All-dielectric optical microwave light splitting and frequency dividing element

Abstract

The invention discloses an all-dielectric optical microwave light splitting and frequency dividing element, which comprises a one-dimensional photonic crystal optical reflecting film and a wave-transparent substrate, and is characterized in that the one-dimensional photonic crystal optical reflecting film is of an alternating film system structure formed by two mediums with high and low refractive indexes, and the film system structure comprises a visible light reflecting film system structure and an infrared reflecting film system structure; and visible light and infrared light can be efficiently reflected. The wave-transparent substrate is a microwave-lossless dielectric substrate and can ensure efficient transmission of microwaves. The visible light reflecting film system structure and the infrared reflecting film system structure grow on the wave-transparent substrate from bottom to top. According to the light splitting and frequency dividing element, light wave and microwave signals are separated in a mode of reflecting light waves and transmitting microwaves, the light splitting and frequency dividing element can be applied to the field of light SAR integrated common time phase detection, visible light and infrared light can be efficiently reflected within a large field angle range, and the light splitting and frequency dividing efficiency is effectively improved.

Description

Technical Field

[0001] The invention relates to the field of microwave and light wave fusion, in particular to an all-dielectric optical microwave light splitting and frequency division element. Background Art

[0002] Optical SAR integrated synchronous phase detection can take into account the characteristics of optical remote sensing imaging, such as good concealment, high resolution, good image quality, and resistance to electronic interference. It can also give full play to the advantages of SAR imaging in all-weather and all-day detection, strong penetration ability, and detection and identification of camouflaged targets, greatly improving the ability to accurately detect multiple targets. The design and processing of its core component, the spectral and frequency division components, can provide support for the development of optical SAR integrated imaging systems, and research is urgently needed.

[0003] In the design and development of light wave / microwave splitting and frequency division, the main technical routes are dielectric reflective films, frequency selective surfaces, diffractive optical devices, etc. The infrared reflectivity and radar transmittance of the frequency selective surface are related to the unit structure and there is a mutual constraint. Diffractive optical elements have the characteristics of small size, high efficiency, great design flexibility and easy integration, but the production of dichroic mirrors is still in the exploratory stage. It also has some effects on the polarization state of millimeter waves, and the size of the elements cannot be scaled up. Plating a dielectric reflective film on a dielectric substrate is a relatively mature technology that can achieve effective reflection of light waves in the target band. At the same time, the dielectric material has good transmission characteristics for microwaves, but the reflection efficiency of the dielectric reflective film drops sharply under a large field of view. Summary of the invention

[0004] The technical problem solved by the present invention is to solve the technical problem of large viewing angle and efficient light wave microwave splitting and frequency division, and provide an all-medium optical microwave splitting and frequency division element.

[0005] The technical solution of the present invention is: an all-dielectric optical microwave spectrometer and frequency division element, including a wave-transmitting substrate, on one side of which an infrared light reflecting film system structure and a visible light reflecting film system structure are sequentially plated, wherein the infrared light reflecting film system structure and the visible light reflecting film system structure are both multi-layer alternating film system structures composed of two media with different refractive indices; the infrared light reflecting film system structure sequentially includes a second infrared light photonic crystal and a first infrared light photonic crystal in a direction away from the wave-transmitting substrate, and the visible light reflecting film system structure sequentially includes a second visible light photonic crystal and a first visible light photonic crystal in a direction away from the wave-transmitting substrate; the refractive indices of the two media in the second infrared light photonic crystal are consistent with the refractive indices of the two media in the first infrared light photonic crystal, but the lattice constants are different; the refractive indices of the two media in the second visible light photonic crystal are consistent with the refractive indices of the two media in the first visible light photonic crystal, but the lattice constants are different.

[0006] Furthermore, the first visible light photonic crystal and the second visible light photonic crystal, starting from the side away from the wave-transmitting substrate, have refractive index values ​​of n and1a and n 1b The reflective films made of two visible light band lossless dielectric materials are alternately composed, n 1a >n 1b ;

[0007] The first infrared light photonic crystal and the second infrared light photonic crystal are formed from the side away from the wave-transmitting substrate and have refractive index values ​​of n and n respectively. 2a and n 2b The reflective films made of two infrared light band lossless dielectric materials are alternately composed, n 2a >n 2b .

[0008] Furthermore, the lattice constant of the first visible light photonic crystal is 110-150 nm, and the number of layers is 6-12; the lattice constant of the second visible light photonic crystal is 160-190 nm, and the number of layers is 6-12.

[0009] Furthermore, the combination of two visible light band lossless dielectric materials is TiO2 and SiO2, TiO2 and Al2O3, or Al2O3 and SiO2.

