Chiral metamaterial absorber for multifunctional sensing and preparation method thereof

Abstract

The invention provides a chiral metamaterial absorber for multifunctional sensing and a preparation method thereof, and relates to the technical field of optics, the absorber comprises three-dimensional double-layer unit structures arranged periodically, and each unit structure sequentially comprises a Z-like chiral metal layer and a temperature-sensitive semiconductor layer from top to bottom; the Z-like chiral metal layer is made of gold; the temperature-sensitive semiconductor layer is made of indium antimonide, the dielectric constant of the temperature-sensitive semiconductor layer dynamically changes along with the temperature, and active regulation and control of the terahertz wave band circular dichroism are achieved. Through a periodic three-dimensional structure of the Z-shaped chiral metal layer and the temperature-sensitive semiconductor layer, strong chiral selective absorption is realized in a terahertz wave band, and the terahertz temperature sensor has a 300-360K high-sensitivity temperature sensing function, a 1.0-2.0 wide-range refractive index and a high-quality factor guarantee efficient integration function.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a chiral metamaterial absorber for multifunctional sensing and a preparation method thereof. Background Art

[0002] Chirality is ubiquitous in nature, with molecules, proteins, and crystals all exhibiting chiral characteristics. Circular dichroism (CD), a core method for characterizing chirality, is defined as the difference in absorption of left-handed circularly polarized light (LCP) and right-handed circularly polarized light (RCP) by a chiral medium. It has important applications in biomonitoring, analytical chemistry, and biosensing. However, the CD effect of naturally occurring chiral media, such as DNA and proteins, is typically weak due to the poor compatibility between their nanoscale size and wavelength, limiting their practical applications.

[0003] To overcome these limitations, researchers have proposed chiral metamaterials, whose optical properties rely primarily on microstructural design rather than intrinsic material properties. By manipulating geometric structure and electromagnetic resonance, chiral responses can be significantly enhanced, playing a key role in fields such as chemical monitoring and biosensing. In recent years, chiral metamaterial sensing design has shown three major trends: Structural optimization: Evolution from two-dimensional to three-dimensional structures, and expansion of material systems from all-metal to metal-dielectric composites, all-dielectric, and ceramic hybrid materials to reduce losses and improve quality factors; Active control: Introducing external stimuli such as temperature, electric field, and magnetic field to achieve dynamic response, replacing passive parameter adjustment, enhancing environmental adaptability and reducing costs; Multifunctional integration: Combining wide-range sensing, high sensitivity, and high quality factor, such as simultaneous dual-parameter sensing of temperature and refractive index.

[0004] However, existing technologies still have significant drawbacks: Single function: Some terahertz chiral metamaterials are designed only as switches, lacking dynamic control capabilities and integrated sensing and absorption functions. Limited scope of application: Most structures have difficulty in achieving high-sensitivity sensing over a wide range of temperature or refractive index; Performance imbalance: It is difficult to achieve a high quality factor, high sensitivity and wide sensing range at the same time.

[0005] Therefore, there is an urgent need to develop a chiral metamaterial absorber that combines wide-range dynamic control, dual-function efficient sensing (temperature / refractive index) and high quality factor to meet the multifunctional sensing needs in complex environments. Summary of the Invention

[0006] To this end, the embodiments of the present invention provide a chiral metamaterial absorber for multifunctional sensing and a preparation method thereof, which are used to solve the problems in the prior art such as lack of dynamic regulation, single sensing function, and difficulty in balancing wide range and high sensitivity.

[0007] To solve the above problems, an embodiment of the present invention provides a chiral metamaterial absorber for multifunctional sensing, comprising: A periodically arranged three-dimensional double-layer unit structure, each unit structure consists of a Z-shaped chiral metal layer and a temperature-sensitive semiconductor layer from top to bottom; The material of the Z-shaped chiral metal layer is gold. In the xy plane, the plane profile of the Z-shaped chiral metal layer is a Z-shaped chiral structure. Its geometric structure is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows: Top horizontal rectangular edge: extends along the -x direction, with a length of , constituting the upper edge of the structure; Middle vertical rectangular segment: extends from the right end of the top horizontal rectangular segment in the -y direction with a length of , connecting the upper edge and the lower edge; Left protruding rectangular edge segment: extends from the left end of the top horizontal rectangular edge segment along the -y direction, with a length of , forming a downward bulge on the left side of the upper edge; Bottom horizontal rectangular segment: extends from the bottom end of the middle vertical rectangular segment in the +x direction, with a length of , forming the lower edge of the structure; The width of the top horizontal rectangular segment, the width of the left protruding rectangular segment, the width of the middle vertical rectangular segment and the width of the bottom horizontal rectangular segment are all ; The material of the temperature-sensitive semiconductor layer is indium antimonide, and its dielectric constant changes dynamically with temperature, thereby realizing active regulation of circular dichroism in the terahertz band.

