Feedthrough suppression for optomechanical devices

Abstract

The present invention relates to an optomechanical device for generating and detecting optical signals, the optomechanical device comprising a proof mass assembly, one or more laser devices, and an electrical circuit. The one or more laser devices are configured to generate a first optical signal and a second optical signal. The electrical circuit is configured to modulate the second optical signal with an electro-optic modulator (EOM), output the first optical signal and the second optical signal to the proof mass assembly, generate a filtered optical signal corresponding to a response of the proof mass assembly to the first optical signal but not the second optical signal, and generate an electrical signal based on the filtered optical signal, wherein the EOM modulates the second optical signal based on the electrical signal.

Description

Technical Field

[0001] This disclosure relates to optomechanical devices, such as accelerometers configured to use optical signals to measure acceleration. Background Technology

[0002] Optomechanical devices include apparatuses for detecting acceleration, velocity, vibration, and other parameters. For example, in an optomechanical accelerometer, the resonant frequency of a mechanical structure shifts under acceleration within the optomechanical device. The mechanical resonant frequency can be read out using an optical field by applying near-resonant light to the optical resonance of the structure and measuring the transmitted or reflected light signal. Summary of the Invention

[0003] Generally, this disclosure relates to means, systems, and techniques for reducing drive feedthrough in optomechanical devices. As used herein, drive feedthrough can refer to a portion of an optical drive field that leaks into a detection path and is independent of acceleration. Drive feedthrough can limit the final noise floor, thereby limiting the performance of the optomechanical device. For example, circuitry can be configured to output a first optical signal as a drive field to drive a mechanical response to a verification mass block assembly, and output a second optical signal as a sensing field to the verification mass block assembly to detect one or more of phase modulation or frequency modulation of mechanical vibrations in the verification mass block assembly.

[0004] In one example, an optomechanical device for generating and detecting optical signals includes: a verification mass block assembly; one or more laser devices configured to generate a first optical signal and a second optical signal, wherein the frequency of the first optical signal is different from the frequency of the second optical signal; and circuitry configured to: modulate the second optical signal with an electro-optic modulator (EOM); output the first and second optical signals to the verification mass block assembly; generate a filtered optical signal corresponding to the response of the verification mass block assembly to the first optical signal but not the second optical signal; and generate an electrical signal based on the filtered optical signal, wherein the EOM modulates the second optical signal based on the electrical signal.

[0005] In another example, a method for generating and detecting an optical signal includes: generating a first optical signal and a second optical signal via one or more laser devices, wherein the frequency of the first optical signal is different from the frequency of the second optical signal; modulating the second optical signal via an electro-optic modulator (EOM) of a circuit; outputting the first optical signal and the second optical signal to a verification quality block component by the circuit; generating a filtered optical signal by the circuit corresponding to the response of the verification quality block component to the first optical signal but not the second optical signal; and generating an electrical signal by the circuit based on the filtered optical signal, wherein the EOM is configured to modulate the second optical signal based on the electrical signal.

[0006] In another example, an optomechanical system for generating and detecting optical signals includes: one or more laser devices configured to generate a first optical signal and a second optical signal, wherein the first optical signal includes a frequency different from that of the second optical signal; and circuitry configured to: modulate the second optical signal with an electro-optic modulator (EOM); output the first and second optical signals to a mechanical component; generate a filtered optical signal corresponding to the mechanical component's response to the first optical signal but not the second optical signal; and generate an electrical signal based on the filtered optical signal, wherein the EOM modulates the second optical signal based on the electrical signal.

[0007] The present invention is intended to provide an overview of the subject matter described herein. It is not intended to provide an exclusive or exhaustive description of the systems, apparatus, and methods detailed in the following drawings and specification. Further details of one or more examples of this disclosure are set forth in the following drawings and specification. Other features, objects, and advantages will be apparent from the description and drawings, as well as from the claims. Attached Figure Description

[0008] Figure 1 This is a block diagram illustrating an electro-optical mechanical system according to one or more technologies of this disclosure.

[0009] Figure 2 This illustrates in more detail one or more technologies according to this disclosure. Figure 1 The circuit block diagram.

[0010] Figure 3 The illustration shows a verification mass block suspended within a frame via a first double-ended tuning fork (DETF) structure, a second DETF structure, and a set of tethering elements, according to one or more techniques of this disclosure. Figure 1 A conceptual diagram of the verification quality block component.

[0011] Figure 4 One or more technologies according to this disclosure are shown. Figure 1 A conceptual diagram of an electro-optical mechanical system.

[0012] Figure 5 One or more technologies according to this disclosure are shown. Figure 1 Additional aspects of electro-optical mechanical systems.

[0013] Figure 6 A conceptual diagram illustrating an exemplary technique for reducing drive feedthrough in an optomechanical device according to one or more techniques of the present invention.

[0014] Figure 7 A conceptual diagram of an exemplary first optical response of a first optical frequency component and a second optical frequency component according to one or more techniques of this disclosure.

[0015] Figure 8 A conceptual diagram of an exemplary second optical response of a first optical frequency component and a second optical frequency component according to one or more techniques of this disclosure.

[0016] Figure 9 A conceptual diagram illustrating an example of applying one or more techniques according to this disclosure to verify optical signals of a mass block assembly.

[0017] Figure 10 For the verification mass block component in response to one or more techniques according to this disclosure Figure 9 A conceptual diagram illustrating an example of an optical signal that is reflected and output as a light signal.

[0018] Figure 11 For the purpose of one or more technologies according to this disclosure Figure 10 A conceptual diagram illustrating an example of a filtered optical signal obtained by filtering an optical signal.

[0019] Figure 12 A flowchart illustrating an example of reducing drive feedthrough in an optomechanical device according to one or more techniques of this disclosure.

[0020] Similar reference characters are used to denote similar elements throughout the specification and drawings. Detailed Implementation

[0021] This disclosure describes apparatus, systems, and techniques for reducing the detection of drive feedthroughs into optomechanical devices, such as, but not limited to, optomechanical accelerometers, electrical filters (e.g., high-pass filters, low-pass filters, and band-pass filters), strain sensors, pressure sensors, force sensors, and gyroscopes, wherein the structure has coupled optical degrees of freedom and can help improve the performance of such optomechanical devices. For example, in an optomechanical accelerometer, the resonant frequency of the mechanical structure shifts under acceleration in the optomechanical device. The mechanical resonant frequency can be measured using an optical field by applying near-resonant light to the optical resonance of the structure and measuring the transmitted or reflected light (since the mechanical resonant frequency is affected when the phase and / or amplitude of the light is modulated by optomechanical coupling in the device). To improve the signal-to-noise ratio of the mechanical frequency measurement, the system can drive the mechanical resonance to a larger amplitude by modulating the optical field with a strong amplitude at or near the mechanical resonant frequency; this can be referred to as “drive modulation” of the input optical field. Conversely, “sensory modulation” can refer to modulation caused by mechanical vibrations on the outgoing optical field and can be less than or even less than the drive modulation of the incident drive optical field. In optomechanical devices that use a single laser field for driving and sensing, the emitted sensing light field can therefore exhibit harmful "feedthrough" modulation on the light field, which can fundamentally distort, blur, or otherwise degrade the quality of the light signal.

[0022] The techniques described herein can mitigate or help eliminate distortion from feedthrough modulation. In some examples, an optomechanical accelerometer can use one laser wavelength for the driving field and another laser wavelength for the sensing field. The laser wavelength used for the driving field and the laser wavelength used for the sensing field can be separated by using wavelength-selective optics such as, but not limited to, filters or dichroic mirrors. Combined with appropriate readout and feedback systems, the techniques described herein can provide a detection signal without "feedthrough," which can be locked to mechanical resonance, and advantageously, little or no distortion or noise present in systems without feedthrough elimination.

[0023] For example, an optomechanical device may include an electro-optical mechanical system configured to accurately measure very high acceleration values ​​(e.g., up to 500,000 meters per second squared (m / s²)). 2 Electro-optical systems can use a combination of electrical, optical, and mechanical signals to determine the acceleration of an object.

[0024] Optomechanical devices can be configured to measure an object's acceleration, velocity, vibration, etc., in real-time or near real-time, enabling processing circuitry to analyze the object's acceleration, velocity, vibration, etc., over a time period to determine the object's positional displacement during that period. For example, the optomechanical device can be part of an inertial navigation system (INS) used to track the object's position based at least in part on its acceleration. Alternatively, the optomechanical device can be located on or within the object, causing it to accelerate, move, vibrate, etc., along with the object. Thus, when the object accelerates, moves, vibrates, etc., the optomechanical device (including mechanical components, verification mass blocks, etc.) accelerates, moves, vibrates, etc., along with the object. In some examples, since acceleration over time is the derivative of velocity over time, and velocity over time is the derivative of position over time, in some cases, the processing circuitry can be configured to determine the object's positional displacement by performing a double integral of the object's acceleration over a time period. Determining the position of an object using an accelerometer system located on the object, rather than using a navigation system separate from the object (such as the Global Positioning System (GPS)), can be called "dead reckoning".

