A precision-controlled optical micro-electromechanical structure

Abstract

The present invention provides an optical micro-electromechanical structure with controllable precision modulation, comprising a suspended mass block, a plurality of suspended tethers, a photonic crystal microcavity, a suspended optical waveguide, a first connecting tether, a suspended beam, a second connecting tether, a rigid block, and a capacitor, wherein the first capacitor end of the capacitor is fixed to the suspended beam, and the second capacitor end is fixed to the rigid block. The present invention uses a capacitance modulation method to modulate the optical microcavity, which can not only calibrate the optical microcavity produced by the photolithography process so that the actual resonance wavelength of the photonic crystal microcavity is perfectly matched with the designed working wavelength, but also adjust the offset of the resonance wavelength caused by changes in the working environment, thereby improving the measurement accuracy. In the present invention, the capacitor only modulates the gap of the photonic crystal microcavity and does not affect the mechanical properties of the mass block, that is, it only modulates the optical properties, thereby avoiding modulation crosstalk. In the present invention, the optical waveguide is connected and fixed to one end of the optical microcavity, and has good optical coupling stability and overall system stability.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-electromechanical systems, and relates to an optical micro-electromechanical structure with controllable precision modulation. Background Art

[0002] Inertial sensing units (IMUs), including gyroscopes and accelerometers, can measure an object's angular acceleration and acceleration, playing a vital role in object positioning and motion posture monitoring. With the development of the Internet of Things, the application of wearable devices, and the gradual popularization of 5G technology, IMUs will be widely used in fields such as autonomous driving, drones, intelligent robots, and virtual / augmented reality. The diverse and complex application scenarios of the future will place stringent requirements on IMUs for high precision and miniaturization. Currently, civilian IMUs are primarily based on microelectromechanical systems (MEMS), which combine silicon-based microelectronics and micromachining technologies to achieve the advantages of small size, low cost, and large-scale production. However, traditional MEMS inertial sensing units have low accuracy and cannot meet the future market demand for high-precision inertial sensors.

[0003] With the recent development of silicon-based photonics, optical microelectromechanical systems (Opto-MEMS) combine the advantages of optical precision measurement with the low cost and miniaturization of MEMS, and are considered to fill the gap in the next generation of low-cost, high-performance miniaturized inertial measurement units. Currently, measurement units based on optomechanical coupling, including accelerometers and gyroscopes, have attracted widespread attention. However, there are still many shortcomings in the calibration and modulation of the core sensing units.

[0004] For common optical micro-electromechanical system measurement units, the usual practice is to construct an optical microcavity, such as a Fabry-Perot optical microcavity or a photonic crystal microcavity to achieve this. Among them, the resonant wavelength of the designed optical microcavity plays a vital role in the process of optical-mechanical signal conversion. However, optical devices are very sensitive to size. Due to the limitations of processing methods, the manufactured devices will have a certain degree of deviation in geometric scale and material properties, resulting in the optical microcavity not necessarily meeting the originally designed resonant wavelength. At the same time, due to the influence of the working environment (such as temperature, etc.), the resonant wavelength of the optical microcavity will have a certain drift, which greatly limits the application scenarios of the device. Therefore, it is necessary to actively correct and adjust the resonant wavelength of the optical microcavity.

[0005] Therefore, how to provide an optical microelectromechanical structure that can actively correct and adjust the resonant wavelength of an optical microcavity so that the optical microcavity can efficiently couple with the incident light wave has become an important technical problem that needs to be solved urgently by those skilled in the art.

[0006] It should be noted that the above introduction to the technical background is merely intended to provide a clear and complete description of the technical solutions of this application and facilitate understanding by those skilled in the art. Simply because these solutions are described in the background technology section of this application, it should not be assumed that the above technical solutions are well known to those skilled in the art. Summary of the Invention

[0007] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide an optical microelectromechanical structure with controllable precision modulation, which is used to solve at least one of the following problems: the optical microcavity of the existing optical microelectromechanical structure is limited by the processing method, so that the actual resonance wavelength does not conform to the originally designed resonance wavelength; the resonance wavelength of the optical microcavity is easily affected by the working environment and drifts; and the device has low flexibility.

[0008] To achieve the above and other related objectives, the present invention provides an optical micro-electromechanical structure with controllable precision modulation, comprising:

[0009] Suspended mass;

[0010] a plurality of suspension tethers, distributed on both sides of the suspended mass in the X direction and connected to the suspended mass;

[0011] a photonic crystal microcavity located on one side of the suspended mass in the Y direction, wherein the Y direction is perpendicular to the X direction, and the photonic crystal microcavity includes a first suspended photonic crystal and a second suspended photonic crystal, wherein the first suspended photonic crystal is fixed to the suspended mass, and the second suspended photonic crystal is located on a side of the first suspended photonic crystal away from the suspended mass and spaced apart from the first suspended photonic crystal;

[0012] a suspended optical waveguide, located on a side of the photonic crystal microcavity away from the suspended mass block and spaced apart from the photonic crystal microcavity by a preset distance;

[0013] a first connecting tether connected between the second suspended photonic crystal and the suspended optical waveguide;

[0014] a suspension beam, located on a side of the suspension optical waveguide away from the photonic crystal microcavity and spaced apart from the suspension optical waveguide;

[0015] a second connecting tie, connected between the suspended optical waveguide and the suspended beam;

[0016] a rigid block, located on a side of the suspension beam away from the suspension optical waveguide and spaced apart from the suspension beam;

[0017] The capacitor includes a first capacitor end and a second capacitor end spaced apart in the Y direction, wherein the first capacitor end is fixed to the suspension beam, and the second capacitor end is fixed to the rigid block.

