CN115390176A - Terahertz polarization conversion unit and terahertz polarization converter - Google Patents
Terahertz polarization conversion unit and terahertz polarization converter Download PDFInfo
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- G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
- G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
- G02B5/3041—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
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- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
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- H01P7/08—Strip line resonators
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Abstract
The invention provides a terahertz polarization conversion unit and a terahertz polarization converter, wherein the terahertz polarization conversion unit comprises: the phase change material comprises a metal film bottom layer, a first dielectric layer, a phase change material layer, a second dielectric layer and a resonance strip layer; the resonance strip layer comprises parallel or vertical phase change material strips and combined material strips; the composite strip of material comprises: metal strips and phase change material terminations; the length of the metal strip is larger than that of the phase change material strip, and the orthographic projection of the combined material strip on the second medium layer penetrates through the second medium layer. According to the terahertz polarization conversion unit and the terahertz polarization converter provided by the embodiment of the invention, the phase change material layer, the phase change material strip and the phase change material end point are caused to generate the phase change, the thickness of the resonant cavity and the length of the strip generating the resonance are changed, and the incident light is modulated in a high frequency band or a low frequency band by utilizing different resonant cavities in different states, so that the modulation effect of converting broadband terahertz linear polarization into circular polarization is realized.
Description
Technical Field
The invention relates to the technical field of terahertz, in particular to a terahertz polarization conversion unit and a terahertz polarization converter.
Background
Terahertz waves are a new frequency band with great research and development values. Terahertz waves refer to electromagnetic radiation with a frequency of 100GHz-10THz in a broad sense, and the frequency band of the terahertz waves is very wide; therefore, how to perform better modulation processing on the ultra-wideband terahertz waves (for example, how to cover and process the wider-band terahertz waves to a great extent) is an important research direction at present.
The existing terahertz polarization converter can utilize a metal strip structure and a metal film to form a resonant cavity so as to realize the function of converting linearly polarized light into circularly polarized light. When terahertz waves are normally incident, compared with the bandwidth of 0.2THz-2THz commonly used in terahertz spectrum testing, the bandwidth capable of being modulated by the terahertz polarization converter is 0.73THz-1.39THz, and the bandwidth coverage range of the terahertz polarization converter for the terahertz waves is small.
Disclosure of Invention
In order to solve the above problems, embodiments of the present invention provide a terahertz polarization conversion unit and a terahertz polarization converter.
In a first aspect, an embodiment of the present invention provides a terahertz polarization conversion unit, including: the resonance strip layer comprises a metal film bottom layer, a first dielectric layer, a phase change material layer, a second dielectric layer and a resonance strip layer which are sequentially arranged in a laminated manner; the first dielectric layer and the second dielectric layer are transparent in a working waveband; the resonance strip layer comprises a phase change material strip and a combined material strip which are positioned on the same plane and are arranged in parallel or perpendicular to each other; the composite strip of material comprises: a metal strip and a phase change material end point connected to an end of the metal strip; the length of the metal strip is greater than that of the phase change material strip, and the orthographic projection of the combined material strip on the second dielectric layer penetrates through the second dielectric layer; the phase change material layer, the phase change material strip and the phase change material end point are in a conductive state or a semiconductor state at different temperatures.
Optionally, the number of the phase change material strips is multiple.
Optionally, the composite material strip is arranged coincident with a diagonal of the second dielectric layer.
Optionally, the number of the phase change material strips is a nonzero even number, and the phase change material strips are symmetrically arranged on two sides of the combined material strip.
Optionally, the material of the phase change material layer comprises: vanadium dioxide or germanium antimony tellurium; the material of the phase change material strip comprises: vanadium dioxide or germanium antimony tellurium; the phase change material end point material comprises: vanadium dioxide or germanium antimony tellurium.
Optionally, the material of the metal film base layer comprises: gold, silver, copper, aluminum, platinum, or chromium; the material of the metal strip comprises: gold, silver, copper, aluminum, platinum or chromium.
Optionally, the thickness of the metal film underlayer is greater than or equal to 0.1 μm.
Optionally, the thickness of the phase change material layer is 0.1 μm to 5 μm; the thickness of the resonance strip layer is 0.1-5 μm.
Optionally, the thickness of the first dielectric layer is 25 μm to 45 μm; the thickness of the second dielectric layer is 20-30 μm.
Optionally, the length of the metal strip is 230 μm to 270 μm; the width of the metal strip is 2-30 μm.
Optionally, the length of the phase change material strip is 100 μm to 140 μm; the width of the phase change material strip is 5-35 mu m.