[0025] Optomechanical devices can be configured to achieve high levels of sensitivity to improve the accuracy of values ​​such as acceleration, velocity, and vibration. High sensitivity enables the optomechanical device to detect very small values ​​of acceleration, velocity, and vibration; very small changes in these values; a wide range of values; or any combination thereof. Furthermore, while an object is experiencing high levels of acceleration, velocity, and vibration, the optomechanical device can be configured to accurately determine the object's acceleration, velocity, and vibration. Thus, the optomechanical device can be configured to enable the INS to accurately track the object's position even when the magnitudes of the object's acceleration, velocity, and vibration are very high.

[0026] In some examples, the optomechanical device may include a MEMS accelerometer having a light-emitting device, circuitry, and a verification mass assembly comprising a verification mass suspended within a frame via a double-ended tuning fork (DETF) structure. In some examples, the optomechanical device may include a single-ended tuning fork or another mechanical component. For example, the optomechanical device may use a mechanical component suitable for an electrical filter (e.g., a high-pass filter, a low-pass filter, and a band-pass filter), a strain sensor, a pressure sensor, a force sensor, a gyroscope, or another mechanical component.

[0027] In some examples, the DETF structure can be configured to guide optical signals. Additionally, the optical signals can induce mechanical vibrations within the DETF structure. In some cases, acceleration causes displacement of the verification mass block relative to the frame, which affects the mechanical vibration frequency (mechanical resonant frequency) corresponding to the DETF structure. Thus, a mathematical relationship can exist between acceleration and the mechanical vibration frequency of the DETF structure. Therefore, this mathematical relationship can be used to determine the acceleration. In some examples, the accelerometer device uses a combination of optical and electrical signals to measure the mechanical vibration frequency corresponding to the DETF structure and calculates the acceleration based on this mechanical vibration frequency.

[0028] Although examples of optomechanical devices are described with respect to an exemplary accelerometer, the noise suppression techniques described herein can be applied to optomechanical devices configured to measure various parameters, including but not limited to acceleration, velocity, vibration, and other parameters. Furthermore, while examples of optomechanical devices are described with respect to an exemplary verification mass block assembly including a DETF structure, other structures, such as, but not limited to, a single-ended tuning fork structure or another structure, may also be used.

[0029] Figure 1 This is a block diagram illustrating an electro-optical mechanical system 10 according to one or more technologies of this disclosure. Figure 1 This is merely a non-limiting exemplary system architecture that can be used to stabilize resonators using the techniques disclosed herein. Figure 1As shown, system 10 includes light-emitting devices 12A and 12B (collectively referred to as "light-emitting device 12"), circuitry 14, and verification mass block assembly 16. Additionally, in Figure 1 In the example shown, circuit 14 includes electro-optic modulators (EOMs) 22A, 22B (collectively referred to as "EOM 22"), optical receivers 24A, 24B (collectively referred to as "optical receiver 24"), feedback units 26A, 26B (collectively referred to as "feedback unit 26"), frequency counters 28A, 28B (collectively referred to as "frequency counter 28"), and processing circuitry 30. Although Figure 1 Examples include two EOMs, two optical receivers, and two frequency counters, but in some examples, the electro-optical system may include only one EOM, one optical receiver, and one frequency counter, or more than two EOMs, two optical receivers, and two frequency counters.

[0030] exist Figure 1 In the example, the light-emitting device 12A, the verification mass block assembly 16, the EOM 22A, the light receiver 24A, the feedback unit 26A, and the frequency counter 28A form a first positive feedback loop. Additionally, in Figure 1 In the example, the light-emitting device 12B, the verification mass block assembly 16, the EOM 22B, the light receiver 24B, the feedback unit 26B, and the frequency counter 28B form a second positive feedback loop. In some examples, the second positive feedback loop may be omitted.

[0031] System 10 can be configured to determine the relationship between the measured vibration frequency of the tuning fork structure of the verification mass block assembly and the object (in Figure 1 (not shown in the image) The acceleration associated with the object. For example, system 10 can be configured to determine the acceleration associated with the object (in the image) based on the measured vibration frequencies of a set of double-ended tuning fork (DETF) structures. Figure 1 (Not shown) The DETF structure suspends the verification mass block of the verification mass block assembly 16, wherein the vibration of the DETF structure is caused by a light signal emitted through the light-emitting device 12. In some examples, a first positive feedback loop generates a first frequency value representing the vibration frequency of the first DETF structure, and a second positive feedback loop generates a second frequency value representing the vibration frequency of the second DETF structure. Based on the first and second vibration frequencies, the system 10 can determine a first acceleration value and a second acceleration value, respectively. In some examples, the system 10 determines the acceleration of the object based on the first and second acceleration values. In some examples, the system 10 determines the acceleration of the object based only on the first acceleration value (e.g., the second positive feedback loop is omitted). In some examples, the system 10 determines the acceleration of the object based only on the second acceleration value (e.g., the first positive feedback loop is omitted).

[0032] Each of the light-emitting devices 12 may include a laser device (also referred to herein simply as a "laser") configured to emit photons forming an optical signal. In some examples, the light-emitting device 12 emits photons with an optical power ranging from 0.1 microwatts (μW) to 100 μW. In some examples, each of the light-emitting devices 12 includes a semiconductor laser having a laser diode. In some examples, each of the light-emitting devices 12 may be configured to generate a first optical signal that interacts with the verification mass block assembly 16 and, in response to the interaction with the verification mass block assembly 16, be subjected to one or more of phase modulation or frequency modulation of mechanical vibrations in the verification mass block assembly 16; and generate a second optical signal that excites the mechanical vibrations in the verification mass block assembly 16. Thus, the second optical signal (e.g., a drive optical signal) can provide drive modulation at the verification mass block assembly, and the feedback unit 26A can use the first optical signal interacting with the verification mass block assembly 16 (e.g., a sense optical signal) while the first optical signal drives the frequency of the mechanical vibrations at the verification mass block assembly 16.

[0033] In some examples, circuit 14 may include a set of electronic components for processing and analyzing the electrical signals received by optical receiver 24. The components of circuit 14 are described in further detail below.

[0034] EOM 22 may represent an optical device configured to modulate an optical signal emitted by a light-emitting device 12 based on an electrical signal generated and processed by circuit 14. For example, EOM 22A may include a set of crystals (e.g., lithium niobate crystals) whose refractive index varies with the electric field adjacent to the set of crystals. The refractive index of the crystals determines how EOM 22A modulates the optical signal. For example, the crystals of EOM 22A may receive an optical signal from the light-emitting device 12, while EOM 22A is also receiving an electrical signal from feedback unit 26A of circuit 14. Therefore, the electrical signal can affect the electric field of the crystals adjacent to EOM 22A, thereby causing EOM 22A to modulate the optical signal. In some examples, EOM 22A modulates the optical signal by using an electrical signal to modulate the refractive index of the crystals to drive a mechanical response in verification mass block assembly 16. In some cases, EOM 22A may send the modulated optical signal to verification mass block assembly 16. In some examples, EOM 22B is essentially similar to EOM 22A, wherein EOM 22B is controlled by an electrical signal from feedback unit 26B.

[0035] Optical receiver 24 (also referred to herein as a "photodiode") may each include one or more transistors configured to absorb photons of an optical signal and output an electrical signal in response to the absorption of photons. Thus, optical receiver 24 may be configured to convert an optical signal into an electrical signal. For example, optical receiver 24A may include a pn junction that converts photons of the optical signal into an electrical signal, wherein the electrical signal retains at least some parameters of the optical signal. In response to optical receiver 24A receiving an optical signal, one or more frequency and intensity values ​​associated with the optical signal may be reflected in the electrical signal generated by optical receiver 24A. For example, in response to receiving a stronger (e.g., higher power) optical signal, optical receiver 24A may generate a stronger electrical signal (e.g., a larger current value). Additionally, in some cases, optical receiver 24A may generate an electrical signal to reflect one or more frequency values ​​corresponding to the received optical signal. In other words, processing circuitry (e.g., processing circuitry 30) may analyze the electrical signal to determine one or more frequency values ​​corresponding to the optical signal. Optical receiver 24A may comprise any combination of semiconductor materials, such as indium gallium arsenide, silicon, silicon carbide, silicon nitride, gallium nitride, germanium, or lead sulfide. In some examples, optical receiver 24B is substantially similar to optical receiver 24A.