[0018] Optionally, the suspended optical waveguide includes a crossbeam, a first connecting block, and a second connecting block. The crossbeam extends along the X direction. The first connecting block and the second connecting block are both connected to a side of the crossbeam away from the photonic crystal microcavity. The vertical projection of the first connecting tether on the XZ plane is located within the vertical projection range of the first connecting block on the XZ plane. The end of the second connecting tether away from the suspended beam is connected to the second connecting block.

[0019] Optionally, a vertical projection of the first connecting block on the XY plane is trapezoidal, and a vertical projection of the second connecting block on the XY plane is trapezoidal.

[0020] Optionally, the first capacitor end is located on the upper surface of the suspension beam, and the second capacitor end is located on the upper surface of the rigid block.

[0021] Optionally, the optical microelectromechanical structure includes a supporting layer and a functional layer located on the supporting layer, the suspended mass block, the suspended tether, the first suspended photonic crystal, the second suspended photonic crystal, the suspended optical waveguide, the suspended beam, the first connecting tether and the second connecting tether are all formed based on the functional layer, and the rigid block is formed based on the supporting layer and the functional layer.

[0022] Optionally, the support layer includes a silicon layer, and the functional layer includes a silicon nitride layer; or the support layer includes a silicon base layer and a silicon oxide layer located on the silicon base layer, and the functional layer includes a silicon top layer.

[0023] Optionally, the optical micro-electromechanical structure is applied to a gyroscope or an accelerometer.

[0024] Optionally, the capacitor is a parallel plate capacitor.

[0025] Optionally, the thickness of the first capacitor terminal is in a range of 50 nanometers to 300 nanometers, the length along the X direction is in a range of 20 micrometers to 200 micrometers, and the width along the Y direction is in a range of 100 nanometers to 2 micrometers; the thickness of the second capacitor terminal is in a range of 50 nanometers to 300 nanometers, the length along the X direction is in a range of 20 micrometers to 200 micrometers, and the width along the Y direction is in a range of 100 nanometers to 2 micrometers.

[0026] Optionally, the capacitor is a comb-tooth capacitor, wherein the first capacitor end includes a first beam, the second capacitor end includes a second beam, the first beam and the second beam are spaced apart in the Y direction, a side of the first beam facing the second beam is connected to a plurality of first comb teeth, a side of the second beam facing the first beam is connected to a plurality of second comb teeth, and the plurality of first comb teeth and the plurality of second comb teeth are alternately arranged in the X direction and partially overlap in the Y direction.

[0027] Optionally, the number of the first comb teeth ranges from 5 to 100, the length along the Y direction ranges from 5 microns to 20 microns, and the width along the X direction ranges from 500 nanometers to 2 microns; the number of the second comb teeth ranges from 5 to 100, the length along the Y direction ranges from 5 microns to 20 microns, and the width along the X direction ranges from 500 nanometers to 2 microns; the gap width between adjacent first comb teeth and second comb teeth in the X direction ranges from 100 nanometers to 500 nanometers, the distance between the end of the first comb tooth and the second crossbeam in the Y direction ranges from 2 microns to 4 microns, and the distance between the end of the second comb tooth 302b and the first crossbeam in the Y direction ranges from 2 microns to 4 microns.

[0028] Optionally, the photonic crystal microcavity includes a defect region and a mirror region, and the mirror region is distributed on both sides of the defect region in the X direction, or the mirror region is distributed on both sides of the defect region in the X direction and both sides of the Y direction.

[0029] Optionally, the first suspended photonic crystal and the second suspended photonic crystal each include a plurality of air holes arranged in at least one row, wherein the row direction is the X direction, and the sizes of the plurality of air holes located in the defect area and arranged in the X direction form an arithmetic progression, gradually decreasing or increasing from the left and right sides to the middle, and the sizes of the plurality of air holes located in the mirror area are the same.

[0030] Optionally, the first suspended photonic crystal and the second suspended photonic crystal both include a plurality of air holes arranged in at least two rows, the plurality of air holes in the first suspended photonic crystal are arranged in a triangular array, and the plurality of air holes in the second suspended photonic crystal are arranged in a triangular array.

[0031] Optionally, the length of the suspended mass along the X direction ranges from 30 microns to 500 microns, and the width along the Y direction ranges from 10 microns to 300 microns; the length of the suspended tether along the X direction ranges from 50 microns to 2000 microns, and the width along the Y direction ranges from 50 nanometers to 400 nanometers; and the width of the suspended optical waveguide along the Y direction ranges from 400 nanometers to 2000 nanometers.

[0032] Optionally, the material of the first capacitor terminal includes one or more of gold, silver, aluminum and copper, and the material of the second capacitor terminal includes one or more of gold, silver, aluminum and copper.

