VO2-based non-reciprocal optical isolation device and preparation method thereof
By setting array holes and multiple interference layers in a VO2 non-reciprocal optical isolation device, and utilizing the phase transition characteristics and photothermal response differences of VO2, an asymmetric response of optical signals in opposite directions is achieved, solving the problem of complex structure of existing devices and enhancing the unidirectional optical transmission capability.
Patent Information
- Application Number
- CN202511801668.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-02
- Publication Date
- 2026-02-10
AI Technical Summary
Existing non-reciprocal optical devices have complex structures, making it difficult to achieve efficient unidirectional transmission of optical signals.
A non-reciprocal optical isolation device based on VO2 is designed. By setting array holes and multi-layer interference layer structure on the metal layer, the phase transition characteristics and photothermal response differences of VO2 are utilized to achieve an asymmetric response of optical signals in opposite directions.
It achieves asymmetric response of optical signals in opposite directions, enhances the unidirectional transmission capability of optical signals, broadens the application range of non-reciprocal optical isolation devices, and provides new optical isolation elements for fields such as integrated optical circuits.
Smart Images
Figure CN121500618A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a non-reciprocal optical isolator and its fabrication method. Background Technology
[0002] In traditional optical systems, the propagation characteristics of light signals are the same in both directions, and this reciprocity limits the realization of certain specific functions. Non-reciprocal optical devices overcome this limitation, allowing light signals to have different response characteristics in opposite directions. These non-reciprocal devices have broad application prospects in fields such as integrated optical circuits and optical computing.
[0003] The realization of non-reciprocal optical properties typically relies on the inherent symmetry of the system or the introduction of external stimuli to disrupt the time-reversal symmetry. Current research focuses on the following approaches: magneto-optical effect, which introduces a magnetic field into the medium and utilizes the Faraday rotation effect or Kerr effect to generate different phase delays and polarization rotations between light signals propagating in opposite directions; acousto-optic modulation, which uses ultrasonic stimulation to achieve dynamic refractive index modulation in the medium material using effects such as Bragg scattering, so that the forward and reverse propagating light signals are affected differently. This method has high flexibility and tunability and is suitable for dynamic control scenarios; topological phase modulation, which uses the design of media with specific geometries, such as helical fiber structures, to generate unidirectional transmission behavior without relying on an external magnetic field; and electro-controlled modulation, which introduces different responses between light signals propagating in opposite directions by applying an asymmetric electric field to cause changes in the refractive index of the structure or differences in the carrier migration characteristics in semiconductor materials.
[0004] Although researchers have made significant progress in achieving efficient non-reciprocal functions through various means such as introducing magneto-optical effects, acousto-optic modulation, and topological phase manipulation, the non-reciprocal optical devices constructed using existing methods still suffer from drawbacks such as structural complexity. Therefore, there is an urgent need to develop a novel type of non-reciprocal optical device. Summary of the Invention
[0005] This invention aims to solve the problem of complex structures in existing optical non-reciprocal devices, and thus provides a non-reciprocal optical isolation device based on VO2 and its fabrication method.
[0006] A non-reciprocal optical isolation device based on VO2, which consists of a metal layer with array holes, a phase transition layer, a first interference layer, a second interference layer and a third interference layer from top to bottom;
[0007] The array holes on the metal layer are square annular holes, with the outer side length of the square annular holes being 0.8μm~1.2μm, the inner side length being 0.6μm~1.0μm, and the vertical distance between the centers of adjacent square annular holes being 1.5μm~2.5μm.
[0008] A method for fabricating a non-reciprocal optical isolator based on VO2, comprising the following steps:
[0009] 1. Using magnetron sputtering, the first interference layer and the third interference layer are formed by sputtering and depositing on both sides of the second interference layer, respectively;
[0010] 2. A phase change layer is obtained by depositing a thin film on the first interference layer using high-energy pulsed magnetron sputtering and then heat-treating it.
[0011] 3. A continuous metal layer is deposited on the surface of the phase change layer using magnetron sputtering, followed by spin coating of photoresist. The photoresist is then cured using laser direct writing or electron beam exposure, and after development, a structure is formed. The continuous metal layer is etched using reactive ion beam etching to form array holes. Finally, the photoresist is removed and cleaned, thus completing the fabrication method of the VO2-based non-reciprocal optical isolation device.
