Chiral metamaterial absorber for multifunctional sensing and preparation method thereof

Abstract

The application provides a chiral metamaterial absorber for multifunctional sensing and a preparation method thereof, and relates to the technical field of optics.The absorber comprises a periodically arranged three-dimensional double-layer unit structure, each unit structure sequentially comprises 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; the material of the temperature-sensitive semiconductor layer is indium antimonide, the dielectric constant of which dynamically changes with temperature, thereby realizing active regulation of circular dichroism in the terahertz wave band.The application realizes strong chiral selective absorption in the terahertz wave band through the periodic three-dimensional structure of the Z-shaped chiral metal layer and the temperature-sensitive semiconductor layer, and has high-sensitivity temperature sensing at 300K-360K and a wide-range refractive index of 1.0-2.0, and high-quality factor guarantees efficient integrated functions.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a chiral metamaterial absorber for multifunctional sensing and its fabrication method. Background Technology

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

[0003] To overcome these limitations, researchers have proposed chiral metamaterials, whose optical properties primarily depend on microstructure design rather than intrinsic material properties. Through geometric structure and electromagnetic resonance modulation, chiral response can be significantly enhanced, playing a crucial role in fields such as chemical monitoring and biosensing. In recent years, the design of chiral metamaterial sensors has shown three major trends:

[0004] 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, in order to reduce losses and improve quality factor;

[0005] Active regulation: 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;

[0006] Multifunctional integration: It combines wide-range sensing, high sensitivity and high quality factor, such as simultaneously achieving dual parameter sensing of temperature and refractive index.

[0007] However, existing technologies still have significant drawbacks:

[0008] Functional limitations: Some terahertz band chiral metamaterials are designed only as switchable switches, lacking dynamic control capabilities and integrated sensing-absorption functions;

[0009] Limited applicability: Most structures are difficult to achieve high-sensitivity sensing over a wide range of temperatures or refractive indices;

[0010] Performance imbalance: It is difficult to achieve high quality factor, high sensitivity and wide sensing range at the same time.

[0011] Therefore, there is an urgent need to develop a chiral metamaterial absorber that combines wide-range dynamic control, dual-function high-efficiency sensing (temperature / refractive index), and high-quality factor to meet the multifunctional sensing requirements in complex environments. Summary of the Invention

[0012] To address these issues, this invention provides a chiral metamaterial absorber for multifunctional sensing and its fabrication method, thereby solving the problems of lack of dynamic control, single sensing function, and difficulty in achieving both wide range and high sensitivity in the prior art.

[0013] To address the above problems, embodiments of the present invention provide a chiral metamaterial absorber for multifunctional sensing, comprising:

[0014] The three-dimensional double-layer unit structure is arranged periodically, and each unit structure consists of a Z-shaped chiral metal layer and a temperature-sensitive semiconductor layer from top to bottom.

[0015] The Z-shaped chiral metal layer is made of gold. In the xy plane, the planar profile of the Z-shaped chiral metal layer is a Z-shaped chiral structure, whose geometric composition is decomposed into four orthogonally connected rectangular segments, with the following specific characteristics:

[0016] Top horizontal rectangular segment: extends along the -x direction, with a length of... It forms the upper edge of the structure;

[0017] The middle vertical rectangle segment: extends from the right end of the top horizontal rectangle segment along the -y direction, with a length of... Connect the top edge and the bottom edge;

[0018] Left protruding rectangular segment: Extends from the left end of the top horizontal rectangular segment along the -y direction, with a length of... This forms a downward bulge on the left side of the upper edge;

[0019] Bottom horizontal rectangle segment: Extends from the bottom end of the middle vertical rectangle segment along the +x direction, with a length of... It forms the lower edge of the structure;

[0020] Furthermore, the widths of the top horizontal rectangular segment, the left protruding rectangular segment, the middle vertical rectangular segment, and the bottom horizontal rectangular segment are all... ;

[0021] The temperature-sensitive semiconductor layer is made of indium antimonide, and its dielectric constant changes dynamically with temperature, enabling active control of the circular dichroism in the terahertz band.

