A method and system for detecting resonance wavelength drift of a MEMS microcavity device

Abstract

The present application relates to the technical field of device testing, and in particular to a MEMS microcavity device resonance wavelength drift detection method and system, comprising: adding an alternating current of a preset frequency to the driving current of a laser to generate a laser signal to irradiate a microcavity device, and inputting a device output signal into a lock-in amplifier to output a direct current voltage signal. The driving current is adjusted in real time to make the amplitude of the direct current voltage signal less than a preset threshold, thereby determining the resonance wavelength. Subsequently, the working temperature of the microcavity device is changed, and according to the correlation between the resonance wavelength and the working temperature, the amplitude of the alternating current added at each temperature point is adaptively adjusted. Finally, the wavelength drift detection is completed based on the resonance wavelengths determined at all working temperatures. The present application effectively suppresses the interference of complex noise in the full temperature range on the detection process, and significantly improves the robustness and precision of the resonance wavelength drift detection.

Description

Technical Field

[0001] This invention relates to the field of device testing technology, and specifically to a method and system for detecting the resonant wavelength drift of MEMS microcavity devices. Background Technology

[0002] MEMS microcavity devices, with their high quality factor and high energy localization capability, have broad application prospects in the field of smart sensors. Examples include optical microcavity gyroscopes / accelerometers or biological / chemical sensors fabricated by changing a specific physical parameter (such as optical path length or resonant frequency) of the optical microcavity. The core performance indicator of this device—the resonant wavelength—is highly susceptible to drift caused by environmental factors such as temperature. Therefore, accurate and reliable detection of the resonant wavelength drift characteristic is not only crucial for evaluating device stability but also fundamental to realizing highly sensitive smart sensing applications.

[0003] Currently, wavelength locking based on lock-in amplification technology is the mainstream method for detecting resonant wavelengths. However, this method lacks robustness and accuracy under complex noise environments. During operation, MEMS microcavity devices generate unpredictable operating noise due to vibration, stress, and adsorption effects, and the noise characteristics change with operating temperature. This noise severely interferes with the locking process of the lock-in amplifier, making it difficult to accurately distinguish between the true wavelength drift caused by physical effects and random fluctuations caused by noise, thus impairing the resolution and accuracy of the measurement. Summary of the Invention

[0004] To address the issues of resolution and accuracy in detecting resonant wavelength drift caused by complex noise interference across the entire temperature range, this invention provides a method and system for detecting resonant wavelength drift in MEMS microcavity devices.

[0005] The present invention provides a method and system for detecting resonant wavelength drift in MEMS microcavity devices, which adopts the following technical solution: One embodiment of the present invention provides a method for detecting the resonant wavelength drift of a MEMS microcavity device, the method comprising the following steps: A laser is driven by adding an alternating current of a preset frequency to the driving current. The laser signal generated by the laser is used to irradiate a microcavity device, and the output signal of the microcavity device is input to a lock-in amplifier, which outputs a DC voltage signal. The drive current is controlled in real time. When the amplitude of the DC voltage signal is less than a preset voltage threshold, the resonant wavelength of the microcavity device is first determined by the wavelength of the laser signal generated by the laser, and then the operating temperature of the microcavity device is changed. In the process of real-time control of the drive current, the amplitude of the alternating current added at each operating temperature is adjusted according to the correlation between the determined resonant wavelength and the operating temperature. Wavelength drift detection is performed based on the resonant wavelength determined at all operating temperatures.

[0006] Preferably, the process of changing the operating temperature of the microcavity device consists of a first temperature change process and a second temperature change process. The specific steps for obtaining the first and second temperature change processes are as follows: Starting from the lower limit of the operating temperature, after each determination of the resonant wavelength, the operating temperature is increased by a preset first step length. After each increase in the operating temperature, the resonant wavelength is determined again until the operating temperature is greater than the upper limit of the operating temperature. This process of increasing the operating temperature is called the first temperature change process. When the operating temperature exceeds the upper limit of the operating temperature, the operating temperature is gradually decreased starting from the upper limit, with a preset first step length. After each decrease in the operating temperature, a resonant wavelength is determined, until the operating temperature is lower than the lower limit of the operating temperature, at which point the temperature change stops. This process of decreasing the operating temperature is called the second temperature change process.

[0007] Preferably, the specific steps of adjusting the amplitude of the added alternating current at each operating temperature based on the determined correlation between the resonant wavelength and the operating temperature are as follows: During the first temperature change process, the amplitude of the alternating current remains constant; after the first temperature change process ends, the resonant wavelength determined at each operating temperature during the first temperature change process is recorded as the first wavelength; during the second temperature change process, any operating temperature after the change is marked as the target temperature. From all the working temperatures during the first temperature change process, obtain the neighborhood temperature sequence of the target temperature; the correlation between the first wavelength sequence determined at all working temperatures in the neighborhood temperature sequence and the neighborhood temperature sequence at different sampling scales is denoted as the wavelength resolution coefficient and wavelength accuracy coefficient of the target temperature, respectively. Based on the relationship between the wavelength resolution coefficient and the wavelength accuracy coefficient at the target temperature, the amplitude of the alternating current added at the target temperature is adjusted, wherein the adjustment range of the amplitude is positively correlated with the difference between the wavelength resolution coefficient and the wavelength accuracy coefficient.

[0008] Preferably, adjusting the amplitude of the alternating current added at the target temperature based on the relationship between the wavelength resolution coefficient and the wavelength accuracy coefficient at the target temperature includes the following specific steps: The absolute value of the difference between the wavelength resolution coefficient and the wavelength accuracy coefficient is used as the adjustment range when adjusting the amplitude of the alternating current; wherein, when the wavelength resolution coefficient is less than the wavelength accuracy coefficient, the amplitude of the alternating current is increased; when the wavelength resolution coefficient is greater than the wavelength accuracy coefficient, the amplitude of the alternating current is decreased; when the wavelength resolution coefficient is equal to the wavelength accuracy coefficient, the amplitude of the alternating current is not changed.

