Optical accelerometer chip based on cascaded double-ring resonator vernier effect

Abstract

The present invention discloses an optical accelerometer chip based on the vernier effect of a cascaded double-ring resonant cavity. It includes a wide-spectrum light source, a pattern spot converter, an optical isolator, a sensitive unit, an upper electrode, a lower electrode, an F-P cavity, a first Y-waveguide, a second Y-waveguide, a 2:1 type Y-waveguide, a first optical power meter, a second optical power meter, a demodulation feedback circuit, a lithium niobate single crystal thin film layer, a silicon dioxide oxide layer, a silicon substrate, and a packaging shell. The present invention has two independent optical resonant cavities: when an acceleration in the x-direction is applied, the spacing between the first annular waveguide and the elliptical disk changes, causing a shift in the resonant wavelength, and the magnitude and direction of the acceleration can be obtained simultaneously; the radii of the two resonant cavities are slightly different, and the vernier effect generated by the interference of the output light of the optical resonant cavity can be used to amplify the frequency shift signal of the resonant wavelength of the first annular waveguide. The present invention has a small size, high precision, a simple manufacturing process, is resistant to electromagnetic interference, and has high reliability.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated optics and inertial sensing and relates to an optical accelerometer, in particular to an optical accelerometer chip based on a cascaded double-ring resonant cavity vernier effect. Background Art

[0002] In recent years, with the increasing maturity of microelectronics technology, integrated circuit technology and micromachining technology, MEMS accelerometers have attracted widespread attention and developed rapidly due to their advantages such as small size, low cost, high reliability and suitability for mass production. They have been widely used in aerospace, earthquake monitoring, attitude recognition, animal husbandry, smart medical care and other fields. However, due to their limited resolution and dynamic range, MEMS accelerometers cannot be used in the field of high-precision inertial navigation and guidance. The urgent vision of developing new accelerometers gave rise to MOEMS accelerometers.

[0003] Compared with MEMS accelerometers, MOEMS accelerometers use optical detection methods to achieve detection with higher sensitivity and resolution. At the same time, the core components of MOEMS accelerometers have natural anti-electromagnetic interference capabilities, and can be connected through optical fibers to remotely place optoelectronic circuits, which can meet the requirements of complex application environments such as strong electromagnetic interference.

[0004] The Vernier effect, as a commonly used method to improve sensitivity, is widely used in sensor devices such as ring resonators and Fabry-Perot interferometers (FPIs). It can amplify the sensitivity by an order of magnitude and greatly improve the sensing efficiency.

[0005] With the development of precision and integration of accelerometer systems, monolithic integrated optical accelerometers are in urgent need of development. Driven by the development of micro-nanotechnology and micro-machining technology, it has become possible to manufacture high-precision optical accelerometer chips based on the cascaded double-ring resonator vernier effect. Summary of the invention

[0006] In order to solve the problems existing in the background technology, the present invention provides an optical accelerometer chip with a cascaded dual-ring resonant cavity vernier effect, which utilizes the vernier effect of two ring resonant cavities and has the advantages of high detection accuracy, small size, high precision, simple manufacturing process, anti-electromagnetic interference, and good reliability.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The present invention comprises a broadband light source, a pattern spot converter, an optical isolator, a sensitive unit, an upper electrode, a lower electrode, an FP cavity, a first curved waveguide, a second straight waveguide, a second curved waveguide, a third straight waveguide, a first 1:2 type Y waveguide, a fourth straight waveguide, a second 1:2 type Y waveguide, a fifth straight waveguide, a sixth straight waveguide, a 2:1 type Y waveguide, a seventh straight waveguide, an eighth straight waveguide, a first optical power meter, a second optical power meter, a demodulation feedback circuit, a lithium niobate single crystal thin film layer, a silicon dioxide oxide layer and a silicon substrate;

[0009] The silicon substrate, the silicon dioxide oxide layer and the lithium niobate single crystal thin film layer are stacked in sequence from bottom to top; the upper surface of the lithium niobate single crystal thin film layer is etched to form a first curved waveguide, a second straight waveguide, a second curved waveguide, a third straight waveguide, a first 1:2 type Y waveguide, a fourth straight waveguide, a second 1:2 type Y waveguide, a fifth straight waveguide, a sixth straight waveguide, a 2:1 type Y waveguide, a seventh straight waveguide and an eighth straight waveguide; the silicon dioxide oxide layer and the lithium niobate single crystal thin film layer are etched together to form a sensitive unit;