[0012] The beneficial effects of this invention are:
[0013] This invention discloses a non-reciprocal optical isolation device based on VO2 that can achieve optical isolation characteristics under laser irradiation. By adjusting the thickness of the three interference layers and the parameters of the metal layer with arrayed apertures, the laser reverse isolation degree and the isolated laser wavelength can be adjusted. While using multiple films alone to form interference can achieve anti-reflection, this method cannot completely eliminate stray light in the non-isolated band and is unlikely to produce a significant difference in equilibrium temperature due to differences in the thermal diffusion process, making the non-reciprocal characteristic difficult to apply. Compared to the interference layer structure, the combination of the metal layer with arrayed apertures and the interference layer in this invention can achieve complete isolation in the non-isolated band. This reduces the light energy incident from the metal layer with arrayed apertures, decreases the thermal effect on the VO2 layer, and increases the phase transition threshold (laser power) relative to the forward incident direction (metal layer with arrayed apertures), achieving an asymmetric phase transition threshold on both sides, thereby realizing the non-reciprocal characteristic. The thickness of the VO2 structure layer, the bias temperature, and the W doping content can adjust the power density of the incident light suitable for the non-reciprocal optical isolation device.
[0014] This invention utilizes the differences in thermal response and VO2 phase transition states when light is incident from opposite directions, enabling optical signals to exhibit different response characteristics in opposite directions. This achieves efficient unidirectional optical transmission capabilities and provides novel optical isolation components for fields such as integrated optical circuits. The designed VO2-based non-reciprocal optical isolation device broadens the implementation methods of existing non-reciprocal optical isolation devices, providing a new component implementation scheme for the development of novel optical devices.
[0015] This invention relates to a non-reciprocal optical isolation device based on VO2 and its fabrication method. Attached Figure Description
[0016] Figure 1This is a schematic diagram of the structure and working principle of the non-reciprocal optical isolation device based on VO2 of the present invention. 1 is a metal layer with array holes, 2 is a phase transition layer, 3 is a first interference layer, 4 is a second interference layer, and 5 is a third interference layer. Detailed Implementation
[0017] Specific implementation method one: Combining Figure 1 This embodiment describes a non-reciprocal optical isolation device based on VO2, which consists of a metal layer with array holes, a phase transition layer, a first interference layer, a second interference layer and a third interference layer from top to bottom.
[0018] The array holes on the metal layer are square annular holes, with the outer side length of the square annular holes being 0.8μm~1.2μm, the inner side length being 0.6μm~1.0μm, and the vertical distance between the centers of adjacent square annular holes being 1.5μm~2.5μm.
[0019] In this specific embodiment, the thermally induced phase transition behavior of the phase transition layer is the core of the non-reciprocal optical properties. The purpose of the metal layer with array aperture, the first interference layer, the second interference layer and the third interference layer is to achieve a large transmittance switching ratio at a specific wavelength by utilizing the wavelength selection effect and the multilayer interference effect, thereby achieving a large optical reverse isolation.
[0020] In this specific embodiment, the laser creates a difference in photothermal conversion within the VO2 layer when irradiated from the opposite direction. Specifically, when incident from the reverse direction (the third interference layer), the equilibrium temperature that VO2 can reach is lower than the phase transition temperature, while when incident from the forward direction (the metal layer with array holes), the equilibrium temperature that VO2 can reach is higher than the phase transition temperature.
[0021] This specific implementation uses a multi-layer interference effect design and wavelength selection effect to change the laser wavelength of non-reciprocal optical characteristics.
[0022] This specific embodiment can adjust the structure according to the VO2 thickness to achieve a transmission switching ratio at a specific wavelength, thereby achieving non-reciprocal optical reverse isolation.
[0023] This specific embodiment can change the phase transition temperature of VO2 according to the W doping concentration in VO2, thereby changing the laser power density applicable to the non-reciprocal characteristics.
[0024] This specific implementation can change the laser power density applicable to non-reciprocal characteristics by changing the temperature environment in which the device is located.
[0025] Principle: This embodiment features a square annular aperture with a specific structure, which has excellent wavelength selective transmission and can maximize the shielding of interference from non-selective wavelength electromagnetic waves.