Optionally, the distance between the phase change material strip and the combined material strip is 50 μm to 90 μm.
Optionally, the period of the terahertz polarization conversion unit along the x direction is 180 μm to 220 μm; the period of the terahertz polarization conversion unit along the y direction is 180-220 microns; and the x direction and the y direction are two directions which are mutually vertical.
In a second aspect, an embodiment of the present invention provides a terahertz polarization converter, including: the terahertz polarization conversion device comprises a plurality of terahertz polarization conversion units, wherein the plurality of terahertz polarization conversion units are arranged in an array manner.
In the solution provided by the foregoing first aspect of the embodiment of the present invention, in the terahertz polarization conversion unit provided in the embodiment of the present invention, the phase change material layer, the phase change material strip, and the phase change material end point are caused to generate a phase change, so that the phase change material layer, the phase change material strip, and the phase change material end point are converted between the conductor state and the non-conductor state, the structure of the resonance unit (unit that resonates with incident light in the terahertz waveband) can be changed, the thickness of the resonant cavity in the terahertz polarization conversion unit and the length of the strip that resonates in the resonance strip layer are changed (for example, the length of the strip that resonates changes when the strip that resonates changes), and thus, the incident light is modulated in the high frequency band or the low frequency band by using different resonant cavities in different states, so that a modulation effect of converting terahertz polarization light in a wider waveband into circular polarization is achieved. The terahertz polarization conversion unit has a large bandwidth coverage range for terahertz waves, and can cover a high frequency band and a low frequency band of a terahertz wave band.
In the solution provided by the second aspect of the embodiments of the present invention, the terahertz polarization converter can enlarge the receiving area of the terahertz polarization conversion unit for the incident light of the terahertz waveband, improve the modulation efficiency of the terahertz polarization converter, and the terahertz polarization converter has a large bandwidth coverage for the terahertz waveband.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a perspective view illustrating a terahertz polarization conversion unit provided by an embodiment of the present invention;
fig. 2 is a perspective view illustrating that a phase change material strip and a combined material strip are arranged perpendicular to each other in a terahertz polarization conversion unit provided by an embodiment of the present invention;
fig. 3 shows a top view of a first terahertz polarization conversion unit provided by an embodiment of the invention;
fig. 4 shows a top view of a second terahertz polarization conversion unit provided by an embodiment of the present invention;
fig. 5 shows a top view of a third terahertz polarization conversion unit provided by the embodiment of the invention;
fig. 6 shows a schematic structural diagram of a terahertz polarization converter provided by an embodiment of the present invention;
FIG. 7 shows a top view of embodiment 1;
FIG. 8 shows a side view of embodiment 1;
FIG. 9 is a diagram showing a simulation result of example 1;
FIG. 10 is a diagram showing another simulation result of example 1;
fig. 11 shows an elliptical polarizability diagram corresponding to incident light of a terahertz wave band reflected in example 1.
Icon:
the terahertz polarization conversion device comprises a 1-metal film bottom layer, a 2-first medium layer, a 3-phase change material layer, a 4-second medium layer, a 5-resonance strip layer, a 51-phase change material strip, a 52-combined material strip, a 521-metal strip, a 522-phase change material end point and a 100-terahertz polarization conversion unit.
Detailed Description
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are used merely for convenience of description and simplification of the description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise explicitly stated or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
An embodiment of the present invention provides a terahertz polarization conversion unit, and as shown in fig. 1, the terahertz polarization conversion unit includes: the phase change material comprises a metal film bottom layer 1, a first dielectric layer 2, a phase change material layer 3, a second dielectric layer 4 and a resonance strip layer 5 which are sequentially arranged in a laminated manner; the first medium layer 2 and the second medium layer 4 are transparent in the working wave band; fig. 1 shows a perspective view of the terahertz polarization conversion unit.
As shown in fig. 1, the resonance strip layer 5 includes a phase change material strip 51 and a combined material strip 52 which are located on the same plane and are arranged parallel to each other or perpendicular to each other; the combined material strip 52 comprises: a metal strip 521 and a phase change material end point 522 attached to an end of the metal strip 521; the length of the metal strip 521 is greater than that of the phase change material strip 51, and the orthographic projection of the combined material strip 52 on the second medium layer 4 penetrates through the second medium layer 4; the phase change material layer 3, the phase change material strips 51 and the phase change material terminals 522 exhibit a conductive state or a semiconductor state at different temperatures.