[0010] One end of the sensitive unit is connected to the wide-spectrum light source through an optical isolator and a mode spot converter, and the other end of the sensitive unit is connected to the beam combining end of the first 1:2 type Y waveguide through an FP cavity, a first curved waveguide, a second straight waveguide, a second curved waveguide and a third straight waveguide in sequence, and an upper electrode and a lower electrode are respectively arranged on the upper surfaces of the lithium niobate single crystal thin film layers on both sides of the FP cavity; the first branch end of the first 1:2 type Y waveguide is connected to the first optical power meter through the eighth straight waveguide; the second branch end of the first 1:2 type Y waveguide is connected to the beam combining end of the second 1:2 type Y waveguide through the fourth straight waveguide, and the first branch end of the second 1:2 type Y waveguide is connected to the beam combining end of the second 1:2 type Y waveguide through the sixth straight waveguide. The first straight waveguide is connected to the first branch end of the 2:1 type Y waveguide, the second branch end of the second 1:2 type Y waveguide is connected to the second branch end of the 2:1 type Y waveguide through the fifth straight waveguide, the sixth straight waveguide and the fifth straight waveguide have different waveguide lengths and are arranged in parallel, an asymmetric Mach-Zehnder interferometer is formed by the second 1:2 type Y waveguide, the fifth straight waveguide, the sixth straight waveguide and the 2:1 type Y waveguide, the beam combining end of the 2:1 type Y waveguide is connected to the second optical power meter through the seventh straight waveguide, the first optical power meter and the second optical power meter are both connected to a demodulation feedback circuit, and the demodulation feedback circuit is also electrically connected to the upper electrode and the lower electrode respectively.

[0011] The sensitive unit comprises a serpentine cantilever beam, a mass block, a first annular waveguide, a second annular waveguide, a first straight waveguide and a micro-elliptical disk;

[0012] The upper surface of the lithium niobate single crystal film layer is etched to form a first straight waveguide, one end of the first straight waveguide is connected to the optical isolator, and the other end of the first straight waveguide is connected to the FP cavity. The silicon dioxide oxide layer and the lithium niobate single crystal film layer on one side of the first straight waveguide are etched together to form a serpentine cantilever beam and a mass block. The two sides of the mass block are respectively connected to the corresponding serpentine cantilever beams. The serpentine cantilever beam is used to support the mass block. The mass block and the bottom of the serpentine cantilever beam are suspended in the air, and the mass block and the first straight waveguide are arranged at intervals. The upper surface of the lithium niobate single crystal film layer in the middle of the mass block is etched to form a first annular waveguide. A micro-elliptical disk is arranged in the inner circle of the first annular waveguide. The silicon dioxide oxide layer and the lithium niobate single crystal film layer between the micro-elliptical disk and the mass block are both etched away, so that the micro-elliptical disk and the mass block are arranged at intervals, and the bottom of the micro-elliptical disk is not suspended in the air; the centers of the first annular waveguide, the second annular waveguide and the micro-elliptical disk are on a straight line, and the major axis of the micro-elliptical disk is on the straight line;

[0013] The upper surface of the lithium niobate single crystal thin film layer near one end of the lower electrode on one side of the first straight waveguide is etched to form a second annular waveguide, the second annular waveguide is spaced apart from the first straight waveguide, and the second annular waveguide is spaced apart from the serpentine cantilever beam closest to one end of the lower electrode.

[0014] The light of the broadband light source enters the first straight waveguide after passing through the mode spot converter and the optical isolator, and the light wave in the first straight waveguide that meets the resonance condition of the first annular waveguide is coupled into the first annular waveguide to resonate, and then coupled into the first straight waveguide; then the light wave in the first straight waveguide that meets the resonance condition of the second annular waveguide is coupled from the first straight waveguide into the second annular waveguide to resonate, and then the light wave passes through the first straight waveguide and enters the FP cavity for narrowband filtering, and the light enters the first curved waveguide from the output end of the FP cavity, and then passes through the second straight waveguide, the second curved waveguide and the third straight waveguide in sequence. The light enters the beam combining end of the first 1:2 type Y waveguide after passing through the waveguide; the first branch end of the first 1:2 type Y waveguide is connected to the first optical power meter through the eighth straight waveguide for real-time monitoring of the optical power; the light is transmitted from the second branch end of the first 1:2 type Y waveguide to the second 1:2 type Y waveguide through the fourth straight waveguide; the light is transmitted from the two branch ends of the second 1:2 type Y waveguide to the fifth straight waveguide and the sixth straight waveguide respectively, and then the light enters the beam combining end of the 2:1 type Y waveguide through the seventh straight waveguide for analyzing the optical wavelength; the signals of the first optical power meter and the second optical power meter are transmitted to the demodulation feedback circuit.