[0022] Preferably, the period of the unit structure is 145μm~155μm.

[0023] Preferably, the thickness of the Z-shaped chiral metal layer The range is 30μm to 60μm.

[0024] Preferably, the temperature-sensitive semiconductor layer has a cubic structure and a thickness of [missing information]. The range is 30μm to 60μm.

[0025] Preferably, the The size ranges from 15μm to 25μm.

[0026] Preferably, the The size ranges from 50μm to 80μm.

[0027] Preferably, the The size ranges from 60μm to 90μm.

[0028] Preferably, the The range is 20μm to 35μm.

[0029] Preferably, the dielectric constant of the temperature-sensitive semiconductor layer satisfies the Drude model:

[0030] ;

[0031] in

[0032] ;

[0033] ;

[0034] In the formula, The dielectric constant at high frequencies; =15.68; =0.1πTHz, representing the damping constant; This refers to the angular frequency in the terahertz band. The imaginary unit; The plasma frequency; Indicates intrinsic carrier concentration; Indicates the charge of a free electron; Represents the vacuum permittivity; =0.015 , representing the effective mass of free charge carriers; , representing the mass of a free electron; Represents the Boltzmann constant; This represents absolute temperature, and the unit is... .

[0035] This invention also provides a method for fabricating a chiral metamaterial absorber for multifunctional sensing. This method, used to fabricate the aforementioned chiral metamaterial absorber for multifunctional sensing, includes:

[0036] A temperature-sensitive semiconductor layer of a predetermined thickness is deposited on the substrate, and the material is indium antimonide;

[0037] A Z-shaped chiral metal layer of a predetermined thickness is fabricated on the temperature-sensitive semiconductor layer. The material of the layer is gold. In the xy plane, the planar contour of the Z-shaped chiral metal layer is a Z-shaped chiral structure, and its geometric composition is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows:

[0038] Top horizontal rectangular segment: extends along the -x direction, with a length of... It forms the upper edge of the structure;

[0039] The middle vertical rectangle segment: extends from the right end of the top horizontal rectangle segment along the -y direction, with a length of... Connect the top edge and the bottom edge;

[0040] Left protruding rectangular segment: Extends from the left end of the top horizontal rectangular segment along the -y direction, with a length of... This forms a downward bulge on the left side of the upper edge;

[0041] Bottom horizontal rectangle segment: Extends from the bottom end of the middle vertical rectangle segment along the +x direction, with a length of... It forms the lower edge of the structure;

[0042] Furthermore, the widths of the top horizontal rectangular segment, the left protruding rectangular segment, the middle vertical rectangular segment, and the bottom horizontal rectangular segment are all... .

[0043] As can be seen from the above technical solutions, this invention application has the following beneficial effects:

[0044] (1) This invention achieves dynamic control of the 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 to 360K, the intrinsic carrier concentration of indium antimonide (InSb) changes exponentially with temperature, affecting the dielectric constant through plasma frequency, thus causing a linear shift in the resonance frequency of the chiral metamaterial absorption spectrum. Data shows 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. Furthermore, the low-frequency CD peak steadily increases with increasing temperature, while the high-frequency CD peak remains around 0.8. This synergistic design of "active control + high-sensitivity sensing" overcomes the environmental adaptability limitations of traditional passive control structures and can meet the stable sensing requirements under complex temperature environments.

[0045] (2) The Z-shaped chiral metal layer of this invention enhances the coupling between light and structure through geometric asymmetry, achieving efficient refractive index sensing over a wide range of 1.0 to 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 to 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 0.817 THz / RIU, and the high-frequency sensitivity reaches 0.857 THz / RIU, with quality factors of 56.41 and 43.3, respectively. This performance is superior to most existing designs, and the dual-frequency response can achieve multi-parameter cross-validation, significantly improving sensing reliability.