[0008] Preferably, the period of the unit structure is 145 μm to 155 μm.

[0009] Preferably, the thickness of the Z-shaped chiral metal layer is 30μm~60μm.

[0010] Preferably, the structure of the temperature-sensitive semiconductor layer is a cube with a thickness of 30μm~60μm.

[0011] Preferably, the 15μm~25μm.

[0012] Preferably, the 50μm~80μm.

[0013] Preferably, the 60μm~90μm.

[0014] Preferably, the 20μm~35μm.

[0015] Preferably, the dielectric constant of the temperature-sensitive semiconductor layer satisfies the Drude model: ; in ; ; Where, is the dielectric constant at high frequency; =15.68; =0.1πTHz, indicating the damping constant; is the angular frequency in the terahertz band; is an imaginary unit; is the plasma frequency; represents the intrinsic carrier concentration; represents the charge of a free electron; represents the dielectric constant of vacuum; =0.015 , represents the effective mass of free carriers; , represents the mass of a free electron; represents the Boltzmann constant; Indicates absolute temperature, the unit is .

[0016] An embodiment of the present invention further provides a method for preparing a chiral metamaterial absorber for multifunctional sensing. The method is used to prepare the chiral metamaterial absorber for multifunctional sensing, comprising: Depositing a temperature-sensitive semiconductor layer of a set thickness on a substrate, wherein the material of the layer is indium antimonide; A Z-shaped chiral metal layer of a predetermined thickness is formed on the temperature-sensitive semiconductor layer. The material of the Z-shaped chiral metal layer is gold. In the xy plane, the Z-shaped chiral metal layer has a planar profile of a Z-shaped chiral structure. The geometric structure of the Z-shaped chiral metal layer is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows: Top horizontal rectangular edge: extends along the -x direction, with a length of , constituting the upper edge of the structure; Middle vertical rectangular segment: extends from the right end of the top horizontal rectangular segment in the -y direction with a length of , connecting the upper edge and the lower edge; Left protruding rectangular edge segment: extends from the left end of the top horizontal rectangular edge segment along the -y direction, with a length of , forming a downward bulge on the left side of the upper edge; Bottom horizontal rectangular segment: extends from the bottom end of the middle vertical rectangular segment in the +x direction, with a length of , forming the lower edge of the structure; The width of the top horizontal rectangular segment, the width of the left protruding rectangular segment, the width of the middle vertical rectangular segment and the width of the bottom horizontal rectangular segment are all .

[0017] It can be seen from the above technical solutions that the present invention has the following beneficial effects: (1) The present invention achieves dynamic control of chiral response in the terahertz band by utilizing the temperature-sensitive dielectric constant of the temperature-sensitive semiconductor layer. Within a wide temperature range of 300K~360K, the intrinsic carrier concentration of indium antimonide (InSb) changes exponentially with temperature, which in turn affects the dielectric constant through the plasma frequency, thereby causing a linear shift in the resonant frequency of the chiral metamaterial absorption spectrum. Data show that the temperature sensitivity of the low-frequency and high-frequency CD spectra reaches 1.46THz / K and 1.07THz / K, respectively, with corresponding quality factors of 103.51 and 82.8, respectively. In addition, the low-frequency CD peak increases steadily with increasing temperature, while the high-frequency CD peak remains near 0.8. This collaborative design of "active control + high-sensitivity sensing" breaks through the environmental adaptability limitations of traditional passive control structures and can meet the requirements of stable sensing in complex temperature environments.

[0018] (2) The Z-shaped chiral metal layer of the present invention enhances the coupling between light and structure through geometric asymmetry, achieving efficient refractive index sensing in a wide range of 1.0~2.0. When the ambient refractive index changes, the surface plasmon resonance conditions of the chiral structure change, resulting in a stable redshift trend in the CD spectrum: the low-frequency CD peak remains at 0.6~0.8, and the high-frequency CD peak is as low as 0.4, both maintaining a strong chiral effect. Linear fitting results show that the low-frequency refractive index sensitivity in the CD spectrum reaches 0.817THz / RIU and the high-frequency reaches 0.857THz / RIU, with quality factors of 56.41 and 43.3, respectively. This performance is better than most existing designs, and the dual-frequency response can achieve multi-parameter cross-validation, significantly improving sensing reliability.

