High-steady-state polarization regulator based on semiconductor metamaterial

Abstract

The invention discloses a high-steady-state polarization regulator based on a semiconductor metamaterial, which consists of a cuboid unit and a medium connector and is used for realizing efficient and stable conversion among various polarization states of electromagnetic waves. Polarization state conversion from a linear polarization state to a linear polarization state, from the linear polarization state to a circular polarization state, from the circular polarization state to the circular polarization state and from the circular polarization state to the linear polarization state is covered. Regulation and control excitation adopted by the polarization regulator is regulation and control electromagnetic waves, the power of the regulation and control electromagnetic waves is regulated to change the carrier concentration and distribution of the cuboid units, and switching between the polarization states is achieved. The polarization modulator is simple in structure, easy to integrate, stable in performance, efficient and suitable for the fields of optical communication, polarization imaging, precision measurement and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz devices, and in particular to a highly stable polarization regulator based on semiconductor metamaterials. Background Art

[0002] Metamaterials are man-made composite materials with special electromagnetic properties in the field of modern optics. Their properties depend on their unique structural units and periodic arrangements. They are widely used in the field of terahertz wave plates and have promoted the design and development of optical devices related to polarization control. Polarizers based on metamaterials play a key role in polarization control technology. Polarization control technology focuses on precisely controlling the polarization state of light waves, including core operations such as polarization state conversion, which can achieve specific propagation characteristics of light waves in different media. By designing the polarizer structure, the polarization, amplitude, phase and propagation mode of the incident electromagnetic wave can be controlled. In optical applications, polarization characteristics are crucial, but traditional polarizers have fixed polarization states and are difficult to meet the diverse needs of modern optical systems. With the development of science and technology, the demand for polarization state switching in fields such as optical communications, imaging and display has become increasingly urgent. Although electrical and optical control has broken the limitations of traditional polarization control, the thermal effect of metamaterials and their sensitivity to external temperature cause changes in the optical properties of metamaterials, reducing the stability and accuracy of polarizers and affecting their performance.

[0003] In contrast, the highly stable polarization regulator based on semiconductor metamaterials of this patent provides an alternative solution. Its core advantage is that the switching of various polarization functions of the polarization regulator is achieved by adjusting the power of the electromagnetic wave, avoiding the influence of temperature factors on the regulation, and improving the stability and accuracy of the polarization regulator. In addition, this patent uses a dielectric connector with low dielectric constant and low thermal conductivity to reduce the mutual interference between the near field and the far field caused by the internal electromagnetic resonance of adjacent metamaterial units (rectangular units), further greatly improving the stability and accuracy of the polarization regulator; secondly, due to the low thermal conductivity of the dielectric connector, the temperature of the polarization regulator remains stable and is almost unaffected by external temperature factors, thereby greatly improving its application scenarios. It shows broad application potential in the fields of optical communication, imaging and display. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a highly stable polarization regulator based on semiconductor metamaterials, which has the characteristics of high performance, high stability and high compactness, and can realize a variety of electromagnetic wave polarization conversion functions under the excitation of regulated electromagnetic waves.

[0005] This patent combines the electromagnetic resonance effect of the subwavelength structural unit (rectangle), the polarization oscillation effect of free carriers and the electromagnetic coupling mechanism to design and realize an ultra-compact, high-performance, and high-stability polarization-adjustable metamaterial device. By regulating the electromagnetic wave excitation, efficient and stable conversion of electromagnetic waves in various polarization states can be achieved, covering dynamic switching from linear polarization state to linear polarization state, linear polarization state to circular polarization state, circular polarization state to circular polarization state, and circular polarization state to linear polarization state. The specific technical solutions of the present invention are as follows:

[0006] A highly stable polarization regulator based on semiconductor metamaterials is composed of sub-wavelength periodic units, including cuboid units and dielectric connectors. The cuboid units are embedded in the dielectric connectors.