[0015] The inner diameter of the first ring waveguide is 2-4 um larger than the inner diameter of the second ring waveguide.

[0016] The distance between the center of the micro-elliptical disk and the center of the first annular waveguide is 150-220 nm.

[0017] The two branch ends of the second 1:2 type Y waveguide or 2:1 type Y waveguide are of unequal lengths.

[0018] The broad spectrum light source adopts SLD light source or ASE light source.

[0019] The beneficial effects of the present invention are:

[0020] The optical accelerometer chip based on the cascaded double-ring resonant cavity vernier effect proposed by the present invention greatly reduces the volume of the acceleration sensor compared to discrete components; it has high precision, simple manufacturing process, resistance to electromagnetic interference, high reliability and low production cost.

[0021] The present invention uses a lithium niobate ridge waveguide made by dry etching to realize light transmission; the positions of all components are determined by electron beam lithography and dry etching processes, so the relative position error is extremely small.

[0022] The first optical power meter of the present invention detects the intensity of the light field after filtering through the FP cavity, inputs it into a demodulation feedback circuit, and uses it as a normalized optical power signal. The second optical power meter records the intensity of the light after filtering through the FP cavity and then interfering through an asymmetric Mach-Zehnder interferometer, and inputs it into a demodulation feedback circuit to demodulate the wavelength.

[0023] The demodulation feedback circuit of the present invention changes the electrode voltage according to the signals of the first optical power meter and the second optical power meter, thereby changing the filtering range of the FP cavity and tracking the resonant wavelength after the acceleration input in real time. The filtering range of the FP cavity moves with the movement of the resonant wavelength, thereby improving the accuracy, linearity and range of acceleration measurement.

[0024] The present invention adopts the vernier effect based on the cascade resonant cavity to amplify the resonant wavelength offset of the first annular waveguide, so the detection accuracy is high. When there is an x-direction acceleration input from the outside, the mass block of the sensitive unit structure generates an x-direction translation displacement, driving the first annular waveguide to translate at the same time, changing the spacing between the first annular waveguide and the micro-elliptical disk, thereby causing the resonant wavelength of the first annular waveguide to shift. This causes the signals of the first optical power meter and the second optical power meter to change, and the wavelength offset direction and offset of the first annular waveguide can be demodulated through the processing of the demodulation feedback circuit, thereby measuring the direction and magnitude of the acceleration. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 It is a schematic diagram of the structure of the sensitive unit of the present invention;

[0027] In the figure: 1, broadband light source, 2, spot converter, 3, optical isolator, 4, sensitive unit, 5, upper electrode, 6, lower electrode, 7, FP cavity, 8, first curved waveguide, 9, second straight waveguide, 10, second curved waveguide, 11, third straight waveguide, 12, first 1:2 type Y waveguide, 13, fourth straight waveguide, 14, second 1:2 type Y waveguide, 15, fifth straight waveguide, 16, sixth straight waveguide, 17, 2: Type 1 Y waveguide, 18. Seventh straight waveguide, 19. Eighth straight waveguide, 20. First optical power meter, 21. Second optical power meter, 22. Demodulation feedback circuit, 23. Lithium niobate single crystal thin film layer, 24. Packaging shell, 42. Serpentine cantilever beam, 43. Mass block, 44. First ring waveguide, 45. Second ring waveguide, 46. First straight waveguide, 47. Micro-elliptical disk, 48. Silicon dioxide oxide layer, 49. Silicon substrate. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] In a specific implementation, the optical accelerometer chip is packaged in a packaging shell 24, which is characterized in that: Figure 1 As shown, the present invention includes a broadband light source 1, a pattern spot converter 2, an optical isolator 3, a sensitive unit 4, an upper electrode 5, a lower electrode 6, an FP cavity 7, a first curved waveguide 8, a second straight waveguide 9, a second curved waveguide 10, a third straight waveguide 11, a first 1:2 type Y waveguide 12, a fourth straight waveguide 13, a second 1:2 type Y waveguide 14, a fifth straight waveguide 15, a sixth straight waveguide 16, a 2:1 type Y waveguide 17, a seventh straight waveguide 18, an eighth straight waveguide 19, a first optical power meter 20, a second optical power meter 21, a demodulation feedback circuit 22, a lithium niobate single crystal thin film layer 23, a silicon dioxide oxide layer 48 and a silicon substrate 49;