[0009] Preferably, when the wavelength resolution coefficient is equal to the wavelength accuracy coefficient, the voltage threshold is reduced, and the amount of reduction in the voltage threshold is negatively correlated with the mean of the wavelength resolution coefficient and the wavelength accuracy coefficient of the target temperature.

[0010] Preferably, the specific steps for obtaining the wavelength resolution coefficient and wavelength accuracy coefficient of the target temperature are as follows: From all the working temperatures during the first temperature change process, obtain the n working temperatures with the smallest difference from the target temperature, and denot them as the first neighborhood temperature sequence of the target temperature; the first wavelength determined at all working temperatures in the first neighborhood temperature sequence constitutes the first wavelength sequence; the first change correlation between the first wavelength sequence and the first neighborhood temperature sequence is denoted as the wavelength resolution coefficient of the target temperature. The m working temperatures with the smallest difference from the target temperature are obtained and denoted as the second neighborhood temperature sequence of the target temperature. The first wavelength determined at all working temperatures in the second neighborhood temperature sequence constitutes the second wavelength sequence. The second change correlation between the downsampling result of the second wavelength sequence and the downsampling result of the second neighborhood temperature sequence is denoted as the wavelength accuracy coefficient of the target temperature. Where m and n are preset values, and m is greater than n.

[0011] Preferably, the wavelength drift detection based on the resonant wavelength determined at all operating temperatures includes the following specific steps: For the target temperature, the resonant wavelength determined at the target temperature during the first temperature change process is denoted as the first measurement wavelength, and the resonant wavelength determined at the target temperature during the second temperature change process is denoted as the second measurement wavelength. The average value of the wavelength resolution coefficient and wavelength accuracy coefficient at the target temperature is recorded as the first fusion weight. The first and second measurement wavelengths are fused using the first and second fusion weights to obtain the fused resonant wavelength at the target temperature. After the second temperature change process is completed, the fused resonant wavelengths at all operating temperatures are obtained. Wavelength drift detection is performed based on the fused resonant wavelengths determined at all operating temperatures. The second fusion weight is a preset value that is greater than the first fusion weight.

[0012] Preferably, the wavelength drift detection based on the fusion resonance wavelength determined at all operating temperatures includes the following specific steps: The fusion resonance wavelength at the preset operating temperature is taken as the standard resonance wavelength; the difference between the fusion resonance wavelength determined at all operating temperatures and the standard resonance wavelength is recorded as the wavelength drift detection result at all operating temperatures.

[0013] Preferably, the specific steps for determining the resonant wavelength of the microcavity device by determining the wavelength of the laser signal generated by the laser are as follows: Different preset constant currents are input into the laser, and the wavelength of the laser signal output by the laser is measured under each constant current. All constant currents are used as the abscissa, and the wavelength of the laser signal corresponding to each constant current is used as the ordinate. The coordinate points formed by all the abscissa and ordinate are connected by a straight line to obtain the curve of the laser output wavelength changing with the current. When the amplitude of the DC voltage signal is less than the preset voltage threshold, the drive current after control is read, and the ordinate corresponding to the drive current is obtained on the curve. This ordinate is used as the resonant wavelength of the microcavity device.

[0014] Another embodiment of the present invention provides a MEMS microcavity device resonant wavelength drift detection system. The system includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor runs the computer program, it implements all the steps of the above-described MEMS microcavity device resonant wavelength drift detection method.

[0015] The beneficial effects of the technical solution of the present invention are: This invention overcomes the limitations of fixed detection parameters: In traditional lock-in amplification detection technology, the amplitude of the modulation signal is usually preset to a fixed value. However, the resonant peak characteristics and noise characteristics (such as thermal stress noise and adsorption effect noise) of MEMS microcavity devices change dynamically at different operating temperatures. A fixed amplitude cannot simultaneously guarantee the optimal signal-to-noise ratio and linearity across the entire temperature range. This invention establishes a feedback mechanism based on the correlation between resonant wavelength and temperature change, enabling dynamic and adaptive adjustment of the alternating current amplitude, ensuring that the detection system can automatically optimize based on the actual noise level at different temperature points.

[0016] This invention enhances anti-interference capabilities: the adaptive adjustment process, based on feedback correlation information, adaptively adjusts the modulation amplitude when noise interference severely affects resolution (corresponding to low correlation), thereby improving the ability to identify minute wavelength drifts and avoiding resonance peak distortion. This allows the invention to maintain high resolution and high accuracy detection capabilities even when faced with unpredictable and variable operating noise across the entire temperature range.

[0017] This invention improves the reliability of wavelength drift detection results: because the alternating current amplitude is set to match the actual state at each operating temperature point, the lock-in amplifier can more stably and accurately lock the center of the resonant peak. Based on this, the resonant wavelength data obtained at different operating temperatures show higher consistency and smaller random errors, thus laying a solid foundation for obtaining accurate and reliable resonant wavelength drift characteristics with temperature.

[0018] In summary, by introducing a feedback control mechanism based on wavelength-temperature correlation, this invention overcomes the shortcomings of traditional methods, such as parameter rigidity and weak anti-interference ability under varying temperature environments, and achieves high-resolution and high-precision detection of wavelength drift in MEMS microcavity resonators. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating the steps of a method for detecting the resonant wavelength drift of a MEMS microcavity device, as provided in an embodiment of the present invention. Detailed Implementation

[0021] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a MEMS microcavity device resonant wavelength drift detection method and system proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] The following description, in conjunction with the accompanying drawings, details the specific scheme of the MEMS microcavity device resonant wavelength drift detection method and system provided by the present invention.