[0007] Furthermore, the rectangular unit structure is a doped semiconductor. The height of the rectangular unit is 0.70 to 1.20 times the wavelength of the working electromagnetic wave; the long side of the rectangular unit is in the x-axis direction, the short side is in the y-axis direction, the ratio of the length of the long side and the width of the short side of the rectangular unit to the wavelength of the working electromagnetic wave is in the range of 0.16 to 0.28 and 0.09 to 0.16 respectively, and the length and width are not equal.

[0008] Furthermore, the doped semiconductor is preferably an N-type doped semiconductor.

[0009] Preferably, the N-type doped semiconductor may be silicon or gallium arsenide.

[0010] Preferably, the free carrier concentration of the doped semiconductor is 10 18 ~10 19 cm -3 .

[0011] Furthermore, the dielectric connector has a relative dielectric constant of 1 to 1.2 and a thermal conductivity of 0.014 to 0.020 W / (m·K), and is preferably a silica aerogel.

[0012] Furthermore, the working electromagnetic wave is incident along the height direction (z-axis direction) of the rectangular unit, that is, vertically incident on the polarization regulator. The u-axis direction is the polarization direction of the working electromagnetic wave, and the angle with the x-axis is α. The v-axis is perpendicular to the u-axis and forms an angle α with the y-axis.

[0013] Furthermore, changing the length, width and height of each cuboid unit will affect the transmission coefficient modulus of the cuboid unit in the u-axis and v-axis directions. u | and |t v | and its phase difference Δδ.

[0014] According to ellipticity (The EP ranges from -1 to 1), and the polarization state of the working electromagnetic wave is determined. When EP = 0, it represents linearly polarized light. At this time, the amplitudes in two orthogonal directions are equal, but the phase difference is 0 or 180°; when EP = 1, it represents right-handed circularly polarized light. At this time, the amplitudes in two orthogonal directions are equal, and the phase difference is 90°; when EP = -1, it represents left-handed circularly polarized light. At this time, the amplitudes in two orthogonal directions are equal, and the phase difference is -90°; when -1 < EP < 0, it represents left-handed elliptically polarized light. At this time, the amplitudes in two orthogonal directions are not equal, and the phase difference is between -90° and 0°; when 0 < EP < 1, it represents right-handed elliptically polarized light. At this time, the amplitudes in two orthogonal directions are not equal, and the phase difference is between 0° and 90°.

[0015] Furthermore, the electromagnetic wave is regulated to be incident on the cuboid unit unidirectionally or bidirectionally along the height direction parallel to the cuboid unit at a specific wavelength and power. Due to the polarization oscillation effect of free carriers, the temperature of the cuboid-doped semiconductor increases. When the temperature rises to the preset temperature, the loading of the regulated electromagnetic wave is stopped or the power of the regulated electromagnetic wave is reduced. Further, the working electromagnetic wave is incident on the polarization regulator along the height direction (z-axis direction) of the cuboid unit. Due to the temperature change, the carrier concentration and its distribution inside the cuboid-doped semiconductor unit change, which changes the electromagnetic resonance behavior of free carriers inside the cuboid unit (sub-wavelength structure), resulting in changes in the effective relative permittivities of the cuboid unit in the u-axis and v-axis directions, and then bringing about changes in the modulus of the transmission coefficients of the transmitted electromagnetic wave in the u-axis and v-axis directions and the phase difference between the two (i.e., ellipticity), ultimately realizing the polarization conversion function. The free carrier concentration at temperature T where N 0 is the carrier concentration at the reference temperature, E g is the energy band gap, and K is the Boltzmann constant.