[0019] (3) The left-right asymmetric design of the Z-shaped chiral metal layer of the present invention (the protrusion on the left side and the non-corresponding structure on the right side) significantly enhances the circular dichroism (CD) effect, forming a double-peak CD value at 1.696THz and 1.804THz in the terahertz band, which is as high as 80% and 70% respectively. It exhibits strong selective absorption of left-handed (LCP) and right-handed (RCP) circularly polarized light (strong RCP absorption and strong LCP reflection). At the same time, the high quality factor (Q factor) of the structure provides a guarantee for efficient sensing: low-frequency Q1 = 117.04, high-frequency Q2 = 91.4. In the presence of inherent dissipation in metal materials, the Q factor close to 100 effectively reduces signal interference and ensures high resolution of temperature and refractive index sensing. This "strong chirality + high Q factor" feature enables a single structure to simultaneously realize the three functions of chiral absorption, temperature sensing, and refractive index sensing, greatly improving the device's integration and adaptability to application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the implementation cases of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for use in the embodiments. By referring to the drawings, the features and advantages of the present invention will be more clearly understood. The drawings are for illustration only and should not be construed as limiting the present invention in any way. Those skilled in the art can derive other drawings based on these drawings without inventive effort. Among them: Figure 1 Schematic diagram of the structure of a chiral metamaterial absorber for multifunctional sensing provided by the present invention, wherein (a) is a three-dimensional stereogram of the absorber, and (b) is a two-dimensional plan view of the absorber; Figure 2 A flow chart of a method for preparing a chiral metamaterial absorber for multifunctional sensing provided by the present invention; Figure 3 Schematic diagram of the differential absorption of left-handed and right-handed circularly polarized light by a chiral metamaterial absorber according to an embodiment of the present invention, wherein (a) is the simulated optical absorption spectrum of the metamaterial under the incidence of LCP light and RCP light, and (b) is the simulated circular dichroism spectrum. Figure 4 Schematic diagram of the electric field distribution (xyz plane) in the unit structure proposed in the present invention at an external temperature of 300K in an embodiment of the present invention, wherein (a) is a schematic diagram when the incident LCP light has a frequency of 1.696 THz; (b) is a schematic diagram when the incident RCP light has a frequency of 1.696 THz; (c) is a schematic diagram when the incident LCP light has a frequency of 1.806 THz; and (d) is a schematic diagram when the incident RCP light has a frequency of 1.806 THz. Figure 5Schematic diagram of power flow distribution of the unit structure proposed in the present invention at z = 0 μm on the xy plane at an external temperature of 300K in an embodiment of the present invention, wherein (a) is a schematic diagram when the incident LCP light has a frequency of 1.696 THz; (b) is a schematic diagram when the incident RCP light has a frequency of 1.696 THz; (c) is a schematic diagram when the incident LCP light has a frequency of 1.806 THz; and (d) is a schematic diagram when the incident RCP light has a frequency of 1.806 THz. Figure 6 Schematic diagram of the refractive index sensing performance of the absorber of the present invention at different refractive indices in an embodiment of the present invention, wherein (a) is a CD spectrum diagram designed under different environmental refractive indices; (b) is the change of low frequency with refractive index and its corresponding linear fitting curve; (c) is the change of high frequency with refractive index and its corresponding linear fitting curve; Figure 7 Figure 1 is a graph showing the relationship between the resonant frequency of the absorber of the present invention and the change in ambient temperature, wherein (a) is a schematic diagram of the designed CD spectrum at different ambient temperatures, (b) is the change of low frequency with ambient temperature and its corresponding linear fitting curve; (c) is the change of high frequency with ambient temperature and its corresponding linear fitting curve Explanation of the accompanying drawings in the specification: 1. Z-shaped chiral metal layer; 2. Temperature-sensitive semiconductor layer. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] Example 1: To solve the problems of lack of dynamic control, single sensing function, and difficulty in balancing wide range and high sensitivity in the prior art. Figure 1 As shown, the present invention proposes a chiral metamaterial absorber for multifunctional sensing, comprising: A periodically arranged three-dimensional double-layer unit structure, each unit structure consists of a Z-shaped chiral metal layer 1 and a temperature-sensitive semiconductor layer 2 from top to bottom; The Z-shaped chiral metal layer 1 is made of gold. In the xy plane, the Z-shaped chiral metal layer 1 has a planar profile of a Z-shaped chiral structure. Its geometric structure is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows: Top horizontal rectangular edge: extends along the -x direction, with a length of , constituting the upper edge of the structure; Left protruding rectangular edge segment: extends from the left end of the top horizontal rectangular edge segment in the -y (downward) direction with a length of , forming a downward bulge on the left side of the upper edge; Middle vertical rectangular segment: extends from the right end of the top horizontal rectangular segment in the -y (downward) direction with a length of , connecting the upper edge and the lower edge; Bottom horizontal rectangular segment: extends from the bottom end of the middle vertical rectangular segment in the +x direction (to the right) with a length of , forming the lower edge of the structure; The width of the top horizontal rectangular segment, the width of the left protruding rectangular segment, the width of the middle vertical rectangular segment and the width of the bottom horizontal rectangular segment are all ; The material of the temperature-sensitive semiconductor layer 2 is indium antimonide, and its dielectric constant changes dynamically with temperature, thereby realizing active regulation of circular dichroism in the terahertz band.