[0024] Please see Figure 1 The diagram illustrates a flowchart of a method for detecting the resonant wavelength drift of a MEMS microcavity device according to an embodiment of the present invention. The method includes the following steps: Step S101: Drive the laser by adding an alternating current of a preset frequency to the driving current, use the laser signal generated by the laser to irradiate the microcavity device, and input the output signal of the microcavity device to the lock-in amplifier, which outputs a DC voltage signal.

[0025] This embodiment adds an alternating current of a preset frequency to the driving current to obtain a modulation signal. This modulation signal contains both DC and AC components, giving the laser signal irradiating the microcavity device a certain wavelength bandwidth (or frequency bandwidth). Furthermore, considering that the resonant peak of a MEMS microcavity device is very sharp, its transmittance varies greatly with wavelength (i.e., the slope) at the edge of the resonant peak. If the laser signal is single-frequency, a small wavelength drift will only cause a small change in light intensity, easily drowned out by noise. This embodiment introduces bandwidth through modulation, allowing the laser wavelength to rapidly "scan" at the edge of the resonant peak. At this time, the small wavelength drift is amplified by the steep slope of the resonant peak, transforming into a significant change in transmitted light intensity, enabling the lock-in amplifier to detect a small-scale drift. The lock-in amplifier acts as a narrow-bandwidth bandpass filter, allowing only signals near the modulation frequency to pass through, thereby filtering out some noise. This noise refers to the noise contained in the output signal of the microcavity device, including noise present in the laser signal due to driving current instability and laser operating errors, as well as operating noise of the microcavity device. This noise can overwhelm the wavelength drift detection results.

[0026] In this embodiment, the preset frequency is set to 60kHz, and the lock-in amplifier is specifically a single-phase lock-in amplifier. The frequency of its reference signal is equal to the preset frequency, and its integration time is set to 30ms.

[0027] Step S102: Control the drive current in real time so that the amplitude of the DC voltage signal is less than the preset voltage threshold.

[0028] The DC voltage signal output by the lock-in amplifier reflects the deviation or error of the center wavelength of the laser signal (i.e., the center of the wavelength bandwidth) relative to the center of the resonant peak. When the absolute value of the DC voltage signal (i.e., the amplitude of the DC voltage signal) is small, it indicates that the center wavelength of the laser signal is exactly aligned with the center of the microcavity's resonant peak. When the absolute value of the DC voltage signal (i.e., the amplitude of the DC voltage signal) is large, it indicates that the center wavelength of the laser signal is located at a considerable distance to the left or right of the resonant peak.

[0029] In this embodiment, the driving current is controlled in real time, causing it to change continuously. After each change, an alternating current of a preset frequency is added to the driving current to drive the laser. This process is equivalent to continuously adjusting the center wavelength of the laser signal. When the amplitude of the DC voltage signal output by the lock-in amplifier is less than the preset voltage threshold after changing the driving current, it indicates that the center wavelength of the laser signal is aligned with the center of the microcavity's resonant peak.

[0030] In this embodiment, a PID control algorithm is used to control the drive current. The sampling frequency of the PID control algorithm is set to 10Hz (i.e., the drive current is adjusted 10 times per second). The proportional gain, integral gain, and derivative gain in the PID control algorithm are set to 1.8, 0.45, and 0.03, respectively. In an optional example, the preset voltage threshold is set to 0V. In a preferred example, considering that there is noise in the PID control process, the lock-in amplifier cannot completely remove all noise from the output signal of the microcavity device; therefore, the amplitude of the DC voltage signal under PID control may not be constantly stable at 0V. Therefore, in this embodiment, the preset voltage threshold is set to 0.4mV, so that the DC voltage signal does not need to be constantly maintained at 0V.

[0031] As an example, the method for determining whether the amplitude of a DC voltage signal is less than a preset voltage threshold includes: Since the DC voltage signal changes dynamically when using PID control, this embodiment aims to keep the amplitude of the DC voltage signal dynamically stable near a small value. Based on this, the "less than the preset voltage threshold" mentioned in this example means that the average amplitude of the DC voltage signal in the most recent 0.5 seconds is less than the preset voltage threshold.

[0032] In some embodiments, during PID control, if after a long period of time (e.g., after 10 seconds) there is still no situation where the amplitude of the DC voltage signal is less than the preset voltage threshold, then it is directly determined that the amplitude of the DC voltage signal is less than the preset voltage threshold.

[0033] Step S103: When the amplitude of the DC voltage signal is less than the preset voltage threshold, the resonant wavelength of the microcavity device is first determined by the wavelength of the laser signal generated by the laser, and then the operating temperature of the microcavity device is changed; wherein, in the process of real-time control of the driving current, the amplitude of the alternating current added at each operating temperature is adjusted according to the correlation between the determined resonant wavelength and the operating temperature.

[0034] During the real-time control of the drive current, when the amplitude of the DC voltage signal is less than the preset voltage threshold, it indicates that the center wavelength of the laser signal is aligned with the center of the microcavity's resonant peak. At this time, the wavelength of the laser signal generated by the laser determines the resonant wavelength of the microcavity device, that is, the resonant wavelength of the microcavity device is equal to the center wavelength of the laser signal.

[0035] In this embodiment, considering that the operating temperature of MEMS microcavity devices is an important factor causing resonant wavelength drift, it is necessary to place the MEMS microcavity devices at different operating temperatures to detect the resonant wavelength in order to comprehensively and reliably measure the resonant wavelength drift.

[0036] Based on this, after determining the resonant wavelength of the microcavity device, this embodiment changes the operating temperature of the MEMS microcavity device to make it operate at other temperatures. Then, the resonant wavelength of the microcavity device is determined again according to the method of steps S101 to S103. After the resonant wavelength of the microcavity device is determined again, the operating temperature of the MEMS microcavity device is changed again, and so on, to obtain the resonant wavelength at different operating temperatures.

