the polarization state of terahertz waves.

[0063] In some embodiments of the present invention, the preparation material of the H-shaped metal layer includes gold;

[0064] The preparation materials of the first dielectric layer, the second dielectric layer, and the third dielectric layer include polyimide.

[0065] In this embodiment, gold has excellent and stable physical and chemical properties, is an excellent conductor, and has excellent processability. Selecting gold as the preparation material of the H-shaped metal layer can further improve the performance of the metamaterial and is also convenient for processing to obtain the metamaterial.

[0066] In this embodiment, the preparation materials of the first dielectric layer, the second dielectric layer, and the third dielectric layer include polyimide. Polyimide has flexibility, insulation properties, a mature process, is easy to process, and is also a good medium for propagating terahertz electromagnetic waves.

[0067] As Figure 2 、 3 and shown in Figure 4, the embodiment of the present invention also provides an isolation performance test system, based on the isolator described in any one of the above, including two of the isolators, and the H-shaped metamaterials of the two isolators are sequentially placed on the same optical axis;

[0068] Terahertz electromagnetic waves are incident on one of the polarizers, and after transmission, the first linearly polarized light is formed. After passing through one of the H-shaped metamaterials, the first circularly polarized light is formed. After passing through another H-shaped metamaterial parallel to the previous one, the second linearly polarized light is formed. The polarization directions of the second linearly polarized light and the first linearly polarized light are perpendicular, and the second linearly polarized light is reflected out of the optical path by another polarizer.

[0069] Through the above method, the isolation effect at any incident angle can be measured. Even when the incident angle is 0, only by deflecting the angle of the polarizer behind the optical path, the second linearly polarized light can be reflected out of the optical path. Furthermore, the second linearly polarized light reflected out of the optical path can be tested, and by measuring the light intensity ratio of the reflected light and the incident light reflected out of the optical path, the isolation effect can be known. The linear polarization direction of the first linearly polarized light is the diagonal direction of the periodic unit of the H-shaped metamaterial. The isolation degree is obtained by testing the transmittance after passing through the combination of two groups of polarizers and the metamaterials placed in the same direction.

[0070] The directions of two adjacent sides of the square surface of the H-shaped metamaterial are the first direction and the second direction respectively. The transmittances of the second linearly polarized light in the first direction and the second direction are measured respectively, and the average of the two transmittances is calculated to obtain the insertion loss along the diagonal direction of the periodic unit of the H-shaped metamaterial.

[0071] The formula for determining the polarization state using the Jones matrix is as follows:

[0072]

[0073] Among them, E in , G1, and G2 respectively represent the qualitative Jones matrices of the linearly polarized wave LP passing through the polarizer, the quarter-wave plate QWP (fast axis along the y direction) of the metamaterial, and the reflection component. i is the imaginary unit. Due to the change in the propagation direction of the reflected light beam, the coordinate system changes. T represents the coordinate transformation matrix between the two coordinate systems. From E in and E r , it can be seen that the reflected linearly polarized wave LP wave is perpendicular to the polarization direction of the polarizer, so it cannot pass through the polarizer. Due to the limitation of the optical path of THz-TDS, the transmittances of two quarter-wave plates QWP of the metamaterial placed in the same direction were measured in the experiment. As Figure 2 shows, it is equivalent to Figure 1 's blocking reflection process, and the corresponding Jones matrix is as follows:

[0074]

[0075] It can be seen from Equation (1) and Equation (2) that the linearly polarized wave LP waves obtained by the two methods are consistent. Based on the above method, by passing through two consecutive quarter-wave plates QWP of the metamaterial, the transmittances of the linearly polarized wave LP at different incident angles are measured, and the blocking efficiency (the ratio of the optical power entering the blocking layer to the optical power exiting the blocking layer) is calculated.

[0076] In the Figure 1 and Figure 2 of the present invention, the metamaterial is composed of multiple periodic units. For the convenience of observation and understanding, in Figure 1 , 2 , a single periodic unit is used to represent the metamaterial.

[0077] In some embodiments of the present invention, the diameter of the wires of the wire grid is 8 - 12 μm, and the spacing between the wires of the wire grid is 25 - 35 μm.

[0078] In this embodiment, the polarizer made of the wire grid with the above parameters has a transmittance of 1 in the polarization direction and a transmittance of 0.005 in the direction perpendicular to the polarization direction.

[0079] In some embodiments of the present invention, the material for preparing the wires of the wire grid is tungsten wire.

[0080] In this embodiment, the wire grid made of tungsten wire has a high contrast ratio.

[0081] As Figure 7 , 8 shown, in some embodiments of the present invention, the incident angle of the terahertz electromagnetic wave is 40°, the insertion loss is 2.17 dB at 1.51 THz, the blocking bandwidth is 280 GHz at 1.37 THz to 1.65 THz, and the blocking efficiency is 20 dB.

[0082] In this embodiment, when the incident angle is 40°, the blocking efficiency of the system is relatively high.

[0083] In some embodiments of the present invention, the incident angle of the terahertz electromagnetic wave is 10°, the insertion loss is reduced to 1.65 dB at 1.51 THz, and the bandwidth of the 20 dB blocking efficiency is 170 GHz from 1.42 THz to 1.59 THz.

