Active regulation and control flexible dual-channel switchable terahertz modulator

Abstract

The invention discloses an active regulation and control flexible dual-channel switchable terahertz modulator, the modulator is composed of a flexible substrate layer and a metasurface structure, the flexible substrate layer is made of a polyimide material, the metasurface structure is composed of vanadium dioxide and a metal material, a vertical I-shaped periodic pattern is formed, the periodic size is 120 [mu] m * 120 [mu] m, and the width of the metasurface structure is 20 [mu] m * 20 [mu] m. The minimum side length of the pattern unit is 10 [mu] m, and the thickness of the metasurface structure is 200 nm. The phase change between the insulation state and the metal state of the vanadium dioxide is realized through external temperature regulation and control; according to the invention, the functions of low-temperature total-transmission and high-temperature dual-resonance dynamic switching in the 0.1-2 THz frequency band are realized, and the dynamic switching device can be applied to the terahertz wave band.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz band dynamic regulation, and in particular to an actively regulated flexible dual-channel switchable terahertz modulator. Background Art

[0002] Vanadium dioxide (VO2) is a functional material with excellent performance. It can undergo a reversible phase transition from an insulating state to a metallic state at about 68°C, accompanied by significant changes in conductivity and dielectric constant. In the terahertz band, the phase change of VO2 can achieve dynamic regulation of the transmission, reflection and absorption properties of electromagnetic waves, making it an ideal dynamic regulation material. Through external stimuli (such as temperature, light or electric field), the phase change of VO2 can achieve rapid response and reversible switching, providing a good technical foundation for the development of dynamic terahertz regulation devices.

[0003] Metasurface is a two-dimensional artificial material designed with subwavelength structural units, which significantly improves the modulation depth and band coverage of the target frequency band. Combining the dynamic phase change characteristics of VO2 with the dual-resonance metasurface design can achieve efficient dynamic regulation function in the terahertz band. On the other hand, the introduction of flexible materials enables the device to adapt to complex bending and deformation environments, thereby improving the practicality and multi-scenario adaptability of the device.

[0004] Despite this, there are still challenges in structural optimization, flexible design and control performance of VO2-based terahertz control devices. For example, how to further improve the resonance performance through structural design, how to achieve stable integration of VO2 phase change materials on flexible substrates, and how to reduce the metallic loss of VO2 are still urgent issues to be solved. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide an actively controlled flexible dual-channel switchable terahertz modulator, which improves the modulation depth and integration by combining VO2 material with a flexible dual-resonance metasurface, and solves the problems existing in the background technology.

[0006] Technical solution: The present invention describes an actively regulated flexible dual-channel switchable terahertz modulator, a flexible substrate layer and a supersurface structure, wherein the flexible substrate layer is composed of a polyimide material; the supersurface structure is composed of vanadium dioxide and a metal material, forming a vertical "I"-shaped periodic pattern, and the insulating state and metallic state phase transition of vanadium dioxide is achieved by controlling the external temperature (20 ℃ ~ 87 ℃).

[0007] Furthermore, the period size is 120 μm × 120 μm.

[0008] Furthermore, the thickness of the metasurface structure is 200 nm; the minimum side length of the "I"-shaped periodic pattern unit is 10 μm.

[0009] Furthermore, in the low-temperature insulating state, the modulator exhibits efficient transmission performance in the 0.1-2 THz frequency band, with a transmittance close to 0 dB.

[0010] Furthermore, when the modulator is in a high-temperature metallic state, vanadium dioxide couples with the metal structure to form a dual-resonance characteristic, generating two resonance valleys with resonance frequencies of 0.604 THz and 1.65 THz, respectively. The 3dB bandwidth of the first resonance is 0.302-0.923 THz, the center frequency is 0.604 THz, and the quality factor is 6.41. The 3dB bandwidth of the second resonance is 1.362-1.947 THz, the center frequency is 1.65 THz, and the quality factor is 14.62, realizing the dual-resonance dynamic switching control function of the terahertz band.

