1. A terahertz active super-surface amplitude type spatial modulator is characterized by comprising M multiplied by M pixel units arranged in an array;

each pixel unit comprises an MOS tube and a super-surface unit; the super-surface unit comprises N multiplied by N resonant super-structure units arranged in an array; the resonant superstructure unit comprises a metal layer, a phase change material layer, a dielectric layer and a resonant module; the MOS tube is connected with the metal layer;

and controlling the reflection state of the super-surface unit by controlling the conduction condition of the MOS tube.

2. The terahertz active super-surface amplitude type spatial modulator of claim 1, wherein the orthographic projection of the super-surface units is square, and the distance between two adjacent super-surface units is 100 μm;

the orthographic projection of the resonant super-structure unit is square, the side length is a mu m, and the side length of the square orthographic projection of the super-surface unit is a multiplied by N mu m.

3. The terahertz active super-surface amplitude type spatial modulator of claim 1, wherein a first surface of the phase change material layer is connected with the metal substrate layer, a second surface of the phase change material layer is connected with the dielectric layer, and the resonance module is disposed on the dielectric layer.

4. The terahertz active super-surface amplitude type spatial modulator of claim 3, wherein the resonance module comprises a first circular cylinder and a second circular cylinder; the first circular cylinder and the second circular cylinder are concentric and have the same height.

5. The terahertz active super-surface amplitude type spatial modulator according to claim 1, wherein in the M x M array, the gates of the MOS transistors in the same row are connected, and the sources of the MOS transistors in the same column are connected;

and the drain electrode of the MOS tube is connected to the side surface of the metal layer of the corresponding super-surface unit.

6. The terahertz active super-surface amplitude type spatial modulator according to claim 2, wherein the side length of the square orthographically projected by the resonant super-structure unit is 49-51 μm.

7. The terahertz active super-surface amplitude type spatial modulator according to claim 4, wherein the outer circle radius of the first circular cylinder is 20.5-21.5 μm, and the inner circle radius is 14.5-15.5 μm;

the outer circle radius of the second circular cylinder is 9.5-10.5 mu m, and the inner circle radius is 3.5-4.5 mu m;

the thickness of the circular cylinder is 0.15-0.25 μm.

8. The terahertz active super-surface amplitude type spatial modulator of claim 1, wherein the metal layer is made of gold, and the phase change material layer is made of Ge₂Sb₂Te₅The dielectric layer is made of SiO 2.

9. The terahertz active super-surface amplitude type spatial modulator of claim 8, wherein the thickness of the phase change material layer is 1.95-2.05 μm, and the thickness of the dielectric layer is 0.95-1.05 μm.

10. The terahertz active super-surface amplitude type spatial modulator of claim 1, wherein the phase change material Ge is₂Sb₂Te₅The node constant in the amorphous state is ε_a18.0+0.01i, phase change material Ge₂Sb₂Te₅Dielectric constant in the crystalline state of epsilon_cThe relative dielectric constant of the dielectric layer is 3.9 ═ 33.0+6.00 i.

Background

The terahertz wave is electromagnetic wave with frequency of 0.1-10 THz, wavelength of 3000-30 μm, and has the characteristics of strong penetrability, unique characteristic spectral line for biological macromolecules, no ionizing radiation to human body, and the like. The characteristics have very wide application prospect in the fields of human body security inspection, medical imaging and the like. One of the key technologies that restrict the development of terahertz technology is a terahertz wave control device. The device can be combined with a super-surface technology to further realize effective terahertz wave regulation and control. The super-surface is a structure array which is artificially designed and arranged in a periodic form and has sub-wavelength thickness, the electromagnetic wave is regulated and controlled through the interaction of the structure and incident light, and the super-surface has unique material characteristics such as negative magnetic conductivity, negative refractive index and negative dielectric constant. Initial research focused primarily on passive super-surface areas, where the electromagnetic properties of the device were fixed once the device was fabricated, and lack of flexibility. In order to solve the above problems and improve the utility of the super-surface, researchers have proposed the preparation of super-surface devices with actively tunable or reconfigurable functions, and it is desirable to further enhance the flexibility of the super-surface, such as the incorporation of phase change materials.

In the field of terahertz imaging, a spatial light modulator is crucial, active super-surface modulation and arrayed single-pixel imaging need to be combined for preparing the device, and if modulation on a single pixel point is not considered, a required pattern is difficult to generate autonomously, so that the arrayed super-surface device and a single-pixel imaging technology are combined to modulate the amplitude of a terahertz wave wavefront, and further the compression sensing technology is combined to process various patterns, so that the device has a great development prospect. Therefore, it is very important to design a spatial light modulator capable of being controlled in an array mode.