[0033] As described above, the optical micro-electromechanical structure of the present invention uses a capacitance modulation method to modulate the optical microcavity of the optical micro-electromechanical structure, thereby achieving active tuning of its resonant wavelength, and can correct the optical microcavity produced by the photolithography process, reduce or eliminate the impact caused by the error of wafer photolithography production, so that the actual resonant wavelength of the photonic crystal microcavity is perfectly matched with the designed operating wavelength. In addition, the active tuning of the resonant wavelength of the photonic crystal microcavity by the capacitor can also compensate for the offset of the resonant wavelength caused by changes in the working environment (such as thermal expansion and contraction caused by temperature), thereby improving measurement accuracy. In the optical micro-electromechanical structure of the present invention, the capacitance modulation method can be parallel plate capacitance modulation or comb capacitance modulation, wherein the comb capacitance modulation method can achieve a larger adjustment of the photonic crystal microcavity gap, thereby achieving a larger adjustment of the resonant frequency, and can match a wider range of incident wavelengths, thereby being applicable to different operating wavelengths, and improving the adaptability and ease of use of the device. The manufacturing process of the optical micro-electromechanical structure of the present invention is simple and can be compatible with current silicon photonic processes. In the capacitance-tuned optical microelectromechanical structure of the present invention, the capacitor only modulates the gap of the photonic crystal microcavity without affecting the mechanical properties of the mass block. In other words, it only modulates the optical properties, thus avoiding modulation crosstalk. In the precision-controlled modulated optical microelectromechanical structure of the present invention, the optical waveguide is fixedly connected to one end of the optical microcavity, ensuring that when acceleration is applied, the optical waveguide and the optical microcavity do not undergo relative displacement, thereby improving the stability of the optical coupling and thus the overall stability of the system. The present invention can also selectively widen the optical waveguide connecting ligaments locally to form a trapezoidal structure, reducing the scattering rate of the connecting ligaments, thereby improving signal loss and improving the signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 FIG. 1 is an XY plane diagram of the optical micro-electromechanical structure with controllable precision modulation according to the present invention in the first embodiment.

[0035] Figure 2 The figure shows the YZ plane view of the precision controllable modulated optical micro-electromechanical structure in the first embodiment of the present invention.

[0036] Figure 3 Shown is a schematic diagram of a parallel plate capacitor.

[0037] Figure 4 The figure shows an XY plane diagram of the precision controllable modulated optical micro-electromechanical structure in the second embodiment of the present invention.

[0038] Figure 5Shown is a partially enlarged structural diagram of a comb capacitor.

[0039] Component number description

[0040] 1 Suspended mass

[0041] 2 Suspension tethers

[0042] 3 Photonic Crystal Microcavity

[0043] 301 The First Suspended Photonic Crystal

[0044] 302 Second Suspended Photonic Crystal

[0045] 4 Suspended optical waveguide

[0046] 5 First connecting strap

[0047] 6 Suspended beam

[0048] 7 Second connecting strap

[0049] 8 Rigid Block

[0050] 9. Capacitor

[0051] 901 First capacitor terminal

[0052] 901a First beam

[0053] 901b First comb tooth

[0054] 902 Second capacitor terminal

[0055] 902a Second beam

[0056] 902b Second comb tooth

[0057] M defect area

[0058] A Support layer

[0059] B functional layer DETAILED DESCRIPTION

[0060] Generally speaking, there are two ways to match the resonant wavelength of a fabricated photonic crystal microcavity with the wavelength of the input lightwave in the optical waveguide. The first is to use a continuously tunable laser light source to adjust the wavelength of the input lightwave so that it couples with the resonant wavelength of the photonic crystal microcavity. However, continuously tunable laser light sources are expensive and bulky, which cannot meet the diverse market demands and limits the popularity of the device. Therefore, the present invention adopts an alternative method, which matches the fixed-wavelength laser light source by adjusting the resonant wavelength of the photonic crystal microcavity. This can greatly reduce costs, reduce the size of the device, and improve product flexibility and user popularity.

[0061] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0062] See also Figures 1 to 5 It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0063] Example 1

[0064] This embodiment provides an optical micro-electromechanical structure with controllable modulation precision. Figure 1 , which shows an XY plane diagram of the optical microelectromechanical structure, including a suspended mass block 1, a plurality of suspended tethers 2, a photonic crystal microcavity 3, a suspended optical waveguide 4, a first connecting tether 5, a suspended beam 6, a second connecting tether 7, a rigid block 8, and a capacitor 9. The plurality of suspended tethers 2 are distributed on both sides of the suspended mass block 1 in the X direction and connected to the suspended mass block 1. The photonic crystal microcavity 3 is located on one side of the suspended mass block 1 in the Y direction, where the Y direction is perpendicular to the X direction. The photonic crystal microcavity 3 includes a first suspended photonic crystal 301 and a second suspended photonic crystal 302. The first suspended photonic crystal 301 is fixed to the suspended mass block 1, and the second suspended photonic crystal 302 is located on a side of the first suspended photonic crystal 301 away from the suspended mass block 1 and between the first suspended photonic crystal 301 and the suspended photonic crystal 302. The suspended optical waveguide 4 is located on a side of the photonic crystal microcavity 3 away from the suspended mass block 1 and is spaced apart from the photonic crystal microcavity 3 by a preset distance; the first connecting tether 5 is connected between the second suspended photonic crystal 302 and the suspended optical waveguide 4; the suspended beam 6 is located on a side of the suspended optical waveguide 4 away from the photonic crystal microcavity 3 and is spaced apart from the suspended optical waveguide 4; the second connecting tether 7 is connected between the suspended optical waveguide 4 and the suspended beam 6; the rigid block 8 is located on a side of the suspended beam 6 away from the suspended optical waveguide 4 and is spaced apart from the suspended beam 6; the capacitor 9 includes a first capacitor terminal 901 and a second capacitor terminal 902 spaced apart in the Y direction, the first capacitor terminal 901 is fixed to the suspended beam 6, and the second capacitor terminal 902 is fixed to the rigid block 8.