[0046] (3) The asymmetrical design of the Z-shaped chiral metal layer in this invention (the left protrusion has no corresponding structure on the right) significantly enhances the circular dichroism (CD) effect, forming a double-peak CD value at 1.696 THz and 1.804 THz in the terahertz band, reaching as high as 80% and 70% respectively. It exhibits strong selective absorption of left-handed (LCP) and right-handed (RCP) circularly polarized light (strong absorption of RCP, strong reflection of LCP). At the same time, the high quality factor (Q factor) of the structure ensures efficient sensing: Q1=117.04 at low frequency and Q2=91.4 at high frequency. In the case of inherent dissipation in the metal material, the Q factor close to 100 effectively reduces signal interference and ensures high resolution of temperature and refractive index sensing. This characteristic of "strong chirality + high Q factor" enables a single structure to simultaneously realize the three major functions of chiral absorption, temperature sensing, and refractive index sensing, greatly improving the integration of the device and its adaptability to application scenarios. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Referring to the drawings will make the features and advantages of the present invention clearer. The drawings are illustrative and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0048] Figure 1 The present invention provides a schematic diagram of a chiral metamaterial absorber for multifunctional sensing, wherein (a) is a three-dimensional view of the absorber and (b) is a two-dimensional planar view of the absorber.

[0049] Figure 2 A flowchart of a method for fabricating a chiral metamaterial absorber for multifunctional sensing provided by the present invention;

[0050] Figure 3This is a schematic diagram of the differential absorption of chiral metamaterial absorbers for left- and right-handed circularly polarized light in an embodiment of the present invention, wherein (a) is the simulated optical absorption spectrum of the metamaterial under LCP and RCP light incident light, and (b) is the simulated circular dichroism spectrum.

[0051] Figure 4 This is a schematic diagram of the electric field distribution (xyz plane) in the unit structure proposed in this invention under an external temperature of 300K, where (a) is a schematic diagram of incident LCP light with a frequency of 1.696 THz; (b) is a schematic diagram of incident RCP light with a frequency of 1.696 THz; (c) is a schematic diagram of incident LCP light with a frequency of 1.806 THz; and (d) is a schematic diagram of incident RCP light with a frequency of 1.806 THz.

[0052] Figure 5 This is a schematic diagram of the power flow distribution of the proposed unit structure at z=0μm in the xy plane under an external temperature of 300K in an embodiment of the present invention. (a) is a schematic diagram of incident LCP light at a frequency of 1.696THz; (b) is a schematic diagram of incident RCP light at a frequency of 1.696THz; (c) is a schematic diagram of incident LCP light at a frequency of 1.806THz; and (d) is a schematic diagram of incident RCP light at a frequency of 1.806THz.

[0053] Figure 6 The diagram shows the refractive index sensing performance of the absorber of the present invention under different refractive indices in an embodiment of the present invention, wherein (a) is the CD spectrum designed under different environmental refractive indices; (b) is the low-frequency variation with refractive index and its corresponding linear fitting curve; and (c) is the high-frequency variation with refractive index and its corresponding linear fitting curve.

[0054] Figure 7 This is a graph showing the relationship between the resonant frequency of the absorber of the present invention and the change in ambient temperature in an embodiment of the present invention. (a) is a schematic diagram of the CD spectrum designed under different ambient temperatures; (b) shows the change in low frequency with ambient temperature and its corresponding linear fitting curve; (c) shows the change in high frequency with ambient temperature and its corresponding linear fitting curve.

[0055] Explanation of reference numerals in the accompanying drawings: 1. Z-shaped chiral metal layer; 2. Temperature-sensitive semiconductor layer. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] Example 1: To address the problems in existing technologies such as lack of dynamic control, limited sensing functionality, and difficulty in simultaneously achieving wide range and high sensitivity. For example... Figure 1 As shown, this invention proposes a chiral metamaterial absorber for multifunctional sensing, comprising:

[0058] A periodically arranged three-dimensional double-layer unit structure, each unit structure consisting of a Z-shaped chiral metal layer 1 and a temperature-sensitive semiconductor layer 2 from top to bottom;

[0059] The Z-shaped chiral metal layer 1 is made of gold. In the xy plane, the planar profile of the Z-shaped chiral metal layer 1 is a Z-shaped chiral structure, and its geometric composition is decomposed into four orthogonally connected rectangular segments, with the following specific characteristics:

[0060] Top horizontal rectangular segment: extends along the -x direction, with a length of... It forms the upper edge of the structure;

[0061] Left protruding rectangular segment: Extends from the left end of the top horizontal rectangular segment along the -y (downward) direction, with a length of... This forms a downward bulge on the left side of the upper edge;

[0062] The middle vertical rectangle segment: extends from the right end of the top horizontal rectangle segment along the -y (downward) direction, with a length of... Connect the top edge and the bottom edge;

[0063] Bottom horizontal rectangle segment: Extends from the bottom end of the middle vertical rectangle segment along the +x (right) direction, with a length of... It forms the lower edge of the structure;

[0064] Furthermore, the widths of the top horizontal rectangle, the left protruding rectangle, the middle vertical rectangle, and the bottom horizontal rectangle are all... ;

[0065] The temperature-sensitive semiconductor layer 2 is made of indium antimonide, and its dielectric constant changes dynamically with temperature, enabling active control of the circular dichroism in the terahertz band.

[0066] As can be seen from the above technical solution, this invention proposes a chiral metamaterial absorber for multifunctional sensing, employing a periodically arranged three-dimensional double-layer unit structure, consisting of a Z-shaped chiral metal layer 1 (gold) and a temperature-sensitive semiconductor layer 2 (indium antimonide) from top to bottom. The Z-shaped chiral metal layer 1 enhances the chiral effect through an orthogonal asymmetric design of a top horizontal rectangular side segment, a left protruding rectangular side segment, a middle vertical rectangular side segment, and a bottom horizontal rectangular side segment. The temperature-sensitive semiconductor layer achieves dynamic control based on the temperature sensitivity of the InSb dielectric constant. This scheme achieves a dual-peak CD value (80% and 70%) in the terahertz band, enabling wide-range temperature sensing (sensitivity 1.07 THz / K ~ 1.46 THz / K) and wide-range refractive index sensing (sensitivity 0.817 THz / RIU ~ 0.857 THz / RIU) from 300K to 360K. Furthermore, a high Q factor (nearly 100) ensures high resolution, achieving chiral absorption, dual-parameter sensing integration, and wide-range stable response.

[0067] like Figure 1 As shown in (a), the absorber is layered along the z-axis. The upper layer of the absorber is a Z-shaped chiral metal layer 1, made of the noble metal gold (Au). Gold has a high resonant displacement capability, which can effectively enhance the light-structure interaction in the terahertz band; its excellent biocompatibility is suitable for biosensing scenarios, and its chemical stability ensures the structural reliability in the sensing environment, making it less susceptible to corrosion and oxidation. The structural morphology of this Z-shaped chiral metal layer 1 is similar to the letter Z, but it differs from the traditional simple Z-shaped chiral structure. By strengthening the geometric asymmetry in the left-right direction (such as a specific protrusion on one side and no corresponding structure on the other side), differential absorption is enhanced to a certain extent.

[0068] The lower layer is the temperature-sensitive semiconductor layer 2, with indium antimonide (InSb) as the temperature control material. InSb is a narrow bandgap semiconductor with a bandgap of approximately 0.17 eV at room temperature (300 K). This characteristic makes its intrinsic carrier concentration extremely sensitive to temperature. Meanwhile, InSb possesses the highest electron mobility among all common semiconductors, far exceeding that of silicon and gallium arsenide (GaAs) at room temperature. This means that electrons move extremely fast within InSb, facilitating rapid response to external stimuli such as temperature and electric fields, thus laying the foundation for temperature control and highly sensitive sensing.

