Mach-Zehnder interferometer pressure sensor based on germanium-based energy valley photonic crystal

Abstract

The invention belongs to the technical field of topological photonics and optical sensing, and discloses a Mach-Zehnder interferometer pressure sensor based on germanium-based energy valley photonic crystals. Comprising a germanium substrate; the germanium substrate is divided into a first area, a second area, a third area and a fourth area by a straight line boundary and an annular boundary; triangular lattices of the first circular holes and the second circular holes in the first region and the fourth region are arranged in a forward staggered manner to form first energy valley photonic crystals; the triangular lattices of the first circular holes and the second circular holes in the second area and the third area are arranged in a staggered mode to form second energy valley photonic crystals. The third area and the fourth area form an input straight waveguide and an output straight waveguide at a straight line boundary, the first area and the third area form a first annular waveguide at an upper boundary, and the second area and the fourth area form a second annular waveguide at a lower boundary. According to the invention, miniaturized, high-sensitivity and integratable pressure sensing can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical fields of topological photonics and optical sensing, and particularly relates to a Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal. Background Art

[0002] Optical pressure sensors detect changes in minute pressure by affecting light rays, and have advantages such as anti-electromagnetic interference, high-speed transmission, and simple operation, and have received extensive attention in the field of optical communication technology. Currently, traditional pressure sensors operating in the optical communication band include fiber optic pressure sensors, Bragg grating sensors, optical waveguide pressure sensors, Mach-Zehnder interferometer sensors, etc. Among them, Mach-Zehnder interferometer sensors have the advantages of high sensitivity and rapid response to changes in the external environment, and are widely used in fields such as optical modulators, optical sensing, spectrometer analysis, and measurement. A Mach-Zehnder interferometer can control the phase difference between two light beams by designing the optical path length difference, and can sense changes in the external environment, thereby controlling the intensity of a specific wavelength in the interference spectrum, for use in fields such as small pressure measurement, biomedical sensing, optical communication, and quantum computing. However, the resonance enhancement of interfering light waves often easily limits the transmission bandwidth of the device, and manufacturing defects are likely to occur; moreover, the size of a Mach-Zehnder interferometer is relatively large, and it is difficult to achieve high-density on-chip integration. Therefore, designing an optical pressure sensor with low transmission loss and ultra-compactness in the optical communication band is one of the development directions in the field of pressure sensing technology.

[0003] The metamaterial pressure sensor with micro-nano size is structurally compact. However, most of the metamaterial pressure sensors use metal materials, which have certain inherent losses in the optical band, and their quality factors are limited to a certain extent. In addition, there are still certain difficulties in the integration of the metamaterial pressure sensor, and high-performance integrated pressure sensing cannot be achieved. In contrast, the photonic crystal pressure sensor has the advantages of being integrable and simple in design, and can be used for pressure sensing functions in the optical communication band. Research shows that germanium material is more sensitive to pressure and has been used to fabricate germanium photonic crystal pressure sensors. T. Zouache et al.'s pressure sensor based on two-dimensional photonic crystal waveguide coupled to a point defect resonant microcavity changes the refractive index of germanium material by changing the applied pressure, and the resonant wavelength (defect mode) will shift, thus realizing the sensing function [T. Zouache, A. Hocini, A. Harhouz, R. Mokhtari, Design of pressure sensor based on two-dimensional photonic crystal, Acta Physica Polonica A, 131(2017)]. However, there are problems such as backward scattering of light waves, low transmittance, and narrow bandwidth in traditional photonic crystal sensors. Especially, the scattering of light waves at the turning points of waveguide devices is particularly serious, which will cause unnecessary light loss, severely limiting the sensitivity and miniaturization of the sensors.

