CN113764961A - Small hemispherical structure terahertz dual-function device and method thereof - Google Patents
Small hemispherical structure terahertz dual-function device and method thereof Download PDFInfo
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Abstract
The invention discloses a terahertz dual-function device with a small hemispherical structure and a method thereof. The terahertz wave detector comprises a terahertz wave input end, a laser input end and N multiplied by N square unit structures, wherein N is a natural number, and the N multiplied by N square unit structures are periodically arranged on a plane vertical to the terahertz wave input direction; the unit structure comprises a substrate metal plate, a small hemispheroid medium layer and a double-layer mixed material ring attached to the medium layer; wherein the small semi-sphere medium layer is positioned above the substrate metal plate. The small hemispherical structure terahertz dual-function device has the characteristics of convenience in manufacturing, convenience in adjustment and absorption, large cross polarization conversion rate bandwidth, multiple functions and the like, and meets the application requirements of a terahertz wave system.
Description
Technical Field
The invention relates to a terahertz multifunctional device, in particular to a terahertz bifunctional device with a small hemispherical structure and a method thereof.
Background
Terahertz generally refers to electromagnetic waves with a frequency within the range of 0.1-10 THz, the frequency of the electromagnetic waves is between infrared and microwave, and the electromagnetic waves are transition regions of macroscopic electronics and microscopic photonics. Terahertz waves are in a special position in the electromagnetic spectrum because of being between the electromagnetic field and the quantum field. This also makes it an internationally recognized leading technology. Terahertz waves have the characteristics of high permeability, low energy, fingerprint spectrum, wide frequency band, short wavelength, strong water absorption and the like, and the properties enable the practical application of terahertz waves to be very wide, such as medical diagnosis, communication, imaging, space astronomy, security inspection and the like. Limited by the defects of the terahertz wave generation and detection method, people have little knowledge on the electromagnetic radiation property of the terahertz wave band in the past. With the generation and breakthrough of corresponding technologies, terahertz waves draw the attention of researchers by virtue of their unique advantages. Nowadays, terahertz science and technology has become a must path for technological development.
In recent years, terahertz devices have been provided with various functions such as absorption, filtering, switching, polarization conversion, and the like.
The terahertz functional devices have wide application prospects in terahertz wave application fields such as terahertz radars, terahertz communication, terahertz wave imaging and the like. However, the existing terahertz functional device is complex in structure, single in function and high in manufacturing cost, and not only has severe requirements on a processing technology and a processing environment, but also is difficult to meet the requirements of practical application. Therefore, a terahertz device which is simple in structure and multifunctional and can be switched is urgently needed to be researched to meet the application requirement of the terahertz system.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a small hemispheric terahertz dual-function device and a method thereof, wherein the absorption bandwidth is up to 6.04THz, and the cross polarization conversion rate bandwidth is 3.33 THz.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a terahertz dual-function device with a small hemispherical structure comprises an NxN square periodic unit structure, wherein N is a natural number; the NxN square periodic unit structures are arranged on a plane vertical to the input direction of the terahertz waves; each square periodic unit structure comprises a substrate metal plate, a small hemispheroid dielectric layer, a lower layer circular ring and an upper layer circular ring, wherein the lower layer circular ring and the upper layer circular ring are attached to the small hemispheroid dielectric layer; the shape of the small hemispheroid medium layer is a segment obtained by cutting a section of height of a hemispheroid by a plane parallel to the bottom surface, and the bottom surface of the small hemispheroid medium layer is arranged on the square substrate metal plate;
the lower layer circular ring and the upper layer circular ring are two circular rings with the inner surfaces tightly attached to the small hemispheroid medium layer, and are obtained by cutting a hollow hemispherical shell by three parallel planes, wherein the upper layer circular ring is formed between the upper two planes, and the lower layer circular ring is formed between the lower two planes;
the lower-layer circular ring is cut into a first lower-layer ring piece, a third lower-layer ring piece and two second lower-layer ring pieces by a first cuboid and a second cuboid, the two second lower-layer ring pieces are positioned outside the first cuboid and the second cuboid, and the four lower-layer ring pieces are continuously spliced end to end;
the upper-layer circular ring is cut into a first upper-layer ring piece, a third upper-layer ring piece and two second upper-layer ring pieces by a third cuboid and a fourth cuboid, the two second upper-layer ring pieces are positioned outside the third cuboid and the fourth cuboid, and the four upper-layer ring pieces are continuously spliced end to end;
wherein the major axis of first cuboid, the second cuboid, the equal perpendicular to substrate metal sheet of third cuboid and fourth cuboid, a side of four cuboid width direction overlaps in same plane, and the central perpendicular line of substrate metal sheet is located the face that overlaps of four cuboids, first lower floor's ring piece and first upper ring piece all are located one side of this face that overlaps, third lower floor's ring piece and third upper ring piece all are located the opposite side of this face that overlaps, square periodic cell structure uses the perpendicular at a diagonal place of substrate metal sheet to be the mirror symmetry structure as the center.