[0011] Furthermore, the modulation depth of the switch at two resonant frequency points is calculated by the following formula: ; Where M is the relative modulation depth, is the maximum transmittance of the device in the dielectric state, is the minimum transmittance of the device in the metallic state.

[0012] Further, for the polyimide dielectric layer, the thickness is 5 μm and the relative dielectric constant is set to 3.5 + 0.0027i.

[0013] The design method of an active control flexible dual-channel switchable terahertz modulator described in the present invention comprises the following steps: (1) Design of flexible substrate and metasurface structure: The flexible substrate is made of polyimide material; the metasurface structure is made of vanadium dioxide and metal materials, forming a vertical “I”-shaped periodic pattern with a periodic size of 120 μm × 120 μm. The minimum side length of the “I”-shaped periodic pattern unit is 10 μm; the metasurface structure thickness is 200 nm; (2) Designing external temperature (20°C to 87°C) to control the insulating and metallic phase transition of vanadium dioxide; (3) The electromagnetic full-wave simulation software was used to simulate and analyze the electromagnetic response characteristics of the flexible switchable dual-resonance terahertz filtering metasurface structure. The boundary conditions in the x and y directions were set as periodic boundaries, while the z direction adopted an open boundary. By setting a plane wave port, the linearly polarized electromagnetic wave propagated along the z-axis and was incident vertically from the +z axis to the top layer of the metasurface structure. The transmittance was monitored using an electric field probe. The simulation frequency range covered 0.1-2 THz, and the time domain transmission line matrix method was used for calculation.

[0014] The application method of the active control flexible dual-channel switchable terahertz modulator described in the present invention is applied to a dynamic switch device in the terahertz band. The dynamic switch device combines the phase change characteristics of vanadium dioxide and the dual-resonance metasurface design, and can achieve low-temperature full-transmission and high-temperature dual-resonance switching functions in the 0.1-2 THz frequency band through temperature control. At low temperatures, the emissivity is close to 0 dB; at high temperatures, it transforms into a metallic state, and through coupling with a metal pattern, two resonance valleys are formed, that is, the resonance frequencies are 0.604 THz and 1.65 THz respectively.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the device of the present invention realizes the functional switching from high-efficiency transmission (low-temperature dielectric state) to dual-resonance switch (high-temperature metal state) by regulating the ambient temperature in the 0.1-2THz frequency band. Among them, the low-temperature insulating state exhibits high transmission characteristics in the range of 0.1-2 THz, while the high-temperature metal state forms two significant resonance valleys, presenting a precise switch control function; utilizing the reversible phase change characteristics of vanadium dioxide, the device can flexibly switch between high transmission and dual-resonance switch functions, enriching the dynamic control means of the terahertz band and providing a new research direction for terahertz metasurface technology; the transmission structure combined with the temperature control design greatly simplifies the control mechanism, and improves the flexibility and ease of use of the device, adapting to a variety of application scenarios; the flexible design and polarization-independent characteristics of the present invention further expand the applicability of the device in complex environments, and can be widely used in terahertz communication, sensing, imaging and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure and dimension marking of the present invention; Figure 2 The flexible dual-channel switchable terahertz switch device of the present invention realizes the effect of dual resonance and full transmission function switching: when vanadium dioxide is in a high-temperature metal state (conductivity is 200000 S / m), its filtering characteristics are as follows Figure 2 As shown in (a), the minimum transmittance is close to -30 dB, and the filtering effect of the device at the resonant frequency is significant and polarization-independent. When vanadium dioxide is in a low-temperature dielectric state (conductivity is 200 S / m), the transmittance is as follows: Figure 2 As shown in (b), the transmittance is almost maintained at 0 dB, and the device has a near-fully transparent performance in the 0.1–2 THz range; Figure 3 The trend of the influence of temperature on the transmittance of the flexible dual-channel switchable terahertz switch device of the present invention; Figure 4The transmittance (dB) of the flexible dual-channel switchable terahertz switch device of the present invention is: when vanadium dioxide is in a high-temperature metallic state, the first resonance obtained has a 3dB bandwidth of 0.302-0.923THz, a bandwidth of 0.621THz, a center frequency of 0.604THz, and a quality factor of 6.41. The second resonance has a 3dB bandwidth of 1.362-1.947THz, a bandwidth of 0.585THz, a center frequency of 1.65THz, and a quality factor of 14.62; Figure 5 The present invention is based on vanadium dioxide (VO 2 ) is a schematic diagram of a flexible dual-channel switchable terahertz switch device system. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0018] Example 1 Based on vanadium dioxide (VO 2 ) Flexible dual-channel switchable terahertz switch device The embodiment of the present invention uses a flexible dual-channel switchable terahertz switch device design based on vanadium dioxide material to propose a transmissive, temperature-controllable dual-resonance filtering terahertz switch device. The device uses the characteristics of vanadium dioxide to achieve multiple functions under different temperature conditions: Under low temperature conditions, vanadium dioxide is in an insulating state and exhibits excellent dielectric properties, allowing the device to achieve efficient transmission in the 0.1-2 THz frequency band with almost no additional attenuation. This feature is suitable for terahertz systems that require high transmittance, such as unobstructed transmission path applications in terahertz imaging and communications.