[0026] VO2 material undergoes a thermally induced phase transition at 68℃, transforming its crystal structure from a monoclinic phase to a rutile phase, and its infrared properties from high infrared transmittance to high infrared reflectance. Achieving optical non-reciprocity by controlling the optical properties of VO2 before and after the phase transition is a novel approach. A metal layer with arrayed apertures and three interference layers can form multilayer interference within a narrow passband with VO2 in the insulating state, resulting in ultra-high transmittance at the passband wavelength. When VO2 transitions from the insulating state to the metallic state, the multilayer interference effect is completely cut off, and the passband wavelength changes from ultra-high transmittance to ultra-high reflectance, achieving light wave cutoff.
[0027] This embodiment proposes a novel non-reciprocal optical device design based on VO2. Utilizing the reversible insulator-to-metal phase transition property of VO2, a passband is formed in the insulating state and becomes a cutoff state in the metallic state. This enables the device to be in different states when irradiated by laser from both sides due to the different crystal structures of the device, thereby achieving a non-reciprocal response in transmittance.
[0028] This structure exhibits non-reciprocal optical properties under specific laser irradiation. The phase transition behavior of the VO2 layer is the core of the optical non-reciprocity, enabling an asymmetric photothermal response when laser light is incident on the structure from opposite directions, and causing a difference in the VO2 state within the device, which in turn leads to non-reciprocity in optical transmittance. The metal layer with array apertures is key to achieving the narrow passband design. The three interference layers can increase the transmittance of the narrow passband in the insulating state, thereby achieving a greater isolation ratio.
[0029] The beneficial effects of this embodiment are:
[0030] This embodiment of a non-reciprocal optical isolator based on VO2 can achieve optical isolation characteristics under laser irradiation. By adjusting the thickness of the three interference layers and the parameters of the metal layer with arrayed apertures, the laser reverse isolation degree and the isolated laser wavelength can be adjusted. If multiple films are used alone to form interference to achieve anti-reflection of the structure, this method cannot completely realize stray light in the non-isolated band, and it is difficult to generate a large difference in equilibrium temperature caused by the difference in the thermal diffusion process, making it difficult to realize the non-reciprocal feature. Compared with the interference layer structure, the combination of the metal layer with arrayed apertures and the interference layer in this embodiment can achieve complete isolation in the non-isolated band. This reduces the light energy incident from the metal layer with arrayed apertures, reduces the thermal effect on the VO2 layer, and increases the phase transition threshold (laser power) relative to the forward incident (metal layer with arrayed apertures), realizing the asymmetric phase transition threshold on both sides, and thus realizing the non-reciprocal feature. The thickness of the VO2 structure layer, the bias temperature, and the W doping content can adjust the power density of the incident light suitable for the non-reciprocal optical isolator.
[0031] This embodiment utilizes the difference in thermal response and the difference in the VO2 phase transition state when light is incident from opposite directions, enabling optical signals to have different response characteristics in opposite directions, thereby achieving efficient unidirectional optical transmission capability. This provides a novel optical isolation element for fields such as integrated optical circuits. The designed VO2-based non-reciprocal optical isolation device broadens the implementation methods of existing non-reciprocal optical isolation devices, providing a new component implementation scheme for the development of novel optical devices.
[0032] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the thickness of the metal layer with array holes is 50nm~150nm. Everything else is the same as in Specific Implementation Method One.
[0033] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the thickness of the phase change layer is 50nm~120nm. Everything else is the same as Specific Implementation Method One or Two.
[0034] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the thickness of the first interference layer is 0.3μm to 0.8μm; the thickness of the second interference layer is 350μm to 650μm; and the thickness of the third interference layer is 0.3μm to 0.8μm. Everything else is the same as in Specific Implementation Methods One to Three.
[0035] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the metal layer with arrayed holes is made of Al. Otherwise, it is the same as Specific Implementation Methods One to Four.
[0036] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the phase transition layer is made of W-doped VO2, and W accounts for 0% to 2.5% of the total number of W and V atoms. Everything else is the same as in Specific Implementation Methods One to Five.