[0037] It should be further noted that while the above steps initially filter out some noise using a lock-in amplifier, some noise still remains that the lock-in amplifier cannot remove. This is because, firstly, the noise suppression capability of the lock-in amplifier is limited, and secondly, noise is complex and diverse. For example, MEMS microcavity devices generate operating noise due to vibration, stress, and even water molecule adsorption. Furthermore, the thermal expansion effect of MEMS microcavity devices varies at different operating temperatures, leading to different noise distribution patterns. In summary, the remaining noise prevents the above process of determining the resonant wavelength from further distinguishing smaller resonant wavelength drifts (i.e., low resolution) or from allowing the lock-in amplifier to more accurately lock onto the resonant wavelength.

[0038] Based on this, in the process of real-time control of the drive current, this embodiment adjusts the amplitude of the alternating current added at each operating temperature according to the determined correlation between the resonant wavelength and the operating temperature.

[0039] The correlation between the resonant wavelength and the operating temperature describes whether the resonant wavelengths obtained in the historical process have a significant correlation with the operating temperature. When there is no significant correlation, it indicates that the obtained resonant wavelengths are still severely affected by noise, and it is impossible to effectively determine the wavelength drift based on these resonant wavelengths. This embodiment utilizes the correlation between the resonant wavelength and the operating temperature to adjust the amplitude of the added alternating current at each operating temperature. This process feeds back the detection results of the resonant wavelength, allowing for further consideration of noise interference when determining the resonant wavelength of the microcavity device, providing a data basis for further noise suppression. Furthermore, the dynamic adaptive update of the alternating current amplitude not only enhances the noise suppression capability of the lock-in amplifier but also ensures that the amplitude of the alternating current added to the drive current is adapted to the operating temperature of the MEMS microcavity device. This avoids the problem that when the amplitude of the alternating current is too small (where the laser wavelength jitter range is too small, resulting in very weak changes in transmitted light intensity that are still easily drowned out by noise), the lock-in amplifier struggles to further distinguish minute wavelength drifts under noise interference. It also avoids the problem that when the amplitude of the alternating current is too large (where the laser wavelength jitter range exceeds the linear region of the resonant peak), the lock-in amplifier introduces high-order nonlinear signals, leading to resonant peak distortion and measurement inaccuracies. This further ensures that the lock-in amplifier can accurately lock the resonant wavelength.

[0040] Step S104: Perform wavelength drift detection based on the resonant wavelength determined at all operating temperatures.

[0041] The above process determines the resonant wavelength at different operating temperatures. Wavelength drift detection is performed based on the resonant wavelengths determined at all operating temperatures, which helps to ensure the comprehensive and reliable results of wavelength drift detection.

[0042] In summary, the above process in this embodiment overcomes the shortcomings of traditional methods such as parameter rigidity and weak anti-interference ability in variable temperature environments by introducing a feedback control mechanism based on wavelength-temperature correlation, and achieves high-resolution and high-precision detection of wavelength drift of MEMS microcavity resonance.

[0043] As a preferred example, an alternating current of a preset frequency is added to the driving current to obtain a modulated signal, including the following process: The signal value of the modulated signal at time t is I(t) = I0 + A0 × sin(wt), where I0 represents the driving current, A0 represents the amplitude of the alternating current, w represents the preset frequency, and sin(wt) represents the sinusoidal signal waveform.

[0044] As an example, the initial value of the drive current I0 is set to 60mA. Specifically, during real-time control of the drive current, if the drive current I0 is less than the laser's minimum startup current or greater than the laser's maximum operating current, the drive current I0 is set to equal the laser's minimum startup current or maximum operating current.

[0045] As an example, the initial value of the alternating current amplitude A0 is set to 1.3mA.

[0046] As a preferred example, determining the resonant wavelength of a microcavity device from the wavelength of the laser signal generated by the laser includes the following methods: Different constant currents are input into the laser, and the wavelength of the laser signal output by the laser is measured under each constant current. All constant currents are used as the abscissa, and the wavelength of the laser signal corresponding to each constant current is used as the ordinate. The coordinate points formed by all the abscissa and ordinate are connected by straight lines to obtain the curve of the laser output wavelength changing with the current.

[0047] When the amplitude of the DC voltage signal is less than the preset voltage threshold, the drive current after PID control is read, and the vertical axis corresponding to the drive current is obtained on the change curve. The vertical axis represents the center wavelength of the laser signal under the drive current, and it is used as the resonant wavelength of the microcavity device.

[0048] As an example, the sampling method for constant currents of different magnitudes is as follows: the minimum start-up current of the laser and the maximum operating current of the laser constitute an operating current range, and a number of currents (e.g., 500) are sampled at equal intervals within this operating current range as the constant current.

[0049] As a preferred example, methods for changing the operating temperature of a MEMS microcavity device include: Set upper and lower limits for the operating temperature of the MEMS microcavity device. The lower limit is used as the initial operating temperature, which is also the operating temperature of the MEMS microcavity device when the resonant wavelength is first determined. Starting from the lower limit, after each determination of the resonant wavelength (see steps S101-103), the operating temperature is increased by a preset first-step length, and then the resonant wavelength is determined again (see steps S101-103), and so on, until the operating temperature exceeds the upper limit. This process of increasing the operating temperature is recorded as the first temperature change process.

[0050] When the operating temperature exceeds the upper limit of the operating temperature, the resonant wave continues to be determined starting from the upper limit of the operating temperature. Each time the resonant wavelength is determined (see steps S101~103 for details), the operating temperature is reduced by a preset first step length, and then the resonant wavelength is determined again (see steps S101~103 for details). This process continues until the operating temperature is lower than the lower limit of the operating temperature, at which point the temperature change stops and the current step S104 ends. This process of decreasing the operating temperature is recorded as the second temperature change process.