Preferably, in the small hemispheroid dielectric layer, the segment is obtained by cutting off a hemisphere with the radius of 9-10 μm by the height of 0.2-0.8 μm.
Further, the material of the small hemispheroid dielectric layer is silicon dioxide.
Furthermore, the outer radius of the upper surface of the lower layer ring is 4.8-5.2 μm, the outer radius of the lower surface of the lower layer ring is 7.2-7.6 μm, the thickness of the lower layer ring in the sphere diameter direction is 0.4-0.6 μm, the width of a first cuboid formed by cutting the first lower layer ring sheet is 3-7 μm, and the width of a second cuboid formed by cutting the third lower layer ring sheet is 10-15 μm.
Furthermore, in the lower ring, the first lower ring and the third lower ring are made of photoconductive silicon, and the second lower ring is made of gold.
Furthermore, the outer radius of the upper surface of the upper layer ring is 7.2-7.6 μm, the outer radius of the lower surface of the upper layer ring is 8.2-8.6 μm, the thickness of the upper layer ring in the sphere diameter direction is 0.4-0.6 μm, the width of a third cuboid formed by cutting the first upper layer ring sheet is 10-15 μm, and the width of a fourth cuboid formed by cutting the third upper layer ring sheet is 3-7 μm.
Furthermore, in the upper-layer circular ring, the first upper-layer ring piece and the third upper-layer ring piece are made of gold, and the second upper-layer ring piece is made of photoconductive silicon.
Furthermore, the substrate metal plate is gold, and the side length is 20-22 μm. The thickness is 1-2 μm.
On the other hand, the invention provides a method for regulating and controlling the terahertz dual-function device with the small hemispherical structure, which comprises the following steps: the conductivity of the light-conducting silicon in the lower layer ring and the upper layer ring is changed by adjusting the intensity of the external laser, so that the adjustable and switchable function of absorption polarization conversion is realized.
Preferably, when terahertz waves are input from the terahertz wave input end, under the condition that the lower-layer ring and the upper-layer ring are provided with additional laser, the device obtains a 6.04THz bandwidth with the systemic yield of more than 90% in the range of 3.96 THz-10 THz; under the condition of no external laser, the device obtains a 3.33THz bandwidth with the cross polarization conversion rate of over 90% in the range of 3.88-7.21 THz, the cross polarization conversion rate of over 99% in the range of 4.02-4.97 THz and 6.07-7.03 THz, and the sum of the bandwidths is 1.91 THz; when the incident angle of the terahertz wave is changed and adjusted within the range of 0-50 degrees, the device keeps more than 90% of absorption rate and cross polarization conversion rate; in the process of changing the external laser intensity of the lower-layer ring and the upper-layer ring, the device has the variability of absorptivity within the range of 18% -94% and the variability of cross polarization conversion rate within the range of 1% -99%.
The terahertz dual-function device with the small hemispherical structure has the characteristics of simple and compact structure, adjustable and switchable absorption rate and cross polarization conversion rate, large absorption and cross polarization conversion rate bandwidth and the like, and meets the application requirements in the fields of terahertz wave imaging, medical diagnosis, sensing, communication and the like.