[0069] The dielectric constant of InSb changes with temperature under different environmental conditions. Based on this characteristic, the chirality of chiral metamaterial absorbers can be dynamically controlled. In simulation modeling, the Drude model is commonly used to describe its dielectric constant, as shown in the following formula:

[0070] ;

[0071] in

[0072] ;

[0073] ;

[0074] In the formula, The dielectric constant at high frequencies; =15.68, which represents the dielectric constant of InSb at high frequencies (the frequency is much faster than the carrier response rate), approaching the "lossless medium" state, which is an inherent property of the material; =0.1πTHz, representing the damping constant, which reflects the energy loss caused by collisions (such as collisions with the lattice and impurities) during the movement of charge carriers. It can be approximated as a constant value at room temperature. The angular frequency in the terahertz band is associated with the frequency characteristics of the incident light. The imaginary unit; The plasma frequency reflects the collective oscillation characteristics of charge carriers and is directly related to the intrinsic charge carrier concentration. This represents the intrinsic carrier concentration, which is significantly affected by temperature. Indicates the charge of a free electron; Represents the vacuum permittivity; =0.015 , representing the effective mass of free carriers; , which represents the mass of free electrons. Due to its special band structure, the effective mass of InSb is much smaller than the mass of free electrons, which is the key to its high electron mobility. Represents the Boltzmann constant; This represents absolute temperature, and the unit is... .

[0075] Temperature by changing ,through Conduction affects dielectric constant Ultimately, this allows the chiral response of the absorber (such as the position of the absorption peak and the intensity of circular dichroism) to change dynamically, which not only supports active chiral modulation but also provides a physical basis for temperature sensing and dynamic chiral modulation applications.

[0076] like Figure 1 As shown in (b), in the xy plane, the planar profile of the Z-shaped chiral metal layer 1 is a Z-shaped chiral structure. The parameters are defined and have typical values:

[0077] Top horizontal rectangular segment: extends along the -x direction (to the left), with a length of... This forms the upper edge of the structure. Length The diameter is controlled within 50μm to 80μm. This range determines the lateral dimension at the top of the structure and affects the initial coupling between the terahertz wave and the structure.

[0078] The middle vertical rectangle segment: extends from the right end of the top horizontal rectangle segment along the -y (downward) direction, with a length of... Connect the top and bottom edges. Length The length is 60μm~90μm, which is the main longitudinal extension of the structure and plays a key role in supporting the resonance mode.

[0079] Left protruding rectangular segment: Extends from the left end of the top horizontal rectangular segment along the -y direction (downwards), with a length of... This forms a downward bulge on the left side of the upper edge. Length With a focal length of 20μm~35μm, the chiral effect is enhanced by left-right asymmetry (no corresponding protrusion on the right side), thereby improving the selectivity for left-handed / right-handed circularly polarized light (LCP / RCP).

[0080] Bottom horizontal rectangle segment: Extends from the bottom end of the middle vertical rectangle segment along the +x direction (to the right), with a length of... , which forms the lower edge of the structure.

[0081] In addition, the widths of the top horizontal rectangle, the left protruding rectangle, the middle vertical rectangle, and the bottom horizontal rectangle are all... The value ranges from 15μm to 25μm, representing the energy interaction area between the associated structure and the incident light.

[0082] Thickness and Periodicity: The structure of the temperature-sensitive semiconductor layer 2 is a cube, and its thickness is... The absorber has a diameter of 30μm to 60μm and is a periodic structure with periodicity in the x and y directions. , All are set to 145μm~155μm, and through periodic arrangement, macroscopic functions are expanded and sensing consistency is enhanced.

[0083] Example 2: Figure 2 As shown, this invention provides a method for fabricating a chiral metamaterial absorber for multifunctional sensing. This method is used to fabricate the chiral metamaterial absorber for multifunctional sensing described in Example 1 above, and specifically includes:

[0084] S1: A temperature-sensitive semiconductor layer 2 of a predetermined thickness is deposited on the substrate, and the material is indium antimonide;

[0085] S2: A Z-shaped chiral metal layer 1 of a predetermined thickness is prepared on the temperature-sensitive semiconductor layer 2. The material of the layer is gold. In the xy plane, the planar contour of the Z-shaped chiral metal layer 1 is a Z-shaped chiral structure, and its geometric composition is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows:

[0086] Top horizontal rectangular segment: extends along the -x direction, with a length of... It forms the upper edge of the structure;

[0087] The middle vertical rectangle segment: extends from the right end of the top horizontal rectangle segment along the -y direction, with a length of... Connect the top edge and the bottom edge;

[0088] Left protruding rectangular segment: Extends from the left end of the top horizontal rectangular segment along the -y direction, with a length of... This forms a downward bulge on the left side of the upper edge;

[0089] Bottom horizontal rectangle segment: Extends from the bottom end of the middle vertical rectangle segment along the +x direction, with a length of... It forms the lower edge of the structure;

[0090] Furthermore, the widths of the top horizontal rectangle, the left protruding rectangle, the middle vertical rectangle, and the bottom horizontal rectangle are all... .