[0051] This embodiment introduces two temperature change processes, namely the first temperature change process and the second temperature change process. The purpose is to achieve multiple measurements at the same operating temperature and to provide a data basis for the subsequent adjustment of the amplitude of the alternating current.

[0052] Based on this preferred example, it can be seen that during the process of changing the operating temperature, such as the first temperature change process or the second temperature change process, a resonant wavelength is determined corresponding to each operating temperature.

[0053] As an example, the upper and lower limits of the operating temperature are set to -40℃ and 120℃.

[0054] As an example, the default first step length is set to 1°C.

[0055] As a preferred example, adjusting the amplitude of the added alternating current at each operating temperature based on the determined correlation between the resonant wavelength and the operating temperature includes the following method: (1) During the first temperature change process, the amplitude of the alternating current remains constant.

[0056] (2) After the first temperature change process is completed, the resonant wavelength determined at each working temperature during the first temperature change process is recorded as the first wavelength. During the second temperature change process, any working temperature after the change (reduction) (including the upper limit of the working temperature) is marked as the target temperature.

[0057] (3) After marking the target temperature, but before re-determining the resonant wavelength according to steps S101~103, perform the following process: From all operating temperatures during the first temperature change process, the n operating temperatures with the smallest absolute difference from the target temperature are obtained, and denoted as the first neighborhood temperature sequence (including the target temperature). The first wavelength determined at all operating temperatures in the first neighborhood temperature sequence constitutes the first wavelength sequence. The first change correlation between the first wavelength sequence and the first neighborhood temperature sequence is denoted as the wavelength resolution coefficient of the target temperature.

[0058] The m working temperatures with the smallest absolute difference from the target temperature are obtained and denoted as the second neighborhood temperature sequence (including the target temperature), where m is greater than n. The first wavelength determined at all working temperatures in the second neighborhood temperature sequence constitutes the second wavelength sequence. The second variation correlation between the downsampling result of the second wavelength sequence and the downsampling result of the second neighborhood temperature sequence is denoted as the wavelength accuracy coefficient of the target temperature.

[0059] The wavelength resolution coefficient represents the correlation between the resonant wavelength obtained during a first temperature change and the change in operating temperature at a relatively small scale of operating temperature variation (representing the case where the operating temperature changes by a relatively small amount). When the presence of noise makes it impossible to distinguish small resonant wavelength drifts (i.e., low resolution), the resonant wavelength drift caused by small changes in operating temperature has the characteristics of random fluctuation, and the resonant wavelength drift cannot be accurately identified. In this case, the obtained wavelength resolution coefficient is small. Therefore, this embodiment uses the wavelength resolution coefficient to describe the impact of noise on the resonant wavelength drift resolution. The smaller the wavelength resolution coefficient, the lower the resonant wavelength drift resolution caused by the presence of noise.

[0060] The wavelength accuracy factor represents the correlation between the resonant wavelength obtained during a first temperature change and the change in operating temperature over a large scale of operating temperature variation (representing the case where the operating temperature changes by a relatively large amount). When the presence of noise prevents the lock-in amplifier from accurately locking the resonant wavelength, the resonant wavelength will fluctuate irregularly even with large changes in operating temperature. Large changes in operating temperature will not cause a clear trend change in the resonant wavelength, and in this case, the wavelength accuracy factor will be smaller. Therefore, this embodiment uses the wavelength accuracy factor to describe the impact of noise on the accuracy of resonant wavelength locking. The smaller the wavelength accuracy factor, the less accurately the lock-in amplifier can lock the resonant wavelength.

[0061] (4) Based on the relationship between the wavelength resolution coefficient and the wavelength accuracy coefficient at the target temperature, adjust the amplitude of the alternating current added at the target temperature, wherein the adjustment range of the amplitude is positively correlated with the difference between the wavelength resolution coefficient and the wavelength accuracy coefficient.

[0062] The relationship between the wavelength resolution coefficient and the wavelength accuracy coefficient describes the relationship between the resolution and locking accuracy of the resonant wavelength obtained near the target temperature during the first temperature change process. For example, when the wavelength resolution coefficient is smaller than the wavelength accuracy coefficient, it indicates that the presence of noise will significantly affect the resolution of the resonant wavelength. In this case, it is necessary to prioritize suppressing the low resolution caused by noise. This requires a larger increase in the amplitude of the alternating current to avoid the alternating current amplitude being too small, thus preventing the inability to distinguish minute wavelength drifts and the decrease in detection sensitivity. Conversely, when the wavelength resolution coefficient is larger than the wavelength accuracy coefficient, it indicates that the presence of noise will significantly prevent the lock-in amplifier from accurately locking the resonant wavelength. In this case, it is necessary to prioritize suppressing the low locking accuracy. This requires a larger decrease in the amplitude of the alternating current to avoid the alternating current amplitude being too large, thus preventing the lock-in amplifier from introducing high-order nonlinear signals that cause resonant peak distortion and measurement result distortion, ensuring the accuracy of the lock-in amplifier's resonant locking.

[0063] Thus, steps (1) to (4) above achieve the goal of adaptively updating the amplitude of the alternating current after each change (decrease) of the operating temperature during the second temperature change process (i.e., at the target temperature). Further, at this operating temperature (i.e., at the target temperature), based on the updated amplitude of the alternating current, the locked resonant wavelength is determined according to steps S101 to S103. Then, the operating temperature is changed (decreased) again, and the changed (decreased) operating temperature is remarked as the target temperature. Steps (1) to (4) are then repeated to achieve the goal of adaptively updating the amplitude of the alternating current, and the locked resonant wavelength is determined according to steps S101 to S103. This process continues until the second temperature change process ends.