[0036] Feedback units 26 may each include a set of circuit components for processing electrical signals. In some examples, this set of circuit components included in feedback unit 26A may include any combination of bandpass filters, phase shifters, electronic amplifiers, and voltage limiters. Such components can process or filter electrical signals, making it possible to more effectively measure certain aspects of the electrical signal (e.g., frequency or intensity values). Figure 1 In this example, feedback unit 26A can receive electrical signals from optical receiver 24A and output the processed electrical signals to EOM 22A, frequency counter 28A, and light-emitting device 12A. Thus, feedback unit 26A acts as part of a first positive feedback loop by processing the electrical signals, which EOM 22A uses to modulate the light signal emitted by light-emitting device 12A. The modulated light signal passes through verification quality block assembly 16 before being processed by feedback unit 26A in return circuit 14.

[0037] Feedback unit 26B can be substantially similar to feedback unit 26A, since feedback unit 26B receives electrical signals from optical receiver 24B and delivers the processed electrical signals to frequency counter 28B, EOM 22B, and light-emitting device 12B. Therefore, feedback unit 26B operates in the second feedback loop in a manner similar to that of feedback unit 26A in the first feedback loop. Similarly, feedback unit 26B can be omitted.

[0038] Frequency counters 28 are circuit components each configured to measure the frequency of an electrical signal. For example, frequency counter 28A can determine one or more frequency values ​​corresponding to the processed electrical signal generated by feedback unit 26A. Frequency counter 28A can measure the frequency value corresponding to the processed electrical signal in real time or approximately real time, such that frequency counter 28A tracks the frequency value changing over time. Frequency counter 28B can be substantially similar to frequency counter 28A, except that frequency counter 28B receives the electrical signal from feedback unit 26B instead of from feedback unit 26A.

[0039] Processing circuitry 30 and circuitry 14 may typically include one or more processors configured to implement functions and / or processing instructions for execution within system 10. For example, processing circuitry 30 is capable of processing data stored in a storage device (in... Figure 1 Instructions (not shown in the document). Processing circuitry 30 may include, for example, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing means or circuits. Therefore, processing circuitry 30 may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions assigned to processing circuitry 30 herein. Processing circuitry 30 and circuitry 14 may include analog-only circuitry, digital-only circuitry, or a combination of analog and digital circuitry. The terms “processor” or “processing circuitry” may generally refer to any of the foregoing analog and / or digital circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.

[0040] The verification mass assembly 16 may include a verification mass, a frame, a set of tethers, and a set of DETF structures. In some examples, the verification mass is suspended within the frame by the set of tethers and the set of DETF structures. For example, the verification mass assembly 16 may include a set of DETF structures that suspend the verification mass relative to the frame in a first direction. Additionally, the set of tethers may suspend the verification mass relative to the frame in second and third directions. The first, second, and third directions may represent three axes of Cartesian space (e.g., the x-axis, y-axis, and z-axis). In some cases, the set of DETF structures allows the verification mass to displace in the first direction. Additionally, in some cases, the set of tethers prevents the verification mass from displacing in the second and third directions. Thus, the mass assembly 16 may allow the verification mass to displace only along a single axis (e.g., the displacement axis). Since the displacement of the verification mass can determine the acceleration measured by circuit 14, system 10 may be configured to determine the acceleration relative to the displacement axis.

[0041] In some examples, a first positive feedback loop (e.g., light-emitting device 12A, verification mass block assembly 16, EOM 22A, optical receiver 24A, feedback unit 26A, and frequency counter 28A) and a second positive feedback loop (e.g., light-emitting device 12B, verification mass block assembly 16, EOM 22B, optical receiver 24B, feedback unit 26B, and frequency counter 28B) are configured to independently determine acceleration values ​​representing the acceleration of an object comprising system 10. For example, light-emitting device 12 can emit an optical signal, EOM 22A can modulate the optical signal to drive a mechanical response in verification mass block assembly 16 to obtain a first modulated optical signal, and EOM 22A can transmit the first modulated optical signal to verification mass block assembly 16. Optical receiver 24A can receive the first modulated optical signal from verification mass block assembly 16, wherein the properties of the first modulated optical signal received by optical receiver 24A may be affected by mechanical vibrations of the first DETF structure of verification mass block assembly 16. The optical receiver 24A converts the first modulated optical signal into a first electrical signal and sends the first electrical signal to the feedback unit 26A.

[0042] Feedback unit 26A can process the first electrical signal to obtain a first processed electrical signal. For example, feedback unit 26A can use any combination of a first bandpass filter, a first phase shifter, a first electronic amplifier, and a first voltage limiter to process the first electrical signal. Frequency counter 28A can receive the first processed electrical signal and determine a first frequency value corresponding to the first processed electrical signal. In some cases, the first frequency value represents the mechanical vibration frequency of the first DETF structure of the verification mass block assembly 16, which carries the first modulated optical signal ultimately received by the optical receiver 24A.

[0043] In addition to sending the first processed electrical signal to the frequency counter 28A, the feedback unit 26A can also send the first processed electrical signal to the EOM 22A. The EOM 22A can then modulate the optical signal emitted by the light-emitting device 12 based on the first processed electrical signal, wherein the first modulated optical signal is sent to the optical receiver 24A via the first DETF structure of the verification mass block assembly 16, thereby completing the first positive feedback loop. Therefore, the future mechanical vibration frequency of the first DETF structure depends at least in part on the current mechanical vibration frequency of the first DETF structure.

[0044] Additionally, in some examples, a second positive feedback loop can determine a second frequency value. For example, the light-emitting device 12 can emit an optical signal, the EOM 22B can modulate the optical signal to obtain a second modulated optical signal, and the EOM 22B can send the second modulated optical signal to the verification mass block assembly 16. The optical receiver 24B can receive the second modulated optical signal from the verification mass block assembly 16, wherein the properties of the second modulated optical signal received by the optical receiver 24B may be affected by mechanical vibrations of the second DETF structure of the verification mass block assembly 16. The optical receiver 24B converts the second modulated optical signal into a second electrical signal and sends the second electrical signal to the feedback unit 26B.

[0045] In some examples, feedback unit 26B processes the second electrical signal to obtain a second processed electrical signal. For example, feedback unit 26B may use any combination of a second bandpass filter, a second phase shifter, a second electronic amplifier, and a second voltage limiter to process the second electrical signal. Frequency counter 28B may receive the second processed electrical signal and determine a second frequency value corresponding to the second processed electrical signal. In some cases, the second frequency value represents the mechanical vibration frequency of the second DETF structure of the verification mass block assembly 16, which carries the second modulated optical signal ultimately received by optical receiver 24B.

[0046] In addition to sending the second processed electrical signal to the frequency counter 28B, the feedback unit 26B can also send the second processed electrical signal to the EOM 22B. The EOM 22B can then modulate an optical signal based on the second processed electrical signal to drive the mechanical response in the verification mass block assembly 16 and emit it through the light-emitting device 12. The second modulated optical signal is transmitted to the optical receiver 24B via the second DETF structure of the verification mass block assembly 16, thus completing the second positive feedback loop. Therefore, the future mechanical vibration frequency of the second DETF structure depends at least in part on the current mechanical vibration frequency of the second DETF structure.

[0047] Processing circuitry 30 can be configured to calculate a first acceleration value based on a first frequency value. In some examples, to calculate the first acceleration value, processing circuitry 30 can subtract a baseline frequency value from the first frequency value to obtain a first frequency difference. This baseline frequency value can represent the resonant mechanical frequency of the first DETF structure of the verification mass assembly 16 when the verification mass is not displaced from its rest point along the verification mass displacement axis. In other words, when the verification mass is not displaced from its rest point along the verification mass displacement axis, the modulated optical signal emitted by EOM 22A can cause or drive the first DETF structure to vibrate at this baseline frequency value. Therefore, when the object is not accelerating, the first frequency difference can be equal to zero because the first acceleration value representing the mechanical frequency of the first DETF structure is equal to the baseline frequency value when the verification mass is not displaced (e.g., the object carrying system 10 is not accelerating). In some examples, the first frequency difference can be related to the acceleration of the object. In other words, an increase in the magnitude of the first frequency difference can indicate an increase in the object's acceleration, and a decrease in the magnitude of the first frequency difference can indicate a decrease in the object's acceleration.

[0048] Additionally, the processing circuit 30 can be configured to calculate a second acceleration value based on a second frequency value. In some examples, to calculate the second acceleration value, the processing circuit 30 can subtract a baseline frequency value from the second frequency value to obtain a second frequency difference. In some examples, the second frequency difference can be related to the acceleration of the object. In other words, an increase in the magnitude of the second frequency difference can indicate an increase in the object's acceleration, and a decrease in the magnitude of the second frequency difference can indicate a decrease in the object's acceleration. In some cases, the first acceleration value and the second acceleration value calculated by the processing circuit 30 can be approximately equal.