In the terahertz polarization conversion unit provided by the embodiment of the invention, the five structural layers (for example, a metal film bottom layer 1, a first dielectric layer 2, a phase change material layer 3, a second dielectric layer 4 and a resonance strip layer 5 which are sequentially stacked from bottom to top in fig. 1) form an integrated structure; wherein, the resonance strip layer 5 at the uppermost layer in fig. 1 includes phase change material strips 51 and combined material strips 52, wherein the number of the phase change material strips 51 can be 1, and for convenience of subsequent description, a schematic diagram of this case is not shown in the embodiment of the present invention, and fig. 1 illustrates that two phase change material strips 51 are included; optionally, the number of the phase change material strips 51 is multiple; when the number of the phase change material strips 51 is greater than 1, the transmittance of the terahertz polarization conversion unit with the structure for incident light is higher.
In the embodiment of the present invention, the phase change material strips 51 and the combined material strips 52 may be arranged in parallel, or may also be arranged in perpendicular; fig. 1 is a schematic view of a phase change material strip 51 and a combined material strip 52 arranged parallel to each other; alternatively, referring to fig. 2, fig. 2 is a schematic diagram illustrating that the phase change material strip 51 and the combined material strip 52 are arranged perpendicular to each other, and the arrangement manner of the phase change material strip 51 and the combined material strip 52 is not limited by the embodiment of the present invention.
The terahertz polarization conversion unit provided by the embodiment of the invention is used for receiving incident light emitted to the surface (such as vertical irradiation) from the outside, generating resonance on the incident light, and realizing high reflection and phase modulation on the incident light through multiple interference effects. Wherein the incident light is linearly polarized light, and the incident light can enter the resonance strip layer 5 in a polarization direction with an angle of 45 degrees with the combined material strip 52 (or the phase change material strip 51); the incident light is generally light in a terahertz waveband, that is, the working waveband of the terahertz polarization conversion unit under a normal condition is the terahertz waveband; the first dielectric layer 2 and the second dielectric layer 4 are transparent in the terahertz waveband, that is, the first dielectric layer 2 and the second dielectric layer 4 both have high transmittance to light in the terahertz waveband, and generally, the first dielectric layer 2 and the second dielectric layer 4 have high transmittance to light in the terahertz wavebandThe first dielectric layer 2 and the second dielectric layer 4 may be made of the same or different thz low-loss materials, including quartz, high-resistance silicon, polyimide, PDMS (poly N, N-dimethylacrylamide), SU8 (an epoxy-based photoresist material), PMMA (Polymethyl methacrylate, organic glass), PET (Polyethylene terephthalate, poly terephthalic plastic), BCB (benzocyclobutene), al 2 O 3 (alumina), mgO (magnesia), and the like. Further, the surface of the terahertz polarization conversion unit receiving incident light is the surface of the terahertz polarization conversion unit on the side away from the metal film underlayer 1, such as the surface on the side having the resonance strip layer 5 in fig. 1. It should be noted that: since the actual area of the resonance band layer 5 only corresponds to the area of the phase change material strips 51 and the combined material strips 52 contained therein, when incident light is incident on the side surface, a part of the light is irradiated onto the part of the second medium layer 4 which cannot be covered by the resonance band layer 5.
As shown in fig. 1, the composite material strip 52 comprises two different materials, one being a metallic material from which the metallic strip 521 of the composite material strip 52 is constructed; the other is phase change material from which the phase change material terminals 522 in the combined material strip 52 are formed; the number of the phase change material terminals 522 may be two, the two terminals are respectively located at two ends of the metal strip 521, and are connected with the metal strip 521 to form an integral structure (the composite material strip 52), and the two phase change material terminals 522 can be used as two terminals of the composite material strip 52. In the embodiment of the present invention, the length of the metal strip 521 is greater than that of the phase change material strip 51, and correspondingly, the length of the combined material strip 52 is also greater than that of the phase change material strip 51; furthermore, both ends of the combined material strip 52 (e.g. the two phase change material end points 522) are respectively in contact with the edge or the top corner of the second medium layer 4, i.e. the orthographic projection of the combined material strip 52 on the second medium layer 4 can penetrate through the second medium layer 4.