[0030] The silicon substrate 49, the silicon dioxide oxide layer 48 and the lithium niobate single crystal thin film layer 23 are stacked in sequence from bottom to top, and the upper surface of the lithium niobate single crystal thin film layer 23 is etched to form a first curved waveguide 8, a second straight waveguide 9, a second curved waveguide 10, a third straight waveguide 11, a first 1:2 type Y waveguide 12, a fourth straight waveguide 13, a second 1:2 type Y waveguide 14, a fifth straight waveguide 15, a sixth straight waveguide 16, a 2:1 type Y waveguide 17, a seventh straight waveguide 18 and an eighth straight waveguide 19; the silicon substrate 49, the silicon dioxide oxide layer 48 and the lithium niobate single crystal thin film layer 23 are etched together to form a sensitive unit 4;

[0031] One end of the sensitive unit 4 is connected to the wide-spectrum light source 1 through the optical isolator 3 and the mode spot converter 2, and the other end of the sensitive unit 4 is connected to the beam combining end of the first 1:2 type Y waveguide 12 through the FP cavity 7, the first curved waveguide 8, the second straight waveguide 9, the second curved waveguide 10 and the third straight waveguide 11 in sequence. The upper surfaces of the lithium niobate single crystal thin film layers 23 on both sides of the FP cavity 7 are respectively provided with an upper electrode 5 and a lower electrode 6, and the upper electrode 5 and the lower electrode 6 are symmetrically distributed about the FP cavity 7; the first branch end of the first 1:2 type Y waveguide 12 is connected to the first optical power meter 20 through the eighth straight waveguide 19; the second branch end of the first 1:2 type Y waveguide 12 is connected to the beam combining end of the second 1:2 type Y waveguide 14 through the fourth straight waveguide 13. The first branch end of the second 1:2 type Y waveguide 14 is connected to the first branch end of the 2:1 type Y waveguide 17 through the sixth straight waveguide 16, and the second branch end of the second 1:2 type Y waveguide 14 is connected to the second branch end of the 2:1 type Y waveguide 17 through the fifth straight waveguide 15. The waveguide lengths of the sixth straight waveguide 16 and the fifth straight waveguide 15 are different, and the sixth straight waveguide 16 and the fifth straight waveguide 15 are arranged in parallel and spaced apart. Specifically, the fourth straight waveguide 13 and the seventh straight waveguide 18 are collinear, and the sixth straight waveguide 16 and the fifth straight waveguide 15 are parallel to the straight line where the fourth straight waveguide 13 and the seventh straight waveguide 18 are located. The two branch ends of the second 1:2 type Y waveguide 14 or the 2:1 type Y waveguide 17 are not of equal length. The splitting ratios of the first 1:2 type Y waveguide 12 and the second 1:2 type Y waveguide 14 are both 3dB. An asymmetric Mach-Zehnder interferometer is formed by the second 1:2 type Y waveguide 14, the fifth straight waveguide 15, the sixth straight waveguide 16 and the 2:1 type Y waveguide 17. The beam combining end of the 2:1 type Y waveguide 17 is connected to the second optical power meter 21 via the seventh straight waveguide 18. The first optical power meter 20 and the second optical power meter 21 are both connected to the demodulation feedback circuit 22, and the demodulation feedback circuit 22 is also electrically connected to the lower electrode 6.

[0032] The FP cavity 7 is obtained in the following manner: the upper surface of the lithium niobate single crystal thin film layer 23 is etched to form an FP waveguide, two end faces of the FP waveguide are respectively inscribed with a femtosecond laser, and two anti-reflection films are formed after the refractive index of the lithium niobate is changed, so that the FP waveguide constitutes the FP cavity 7. The two ends of the FP cavity 7 are respectively connected to the other end of the first straight waveguide 46 and the first curved waveguide 8.

