A high-order scattering zero-enhanced phase sensing platform

Abstract

The present invention discloses a high-order scattering zero-point enhanced phase sensing platform, which includes a high-order scattering zero-point control unit and a sensing unit. The phase sensing platform does not need to adjust the sensor parameters. By regulating the high-order scattering zero-point control unit, high-order scattering zero points are achieved and the change of the transmission spectrum is measured, thereby realizing the measurement of the phase change at the sensor. The sensing unit is an insertable external sensor separated from the high-order scattering zero-point control unit, and this sensor can respond to the perturbation caused by the sensing target or external field and change the optical phase. The high-order scattering zero-point control unit is a non-Hermitian multi-mode non-reciprocal optical system composed of two whispering gallery mode optical microcavities and a waveguide that are mutually coupled. Moreover, in the coupled whispering gallery mode optical microcavity group, a bidirectional coupling channel caused by the scattering of isotropic scatterers and a non-reciprocal unidirectional coupling channel caused by single-ended specular reflection are respectively introduced. The present invention can be applied to any conventional sensor.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical sensing and quantum sensing, and particularly relates to a high-order scattering zero-enhanced phase sensing platform. Background Art

[0002] Optical sensors use optical phase to transmit valuable information and play an important role in many fields such as gravitational wave detection, biomedical imaging, and structural health monitoring. Due to the limitation of the sensitivity of traditional optical sensing technology, it is difficult to meet the increasingly high precision requirements of optical phase sensing. Therefore, it is of great significance to seek new technologies to improve sensitivity.

[0003] Existing methods for improving phase sensing include the exceptional point (EP)-enhanced phase sensing platform. (Mao W, Fu Z, Li Y, at el. Exceptional–point–enhanced phase sensing[J / OL]. Science Advances, 2024, 10(14): eadl5037. DOI: 10.1126 / sciadv.adl5037 .) The EP-enhanced phase sensing platform applies EP-enhanced sensing technology to traditional optical sensors. This platform is equipped with a plug-in external sensor separated from the exceptional point control unit. The improvement in sensitivity stems from the square root behavior of the eigenvalues, and there is a corresponding correlation between the valleys of the transmission spectrum and the real part of the eigenvalues. Thus, a small perturbation received by the system will be converted and amplified into spectral features. By separating the sensing and control functions, the applicability of the exceptional point enhancement technology to various conventional sensors is expanded. It builds a general platform for the application of exceptional point enhancement technology to different phase-dependent structures and is expected to achieve ultra-high sensitivity sensing in various applications. However, the implementation of EP is accompanied by fundamental noise generated by eigenvalue collapse, which will reduce the sensing performance. Moreover, the method constructs a second-order EP system, and there is still room for improving sensitivity. Summary of the Invention

[0004] The object of the present invention is to overcome the above deficiencies of the existing EP-enhanced phase sensing platform and provide a high-stability and high-performance high-order scattering zero-enhanced phase sensing platform.

[0005] The technical solution for achieving the object of the present invention is as follows: A high-order scattering zero-enhanced phase sensing platform, including a high-order scattering zero control unit and a sensing unit. The phase sensing platform does not require adjustment of sensor parameters. By regulating the high-order scattering zero control unit, high-order scattering zeros are achieved and the change of the transmission spectrum is measured, thereby realizing the measurement of the phase change at the sensor. The sensing unit is a plug-in external sensor separated from the high-order scattering zero control unit, and this sensor can respond to perturbations caused by sensing targets or external fields and change the optical phase. The high-order scattering zero control unit is a non-Hermitian multi-mode non-reciprocal optical system composed of two coupled whispering gallery mode optical microcavities and a waveguide. And in the coupled whispering gallery mode optical microcavity group, a bidirectional coupling channel caused by isotropic scatterer scattering and a non-reciprocal unidirectional coupling channel caused by single-end mirror reflection are respectively introduced.