[0004] Therefore, there is an urgent need to provide a new design idea to realize a miniaturized, highly sensitive and integrable pressure sensor. Summary of the Invention

[0005] In order to solve the technical problems in the prior art that it is difficult for pressure sensors to achieve miniaturization, high sensitivity and integrability, the present invention proposes a Mach-Zehnder interferometer pressure sensor based on germanium-based valley photonic crystals to realize pressure sensing in the optical communication band.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a Mach-Zehnder interferometer pressure sensor based on germanium-based valley photonic crystals, including a germanium substrate; the germanium substrate is divided into four regions, namely a first region, a second region, a third region and a fourth region by a straight dividing line and an annular dividing line; the straight dividing line is parallel to the light incident direction, the annular dividing line intersects with the straight dividing line and is divided into an upper dividing line and a lower dividing line by the straight dividing line, the upper dividing line and the lower dividing line respectively form a first trapezoid and a second trapezoid with the straight dividing line, the short bases of the first trapezoid and the second trapezoid are the same and the perimeters are not equal; the first region and the second region are located inside the annular dividing line and are respectively located on the upper and lower sides of the straight dividing line, and the third region and the fourth region are located outside the annular dividing line and are respectively located on the upper and lower sides of the straight dividing line;

[0007] In the first region, second region, third region, and fourth region, a plurality of first circular holes arranged in a triangular lattice and a plurality of second circular holes arranged in a triangular lattice are provided; in the first region and the fourth region, the centers of the respective second circular holes are disposed at the centers of the respective upright triangles formed by the first circular holes, such that the triangular lattices of the first circular holes and the second circular holes are positively staggered to form a first valley photonic crystal; in the second region and the third region, the centers of the respective second circular holes are disposed at the centers of the respective inverted triangles formed by the first circular holes, such that the triangular lattices of the first circular holes and the second circular holes are negatively staggered to form a second valley photonic crystal; the radius of the first circular hole is greater than the radius of the second circular hole;

[0008] On one side of the third region and the fourth region close to the straight dividing line, a row of first circular holes are respectively arranged, forming an input straight waveguide and an output straight waveguide on both sides of the annular dividing line. On one side of the first region and the third region close to the upper dividing line, a row of first circular holes are respectively arranged to form a first annular waveguide. On one side of the second region and the fourth region close to the lower dividing line, a row of first circular holes are respectively arranged to form a second annular waveguide.

[0009] The first trapezoid and the second trapezoid are isosceles trapezoids, and the base angles of the trapezoids are 60°.

[0010] The optical path difference between the first annular waveguide and the second annular waveguide is 4 - 20a, where a represents the distance between two adjacent first circular holes or two adjacent second circular holes in the valley photonic crystal.

[0011] The value range of the radius R1 of the first circular hole is 0.25a - 0.27a, and the value range of the radius R2 of the second circular hole is 0.06a - 0.08a, where a represents the distance between two adjacent first circular holes or two adjacent second circular holes in the valley photonic crystal.

[0012] The value range of a is 390 - 430 nm.

[0013] The depths of the first circular hole and the second circular hole penetrate the germanium substrate.

[0014] The thickness of the germanium substrate is 220 - 1500 nm.

[0015] A Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal realizes pressure sensing through the wavelength shift of the interference peak in the transmission spectrum.

[0016] A Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal has an operating wavelength in the optical communication band.

[0017] The described Mach-Zehnder interferometer pressure sensor based on germanium-based valley photonic crystal, and its manufacturing method includes the following steps:

[0018] Select an SOI wafer including a germanium layer and a silicon dioxide layer;

[0019] Coat photoresist on the germanium surface, then use electron beam lithography to expose the photoresist, and subsequently use the photoresist as a mask layer for reactive ion etching to obtain a first circular hole and a second circular hole;

[0020] Then remove the photoresist and remove the silicon dioxide substrate to obtain the pressure sensor structure.

[0021] The present invention has the following beneficial effects compared with the prior art:

[0022] 1. The present invention provides a germanium-based valley photonic crystal Mach-Zehnder interferometer pressure sensor. By forming a straight waveguide and two ring waveguides at the boundary of the photonic crystal, and using the two ring waveguides to form interference arms. Since the refractive index of germanium changes with pressure, the optical path difference between the two interference arms changes with pressure. Therefore, the wavelength of its interference peak is related to pressure, and then pressure sensing is realized according to the movement of the interference peak position. Experiments have confirmed that in the pressure sensing range of 0 - 10 GPa of the applied pressure, the detection sensitivity of the topological resonance ring sensor is 0.012 μm / GPa (pressure unit).