[0049] Figure 2 This illustrates in more detail one or more technologies according to this disclosure. Figure 1 The block diagram of circuit 14. (See example.) Figure 1 As shown, circuit 14 includes an EOM 22, an optical receiver 24, a feedback unit 26, a frequency counter 28, and a processing circuit 30. The feedback unit 26 may each include bandpass filters 40A and 40B (collectively referred to as "bandpass filter 40"), phase shifters 42A and 42B (collectively referred to as "phase shifter 42"), electronic amplifiers 44A and 44B (collectively referred to as "electronic amplifier 44"), and drivers 47A and 47B (collectively referred to as "driver 47"). The first feedback loop includes bandpass filter 40A, phase shifter 42A, electronic amplifier 44A, and driver 47A. The second feedback loop includes bandpass filter 40B, phase shifter 42B, electronic amplifier 44B, and driver 47B.

[0050] Circuit 14 can be configured to: receive an optical signal from the verification mass block assembly 16; convert the optical signal into an electrical signal; process the electrical signal; analyze the processed electrical signal to determine an acceleration value; and use the processed electrical signal to modulate the optical signal and suppress noise, thereby completing a first feedback loop and a second feedback loop. While this example is an accelerometer, in some examples, circuit 14 can be configured to analyze the processed electrical signal to determine other values, such as, but not limited to, velocity, vibration, rotation, and other values. For example, optical receiver 24A can receive a first modulated optical signal from a first DETF structure of the verification mass block assembly 16. The first modulated optical signal may include frequency components associated with the first DETF structure itself, such as the vibration frequency of the first DETF structure. Optical receiver 24A can convert the first modulated optical signal into a first set of electrical signals to maintain the frequency components indicating the vibration frequency of the first DETF structure for driver 47A. Optical receiver 24A can transmit the first set of electrical signals to feedback unit 26A, which includes a bandpass filter 40A, a phase shifter 42A, an electronic amplifier 44A, and driver 47A.

[0051] The bandpass filter 40A can be an electronic filter that attenuates frequencies outside its frequency range and allows frequencies within its range to "pass through". In some examples, the bandpass filter 40A includes any combination of passive filters, active filters, infinite impulse response (IIR) filters, finite impulse response (FIR) filters, Butterworth filters, Chebyshev filters, elliptic filters, Bessel filters, Gaussian filters, Legendre filters, or Linkwick-Rayleigh filters. In some examples, the bandpass filter 40A includes a combination of a high-pass filter that passes frequencies above the high-pass cutoff point and a low-pass filter that passes frequencies below the low-pass cutoff point. In some cases, the bandpass filter 40A passes frequencies in the range between 100 kHz and 10,000 kHz.

[0052] Phase shifter 42A can be configured to shift the phase of a first electrical signal and a second electrical signal. Phase can be characterized as an instantaneous position on the waveform period of a periodic waveform. For example, the first electrical signal may comprise a periodic waveform representing a frequency component of the first electrical signal. The maximum peak of a sine wave may, for example, be at a different phase than the minimum peak or zero crossing of the sine wave. In some examples, phase shifter 42A may "delay" the first electrical signal by a certain time value to shift the time axis in which the frequency component of the first electrical signal oscillates, and delay the second electrical signal by a certain time value to shift the time axis in which the frequency component of the second electrical signal oscillates.

[0053] Electronic amplifier 44A amplifies the first electrical signal and / or the second electrical signal, increasing the amplitude of the first electrical signal by a gain factor. In other words, electronic amplifier 44A increases the power of the first and second electrical signals. By using electronic amplifier 44A to amplify the first and second electrical signals, circuit 14 can improve the ability of processing circuit 30 to analyze the first and second electrical signals and to use EOM 22A to modulate the light signal emitted by light-emitting device 12.

[0054] In some cases, electronic amplifier 44A may include a power amplifier, operational amplifier, or transistor amplifier, or any combination thereof. Additionally, in some examples, electronic amplifier 44A is configured to limit the voltage of the first and second electrical signals to a maximum voltage value. In other words, electronic amplifier 44A prevents the first and second electrical signals from exceeding the maximum voltage value, meaning that the first and second processed electrical signals generated by feedback unit 26A may not exceed the maximum voltage value.

[0055] In some examples, the first set of electrical signals can pass through the feedback unit 26A in the order of bandpass filter 40A, phase shifter 42A, electronic amplifier 44A, and driver 47A, such as... Figure 2 As shown. However, Figure 2 The order shown is not restrictive. The bandpass filter 40A, phase shifter 42A, and electronic amplifier 44A can be arranged to process the first and second electrical signals in any order.

[0056] Driver 47A can be configured to cause EOM 22A to modulate an optical signal to drive the mechanical resonance of the verification mass block assembly 16. For example, driver 47A can be configured to generate a mechanical resonance feedback signal that causes EOM 22A to operate near or at the mechanical resonance of the verification mass block assembly 16. For example, driver 47A can use a signal generator configured to generate the mechanical resonance of the verification mass block assembly 16. For example, driver 47A can be designed to use a first optical signal (e.g., a sensing optical signal) to sense the mechanical resonance at the verification mass block assembly 16, while system 10 can use a second optical signal (e.g., a driving optical signal) to drive the mechanical resonance at the verification mass block assembly 16.

[0057] Driver 47A can send a mechanical resonance feedback signal to frequency counter 28A. Frequency counter 28A can determine a first frequency value, and processing circuit 30 can determine a first acceleration value based on the first frequency value. Additionally, driver 47A can transmit the mechanical resonance feedback signal to EOM 22A, and EOM 22A can modulate an optical signal based on the mechanical resonance feedback signal generated from the sensed optical signal to drive a mechanical response and emit it from light-emitting device 12A. Thus, the verification mass block assembly 16, optical receiver 24A, bandpass filter 40A, phase shifter 42A, electronic amplifier 44A, driver 47A, EOM 22A, and frequency counter 28A form part of a first positive feedback loop that generates a first acceleration value associated with the object including system 10.

[0058] The components of feedback unit 26B (e.g., bandpass filter 40B, phase shifter 42B, electronic amplifier 44B, and driver 47B) can be substantially similar to the corresponding components of feedback unit 26A. Therefore, the second positive feedback loop can be substantially similar to the first positive feedback loop.

[0059] Figure 3 A conceptual diagram of a verification mass block assembly 16, comprising a verification mass block 50 suspended within a frame 52 via a first DETF structure 54, a second DETF structure 58, and a set of tethering elements 62A-62R, is shown according to one or more techniques of this disclosure. Figure 3 As shown, the verification mass assembly 16 includes: a verification mass 50, a frame 52, a first DETF structure 54 including a first pair of mechanical beams 56A and 56B (collectively referred to as the "first pair of mechanical beams 56"), a second DETF structure 58 including a second pair of mechanical beams 60A and 60B (collectively referred to as the "second pair of mechanical beams 60"), tethering members 62A to 62R (collectively referred to as the "tethering members 62"), a first distal serration 64, and a second distal serration 68. The verification mass assembly 16 is aligned with respect to the verification mass displacement axis 72 and the verification mass rest plane 74, as shown. Figure 3 As shown.

[0060] The verification mass block assembly 16 is a mechanical component of the electro-optical mechanical system 10. Since system 10 measures acceleration, which is the rate at which the velocity of an object changes over time, including the verification mass block assembly 16 may be advantageous, allowing acceleration to be measured based on a physical object such as the verification mass block 50. For example, system 10 including the verification mass block assembly 16 may be fixed to or included within an object. Thus, when the object accelerates with an acceleration value, the verification mass block assembly 16 may also accelerate with that acceleration value. Acceleration can affect the position of the verification mass block 50 within frame 52 relative to the verification mass block displacement axis 72 and the verification mass block rest plane 74. For example, a non-zero acceleration can cause the verification mass block 50 to displace along the verification mass block displacement axis 72 from the verification mass block rest plane 74. As described herein, if the verification mass block 50 “displaces,” the center of mass of the verification mass block 50 is displaced relative to frame 52. Increasing the acceleration metric can cause an increase in the displacement of the verification mass block 50 along the verification mass block displacement axis 72. In addition, reducing the acceleration metric value can lead to a decrease in the displacement of the verification mass block 50 along the verification mass block displacement axis 72.