[0037] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the material of the first interference layer is HfO2; the material of the second interference layer is Si; and the material of the third interference layer is HfO2. Everything else is the same as in Specific Implementation Methods One to Six.
[0038] Specific Implementation Method Eight: This implementation method provides a method for fabricating a non-reciprocal optical isolation device based on VO2, which is carried out according to the following steps:
[0039] 1. Using magnetron sputtering, the first interference layer and the third interference layer are formed by sputtering and depositing on both sides of the second interference layer, respectively;
[0040] 2. A phase change layer is obtained by depositing a thin film on the first interference layer using high-energy pulsed magnetron sputtering and then heat-treating it.
[0041] 3. A continuous metal layer is deposited on the surface of the phase change layer using magnetron sputtering, followed by spin coating of photoresist. The photoresist is then cured using laser direct writing or electron beam exposure, and after development, a structure is formed. The continuous metal layer is etched using reactive ion beam etching to form array holes. Finally, the photoresist is removed and cleaned, thus completing the fabrication method of the VO2-based non-reciprocal optical isolation device.
[0042] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Eight in that: Step One is specifically carried out according to the following steps: Using DC magnetron sputtering, under the conditions of DC power supply power of 150W~250W, oxygen flow rate of 2sccm~6sccm, argon flow rate of 70sccm~90sccm, pressure of 0.3Pa~0.8Pa and substrate temperature of 150℃~250℃, a first interference layer and a third interference layer are sputtered and deposited on both sides of the second interference layer respectively;
[0043] Step two is specifically carried out as follows: Using high-energy pulsed magnetron sputtering, a thin film is deposited on the first interference layer under the following conditions: power supply of 140W~180W, pulse duty cycle of 0.5%~1.5%, oxygen flow rate of 1.2sccm~2sccm, argon flow rate of 70sccm~90sccm, pressure of 0.7Pa~1.0Pa, and substrate temperature of 350℃~450℃. Then, it is heat-treated for 2h~4h under an argon atmosphere and at a temperature of 350℃~450℃. Other procedures are the same as in specific embodiment eight.
[0044] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Eight or Nine in that step three is specifically performed according to the following steps:
[0045] ① A continuous metal layer is deposited on the surface of the phase change layer using DC magnetron sputtering under the conditions of DC power supply power of 80W~120W, argon flow rate of 40sccm~60sccm, pressure of 0.5Pa~1.0Pa and substrate temperature of 80℃~120℃.
[0046] ② Using a spin coater, at a speed of 3500 rpm to 4500 rpm, PMMA A4 photoresist is spin-coated onto a continuous metal layer surface for 50 s to 70 s, and then baked at a temperature of 150 ℃ to 200 ℃ for 80 s to 120 s to obtain a photoresist with a thickness of 150 nm to 200 nm.
[0047] ③ At an electron beam accelerating voltage of 40keV~60keV and an exposure dose of 250μC / cm 2 ~350μC / cm 2Under these conditions, the photoresist is exposed according to the pattern, and after exposure, it is developed for 100s~140s to obtain the photomask.
[0048] ④ Using a reactive ion beam with Cl2 gas as the etching gas, under the conditions of RF power of 40W~60W, ICP power of 300W~340W, Cl2 gas flow rate of 5sccm~15sccm and pressure of 5mTorr~10mTorr, a continuous metal layer is etched for 10s~30s to obtain an array of holes.
[0049] ⑤ Place in a desmearing solution and heat at 130℃~170℃ for 5min~15min. Then wash in acetone solution and dry with nitrogen. Other steps are the same as in specific implementation method eight or nine.
[0050] The beneficial effects of the present invention are verified using the following embodiments:
[0051] Example 1:
[0052] A non-reciprocal optical isolation device based on VO2, which consists of a metal layer with array holes, a phase transition layer, a first interference layer, a second interference layer and a third interference layer from top to bottom;
[0053] The array holes on the metal layer are square annular holes, with the outer side length of the square annular holes being 1μm, the inner side length being 0.8μm, and the vertical distance between the centers of adjacent square annular holes being 2μm.
[0054] The thickness of the metal layer with array holes is 100 nm.
[0055] The phase change layer has a thickness of 70 nm.
[0056] The thickness of the first interference layer is 0.5 μm; the thickness of the second interference layer is 350 μm; and the thickness of the third interference layer is 0.5 μm.