[0064] The above process, by adjusting the amplitude of the alternating current added at each operating temperature, not only enhances the noise suppression capability of the lock-in amplifier, but also ensures that the amplitude of the alternating current added to the drive current can be adapted to the operating temperature of the MEMS microcavity device, further suppressing noise interference and guaranteeing the accuracy of the resonant wavelength determined during the second temperature change process.

[0065] As an example, the specific method for obtaining the first change correlation between the first wavelength sequence and the first neighborhood temperature sequence is as follows: The first wavelength sequence and the first neighborhood temperature sequence are normalized separately. The Pearson correlation coefficient between the normalized first wavelength sequence and the normalized first neighborhood temperature sequence is used as the first variation correlation. This example uses the softmax formula for normalization.

[0066] The specific process for obtaining the second change correlation is the same as that for the first change correlation, and will not be described in detail in this embodiment.

[0067] Specifically, when the correlation of the first change or the correlation of the second change is greater than 0.46, the correlation of the first change or the correlation of the second change is set to 1.

[0068] As a preferred example, adjusting the amplitude of the alternating current added at the target temperature based on the relationship between the wavelength resolution coefficient and the wavelength accuracy coefficient at the target temperature includes the following methods: The absolute value of the difference between the wavelength resolution coefficient and the wavelength accuracy coefficient is denoted as M, where M represents the adjustment range of the amplitude of the alternating current.

[0069] The adjusted amplitude of the alternating current is A1 = A0 × (1 + k × M), where A0 represents the amplitude of the alternating current during the first temperature change, and k describes the relationship between the wavelength resolution coefficient and the wavelength accuracy coefficient. When the wavelength resolution coefficient is less than the wavelength accuracy coefficient, k = 1, indicating an increase in the amplitude of the alternating current; when the wavelength resolution coefficient is greater than the wavelength accuracy coefficient, k = -1, indicating a decrease in the amplitude of the alternating current. Specifically, when the wavelength resolution coefficient is equal to the wavelength accuracy coefficient, k = 0, and the amplitude of the alternating current remains unchanged. Therefore, this embodiment cannot further suppress noise interference by adjusting the amplitude of the alternating current.

[0070] In some examples, when M is less than or equal to 0.2, the wavelength resolution coefficient is determined to be equal to the wavelength accuracy coefficient; when M is greater than 0.2, the wavelength resolution coefficient is determined to be greater than or less than the wavelength accuracy coefficient. This example avoids interference from calculation errors of the wavelength resolution coefficient and wavelength accuracy coefficient. Only when there is a significant difference between the wavelength resolution coefficient and the wavelength accuracy coefficient is the wavelength resolution coefficient determined to be greater than or less than the wavelength accuracy coefficient, and noise interference is suppressed by adjusting the amplitude of the variable current. When the wavelength resolution coefficient and the wavelength accuracy coefficient have a small difference, the wavelength resolution coefficient is determined to be equal to the wavelength accuracy coefficient, and noise interference is no longer suppressed by adjusting the amplitude of the variable current, making the noise suppression process robust.

[0071] As a preferred example, when the wavelength resolution factor equals the wavelength accuracy factor, it is impossible to further suppress noise interference by adjusting the amplitude of the alternating current. In this case, noise can be suppressed as much as possible from the PID control process using the following method: When the average of the wavelength resolution coefficient and wavelength accuracy coefficient of the target temperature is less than a preset first value (e.g., 0.46), the voltage threshold is reduced, for example, by 50%, and then the resonant wavelength is determined according to steps S101-103 (that is, the resonant wavelength is no longer determined by adjusting the amplitude of the alternating current). Although this process of reducing the voltage threshold sacrifices the efficiency of PID control (that is, it takes a relatively long time for the amplitude of the DC voltage signal to be less than the reduced voltage threshold), it can ensure the accuracy of the DC voltage signal control result, thereby ensuring the accuracy of the resonant wavelength acquisition result to a certain extent.

[0072] It should be noted that when the wavelength resolution coefficient is greater than or less than the wavelength accuracy coefficient, it is not necessary to reduce the voltage threshold. In other words, it is sufficient to keep it constant at the value preset in step S102 (i.e., 0.4mV). This is because determining the resonant wavelength by adjusting the amplitude of the alternating current is more efficient than determining the resonant wavelength by reducing the voltage threshold (i.e., the PID control is more efficient and can also effectively suppress noise interference).

[0073] It should also be noted that when the average value of the wavelength resolution coefficient and wavelength accuracy coefficient of the target temperature is greater than or equal to the preset first value, it means that the noise interference can be ignored. At this time, the amplitude of the alternating current and the voltage threshold remain unchanged and are not adjusted.

[0074] In another example, when reducing the voltage threshold as described above, the voltage threshold can be reduced by q×100%, where q and the mean of the wavelength resolution coefficient and wavelength accuracy coefficient of the target temperature are negatively correlated. This indicates that the smaller the wavelength resolution coefficient and wavelength accuracy coefficient are (i.e., the more significant the noise interference), the more significantly the voltage threshold needs to be reduced. This achieves adaptive change of the voltage threshold, adaptively suppressing noise by adapting to the noise interference situation, and improving the control efficiency of the PID to a certain extent. In one example... , where x represents the mean of the wavelength resolution coefficient and the wavelength accuracy coefficient. Used to normalize x, that is, to obtain exp() represents an exponential function with the natural constant as the base.

[0075] As a preferred example, the method for obtaining the downsampling results of the second wavelength sequence and the downsampling results of the second neighborhood temperature sequence is as follows: In the second wavelength sequence, starting from the first wavelength corresponding to the target temperature, it is traversed to both sides with a step size of 2. The sequence formed by all the first wavelengths traversed is used as the downsampling result of the second wavelength sequence. That is, in the second wavelength sequence, starting from the first wavelength corresponding to the target temperature, every other element retains a first wavelength, thereby achieving downsampling.