[0033] The broadband light source 1, the spot converter 2, the optical isolator 3, the first optical power meter 20, the second optical power meter 21 and the demodulation feedback circuit 22 are all located on the upper surface of the lithium niobate single crystal thin film layer 23. The broadband light source has a spectral width of 40nm and a central wavelength of 1550nm. The broadband light source 1 adopts an SLD light source or an ASE light source.

[0034] like Figure 2As shown, the sensitive unit 4 includes a serpentine cantilever beam 42, a mass block 43, a first annular waveguide 44, a second annular waveguide 45, a first straight waveguide 46 and a micro-elliptical disk 47;

[0035] The upper surface of the lithium niobate single crystal thin film layer 23 is etched to form a first straight waveguide 46, one end of the first straight waveguide 46 is connected to the optical isolator 3, and the other end of the first straight waveguide 46 is connected to the FP cavity 7. The silicon substrate 49, the silicon dioxide oxide layer 48 and the lithium niobate single crystal thin film layer 23 on one side of the first straight waveguide 46 are etched together to form a serpentine cantilever beam 42 and a mass block 43. The mass block 43 is suspended as a whole, and the two sides of the mass block 43 are respectively connected to the corresponding serpentine cantilever beam 42. The serpentine cantilever beam 42 is connected to the middle part of the mass block 43. The serpentine cantilever beams 42 on both sides of the mass block 43 are arranged symmetrically. The serpentine cantilever beam 42 is used to stably support the mass block 43. The mass block 43 and the bottom of the serpentine cantilever beam 42 are suspended in the air. Specifically, the mass block 43 and the serpentine cantilever beam 42 are in the lithium niobate single crystal thin film layer 23. The silicon dioxide oxide layer 48 below the mass block 43 and the serpentine cantilever beam 42 is corroded, so that the mass block 43 and the serpentine cantilever beam 42 are suspended in the air. The mass block 43 and the first straight waveguide 46 are arranged at intervals, and the upper surface of the lithium niobate single crystal film layer 23 in the middle of the mass block 43 is etched to form a first annular waveguide 44. A micro-elliptical disk 47 is arranged in the inner circle of the first annular waveguide 44. The silicon dioxide oxide layer 48 and the lithium niobate single crystal film layer 23 between the micro-elliptical disk 47 and the mass block 43 are all etched away, so that the micro-elliptical disk 47 and the mass block 43 are arranged at intervals, and the bottom of the micro-elliptical disk 47 is not suspended, that is, half of the long axis of the micro-elliptical disk 47 is smaller than the inner diameter of the first annular waveguide 44, and the silicon dioxide oxide layer 48 below the micro-elliptical disk 47 is not etched away. The centers of the first annular waveguide 44, the second annular waveguide 45 and the micro-elliptical disk 47 are on a straight line and the long axis of the micro-elliptical disk 47 is on the straight line; the straight line where the centers of the first annular waveguide 44, the second annular waveguide 45 and the micro-elliptical disk 47 are located is the x-axis direction, and the y-axis direction is perpendicular to the x-axis direction and is on the plane of the chip. The distance between the center of the micro-elliptical disk 47 and the center of the first annular waveguide 44 is 150-220 nm, that is, the center of the micro-elliptical disk 47 is offset by 150-220 nm relative to the center of the first annular waveguide 44 in the positive or negative direction of the x-axis. In the embodiment, the center is offset by 200 nm.

[0036] The upper surface of the lithium niobate single crystal thin film layer 23 near one end of the lower electrode 6 on one side of the first straight waveguide 46 is etched to form a second annular waveguide 45, the serpentine cantilever beam 42, the mass block 43, the first annular waveguide 44, the second annular waveguide 45, and the micro-elliptical disk 47 are all located on the same side of the first straight waveguide 46, the second annular waveguide 45 is arranged at intervals with the first straight waveguide 46, and the second annular waveguide 45 is arranged at intervals with the serpentine cantilever beam 42 closest to one end of the lower electrode 6. The first annular waveguide 44 serves as a first-stage annular resonant cavity, and the second annular waveguide 45 serves as a second-stage annular resonant cavity.