[0065] As an example, the suspended optical waveguide 4 includes a crossbeam 401, a first connecting block 402, and a second connecting block 403. The crossbeam 401 extends along the X-direction. The first connecting block 402 and the second connecting block 403 are both connected to the side of the crossbeam 401 away from the photonic crystal microcavity 3. The vertical projection of the first connecting ligament 5 on the XZ plane (the X, Y, and Z directions are mutually perpendicular) is within the vertical projection of the first connecting block 402 on the XZ plane. The end of the second connecting ligament 7 away from the suspended beam 6 is connected to the second connecting block 403. In other words, the suspended optical waveguide 4 is locally widened at the connection points with the first connecting ligament 5 and the second connecting ligament 7. This narrows the optical mode of the lightwave and confines it to the interior of the suspended optical waveguide 4, reducing scattering losses from the first connecting ligament 5 and the second connecting ligament 7, thereby improving signal loss and enhancing the signal-to-noise ratio.

[0066] As an example, depending on the operating wavelength, the width of the portion of the suspended optical waveguide 4 without the connecting block along the Y direction can range from 400 nanometers to 1000 nanometers, while the width of the portion with the connecting block along the Y direction can range from 1600 nanometers to 2400 nanometers. In this embodiment, the vertical projections of the first connecting block 402 and the second connecting block 403 on the XY plane are both trapezoidal.

[0067] As an example, the number of first connecting blocks 402 is the same as the number of first connecting ties 5, and they correspond one-to-one. In this embodiment, the second suspended photonic crystal 302 is connected to the suspended optical waveguide 4 via two first connecting ties 5. Accordingly, the number of first connecting blocks 402 is also two. In other embodiments, the number of first connecting ties 5 and first connecting ties 5 may be greater, and this should not unduly limit the scope of protection of the present invention.

[0068] As an example, the number of the second connecting blocks 403 and the second connecting ties 7 is multiple, wherein each second connecting block 403 can be connected to only one second connecting ties 7, or can be connected to multiple second connecting ties 7 at the same time, wherein, Figure 1 What is presented is the situation that each second connecting block 403 is connected to three second connecting ties 7.

[0069] The fabrication process of the precision-controlled modulated optical micro-electromechanical structure of this embodiment is simple and compatible with current silicon photonics technology. Figure 2 , which is a YZ plane diagram of the optical microelectromechanical structure (along Figure 1In this embodiment, the first capacitor terminal 901 is located on the upper surface of the suspended mass block 1, and the second capacitor terminal 902 is located on the upper surface of the rigid block 8.

[0070] As an example, the optical microelectromechanical structure includes a support layer A and a functional layer B located on the support layer. The suspended mass 1, the suspended tether 2, the first suspended photonic crystal 301, the second suspended photonic crystal 302, the first connecting tether 5, the suspended beam 6, the second connecting tether 7, and the suspended beam 6 are all formed based on the functional layer B. The rigid block 8 is formed based on the support layer A and the functional layer B. In this embodiment, the material of the first capacitor terminal 901 and the second capacitor terminal 902 includes, but is not limited to, one or more of gold, silver, aluminum, and copper, and can be deposited on the upper surface of the functional layer B by evaporation.

[0071] As an example, the optical micro-electromechanical structure may be established based on a silicon nitride / silicon platform, that is, the support layer A includes a silicon layer, and the functional layer B includes a silicon nitride layer.

[0072] As an example, the optical micro-electromechanical structure can also be established based on a silicon-on-insulator (SOI) platform. In this case, the support layer A includes a silicon base layer and a silicon oxide layer ( Figure 3 The functional layer includes a silicon top layer. The optical micro-electromechanical structure of this embodiment can be applied to gyroscopes, accelerometers or other inertial measurement units. The following briefly describes the working principle of the optical micro-electromechanical structure of this embodiment using an optical micro-electromechanical accelerometer as an example: Figure 1As shown, the suspended optical waveguide 4 is coupled to the photonic crystal microcavity 3, serving as a medium for optical signal input and output. Incident light waves of a specific wavelength are input through one end of the suspended optical waveguide 4 (e.g., in the negative direction of the X-axis) and couple with the photonic crystal microcavity 3. When the spacing between the suspended optical waveguide 4 and the photonic crystal microcavity 3 is fixed, the coupling efficiency is determined by the difference between the wavelength of the incident light wave and the resonant wavelength of the photonic crystal microcavity 3. The resonant wavelength of the photonic crystal microcavity 3 is related to the gap between the first suspended photonic crystal 301 and the second suspended photonic crystal 302. When an acceleration along the Y-direction is applied to the system, the suspended mass 1 undergoes relative displacement along the Y-direction due to inertia, thereby changing the gap between the first suspended photonic crystal 301 and the second suspended photonic crystal 302, thereby changing the resonant wavelength of the photonic crystal microcavity 3 and, consequently, the coupling efficiency between the suspended optical waveguide 4 and the photonic crystal microcavity 3. By detecting the change of the optical signal at the output end (eg, the positive direction of the X-axis) of the suspended optical waveguide 4, the change of the gap between the first suspended photonic crystal 301 and the second suspended photonic crystal 302 can be inversely calculated, thereby obtaining the acceleration to be measured.

[0073] In order to achieve optimal coupling efficiency, it is necessary to control the wavelength error of the incident light or the resonant wavelength offset of the photonic crystal microcavity 3 to within tens of picometers or even a few picometers. However, due to errors in wafer lithography production, the resonant wavelength of the photonic crystal microcavity 3 may offset by several nanometers. Therefore, it is very necessary to be able to actively modulate the photonic crystal microcavity 3. The optical microelectromechanical structure of this embodiment can modulate the optical microcavity of the optical microelectromechanical structure through the capacitor 9, thereby achieving active tuning of its resonant wavelength, so that the photonic crystal microcavity can be efficiently coupled with the incident light wave.