[0076] In the second neighborhood temperature sequence, starting from the target temperature, it traverses to both sides with a step size of 2. The sequence formed by the traversed working temperatures is used as the downsampling result of the second neighborhood temperature sequence. That is, in the second neighborhood temperature sequence, starting from the target temperature, every other element retains a working temperature, thereby achieving downsampling.

[0077] As an example, m and n are set to odd numbers, for example, m is set to 2n+1 and n is set to 7.

[0078] As an optional example, wavelength drift detection based on the resonant wavelength determined at all operating temperatures includes the following steps: The resonant wavelength determined by the second temperature change process is denoted as the second wavelength.

[0079] This example uses the second wavelength at 25°C as the standard resonant wavelength. The difference between all second wavelengths and the standard resonant wavelength is recorded as the wavelength drift detection results at all operating temperatures.

[0080] Plot the wavelength drift detection results as the vertical axis and the corresponding operating temperature as the horizontal axis. Then, plot the wavelength drift detection results as a function of the operating temperature. Use this curve as the resonant wavelength drift characteristic curve of the MEMS microcavity device and store or display it in the technical manual of the MEMS microcavity device. Mark the standard resonant wavelength and the corresponding operating temperature (i.e., 25℃) on the characteristic curve.

[0081] As a preferred example, wavelength drift detection based on the resonant wavelength determined at all operating temperatures includes the following steps: For any temperature during the second temperature change process, i.e. the target temperature mentioned above, the resonant wavelength determined at the target temperature during the first temperature change process is denoted as the first measurement wavelength L1, and the resonant wavelength determined at the target temperature during the second temperature change process is denoted as the second measurement wavelength L2.

[0082] The average of the wavelength resolution coefficient and wavelength accuracy coefficient at the target temperature is denoted as the first fusion weight w1. L1 and L2 are fused using the first fusion weight w1 and the second fusion weight w2 to obtain the fused resonant wavelength at the target temperature. After the second temperature change process is completed, the fused resonant wavelength at each operating temperature is obtained.

[0083] Wavelength drift detection is performed based on the fusion resonant wavelength determined at all operating temperatures. The specific process is the same as the optional example above, that is, the fusion resonant wavelength at 25℃ is taken as the standard resonant wavelength, and the difference between all fusion resonant wavelengths and the standard resonant wavelength is recorded as the wavelength drift detection result at all operating temperatures.

[0084] The larger the fusion weight w1, the less noise interference the resonant wavelength determined at the target temperature during the first temperature change process is subjected to. In this case, the reliability of the resonant wavelength L1 is relatively high, and the value of L1 should be given more attention after fusing L1 and L2. Conversely, the smaller the fusion weight w1, the more significant the noise interference the resonant wavelength determined at the target temperature is subjected to during the first temperature change process. In this case, the reliability of the resonant wavelength L1 is relatively low, and the value of L1 should not be given more attention after fusing L1 and L2. Specifically, when w1 is less than 0, w1=0; when w1 is greater than 1, w1=1.

[0085] The second fusion weight w2 is a preset value, and w2 is greater than or equal to w1. The purpose is that since L2 is determined by adaptively updating the amplitude of the alternating current, noise interference is further suppressed. Therefore, when fusing L1 and L2, more attention is paid to the value of L2.

[0086] As an example, let w2 = 2 - w1, then w2 is greater than or equal to w1.

[0087] As an example, L1 and L2 are fused using the first fusion weight w1 and the second fusion weight w2, specifically including: The softmax formula is used to normalize w1 and w2, and the normalized w1 and w2 are used to perform a weighted summation of L1 and L2 to obtain the fusion resonant wavelength.

[0088] Another embodiment of the present invention provides a MEMS microcavity device resonant wavelength drift detection system. The system includes a resonant wavelength drift detection module, which includes a MEMS microcavity device to be detected, a laser, a lock-in amplifier, and an optical heating and cooling stage for changing the operating temperature of the MEMS microcavity device.

[0089] The resonant wavelength drift detection module includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor runs the computer program, it implements all the steps of all the above embodiments.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting resonant wavelength drift in MEMS microcavity devices, characterized in that, The method includes the following steps: A laser is driven by adding an alternating current of a preset frequency to the driving current. The laser signal generated by the laser is used to irradiate a microcavity device, and the output signal of the microcavity device is input to a lock-in amplifier, which outputs a DC voltage signal. The drive current is controlled in real time. When the amplitude of the DC voltage signal is less than a preset voltage threshold, the resonant wavelength of the microcavity device is first determined by the wavelength of the laser signal generated by the laser, and then the operating temperature of the microcavity device is changed. In the process of real-time control of the drive current, the amplitude of the alternating current added at each operating temperature is adjusted according to the correlation between the determined resonant wavelength and the operating temperature. Wavelength drift detection is performed based on the resonant wavelength determined at all operating temperatures.

2. The method for detecting resonant wavelength drift in a MEMS microcavity device according to claim 1, characterized in that, The process of changing the operating temperature of the microcavity device consists of a first temperature change process and a second temperature change process. The specific steps for obtaining the first and second temperature change processes are as follows: Starting from the lower limit of the operating temperature, after each determination of the resonant wavelength, the operating temperature is increased by a preset first step length. After each increase in the operating temperature, the resonant wavelength is determined again until the operating temperature is greater than the upper limit of the operating temperature. This process of increasing the operating temperature is called the first temperature change process. When the operating temperature exceeds the upper limit of the operating temperature, the operating temperature is gradually decreased starting from the upper limit, with a preset first step length. After each decrease in the operating temperature, a resonant wavelength is determined, until the operating temperature is lower than the lower limit of the operating temperature, at which point the temperature change stops. This process of decreasing the operating temperature is called the second temperature change process.