For example, referring to fig. 3 (fig. 3 is a top view of a first terahertz polarization conversion unit), a plane coordinate system is constructed on a side surface of the second medium layer 4 away from the metal film substrate 1 (not shown in fig. 3), a horizontal direction in fig. 3 is an x direction, a vertical direction perpendicular to the x direction is a y direction, the combined material strip 52 is vertically disposed on a side surface of the second medium layer 4 away from the metal film substrate 1, and the length of the combined material strip 52 is identical to the length of the second medium layer 4 in the y direction, if the phase change material end points 522 at two ends of the combined material strip 52 are respectively in contact with (or flush with) the upper edge and the lower edge of the second medium layer 4, an orthographic projection of the combined material strip 52 on the second medium layer 4 can penetrate through the second medium layer 4; alternatively, as shown in fig. 4 (fig. 4 is a top view of the second terahertz polarization conversion unit), the combined material strip 52 is horizontally disposed on a side surface of the second dielectric layer 4 away from the metal film underlayer 1 (not shown in fig. 4), the length of the combined material strip 52 is the same as the length of the second dielectric layer 4 in the x direction, for example, the phase change material end points 522 at two ends of the combined material strip 52 are respectively in contact with (or flush with) the left edge and the right edge of the second dielectric layer 4; still alternatively, as shown in fig. 5 (fig. 5 is a top view of the third terahertz polarization conversion unit, and is consistent with the structure shown in fig. 1), the combined material strip 52 is disposed along a diagonal on a side surface of the second dielectric layer 4 away from the metal film underlayer 1 (not shown in fig. 5), a length of the combined material strip 52 is consistent with a length of the diagonal of the second dielectric layer 4, for example, end points 522 of the phase change material at two ends of the combined material strip 52 are respectively in contact with (or flush with) two pairs of corners of the second dielectric layer 4.
In the embodiment of the present invention, the phase change material layer 3, the phase change material strip 51, and the phase change material end point 522 included in the terahertz polarization conversion unit are all structural layers capable of changing their states according to applied excitation (such as photo-thermal excitation or electro-thermal excitation), so as to change their functions, for example, under the action of some external excitation, the phase change material layer 3, the phase change material strip 51, and the phase change material end point 522 may be converted from a semiconductor state to a conductor state, so that their functions may be converted from originally transmitted incident light to reflected incident light; alternatively, under the action of another external excitation, the phase change material layer 3, the phase change material strips 51 and the phase change material terminals 522 can also be changed from a conductor state to a semiconductor state, so that the function thereof can be changed from originally reflecting incident light to transmitting incident light.
Specifically, in the terahertz polarization conversion unit provided by the embodiment of the present invention, under the condition that the phase change material layer 3, the phase change material strip 51 and the phase change material endpoint 522 maintain the semiconductor state, the phase change material layer 3, the phase change material strip 51 and the phase change material endpoint 522 are transparent to incident light, for example, the phase change material layer 3, the phase change material strip 51 and the phase change material endpoint 522 all have no resonance response to the incident light; as shown in fig. 5, the incident light (denoted by c) is linearly polarized light, the polarization direction of the incident light is indicated by a dashed double-arrow line, the incident light enters perpendicularly to the second medium layer 4, and the polarization direction of the incident light forms an included angle θ of 45 degrees with the combined material strip 52; in this state, the metal strip 521 and the metal film bottom layer 1 form a resonant cavity, and the thickness of the cavity is the total thickness of the first dielectric layer 2, the phase change material layer 3 and the second dielectric layer 4 (as shown in fig. 1); incident light resonates in the resonant cavity (the cavity between the metal strip 521 and the metal film base layer 1).
As shown in fig. 5, the electric field of the incident light
Can be decomposed into orthogonal components parallel to metal strip 521 and perpendicular to metal strip 521
And
the incident electric field of the incident light
Can be expressed as:
wherein r is 1 And r 2 The reflectivity of the incident light of the terahertz waveband in the direction parallel to the metal strip 521 and the reflectivity in the direction perpendicular to the metal strip 521 are respectively; θ =45 °; in the embodiment of the invention, when incident light in a terahertz waveband is modulated by the terahertz polarization conversion unit, terahertz waves can be obtained by reflection,the polarization conversion performance of the terahertz waves can be effectively represented by calculating the Stokes parameters of the reflected terahertz waves. Further, the calculation formula of the stokes parameter can be expressed as:
wherein S is 0 、S 1 、S 2 And S 3 And represents the parameters of the stokes number,
representing a phase difference between the vertical direction and the parallel direction of the reflected terahertz wave; based on the stokes parameters, an elliptical polarization rate χ (a standard parameter for determining a polarization state) corresponding to the reflected terahertz waves can be calculated, wherein χ = S 3 /S 0 (ii) a If the elliptic polarizability x is close to 1, determining the polarization state of the terahertz waves reflected by the terahertz polarization conversion unit to be left-handed circularly polarized light; if the elliptic polarizability chi is close to-1, the polarization state of the terahertz wave reflected by the terahertz polarization conversion unit is determined to be right-handed circularly polarized light.