[0057] The metal layer with arrayed holes is made of Al.
[0058] The phase transition layer is made of W-doped VO2, and W accounts for 2% of the total number of W and V atoms.
[0059] The first interference layer is made of HfO2; the second interference layer is made of Si; and the third interference layer is made of HfO2.
[0060] A method for fabricating a non-reciprocal optical isolator based on VO2, comprising the following steps:
[0061] 1. Using magnetron sputtering, the first interference layer and the third interference layer are formed by sputtering and depositing on both sides of the second interference layer, respectively;
[0062] 2. A phase change layer is obtained by reacting and depositing a thin film on the first interference layer using high-energy pulsed magnetron sputtering and then heat-treating it.
[0063] 3. A metal layer is deposited on the surface of the phase change layer using magnetron sputtering, followed by spin coating of photoresist. The photoresist is then cured using laser direct writing or electron beam exposure, and after development, a structure is formed. Square annular holes are formed on the surface of the metal layer using reactive ion beam etching. Finally, the photoresist is removed and the device is cleaned. This completes the fabrication method of the non-reciprocal optical isolation device based on VO2.
[0064] Step one is specifically carried out in the following steps: using DC magnetron sputtering, under the conditions of DC power of 200W, oxygen flow rate of 4sccm, argon flow rate of 80sccm, pressure of 0.5Pa and substrate temperature of 200℃, the first interference layer and the third interference layer are sputtered and deposited on both sides of the second interference layer respectively.
[0065] Step two is carried out in the following steps: using high-energy pulsed magnetron sputtering, a thin film is deposited on the first interference layer under the conditions of power supply of 160W, pulse duty cycle of 1%, oxygen flow rate of 1.6sccm, argon flow rate of 80sccm, pressure of 0.9Pa and substrate temperature of 400℃, and then heat-treated for 3h under argon atmosphere and temperature of 400℃.
[0066] Step three is carried out in the following steps:
[0067] ① A continuous metal layer was deposited on the surface of the phase change layer using DC magnetron sputtering under the conditions of DC power supply power of 100W, argon flow rate of 50sccm, pressure of 0.8Pa and substrate temperature of 100℃.
[0068] ② Using a spin coater, PMMA A4 photoresist was spin-coated onto a continuous metal layer surface for 60 seconds at a speed of 4000 rpm, and then baked at a temperature of 180℃ for 100 seconds to obtain a photoresist with a thickness of 175 nm.
[0069] ③ At an electron beam acceleration voltage of 50 keV and an exposure dose of 300 μC / cm 2 Under these conditions, the photoresist is exposed according to the pattern, and after exposure, it is developed for 120 seconds to obtain the photomask.
[0070] ④ Using a reactive ion beam with Cl2 gas as the etching gas, under the conditions of RF power of 50W, ICP power of 320W, Cl2 gas flow rate of 10sccm and pressure of 5mTorr, a continuous metal layer was etched for 20s to obtain an array of holes.
[0071] ⑤ Place it in a degumming solution and heat it at 150℃ for 10 minutes. Then wash it in acetone solution and dry it with nitrogen gas.
[0072] Example 2: This example differs from Example 1 in that the outer side length of the square annular hole is 1.2 μm, and the inner side length is 1 μm. Everything else is the same as in Example 1.
[0073] Example 3: This example differs from Example 1 in that the thickness of the first interference layer is 0.45 μm, and the thickness of the third interference layer is 0.45 μm. Everything else is the same as in Example 1.
[0074] Example 4: This example differs from Example 1 in that the thickness of the phase change layer is 120 nm. Everything else is the same as in Example 1.
[0075] Example 5: This example differs from Example 1 in that W accounts for 1.5% of the total number of atoms of W and V. Everything else is the same as in Example 1.
[0076] Example 6: This example differs from Example 1 in that W accounts for 1% of the total number of atoms of W and V. Everything else is the same as in Example 1.
[0077] Example 7: This example differs from Example 1 in that W accounts for 0.5% of the total number of atoms of W and V. Everything else is the same as in Example 1.
[0078] Example 8: This example differs from Example 1 in that W accounts for 0% of the total number of atoms of W and V. Everything else is the same as in Example 1.