[0006] Further, the two whispering gallery mode optical microcavities are respectively denoted as microcavity a and microcavity b. The high-order scattering zero control unit further includes a bus waveguide, an interconnecting waveguide, and a phase transformation device. Microcavity a is coupled to the bus waveguide, and the probe light is input from the first port of the bus waveguide, and the transmission spectrum is measured from the second port of the bus waveguide. Microcavity b is coupled to the interconnecting waveguide. The left side of the interconnecting waveguide is successively connected to the phase transformation device and the sensing unit, and the right side is used as a non-reflecting end. The phase transformation device is used to adjust the phase of the coupling coefficient to meet the condition parameters for achieving high-order scattering zeros.

[0007] Further, each of the whispering gallery mode optical microcavities supports two transmission modes, CW and CCW. The eigenfrequencies of the four modes are degenerate but the eigenvectors are orthogonal to each other.

[0008] Further, a bidirectional coupling channel caused by scattering is introduced into microcavity a, so that the CW mode and the CCW mode in microcavity a are bidirectionally coupled.

[0009] A non-reciprocal unidirectional coupling channel caused by single-end mirror reflection is introduced into microcavity b, so that the CCW mode in microcavity b is reflected back to microcavity b through the interconnecting waveguide and the sensing unit, while the CW mode passes through the non-reflecting end on the right side of the interconnecting waveguide, introducing a unidirectional coupling from the CCW mode to the CW mode.

[0010] Further, the effective Hamiltonian of the high-order scattering zero control unit is represented by a 4×4 matrix:

[0011]

[0012] In the formula, are the resonant frequencies of microcavity a and microcavity b, They are the intrinsic losses of microcavity a and microcavity b respectively, is the gain of microcavity a, are the coupling coefficients between microcavity a and the bus waveguide, and between microcavity b and the interconnecting waveguide; is the two-way coupling coefficient of the CW and CCW modes caused by scattering in microcavity a, is the one-way coupling coefficient that the CCW mode in microcavity b is coupled to the CW mode through the interconnecting waveguide and reflected back to microcavity b by the sensing unit without the action of the optical phase signal of the sensing unit, is the two-way coupling coefficient of microcavity a and microcavity b, where i represents the imaginary symbol.

[0013] Furthermore, the high-order scattering zero control unit realizes a fourth-order exceptional point, specifically by constructing the fourth-order scattering zero of the transmission spectrum.

[0014] Furthermore, the transmission spectrum is :

[0015]

[0016] In the formula, is the eigenvalue of the effective Hamiltonian H, , are fourth-order polynomials related to the frequency ω, is 's solution, 's solution is also the eigenvalue of the effective Hamiltonian H, .

[0017] Furthermore, the construction of the fourth-order scattering zero of the transmission spectrum is achieved by setting the coupling coefficients and gain-loss ratios of each part of the high-order scattering zero control unit so that all the roots of the fourth-order polynomial of the transmission spectrum are degenerate.

[0018] Furthermore, the phase sensing platform further includes:

[0019] A noise feedback unit, which is used to feedback the phase shift to the phase transformation device on the interconnecting waveguide according to the influence of environmental noise on the signal-to-noise ratio under different perturbations and the sensitivity under different perturbations before the phase sensing platform measures, and adjust the operating point of the high-order scattering zero control unit, that is, the non-Hermitian multi-mode non-reciprocal optical system, to a suitable position; the suitable position means that the signal-to-noise ratio is within a preset acceptance range and the sensitivity is greater than a preset standard threshold.

[0020] Furthermore, the noise feedback unit specifically realizes:

[0021] Introduce sensitivity, and obtain the response curves of the valley point frequency splitting and sensitivity of the phase sensing platform in the ideal state to the phase perturbation respectively;

[0022] Obtain the response curve of the signal-to-noise ratio and perturbation under noise in the measurement environment; the signal-to-noise ratio is defined as the ratio of the valley point frequency splitting in the ideal case to the fluctuation of the valley point frequency splitting caused by noise.

[0023] Based on the above response curve, select the position where the signal-to-noise ratio is within the preset acceptance range and the sensitivity is greater than the preset standard threshold as the operating point of the non-Hermitian multimode non-reciprocal optical system, and denote the phase perturbation at this position as , and feedback it as the phase offset to the phase transformation device on the interconnected waveguide, so that it adds a phase offset that changes the operating point on the basis of the phase offset implementing the scattering zero point.