[0023] As can be seen from the above technical solution, the present invention proposes a chiral metamaterial absorber for multifunctional sensing. It utilizes a periodically arranged three-dimensional bilayer structure consisting, from top to bottom, of a Z-shaped chiral metal layer 1 (gold) and a temperature-sensitive semiconductor layer 2 (indium antimonide). The Z-shaped chiral metal layer 1 enhances its chirality through an orthogonal asymmetric design consisting of a top horizontal rectangular segment, a left raised rectangular segment, a middle vertical rectangular segment, and a bottom horizontal rectangular segment. The temperature-sensitive semiconductor layer leverages the temperature sensitivity of the InSb dielectric constant to achieve dynamic control. This solution forms a dual-peak CD value (80% and 70%) in the terahertz band, achieving a wide range of temperature sensing from 300K to 360K (sensitivity 1.07 THz / K to 1.46THz / K) and a wide refractive index sensing range of 1.0 to 2.0 (sensitivity 0.817 THz / RIU to 0.857THz / RIU). The high Q factor (nearly 100) ensures high resolution, achieving chiral absorption, dual-parameter sensing integration and wide-range stable response.

[0024] like Figure 1 As shown in (a), the absorber is layered along the z-axis. The upper layer is a Z-shaped chiral metal layer 1, made of the precious metal gold (Au). Gold has a high resonance shift capability, effectively enhancing light-structure interactions in the terahertz band. Its excellent biocompatibility is well-suited for biosensing applications, while its chemical stability ensures structural reliability in sensing environments and is resistant to corrosion and oxidation. This Z-shaped chiral metal layer 1 resembles the letter Z, but differs from traditional simple Z-shaped chiral structures in that it enhances differential absorption by strengthening the left-right geometric asymmetry (e.g., a specific protrusion on one side and no corresponding structure on the other).

[0025] The lower layer is the temperature-sensitive semiconductor layer 2. The temperature-control material is indium antimonide (InSb), a narrow-bandgap semiconductor with a bandgap of approximately 0.17 eV at room temperature (300K). This property makes its intrinsic carrier concentration extremely sensitive to temperature. InSb also has the highest electron mobility of all common semiconductors, far exceeding that of materials like silicon and gallium arsenide (GaAs) at room temperature. This means that electrons move extremely fast within InSb, enabling rapid response to external stimuli such as temperature and electric fields, laying the foundation for temperature control and highly sensitive sensing.

[0026] In different temperature environments, the dielectric constant of InSb changes with temperature. Based on this characteristic, the chirality of chiral metamaterial absorbers can be dynamically controlled. In simulation modeling, the Drude model is often used to describe its dielectric constant. The formula is as follows: ; in ; ; Where, is the dielectric constant at high frequency; =15.68, which means that at high frequencies (frequencies much faster than the carrier response rate), InSb approaches the dielectric constant of a "lossless dielectric" state, which is an inherent property of the material; =0.1πTHz, which represents the damping constant, reflecting the energy loss caused by collisions (such as collisions with the lattice and impurities) during carrier motion, and can be approximately constant at room temperature; is the angular frequency in the terahertz band, which is related to the frequency characteristics of the incident light; is an imaginary unit; is the plasma frequency, reflecting the collective oscillation characteristics of carriers and is directly related to the intrinsic carrier concentration; Indicates the intrinsic carrier concentration, which is significantly affected by temperature; represents the charge of a free electron; represents the dielectric constant of vacuum; =0.015 , represents the effective mass of free carriers; , represents the mass of free electrons. Due to the special band structure of InSb, the effective mass is much smaller than the free electron mass, which is the key to its high electron mobility; represents the Boltzmann constant; Indicates absolute temperature, the unit is .