[0016] By using a dielectric connector with a low dielectric constant and low thermal conductivity, the mutual interference between the near field and the far field caused by the electromagnetic resonance inside adjacent metamaterial units (cuboid units) is reduced. Due to the low thermal conductivity of the dielectric connector, the temperature of the polarization regulator remains stable, and the polarization regulator is hardly affected by external temperature factors.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] (1) The highly stable polarization controller based on semiconductor metamaterials provided by the present invention can adjust the power of electromagnetic waves to achieve different polarization function switching, which makes the polarization controller have a wider application potential in a variety of optical systems. (2) Compared with traditional polarizers, the polarization controller of the present invention has a compact structure and is easy to integrate with existing semiconductor electronic devices, which is conducive to the miniaturization and integration of optical systems. (3) It can be processed using mature semiconductor processes to reduce manufacturing costs. At the same time, the electromagnetic properties of semiconductors can be easily regulated by external electromagnetic wave excitation. (4) The dielectric connector can maintain its function within a wide temperature range, which enhances the stability and reliability of the polarization controller under different environmental conditions. (5) Due to the above advantages, the polarization controller of the present invention has broad application prospects in the fields of terahertz communication, spectral detection, sensing technology, etc., and helps to promote the development and innovation of related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to show the technical details of the embodiments of the invention, the drawings used in the embodiments are briefly introduced. Obviously, they only represent some embodiments of the present invention. For those skilled in the art, other possible drawing forms can be derived from these drawings.

[0020] Figure 1 It is a structural schematic diagram of the polarization regulator.

[0021] Figure 2 This is a schematic diagram of the periodic unit of the polarization regulator in the xoy plane.

[0022] Figure 3 is the transmission coefficient modulus when u-polarized and v-polarized electromagnetic waves are incident on this polarization controller (|t u | and |t v |) spectrum and transmitted wave ellipticity spectrum.

[0023] Figure 4 (a), (b), and (c) show the temperature variation trend of the ellipticity of the transmitted electromagnetic wave when linearly polarized electromagnetic waves with wavelengths of 0.26 mm, 0.3 mm, and 0.37 mm are incident on the polarization regulator.

[0024] Figure 5 is the transmission coefficient modulus (|t u | and |t v |) spectrum and transmitted wave ellipticity spectrum.

[0025] Figure 6 (a), (b), and (c) show the temperature variation trend of the ellipticity of the transmitted electromagnetic wave when right-handed circularly polarized electromagnetic waves with wavelengths of 0.26 mm, 0.3 mm, and 0.37 mm are incident on the polarization regulator.

[0026] In the figure: 1 is a rectangular unit, 2 is a dielectric connection, 3 is a control electromagnetic wave, 4 is a working electromagnetic wave, α is the angle between the u axis and the x axis, |t u | is the transmission coefficient norm in the u-axis direction, |t v | is the transmission coefficient norm in the v-axis direction, and EP is the ellipticity. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the examples in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The present invention aims to provide a high-stable-state polarization regulator based on semiconductor metamaterials to achieve a related technical solution for better high-stable-state polarization regulation.

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The present invention is a highly stable polarization regulator based on semiconductor metamaterials, comprising at least one sub-wavelength periodic unit. The sub-wavelength periodic unit comprises a rectangular unit and a dielectric connector. The rectangular unit is embedded inside the dielectric connector, and the working electromagnetic wave is incident along the height direction (z-axis direction) of the rectangular unit. The height of the rectangular unit is 0.70 to 1.20 times the wavelength of the working electromagnetic wave; the ratio of the length of the rectangular unit in the x-axis direction and the width in the y-axis direction to the wavelength of the working electromagnetic wave is in the range of 0.16 to 0.28 and 0.09 to 0.16, respectively, and the length and width are not equal. The rectangular unit is composed of an N-type or P-type doped semiconductor, preferably an N-type doped semiconductor, which can be a semiconductor such as silicon or gallium arsenide. The N-type doped semiconductor preferably has a free carrier concentration of 10 18 ~10 19 cm -3 The dielectric constant of the dielectric connection material is 1 to 1.2, and the thermal conductivity is 0.014 to 0.020 W / (m·K), and silica aerogel is preferred.