[0074] It should be noted that in the precision-controlled modulated optical microelectromechanical structure of this embodiment, the capacitor 9 is not directly connected to the suspended mass block 1, but only modulates the photonic crystal microcavity gap, without affecting the mechanical properties of the suspended mass block 1. In other words, only the optical properties are modulated, which can avoid modulation crosstalk.

[0075] In addition, in the precision-controlled modulated optical microelectromechanical structure of this embodiment, the suspended optical waveguide 4 is fixedly connected to one end of the photonic crystal microcavity 3 (the second suspended photonic crystal 302), which ensures that when acceleration is applied, the suspended optical waveguide 4 and the photonic crystal microcavity 3 do not undergo relative displacement, and the spacing distance between the suspended optical waveguide 4 and the photonic crystal microcavity 3 (the length of the first connecting ligament 5 along the Y direction) remains unchanged, which can improve the stability of optical coupling and the overall stability of the system.

[0076] In this embodiment, the capacitor 9 is a parallel plate capacitor, i.e., the first capacitor terminal 901 and the second capacitor terminal 902 are two parallel plates arranged opposite each other. Depending on the requirements, the thickness of the first capacitor terminal 901 ranges from 50 nanometers to 300 nanometers, the length along the X direction ranges from 20 micrometers to 200 micrometers, and the width along the Y direction ranges from 100 nanometers to 2 micrometers; the thickness of the second capacitor terminal 902 ranges from 50 nanometers to 300 nanometers, the length along the X direction ranges from 20 micrometers to 200 micrometers, and the width along the Y direction ranges from 100 nanometers to 2 micrometers.

[0077] Specifically, the basic working principle of capacitance modulation is as follows: Figure 3 The figure shows a schematic diagram of a parallel plate capacitor, where the distance between the two ends of the parallel plate capacitor is W. g , the voltage applied across the capacitor is V. The upper end of the capacitor is rigidly fixed, and the lower end is connected to a flexible structure that can move along the Y direction. Assuming the relative translation distance of the lower end of the capacitor is y, the capacitance C(y) is a function relative to y. For a parallel plate capacitor:

[0078]

[0079] Where A is the relative area of ​​the plate capacitor and ∈0 is the vacuum permittivity.

[0080] For capacitors formed by metal wires integrated into the chip, the electric field distribution at the edge will have a significant impact due to the similar thickness and spacing of the metal wires. Therefore, the parallel plate model needs to be modified as follows:

[0081]

[0082] Where n is a real number between 0 and 1. Therefore, the electrostatic force generated by the capacitor is:

[0083]

[0084] This electrostatic force will balance the elastic restoring force of the flexible structure, introducing the effective elastic coefficient k eff , then:

[0085] F(y)=k eff y (4)

[0086] When x<<w g , the displacement caused by the electrostatic force can be approximated by equations (3) and (4):

[0087]

[0088] It can be seen that the displacement δy is proportional to the square of the applied voltage (V 2) and capacitor gap W g The negative (n+1) power, that is, w g -(n+1) .

[0089] Specifically, the capacitance-tuned optical microelectromechanical structure of this embodiment uses the capacitor 9 to actively tune the resonant wavelength of the photonic crystal microcavity 3, utilizing the following principle: When a voltage is applied to the capacitor 9, an electrostatic force is generated, thereby changing the gap between the first capacitor terminal 901 and the second capacitor terminal 902. Since the second suspended photonic crystal 302 is sequentially connected to the first capacitor terminal 901 of the capacitor 9 via the first connecting tether 5, the suspended optical waveguide 4, the second connecting tether 7, and the suspended beam 6, when the first capacitor terminal 901 moves, the second suspended photonic crystal 302 also moves simultaneously, thereby changing the gap of the photonic crystal microcavity 3 and, consequently, the resonant wavelength of the photonic crystal microcavity 3. In this way, the resonant wavelength can be continuously adjusted, thereby achieving efficient coupling with the incident light wave.

[0090] Therefore, if the electrostatic force generated by the capacitor 9 causes a displacement δy, the corresponding shift of the resonant wavelength of the photonic crystal microcavity 3 is:

[0091]

[0092] Among them, g om is the optomechanical coupling strength, λ0 is the resonant wavelength of the initial photonic crystal microcavity, and c is the speed of light.

[0093] As can be seen from the above, the capacitance-tuned optical microelectromechanical structure of this embodiment can use the capacitor 9 to actively tune the resonant wavelength of the photonic crystal microcavity 3, thereby correcting the optical microcavity produced by the photolithography process, reducing or eliminating the impact caused by errors in wafer photolithography production, so that the resonant wavelength of the photonic crystal microcavity is perfectly matched with the designed operating wavelength, and achieving optimal coupling efficiency with the incident light wave.

[0094] In addition, by actively tuning the resonance wavelength of the photonic crystal microcavity 3 using the capacitor 9, the offset of the resonance wavelength caused by changes in the working environment (such as thermal expansion and contraction caused by temperature) can be adjusted, thereby improving measurement accuracy.

[0095] Furthermore, by actively tuning the resonance wavelength of the photonic crystal microcavity 3 using the capacitor 9, the photonic crystal microcavity 3 can also be made to match different incident wavelengths, thereby being suitable for different operating wavelengths and matching different laser light sources, thereby improving the adaptability and ease of use of the device.