[0023] 2. In the present invention, the bending angle of the ring waveguide is 60°, which reduces the transmission loss of the structure. In addition, by optimizing the structural parameters of the valley photonic crystal in the present invention, when the arm length difference (optical path difference) between interference arm one and interference arm two is 4a, the transmittance of the transmission peak of the pressure sensor in the communication band reaches up to 0.95. Therefore, the present invention can obtain a high signal-to-noise ratio. Moreover, due to the spin-valley locking characteristic based on the topological edge state, the sensor of the present invention can also effectively suppress the backscattering signal of the light source.

[0024] 3. The present invention can achieve miniaturized, highly sensitive, and integratable pressure sensing. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of a Mach-Zehnder interferometer pressure sensor based on germanium-based valley photonic crystal provided by an embodiment of the present invention;

[0026] Figure 2 It is a curve of the refractive index of the material in the pressure sensor in an embodiment of the present invention changing with pressure;

[0027] Figure 3 It is a transmission spectrum and an electric field intensity distribution diagram of the pressure sensor in an embodiment of the present invention without applying pressure;

[0028] Figure 4 This is the energy band curve of the topological edge state structure of the pressure sensor in the embodiments of the present invention under the condition of pressure change;

[0029] Figure 5 This is the situation of the interference peak at a wavelength of 1708 nm in the pressure sensor in the embodiments of the present invention changing with pressure;

[0030] Figure 6 This is the linear fitting curve of the interference peak at a wavelength of 1708 nm in the pressure sensor in the embodiments of the present invention changing with pressure.

[0031] Explanation of reference numerals: 1 is the input straight waveguide, 2 is the output straight waveguide, 3 is the first region, 4 is the second region, 5 is the third region, 6 is the fourth region, 7 is the upper dividing line, 8 is the straight dividing line, 9 is the lower dividing line, 10 is the first circular hole, 11 is the second circular hole, 12 is the first annular waveguide, 13 is the second annular waveguide, 14 is the first valley photonic crystal, and 15 is the second valley photonic crystal. Detailed implementation manners

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] As Figure 1 shown, Embodiment 1 of the present invention provides a Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal, including a germanium substrate; the germanium substrate is divided into four regions, namely a first region 3, a second region 4, a third region 5, and a fourth region 6 by a straight dividing line 8 and an annular dividing line; the straight dividing line 8 is parallel to the light incident direction, the annular dividing line intersects with the straight dividing line 8 and is divided by the straight dividing line 8 into an upper dividing line 7 and a lower dividing line 9. The upper dividing line 7 and the lower dividing line 9 respectively form a first trapezoid and a second trapezoid with the straight dividing line 8. The short bases of the first trapezoid and the second trapezoid are the same and the perimeters are unequal; the first region 3 and the second region 4 are located inside the annular dividing line 9 and are respectively located on the upper and lower sides of the straight dividing line 8, and the third region 5 and the fourth region 6 are located outside the annular dividing line 9 and are respectively located on the upper and lower sides of the straight dividing line 8.

[0034] In this embodiment, a plurality of first circular holes 10 arranged in a triangular lattice and a plurality of second circular holes 11 arranged in a triangular lattice are provided in each of the first region 3, the second region 4, the third region 5, and the fourth region 6; in the first region 3 and the fourth region 6, the centers of the respective second circular holes 11 are provided at the centers of the respective upright triangles formed by the first circular holes 10, so that the triangular lattices of the first circular holes 10 and the second circular holes 11 are arranged in a positive stagger to form a first valley photonic crystal 14; in the second region 4 and the third region 5, the centers of the respective second circular holes 11 are provided at the centers of the respective inverted triangles formed by the first circular holes 10, so that the triangular lattices of the first circular holes 10 and the second circular holes 11 are arranged in an inverted stagger to form a second valley photonic crystal 15; the radius of the first circular holes 10 is greater than the radius of the second circular holes 11.