Disclosure of Invention

In order to solve at least one of the technical problems in the prior art to a certain extent, the present invention aims to provide a terahertz active super-surface amplitude type spatial modulator.

The technical scheme adopted by the invention is as follows:

a terahertz active super-surface amplitude type spatial modulator comprises M multiplied by M pixel units arranged in an array;

each pixel unit comprises an MOS tube and a super-surface unit; the super-surface unit comprises N multiplied by N resonant super-structure units arranged in an array; the resonant superstructure unit comprises a metal layer, a phase change material layer, a dielectric layer and a resonant module; the MOS tube is connected with the metal layer;

and controlling the reflection state of the super-surface unit by controlling the conduction condition of the MOS tube.

Further, the orthographic projection of the super-surface unit is square, and the distance between two adjacent super-surface units is 100 micrometers;

the orthographic projection of the resonant super-structure unit is square, the side length is a mu m, and the side length of the square orthographic projection of the super-surface unit is a multiplied by N mu m.

Further, the first surface of the phase change material layer is connected with the metal substrate layer, the second surface of the phase change material layer is connected with the dielectric layer, and the resonance module is arranged on the dielectric layer.

Further, the resonance module comprises a first circular cylinder and a second circular cylinder; the first circular cylinder and the second circular cylinder are concentric and have the same height.

Furthermore, in the M multiplied by M array, the grid electrodes of the MOS tubes in the same row are connected, and the source electrodes of the MOS tubes in the same column are connected;

and the drain electrode of the MOS tube is connected to the side surface of the metal layer of the corresponding super-surface unit.

Further, the side length of a square orthographically projected by the resonant superstructure unit is 49-51 μm.

Further, the outer circle radius of the first circular cylinder is 20.5-21.5 μm, and the inner circle radius is 14.5-15.5 μm;

the outer circle radius of the second circular cylinder is 9.5-10.5 mu m, and the inner circle radius is 3.5-4.5 mu m;

the thickness of the circular cylinder is 0.15-0.25 μm.

Further, the metal layer is made of gold, and the phase change material layer is made of Ge₂Sb₂Te₅The dielectric layer is made of SiO 2.

Further, the thickness of the phase change material layer is 1.95-2.05 μm, and the thickness of the dielectric layer is 0.95-1.05 μm.

Further, the phase change material Ge₂Sb₂Te₅The node constant in the amorphous state is ε_a18.0+0.01i, phase change material Ge₂Sb₂Te₅Dielectric constant in the crystalline state of epsilon_cThe relative dielectric constant of the dielectric layer is 3.9 ═ 33.0+6.00 i.

Further, the thickness of the metal layer is 1 μm, the thickness of the phase change material layer is 2 μm, the thickness of the dielectric layer is 1 μm, and the height of the circular cylinder is 0.2 μm.

The invention has the beneficial effects that: the super-surface unit can switch crystalline state and amorphous state through on-off control of the MOS tube, is convenient to apply to terahertz image generation through a subsequent modulation means, generates reflected electromagnetic intensity or energy spatial distribution, and receives and obtains a pattern with inconsistent light and shade distribution of pixel points through a detector, thereby realizing spatial amplitude modulation of terahertz wave front.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description is made on the drawings of the embodiments of the present invention or the related technical solutions in the prior art, and it should be understood that the drawings in the following description are only for convenience and clarity of describing some embodiments in the technical solutions of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic structural view of an M × M arrayed super-surface in an embodiment of the present invention;

FIG. 2 is a schematic structural view of a single super-surface unit in an embodiment of the invention;

FIG. 3 is a schematic structural diagram of a single resonant superstructure unit in an embodiment of the present invention;

FIG. 4 is a surface current vector diagram of a super-surface at 1.133THz in an embodiment of the invention;

FIG. 5 is a surface current vector diagram of the top surface of the metal underlayer at 1.133THz in an embodiment of the present invention;

FIG. 6 is a surface current vector diagram of a super-surface at 2.840THz in an embodiment of the invention;

FIG. 7 is a surface current vector diagram at 2.840THz for the top surface of the metal underlayer in an embodiment of the present invention;

FIG. 8 is a graph illustrating reflectivity after phase transformation of a super-surface in an embodiment of the present invention;

FIG. 9 is a schematic diagram of a simulation of super-surface heating in an embodiment of the present invention;

FIG. 10 is a schematic diagram of ideal imaging or spatial modulation of a cross binary image in an embodiment of the invention;

FIG. 11 is a diagram illustrating a structural relationship between a pixel unit and a resonant superstructure unit according to an embodiment of the present invention.