[0031] Furthermore, the regulating electromagnetic wave (12.2cm~12.6cm) is incident on the rectangular unit unidirectionally or bidirectionally along the height direction parallel to the rectangular unit with a specific power. Due to the polarization oscillation effect of free carriers, the temperature of the rectangular doped semiconductor increases. When the temperature rises to the preset temperature, the loading of the regulating electromagnetic wave is stopped or the power of the regulating electromagnetic wave is reduced. Further, the working electromagnetic wave is incident on the polarization regulator along the height direction (z-axis direction) of the rectangular unit. Due to the temperature change, the carrier concentration and its distribution inside the rectangular doped semiconductor unit change, which changes the electromagnetic resonance behavior of the free carriers inside the rectangular unit (subwavelength structure), resulting in the change of the effective relative dielectric constant of the rectangular unit in the u-axis and v-axis directions, which in turn brings about the change of the transmission coefficient modulus of the transmitted electromagnetic wave in the u-axis and v-axis directions and the phase difference (i.e., ellipticity) between the two, and finally realizes the polarization conversion function. The use of dielectric connectors with low dielectric constant and low thermal conductivity reduces the mutual interference between the near field and the far field caused by the internal electromagnetic resonance of adjacent metamaterial units (rectangular units). Due to the low thermal conductivity of the dielectric connector, the temperature of the polarization controller remains stable and the polarization controller is almost unaffected by external temperature factors.

[0032] The specific parameters of each embodiment are as follows:

[0033] Example 1

[0034] (1) Experimental methods

[0035] like Figure 1 As shown, the height H of the subwavelength periodic unit is 300um. The length of the rectangular unit is 70um and the width is 40um. The rectangular unit is a silicon-doped semiconductor, the doping type is N-type, and the free carrier concentration of the silicon-doped semiconductor is 1×10 18 cm -3 The angle α between the u-axis and the x-axis is 45°. Figure 2 As shown, the period of the rectangular unit is 100um. The material of the dielectric connector is silica aerogel.

[0036] The electromagnetic wave is regulated to be incident bidirectionally from the height direction parallel to the rectangular unit, with a wavelength of 12.24 cm and a power of 1200 W. The temperature is regulated to rise to the specified temperature. When the u-polarized and v-polarized electromagnetic waves are incident on the polarization regulator, the transmission coefficients of the u-polarized and v-polarized electromagnetic waves are modul|t u | and |t v | and the changing trend of ellipticity EP with different wavelengths, such as Figure 3 shown.

[0037] (2) Experimental results

[0038] like Figure 3As shown in the figure, at the working wavelength of 0.3mm, that is, for linearly polarized incident light, there is only transmission in the v-axis direction, and the ellipticity EP is 0, which means that the u-linearly polarized incident light is completely converted into the v-linearly polarized outgoing light; at the working wavelength of 0.26mm, the transmission coefficient modulus in the u-axis direction and the v-axis direction is equal (|t u |=|t v |), and the ellipticity EP is 1, that is, the u-linear polarized incident light is converted into right-handed circularly polarized outgoing light; at the working wavelength of 0.37mm, the transmission coefficient modulus in the u-axis direction and the v-axis direction is equal (|t u |=|t v |), and the ellipticity is -1, that is, the u-linearly polarized incident light is converted into left-handed circularly polarized outgoing light.

[0039] like Figure 4 As shown in the figure, at different working wavelengths, the ellipticity EP shows a certain change trend with the change of temperature. Within the normal working temperature range, it can maintain a stable polarization state conversion function, and will not experience a sharp deterioration in performance or loss of function due to slight temperature fluctuations.