[0096] Specifically, the photonic crystal microcavity 3 includes a defect region M and a mirror region. The mirror region is distributed on both sides of the defect region M in the X direction to achieve confinement of the light field in the X direction. In this embodiment, the mirror region is also distributed on both sides of the defect region A in the Y direction, thereby achieving confinement of the light field in both the X and Y directions.

[0097] Specifically, the first suspended photonic crystal 301 and the second suspended photonic crystal 302 are placed in each other's near field. The strong coupling between the two photonic crystal strips forms an energy band structure, which, combined with total internal reflection, confines the optical mode to the defect area of ​​the optical resonant cavity (that is, the photonic crystal microcavity), that is, the center position of the optical resonant cavity.

[0098] As an example, the first suspended photonic crystal 301 and the second suspended photonic crystal 302 each include a plurality of air holes arranged in at least one row, wherein the row direction is the X direction, and the sizes of the plurality of air holes located in the defect region M and arranged in the X direction form an arithmetic progression, gradually decreasing or increasing from the left and right sides to the middle, and the sizes of the plurality of air holes located in the mirror region are the same.

[0099] As an example, the air holes are circular holes with a diameter ranging from 100 nanometers to 1000 nanometers. Except for the defective area M, the diameters of the air holes in other areas are the same.

[0100] As an example, when the first suspended photonic crystal 301 includes two or more rows of air holes, the multiple air holes in the first suspended photonic crystal 301 are arranged in a triangular array, that is, the air holes in two adjacent rows are staggered, and at the same time, except for the air holes at the extreme edges on the left and right sides, each air hole forms an equilateral triangle with the two air holes closest to the adjacent row. The air hole arrangement of the second suspended photonic crystal 302 is substantially the same as that of the first suspended photonic crystal 301, and the air holes in the row closest to the gap in the second suspended photonic crystal 301 are symmetrically distributed about the X-axis with the air holes in the row closest to the gap in the first suspended photonic crystal 301.

[0101] As an example, the number of rows of air holes in the second suspended photonic crystal 302 may be the same as or different from the number of rows of air holes in the first suspended photonic crystal 301 .

[0102] Specifically, in this embodiment of the precision-controlled modulated optical microelectromechanical system, the suspended mass 1 is suspended by multiple suspension tethers 2 (four in this embodiment). Adjusting the dimensions of the suspended mass 1 and the suspension tethers 2 allows the mechanical resonant frequency of the optical microelectromechanical system to be adjusted. Depending on the operating frequency, the length of the suspended mass 1 along the X-direction can range from 30 microns to 500 microns, and the width along the Y-direction can range from 10 microns to 300 microns. The length of the suspension tethers 2 along the X-direction can range from 50 microns to 2000 microns, and the width along the Y-direction can range from 50 nanometers to 400 nanometers. Depending on the device's operating wavelength, the width of the suspended optical waveguide 4 along the Y-direction can range from 400 nanometers to 2000 nanometers.

[0103] The precision controllable modulated optical micro-electromechanical structure of the present embodiment uses a parallel plate capacitor to actively tune the resonant wavelength of the photonic crystal microcavity, thereby achieving active tuning of its resonant wavelength, and can correct the optical microcavity produced by the photolithography process, reduce or eliminate the impact caused by the error of wafer photolithography production, so that the actual resonant wavelength of the photonic crystal microcavity is perfectly matched with the designed working wavelength. In addition, actively tuning the resonant wavelength of the photonic crystal microcavity by the capacitor can also compensate for the offset of the resonant wavelength caused by changes in the working environment (such as thermal expansion and contraction caused by temperature), thereby improving measurement accuracy. The manufacturing process of the precision controllable modulated optical micro-electromechanical structure of the present embodiment is simple and can be compatible with current silicon photonic processes. In the capacitor-tuned optical micro-electromechanical structure of the present embodiment, the capacitor only modulates the gap of the photonic crystal microcavity and does not affect the mechanical properties of the mass block, that is, it only modulates the optical properties, which can avoid modulation crosstalk. In this embodiment of the precision-controlled modulated optical microelectromechanical structure, the optical waveguide is fixedly connected to one end of the optical microcavity, ensuring that when acceleration is applied, the optical waveguide and the optical microcavity do not undergo relative displacement, thereby improving the stability of the optical coupling and, consequently, the overall stability of the system. This embodiment of the capacitance-tuned optical microelectromechanical structure can also selectively widen the optical waveguide connection ligament locally, forming a trapezoidal structure. This reduces the scattering rate of the connection ligament, thereby improving signal loss and enhancing the signal-to-noise ratio.

[0104] Example 2

[0105] This embodiment and the first embodiment use basically the same structure, the difference being that in the first embodiment, a parallel plate capacitor is used to actively tune the resonant wavelength of the photonic crystal microcavity, while in this embodiment, a comb capacitor is used to actively tune the resonant wavelength of the photonic crystal microcavity.

[0106] See also Figure 4, which shows an XY plane diagram of the precision controllable modulated optical microelectromechanical structure of this embodiment, wherein the first capacitance end of the comb capacitor includes a first beam 901a, and the second capacitance end includes a second beam 902a. The first beam 901a and the second beam 902a are spaced apart in the Y direction. A plurality of first comb teeth 901b are connected to a side of the first beam 901a facing the second beam 902a, and a plurality of second comb teeth 902b are connected to a side of the second beam 902a facing the first beam 901a. The plurality of first comb teeth 901b and the plurality of second comb teeth 902b are alternately arranged in the X direction and partially overlap in the Y direction.