[0061] In some examples, the verification mass block 50 takes the form of a patterned thin film having a mass in the range of 100 nanograms (ng) to 10,000 ng. Additionally, in some cases, the film has a thickness in the range of 1 nm to 5,000 nm. The verification mass block 50 can be suspended within the frame 52 along the verification mass block displacement axis 72 by a first DETF structure 54 and a second DETF structure 58 (collectively referred to as “DETF structures 54, 58”). The first DETF structure 54 and the second DETF structure 58 can each have a high level of stiffness. For example, the scaling factor of each of the first DETF structure 54 and the second DETF structure 58 can be in the range of 0.1 parts per million of gravitational equivalent (ppm / G) to 10 ppm / G. Thus, the verification mass block assembly 16 can include a very lightweight verification mass block 50 fixed by very rigid DETF structures 54, 58. Therefore, very high accelerations (e.g., 100,000 m / s²) are possible. 2 This can cause the verification mass block 50 to be displaced along the verification mass block displacement axis 72 by, for example, a very small displacement value. In some examples, the verification mass block 50 is displaced along the verification mass block displacement axis 72 by a displacement value of up to 100 nm.

[0062] To generate an acceleration value indicating the acceleration of the object to which the system 10 is fixed, the system 10 can use an optical signal to quantify the displacement of the verification mass 50 within the frame 52. To quantify the displacement of the verification mass 50, the system 10 can measure and analyze the mechanical properties of the DETF structures 54 and 58, such as the mechanical vibration frequency values ​​corresponding to the DETF structures 54 and 58. In fact, since the verification mass 50 is suspended by the DETF structures 54 and 58, the mechanical vibration frequency of the DETF structures 54 and 58 can be affected by the displacement of the verification mass 50. For example, the displacement of the verification mass 50 toward the first DETF structure 54 and away from the second DETF structure 58 can cause the verification mass 50 to exert a compressive force on the first DETF structure 54 and a tensile force on the second DETF structure 58. Such a compressive force can cause a decrease in the mechanical vibration frequency of the first DETF structure 54, and such a tensile force can cause an increase in the mechanical vibration force of the second DETF structure 58. In some examples, the change in the mechanical vibration frequency of the DETF structures 54, 58 can be proportional to the displacement of the verification mass 50 relative to the frame 52 in the direction of the verification mass displacement axis 72. In some examples, the system 10 can measure the change in the mechanical vibration frequency of the DETF structures 54, 58 by transmitting modulated optical signals via the DETF structures 54, 58.

[0063] The first DETF structure 54 may include, for example, a first pair of mechanical beams 56 spaced apart by a gap. The first pair of mechanical beams 56 may include photonic crystal mechanical beams configured to guide a first modulated optical signal when the first DETF structure 54 oscillates at a first mechanical vibration frequency. In some cases, the first modulated optical signal is emitted by a light-emitting device 12 (such as...). Figure 1 As shown, the first modulated optical signal is emitted, and the first modulated optical signal itself induces vibration in the first DETF structure 54. Furthermore, the vibration of the first DETF structure 54 can affect certain properties of the first modulated optical signal, causing the mechanical vibration frequency of the first DETF structure 54 to be reflected in the first modulated optical signal. Thus, the first modulated optical signal can cause mechanical vibration in the first DETF structure 54, enabling the system 10 to measure the mechanical vibration frequency of the first DETF structure 54 based on the first modulated optical signal.

[0064] Additionally, the second DETF structure 58 may include, for example, a second pair of mechanical beams 60 spaced apart by a gap. The second pair of mechanical beams 60 may include photonic crystal mechanical beams configured to guide a second modulated optical signal when the second DETF structure 58 oscillates at a second mechanical vibration frequency. In some cases, the second modulated optical signal is emitted by a light-emitting device 12 (such as...). Figure 1The second modulated optical signal is emitted, and the second modulated optical signal itself induces vibration in the second DETF structure 58. Furthermore, the vibration of the second DETF structure 58 can affect certain properties of the second modulated optical signal, causing the mechanical vibration frequency of the second DETF structure 58 to be reflected in the second modulated optical signal. Thus, the second modulated optical signal can cause mechanical vibration to occur in the second DETF structure 58, enabling the system 10 to measure the mechanical vibration frequency of the second DETF structure 58 based on the second modulated optical signal.

[0065] The verification mass 50 can be secured to the frame 52 by a tether 62. In some examples, the tether 62 can suspend the verification mass 50 in a verification mass rest plane 74 such that the center of mass of the verification mass 50 does not move relative to the frame 52 within the verification mass rest plane 74. The verification mass displacement axis 72 can represent a single axis (e.g., the x-axis) in Cartesian space, and the verification mass rest plane 74 can represent two axes (e.g., the y-axis and the z-axis) in Cartesian space. Because the tether 62 can restrict the displacement of the verification mass 50 relative to the verification mass rest plane 74, in some examples, the verification mass 50 can displace only along the verification mass displacement axis 72. The system 10 can measure acceleration based on the mechanical vibration frequency of the DETF structures 54, 58, where the mechanical vibration frequency is related to the amount of displacement of the verification mass 50 along the verification mass displacement axis 72. Thus, the acceleration determined by the system 10 can be the acceleration relative to the verification mass displacement axis 72.

[0066] The first DETF structure 54 may include a proximal end adjacent to the verification mass block 50 and a distal end separated from the frame 52 through a first gap 66. A first distal serration 64 may facilitate suspending the first DETF structure 54 within the frame 52 such that the first DETF structure 54 is perpendicular to the verification mass block's stationary plane 74. In some examples, the first distal serration 64 extends perpendicularly to the verification mass block's displacement axis 72 between the two sidewalls of the frame 52. Optical signals can be transmitted via a first optical fiber (in... Figure 3 (Not shown) travels through frame 52, and the optical signal is coupled to the first DETF structure 54 across the first gap 66.

[0067] The second DETF structure 58 may include a proximal end adjacent to the verification mass block 50 and a distal end separated from the frame 52 through a second gap 70. A second distal serration 68 may facilitate suspending the first DETF structure 58 within the frame 52 such that the second DETF structure 58 is perpendicular to the verification mass block's stationary plane 74. In some examples, the second distal serration 68 extends perpendicularly to the verification mass block's displacement axis 72 between the two sidewalls of the frame 52. Optical signals can be transmitted via a second optical fiber (in... Figure 3(Not shown) travels through frame 52, and the optical signal is coupled to the second DETF structure 58 across the second gap 70.

[0068] Figure 4 A conceptual diagram of a system 10 based on one or more technologies according to this disclosure is shown. Figure 4 The conceptual diagram includes components of the light-emitting device 12, circuitry 14, and verification mass block assembly 16. In some examples, the object may be fixed to the system 10. In some cases, the object may accelerate. The system 10, including the verification mass block assembly 16, may accelerate along with the object. When the verification mass block assembly 16 accelerates, the verification mass block 50 may displace relative to the frame 52. Figure 4 In the example shown, if the verification mass assembly 16 accelerates in direction 78, then the verification mass 50 displaces in direction 78. In some examples, direction 78 is opposite to the verification mass displacement axis (e.g., Figure 3 The verification mass block axis 72) is aligned.

[0069] When the verification mass 50 is displaced relative to the frame 52 in direction 78, the verification mass 50 applies a compressive force to the first DETF structure 54 and a tensile force to the second DETF structure 58. These forces can affect the mechanical vibration frequencies of the DETF structures 54 and 58, whereby the electro-optic modulators 22A and 22B induce mechanical vibrations in the first DETF structure 54 and the second DETF structure 58, respectively. For example, the compressive force applied to the first DETF structure 54 can cause a decrease in its mechanical vibration frequency, and the tensile force applied to the second DETF structure 58 can cause an increase in its mechanical vibration frequency.

[0070] The light-emitting device 12 can emit a driving optical signal to the EOM 22 and a sensing optical signal to the verification mass block assembly 16. For example, each of the light-emitting devices 12 can be configured to generate a sensing optical signal that interacts with the verification mass block assembly 16, and one or more of phase modulation or frequency modulation applied to the mechanical vibration in the verification mass block assembly 16 in response to the interaction with the verification mass block assembly 16; and generate a driving optical signal that is modulated by the EOM 22 and excites the mechanical vibration in the verification mass block assembly 16. In this way, the driving optical signal can provide driving modulation at the verification mass block assembly, and the feedback units 26A, 26B can use the sensing optical signal that interacts with the verification mass block assembly 16, while the driving optical signal drives the mechanical vibration frequency at the verification mass block assembly 16.

[0071] Subsequently, EOM 22A and EOM 22B can modulate corresponding driving optical signals based on the processed electrical signals generated by feedback unit 26A and feedback unit 26B, respectively. Thus, EOM 22A can generate a first modulated optical signal for driving a mechanical response in the verification mass block assembly 16, and EOM 22B can generate a second modulated optical signal for driving a mechanical response in the verification mass block assembly 16. For example, EOM 22A can send the first modulated optical signal to the verification mass block assembly 16. The first modulated optical signal can cross frame 52. In some examples, frame 52 includes a hole or another opening bridged by a first optical fiber allowing the first modulated optical signal to pass through. Alternatively, the first modulated optical signal can be coupled across a first gap 66 to the first DETF structure 54. The first modulated optical signal for driving a mechanical response in the verification mass block assembly 16 can propagate through the first DETF structure 54, thereby inducing mechanical vibration in the first DETF structure 54. In some examples, the first modulated optical signal propagates along mechanical beam 56A toward the verification quality block 50 along the length of the first DETF structure 54, and then propagates along mechanical beam 56B away from the verification quality block 50 along the length of the first DETF structure 54.