Drawings
FIG. 1 is a two-dimensional plan view and a three-dimensional unit structure view of a terahertz dual-function device with a small hemispherical structure;
FIG. 2 is a top view of a lower ring of a terahertz dual-function device with a small hemispherical structure on a small hemispherical dielectric layer;
FIG. 3 is a top view of an upper layer ring of the terahertz dual-function device with a small hemispheroid structure on a small hemispheroid dielectric layer;
FIG. 4 is an optimal absorption spectrum diagram of a terahertz dual-function device with a small hemispherical structure;
FIG. 5 is a graph of an optimal cross-polarization conversion rate spectrum of a terahertz dual-function device with a small hemispherical structure;
FIG. 6 is a graph of absorbance contrast of different conductivities of photoconductive silicon of a terahertz dual-function device with a small hemispherical structure;
FIG. 7 is a cross-polarization conversion ratio comparison graph of different conductivities of photoconductive silicon of a terahertz dual-function device with a small hemispherical structure;
FIG. 8 is an absorption rate contrast diagram of a small hemispherical structure terahertz dual-function device at different incident angles;
fig. 9 is a cross polarization conversion ratio comparison graph of different incident angles of the terahertz dual-function device with the small hemispherical structure.
Detailed Description
As shown in fig. 1, the present invention provides a terahertz dual-function device with a small hemispherical structure, which includes N × N square periodic unit structures 1, a terahertz wave input end 2 and a laser input end 3; the N multiplied by N square periodic unit structures 1 are arranged on a plane perpendicular to the input direction of the terahertz wave, N is a natural number, the specific number is not limited, and the square periodic unit structures are continuously arranged according to the area required by the device.
Each square periodic unit structure 1 has the same structural form and comprises a substrate metal plate 7, a small hemispheroid dielectric layer 4, and a lower layer circular ring 5 and an upper layer circular ring 6 which are attached to the small hemispheroid dielectric layer 4. The shape of the small hemispheroid medium layer 4 is a segment shape, and the segment shape is obtained by cutting a hemisphere by a plane parallel to the bottom surface of the hemisphere, and the segment is smaller than the hemisphere, so the small hemispheroid is called as a small hemispheroid in the invention. The bottom surface of the small hemispheroid dielectric layer 4 is arranged on a substrate metal plate 7 with a square plane, and the center of the bottom surface of the small hemispheroid dielectric layer is superposed with the center of the upper surface of the substrate metal plate 7.
The lower layer ring 5 and the upper layer ring 6 are two rings with inner surfaces tightly attached to the small hemispheroid medium layer 4, the two rings are ring bodies with space curvature, and the forming mode is as follows: a hollow hemispherical shell is cut by utilizing three parallel planes with a certain interval, two ring bodies can be obtained after two parts of the top and the bottom are removed, wherein an upper ring 6 is formed between the two planes at the upper part, and a lower ring 5 is formed between the two planes at the lower part. It should be noted that, in order to ensure that the inner surfaces of the lower ring 5 and the upper ring 6 can be attached to the small hemispheric medium layer 4 to obtain an outer surface, the inner diameter of the hollow hemispherical shell should be equal to the outer diameter of the small hemispheric medium layer 4.
In addition, lower floor ring 5 is cut into four sections lower floor ring pieces by first cuboid and second cuboid, including one section first lower floor ring piece 8, one section third lower floor ring piece 10 and two sections second lower floor ring pieces 9, first lower floor ring piece 8 and third lower floor ring piece 10 are located first cuboid and second cuboid respectively, and two sections second lower floor ring pieces 9 all are located outside first cuboid and the second cuboid, and four sections lower floor ring pieces meet end to end and splice in succession and have formed lower floor ring 5. It should be noted that the aforementioned first rectangular parallelepiped and second rectangular parallelepiped are introduced only for illustrating the segmented form of the four segments of the lower ring 5, but are not constituent components of the lower ring 5. The long axes (i.e., the central axes parallel to the longitudinal direction) of the first rectangular parallelepiped and the second rectangular parallelepiped are perpendicular to the substrate metal plate 7, and one side surface in the width direction between the two rectangular cuboids is overlapped, and the two rectangular cuboids are respectively located on both sides of the overlapped surface. Thus, the first lower ring piece 8 is substantially the intersection of the first rectangular parallelepiped and the lower ring 5, the third lower ring piece 10 is substantially the intersection of the second rectangular parallelepiped and the lower ring 5, and the remaining non-intersected portions of the lower ring 5 form two second lower ring pieces 9.