[0107] As an example, according to requirements, the number of the first comb teeth 901b can range from 5 to 100, the length along the Y direction can range from 5 microns to 20 microns, and the width along the X direction can range from 500 nanometers to 2 microns; the number of the second comb teeth 902b can range from 5 to 100, the length along the Y direction can range from 5 microns to 20 microns, and the width along the X direction can range from 500 nanometers to 2 microns; the gap width between adjacent first comb teeth 901b and second comb teeth 902b in the X direction can range from 100 nanometers to 500 nanometers, the distance between the end of the first comb tooth 901b and the second crossbeam 902a in the Y direction can range from 2 microns to 4 microns, for example, 3 microns, and the distance between the end of the second comb tooth 902b and the first crossbeam 901a in the Y direction can range from 2 microns to 4 microns, for example, 3 microns.

[0108] See also Figure 5 , which shows a partially enlarged schematic diagram of the comb-tooth capacitor structure, where L is the length of the comb teeth along the Y direction, G is the relative distance between the two comb teeth in the X direction, D is the distance from the end of the comb teeth to the other end of the beam of the capacitor along the Y direction, and W is the width of the comb teeth along the X direction. Assuming the number of comb teeth is N, the capacitance of the comb-tooth capacitor is:

[0109]

[0110] When a voltage V is applied, the electrostatic force generated is:

[0111]

[0112] This shows that the electrostatic force of the comb-tooth capacitor is independent of L and D, and can provide displacement adjustment on the scale of tens of nanometers or even micrometers. Compared to the first embodiment, which uses a parallel plate capacitor to actively tune the resonant wavelength of the photonic crystal microcavity, which can only achieve nanometer-scale adjustment, the use of the comb-tooth capacitor in this embodiment can achieve a larger adjustment of the photonic crystal microcavity gap, thereby achieving a larger adjustment of the resonant frequency, and can match a wider range of incident wavelengths, thereby being applicable to different operating wavelengths, improving the adaptability and ease of use of the device.

[0113] In summary, the optical micro-electromechanical structure of the precision controllable modulation of the present invention uses a capacitance modulation method to modulate the optical microcavity of the optical micro-electromechanical structure, thereby realizing active tuning of its resonant wavelength, and can correct the optical microcavity produced by the photolithography process, reduce or eliminate the influence caused by the error of wafer photolithography production, so that the actual resonant wavelength of the photonic crystal microcavity is perfectly matched with the designed working wavelength. In addition, the resonant wavelength of the photonic crystal microcavity is actively tuned by the capacitor, and the offset of the resonant wavelength caused by changes in the working environment (such as thermal expansion and contraction caused by temperature) can be compensated, thereby improving measurement accuracy. In the optical micro-electromechanical structure of the precision controllable modulation of the present invention, the capacitance modulation method can be parallel plate capacitance modulation or comb capacitance modulation, wherein the comb capacitance modulation method can realize a larger adjustment of the photonic crystal microcavity gap, thereby realizing a larger adjustment of the resonant frequency, and can match a larger range of incident wavelengths, thereby being applicable to different working wavelengths, and improving the adaptability and ease of use of the device. The manufacturing process of the optical micro-electromechanical structure of the precision controllable modulation of the present invention is simple and can be compatible with current silicon photonic processes. In the capacitance-tuned optical micro-electromechanical structure of the present invention, the capacitor only modulates the gap of the photonic crystal microcavity without affecting the mechanical properties of the mass block, that is, it only modulates the optical properties, which can avoid modulation crosstalk. In the precision-controlled modulated optical micro-electromechanical structure of the present invention, the optical waveguide is connected and fixed to one end of the optical microcavity, which can ensure that when acceleration is applied, the optical waveguide and the optical microcavity will not undergo relative displacement, thereby improving the stability of the optical coupling and thus improving the overall stability of the system. The present invention can also selectively widen the optical waveguide connecting ligament locally to form a trapezoidal structure, reducing the scattering rate of the connecting ligament, thereby increasing the signal loss and improving the signal-to-noise ratio. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0114] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An optical micro-electromechanical structure with controllable precision modulation, characterized in that: include: Suspended mass; a plurality of suspension tethers, distributed on both sides of the suspended mass in the X direction and connected to the suspended mass; a photonic crystal microcavity located on one side of the suspended mass in the Y direction, wherein the Y direction is perpendicular to the X direction, the photonic crystal microcavity comprising a first suspended photonic crystal and a second suspended photonic crystal, wherein the first suspended photonic crystal is fixed to the suspended mass, and the second suspended photonic crystal is located on a side of the first suspended photonic crystal away from the suspended mass and spaced apart from the first suspended photonic crystal; a suspended optical waveguide, located on a side of the photonic crystal microcavity away from the suspended mass block and spaced apart from the photonic crystal microcavity by a preset distance; a first connecting tether connected between the second suspended photonic crystal and the suspended optical waveguide; a suspension beam, located on a side of the suspension optical waveguide away from the photonic crystal microcavity and spaced apart from the suspension optical waveguide; a second connecting tie, connected between the suspended optical waveguide and the suspended beam; a rigid block, located on a side of the suspension beam away from the suspension optical waveguide and spaced apart from the suspension beam; The capacitor includes a first capacitor end and a second capacitor end spaced apart in the Y direction, wherein the first capacitor end is fixed to the suspension beam, and the second capacitor end is fixed to the rigid block.