[0072] Similarly, a first sensed light signal can cross frame 52. The first sensed light signal can be coupled to the first DETF structure 54 across the first gap 66. The first sensed light signal can propagate through the first DETF structure 54 to apply mechanical vibrations within the first DETF structure 54 to the first sensed light signal. In some examples, the first sensed light signal propagates along the mechanical beam 56A toward the verification mass block 50 along the length of the first DETF structure 54, and then propagates along the mechanical beam 56B away from the verification mass block 50. In some examples, the first sensed light signal propagates along the mechanical beam 56B toward the verification mass block 50 along the length of the first DETF structure 54, and then propagates along the mechanical beam 56A away from the verification mass block 50 along the length of the first DETF structure 54. In any case, by propagating the length of the first DETF structure 54, the first sensed light signal can retain information indicative of the mechanical properties of the first DETF structure 54 (e.g., the frequency of mechanical vibrations). After the first sensed light signal propagates through the first DETF structure 54, the first sensed light signal can leave the verification mass block assembly 16 via the first optical fiber of the first gap 66 and the frame 52.

[0073] After leaving the verification mass block assembly 16, a first sensed optical signal, which may include fluctuations in amplitude and / or frequency, can reach the optical receiver 24A. The optical receiver 24A converts the first modulated optical signal into a set of electrical signals for suppressing noise in the light-emitting device 12A and for driving the EOM 22A to the mechanical resonance of the verification mass block assembly 16. The frequency counter 28A can determine a first frequency value corresponding to the first processed electrical signal, wherein the first frequency value indicates the mechanical vibration frequency of the first DETF structure 54. The processing circuit 30 can subtract a baseline frequency value from the first frequency value to obtain a first frequency difference, and calculate a first acceleration value based on the first frequency difference. The EOM 22A can use the first processed electrical signal to modulate the optical signal emitted by the light-emitting device 12.

[0074] For example, EOM 22B can send a second modulated optical signal to the verification quality block assembly 16. The second modulated optical signal can cross a frame 52. In some examples, the frame 52 includes a hole or another opening bridged by a second optical fiber that allows the second modulated optical signal to pass through. Additionally, the second modulated optical signal can be coupled to a second DETF structure 58 across a second gap 70. The second modulated optical signal can propagate through the second DETF structure 58, thereby inducing mechanical vibration within the second DETF structure 58. In some examples, the second modulated optical signal propagates along the mechanical beam 60A toward the verification quality block 50 along the length of the second DETF structure 58, and then propagates along the mechanical beam 60B away from the verification quality block 50 along the length of the second DETF structure 58. In some examples, the second modulated optical signal propagates along the mechanical beam 60B toward the verification quality block 50 along the length of the second DETF structure 58, and then propagates along the mechanical beam 60A away from the verification quality block 50 along the length of the second DETF structure 58.

[0075] Similarly, the second sensing light signal can cross frame 52. Additionally, the second sensing light signal can be coupled to the second DETF structure 58 across the second gap 70. The second sensing light signal can propagate through the second DETF structure 58 to apply mechanical vibrations in the first DETF structure 28 to the second sensing light signal. In some examples, the second sensing light signal propagates along the mechanical beam 60A toward the verification mass block 50 along the length of the second DETF structure 58, and then propagates along the mechanical beam 60B away from the verification mass block 50. In some examples, the second sensing light signal propagates along the mechanical beam 60B toward the verification mass block 50 along the length of the second DETF structure 58, and then propagates along the mechanical beam 60A away from the verification mass block 50 along the length of the second DETF structure 58. In any case, by propagating the length of the second DETF structure 58, the second sensing light signal can retain information indicative of the mechanical properties of the second DETF structure 58 (e.g., the frequency of mechanical vibrations). After the second sensing light signal propagates through the second DETF structure 58, the second sensing light signal can leave the verification mass block assembly 16 via the second optical fiber of the second gap 70 and the frame 52.

[0076] After leaving the verification mass block assembly 16, a second sensed optical signal, which may include thermal noise, can reach the photoreceiver 24B. The photoreceiver 24B converts the second modulated optical signal into a set of electrical signals for suppressing noise in the light-emitting device 12B, and a second electrical signal for driving the EOM 22B to the mechanical resonance of the verification mass block assembly 16. The frequency counter 28B can determine a second frequency value corresponding to the second processed electrical signal, wherein the second frequency value indicates the mechanical vibration frequency of the second DETF structure 58. The processing circuit 30 can subtract a baseline frequency value from the second frequency value to obtain a second frequency difference, and calculate a second acceleration value based on the second frequency difference. The EOM 22B can use the second processed electrical signal to modulate the optical signal emitted by the light-emitting device 12.

[0077] Figure 5 Additional aspects of system 10 according to one or more technologies of this disclosure are shown. For example, Figure 5 A first DETF structure 54 is shown, comprising a first pair of mechanical beams 56. A light signal emitted by the light-emitting device 12 can induce a force between the first pair of mechanical beams 56, and this force can be simulated by a spring force. Figure 5 The diagram shows the spring force (502) provided by the laser in the optical zipper between the photonic crystal mechanical beams 56A and 56B of the DETF structure 54, the perspective view depicting the vibration modes of the beams in the optical zipper together in a common direction (504), and the perspective view depicting the vibration modes of the beams in the optical "zipper" in opposite directions of oscillation (506).

[0078] Figure 6 A conceptual diagram illustrating an exemplary technique for reducing drive feedthrough in an optomechanical device according to one or more techniques of the present invention. Figure 6 Referenced for illustrative purposes only Figures 1 to 5 Discussion. As shown in the figure, an electro-optical system 610, which may be an example of system 10, may include a light-emitting device 612, an intensity stabilizer 617, an EOM 622, an optical circulator 672, a verification mass block assembly (also referred to herein as “device 616”) 616, and a feedback unit 626.

[0079] The light-emitting device 612 may include a sensing laser 611 and a driving laser 613. The sensing laser 611 and the driving laser 613 are capable of outputting at different intensities. For example, the sensing laser 611 may be configured to generate a sensing light signal that interacts with the verification mass block assembly, and to apply one or more of phase modulation and frequency modulation of the mechanical vibrations in the verification mass block assembly in response to the interaction with the verification mass block assembly. Conversely, the driving laser 613 may be configured to generate a driving light signal that excites mechanical vibrations in the verification mass block assembly 616. For example, the driving laser 613 may be configured to generate a driving light signal having an amplitude greater than ten times the amplitude of the sensing light signal output by the sensing laser 611.

[0080] The sensing laser 611 and the driving laser 613 can be two intensity-stabilized lasers, each tuned to slightly different frequencies. For example, the sensing laser 611 can be tuned to vopt + Γ / 4, and the driving laser 613 can be tuned to vopt - Γ / 4, where vopt is the optical resonant frequency and Γ is the FWHM. In another example, the driving laser 613 can be tuned to vopt + Γ / 4, and the sensing laser 611 can be tuned to vopt - Γ / 4.

[0081] The sensing laser 611 and the driving laser 613 can each be tuned to slightly different frequencies offset from the optical resonant frequency. For example, the sensing laser 611 can be tuned to vopt + Γ / 4 + Δ, and the driving laser 613 can be tuned to vopt + Γ / 4 - Δ, where Δ is a resolvable frequency difference greater than the mechanical frequency. In some examples, the driving laser 613 can be tuned to vopt + Γ / 4 + Δ, and the sensing laser 611 can be tuned to vopt + Γ / 4 - Δ. In some examples, the sensing laser 611 can be tuned to vopt - Γ / 4 + Δ, and the driving laser 613 can be tuned to vopt - Γ / 4 - Δ. In some examples, the driving laser 613 can be tuned to vopt - Γ / 4 + Δ, and the sensing laser 611 can be tuned to vopt - Γ / 4 - Δ, where vopt is the optical resonant frequency and Γ is the FWHM.

[0082] Intensity stabilizer 617 can be configured to adjust the intensity of the optical signal output from sensing laser 611 to a predetermined intensity value. For example, the optical signal output from sensing laser 611 passes through a variable optical attenuator (VOA) 671, which can be configured to attenuate a portion of the optical signal. Tap 673 can be configured to output a first portion of the optical signal from VOA 671 to photodiode 675 and a second portion of the optical signal from VOA 671 to optical circulator 672. In this example, intensity servo 677 can be configured to use the electrical signal output from photodiode 675 to stabilize the overall light level of the optical signal.