[0035] In this embodiment, a row of first circular holes 10 are arranged on one side of the third region 5 and the fourth region 6 close to the straight dividing line 8, and an input straight waveguide 1 and an output straight waveguide 2 are formed on both sides of the annular dividing line respectively. A row of first circular holes 10 are arranged on one side of the first region 3 and the third region 5 close to the upper dividing line 7 to form a first annular waveguide 12, and a row of first circular holes 10 are arranged on one side of the second region 4 and the fourth region 6 close to the upper dividing line 7 to form a second annular waveguide 13.

[0036] In this embodiment, the arrangement densities of the first circular holes 10 and the second circular holes 11 in the four regions are the same. Moreover, overall, the centers of the first circular holes 10 in the first region 3 and the fourth region 6, and the centers of the second circular holes 11 in the second region 4 and the third region 5 are arranged in a triangular lattice. The centers of the second circular holes 11 in the first region 3 and the fourth region 6, and the centers of the first circular holes 10 in the second region 4 and the third region 5 are arranged in a triangular lattice, which is equivalent to the radii of the circular holes in the second region 4 and the third region 5 being interchanged relative to the first region 3 and the fourth region 6.

[0037] Further, in this embodiment, the first trapezoid and the second trapezoid are isosceles trapezoids, and the base angles of the trapezoids are 60°. Then, when the light beam enters the first annular waveguide 12 and the second annular waveguide 13 from the input straight waveguide 1, and when the light beam enters the straight waveguide from the first annular waveguide 12 and the second annular waveguide 13, the turning angles are both 60°, and the formed turning angle topological waveguide structure has low loss during transmission.

[0038] Specifically, in this embodiment, the optical path difference between the first annular waveguide 12 and the second annular waveguide 13 is 4-20a, where a represents the distance between two adjacent first circular holes 10 or two adjacent second circular holes 11 in the valley photonic crystal, that is, the lattice constant of the triangular lattice.

[0039] Further, in this embodiment, the radius of the first circular hole 10 ranges from 0.25a to 0.27a, and the radius of the second circular hole 11 ranges from 0.06a to 0.08a, where a represents the distance between two adjacent first circular holes 10 or two adjacent second circular holes 11 in the valley photonic crystal.

[0040] Further, in this embodiment, the value range of a is 390 - 430 nm.

[0041] Further, in this embodiment, the depths of the first circular hole 10 and the second circular hole 11 penetrate through the germanium substrate. The thickness of the germanium substrate is 220 - 1500 nm.

[0042] Further, in this embodiment, the radius of the first circular hole 10 is r1 = 108 nm, the radius of the second circular hole 11 is r2 = 30 nm, the lattice constants of the triangular lattice formed by the first circular holes 10 and the triangular lattice formed by the second circular holes 11 are both a = 410 nm, and the thickness of the germanium substrate is 220 nm.

[0043] The germanium-based topological Mach-Zehnder interferometer pressure sensor of this embodiment realizes pressure sensing through the wavelength shift of the interference peaks in the transmission spectrum, and its working wavelength is in the communication band.

[0044] A germanium-based topological Mach-Zehnder interferometer pressure sensor of this embodiment can be processed based on CMOS technology, and its processing method includes the following steps:

[0045] (1) Select an SOI wafer including a germanium layer and a silicon dioxide layer; in this embodiment, a standard SOI wafer with a 220-nm-thick germanium top layer and a 3-μm-thick silicon dioxide layer is selected;

[0046] (2) Coat a photoresist (ZEP520A) on the germanium surface, then expose the photoresist using electron beam lithography, and subsequently use the photoresist as a mask layer for reactive ion etching to obtain the first circular hole and the second circular hole.

[0047] In this step, it is important to obtain vertical etching sidewalls to maintain the mirror symmetry of the photonic crystal structure with respect to the x-y plane located in the middle of the photonic crystal slab. Specifically, after coating the photoresist on the surface of the germanium top layer, make the pattern to be etched on the photoresist, and then use the photoresist as a mask layer for reactive ion etching to obtain the first circular hole and the second circular hole;

[0048] (3) Then remove the photoresist and perform selective wet etching with diluted hydrofluoric acid for 15 minutes to remove the silicon dioxide substrate. This can obtain a topological pressure sensor structure.