2. The precision-controllable modulated optical micro-electromechanical structure according to claim 1, characterized in that: The suspended optical waveguide includes a crossbeam, a first connecting block, and a second connecting block. The crossbeam extends along the X direction. The first connecting block and the second connecting block are both connected to a side of the crossbeam away from the photonic crystal microcavity. The vertical projection of the first connecting lace on the XZ plane is within the range of the vertical projection of the first connecting block on the XZ plane. The end of the second connecting lace away from the suspended beam is connected to the second connecting block.

3. The precision-controlled modulated optical micro-electromechanical structure according to claim 2, characterized in that: The vertical projection of the first connecting block on the XY plane is trapezoidal, and the vertical projection of the second connecting block on the XY plane is trapezoidal.

4. The precision-controllable optical micro-electromechanical structure according to claim 1, characterized in that: The first capacitor end is located on the upper surface of the suspension beam, and the second capacitor end is located on the upper surface of the rigid block.

5. The precision-controllable optical micro-electromechanical structure according to claim 1, characterized in that: The optical microelectromechanical structure includes a supporting layer and a functional layer located on the supporting layer. The suspended mass block, the suspended tether, the first suspended photonic crystal, the second suspended photonic crystal, the suspended optical waveguide, the suspended beam, the first connecting tether and the second connecting tether are all formed based on the functional layer, and the rigid block is formed based on the supporting layer and the functional layer.

6. The precision-controllable modulated optical micro-electromechanical structure according to claim 5, characterized in that: The supporting layer includes a silicon layer, and the functional layer includes a silicon nitride layer; or the supporting layer includes a silicon base layer and a silicon oxide layer located on the silicon base layer, and the functional layer includes a silicon top layer.

7. The precision-controllable modulated optical micro-electromechanical structure according to claim 1, characterized in that: The optical micro-electromechanical structure is applied to a gyroscope or an accelerometer.

8. The precision-controllable modulated optical micro-electromechanical structure according to claim 1, characterized in that: The capacitor is a parallel plate capacitor.

9. The precision-controllable modulated optical micro-electromechanical structure according to claim 8, characterized in that: The thickness of the first capacitor terminal is in the range of 50 nanometers to 300 nanometers, the length along the X direction is in the range of 20 micrometers to 200 micrometers, and the width along the Y direction is in the range of 100 nanometers to 2 micrometers; the thickness of the second capacitor terminal is in the range of 50 nanometers to 300 nanometers, the length along the X direction is in the range of 20 micrometers to 200 micrometers, and the width along the Y direction is in the range of 100 nanometers to 2 micrometers.

10. The precision-controllable modulated optical micro-electromechanical structure according to claim 1, characterized in that: The capacitor is a comb-tooth capacitor, wherein the first capacitor end includes a first beam, the second capacitor end includes a second beam, the first beam and the second beam are spaced apart in the Y direction, a plurality of first comb teeth are connected to a side of the first beam facing the second beam, and a plurality of second comb teeth are connected to a side of the second beam facing the first beam, the plurality of first comb teeth and the plurality of second comb teeth are alternately arranged in the X direction and partially overlap in the Y direction.

11. The precision-controllable modulated optical micro-electromechanical structure according to claim 10, characterized in that: The number of the first comb teeth ranges from 5 to 100, the length along the Y direction ranges from 5 microns to 20 microns, and the width along the X direction ranges from 500 nanometers to 2 microns; the number of the second comb teeth ranges from 5 to 100, the length along the Y direction ranges from 5 microns to 20 microns, and the width along the X direction ranges from 500 nanometers to 2 microns; the width of the gap between adjacent first and second comb teeth in the X direction ranges from 100 nanometers to 500 nanometers, the distance between the end of the first comb tooth and the second crossbeam in the Y direction ranges from 2 microns to 4 microns, and the distance between the end of the second comb tooth 302b and the first crossbeam in the Y direction ranges from 2 microns to 4 microns.

12. The precision-controllable modulated optical micro-electromechanical structure according to claim 1, characterized in that: The photonic crystal microcavity includes a defect region and a mirror region. The mirror region is distributed on both sides of the defect region in the X direction, or the mirror region is distributed on both sides of the defect region in the X direction and the Y direction.

13. The precision-controllable modulated optical micro-electromechanical structure according to claim 12, characterized in that: The first suspended photonic crystal and the second suspended photonic crystal each include a plurality of air holes arranged in at least one row, wherein the row direction is the X direction, and the sizes of the plurality of air holes located in the defect area and arranged in the X direction form an arithmetic progression, gradually decreasing or increasing from the left and right sides to the middle, and the sizes of the plurality of air holes located in the mirror area are the same.

14. The precision-controllable modulated optical micro-electromechanical structure according to claim 13, characterized in that: The first suspended photonic crystal and the second suspended photonic crystal both include a plurality of air holes arranged in at least two rows. The plurality of air holes in the first suspended photonic crystal are arranged in a triangular array, and the plurality of air holes in the second suspended photonic crystal are arranged in a triangular array.

15. The precision-controllable modulated optical micro-electromechanical structure according to claim 1, characterized in that: The length of the suspended mass along the X direction ranges from 30 microns to 500 microns, and the width along the Y direction ranges from 10 microns to 300 microns; the length of the suspended tether along the X direction ranges from 50 microns to 2000 microns, and the width along the Y direction ranges from 50 nanometers to 400 nanometers; the width of the suspended optical waveguide along the Y direction ranges from 400 nanometers to 2000 nanometers.

16. The precision-controllable modulated optical micro-electromechanical structure according to claim 1, characterized in that: The material of the first capacitor terminal includes one or more of gold, silver, aluminum and copper, and the material of the second capacitor terminal includes one or more of gold, silver, aluminum and copper.

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