[0040] Specifically, at a working wavelength of 0.3 mm, the ellipticity EP is 0, which means that all linearly polarized incident light is converted into linearly polarized outgoing light; in the temperature range of 100K to 550K, the ellipticity EP changes steadily, and the polarization state conversion efficiency remains relatively stable; at a working wavelength of 0.26 mm, the transmission coefficient modulus in the u-axis and v-axis directions is equal (|t u |=|t v |), and the ellipticity EP is 1, that is, the u-linear polarized incident light is converted into right-handed circularly polarized outgoing light. In the temperature range of 100K to 550K, the ellipticity EP changes steadily, and the polarization state conversion efficiency remains relatively stable. When the control temperature is raised to 660K, the ellipticity EP is 0, that is, the linearly polarized incident light is completely converted into linearly polarized outgoing light, realizing the conversion of different polarizations; at the working wavelength of 0.37mm, the transmission coefficient modulus in the u-axis and v-axis directions is equal (|t u |=|t v |), and the ellipticity is -1, that is, the linearly polarized incident light is converted into left-handed circularly polarized outgoing light. In the temperature range of 100K to 550K, the ellipticity EP changes steadily, and the polarization state conversion efficiency remains relatively stable. When the control temperature is raised to 660K, the ellipticity EP is 0, that is, the linearly polarized incident light is completely converted into linearly polarized outgoing light.

[0041] In summary, at an operating wavelength of 0.3mm, the linear polarization state of the present invention rotates 90° to achieve a change in the direction of rotation of the linear polarization state. At operating wavelengths of 0.26mm and 0.37mm, the present invention achieves the function of converting a linear polarization state to a circular polarization state. Within a larger temperature range, the polarization regulator can maintain a stable polarization state conversion function, and will not experience a sharp deterioration in performance or loss of function due to slight temperature fluctuations. At the same time, the temperature can be precisely controlled by controlling the power of the electromagnetic wave, and the polarization function of the polarization regulator can be further dynamically adjusted.

[0042] Example 2 (Right-handed circularly polarized incident light)

[0043] (1) Experimental methods

[0044] like Figure 1 As shown, the height H of the subwavelength periodic unit is 300um. The length of the rectangular unit is 70um and the width is 40um. The rectangular unit is a silicon-doped semiconductor, the doping type is N-type, and the free carrier concentration of the silicon-doped semiconductor is 1×10 18 cm -3 The angle α between the u-axis and the x-axis is 45°. Figure 2 As shown, the period of the rectangular unit is 100um. The material of the dielectric connector is silica aerogel.

[0045] The electromagnetic wave is regulated to be incident bidirectionally from the height direction parallel to the rectangular unit, with a wavelength of 12.24 cm and a power of 1200 W. The temperature is regulated to rise to the specified temperature. When the right-handed circularly polarized wave is incident on the polarization controller, the transmission coefficients of the u-polarized and v-polarized electromagnetic waves are modulo |t u | and |t v | and the changing trend of ellipticity EP with different wavelengths, such as Figure 5 shown.

[0046] (2) Experimental results

[0047] like Figure 5 As shown, at the working wavelength of 0.3 mm, the transmission coefficient modulus in the u-axis and v-axis directions is equal (|t u |=|t v |). The ellipticity is -1, which means that all right-handed circularly polarized incident light is converted into left-handed circularly polarized outgoing light; at the working wavelengths of 0.26mm and 0.37mm, the ellipticity is 0, which means that the right-handed circularly polarized incident light is converted into linearly polarized outgoing light.

[0048] like Figure 6 As shown in the figure, at different working wavelengths, the ellipticity EP shows a certain change trend with the change of temperature. Within the normal working temperature range, it can maintain a stable polarization state conversion function, and will not experience a sharp deterioration in performance or loss of function due to slight temperature fluctuations.