In the embodiment of the present invention, because the length of the metal strip 521 is long, the wavelength of the incident light of the metal strip 521 corresponding to resonance is also long, and because the wavelength of the incident light is in a reciprocal relationship with the frequency, in this state (the phase change material layer 3, the phase change material strip 51, and the phase change material end point 522 maintain a semiconductor state), the resonant cavity formed by the metal strip 521 and the metal film bottom layer 1 can process the incident light of a low frequency band, when the incident light (light of a broadband terahertz wave band) passes through the terahertz polarization conversion unit, the incident light can be resonated and modulated in a lower frequency band, and in this state, the elliptical polarization rate χ can be calculated according to the above formula to be close to-1, which proves that the terahertz polarization conversion unit in this state can convert the incident light of the terahertz wave band from linearly polarized light to right circularly polarized light, and the terahertz polarization conversion unit exhibits the same modulation effect as the quarter wave plate.
In addition, in the terahertz polarization conversion unit provided by the embodiment of the present invention, under the condition that the phase change material layer 3, the phase change material strips 51 and the phase change material end points 522 maintain the conductor state, the phase change material layer 3, the phase change material strips 51 and the phase change material end points 522 reflect (e.g., totally reflect) incident light; the phase change material end point 522 and the metal strip 521 (the combined material strip 52) form a grating structure, the grating structure (the combined material strip 52) has a large period and a small structure broadband, and has a small modulation effect on incident light in a terahertz waveband, so that the modulation effect on the incident light in the terahertz waveband can be ignored, that is, the combined material strip 52 has no resonance response to the incident light in a state that the phase change material end point 522 maintains a conductor state. Moreover, since the phase change material strips 51 and the phase change material layer 3 are both in a conductive state, in this state, the phase change material strips 51 and the phase change material layer 3 form a resonant cavity, and the thickness of the cavity is reduced, for example, the thickness of the cavity is changed to the thickness of the second dielectric layer 4; incident light resonates in the resonant cavity (the cavity between the phase change material strip 51 and the phase change material layer 3). Because the length of the phase change material strip 51 is short, the wavelength of the incident light corresponding to resonance of the phase change material strip 51 is also short, and the wavelength of the incident light is in a reciprocal relationship with the frequency, in this state (the phase change material layer 3, the phase change material strip 51 and the phase change material endpoint 522 maintain a conductive state), the phase change material strip 51 and the phase change material layer 3 form a resonant cavity to process the incident light of a high frequency band, the incident light (light of a broadband terahertz wave band) can be resonated and modulated in the high frequency band when passing through the terahertz polarization conversion unit, and in this state, the elliptical polarization rate χ can be calculated according to the above equation to be close to-1, which proves that the terahertz polarization conversion unit in this state can convert the incident light of the terahertz wave band from linearly polarized light to right-handed circularly polarized light.
The terahertz polarization conversion unit provided by the embodiment of the invention can change the structure of a resonance unit (a unit which generates resonance with incident light of an incident terahertz waveband) by causing the phase change material layer 3, the phase change material strip 51 and the phase change material endpoint 522 to generate phase change between a conductor state and a non-conductor state, change the thickness of a resonant cavity in the terahertz polarization conversion unit and the length of a strip which generates resonance in the resonance strip layer 5 (for example, the length of the strip which generates resonance is changed when the strip which generates resonance is changed), and thus, the terahertz polarization conversion unit can modulate the incident light in a high frequency band or a low frequency band by using different resonant cavities in different states, thereby realizing the modulation effect of converting terahertz polarization of a wider waveband into circular polarization. The terahertz polarization conversion unit has a large bandwidth coverage range for terahertz waves, and can cover a high frequency band and a low frequency band of a terahertz wave band.
Alternatively, referring to fig. 1 and 5, the combined material strip 52 is arranged to coincide with a diagonal of the second dielectric layer 4.
In the embodiment of the present invention, since the combined material strip 52 is overlapped and disposed on the diagonal line of the second medium layer 4, the length of the combined material strip 52 is longer than that when disposed at other positions, so that the length of the metal strip 521 is longer, the frequency band of the incident light (light of the broadband terahertz wave band) that can be modulated is lower, and the low frequency band that cannot be modulated by the conventional terahertz polarization converter can be covered.
Alternatively, as shown in fig. 1 to 5, the number of the phase change material strips 51 is a non-zero even number, and the phase change material strips 51 are symmetrically arranged on both sides of the combined material strip 52.