[0049] In this embodiment, the pressure sensor uses germanium material as the substrate, and the relationship between its refractive index and the applied pressure satisfies the following formula:

[0050]

[0051] As Figure 2 shown. Under the applied pressure, the effective refractive index of the germanium photonic crystal changes with the pressure, thereby affecting the interference peak wavelength of the topological pressure sensor and realizing the high-precision pressure sensing function.

[0052] Figure 3 FIG. (a, b) shows the electric field intensity distribution and FIG. (c) shows the transmission spectrum of a Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal provided in Embodiment 1 of the present invention without applied pressure. When the arm lengths of the first ring waveguide (12) serving as the first interference arm and the second ring waveguide serving as the second interference arm are 27a and 23a respectively, and the corresponding optical path difference is 4a, the maximum transmittance of the transmission peak of the topological pressure sensor is 0.95. The figure shows the constructive and destructive interference of light waves at different wavelength positions. It can be seen from the electric field intensity distribution diagram that at 1693 nm, the light wave shows constructive interference. The light wave enters the structure from the left input waveguide, transmits along the first interference arm and the second interference arm respectively, and after reaching the right output waveguide, the light is enhanced and continues to transmit; while at 1700 nm, the light wave shows destructive interference. The light wave also transmits along the first interference arm and the second interference arm. After reaching the convergence point, the two light beams interfere destructively, so they cannot reach the right output waveguide. Moreover, based on the spin-valley locking characteristic of the topological edge state, the backscattering of the light source is effectively suppressed.

[0053] In the embodiment of the present invention, the finite-difference time-domain (FDTD) method is used to calculate the energy band diagrams of the germanium-based honeycomb lattice circular lattice point topological edge state structure of the present invention under different pressures, as Figure 4 shown. The diagonal shaded area in the figure is the air light cone. Under different applied pressures, the topological waveguide is in different working bands, and the pressure adjustment range is 0 - 10 GPa, where the solid line is the edge state curve without applied pressure. From Figure 4 the energy band diagram, it can be seen that as the applied pressure increases, the edge state energy band curve undergoes a blue shift, which will affect the position of the interference peak wavelength and realize pressure sensing within the optical communication band.

[0054] Specifically, in this embodiment, different pressures applied to the Mach-Zehnder interferometer pressure sensor are simulated by changing the refractive index of the germanium material, as Figure 5As shown. By simulating the spectral distribution of interference peaks of germanium-based valley photonic crystals with different refractive indices, the pressure value is detected by the tiny shift of the interference peak position under different pressures using a topological pressure sensor. Several obtained results are compared and analyzed, and then the function of pressure sensing in the optical communication band is realized. The results show that as the applied pressure changes, the interference peak position moves from 1.586 μm to 1.708 μm, showing a blue shift, which is consistent with the previous analysis of the edge state energy band. This indicates that this structure can adjust the wavelength of the interference peak under different pressures and characterize the magnitude of the pressure value.

[0055] When the applied pressure changes in the range of 0 GPa to 10 GPa, the transmittance and shift of the interference peak are observed every 1 GPa. The research results show that as the applied pressure changes, the interference peak position shows a blue shift, and the transmittance of the interference peak always remains above 0.92, indicating that high-efficiency optical transmission can be achieved in the integrated optical circuit. The sensitivity of the pressure sensor is calculated by fitting according to the formula, as Figure 6 shown. After calculation, the sensitivity of this topological pressure sensor is 0.012 μm / GPa (pressure unit), and the minimum detectable pressure difference is 1 GPa.