[0010] Furthermore, the lattice constant of the first infrared light photonic crystal is 800-1150 nm, and the number of layers is 6-12; the lattice constant of the second infrared light photonic crystal is 1170-1300 nm, and the number of layers is 6-12.

[0011] Furthermore, the combination of two infrared light band lossless dielectric materials is TiO2 and SiO2, ZnS and HfO2, or ZnSe and YiF3.

[0012] Furthermore, the first visible light photonic crystal, the second visible light photonic crystal, the first infrared light photonic crystal and the second infrared light photonic crystal are all composed of reflective films made of TiO2 and SiO2 alternately in sequence, the refractive indices of TiO2 and SiO2 in the first visible light photonic crystal and the second visible light photonic crystal are 2.43 and 1.46 respectively, the refractive indices of TiO2 and SiO2 in the first infrared light photonic crystal and the second infrared light photonic crystal are 2.18 and 1.39 respectively, the lattice constants are 122nm, 165nm, 897nm, 1208nm respectively, the thicknesses of the two dielectric films of TiO2 and SiO2 are 43nm and 79nm, 59nm and 106nm, 343nm and 554nm, 465nm and 743nm respectively, and the number of layers are 10, 10, 8, 8 respectively.

[0013] Furthermore, the wave-transmitting substrate is a microwave lossless dielectric substrate, the thickness of which can be 2 mm to 10 mm, the shape of which is a plane mirror, a double concave mirror or a double convex mirror, and the material of which is quartz glass or soda-lime glass.

[0014] The advantages of the present invention compared with the prior art are:

[0015] (1) The technical solution proposed in the present invention can achieve efficient reflection of visible light and infrared light within a large field of view angle range (incident angle within 45 degrees).

[0016] (2) The optical splitter and frequency division element of the present invention can achieve an optical splitter and frequency division efficiency of ≥95% in the target band. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram showing the structure of a light splitting and frequency dividing element according to an embodiment of the present invention;

[0018] Figure 2 It shows the relationship between the refractive index of TiO2 and SiO2 and the wavelength;

[0019] Figure 3 The figure shows the reflection spectrum of the heterogeneous photonic crystal structure according to one embodiment of the present invention for the incident TE polarized visible light (P light);

[0020] Figure 4 The figure shows the reflection spectrum of the heterogeneous photonic crystal structure according to one embodiment of the present invention for the incident TE polarized infrared light (P light);

[0021] Figure 5 The figure shows the reflection spectrum of the heterogeneous photonic crystal structure according to one embodiment of the present invention for the case of incident TM polarized visible light (S light);

[0022] Figure 6 The figure shows the reflection spectrum of the heterogeneous photonic crystal structure according to one embodiment of the present invention for the case of TM polarized infrared light (S light) incident thereon;

[0023] Figure 7 The microwave transmittance of the light-splitting and frequency-demultiplexing element according to one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0024] In order to better understand the technical solution of the present invention, the specific implementation mode of the present invention is described in detail below with reference to the accompanying drawings.

[0025] A fully dielectric light wave microwave splitting and frequency division element, including a wave-transmitting substrate 3 and a one-dimensional photonic crystal optical reflective film, is an alternating film system structure composed of two media with high and low refractive indices, including a visible light reflective film system structure 1 and an infrared light reflective film system structure 2, wherein the visible light reflective film system structure 1 is composed of a first visible light photonic crystal 11 and a second visible light photonic crystal 12. The infrared light reflective film system structure 2 is composed of a first infrared light photonic crystal 21 and a second infrared light photonic crystal 22. The wave-transmitting substrate 3 is a microwave lossless dielectric substrate. The visible light reflective film system structure 1 and the infrared reflective film system structure 2 grow on the wave-transmitting substrate 3 from bottom to top, and the bottom refers to the side away from the wave-transmitting substrate.

[0026] The first visible light photonic crystal 11 and the second visible light photonic crystal 12 are composed of refractive index values ​​n1 and n2, respectively. a and n1 b The alternating film structure of two visible light band lossless dielectric materials is composed of n1 a >n1 b The material combination can be but not limited to TiO2 / SiO2, TiO2 / Al2O3, Al2O3 / SiO2, etc.

[0027] The first visible light photonic crystal 11 and the second visible light photonic crystal 12 have a lattice constant of 110-150 nm and a number of layers of 6-12, respectively; and a lattice constant of 160-190 nm and a number of layers of 6-12 respectively.

[0028] The first infrared light photonic crystal 21 and the second infrared light photonic crystal 22 have refractive index values ​​of n 2a and n 2b The alternating film structure of two infrared light band lossless dielectric materials is composed of n 2a >n 2b The material combination can be TiO2 / SiO2, ZnS / HfO2, ZnSe / YiF3, etc.