[0037] The inner diameter of the first annular waveguide 44 is 2-4 um larger than the inner diameter of the second annular waveguide 45. In a specific implementation, the inner diameter of the first annular waveguide 44 is 3 um larger than the inner diameter of the second annular waveguide 45. The transmission spectrum of the first annular waveguide 44 is a first transmission valley with equal frequency intervals, and this frequency interval is the free spectrum range FSR1 of the first annular waveguide 44, and the resonant frequency of the first annular waveguide 44 corresponds to the first transmission valley; the transmission spectrum of the second annular waveguide 45 is a second transmission valley with equal frequency intervals, and this frequency interval is the free spectrum range FSR2 of the second annular waveguide 45, and the resonant frequency of the second annular waveguide 45 corresponds to the second transmission valley. The free spectrum range FSR1 of the first annular waveguide 44 is slightly smaller than the free spectrum range of the second ring resonant cavity, and the cascade effect of the two resonant cavities is used to amplify the offset of the resonant frequency of the first annular waveguide 44.

[0038] The light from the wide spectrum light source 1 enters the first straight waveguide 46 after passing through the mode spot converter 2 and the optical isolator 3. Due to the effect of the evanescent wave, the light wave of the frequency that meets the resonance condition of the first ring waveguide 44 in the first straight waveguide 46 is coupled into the first ring waveguide 44 to resonate, and then coupled into the first straight waveguide 46; then the light wave of the frequency that meets the resonance condition of the second ring waveguide 45 in the first straight waveguide 46 is coupled from the first straight waveguide 46 into the second ring waveguide 45 to resonate, and then the light wave passes through the first straight waveguide 46 and enters the FP cavity 7 for narrowband filtering, and the light enters the first curved waveguide 8 from the output end of the FP cavity 7, and then passes through the second straight waveguide 9, the second curved waveguide 10 and the third straight waveguide 8 in sequence. The light enters the beam combining end of the first 1:2 type Y waveguide 12 after the light enters the beam combining end of the first 1:2 type Y waveguide 12; the first branch end of the first 1:2 type Y waveguide 12 is connected to the first optical power meter 20 through the eighth straight waveguide 19 for real-time monitoring of the optical power; the light is transmitted from the second branch end of the first 1:2 type Y waveguide 12 to the second 1:2 type Y waveguide 14 through the fourth straight waveguide 13; the light is transmitted from the two branch ends of the second 1:2 type Y waveguide 14 to the fifth straight waveguide 15 and the sixth straight waveguide 16 respectively, and then the light enters the beam combining end of the 2:1 type Y waveguide 17 and is coupled into the second optical power meter 21 through the seventh straight waveguide 18 for analyzing the optical wavelength; the signals of the first optical power meter 20 and the second optical power meter 21 are transmitted to the demodulation feedback circuit 22. The demodulation feedback circuit 22 analyzes the resonant wavelength offset, and then analyzes the magnitude and direction of the acceleration; the demodulation feedback circuit 22 changes the transmission wavelength range of the FP cavity by controlling the voltage between the upper electrode 5 and the lower electrode 6, and then tracks the resonance valley in real time. The filtering range of the FP cavity moves with the movement of the resonant wavelength, thereby improving the accuracy, linearity and range of acceleration measurement.

[0039] In a specific embodiment, the overall size of the monolithic integrated optical accelerometer is 3×3×0.2~6×6×0.3 cubic millimeters, the upper surface area of ​​the mass block 43 is 0.5×1~1×2 square millimeters, the thickness is 0.3~0.4 microns, the inner radius of the first ring waveguide 44 is 7um~9um, the outer radius is 8-10um, the inner radius of the second ring waveguide 45 is 10um~12um, the outer radius is 11-13um, the thickness of the silicon substrate 49 is 0.1~0.2 mm; the long semi-axis of the micro-elliptical disk 47 is 6-6.5um, and the short semi-axis is 5-5.5um. The thickness of the silicon dioxide oxide layer 48 is 1~5 microns, and the thickness of the lithium niobate single crystal film 23 is 0.4~1 micron. The wide spectrum light source 1 adopts an SLD light source or an ASE light source. The first 1:2 type Y waveguide 12, the second 1:2 type Y waveguide 14, and the 2:1 type Y waveguide 17 are ridge waveguides, with a waveguide width of 0.5 to 1.5 microns and a ridge height of 0.2 to 0.5 microns. The distance between the upper electrode 5 and the lower electrode 6 is 1.3 to 10 microns.