[0079] Example 1: In a constant temperature environment of 25°C, with a wavelength of 3.5μm and a power of 6.5kW / cm². 2 After the pulsed laser irradiation reaches the point where the transmittance is stable, the transmittance is 0.05 when incident in the forward direction (metal layer with array holes) and 0.65 when incident in the reverse direction (third interference layer). At this point, the optical reverse isolation for electromagnetic waves with a wavelength of 3.5μm is 13:1.
[0080] Example 2: In a constant temperature environment of 25°C, with a wavelength of 4.9μm and a power of 8.5kW / cm². 2After the pulsed laser irradiation reaches the point where the transmittance is stable, the transmittance is 0.10 when incident in the forward direction (metal layer with array holes) and 0.58 when incident in the reverse direction (third interference layer). At this point, the optical reverse isolation for electromagnetic waves with a wavelength of 4.9μm is 6:1.
[0081] Example 3: In a constant temperature environment of 25°C, with a wavelength of 3.2μm and a power of 6.8kW / cm². 2 After the pulsed laser irradiation reaches the point where the transmittance is stable, the transmittance is 0.05 when incident in the forward direction (metal layer with array holes) and 0.60 when incident in the reverse direction (third interference layer). At this point, the optical reverse isolation for electromagnetic waves with a wavelength of 3.2μm is 12:1.
[0082] Example 4: In a constant temperature environment of 25°C, with a wavelength of 3.5μm and a power of 5.8kW / cm². 2 After the pulsed laser irradiation reaches the point where the transmittance is stable, the transmittance is 0.05 when incident in the forward direction (metal layer with array holes) and 0.55 when incident in the reverse direction (third interference layer). At this point, the optical reverse isolation for electromagnetic waves with a wavelength of 3.5μm is 11:1.
[0083] Example 5: In a constant temperature environment of 35°C, with a wavelength of 3.5μm and a power of 6kW / cm². 2 After the pulsed laser irradiation reaches the point where the transmittance is stable, the transmittance is 0.05 when incident in the forward direction (metal layer with array holes) and 0.57 when incident in the reverse direction (third interference layer). At this point, the optical reverse isolation for electromagnetic waves with a wavelength of 3.5μm is 12:1.
[0084] Example 6: In a constant temperature environment of 43°C, with a wavelength of 3.5μm and a power of 5.5kW / cm². 2 After the pulsed laser irradiation reaches the point where the transmittance is stable, the transmittance is 0.05 when incident in the forward direction (metal layer with array holes) and 0.45 when incident in the reverse direction (third interference layer). At this point, the optical reverse isolation for electromagnetic waves with a wavelength of 3.5μm is 9:1.
[0085] Example 7: In a constant temperature environment of 50°C, with a wavelength of 3.5μm and a power of 4.5kW / cm². 2 After the pulsed laser irradiation reaches the point where the transmittance is stable, the transmittance is 0.05 when incident in the forward direction (metal layer with array holes) and 0.42 when incident in the reverse direction (third interference layer). At this point, the optical reverse isolation for electromagnetic waves with a wavelength of 3.5μm is 8:1.
[0086] Example 8: In a constant temperature environment of 55°C, with a wavelength of 3.5μm and a power of 3.2kW / cm². 2After the pulsed laser irradiation reaches the point where the transmittance is stable, the transmittance is 0.05 when incident in the forward direction (metal layer with array holes) and 0.62 when incident in the reverse direction (third interference layer). At this point, the optical reverse isolation for electromagnetic waves with a wavelength of 3.5μm is 12:1.
Claims
1. A non-reciprocal optical isolation device based on VO2, characterized in that... It consists of, from top to bottom, a metal layer with arrayed holes, a phase transition layer, a first interference layer, a second interference layer, and a third interference layer; The array holes on the metal layer are square annular holes, with the outer side length of the square annular holes being 0.8μm~1.2μm, the inner side length being 0.6μm~1.0μm, and the vertical distance between the centers of adjacent square annular holes being 1.5μm~2.5μm.
2. The non-reciprocal optical isolation device based on VO2 according to claim 1, characterized in that... The thickness of the metal layer with array holes is 50nm~150nm.