Similarly, the upper ring 6 is cut into four sections of upper ring pieces by a third cuboid and a fourth cuboid, and comprises a first upper ring piece 11, a third upper ring piece 13 and two sections of second upper ring pieces 12, wherein the first upper ring piece 11 and the third upper ring piece 13 are respectively positioned in the third cuboid and the fourth cuboid, the two sections of second upper ring pieces 12 are respectively positioned outside the third cuboid and the fourth cuboid, and the four sections of upper ring pieces are spliced continuously end to form the upper ring 6. It should also be noted that the aforementioned third and fourth cuboids are introduced only for illustrating the segmented form of the four segments in the upper ring 6, but are not constituent parts of the upper ring 6. The long axes (i.e., the central axes parallel to the longitudinal direction) of the third rectangular parallelepiped and the fourth rectangular parallelepiped are also perpendicular to the substrate metal plate 7, and one side surface in the width direction between the two rectangular cuboids is also overlapped, and the two rectangular cuboids are respectively located on both sides of the overlapped surface. Therefore, the first upper ring piece 11 is substantially the intersection part of the third cuboid and the upper ring 6, the third upper ring piece 13 is substantially the intersection part of the fourth cuboid and the upper ring 6, and the remaining non-intersection part of the upper ring 6 forms two sections of the second upper ring pieces 12.
The entire square periodic cell structure 1 is a mirror-symmetrical structure whose mirror-symmetrical center plane is a vertical plane perpendicular to the substrate metal plate 7, and a diagonal line of the substrate metal plate 7 is in the vertical plane. Therefore, one side surfaces in the width direction of the first rectangular solid, the second rectangular solid, the third rectangular solid, and the fourth rectangular solid are virtually all overlapped in the same plane, and the central perpendicular line of the substrate metal plate 7 is located in the overlapped plane common to the four rectangular solids, which is perpendicular to the central plane of the aforementioned mirror symmetry. The first lower ring 8 and the first upper ring 11 are located on one side of the overlapping surface, and the third lower ring 10 and the third upper ring 13 are located on the other side of the overlapping surface.
In the square periodic unit structure 1, a terahertz wave input end 2 is arranged right above the structure, terahertz waves can be incident at a certain deflection angle, a laser input end 3 is arranged at the positions of a lower-layer circular ring 5 and an upper-layer circular ring 6, and the concentration of light guide silicon carriers in the lower-layer circular ring 5 and the upper-layer circular ring 6 is changed by changing the intensity of external laser, so that the conductivity of the light guide silicon carriers is changed rapidly, and the adjustable and switchable function of absorption polarization conversion is realized.
In the terahertz bifunctional device with the small hemispherical structure, the specific structural parameters and materials of each part can adopt the following forms: in the small hemispheroid dielectric layer 4, the corresponding segment is obtained by cutting off a hemispheroid with the radius of 9-10 mu m by the height of 0.2-0.8 mu m. The material of the small hemispheroid dielectric layer 4 is silicon dioxide. The upper surface outer radius of the lower layer ring 5 is 4.8 to 5.2 μm, the lower surface outer radius is 7.2 to 7.6 μm, the thickness in the spherical diameter direction (i.e. the thickness of the hollow hemispherical shell) is 0.4 to 0.6 μm, the width of the first cuboid cut to form the first lower layer ring piece 8 is 3 to 7 μm, and the width of the second cuboid cut to form the third lower layer ring piece 10 is 10 to 15 μm. In the lower ring 5, the first lower ring 8 and the third lower ring 10 are made of photoconductive silicon, and the second lower ring 9 is made of gold. The upper surface outer radius of the upper layer ring 6 is 7.2-7.6 μm, the lower surface outer radius is 8.2-8.6 μm, the thickness in the sphere diameter direction (i.e. the thickness of the hollow hemispherical shell) is 0.4-0.6 μm, the width of the third cuboid cutting the first upper layer ring piece 11 is 10-15 μm, and the width of the fourth cuboid cutting the third upper layer ring piece 13 is 3-7 μm. In the upper layer circular ring 6, the material of the first upper layer ring sheet 11 and the third upper layer ring sheet 13 is gold, and the material of the second upper layer ring sheet 12 is photoconductive silicon. The substrate metal plate 4 is gold, and the side length is 20-22 μm. The thickness is 1-2 μm.