[0056] In summary, the present invention provides a Mach-Zehnder interferometer pressure sensor based on germanium-based valley photonic crystals. By forming a straight waveguide and two ring waveguides at the boundary of the photonic crystal, and using the two ring waveguides to form interference arms. Since the refractive index of germanium changes with pressure, the optical path difference between the two interference arms changes with pressure. Therefore, the wavelength of its interference peak is related to the pressure, and then pressure sensing is realized according to the shift of the interference peak position. The sensor of the present invention can operate in the communication band, and experiments have confirmed that the transmittance of its transmission peak in the communication band reaches up to 0.95 at most. In the pressure sensing range of 0 - 10 GPa of the applied pressure, the detection sensitivity of the topological resonant ring sensor is 0.012 μm / GPa (pressure unit). Therefore, the present invention can achieve precise pressure sensing.

[0057] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal, characterized in that, It includes a germanium substrate; the germanium substrate is divided into a first region (3), a second region (4), a third region (5) and a fourth region (6) by a straight dividing line (8) and an annular dividing line; the straight dividing line (8) is parallel to the light incident direction, the annular dividing line intersects with the straight dividing line (8) and is divided by the straight dividing line (8) into an upper dividing line (7) and a lower dividing line (9); the first region (3) and the second region (4) are located inside the annular dividing line and are respectively located on the upper and lower sides of the straight dividing line (8), and the third region (5) and the fourth region (6) are located outside the annular dividing line and are respectively located on the upper and lower sides of the straight dividing line (8); A plurality of first circular holes (10) arranged in a triangular lattice and a plurality of second circular holes (11) arranged in a triangular lattice are provided in the first region (3), the second region (4), the third region (5) and the fourth region (6); in the first region (3) and the fourth region (6), the centers of the respective second circular holes (11) are arranged at the centers of the respective upright triangles formed by the first circular holes (10); in the second region (4) and the third region (5), the centers of the respective second circular holes (11) are arranged at the centers of the respective inverted triangles formed by the first circular holes (10); the radius of the first circular hole (10) is greater than the radius of the second circular hole (11); The input straight waveguide (1) and the output straight waveguide (2) are formed by arranging the first circular holes (10) near the straight dividing line (8) in the third region (5) and the fourth region (6); the first annular waveguide (12) is formed by arranging the first circular holes (10) near the upper dividing line (7) in the first region (3) and the third region (5), and the second annular waveguide (13) is formed by arranging the first circular holes (10) near the lower dividing line (9) in the second region (4) and the fourth region (6).

2. The Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 1, characterized in that, The upper dividing line (7) and the lower dividing line (9) respectively form a first trapezoid and a second trapezoid with the straight dividing line (8), and the short bases of the first trapezoid and the second trapezoid are the same and the perimeters are unequal.

3. The Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 2, characterized in that, The first trapezoid and the second trapezoid are isosceles trapezoids, and the base angles of the trapezoids are 60°; the optical path difference between the first annular waveguide (12) and the second annular waveguide (13) is 4 - 20a, where a represents the distance between two adjacent first circular holes (10) or two adjacent second circular holes (11) in the valley photonic crystal.

4. The Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 1, characterized in that, The value range of the radius R1 of the first circular hole (10) is 0.25a - 0.27a, and the value range of the radius R2 of the second circular hole (11) is 0.06a - 0.08a, where a represents the distance between two adjacent first circular holes (10) or two adjacent second circular holes (11) in the valley photonic crystal.

5. A Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 3 or 4, characterized in that, The value range of a is 390 - 430 nm.

6. The Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 1, characterized in that, The depths of the first circular holes (10) and the second circular holes (11) penetrate through the germanium substrate.

7. A Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 1, characterized in that, The thickness of the germanium substrate is 220 - 1500 nm.

8. A Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 1, characterized in that, Pressure sensing is realized by the wavelength shift of the interference peak in the transmission spectrum.

9. The Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 1, characterized in that, Its working wavelength is in the optical communication band.

10. A Mach-Zehnder interferometer pressure sensor based on a germanium-based valley photonic crystal according to claim 1, characterized in that, Its processing method includes the following steps: Select an SOI wafer including a germanium layer and a silicon dioxide layer; Apply photoresist on the germanium surface, then use electron beam lithography to expose the photoresist, and subsequently use the photoresist as a mask layer for reactive ion etching to obtain the first circular hole and the second circular hole; Then remove the photoresist and remove the silicon dioxide substrate to obtain the pressure sensor structure.

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