[0040] In this example, the broadband light source 1 adopts an SLD light source with a central wavelength of 1550 nanometers and an average optical power output of 800 microwatts. The thickness of the lithium niobate single crystal film 23 is 0.6 microns, the thickness of the silicon dioxide oxide layer 48 is 2 microns, and the thickness of the silicon substrate 49 is 0.1 mm. The first 1:2 type Y waveguide 12, the second 1:2 type Y waveguide 14, and the 2:1 type Y waveguide 17 are ridge waveguides with a waveguide width of 1 micron and a ridge height of 0.3 microns. The spacing between the electrode and the ridge waveguide is 2 microns, and the lengths of the upper electrode 5 and the lower electrode 6 are both 2 mm. The upper surface area of ​​the mass block 43 is 0.5×1 square millimeter, the thickness is 0.3 microns, the inner radius of the first annular waveguide 44 is 7um, the outer radius is 8um, the inner radius of the second annular waveguide 48 is 10um, and the outer radius is 11um. The width of the serpentine cantilever beam 42 is 0.4um and the height is 0.3um.

[0041] like Figure 2 As shown, when the optical accelerometer is subjected to acceleration in the x direction, the mass block 43 will deviate in the x direction, thereby driving the first annular waveguide 44 to deviate in the x direction, causing the distance between the first annular waveguide 44 and the micro-elliptical disk 47 to change, causing the resonant wavelength of the first annular waveguide 44 to deviate. The vernier effect formed by the two cascaded annular resonators is used to amplify the resonant wavelength offset of the first annular waveguide 44. After narrow-band filtering through the FP cavity, the light is divided into two beams through the first 1:2 type Y waveguide 12. One beam is received by the first optical power meter 20, carrying intensity information, and the other beam passes through the asymmetric Mach-Zehnder interferometer composed of the fifth straight waveguide 15 and the sixth straight waveguide 16, and is received by the second optical power meter 21, carrying wavelength information. The signals of the two power meters are transmitted to the demodulation feedback circuit 22, and the resonant wavelength offset of the first annular waveguide 44 is demodulated, and then the direction and magnitude of the acceleration are demodulated. The demodulation feedback circuit 22 changes the transmission wavelength range of the FP cavity by controlling the voltage between the upper electrode 5 and the lower electrode 6, thereby tracking the resonant wavelength in real time. The filtering range of the FP cavity moves with the movement of the resonant wavelength, thereby improving the accuracy, linearity and range of acceleration measurement.

Claims

1. An optical accelerometer chip based on the vernier effect of a cascaded double-ring resonant cavity, characterized in that: The silicon substrate, the silicon dioxide oxide layer and the lithium niobate single crystal thin film layer are stacked in sequence from bottom to top, and the silicon dioxide oxide layer and the lithium niobate single crystal thin film layer are etched together to form a sensitive unit; the sensitive unit includes a serpentine cantilever beam, a mass block, a first annular waveguide, a second annular waveguide, a first straight waveguide and a micro-elliptical disk; The upper surface of the lithium niobate single crystal film layer is etched to form a first straight waveguide, one end of the first straight waveguide is connected to the optical isolator, and the other end of the first straight waveguide is connected to the FP cavity. The silicon dioxide oxide layer and the lithium niobate single crystal film layer on one side of the first straight waveguide are etched together to form a serpentine cantilever beam and a mass block. The two sides of the mass block are respectively connected to the corresponding serpentine cantilever beams. The serpentine cantilever beam is used to support the mass block. The mass block and the bottom of the serpentine cantilever beam are suspended in the air, and the mass block and the first straight waveguide are arranged at intervals. The upper surface of the lithium niobate single crystal film layer in the middle of the mass block is etched to form a first annular waveguide. A micro-elliptical disk is arranged in the inner circle of the first annular waveguide. The silicon dioxide oxide layer and the lithium niobate single crystal film layer between the micro-elliptical disk and the mass block are both etched away, so that the micro-elliptical disk and the mass block are arranged at intervals, and the bottom of the micro-elliptical disk is not suspended in the air; the centers of the first annular waveguide, the second annular waveguide and the micro-elliptical disk are on a straight line, and the major axis of the micro-elliptical disk is on the straight line; A second annular waveguide is formed by etching the upper surface of the lithium niobate single crystal thin film layer near one end of the lower electrode on one side of the first straight waveguide, the second annular waveguide is arranged at an interval with the first straight waveguide, and the second annular waveguide is arranged at an interval with the serpentine cantilever beam closest to one end of the lower electrode; The distance between the center of the micro-elliptical disk and the center of the first annular waveguide is 150-220 nm.