[0027] Temperature by changing ,through Conduction affects dielectric constant , ultimately allowing the chiral response of the absorber (such as absorption peak position, circular dichroism intensity) to change dynamically, which not only supports active control of chiral functions, but also provides a physical basis for temperature sensing and chiral dynamic modulation applications.

[0028] like Figure 1 As shown in (b), in the xy plane, the plane profile of the Z-shaped chiral metal layer 1 is a Z-shaped chiral structure, and the definitions and typical values ​​of various parameters are as follows: Top horizontal rectangular segment: extends in the -x direction (to the left) with a length of , forming the upper edge of the structure. Length Controlled between 50μm and 80μm, this section determines the lateral size of the top of the structure and affects the initial coupling of the terahertz wave and the structure.

[0029] Middle vertical rectangular segment: extends from the right end of the top horizontal rectangular segment in the -y (downward) direction with a length of , connecting the upper edge and the lower edge. Length It is 60μm~90μm, is the main longitudinal extension of the structure, and plays a key role in supporting the resonance mode.

[0030] Left protruding rectangular edge segment: extends from the left end of the top horizontal rectangular edge segment in the -y direction (downward), with a length of , forming a downward bulge on the left side of the upper edge. The diameter is set to 20μm~35μm, and the left-right asymmetry (no corresponding protrusion on the right) strengthens the chiral effect and improves the selectivity for left-handed / right-handed circularly polarized light (LCP / RCP).

[0031] Bottom horizontal rectangular segment: extends from the bottom end of the middle vertical rectangular segment in the +x direction (to the right) with a length of , forming the lower edge of the structure.

[0032] In addition, the width of the top horizontal rectangular segment, the width of the left protruding rectangular segment, the width of the middle vertical rectangular segment, and the width of the bottom horizontal rectangular segment are all , with a value of 15μm~25μm, relates to the energy interaction area between the structure and the incident light.

[0033] Thickness and period: The structure of the temperature-sensitive semiconductor layer 2 is a cube, and its thickness 30μm~60μm; the absorber is a periodic structure, with periods in the x and y directions 、 They are all set to 145μm~155μm, and through periodic arrangement, the macro function is expanded and the sensing consistency is enhanced.

[0034] Example 2: Figure 2As shown, the present invention provides a method for preparing a chiral metamaterial absorber for multifunctional sensing. The method is used to prepare the chiral metamaterial absorber for multifunctional sensing of the first embodiment, and specifically includes: S1: depositing a temperature-sensitive semiconductor layer 2 of a set thickness on a substrate, wherein the material of the layer is indium antimonide; S2: A Z-shaped chiral metal layer 1 of a predetermined thickness is formed on the temperature-sensitive semiconductor layer 2. The Z-shaped chiral metal layer 1 is made of gold. In the xy plane, the Z-shaped chiral metal layer 1 has a Z-shaped chiral structure. Its geometric structure is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows: Top horizontal rectangular edge: extends along the -x direction, with a length of , constituting the upper edge of the structure; Middle vertical rectangular segment: extends from the right end of the top horizontal rectangular segment in the -y direction with a length of , connecting the upper edge and the lower edge; Left protruding rectangular edge segment: extends from the left end of the top horizontal rectangular edge segment along the -y direction, with a length of , forming a downward bulge on the left side of the upper edge; Bottom horizontal rectangular segment: extends from the bottom end of the middle vertical rectangular segment in the +x direction, with a length of , forming the lower edge of the structure; The width of the top horizontal rectangular segment, the width of the left protruding rectangular segment, the width of the middle vertical rectangular segment and the width of the bottom horizontal rectangular segment are all .

[0035] The method for preparing a chiral metamaterial absorber for multifunctional sensing in this embodiment is used to prepare the aforementioned chiral metamaterial absorber for multifunctional sensing. To avoid redundancy, it will not be described here in detail.