The method for regulating and controlling the small-hemisphere terahertz dual-function device changes the conductivity of photoconductive silicon in the lower-layer circular ring 5 and the upper-layer circular ring 6 by regulating the intensity of external laser, and realizes the function of adjustable and switchable absorption polarization conversion. In the subsequent embodiment of the invention, when terahertz waves are input from the terahertz wave input end 1, under the condition that the lower layer ring 5 and the upper layer ring 6 have external laser, namely the conductivity sigma of the photoconductive silicon is 10000S/m, the device obtains a 6.04THz bandwidth with the systemic yield of over 90% in the range of 3.96THz to 10 THz; under the condition of no external laser, namely when the electrical conductivity sigma of the photoconductive silicon is 0.00025S/m, the device obtains a 3.33THz bandwidth with the cross polarization conversion rate of over 90 percent in the range of 3.88 to 7.21THz, and the cross polarization conversion rate of over 99 percent in the ranges of 4.02 to 4.97THz and 6.07 to 7.03THz, and the total bandwidth is 1.91 THz; when the incident angle of the terahertz wave is changed and adjusted within the range of 0-50 degrees, the device keeps more than 90% of absorption rate and cross polarization conversion rate; during the change of the external laser intensity of the lower ring 5 and the upper ring 6, the device has the variability of the absorptivity within the range of 18% -94% and the variability of the cross polarization conversion rate within the range of 1% -99%.
The following explains specific technical effects of the terahertz dual-function device based on the small hemispherical structure by embodiments.
Example 1
In this embodiment, the structure and the shapes of the components of the terahertz dual-function device with the small hemispherical structure are as described above, and therefore are not described in detail. However, the specific parameters of each component are as follows:
in the small hemispheroid dielectric layer 4, the corresponding segment is obtained by cutting off a hemispheroid with the radius of 9.5 mu m by the height of 0.5 mu m. The material of the small hemispheroid dielectric layer 4 is silicon dioxide. The upper surface outside radius of the lower ring 5 is 5.0 μm, the lower surface outside radius is 7.4 μm, the thickness in the spherical diameter direction is 0.5 μm, the width of the first rectangular parallelepiped formed by cutting the first lower ring piece 8 is 5 μm, and the width of the second rectangular parallelepiped formed by cutting the third lower ring piece 10 is 12 μm. In the lower ring 5, the first lower ring 8 and the third lower ring 10 are made of photoconductive silicon, and the second lower ring 9 is made of gold. The upper surface outside radius of the upper layer ring 6 is 7.5 μm, the lower surface outside radius is 8.4 μm, the thickness in the spherical diameter direction is 0.5 μm, the width of the third rectangular parallelepiped cut to form the first upper layer ring piece 11 is 12 μm, and the width of the fourth rectangular parallelepiped cut to form the third upper layer ring piece 13 is 5 μm. In the upper layer circular ring 6, the material of the first upper layer ring sheet 11 and the third upper layer ring sheet 13 is gold, and the material of the second upper layer ring sheet 12 is photoconductive silicon. The substrate metal plate 4 is gold with a side length of 20 μm. The thickness was 1 μm.