[0019] Under high temperature conditions, vanadium dioxide undergoes a phase transition and turns into a metallic state. At this time, the device couples with the metal pattern to form two significant resonance valleys, showing a dual-resonance filtering characteristic, which effectively suppresses terahertz waves in a specific frequency band (0.604 THz and 1.65 THz). This function can be used as a tunable band-stop filter to achieve selective switching and suppression of specific frequency signals.

[0020] In the implementation scheme of the present invention, electromagnetic full-wave simulation software is used to simulate and analyze the electromagnetic response characteristics of the flexible switchable dual-resonance terahertz filtering metasurface structure in detail. During the simulation process, the boundary conditions in the x and y directions are set to periodic boundaries, while the z direction uses an open boundary with additional space to simulate the electromagnetic wave propagation environment in infinite space. By setting a plane wave port, the linearly polarized electromagnetic wave propagates along the z-axis direction and is incident vertically from the +z axis to the top layer area of ​​the metasurface structure, and the transmittance is monitored using an electric field probe. The simulation frequency range covers 0.1-2 THz, and the time domain transmission line matrix method is used for calculation.

[0021] The metasurface structure has a high degree of polarization independence, high stability in both TE and TM polarization, and still maintains good active adjustment performance during temperature switching. The designed structure has excellent stability and environmental adaptability, providing broad space for practical engineering applications.

[0022] Example 2 Based on vanadium dioxide (VO 2 ) performance calculation of flexible dual-channel switchable terahertz switch device The present invention proposes a transmissive temperature-controlled flexible switchable band-stop terahertz filter and switch device, whose unit structure adopts a periodic design with a periodic size of 120 μm × 120 μm. The device is based on a double-layer metasurface structure, and its main components include: Bottom dielectric layer: A 5 μm thick polyimide material is used, which has excellent dielectric properties and can provide structural stability and good transmission properties. In addition, polyimide has low loss characteristics in the terahertz band and is an ideal metasurface substrate material.

[0023] Top structural layer: aluminum (Al) and vanadium dioxide (VO 2 ) together, with a thickness of about 200 nm. The top structure adopts a checkerboard design, in which the minimum side length of the checkerboard unit is 10 μm. Through periodic arrangement and design, precise control and flexible response functions of the terahertz band are achieved.

[0024] In the simulation analysis, the embodiment of the present invention uses simulation software to verify and optimize the characteristics of the device. For the polyimide dielectric layer, its relative dielectric constant is set to 3.5 + 0.0027i, taking into account the dielectric properties and loss factor of polyimide.