In this case, the same number of phase change material strips 51 may be symmetrically disposed on both sides of the combined material strip 52, for example, as shown in fig. 1 to 5, the number of the phase change material strips 51 is 2, and 1 phase change material strip 51 may be disposed on each of both sides of the combined material strip 52 (as shown in fig. 1, 2, or 5, the upper left and lower right of the combined material strip 52, or as shown in fig. 3, the left and right of the combined material strip 52, or as shown in fig. 4, the upper and lower sides of the combined material strip 52) so that both sides of the combined material strip 52 form a symmetrical structure. The space utilization rate of the terahertz polarization conversion unit can be improved through the arrangement mode, so that the bandwidth and the modulation effect of incident light which can be modulated by the terahertz polarization conversion unit are improved.
Alternatively, the material of the phase change material layer 3 includes: vanadium dioxide or germanium antimony tellurium; the material of the phase change material strip 51 comprises: vanadium dioxide or germanium antimony tellurium; the materials of the phase change material end point 522 include: vanadium dioxide or germanium antimony tellurium.
In the embodiment of the present invention, vanadium dioxide is a metal oxide having a phase transition property, and the phase transition temperature of vanadium dioxide is 68 ℃, and vanadium dioxide can be specifically converted between a metal state (a conductor state) and an insulation state (a non-conductor state), so that the phase change material layer 3, the phase change material strip 51, and the phase change material end point 522 in the embodiment of the present invention are required to function; or, in the embodiment of the present invention, a germanium antimony tellurium (GST) material may also be selected as the material of the phase change material layer 3, the phase change material strip 51, or the phase change material endpoint 522, and under irradiation of incident light in the terahertz band, the germanium antimony tellurium material changes between a crystalline state and an amorphous state, and may also reflect the incident light. In the embodiment of the present invention, other materials (such as a doping material of the same system) having the above-mentioned functions may also be selected as the materials of the phase change material layer 3, the phase change material strip 51 and the phase change material end 522, and the phase change material layer 3, the phase change material strip 51 and the phase change material end 522 may be made of the same material at the same time, for example, a vanadium dioxide material may be selected at the same time, which is not specifically limited in the embodiment of the present invention.
Alternatively, the material of the metal film base layer 1 includes: gold, silver, copper, aluminum, platinum, or chromium; the material of the metal strip 521 includes: gold, silver, copper, aluminum, platinum or chromium.
In the embodiment of the present invention, a metal material with high conductivity may be used as the material of the metal film underlayer 1 or the metal strip 521, for example, among the above-mentioned metal materials, gold is more effective, and gold may be used as the material of both the metal film underlayer 1 and the metal strip 521.
Alternatively, the metal film base layer 1 may have a thickness of 0.1 μm or more, for example, a thickness of 0.2 μm. It should be noted that, the specific thickness of the metal film underlayer 1 may be determined according to specific situations, and this is not limited by the embodiment of the present invention.
Optionally, the thickness of the phase change material layer 3 is 0.1 μm to 5 μm; the thickness of the resonance strip layer 5 is 0.1 μm to 5 μm. For example, the thickness of the phase change material layer 3 may be 1 μm; the thickness of the resonance strip layer 5 may also be 1 μm.
Optionally, the thickness of the first dielectric layer 2 is 25 μm to 45 μm; the thickness of the second dielectric layer 4 is 20 μm to 30 μm. For example, the thickness of the first dielectric layer 2 may be 35 μm and the thickness of the second dielectric layer 4 may be 25 μm.
Optionally, the length of the metal strip 521 is 230 μm to 270 μm; the width of the metal strip 521 is 2 μm to 30 μm. For example, the length of the metal strip 521 may be 250 μm and the width of the metal strip 521 may be 5 μm.
Optionally, the length of the phase change material strip 51 is 100 μm to 140 μm; the width of the strips 51 of phase change material is between 5 and 35 μm. For example, the length of the phase change material strip 51 may be 120 μm; the width of the strips 51 of phase change material may be 20 μm.
Optionally, the spacing between the strips 51 of phase change material and the strips 52 of composite material is between 50 μm and 90 μm. For example, the spacing between the strips of phase change material 51 and the strips of composite material 52 may be 70 μm.
Optionally, the period of the terahertz polarization conversion unit along the x direction is 180 μm to 220 μm; the period of the terahertz polarization conversion unit along the y direction is 180-220 mu m.