3. The method for detecting resonant wavelength drift in a MEMS microcavity device according to claim 2, characterized in that, The specific steps for adjusting the amplitude of the added alternating current at each operating temperature based on the determined correlation between the resonant wavelength and the operating temperature are as follows: During the first temperature change process, the amplitude of the alternating current remains constant; after the first temperature change process ends, the resonant wavelength determined at each operating temperature during the first temperature change process is recorded as the first wavelength. During the second temperature change process, any working temperature after the change is marked as the target temperature; From all the working temperatures during the first temperature change process, obtain the neighborhood temperature sequence of the target temperature; the correlation between the first wavelength sequence determined at all working temperatures in the neighborhood temperature sequence and the neighborhood temperature sequence at different sampling scales is denoted as the wavelength resolution coefficient and wavelength accuracy coefficient of the target temperature, respectively. Based on the relationship between the wavelength resolution coefficient and the wavelength accuracy coefficient at the target temperature, the amplitude of the alternating current added at the target temperature is adjusted, wherein the adjustment range of the amplitude is positively correlated with the difference between the wavelength resolution coefficient and the wavelength accuracy coefficient.

4. The method for detecting resonant wavelength drift of a MEMS microcavity device according to claim 3, characterized in that, The specific steps for adjusting the amplitude of the alternating current added at the target temperature based on the relationship between the wavelength resolution coefficient and the wavelength accuracy coefficient at the target temperature are as follows: The absolute value of the difference between the wavelength resolution coefficient and the wavelength accuracy coefficient is used as the adjustment range when adjusting the amplitude of the alternating current; wherein, when the wavelength resolution coefficient is less than the wavelength accuracy coefficient, the amplitude of the alternating current is increased; when the wavelength resolution coefficient is greater than the wavelength accuracy coefficient, the amplitude of the alternating current is decreased; when the wavelength resolution coefficient is equal to the wavelength accuracy coefficient, the amplitude of the alternating current is not changed.

5. The method for detecting resonant wavelength drift of a MEMS microcavity device according to claim 4, characterized in that, When the wavelength resolution coefficient equals the wavelength accuracy coefficient, the voltage threshold is reduced. The amount of reduction in the voltage threshold is negatively correlated with the mean value of the wavelength resolution coefficient and the wavelength accuracy coefficient of the target temperature.

6. The method for detecting resonant wavelength drift of a MEMS microcavity device according to claim 3, characterized in that, The specific steps for obtaining the wavelength resolution coefficient and wavelength accuracy coefficient of the target temperature are as follows: From all the working temperatures during the first temperature change process, obtain the n working temperatures with the smallest difference from the target temperature, and denot them as the first neighborhood temperature sequence of the target temperature; the first wavelength determined at all working temperatures in the first neighborhood temperature sequence constitutes the first wavelength sequence; the first change correlation between the first wavelength sequence and the first neighborhood temperature sequence is denoted as the wavelength resolution coefficient of the target temperature. The m working temperatures with the smallest difference from the target temperature are obtained and denoted as the second neighborhood temperature sequence of the target temperature. The first wavelength determined at all working temperatures in the second neighborhood temperature sequence constitutes the second wavelength sequence. The second change correlation between the downsampling result of the second wavelength sequence and the downsampling result of the second neighborhood temperature sequence is denoted as the wavelength accuracy coefficient of the target temperature. Where m and n are preset values, and m is greater than n.

7. The method for detecting resonant wavelength drift of a MEMS microcavity device according to claim 3, characterized in that, The specific steps for wavelength drift detection based on the resonant wavelength determined at all operating temperatures are as follows: For the target temperature, the resonant wavelength determined at the target temperature during the first temperature change process is denoted as the first measurement wavelength, and the resonant wavelength determined at the target temperature during the second temperature change process is denoted as the second measurement wavelength. The average value of the wavelength resolution coefficient and wavelength accuracy coefficient of the target temperature is recorded as the first fusion weight. The first measurement wavelength and the second measurement wavelength are fused using the first fusion weight and the second fusion weight to obtain the fused resonant wavelength at the target temperature. After the second temperature change process is completed, the fusion resonance wavelength at all operating temperatures is obtained; wavelength drift detection is performed based on the fusion resonance wavelength determined at all operating temperatures. The second fusion weight is a preset value that is greater than the first fusion weight.

8. The method for detecting resonant wavelength drift of a MEMS microcavity device according to claim 7, characterized in that, The specific steps for wavelength drift detection based on the fusion resonance wavelength determined at all operating temperatures are as follows: The fusion resonance wavelength at the preset operating temperature is taken as the standard resonance wavelength; the difference between the fusion resonance wavelength determined at all operating temperatures and the standard resonance wavelength is recorded as the wavelength drift detection result at all operating temperatures.

9. The method for detecting resonant wavelength drift in a MEMS microcavity device according to claim 1, characterized in that, The specific steps involved in determining the resonant wavelength of the microcavity device by analyzing the wavelength of the laser signal generated by the laser are as follows: Different preset constant currents are input into the laser, and the wavelength of the laser signal output by the laser is measured under each constant current. All constant currents are used as the abscissa, and the wavelength of the laser signal corresponding to each constant current is used as the ordinate. The coordinate points formed by all the abscissa and ordinate are connected by a straight line to obtain the curve of the laser output wavelength changing with the current. When the amplitude of the DC voltage signal is less than the preset voltage threshold, the drive current after control is read, and the ordinate corresponding to the drive current is obtained on the curve. This ordinate is used as the resonant wavelength of the microcavity device.

10. A MEMS microcavity device resonant wavelength drift detection system, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor runs the computer program, it implements all the steps of the MEMS microcavity device resonant wavelength drift detection method according to any one of claims 1 to 9.

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