The absorber changes the conductivity of the photoconductive silicon by changing the intensity of the external laser, thereby achieving the function of adjustable and switchable absorption polarization conversion. Because the metal plate is arranged on the bottom layer of the small hemispheric terahertz dual-function device, terahertz waves cannot be transmitted out. All performance indexes of the terahertz dual-function device with the small hemispherical structure are obtained by simulation calculation through CST STUDIO SUITE 2019 software. Fig. 4 is a diagram of the optimal absorption performance of the terahertz dual-function device with a small hemispherical structure, when terahertz waves are input from the terahertz wave input end, the device is in an absorption mode under the condition that laser is applied to the upper and lower annular layers, that is, the optical guide silicon conductivity σ is 10000S/m, and at this time, the absorption rate exceeds 90% in the bandwidth range of 3.96 THz-10.00 THz, and the bandwidth can reach 6.04 THz. Fig. 5 is a spectrogram of the optimal cross polarization conversion rate of the terahertz dual-function device with the small hemispherical structure, the device is in a cross polarization conversion mode under the condition that no laser is applied to the upper and lower annular layers, that is, when the conductivity σ of the photoconductive silicon is 0.00025S/m, the cross polarization conversion rate exceeds 90% in the bandwidth range of 3.88THz to 7.21THz, the bandwidth of the device can reach 3.33THz, wherein the cross polarization conversion rate exceeds 99% in the bandwidth ranges of 4.02 to 4.97THz and 6.07 to 7.03THz, and the sum of the bandwidths is 1.91 THz. Fig. 6 is an absorption rate comparison graph of different conductivities of photoconductive silicon of the terahertz dual-function device with the small hemispherical structure, when the external laser condition of the upper and lower annular layers is changed, the conductivity of the photoconductive silicon is rapidly changed due to the change of the carrier concentration of the photoconductive silicon, and the graph shows that the absorption performance of the terahertz dual-function device in the absorption mode is firstly increased and then decreased along with the decrease of the conductivity, the absorption rate can reach 18% at most in the range of 3.96THz to 10.00THz, and at the moment, the absorption rate adjustability of 18% to 94% is obtained by the absorber. Fig. 7 is a cross polarization conversion rate comparison graph of different conductivities of photoconductive silicon of the small hemispherical structure terahertz dual-function device, and it can be known from the graph that the cross polarization conversion rate of the device in the cross polarization conversion mode increases with the decrease of the conductivity, the cross polarization conversion rate can reach 1% at least in the range of 3.88THz to 7.21THz, and at this time, the absorber obtains the adjustability of the cross polarization conversion rate of 1% to 99%. FIG. 8 is an absorption rate comparison graph of different incident angles of the small hemispherical structure terahertz dual-function device, and when the incident angle of terahertz waves is changed within the range of 0-50 degrees, the small hemispherical structure terahertz dual-function device can ensure that more than 90% of absorption rate exists within the bandwidth range; fig. 9 is a cross polarization conversion rate comparison graph of different incident angles of the small hemispherical structure terahertz dual-function device, and when the incident angle of terahertz waves is changed within the range of 0-80 degrees, the small hemispherical structure terahertz dual-function device can ensure the existence of over 90% cross polarization conversion rate within the bandwidth range.
Claims (10)
1. A terahertz dual-function device with a small hemispherical structure is characterized by comprising N multiplied by N square periodic unit structures (1), wherein N is a natural number; the NxN square periodic unit structures (1) are arranged on a plane perpendicular to the input direction of the terahertz waves; each square periodic unit structure (1) comprises a substrate metal plate (7), a small hemispheroid dielectric layer (4), and a lower layer circular ring (5) and an upper layer circular ring (6) which are attached to the small hemispheroid dielectric layer (4); the shape of the small hemispheroid dielectric layer (4) is a segment obtained by cutting a hemisphere by a plane parallel to the bottom surface to obtain a section of height, and the bottom surface of the small hemispheroid dielectric layer (4) is arranged on a square substrate metal plate (7);
the lower-layer circular ring (5) and the upper-layer circular ring (6) are two circular rings with inner surfaces tightly attached to the small hemispherical medium layer (4), a hollow hemispherical shell is cut by three parallel planes, the upper-layer circular ring (6) is formed between the two upper planes, and the lower-layer circular ring (5) is formed between the two lower planes;
the lower-layer circular ring (5) is cut into a first lower-layer ring piece (8), a third lower-layer ring piece (10) and two second lower-layer ring pieces (9) by a first cuboid and a second cuboid, the two second lower-layer ring pieces (9) are positioned outside the first cuboid and the second cuboid, and the four lower-layer ring pieces are connected end to end and are continuously spliced;
the upper-layer circular ring (6) is cut into a first upper-layer ring piece (11), a third upper-layer ring piece (13) and two second upper-layer ring pieces (12) by a third cuboid and a fourth cuboid, the two second upper-layer ring pieces (12) are positioned outside the third cuboid and the fourth cuboid, and the four upper-layer ring pieces are connected end to end and are continuously spliced;
wherein first cuboid, the second cuboid, the equal perpendicular to substrate metal sheet (7) of the long axis of third cuboid and fourth cuboid, a side of four cuboid width direction overlaps in same plane, and the central perpendicular of substrate metal sheet (7) is located the face that overlaps of four cuboids, first lower floor's ring piece (8) and first upper ring piece (11) all are located one side of this face that overlaps, third lower floor's ring piece (10) and third upper ring piece (13) all are located the opposite side of this face that overlaps, square periodic cell structure (1) is the mirror symmetry structure as the center with the perpendicular face at a diagonal place of substrate metal sheet (7).