[0091] This embodiment describes a method for fabricating a chiral metamaterial absorber for multifunctional sensing, which is used to fabricate the aforementioned chiral metamaterial absorber for multifunctional sensing. To avoid redundancy, it will not be described again here.

[0092] To further illustrate the advantages of this invention, the following description is based on specific simulations.

[0093] 1. Structural parameters:

[0094] Z-shaped chiral metal layer 1: , , , , .

[0095] Temperature-sensitive semiconductor layer 2: ,cycle .

[0096] 2. Simulation Verification

[0097] In the initial state, 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 under left-handed circularly polarized light (LCP) and right-handed circularly polarized light (RCP) incident conditions were simulated and analyzed.

[0098] 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 respectively, the absorber structure exhibits significant polarization selectivity: it strongly absorbs RCP light, while it mainly reflects LCP light. The two exhibit a great contrast in light absorption behavior, fully demonstrating the structure's differentiated response to light with different circular polarization states.

[0099] Combined with the results of circular dichroism (CD) analysis (corresponding to) Figure 3 (b) shows that at frequencies of 1.696 THz and 1.804 THz in the terahertz band, the CD values ​​approach 80% and 70%, respectively, exhibiting a bimodal chiral effect. This result strongly demonstrates that the absorber structure possesses significant chiral selective absorption capability in the terahertz band, laying the physical foundation for subsequent temperature sensing and refractive index sensing functions based on CD spectroscopy.

[0100] To investigate the cause of the strong circular dichroism (CD) effect in this structure, the electric field distribution of the unit cell structure at frequencies of 1.696 THz and 1.804 THz was simulated and analyzed at an ambient temperature of 300 K. 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 was further revealed: under LCP and RCP light excitation, the different colored regions at the upper and lower boundaries of the structure visually demonstrated the accumulation and distribution characteristics of the induced positive and negative charges.

[0101] Specifically, Figure 4 (a) and Figure 4 (c) shows that when the chiral structure is irradiated with LCP light, the electric field distribution is relatively weak at frequencies of 1.696 THz and 1.804 THz, with only a weak resonance phenomenon and a tendency for the electric field to strengthen. This contrasts sharply with... Figure 4 (b) and Figure 4 In (d), when the RCP light of the two frequencies mentioned above is incident perpendicularly, the electric field distribution at the junction of the upper and lower parts of the structure is extremely strong, exhibiting a significantly enhanced resonance response.

[0102] In summary, the surface of the temperature-sensitive semiconductor layer 2 responds more strongly to RCP light than to LCP light, exhibiting a higher electric field intensity when excited by RCP light. In fact, this structure can strongly couple with the electric field of incident right-handed circularly polarized (RCP) light, thereby generating a dipole resonance response. Therefore, the absorption differs between LCP and RCP light excitation, leading to optically selective absorption and ultimately a significant circular dichroism (CD) effect across the dual-band range.

[0103] To further elucidate the intrinsic mechanism of optically selective absorption, simulations were used to obtain the power flow distribution characteristics of the unit cell structure in the xy plane at z=0 μm under the incident conditions of left-handed circularly polarized (LCP) light with frequencies of 1.696 THz and right-handed circularly polarized (RCP) light with frequencies of 1.804 THz and 1.696 THz, respectively, at an external temperature of 300 K. The relevant results are as follows: Figure 5 As shown.

[0104] At the two specific frequencies mentioned above, observations revealed that, regardless of whether it is LCP or RCP light, the incident circularly polarized (CP) light power flow initially forms a parallel flow pattern near the boundary space between the Z-shaped chiral metal layer 1 and the lower temperature-sensitive semiconductor layer 2. As the incident circularly polarized light gradually approaches and passes through the surface of the unit cell structure, most of the terahertz wave energy eventually concentrates near the edge region of the evolved Z-shaped chiral structure at z=0μm.