As shown in fig. 5, the horizontal direction in fig. 5 is the x direction, the vertical direction perpendicular to the x direction is the y direction, and the period of the x direction or the period of the y direction corresponds to the length of the terahertz polarization conversion unit in the x direction or the length of the terahertz polarization conversion unit in the y direction. For example, the period of the terahertz polarization conversion unit in the x direction may be the same as the period thereof in the y direction, each being 200 μm.
An embodiment of the present invention further provides a terahertz polarization converter, as shown in fig. 6, including: a plurality of terahertz polarization conversion units 100 as described above, and the plurality of terahertz polarization conversion units 100 are arranged in an array. The plurality of terahertz polarization conversion units 100 may be arranged in an array form (fig. 6 is a schematic diagram of the arrangement of the 6 terahertz polarization conversion units 100 in the array form), and the combined material strips 52 in the plurality of terahertz polarization conversion units 100 are connected to each other to form a grating when the phase change material end point 522 included in each of the plurality of terahertz polarization conversion units is in a conductor state, in which a resonance cannot be realized for incident light. The terahertz polarization converter formed by the embodiment of the invention can enlarge the receiving area of the terahertz polarization conversion unit 100 for incident light of a terahertz waveband, improve the modulation efficiency of the terahertz polarization converter, and has a large bandwidth coverage range for the terahertz waveband.
Example 1:
the specific structure of the terahertz polarization conversion unit is shown in fig. 1, and the specific structural parameters are as follows: px = Py =200 μm; l. the 1 ＝250μm；l 2 ＝120μm；w 1 ＝5μm；w 2 ＝20μm；g＝70μm；t 1 ＝1μm；t 2 ＝1μm；t 3 ＝0.2μm；d 1 ＝35μm；d 2 =25 μm; among them, px (period of the terahertz polarization conversion unit in the x direction), py (period of the terahertz polarization conversion unit in the y direction), l 1 (length of metal strip 521), l 2 (length of the phase change material strip 51), w 1 (width of metal strip 521), w 2 Both (width of the phase change material strip 51) and g (spacing between the phase change material strip 51 and the combined material strip 52) can be seen in fig. 7; t is t 1 (thickness of resonance strip layer 5), t 2 (thickness of phase change material layer 3), t 3 (thickness of Metal film substrate 1), d 1 (first Medium)Thickness of layer 2) and d 2 (thickness of the second dielectric layer 4) can be seen in fig. 8.
The specific structural parameters may be input into simulation software to perform numerical simulation calculation, so as to obtain two simulation result diagrams shown in fig. 9 and 10, and an elliptical polarization rate diagram shown in fig. 11 corresponding to the incident light of the terahertz waveband reflected in embodiment 1.
In the case that the phase change material layer 3, the phase change material strip 51 and the phase change material end point 522 are in the semiconductor state, when the incident light in the terahertz waveband is incident on the metal strip 521 in the 45-degree polarization direction, as shown in fig. 9, the reflectivity of the incident light in the terahertz waveband is close to 100% from 0.4THz to 0.85 THz; also, the phase retardation in the two directions (the curve corresponding to "phase difference" in fig. 9) of the component perpendicular to the metal strip 521, which is decomposed by the incident light in the polarization direction of 45 degrees, and the component horizontal to the metal strip 521 are close to 270 degrees (equivalent to minus 90-degree phase difference), indicating that the incident light in the linearly polarized terahertz band can be efficiently converted into light in the circularly polarized terahertz band in this band (e.g., 0.4THz to 0.85 THz).
In the case where the phase change material layer 3, the phase change material strip 51, and the phase change material end point 522 are in the conductive state, when the incident light of the terahertz wave band is incident on the metal strip 521 in the polarization direction of 45 degrees, as shown in fig. 10, the reflectance of the incident light of the terahertz wave band is close to 100% from 0.8THz to 1.5 THz; moreover, the phase retardation of the component perpendicular to the metal strip 521, which is decomposed by the incident light with the polarization direction of 45 degrees, and the component horizontal to the metal strip 521 in the two directions is close to 270 degrees (equivalent to a phase difference of minus 90 degrees), which indicates that the incident light in the linearly polarized terahertz band can be efficiently converted into the light in the circularly polarized terahertz band in this band (e.g., 0.8THz to 1.5 THz). Therefore, this embodiment 1 can convert light in the 0.4THz to 1.5THz band.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention, and the present invention shall be covered by the claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (14)
1. A terahertz polarization conversion unit is characterized by comprising: the phase change material comprises a metal film bottom layer (1), a first dielectric layer (2), a phase change material layer (3), a second dielectric layer (4) and a resonance strip layer (5) which are sequentially arranged in a laminated manner; the first medium layer (2) and the second medium layer (4) are transparent in a working waveband;
the resonance strip layer (5) comprises a phase change material strip (51) and a combined material strip (52) which are positioned on the same plane and are arranged in parallel or perpendicular to each other; the composite strip (52) comprises: a metal strip (521) and a phase change material end point (522) connected to the end of the metal strip (521);
the length of the metal strip (521) is greater than that of the phase change material strip (51), and the orthographic projection of the combined material strip (52) on the second medium layer (4) penetrates through the second medium layer (4); the phase change material layer (3), the phase change material strips (51) and the phase change material end points (522) are in a conductive state or a semi-conductive state at different temperatures.