3. The non-reciprocal optical isolation device based on VO2 according to claim 1, characterized in that... The thickness of the phase change layer is 50nm~120nm.
4. A non-reciprocal optical isolation device based on VO2 according to claim 1, characterized in that... The thickness of the first interference layer is 0.3 μm to 0.8 μm; the thickness of the second interference layer is 350 μm to 650 μm; and the thickness of the third interference layer is 0.3 μm to 0.8 μm.
5. A non-reciprocal optical isolation device based on VO2 according to claim 1, characterized in that... The metal layer with arrayed holes is made of Al.
6. A non-reciprocal optical isolation device based on VO2 according to claim 1, characterized in that... The phase transition layer is made of W-doped VO2, and W accounts for 0% to 2.5% of the total number of W and V atoms.
7. A non-reciprocal optical isolation device based on VO2 according to claim 1, characterized in that... The first interference layer is made of HfO2; the second interference layer is made of Si; and the third interference layer is made of HfO2.
8. The method for fabricating a non-reciprocal optically isolated device based on VO2 as described in claim 1, characterized in that... It is done in the following steps:
1. Using magnetron sputtering, the first interference layer and the third interference layer are formed by sputtering and depositing on both sides of the second interference layer, respectively; 2. A phase change layer is obtained by depositing a thin film on the first interference layer using high-energy pulsed magnetron sputtering and then heat-treating it.
3. A continuous metal layer is deposited on the surface of the phase change layer using magnetron sputtering, followed by spin coating of photoresist. The photoresist is then cured using laser direct writing or electron beam exposure, and after development, a structure is formed. The continuous metal layer is etched using reactive ion beam etching to form array holes. Finally, the photoresist is removed and cleaned, thus completing the fabrication method of the VO2-based non-reciprocal optical isolation device.
9. The method for fabricating a non-reciprocal optically isolated device based on VO2 according to claim 8, characterized in that... Step one is specifically carried out in the following steps: using DC magnetron sputtering, under the conditions of DC power supply power of 150W~250W, oxygen flow rate of 2sccm~6sccm, argon flow rate of 70sccm~90sccm, pressure of 0.3Pa~0.8Pa and substrate temperature of 150℃~250℃, the first interference layer and the third interference layer are sputtered and deposited on both sides of the second interference layer respectively; Step two is specifically carried out as follows: using high-energy pulsed magnetron sputtering, a thin film is deposited on the first interference layer under the conditions of power supply of 140W~180W, pulse duty cycle of 0.5%~1.5%, oxygen flow rate of 1.2sccm~2sccm, argon flow rate of 70sccm~90sccm, pressure of 0.7Pa~1.0Pa and substrate temperature of 350℃~450℃. Then, it is heat-treated for 2h~4h under argon atmosphere and temperature of 350℃~450℃.
10. The method for fabricating a non-reciprocal optically isolated device based on VO2 according to claim 8, characterized in that... Step three is carried out in the following steps: ① A continuous metal layer is deposited on the surface of the phase change layer using DC magnetron sputtering under the conditions of DC power supply power of 80W~120W, argon flow rate of 40sccm~60sccm, pressure of 0.5Pa~1.0Pa and substrate temperature of 80℃~120℃. ② Using a spin coater, at a speed of 3500 rpm to 4500 rpm, PMMA A4 photoresist is spin-coated onto a continuous metal layer surface for 50 s to 70 s, and then baked at a temperature of 150 ℃ to 200 ℃ for 80 s to 120 s to obtain a photoresist with a thickness of 150 nm to 200 nm. ③ At an electron beam accelerating voltage of 40keV~60keV and an exposure dose of 250μC / cm 2 ~350μC / cm 2 Under these conditions, the photoresist is exposed according to the pattern, and after exposure, it is developed for 100s~140s to obtain the photomask. ④ Using a reactive ion beam with Cl2 gas as the etching gas, under the conditions of RF power of 40W~60W, ICP power of 300W~340W, Cl2 gas flow rate of 5sccm~15sccm and pressure of 5mTorr~10mTorr, a continuous metal layer is etched for 10s~30s to obtain an array of holes. ⑤ Place it in a degumming solution and heat it at a temperature of 130℃~170℃ for 5min~15min. Then wash it in acetone solution and blow it dry with nitrogen.