[0105] In Z-shaped chiral structures, the spatial distribution pattern of power flow differs depending on the incident light for perpendicularly incident LCP and RCP light. Specifically, for example... Figure 4 (a) and Figure 4 As shown in (c), when perpendicularly incident LCP light acts on the unit cell structure, the spatial distribution of the power flow on the structure exhibits extremely flat and weak characteristics. This 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 absorption spectrum). Figure 3 The low absorption characteristics of LCP light in (a) are highly consistent.

[0106] In stark contrast, such as Figure 4 (b) and Figure 4 As shown in (d), at the resonant frequencies of 1.696 THz and 1.804 THz, the power flow generated around the unit cell structure by the perpendicularly incident RCP light is extremely strong. At this time, most of the energy of the RCP light is concentrated near the bottom edge of the Z-shaped chiral structure and in the internal space, while the remaining energy flows back to the vicinity of the structure through the substrate and is eventually dissipated and absorbed by the entire structure. This energy evolution process is related to the absorption spectrum (see...). Figure 3 The high absorption characteristics of RCP light in (a) are also perfectly matched.

[0107] By analyzing the differences in power flow distribution, the energy transfer laws of LCP and RCP light when interacting with Z-shaped chiral structures were clearly revealed, providing intuitive physical evidence for the optical rotation selective absorption mechanism.

[0108] Figure 6The refractive index sensing performance of this chiral metamaterial absorber under different environmental refractive indices is presented. Experimental results show that, within a wide refractive index range of n = 1.0–2.0, the circular dichroism (CD) curves in both high and low frequency bands exhibit a gradual redshift trend with increasing refractive index, while maintaining a consistently high chiral effect. This performance advantage surpasses that of most existing designs. Due to its dual narrow-band chiral selective absorption characteristics, this chiral structure is highly suitable for refractive index (RI) sensing applications. In practical applications, it can be assumed that the analyte (such as a solution) completely submerges the Z-shaped chiral structure, and sensing can be achieved by monitoring changes in the CD spectrum.

[0109] Figure 6 (a) shows the CD spectra under different refractive index conditions when the temperature is fixed at 300K: when the refractive index is gradually increased from 1.00 to 2.0 (step size of 0.2), the CD peak value 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 chiral metamaterial absorber (CMA) has good stability and reliability in response to analytes in the low frequency band; in the high frequency band, with the increase of refractive index, the lowest CD peak value is 0.4, and the adjustable range of the CD effect is 0.90~1.804THz, which also shows effective response characteristics.

[0110] To further verify its refractive index sensing performance, Figure 6 (b) and Figure 6 (c) The curve showing the relationship between the CD peak frequency f and the refractive index n of the surrounding analyte is presented. 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 quality factor (FOM) is defined as the ratio of sensitivity to full width at half maximum (FWHM), used to comprehensively evaluate sensing performance. Linear fitting results show an ideal linear relationship between the CD peak frequency and the refractive index of the analyte, highly consistent with simulation results. Calculations based on the slope of the linear fitting curves show that 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, with corresponding quality factors of FOM1=56.41 and FOM2=43.3, respectively.

[0111] The above results fully demonstrate that the absorber designed in this 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.

[0112] To verify the temperature sensing characteristics of the designed chiral structure, a curve showing the relationship between the resonant frequency and the ambient temperature was plotted (e.g., Figure 7(a) As shown in the simulation results, the structure can achieve stable temperature sensing and active temperature control functions within a wide range of ambient temperature T=300K~360K: the peak value of circular dichroism (CD) in the low-frequency band increases with increasing temperature, while the peak value of CD in the high-frequency band remains stable, always maintained at around 0.8, which fully demonstrates its reliable temperature sensing performance.

[0113] Temperature sensitivity is defined as the resonant frequency shift caused by a unit temperature change, expressed as S. T =df / dT (unit: THz / K), 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), and is a key indicator for comprehensively evaluating sensor performance. From Figure 7 (b) and Figure 7 (c) The linear fitting results 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 to a 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 this structure can serve as a dual-frequency temperature sensor with excellent performance in the terahertz band.