[0029] The first infrared light photonic crystal 21 and the second infrared light photonic crystal 22 have a lattice constant of 800-1150 nm and a number of 6-12 layers, and a lattice constant of 1170-1300 nm and a number of 6-12 layers.

[0030] The substrate is a microwave lossless material that can efficiently transmit microwaves. The thickness can be 2mm-10mm. The shape can be a plane mirror, a double concave mirror, a double convex mirror, etc. The material can be quartz glass, soda-lime glass, etc.

[0031] A specific embodiment of the present invention is given below:

[0032] According to the transfer matrix method and angular frequency domain superposition method, a heterogeneous photonic crystal structure is designed based on two dielectric materials, TiO2 and SiO2, which can achieve high reflectivity in both the visible light band and the mid-infrared band.

[0033] The photonic crystal reflective film structure is grown on a quartz glass substrate, see Figure 1 The refractive index of TiO2 and SiO2 is as follows: Figure 2 As shown in the figure, the extinction coefficients of these two dielectric materials in the visible light and mid-infrared bands are negligible, and both dielectric materials are dispersive materials, and the refractive index decreases with the increase of wavelength. When designing the thickness of the photonic crystal structure film in the optical band, the refractive index values ​​of TiO2 and SiO2 are 2.43 and 1.46 (550nm) respectively, and in the mid-infrared band, the refractive index values ​​of TiO2 and SiO2 are 2.18 and 1.39 (4μm) respectively.

[0034] Four photonic crystals with different lattice constants are designed, from top to bottom: the second infrared light photonic crystal 22, denoted as infrared light photonic crystal d, the first infrared light photonic crystal 21, denoted as infrared light photonic crystal c, the second visible light photonic crystal, denoted as visible light photonic crystal b, the first visible light photonic crystal, denoted as visible light photonic crystal a, and are grown on a quartz glass substrate in the above order. The lattice constants are L a =122nm, L b =165nm, L c =897nm, L d =1208nm. The thicknesses of the two dielectric films of TiO2 and SiO2 are: 43nm and 79nm for visible light photonic crystal a, 59nm and 106nm for visible light photonic crystal b, 343nm and 554nm for infrared light photonic crystal c, and 465nm and 743nm for infrared light photonic crystal d, respectively. The number of layers are 10, 10, 8, and 8, respectively. 10 layers represent 5 layers of TiO2 and 5 layers of SiO2 overlapping each other.

[0035] Based on the above structural parameters, the reflection characteristics of the heterogeneous photonic crystal structure in the dual reflection band are as follows: Figure 3 -6. Figure 3 and 4 The reflectivity spectra of the heterogeneous photonic crystal structure for TE polarized light incident in the 400-700nm and 3-5μm bands are given respectively. Within a 45° field of view, the heterogeneous photonic crystal is close to total reflection of the incident light, and the theoretical reflection efficiency in the entire target band is greater than 99%. Figure 5 and 6The reflectivity spectra of the heterogeneous photonic crystal structure for TM polarized light incident in the 400-700nm and 3-5μm bands are given respectively. Within the 30° incident angle, its reflection efficiency is basically the same as that for TE polarized light incident. At an angle of 45°, the reflectivity of the heterogeneous photonic crystal structure is poor at a few wavelengths within the target band, but the overall reflectivity is still greater than 95%. Based on the above simulation results, it can be seen that the theoretical reflectivity of the designed heterogeneous photonic crystal structure for the two modes of polarized light within the 45° oblique incident angle within the target bands of 400nm-700nm and 3-5μm is greater than 95%.

[0036] The substrate material is quartz glass, which has a refractive index of about 3.75 in the microwave band, and its loss to microwaves is negligible. In the optical path structure of splitting and dividing frequencies, in order to meet the imaging requirements of the optical band, the side of the quartz substrate that needs to be coated with the photonic crystal reflective film needs to be designed as a convex surface, and the other side needs to be designed as a concave surface. The thickness of the substrate is the same everywhere, which can reduce the impact on the microwave phase. The diameter of the quartz substrate is 25.4mm (one inch) and the radius of curvature is 78.4mm. The wave transmission performance of the quartz substrate is simulated based on the CST STUDIOSUITE software. The time domain solver is used for the solution, and the boundary conditions X, Y and Z are all set to electrical walls, and the environment is set to a perfect electrical conductor. The incident port is Waveguide. After optimization, when the thickness of the quartz substrate is 4.4mm, the microwave transmittance in the target band is optimal, such as Figure 7 As shown. The microwave transmittance is higher than 90% in the range of 32-38GHz, and higher than 95% in the range of 34-36GHz. When simulating the thickness of 4.3mm and 4.4mm, the microwave transmittance of the quartz substrate is greater than 90% in the target band (34-36GHz), indicating that within a certain range of processing error, the transmittance of the quartz substrate can meet the requirements.