[0083] Intensity stabilizer 617 can be configured to adjust the intensity of the optical signal output by drive laser 613 to a predetermined intensity value. For example, the optical signal output by drive laser 613 passes through VOA 686, and the variable optical attenuator can be configured to attenuate a portion of the optical signal. Tap 676 can be configured to output a first portion of the optical signal output from VOA 686 to photodiode 674, and a second portion of the optical signal output from VOA 686 to optical EOM 622. In this example, intensity servo 677 can be configured to use the electrical signal output by photodiode 674 to stabilize the overall light level of the optical signal.

[0084] The intensity servo 677 can be configured to adjust the intensity of the optical signal output by the sensing laser 611 to a first predetermined optical intensity value before outputting the optical signal to the verification mass block assembly 616. In some examples, the intensity servo 677 can be configured to adjust the intensity of the optical signal output by the driving laser 613 to a second predetermined optical intensity value before outputting the optical signal to the verification mass block assembly 616. In some examples, the second predetermined optical intensity value can be greater than the first predetermined optical intensity value (e.g., greater than 10 times, greater than 20 times, etc.).

[0085] EOM 622 can be configured to modulate the optical signal (e.g., a drive optical signal) output from tap 676 to the optical resonance of verification mass block assembly 616. For example, EOM 622 can be configured to drive the optical signal output from tap 676 to the peak optical resonance of verification mass block assembly 616 using an electrical signal generated by feedback unit 626.

[0086] Optical circulator 672 can be configured to output an optical signal (e.g., a drive optical signal) from EOM 622 and an optical signal (e.g., a sense optical signal) from tap 673 to mass block assembly 616, and to receive an optical signal reflected from verification mass block assembly 616. For example, an optical signal output from sense laser 611 and stabilized by intensity stabilizer 617 and an optical signal output from driver laser 613 and stabilized by intensity stabilizer 617 are combined to generate a combined optical signal, which enters port "1" of optical circulator 672 and exits from port "2" of optical circulator 672, wherein the modulated optical signal interacts with verification mass block assembly 616 (e.g., a zipper cavity measured in reflection).

[0087] After passing through port "2" of the optical circulator 672, the optical signal is output from port "3" of the optical circulator 672 to the feedback unit 626. The feedback unit 626 can be configured to use the optical signal generated by the verification mass block assembly 616 to drive the mechanical response of the verification mass block assembly 616.

[0088] As shown in the figure, the feedback unit 626 may include a dichroic mirror 684, photodiodes 624A and 624B (collectively referred to as "photodiode 624" (photodiode 624A is optional)), a bandpass filter (BPF) 620, a frequency servo and data acquisition module 628, and a signal generator 646. The frequency servo and data acquisition module 628 may be an example of drivers 47A and 47B.

[0089] The dichroic mirror 648 can be configured to separate driving and sensing light signals at different wavelengths. For example, the dichroic mirror 648 can be configured to output a first light signal corresponding to vopt+Γ / 4 and a second light signal corresponding to vopt-Γ / 4, or output a first light signal corresponding to vopt-Γ / 4 and a second light signal corresponding to vopt+Γ / 4. In some examples, the dichroic mirror 648 can be configured to output a first light signal corresponding to vopt+Γ / 4+Δ and a second light signal corresponding to vopt+Γ / 4-Δ, or output a first light signal corresponding to vopt+Γ / 4-Δ and a second light signal corresponding to vopt+Γ / 4+Δ. In some examples, the dichroic mirror 648 can be configured to output a first light signal corresponding to vopt-Γ / 4+Δ and a second light signal corresponding to vopt-Γ / 4-Δ, or output a first light signal corresponding to vopt-Γ / 4-Δ and a second light signal corresponding to vopt-Γ / 4+Δ.

[0090] Photodiode 624A can be configured to convert a first portion of the optical signal output by dichroic mirror 684 into a first electrical signal. Similarly, photodiode 624B can be configured to convert a second portion of the optical signal output by dichroic mirror 684 into a second electrical signal.

[0091] The BPF 620 can be configured to transmit electrical signals in a frequency band near the mechanical frequency of the verification mass block assembly 616. For example, the BPF 620 can be configured to transmit electrical signals in a frequency band of approximately 1 MHz.

[0092] The frequency servo and data acquisition module 628 can be configured to drive the EOM 622 to the mechanical resonance of the verification mass block assembly 616 via the optical signal output from tap 676. For example, the signal generator 646 can be configured to generate a mechanical resonance feedback signal that causes the EOM 622 to operate near or at the mechanical resonance of the verification mass block assembly 616. For example, the signal generator 646 can be used to generate the mechanical resonance feedback signal to set it to the mechanical resonance of the verification mass block assembly 616. The frequency servo and data acquisition module 628 can determine a first frequency value to determine an acceleration value for the verification mass block assembly 616. The frequency servo and data acquisition module 628 can be configured to use the mechanical resonance feedback signal to measure the acceleration at the verification mass block assembly 616.

[0093] According to the technique described herein, the driving laser 613 can be configured to generate an optical signal passing through an EOM 622, at which the light is modulated at a mechanical resonant frequency. The optical signal output from the driving laser 613 is combined with an optical signal output from a sensing laser 611, and the combination of the optical signals output from the driving laser 613 and the sensing laser 611 passes through an optical circulator 672 to a verification mass block assembly 616 (e.g., an optomechanical accelerometer, which may include a photonic zipper cavity). The optical signal output from the driving laser 613 interacts with the verification mass block assembly 616 and excites mechanical vibrations within the verification mass block assembly 616. The optical signal output from the sensing laser 611 interacts with the verification mass block assembly 616, and due to the mechanical vibrations excited by the optical signal output from the driving laser 613, phase and / or frequency modulation is applied to the optical signal, and information about the frequency and phase of the mechanical vibrations is also carried, including, for example, one or more shifts in the mechanical resonance caused by the acceleration of the verification mass block assembly 616. Both optical signals generated by the sensing laser 611 and the driving laser 613 exit the verification mass block assembly 616 (either by reflection or transmission). In the case of reflection, the optical signal is returned to the dichroic mirror 684 with sufficient frequency selectivity via the optical circulator 672 to separate the driving and sensing optical fields at different wavelengths. The photodiode 624B, BPF 620, frequency servo and data acquisition module 628, and signal generator 646 can be configured to perform subsequent detection and processing only on the optical signal output sensing laser 611, thereby helping to provide acceleration measurements uncontaminated by feedthrough. In closed-loop oscillator operation, the feedback unit 626 can be configured to electronically detect and process the optical signal from the sensing laser 611 and the control signal generator 646 to drive the EOM 622 to create a modulated driving field. In some examples (e.g., open-loop, scanning, or phase-locked loop), the feedback unit 626 can be configured to derive the signal to be applied to the EOM 622 from a separate frequency synthesizer.

[0094] Figure 7 A conceptual diagram of an exemplary first optical response of a first optical frequency component and a second optical frequency component according to one or more techniques of this disclosure. Figure 7 Referenced for illustrative purposes only Figures 1-6 discuss. Figure 7 The horizontal axis (e.g., the horizontal axis) represents the laser wavelength in nanometers (nm), and Figure 7 The ordinate axis (e.g., the vertical axis) represents normalized reflection 702. In Figure 7In the example, this might be useful for narrow optical resonances, where a laser (e.g., a driving laser or a sensing laser) is set to a first frequency 704 and tuned to vopt+Γ / 4, and another laser (e.g., a sensing laser or a driving laser) is tuned to vopt-F / 4, where vopt is the optical resonance frequency and Γ is the FWHM.

[0095] Figure 8 A conceptual diagram of an exemplary second optical response of a first optical frequency component and a second optical frequency component according to one or more techniques of this disclosure. Figure 8 Referenced for illustrative purposes only Figures 1-7 discuss. Figure 8 The horizontal axis (e.g., the horizontal axis) represents the laser wavelength in nanometers (nm), and Figure 8 The ordinate axis (e.g., the vertical axis) represents normalized reflection 802. In Figure 8 In one example, a laser (e.g., a driving laser or a sensing laser) can be set to a first frequency 804 and tuned to vopt + Γ / 4 - Δ, while another laser (e.g., a sensing laser or a driving laser) is tuned to vopt + Γ / 4 + Δ, where vopt is the optical resonant frequency and Γ is the FWHM. In some examples, a laser (e.g., a driving laser or a sensing laser) can be set to a first frequency and tuned to vopt - Γ / 4 - Δ, while another laser (e.g., a sensing laser or a driving laser) is tuned to vopt - Γ / 4 + Δ, where vopt is the optical resonant frequency and Γ is the FWHM.