[0114] Furthermore, this structure maintains high sensitivity across a wide refractive index and temperature sensing range, and exhibits excellent Q-factor (an important indicator of sensor performance, defined as the ratio of the initial resonance 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 metallic materials, a Q-factor approaching 100 is already considered excellent, ensuring the structure achieves high-efficiency sensing performance.

[0115] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A chiral metamaterial absorber for multifunctional sensing, characterized in that, include: The three-dimensional double-layer unit structure is arranged periodically, and each unit structure consists of a Z-shaped chiral metal layer and a temperature-sensitive semiconductor layer from top to bottom. The Z-shaped chiral metal layer is made of gold. In the xy plane, the planar profile of the Z-shaped chiral metal layer is a Z-shaped chiral structure, whose geometric composition is decomposed into four orthogonally connected rectangular segments, with the following specific characteristics: Top horizontal rectangular segment: extends along the -x direction, with a length of... It forms the upper edge of the structure; The middle vertical rectangle segment: extends from the right end of the top horizontal rectangle segment along the -y direction, with a length of... Connect the top edge and the bottom edge; Left protruding rectangular segment: Extends from the left end of the top horizontal rectangular segment along the -y direction, with a length of... This forms a downward bulge on the left side of the upper edge; Bottom horizontal rectangle segment: Extends from the bottom end of the middle vertical rectangle segment along the +x direction, with a length of... It forms the lower edge of the structure; Furthermore, the widths of the top horizontal rectangular segment, the left protruding rectangular segment, the middle vertical rectangular segment, and the bottom horizontal rectangular segment are all... ; The temperature-sensitive semiconductor layer is made of indium antimonide, and its dielectric constant dynamically changes with temperature, enabling active modulation of circular dichroism in the terahertz band. The dielectric constant of the temperature-sensitive semiconductor layer satisfies the Drude model. ； in ； ； In the formula, The dielectric constant at high frequencies; =15.68; =0.1πTHz, representing the damping constant; This refers to the angular frequency in the terahertz band. The imaginary unit; The plasma frequency; Indicates intrinsic carrier concentration; Indicates the charge of a free electron; Represents the vacuum permittivity; =0.015 , representing the effective mass of free carriers; , representing the mass of a free electron; Represents the Boltzmann constant; This represents absolute temperature, and the unit is... .

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

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

4. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that, The temperature-sensitive semiconductor layer has a cubic structure and a thickness of [missing information]. The range is 30μm to 60μm.

5. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that, The The size ranges from 15μm to 25μm.

6. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that, The The size ranges from 50μm to 80μm.

7. The chiral metamaterial absorber for multifunctional sensing according to claim 1, characterized in that, The The size ranges from 60μm to 90μm.

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

9. A method for fabricating 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 8, comprising: A temperature-sensitive semiconductor layer of a predetermined thickness is deposited on the substrate, and the material is indium antimonide; A Z-shaped chiral metal layer of a predetermined thickness is fabricated on the temperature-sensitive semiconductor layer. The material of the layer is gold. In the xy plane, the planar contour of the Z-shaped chiral metal layer is a Z-shaped chiral structure, and its geometric composition is decomposed into four orthogonally connected rectangular segments. The specific characteristics are as follows: Top horizontal rectangular segment: extends along the -x direction, with a length of... It forms the upper edge of the structure; The middle vertical rectangle segment: extends from the right end of the top horizontal rectangle segment along the -y direction, with a length of... Connect the top edge and the bottom edge; Left protruding rectangular segment: Extends from the left end of the top horizontal rectangular segment along the -y direction, with a length of... This forms a downward bulge on the left side of the upper edge; Bottom horizontal rectangle segment: Extends from the bottom end of the middle vertical rectangle segment along the +x direction, with a length of... It forms the lower edge of the structure; Furthermore, the widths of the top horizontal rectangular segment, the left protruding rectangular segment, the middle vertical rectangular segment, and the bottom horizontal rectangular segment are all... .

Images