[0084] In this embodiment, when the incident angle is 10°, the insertion loss of the system is relatively small.

[0085] In this embodiment, the reflection unit in the transmission isolation system can be any optical device. When it is necessary to isolate the terahertz backlight reflection generated by the optical device, only a combination of a polarizer and an H-type metamaterial needs to be set in front of the optical device to isolate the terahertz backlight reflection.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A terahertz isolator based on H-shaped metamaterials, characterized in that, It includes an H-type metamaterial and a polarizer; The H-type metamaterial includes a plurality of periodic units, and the periodic units are periodically arranged in two directions where the adjacent unit edges are perpendicular to each other to form the metamaterial; The periodic unit is a cuboid including two square faces, and sequentially includes a first dielectric layer, a second dielectric layer, and a third dielectric layer along the thickness direction. H-type metal layers are provided on the faces of the second dielectric layer and the third dielectric layer facing the first dielectric layer; The H-type metamaterial is used to convert linearly polarized light into circularly polarized light or convert circularly polarized light into linearly polarized light; The polarizer includes a wire grid. The wire grid includes a plurality of wires parallel to each other in the same plane. Each wire of the wire grid is parallel to the diagonal of the periodic unit of the H-type metamaterial. The polarizer is used to transmit polarized light with a polarization direction perpendicular to the wires of the wire grid and reflect polarized light with a polarization direction parallel to the wires of the wire grid; Terahertz electromagnetic waves are incident on the polarizer. The terahertz electromagnetic waves pass through the polarizer to form first linearly polarized light. The first linearly polarized light passes through the H-type metamaterial to form first circularly polarized light. The first circularly polarized light is reflected by a subsequent optical device to form second circularly polarized light. The second circularly polarized light passes through the H-type metamaterial to form second linearly polarized light. The polarization directions of the first linearly polarized light and the second linearly polarized light are perpendicular. The rotation directions of the first circularly polarized light and the second circularly polarized light are opposite. The polarization direction of the second linearly polarized light is parallel to the wires of the wire grid and cannot pass through the polarizer, and is reflected by the polarizer to isolate the terahertz electromagnetic waves and prevent the reflected terahertz electromagnetic waves from affecting the incident light source.

2. The isolator according to claim 1, wherein The side length of the square face of the periodic unit is 50 - 70 μm, the thickness of the first dielectric layer is 3 - 7 μm, the thickness of the second dielectric layer is 15 - 25 μm, the thickness of the third dielectric layer is 5 - 15 μm, and the thickness of the H-type metal layer is 180 - 220 nm; The H-type metal layer includes two parallel first metal strips and a second metal strip connecting the midpoints of the two first metal strips. The lengths of the first metal strip and the second metal strip are both 30 - 42 μm, and the widths are both 2 - 4 μm.

3. The isolator according to claim 2, wherein The preparation material of the H-type metal layer includes gold; The preparation materials of the first dielectric layer, the second dielectric layer, and the third dielectric layer include polyimide.

4. An isolation performance test system, characterized in that, Based on the isolator according to any one of claims 1 - 3, it includes two such isolators, and the H-type metamaterials of the two isolators are sequentially placed on the same optical axis; Terahertz electromagnetic waves are incident on one polarizer. After transmission, the first linearly polarized light is formed. The first linearly polarized light passes through one H-type metamaterial to form the first circularly polarized light. The first circularly polarized light passes through another H-type metamaterial to form the second linearly polarized light. The polarization direction of the second linearly polarized light is perpendicular to that of the first linearly polarized light, and the second linearly polarized light is reflected out of the optical path by another polarizer; The isolation effect can be known by measuring the light intensity ratio of the second linearly polarized light reflected out of the optical path to the incident light. The linear polarization direction of the first linearly polarized light is the diagonal direction of the periodic unit of the H-type metamaterial. The isolation degree is obtained by testing the electromagnetic wave transmittance through two such isolators.

5. The system according to claim 4, wherein The directions of two adjacent sides of the square surface of the H-type metamaterial are the first direction and the second direction respectively. The transmittances of the second linearly polarized light in the first direction and the second direction are measured respectively, and the average of the two transmittances is calculated to obtain the insertion loss along the diagonal direction of the periodic unit of the H-type metamaterial.

6. The system according to claim 4, characterized in that, The diameter of the wires of the wire grid is 8 - 12 μm, and the interval between the wires of the wire grid is 25 - 35 μm.

7. The system according to claim 4, wherein The material for preparing the wires of the wire grid is tungsten wire.

8. The system according to claim 4, characterized in that The incident angle of the terahertz electromagnetic wave is 40°. The insertion loss is 2.17 dB at 1.51 THz, the blocking bandwidth is 280 GHz at 1.37 THz - 1.65 THz, and the blocking efficiency is 20 dB.

9. The system according to claim 4, characterized in that, The incident angle of the terahertz electromagnetic wave is 10°. The insertion loss is reduced to 1.65 dB at 1.51 THz, and the bandwidth with a blocking efficiency of 20 dB is 170 GHz at 1.42 THz to 1.59 THz.

Images