[0025] In an embodiment of the present invention, when the device is under low temperature conditions, vanadium dioxide (VO 2) remains in an insulating state, showing excellent dielectric properties. In this state, the device has efficient transmission performance in the 0.1–2 THz frequency band, with a transmittance close to full transmittance and almost no additional attenuation loss.

[0026] Under high temperature conditions, the vanadium dioxide material undergoes a phase transition from an insulating state to a metallic state. At this time, the metal pattern in the device structure interacts with the conductive properties of vanadium dioxide to form a coupling effect, producing obvious resonance valleys at specific frequency points (0.604 THz and 1.65 THz), showing significant dual-resonance switching characteristics. This function effectively suppresses the transmission of terahertz waves in a specific frequency band and can be used as a tunable band-stop filter to achieve selective switching and suppression of terahertz signals within the target frequency range.

[0027] By adjusting the ambient temperature, the embodiment of the present invention realizes the switching of the device between the low temperature high transparency and high temperature dual resonant switch states. This temperature control and adjustable characteristic enables the device to have active regulation capability, and can respond quickly according to actual application requirements to achieve dynamic switching and frequency band control in the terahertz band. This function is suitable for dynamic terahertz communication systems, tunable filtering equipment and other terahertz technology fields that require flexible regulation.

[0028] The device structure design in the embodiment of the present invention realizes the polarization-independent response characteristics to terahertz waves. Specifically, for TE linearly polarized and TM linearly polarized terahertz incident waves, the device exhibits consistent electromagnetic response performance and remains stable in both transmission and switching states. This feature enables the device to still work effectively under complex polarization conditions, expands its application range, and is suitable for the terahertz wave control needs of multi-polarized light fields.

[0029] In the device structure design, a polyimide flexible substrate with a thickness of 5 μm is used to provide the device with good flexibility and mechanical stability. This flexible design enables the device to adapt to device surfaces of different shapes, with good bending adaptability and reliability. In addition, the overall structure of the device is lightweight and easy to integrate into portable and wearable devices, and can be widely used in flexible terahertz sensing systems and other multi-scenario terahertz applications.

[0030] In an embodiment of the present invention, based on vanadium dioxide (VO 2The performance parameters of the flexible dual-channel switchable terahertz switch device of the invention are analyzed and calculated in detail through electromagnetic simulation. The simulation results show that the device exhibits obvious dual resonance characteristics in the high-temperature metallic state. Resonance valleys appear at the two frequency points of 0.604 THz and 1.65 THz, and the corresponding quality factors Q values ​​are 6.41 and 14.62, respectively, indicating that the frequency selectivity of the second resonance is higher. It is calculated that the bandwidths of the two resonance valleys are 0.449 THz and 0.386 THz, respectively, showing the device's effective control capability for terahertz waves in a wide frequency band. In addition, the device has extremely high modulation depth at both resonant frequency points, calculated by the following formula: ; Where M is the relative modulation depth, is the maximum transmittance of the device in the dielectric state, is the minimum transmittance of the device in the metallic state.

[0031] At the resonance 1 position, the 3dB bandwidth is 0.302-0.923THz, and within the 3dB bandwidth, its relative modulation depth ranges from 80.7-98.5%. At the resonance 2 position, the 3dB bandwidth is 1.362-1.947THz, and its relative modulation depth ranges from 35.5-94.9%. This shows that the device has a significant effect on suppressing terahertz waves in the high-temperature metallic state, and can achieve dynamic amplitude control in multiple frequency bands.

[0032] In summary, the terahertz device of the present invention exhibits efficient full-transmission characteristics in the low-temperature insulating state, and realizes the dual-resonance switch control function of a specific frequency by forming two resonance valleys in the high-temperature metallic state. The resonant quality factor, band-stop bandwidth and modulation depth of the device all show excellent performance, and are suitable for terahertz communication, spectrum management, tunable filtering and other dynamic control application scenarios.