Reference numerals: 1. metal layer, 2, phase change material layer, 3, dielectric layer, 4, resonance module.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention. The step numbers in the following embodiments are provided only for convenience of illustration, the order between the steps is not limited at all, and the execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.

Fig. 1 is a schematic structural diagram of a terahertz active super-surface array amplitude type spatial modulator based on a phase change medium according to an embodiment of the present invention, and the entire terahertz active super-surface array amplitude type spatial modulator is an M × M array, and each pixel unit has a constant interval, and the interval distance is 100 μ M. The pixel unit is composed of an MOS (metal oxide semiconductor) gating tube structure and an independent super surface, referring to fig. 11, the super surface in a single pixel unit is formed by periodically arranging an NxN resonant super structure unit array, and the super surface is arrayed to form the terahertz spatial modulator based on super surface amplitude regulation; the pixel cell size design is determined by the operating frequency or wavelength, and for 1.133THz, a single pixel size is designed to be 300 μm × 300 μm and is composed of a 6 × 6 resonant super-structural cell array (i.e., N ═ 6); therefore, the super surface of each pixel unit can be independently addressed and controlled, a certain super surface is gated by addressing and gating the transverse and longitudinal electrodes as row lines and column lines respectively to realize local electromagnetic regulation and control, and specifically, the MOS tube is controlled to conduct and heat Ge₂Sb₂Te₅(GST) which switches reflectivity between a large normal value and a minimum value at a resonance point when switching between the amorphous and crystalline states; when the reflectivity is at a minimum value, the corresponding selected unit can be regarded as an off state of the corresponding pixel, the intensity of the reflected light is extremely small and is represented by a number of 0; on the contrary, when the phase change control causes the reflection maximum value to appear at the original frequency point of the resonant cell, the selected cell can be regarded as the "on state" of the corresponding pixel, and is represented by the number "1". In particular, in the process of controlling the MOS tube, the MOS tube can be controlledThe modulation is performed in a row-by-row (i.e., M × M per row) manner.

Fig. 2 is a schematic diagram of a super-surface unit according to an embodiment of the present invention, in which an orthogonal projection of the super-surface unit is a square, a side length of the square is a × N μm, and each super-surface unit is composed of N × N resonant super-structure units. Wherein a is the side length of the orthographic projection of the resonant superstructure unit.

In the embodiment of the present invention, the height refers to a dimension in the Z direction in fig. 3. Fig. 3 is a schematic structural diagram of a single resonant superstructure unit in fig. 2, and as shown in fig. 3, the resonant superstructure unit includes a metal substrate layer 1, a phase change material layer 2, a dielectric layer 3, and a resonant module 4, which are sequentially stacked, where the metal substrate layer 1, the phase change material layer 2, and the dielectric layer 3 in the resonant superstructure unit are squares with equal side lengths, and the side length of the square is 49-51 μm, and in this embodiment, the side length of the square is preferably 50 μm. The thickness of the metal substrate layer 1 is 0.9-1.1 μm, 1 μm being chosen for this example. The thickness of the phase change material layer 2 is 1.95-2.05 μm, preferably 2.00 μm in this embodiment. The thickness of the dielectric layer 3 is 0.95-1.05 μm, preferably 1.00 μm in this embodiment. The resonance module 4 is placed in the very center of the dielectric layer 3.

The resonance module 4 includes a large circular cylinder (i.e., a first circular cylinder) and a small circular cylinder (i.e., a second circular cylinder), which are concentrically disposed. The height of the large circular cylinder is the same as that of the small circular cylinder, and the height is in the range of 0.15-0.25 μm, and preferably, the height is 0.2 μm. The difference in height affects the resonance frequency, resulting in a deterioration of the wave-absorbing effect. The resonance module is made of metal material copper.

In this embodiment, the dielectric layer 3 is made of SiO₂The phase change material layer 2 is Ge with a relative dielectric constant of 3.9₂Sb₂Te₅. The phase change material has a dielectric constant of epsilon when the phase change material layer is in an amorphous state_a18.0+0.01i, and a dielectric constant in the crystalline state of ε_c＝33.0+6.00i。

In this embodiment, when an incident electromagnetic field perpendicularly enters the super-surface structure unit along the z-direction (as shown in fig. 3), the metal ring generates an induced current, the current flows through the two arms of the ring in opposite directions, the metal ring generates electric dipole oscillation, the bottom metal layer current is mainly concentrated right below the ring, the current direction is opposite to the ring current direction, a loop is formed, magnetic dipole resonance is further excited, and the reflectivity reaches a minimum value at the resonance frequency. Fig. 4 and 5 are a circular ring surface current vector diagram and a metal layer surface current vector diagram of the super-surface at 1.133 THz. Fig. 6 and 7 are a circular ring surface current vector diagram and a metal layer surface current vector diagram of the super-surface at 2.840 THz. Wherein, referring to fig. 4, the two arms of the ring refer to the left and right metal parts of the metal ring which are bisected from the middle symmetry axis in the embodiment.