[0096] Figure 9 A conceptual diagram illustrating an example of applying one or more techniques according to this disclosure to verify optical signals of a mass block assembly. Figure 9 Referenced for illustrative purposes only Figures 1-8 discuss. Figure 9 The horizontal axis (e.g., the horizontal axis) represents the laser wavelength in nanometers (nm), and Figure 9 The ordinate axis (e.g., the vertical axis) represents normalized reflection 902. In Figure 9 In the example, optical signal 912 corresponds to the optical signal output by the driving laser 613 before being output to the optical circulator 672 and after being processed by the intensity stabilizer 617, and optical signal 914 corresponds to the optical signal output by the sensing laser 611 before being output to the optical circulator 672 and after being processed by the intensity stabilizer 617.

[0097] As shown in the figure, optical signal 912 includes a center frequency with harmful "feedpass" modulation, which can be represented as a lower sideband and an upper sideband. However, optical signal 914 includes a center frequency with little or no harmful feedpass modulation.

[0098] Figure 10 For the verification mass block component in response to one or more techniques according to this disclosure Figure 9 A conceptual diagram illustrating an example of an optical signal that is reflected and output as a light signal. Figure 10 Referenced for illustrative purposes only Figures 1-9 discuss. Figure 10 The horizontal axis (e.g., the horizontal axis) represents the laser wavelength in nanometers (nm), and Figure 10 The ordinate axis (e.g., the vertical axis) represents normalized reflection 1002. In Figure 10 In the example, optical signal 1012 corresponds to the optical signal output by the driving laser 613 before being output to the dichroic mirror 684 and after being output by the optical circulator 672, and optical signal 1014 corresponds to the optical signal output by the sensing laser 611 before being output to the dichroic mirror 684 and after being output by the optical circulator 672.

[0099] As shown in the figure, after interacting with the verification quality block assembly 616, the optical signal 1012 includes a center frequency with harmful feedpass modulation. Therefore, although the optical signal 1012 includes the effects of the interaction with the verification quality block assembly 616, these effects are obscured by the harmful feedpass modulation associated with the driving mechanical response at the verification quality block assembly. Conversely, the optical signal 1014 includes a center frequency with little or no harmful feedpass modulation. Thus, compared to the optical signal 1012, the optical signal 1014 more clearly includes the effects of the interaction with the verification quality block assembly 616, which can be considered as additional sidebands.

[0100] Figure 11 For the purpose of one or more technologies according to this disclosure Figure 10 A conceptual diagram illustrating an example of a filtered optical signal obtained by filtering an optical signal. Figure 11 Referenced for illustrative purposes only Figures 1-10 discuss. Figure 11 The horizontal axis (e.g., the horizontal axis) represents the laser wavelength in nanometers (nm), and Figure 11 The ordinate axis (e.g., the vertical axis) represents the normalized reflection 1102. In Figure 11 In the example, optical signal 1114 corresponds to the optical signal output by sensing laser 611 after being processed by dichroic mirror 684.

[0101] Figure 12 A flowchart illustrating an example of reducing drive feedthrough in an optomechanical device according to one or more techniques of this disclosure. Figure 12 Referenced for illustrative purposes only Figures 1-11 describe.

[0102] Light-emitting device 612 generates a first optical signal and a second optical signal (1202). In some examples, the first optical signal includes a frequency different from that of the second optical signal. EOM 622 modulates the second optical signal (1204). Optical circulator 672 outputs the first and second optical signals to the verification mass block assembly (1206). Dichroic mirror 684 generates a filtered optical signal (1208) corresponding to the response of the verification mass block assembly to the first optical signal but not the second optical signal. Photodiode 624B generates an electrical signal (1210) based on the filtered optical signal. In some examples, EOM 622 modulates the second optical signal based on the electrical signal.

[0103] The frequency servo and data acquisition module 628 may optionally generate an acceleration indication (1212) at the verification mass block assembly based on an electrical signal. However, in other examples, the circuit may generate other indications, such as velocity, vibration, rotation, position, or another indication at a mechanical component.

[0104] The optomechanical devices described herein may include analog-only circuitry, digital-only circuitry, or a combination of analog and digital circuitry. Digital circuitry may include, for example, a microcontroller on a single integrated circuit, comprising a processor core, memory, inputs, and outputs. For example, the digital circuitry of the optomechanical devices described herein may include one or more processors, including one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, and any combination of such components. The terms "processor" or "processing circuitry" may generally refer to any of the aforementioned analog and / or digital circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.

[0105] The techniques disclosed herein can be implemented in various devices or apparatuses including integrated circuits (ICs) or a set of ICs (e.g., chipsets). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to perform the disclosed techniques, but they do not necessarily need to be implemented by different hardware units. Instead, various units may be combined with or provided by a collection of interoperable hardware units (including one or more processors as described above) incorporating suitable software and / or firmware.

Claims

1. An optomechanical device for generating and detecting optical signals, the device comprising: Verify the quality block component; The laser device is configured to generate a first optical signal and a second optical signal; as well as The circuit is configured as follows: The second optical signal is modulated using an electro-optic modulator (EOM). The first optical signal and the second optical signal are output to the verification quality block component; Generate a filtered optical signal corresponding to the response of the verification quality block component to the first optical signal instead of the second optical signal; as well as An electrical signal is generated based on the filtered optical signal, wherein the EOM modulates the second optical signal based on the electrical signal. The laser device includes: A sensing laser device is configured to generate a first optical signal; and The driving laser device is configured to generate a second optical signal, and The sensing laser device is configured to generate the first optical signal at a frequency corresponding to the optical resonance of the verification mass block assembly plus one-quarter of the full width at half maximum (FWHM) of the optical resonance of the verification mass block assembly, and the driving laser device is configured to generate the second optical signal at a frequency corresponding to the optical resonance of the verification mass block assembly minus one-quarter of the FWHM of the optical resonance of the verification mass block assembly; or The sensing laser device is configured to generate the first optical signal at a frequency corresponding to one-quarter of the FWHM of the optical resonance of the verification mass block assembly minus the FWHM of the optical resonance of the verification mass block assembly, and the driving laser device is configured to generate the second optical signal at a frequency corresponding to one-quarter of the FWHM of the optical resonance of the verification mass block assembly plus the FWHM of the optical resonance of the verification mass block assembly; or The sensing laser device is configured to generate the first optical signal at a frequency corresponding to the sum of the optical resonance of the verification mass block assembly plus one-quarter of the FWHM of the optical resonance of the verification mass block assembly and the offset, and the driving laser device is configured to generate the second optical signal at a frequency corresponding to the optical resonance of the verification mass block assembly plus the result of subtracting the offset from one-quarter of the FWHM of the optical resonance of the verification mass block assembly; or The sensing laser device is configured to generate the first optical signal at a frequency corresponding to the optical resonance of the verification mass block assembly plus one-quarter of the FWHM of the optical resonance of the verification mass block assembly minus the offset, and the driving laser device is configured to generate the second optical signal at a frequency corresponding to the sum of the optical resonance of the verification mass block assembly minus one-quarter of the FWHM of the optical resonance of the verification mass block assembly and the offset.

2. The optomechanical device according to claim 1, wherein the circuit is configured as follows: An acceleration indication is generated at the verification mass block assembly based on the electrical signal.

3. The optomechanical device according to claim 1, The sensing laser device is configured to generate the first optical signal, such that the first optical signal interacts with the verification mass block assembly, and, in response to the interaction with the verification mass block assembly, one or more of a phase modulation of the mechanical vibration in the verification mass block assembly and a frequency modulation of the mechanical vibration in the verification mass block assembly are applied; and The driving laser device is configured to generate the second optical signal, such that the second optical signal excites mechanical vibration in the verification mass block assembly.

4. The optomechanical device according to claim 1, wherein the driving laser device is configured to generate a second optical signal with an amplitude greater than ten times the amplitude of the first optical signal.

5. The optomechanical device of claim 1, wherein the offset is a frequency greater than the mechanical frequency of the verification mass block assembly.

6. The optomechanical device of claim 1, wherein the circuitry includes an optical circulator, wherein, for outputting the first optical signal and the second optical signal to the verification mass block assembly, the circuitry is configured to: The first optical signal and the second optical signal are combined into a combined optical signal; The combined optical signal is output to the optical circulator, wherein the optical circulator outputs the combined optical signal to the verification quality block component and receives responses to the first optical signal and the second optical signal from the verification quality block component.

7. The optomechanical device of claim 6, wherein the circuitry includes a filter, the filter being configured to: Using the responses from the verification quality block component to the first and second optical signals, a filtered optical signal corresponding to the response of the verification quality block component to the first optical signal but not the second optical signal is generated.

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