[0033] Example 3 Based on vanadium dioxide (VO 2 ) flexible switchable dual-resonance terahertz modulation device and its working principle like Figure 5 As shown, this embodiment describes a method based on vanadium dioxide (VO 2 ) flexible switchable dual-resonance terahertz modulation device and its working principle. This system mainly includes a transmitter, a receiver and a VO-based 2 The dual-resonance modulation module of the material, the transmitting end is responsible for signal generation and modulation, and the receiving end is responsible for signal reception and restoration. The dual-resonance modulation module is the core component of the entire system.

[0034] The transmitter includes a local oscillator, a frequency multiplication and amplification link, an optical pumping and temperature control module, and a terahertz antenna. The local oscillator is used to generate a baseband signal and output a stable and low-noise signal source. The frequency multiplication and amplification link multiplies and amplifies the baseband signal to generate a high-frequency signal. The optical pumping and temperature control module triggers the VO through optical pumping or temperature control. 2 The metal-insulator phase transition of the material changes its electromagnetic properties to achieve the function switching of modulation. The terahertz antenna is used to transmit modulated terahertz signals. The working principle of the transmitter is to generate a baseband signal through a local oscillator, and after the high-frequency signal is formed through a frequency multiplication amplification link, the optical pump or temperature control module controls the VO 2 The phase change state of the device. VO 2 The device switches between two different resonance modes through dual resonance characteristics, thereby dynamically modulating the frequency or amplitude of the transmitted signal, which is ultimately transmitted into space by the antenna.

[0035] The receiving end is composed of a terahertz antenna, a low-noise amplifier, a terahertz detector, a low-frequency amplifier, and a digital demodulation module. The terahertz antenna is used to receive the terahertz signal transmitted from the transmitting end. The low-noise amplifier performs low-noise amplification on the received signal to improve the signal-to-noise ratio. The terahertz detector converts the terahertz signal into a low-frequency baseband signal. The low-frequency amplifier amplifies the down-converted baseband signal, and finally demodulates and restores the signal information through the digital demodulation module. The working principle of the receiving end is to capture the terahertz signal through the antenna, down-convert it by the detector after low-noise amplification, and restore the information transmitted by the transmitting end after amplification and demodulation.

[0036] The core device of the system is based on vanadium dioxide (VO 2 The main functions of the flexible dual-resonance modulation device are as follows: First, dynamic frequency switching. 2 The metal-insulator phase transition properties of the material enable it to quickly switch electromagnetic properties under optical pumping or temperature control. Through the dual-resonance structure design, VO 2 The device can quickly switch between the two resonant frequencies, thereby achieving dynamic regulation of the terahertz signal frequency. Second, switch modulation. 2 The device has a high-speed switching modulation function, and its metal-insulator phase change response speed can reach the nanosecond level. The signal can be turned on and off at the transmitting end to achieve the signal modulation function. Third, enhance signal selectivity. The dual-resonance structure makes VO 2 The device has high selectivity for signals in the target frequency band, which can effectively suppress interference signals and improve the system's anti-interference ability. Fourth, flexibility and adaptability. 2 The device is integrated on a flexible substrate, allowing it to maintain stable electromagnetic properties during mechanical deformation (such as bending or stretching), which provides the possibility for its application in flexible electronic devices and wearable devices.

[0037] Through the cooperation of the transmitter and the receiver, combined with VO 2 The dual-resonance modulation device of the material can realize the efficient modulation and transmission of terahertz signals. 2 As the core of the system, the flexible switchable dual-resonance terahertz modulation device can not only realize dynamic frequency switching, but also play the role of high-speed modulation and signal selection, providing flexible and efficient solutions for terahertz communication, imaging and sensing.