FIG. 8 is a graph of the reflection curves of an example of the super-surface phase change material in the amorphous and crystalline states, where the amorphous state has two reflection minima, 1.133THz reflectivity of 0.009 and 2.840THz reflectivity of 0.020; in a crystalline mode, the reflectivity of an original resonant frequency point 1.133THz is 0.985, the reflectivity of 2.840THz is 0.932, the reflectivity has great contrast, a unit with a resonant reflection minimum value at each pixel point can be regarded as a dark place and represented by a number '0', a unit with a resonant reflection maximum value at the original frequency point after phase change can be regarded as a bright place and represented by a number '1', and at the moment, a pattern with inconsistent amplitude spatial distribution can be generated on the surface of the device, so that amplitude modulation of terahertz wave front is realized.

Fig. 9 is a simulation diagram of the super-surface unit heating according to the embodiment of the present invention, in which the drain of the MOS transistor is connected to the side of the metal layer, the other side of the metal layer is grounded, and after the MOS transistor is turned on, a voltage of 0.1V is applied, and the metal layer serves as a heater, so that the entire phase change layer reaches the melting temperature of 610 ℃ at 25 μ s, and the off-state voltage is cooled to room temperature GST and the GST changes from the amorphous state to the crystalline state. At this time, the reflectivity of the original resonant frequency point is greatly different. Meanwhile, the dielectric layer 3 is SiO₂The layer is resistant to high temperatures and still maintains its stability during heating.

FIG. 10 is a schematic diagram of ideal imaging or spatial modulation of a cross binary image according to an embodiment of the present invention, wherein when an incident terahertz wave is 1.334THz, the MOS transistor is controlled to be turned on and the Ge is heated₂Sb₂Te₅(GST) in the absence ofThe crystalline state and the crystalline state are switched, the reflectivity of the original resonant frequency point is changed between a larger normal value and a minimum value, when the reflectivity is at the minimum value, the corresponding selected unit can be regarded as a dark place, namely the off state of the corresponding pixel, the intensity of reflected light is extremely small and is represented by a number 0, and the schematic diagram is white; on the contrary, when the phase change causes the resonance module to have a reflection maximum at the original frequency point, the corresponding selected cell can be regarded as being lighted, i.e. the corresponding pixel is in an "on state", which is represented by the number "1", and the schematic diagram is black.

Compared with the prior art, the embodiment of the invention at least has the following beneficial effects:

the super-surface of the invention can control the on-off of the MOS tube through the transverse electrode and the longitudinal electrode, and further applies voltage to heat the phase change material layer to change the amorphous GST into the crystalline GST, the dielectric constant is obviously changed, and the reflectivity of the original resonance point has larger contrast. The principle of the resonance between the super-surface and the terahertz waves is that when electromagnetic waves are incident along the Z axis, the metal ring generates induced currents, currents flow through two arms of the ring, the directions of the induced currents of the two arms are opposite, the metal ring generates electric dipole oscillation, the bottom metal layer currents are mainly concentrated under the resonance ring, the current direction of the bottom metal layer currents is opposite to the current direction of the ring, a loop is formed, magnetic dipole resonance is further excited, and the reflectivity reaches a minimum value at the resonance frequency. At each pixel point, the reflectivity of the original resonant frequency point changes between a larger normal value and a minimum value, when the reflectivity is at the minimum value, the corresponding selected unit can be regarded as a dark place, namely the 'off state' of the corresponding pixel, the intensity of reflected light is extremely small, and the reflected light is represented by a number '0'; on the contrary, when the phase change causes the resonance module to have a reflection maximum at the original frequency point, the corresponding selected cell can be regarded as being lighted, i.e. the corresponding pixel is in an "on state" and is represented by the number "1". During the period, the surface can generate spatial amplitude distribution through reflection, so that the surface can be conveniently applied to terahertz image generation through a subsequent modulation means, reflected electromagnetic intensity or energy spatial distribution is generated, a pattern with inconsistent light and shade distribution of pixel points is obtained through receiving of a detector, and spatial amplitude modulation of terahertz wave front is realized.

In the foregoing description of the specification, reference to the description of "one embodiment/example," "another embodiment/example," or "certain embodiments/examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.