2. The terahertz polarization conversion unit according to claim 1, wherein the phase change material strips (51) are plural in number.
3. The terahertz polarization conversion unit according to claim 1, wherein the combined material strip (52) is disposed to coincide with a diagonal of the second medium layer (4).
4. The terahertz polarization conversion unit according to claim 3, wherein the number of the phase change material strips (51) is a non-zero even number, and the phase change material strips (51) are symmetrically arranged on two sides of the combined material strip (52).
5. The terahertz polarization conversion unit according to any one of claims 1 to 4, wherein the material of the phase change material layer (3) comprises: vanadium dioxide or germanium antimony tellurium; the material of the phase change material strip (51) comprises: vanadium dioxide or germanium antimony tellurium; the phase change material termination (522) material includes: vanadium dioxide or germanium antimony tellurium.
6. The terahertz polarization conversion unit according to any one of claims 1 to 4, wherein the material of the metal film underlayer (1) includes: gold, silver, copper, aluminum, platinum, or chromium; the material of the metal strip (521) comprises: gold, silver, copper, aluminum, platinum or chromium.
7. The terahertz polarization conversion unit according to any one of claims 1 to 4, wherein the thickness of the metal film base layer (1) is greater than or equal to 0.1 μm.
8. The terahertz polarization conversion unit according to any one of claims 1 to 4, wherein the thickness of the phase change material layer (3) is 0.1 μm to 5 μm; the thickness of the resonance strip layer (5) is 0.1-5 μm.
9. The terahertz polarization conversion unit of any one of claims 1 to 4, wherein the thickness of the first dielectric layer (2) is 25 μm to 45 μm; the thickness of the second dielectric layer (4) is 20-30 μm.
10. The terahertz polarization conversion unit according to any one of claims 1 to 4, wherein the length of the metal strip (521) is 230 μm to 270 μm; the width of the metal strip (521) is 2-30 mu m.
11. The terahertz polarization conversion unit of any one of claims 1 to 4, wherein the length of the phase change material strip (51) is 100 μm to 140 μm; the width of the phase change material strip (51) is 5-35 mu m.
12. The terahertz polarization conversion unit of any one of claims 1 to 4, wherein a spacing between the phase change material strip (51) and the combination material strip (52) is 50 μm to 90 μm.
13. The terahertz polarization conversion unit according to any one of claims 1 to 4, wherein the period of the terahertz polarization conversion unit in the x direction is 180 μm to 220 μm; the period of the terahertz polarization conversion unit along the y direction is 180-220 microns; and the x direction and the y direction are two directions which are mutually vertical.
14. A terahertz polarization converter, comprising: a plurality of the terahertz polarization conversion units (100) as claimed in any one of claims 1 to 13, wherein the plurality of terahertz polarization conversion units (100) are arranged in an array.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11927769B2 (en) | 2022-03-31 | 2024-03-12 | Metalenz, Inc. | Polarization sorting metasurface microlens array device |
| US11978752B2 (en) | 2019-07-26 | 2024-05-07 | Metalenz, Inc. | Aperture-metasurface and hybrid refractive-metasurface imaging systems |
| US11988844B2 (en) | 2017-08-31 | 2024-05-21 | Metalenz, Inc. | Transmissive metasurface lens integration |
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2022
- 2022-09-05 CN CN202211078670.6A patent/CN115390176A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11988844B2 (en) | 2017-08-31 | 2024-05-21 | Metalenz, Inc. | Transmissive metasurface lens integration |
| US11978752B2 (en) | 2019-07-26 | 2024-05-07 | Metalenz, Inc. | Aperture-metasurface and hybrid refractive-metasurface imaging systems |
| US11927769B2 (en) | 2022-03-31 | 2024-03-12 | Metalenz, Inc. | Polarization sorting metasurface microlens array device |
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