2. The optical accelerometer chip based on the cascaded double-ring resonant cavity vernier effect according to claim 1, characterized in that: The upper surface of the lithium niobate single crystal thin film layer is etched to form a first curved waveguide, a second straight waveguide, a second curved waveguide, a third straight waveguide, a first 1:2 type Y waveguide, a fourth straight waveguide, a second 1:2 type Y waveguide, a fifth straight waveguide, a sixth straight waveguide, a 2:1 type Y waveguide, a seventh straight waveguide and an eighth straight waveguide; One end of the sensitive unit is connected to the wide-spectrum light source through an optical isolator and a mode spot converter, and the other end of the sensitive unit is connected to the beam combining end of the first 1:2 type Y waveguide through an FP cavity, a first curved waveguide, a second straight waveguide, a second curved waveguide and a third straight waveguide in sequence, and an upper electrode and a lower electrode are respectively arranged on the upper surfaces of the lithium niobate single crystal thin film layers on both sides of the FP cavity; the first branch end of the first 1:2 type Y waveguide is connected to the first optical power meter through the eighth straight waveguide; the second branch end of the first 1:2 type Y waveguide is connected to the beam combining end of the second 1:2 type Y waveguide through the fourth straight waveguide, and the first branch end of the second 1:2 type Y waveguide is connected to the beam combining end of the second 1:2 type Y waveguide through the sixth straight waveguide. The first straight waveguide is connected to the first branch end of the 2:1 type Y waveguide, the second branch end of the second 1:2 type Y waveguide is connected to the second branch end of the 2:1 type Y waveguide through the fifth straight waveguide, the sixth straight waveguide and the fifth straight waveguide have different waveguide lengths and are arranged in parallel, an asymmetric Mach-Zehnder interferometer is formed by the second 1:2 type Y waveguide, the fifth straight waveguide, the sixth straight waveguide and the 2:1 type Y waveguide, the beam combining end of the 2:1 type Y waveguide is connected to the second optical power meter through the seventh straight waveguide, the first optical power meter and the second optical power meter are both connected to a demodulation feedback circuit, and the demodulation feedback circuit is also electrically connected to the upper electrode and the lower electrode respectively.

3. The optical accelerometer chip based on the cascaded double-ring resonant cavity vernier effect according to claim 2, characterized in that: The light of the broadband light source enters the first straight waveguide after passing through the mode spot converter and the optical isolator. The light wave in the first straight waveguide that meets the resonance condition of the first annular waveguide is coupled into the first annular waveguide to resonate, and then coupled into the first straight waveguide; then the light wave in the first straight waveguide that meets the resonance condition of the second annular waveguide is coupled from the first straight waveguide into the second annular waveguide to resonate, and then the light wave passes through the first straight waveguide and enters the FP cavity for narrowband filtering, and the light enters the first curved waveguide from the output end of the FP cavity, and then passes through the second straight waveguide, the second curved waveguide and the third straight waveguide in sequence before entering The first 1:2 type Y waveguide is connected to the beam combining end; the first branch end of the first 1:2 type Y waveguide is connected to the first optical power meter through the eighth straight waveguide for real-time monitoring of optical power; light is transmitted from the second branch end of the first 1:2 type Y waveguide to the second 1:2 type Y waveguide via the fourth straight waveguide; light is transmitted from the two branch ends of the second 1:2 type Y waveguide to the fifth straight waveguide and the sixth straight waveguide respectively, and then the light enters the beam combining end of the 2:1 type Y waveguide and is coupled into the second optical power meter via the seventh straight waveguide for analyzing the optical wavelength; the signals of the first optical power meter and the second optical power meter are transmitted to the demodulation feedback circuit.

4. The optical accelerometer chip based on the cascaded double-ring resonant cavity vernier effect according to claim 1, characterized in that: The inner diameter of the first ring waveguide is 2-4 um larger than the inner diameter of the second ring waveguide.

5. The optical accelerometer chip based on the cascaded double-ring resonant cavity vernier effect according to claim 2, characterized in that: The two branch ends of the second 1:2 type Y waveguide or 2:1 type Y waveguide are of unequal lengths.

6. The optical accelerometer chip based on the cascaded double-ring resonant cavity vernier effect according to claim 2, characterized in that: The broad spectrum light source adopts SLD light source or ASE light source.

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