Claims

1. An actively controlled flexible dual-channel switchable terahertz modulator, characterized in that: Flexible substrate layer and super surface structure, the flexible substrate layer is made of polyimide material; the super surface structure is composed of vanadium dioxide and metal material, forming a vertical "I"-shaped periodic pattern, and the insulating state and metallic state phase transition of vanadium dioxide is achieved through external temperature control; The external temperature is 20℃~87℃.

2. The active control flexible dual-channel switchable terahertz modulator according to claim 1, characterized in that: The period size is 120 μm × 120 μm.

3. The active control flexible dual-channel switchable terahertz modulator according to claim 1, characterized in that: The thickness of the metasurface structure is 200 nm; the minimum side length of the "I"-shaped periodic pattern unit is 10 μm.

4. The active control flexible dual-channel switchable terahertz modulator according to claim 1, characterized in that: In the low-temperature insulating state, the modulator exhibits efficient transmission performance in the 0.1-2 THz frequency band with a transmittance close to 0 dB.

5. The active control flexible dual-channel switchable terahertz modulator according to claim 1, characterized in that: When the modulator is in the high-temperature metallic state, vanadium dioxide couples with the metal structure to form a dual-resonance characteristic, producing two resonance valleys with resonant frequencies of 0.604 THz and 1.65 THz, respectively. The 3dB bandwidth of the first resonance is 0.302-0.923 THz, the center frequency is 0.604 THz, and the quality factor is 6.

41. The 3dB bandwidth of the second resonance is 1.362-1.947 THz, the center frequency is 1.65 THz, and the quality factor is 14.62, realizing the dual-resonance dynamic switching control function of the terahertz band.

6. The active control flexible dual-channel switchable terahertz modulator according to claim 5, characterized in that: The modulation depth of the switch at the two resonant frequencies is calculated by the following formula: ； Where M is the relative modulation depth, is the maximum transmittance of the device in the dielectric state, is the minimum transmittance of the device in the metallic state.

7. The active control flexible dual-channel switchable terahertz modulator according to claim 1, characterized in that: For the polyimide dielectric layer, the thickness is 5 μm and its relative dielectric constant is set to 3.5 + 0.0027i.

8. A design method for actively regulating a flexible dual-channel switchable terahertz modulator, characterized in that: The following steps are involved: (1) Design of flexible substrate and metasurface structure: The flexible substrate is made of polyimide material; the metasurface structure is made of vanadium dioxide and metal materials, forming a vertical "I"-shaped periodic pattern with a periodic size of 120 μm × 120 μm. The minimum side length of the "I"-shaped periodic pattern unit is 10 μm; the metasurface structure thickness is 200 nm; (2) Design external temperature control to achieve the insulating and metallic phase transition of vanadium dioxide; the temperature is 20 ℃ ~ 87 ℃; (3) The electromagnetic full-wave simulation software was used to simulate and analyze the electromagnetic response characteristics of the flexible switchable dual-resonance terahertz filtering metasurface structure. The boundary conditions in the x and y directions were set as periodic boundaries, while the z direction adopted an open boundary. By setting a plane wave port, the linearly polarized electromagnetic wave propagated along the z-axis and was incident vertically from the +z axis to the top layer of the metasurface structure. The transmittance was monitored using an electric field probe. The simulation frequency range covered 0.1-2 THz, and the time domain transmission line matrix method was used for calculation.

9. An application method for actively regulating a flexible dual-channel switchable terahertz modulator, characterized in that: Dynamic switching devices used in the terahertz band, combined with the phase change characteristics of vanadium dioxide and dual-resonance metasurface design, can achieve low-temperature full-transmission and high-temperature dual-resonance switching functions in the 0.1-2 THz frequency band through temperature control. At low temperatures, the emissivity is close to 0 dB; at high temperatures, it transforms into a metallic state and forms two resonance valleys through coupling with metal patterns, with resonance frequencies of 0.604 THz and 1.65 THz respectively.

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