[0037] In summary, the optical splitting and frequency division sample designed in the present invention can efficiently realize the optical wave and microwave signal splitting, and the optical splitting efficiency is greater than 95%.

[0038] It is to be understood that the present invention is described by way of embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and embodiments that can fall within the scope of the claims of this application all fall within the scope protected by the present invention.

[0039] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An all-dielectric optical microwave splitting and frequency division element, characterized in that: The invention comprises a wave-transmitting substrate (3), on one side of which an infrared light reflecting film system structure (2) and a visible light reflecting film system structure (1) are sequentially plated, wherein the infrared light reflecting film system structure and the visible light reflecting film system structure are both multi-layer alternating film system structures composed of two media with different refractive indices; the infrared light reflecting film system structure (2) sequentially comprises a second infrared light photonic crystal (22) and a first infrared light photonic crystal (21) in a direction away from the wave-transmitting substrate, and the visible light reflecting film system structure (1) sequentially comprises a second visible light photonic crystal (12) and a first visible light photonic crystal (11) in a direction away from the wave-transmitting substrate; the refractive indices of the two media in the second infrared light photonic crystal (22) are consistent with the refractive indices of the two media in the first infrared light photonic crystal (21), but the lattice constants are different; the refractive indices of the two media in the second visible light photonic crystal (12) are consistent with the refractive indices of the two media in the first visible light photonic crystal (11), but the lattice constants are different.

2. The all-dielectric optical microwave splitter and frequency division element according to claim 1, characterized in that: The first visible light photonic crystal (11) and the second visible light photonic crystal (12) are formed from a side away from the wave-transmitting substrate and have refractive index values ​​of n and n, respectively. 1a and n 1b The reflective films made of two visible light band lossless dielectric materials are alternately composed, n 1a >n 1b ; The first infrared light photonic crystal (21) and the second infrared light photonic crystal (22) are formed from a side away from the wave-transmitting substrate and have refractive index values ​​of n 2a and n 2b The reflective films made of two infrared light band lossless dielectric materials are alternately composed, n 2a >n 2b .

3. The all-dielectric optical microwave splitting and frequency division element according to claim 2, characterized in that: The lattice constant of the first visible light photonic crystal (11) is 110-150 nm, and the number of layers is 6-12; the lattice constant of the second visible light photonic crystal (12) is 160-190 nm, and the number of layers is 6-12.

4. The all-dielectric optical microwave splitter and frequency division element according to claim 2, characterized in that: The two visible light band lossless dielectric material combinations are TiO2 and SiO2, TiO2 and Al2O3, or Al2O3 and SiO2.

5. The all-dielectric optical microwave splitting and frequency division element according to claim 2, characterized in that: The lattice constant of the first infrared light photonic crystal (21) is 800-1150 nm, and the number of layers is 6-12; the lattice constant of the second infrared light photonic crystal (22) is 1170-1300 nm, and the number of layers is 6-12.

6. The all-dielectric optical microwave splitting and frequency division element according to claim 2, characterized in that: The two infrared light band lossless dielectric material combinations are TiO2 and SiO2, ZnS and HfO2, or ZnSe and YiF3.

7. The all-dielectric optical microwave splitting and frequency division element according to claim 2, characterized in that: The first visible light photonic crystal (11), the second visible light photonic crystal (12), the first infrared light photonic crystal (21) and the second infrared light photonic crystal (22) are all composed of reflective films made of TiO2 and SiO2 in sequence and alternately. The refractive indexes of TiO2 and SiO2 in the first visible light photonic crystal (11) and the second visible light photonic crystal (12) are 2.43 and 1.46 respectively. The refractive indexes of TiO2 and SiO2 in the first infrared light photonic crystal (21) and the second infrared light photonic crystal (22) are 2.18 and 1.39 respectively. The lattice constants are 122nm, 165nm, 897nm and 1208nm respectively. The thicknesses of the two dielectric films of TiO2 and SiO2 are 43nm and 79nm, 59nm and 106nm, 343nm and 554nm, 465nm and 743nm respectively. The number of layers is 10, 10, 8 and 8 respectively.

8. The all-dielectric optical microwave splitter and frequency division element according to any one of claims 1 to 7, characterized in that: The wave-transmitting substrate (3) is a microwave lossless dielectric substrate, the thickness of which can be 2 mm to 10 mm, the shape of which is a plane mirror, a double concave mirror or a double convex mirror, and the material of which is quartz glass or soda-lime glass.

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