[0036] In order to further illustrate the advantages of the present invention, it is described below in conjunction with specific simulations.

[0037] 1. Structural parameters: Z-shaped chiral metal layer 1: , , , , .

[0038] Temperature-sensitive semiconductor layer 2: ,cycle .

[0039] 2. Simulation Verification Initially, the chiral metamaterial absorber was placed in a room temperature environment (300K) and the surrounding medium was set to air (refractive index n=1.0). Using COMSOL simulation software, the optical absorption characteristics of the absorber were simulated and analyzed under the conditions of left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) incident light.

[0040] The optical absorption results obtained from the simulation (corresponding to Figure 3 (a) It can be clearly observed that when LCP light and RCP light are incident separately, the absorber structure exhibits remarkable polarization selectivity: it strongly absorbs RCP light, while it mainly reflects LCP light. The sharp contrast in their light absorption behavior fully demonstrates the structure's differentiated response to light of different circular polarization states.

[0041] Combined with the circular dichroism (CD) analysis results (corresponding to Figure 3 As shown in (b), at frequencies of 1.696 THz and 1.804 THz in the THz band, the CD values ​​approach 80% and 70%, respectively, exhibiting a bimodal chiral effect. This result strongly demonstrates that the absorber structure possesses significant chirally selective absorption capabilities in the THz band, laying the physical foundation for subsequent CD-based spectral temperature sensing and refractive index sensing.

[0042] To explore the cause of the strong circular dichroism (CD) effect of the structure, the electric field distribution of the unit structure at 1.696THz and 1.804THz frequencies was simulated and analyzed at an ambient temperature of 300K. The simulation results show that RCP light is absorbed by the structure, while LCP light is reflected. Figure 4 The physical mechanism of this phenomenon is further presented: under the excitation of LCP light and RCP light, the different color areas at the upper and lower junctions of the structure intuitively demonstrate the accumulation and distribution characteristics of the induced positive and negative charges.

[0043] Specifically, Figure 4 (a) and Figure 4 (c) shows that when the chiral structure is irradiated by LCP light, the electric field distribution is relatively weak at 1.696THz and 1.804THz, with only a weak resonance phenomenon and electric field enhancement trend. In sharp contrast, Figure 4 (b) and Figure 4 In (d), when the RCP light of the above two frequencies is incident vertically, the electric field distribution at the upper and lower junctions of the structure is extremely strong, showing a significantly enhanced resonance response.

[0044] In summary, the surface response of the temperature-sensitive semiconductor layer 2 to RCP light is stronger than to LCP light, manifested by a higher concentrated electric field intensity when excited by RCP light. In fact, this structure strongly couples with the electric field of incident right-handed circularly polarized (RCP) light, generating a dipole resonance response. Consequently, there is a difference in absorption when excited by LCP and RCP light, leading to optically selective absorption and ultimately significant circular dichroism (CD) effects across the dual-band range.

[0045] To further elucidate the intrinsic mechanism of optically selective absorption, simulations were used to obtain the power flow distribution characteristics of the unit structure in the xy plane at z = 0 μm when the external temperature was 300 K and the incident frequencies of left-handed circularly polarized (LCP) light and right-handed circularly polarized (RCP) light were 1.696 THz and 1.804 THz, respectively. The relevant results are shown in the figure below. Figure 5 shown.

[0046] At the two specific frequencies mentioned above, observations revealed that, for both LCP and RCP light, the incident circularly polarized (CP) optical power flow initially formed a parallel flow pattern near the interface between the Z-shaped chiral metal layer 1 and the underlying temperature-sensitive semiconductor layer 2. As the incident circularly polarized light gradually approached and passed through the surface of the unit structure, the majority of the terahertz wave energy ultimately accumulated near the edge region of the evolved Z-shaped chiral structure at z = 0 μm.

[0047] In a Z-shaped chiral structure, for vertically incident LCP light and RCP light, the spatial distribution pattern of the power flow will be different due to the different incident light. Specifically, Figure 4 (a) and Figure 4 As shown in (c), when vertically incident LCP light acts on the unit structure, the spatial distribution of power flow on the structure shows an extremely flat and weak feature, which results in most of the LCP light energy not being absorbed by the structure but being directly reflected. This phenomenon is consistent with the absorption spectrum (see Figure 3 (a)) is highly consistent with the low absorption characteristics of LCP light.