[0049] Specifically: at the working wavelength of 0.3mm, after the right-handed circularly polarized incident light passes through the polarization regulator, the ellipticity EP is -1, which means that all the right-handed circularly polarized incident light is converted into left-handed circularly polarized outgoing light. The ellipticity EP has a stable change trend in the temperature range of 300K~550K, and the polarization state conversion efficiency remains relatively stable. When the control temperature rises to 700K, the ellipticity EP is 0, that is, the right-handed circularly polarized incident light is converted into linearly polarized outgoing light, realizing different polarization conversions; at the working wavelength of 0.26mm, the ellipticity EP is 0, that is, the right-handed circularly polarized incident light is converted into linearly polarized outgoing light. The ellipticity EP has a stable change trend in the temperature range of 300K~450K, and the polarization state conversion efficiency remains relatively stable; at the working wavelength of 0.37mm, the ellipticity EP is 0, that is, the right-handed circularly polarized incident light is converted into linearly polarized outgoing light. The ellipticity EP has a stable change trend in the temperature range of 280K~600K, and the polarization state conversion efficiency remains relatively stable.

[0050] In summary, at an operating wavelength of 0.3mm, the present invention achieves a change in the direction of rotation of the circular polarization state. At operating wavelengths of 0.26mm and 0.37mm, the present invention achieves a function of converting the circular polarization state to a linear polarization state. Within a larger temperature range, the polarization regulator can maintain a stable polarization state conversion function, and will not experience a sharp deterioration in performance or loss of function due to slight temperature fluctuations. At the same time, the temperature can be precisely controlled by controlling the power of the electromagnetic wave, and the polarization function of the polarization regulator can be further dynamically adjusted.

[0051] This article illustrates the principles and implementation methods through specific examples, which is intended to aid understanding and not to limit the invention. Modifications, substitutions, improvements, etc. within the spirit and principles of the invention should all be included in the scope of protection.

Claims

1. A highly stable polarization controller based on semiconductor metamaterials, characterized in that: The polarization regulator is designed to achieve stable and efficient conversion between multiple polarization states, covering polarization state conversion from linear polarization to linear polarization, linear polarization to circular polarization, circular polarization to circular polarization, and circular polarization to linear polarization. The polarization regulator is composed of a sub-wavelength periodic unit, and the periodic unit is composed of a rectangular unit and a dielectric connector. Further, the rectangular unit is embedded inside the dielectric connector. The working electromagnetic wave is incident along the height direction (z-axis direction) of the rectangular unit. The height of the rectangular unit is 0.70 to 1.20 times the wavelength of the working electromagnetic wave; the long side direction of the rectangular unit is the x-axis direction, and the short side direction is the y-axis direction. The ratio of the length of the long side and the width of the short side of the rectangular unit to the wavelength of the working electromagnetic wave is in the range of 0.16 to 0.28 and 0.09 to 0.16, respectively, and the length and width are not equal. The rectangular parallelepiped unit is composed of N-type or P-type doped semiconductors, the relative dielectric constant of the dielectric connector is 1 to 1.2, and the thermal conductivity is 0.014 to 0.020 W / (m·K). The control excitation used by the polarization regulator is a control electromagnetic wave, the direction of the control electromagnetic wave is parallel to the height direction (z-axis direction), and the wavelength of the control electromagnetic wave is not equal to the wavelength of the working electromagnetic wave.

2. The doped semiconductor according to claim 1 is preferably an N-type doped semiconductor.

3. The doped semiconductor according to claim 2 is preferably silicon or gallium arsenide.

4. The doped semiconductor according to claim 3, wherein the free carrier concentration is 10 18 ~10 19 cm -3 .

5. According to claim 1, the dielectric connecting material having a relative dielectric constant of 1 to 1.2 and a thermal conductivity of 0.014 to 0.020 W / (m·K) is preferably a silica aerogel.

6. The control electromagnetic wave according to claim 1 can be incident on the rectangular parallelepiped unit unidirectionally or bidirectionally, preferably bidirectionally.

7. The control electromagnetic wave according to claim 6, characterized in that: The regulated electromagnetic wave is microwave, and the preferred wavelength is 12.2 cm to 12.6 cm.

Images