2. The terahertz bifunctional device with a small hemispherical structure as claimed in claim 1, wherein in the small hemispherical dielectric layer (4), the segment is obtained by cutting off a hemisphere with a radius of 9 μm to 10 μm by a height of 0.2 μm to 0.8 μm.
3. The terahertz bifunctional device with a small hemispheroid structure as claimed in claim 2, wherein the material of the small hemispheroid dielectric layer (4) is silicon dioxide.
4. The terahertz bifunctional device with a small hemispherical structure as claimed in claim 3, wherein the upper surface of the lower ring (5) has an outer radius of 4.8 μm to 5.2 μm, the lower surface has an outer radius of 7.2 μm to 7.6 μm, the thickness in the spherical radial direction is 0.4 μm to 0.6 μm, the width of a first rectangular parallelepiped for cutting to form the first lower ring (8) is 3 μm to 7 μm, and the width of a second rectangular parallelepiped for cutting to form the third lower ring (10) is 10 μm to 15 μm.
5. The terahertz bifunctional device with a small hemispherical structure as claimed in claim 4, wherein in the lower ring (5), the material of the first lower ring (8) and the third lower ring (10) is photoconductive silicon, and the material of the second lower ring (9) is gold.
6. The terahertz bifunctional device with a small hemispherical structure as claimed in claim 5, wherein the upper surface of the upper ring (6) has an outer radius of 7.2 μm to 7.6 μm, the lower surface has an outer radius of 8.2 μm to 8.6 μm, the thickness in the spherical radial direction is 0.4 μm to 0.6 μm, the width of the third cuboid cut to form the first upper ring (11) is 10 μm to 15 μm, and the width of the fourth cuboid cut to form the third upper ring (13) is 3 μm to 7 μm.
7. The terahertz bifunctional device with a small hemispherical structure as claimed in claim 6, wherein in the upper ring (6), the material of the first upper ring (11) and the third upper ring (13) is gold, and the material of the second upper ring (12) is photoconductive silicon.
8. The terahertz bifunctional device with a small hemispherical structure as claimed in claim 7, wherein the substrate metal plate (4) is gold, and the side length is 20 μm-22 μm. The thickness is 1-2 μm.
9. A regulation and control method of a small hemispherical structure terahertz double-function device as claimed in claim 1 is characterized in that the conductivity of photoconductive silicon in the lower layer circular ring (5) and the upper layer circular ring (6) is changed by adjusting the intensity of external laser, so that the adjustable switchable function of absorption polarization conversion is realized.
10. The control method according to claim 9, wherein when the terahertz wave is input from the terahertz wave input end (1), the device obtains a 6.04THz bandwidth with a systemic yield exceeding 90% in a range of 3.96THz to 10THz under the condition that the lower ring (5) and the upper ring (6) have additional laser; under the condition of no external laser, the device obtains a 3.33THz bandwidth with the cross polarization conversion rate of over 90% in the range of 3.88-7.21 THz, the cross polarization conversion rate of over 99% in the range of 4.02-4.97 THz and 6.07-7.03 THz, and the sum of the bandwidths is 1.91 THz; when the incident angle of the terahertz wave is changed and adjusted within the range of 0-50 degrees, the device keeps more than 90% of absorption rate and cross polarization conversion rate; the device has an absorptivity variability in the range of 18% -94% and a cross polarization conversion rate variability in the range of 1% -99% during the change of the applied laser intensity of the lower layer circular ring (5) and the upper layer circular ring (6).
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