[0048] In sharp contrast, Figure 4 (b) and Figure 4 As shown in (d), at the two resonant frequencies of 1.696THz and 1.804THz, the power flow generated by the vertically incident RCP light around the unit cell structure is extremely strong. At this time, most of the RCP light energy will be concentrated near the bottom edge of the Z-shaped chiral structure and in the internal space, while the remaining energy will flow back to the vicinity of the structure through the substrate and will eventually be dissipated and absorbed by the entire structure. This energy evolution process is consistent with the absorption spectrum (see Figure 3 The high absorption characteristics of RCP light in (a) are also fully matched.

[0049] Through the analysis of the differences in power flow distribution, the energy transfer rules of LCP light and RCP light when interacting with Z-shaped chiral structures are clearly revealed, providing intuitive physical evidence for the optically selective absorption mechanism.

[0050] Figure 6 The refractive index sensing performance of this chiral metamaterial absorber under different ambient refractive indices is presented. Experimental results show that within the wide refractive index range of n = 1.0 to 2.0, the circular dichroism (CD) curves in both the high- and low-frequency bands exhibit a gradual redshift with increasing refractive index, while maintaining a high chiral effect. This performance advantage surpasses most existing designs. The chiral structure's dual narrowband chirally selective absorption properties make it ideal for refractive index (RI) sensing. In practical applications, it can be assumed that the analyte to be detected (e.g., a solution) completely submerges the Z-shaped chiral structure, and sensing can be achieved by monitoring changes in the CD spectrum.

[0051] Figure 6 (a) Shows the CD spectra under different refractive index conditions when the temperature is fixed at 300K: when the refractive index gradually increases from 1.00 to 2.0 (step size of 0.2), the CD peak in the low-frequency band is stably maintained at 0.6~0.8, and the adjustable range of the CD effect is 0.85THz~1.696THz, indicating that the sensor based on the chiral metamaterial absorber (CMA) has good stability and reliability in responding to the analyte in the low-frequency band; in the high-frequency band, as the refractive index increases, the minimum value of the CD peak is 0.4, and the adjustable range of the CD effect is 0.90~1.804THz, which also shows effective response characteristics.

[0052] To further verify its refractive index sensing performance, Figure 6 (b) and Figure 6 (c) shows the relationship between the CD peak frequency f and the refractive index n of the surrounding analyte. The sensitivity of the refractive index sensor is defined as S R =df / dn (unit: THz / RIU), which is the ratio of the change in CD peak frequency df to the change in refractive index dn. The figure of merit (FOM), defined as the ratio of sensitivity to full width at half maximum (FWHM), is used to comprehensively evaluate sensing performance. Linear fitting results show an ideal linear relationship between CD peak frequency and the analyte's refractive index, highly consistent with simulation results. Calculated from the slope of the linear fitting curve, the refractive index sensing sensitivity of this structure is S1 = 0.817 THz / RIU in the low-frequency range and S2 = 0.857 THz / RIU in the high-frequency range, corresponding to FOM1 = 56.41 and FOM2 = 43.3, respectively.

[0053] The above results fully demonstrate that the absorber designed in the present invention has high-quality refractive index sensing performance in the terahertz band, providing a reliable technical solution for wide-range, high-sensitivity refractive index detection applications.

[0054] In order to verify the temperature sensing characteristics of the designed chiral structure, the relationship between the resonance frequency and the ambient temperature change was plotted (e.g. Figure 7 (a)). Simulation results show that the structure can achieve stable temperature sensing and active temperature control functions within a wide range of ambient temperatures, T = 300K to 360K: the circular dichroism (CD) peak in the low-frequency band increases with increasing temperature, while the CD peak in the high-frequency band remains stable, always maintaining near 0.8, fully demonstrating its reliable temperature sensing performance.

[0055] Temperature sensitivity is defined as the resonant frequency shift caused by a unit temperature change, and the expression is S T =df / dT (unit: THz / K), which is used to quantify the linear relationship between the ambient temperature change dT and the resonant frequency shift df; the quality factor (FOM) is defined as the ratio of sensitivity to full width at half maximum (FWHM), which is a key indicator for comprehensive evaluation of sensing performance. Figure 7 (b) and Figure 7 The linear fitting results of (c) show that there is a good linear relationship between the resonant frequency and the ambient temperature. The slope of the fitting curve is the temperature sensitivity: low-frequency temperature sensitivity S T1 =1.46THz / K, corresponding quality factor FOM1=103.51; high frequency temperature sensitivity S T2 =1.07THz / K, corresponding to a quality factor FOM2=82.8. This performance is comparable to similar designs, indicating that the structure can be used as a dual-frequency temperature sensor with excellent performance in the terahertz band.

[0056] Furthermore, the structure maintains high sensitivity across a wide refractive index and temperature sensing range, with an excellent Q factor (a key indicator of sensor performance, defined as the ratio of the initial resonance peak frequency f to the full width at half maximum (FWHM)): Q1 = 117.04 in the low-frequency range and Q2 = 91.4 in the high-frequency range. Considering the significant dissipation inherent in metal materials, a Q factor approaching 100 is considered excellent, ensuring efficient sensing performance.

[0057] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A chiral metamaterial absorber for multifunctional sensing, characterized in that: include: A periodically arranged three-dimensional double-layer unit structure, each unit structure consists of a Z-shaped chiral metal layer and a temperature-sensitive semiconductor layer from top to bottom; The material of the Z-shaped chiral metal layer is gold. In the xy plane, the plane profile of the Z-shaped chiral metal layer is a Z-shaped chiral structure. Its geometric structure is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows: Top horizontal rectangular edge: extends along the -x direction, with a length of , constituting the upper edge of the structure; Middle vertical rectangular segment: extends from the right end of the top horizontal rectangular segment in the -y direction with a length of , connecting the upper edge and the lower edge; Left protruding rectangular edge segment: extends from the left end of the top horizontal rectangular edge segment along the -y direction, with a length of , forming a downward bulge on the left side of the upper edge; Bottom horizontal rectangular segment: extends from the bottom end of the middle vertical rectangular segment in the +x direction, with a length of , forming the lower edge of the structure; The width of the top horizontal rectangular segment, the width of the left protruding rectangular segment, the width of the middle vertical rectangular segment and the width of the bottom horizontal rectangular segment are all ; The material of the temperature-sensitive semiconductor layer is indium antimonide, and its dielectric constant changes dynamically with temperature, thereby realizing active regulation of circular dichroism in the terahertz band.

2. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that: The period of the unit structure is 145 μm to 155 μm.

3. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that: The thickness of the Z-shaped chiral metal layer 30μm~60μm.

4. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that: The structure of the temperature-sensitive semiconductor layer is a cube, and its thickness is 30μm~60μm.

5. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that: described 15μm~25μm.

6. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that: described 50μm~80μm.

7. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that: described 60μm~90μm.

8. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that: described 20μm~35μm.

9. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that: The dielectric constant of the temperature-sensitive semiconductor layer satisfies the Drude model: ； in ； ； Where, is the dielectric constant at high frequency; =15.68; =0.1πTHz, indicating the damping constant; is the angular frequency in the terahertz band; is an imaginary unit; is the plasma frequency; represents the intrinsic carrier concentration; represents the charge of a free electron; represents the dielectric constant of vacuum; =0.015 , represents the effective mass of free carriers; , represents the mass of a free electron; represents the Boltzmann constant; Indicates absolute temperature, the unit is .

10. A method for preparing a chiral metamaterial absorber for multifunctional sensing, characterized in that: The method is used to prepare the chiral metamaterial absorber for multifunctional sensing according to any one of claims 1 to 9, comprising: Depositing a temperature-sensitive semiconductor layer of a set thickness on a substrate, wherein the material of the layer is indium antimonide; A Z-shaped chiral metal layer of a predetermined thickness is formed on the temperature-sensitive semiconductor layer. The material of the Z-shaped chiral metal layer is gold. In the xy plane, the Z-shaped chiral metal layer has a planar profile of a Z-shaped chiral structure. The geometric structure of the Z-shaped chiral metal layer is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows: Top horizontal rectangular edge: extends along the -x direction, with a length of , constituting the upper edge of the structure; Middle vertical rectangular segment: extends from the right end of the top horizontal rectangular segment in the -y direction with a length of , connecting the upper edge and the lower edge; Left protruding rectangular edge segment: extends from the left end of the top horizontal rectangular edge segment along the -y direction, with a length of , forming a downward bulge on the left side of the upper edge; Bottom horizontal rectangular segment: extends from the bottom end of the middle vertical rectangular segment in the +x direction, with a length of , forming the lower edge of the structure; The width of the top horizontal rectangular segment, the width of the left protruding rectangular segment, the width of the middle vertical rectangular segment and the width of the bottom horizontal rectangular segment are all .

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