[0024] Compared with the prior art, the remarkable advantages of the present invention are:

[0025] (1) The present invention applies the high-order scattering zero point enhancement technology to the design of the sensing platform with separated control unit and sensing unit, ensuring its applicability to a wide range of conventional sensors.

[0026] (2) For the first time, it is proposed to introduce a coupling channel through isotropic scatterer scattering and single-end mirror reflection in two coupled whispering gallery mode microcavities, breaking the symmetry of the coupled cavity group and realizing a non-Hermitian non-reciprocal system of four modes.

[0027] (3) High-order scattering zero points are realized in the non-reciprocal multimode non-Hermitian system by adjusting system parameters. Among them, the non-reciprocal design can enhance the robustness of the system (for example, the parameters given in the implementation case value, the coupling phase does not necessarily have to be π / 5. With other phases, the spectrum of this system has the same response characteristics to perturbations. As long as the parameter relationship can meet the requirements of the given algebraic expressions, such as , etc., and other undetermined parameters are reasonable), the implementation of high-order scattering zero points will not result in the collapse of eigenvalues. The eigenvalues of the Hamiltonian can have negative imaginary parts, and the evanescent field in the solution will decay quickly, being more stable.

[0028] (4) The non-reciprocal high-order scattering zero point is used to enhance phase sensing. The fourth root behavior of the zero points of the molecular polynomial of the transmission spectrum expression leads to the enhancement of the phase measurement sensitivity, which mainly determines the valley characteristics of the transmission spectrum. This makes the small perturbations received by the system present as amplified spectral changes. The valley frequency splitting of the transmission spectrum is proportional to the fourth root of the optical phase change under small perturbations, thereby realizing the enhanced measurement of small signals of induced phase changes.

[0029] (5) The response of the sensing platform to phase changes is improved from being proportional to the square root to the fourth root, having higher sensitivity when measuring small perturbations.

[0030] (6) The platform also has a noise feedback system. After monitoring the noise in the environment, it feeds back the phase shift to move the working point to a suitable position, effectively achieving the balance between sensitivity and anti-interference ability.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings. Brief Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the overall structure of the present invention's high-order scattering zero-enhanced phase sensing platform.

[0033] Figure 2 In (a) of, it is a change diagram of the transmission spectrum of the present invention with the optical phase change brought by the sensing unit. Figure 2 In (b) of, it is a curve of the valley frequency splitting of the transmission spectrum of the present invention with noise with the optical phase change brought by the sensing unit. The inset is a comparison diagram after taking the double logarithm of the quarter-power function curve and the frequency splitting curve.

[0034] Figure 3 In (a) of, it is a curve of the sensitivity of the present invention with the optical phase change brought by the sensing unit and the negative three-quarter-power function curve. The inset is a comparison diagram after taking the double logarithm of the frequency splitting curve, the negative three-quarter-power function curve, and the negative half-power function curve. Figure 3 In (b) of, it is a curve diagram of the signal-to-noise ratio of the present invention with noise with the optical phase change brought by the sensing unit.

[0035] Reference Numerals: 1 bus waveguide, 2 interconnecting waveguide, 3 whispering gallery mode optical microcavity a, 4 whispering gallery mode optical microcavity b, 5 phase transformation device, 6 sensing unit, 7 noise feedback unit. 1, 2, 3, 4, 5 together constitute a high-order scattering zero control unit. Specific Embodiments

[0036] In order to make the objectives, technical solutions, and advantages of the present application clearer, the following further describes the present application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0037] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0038] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] In one embodiment, in combination with Figure 1 , a high-order scattering zero-enhanced phase sensing platform is provided, including a high-order scattering zero control unit and a sensing unit. The phase sensing platform does not require adjustment of sensor parameters. By regulating the high-order scattering zero control unit, high-order scattering zeros are achieved and the change of the transmission spectrum is measured, and then the phase change at the sensor is measured (the change of the transmission spectrum is specifically manifested as the change of the valley point with the perturbation, as shown in Figure 2 (a) in

[0040] ; the sensing unit is an insertable external sensor separated from the high-order scattering zero control unit, and the sensor can change the optical phase in response to the perturbation caused by the sensing target or external field; the high-order scattering zero control unit is a non-Hermitian multimode non-reciprocal optical system composed of two whispering gallery mode optical microcavities and a waveguide that are mutually coupled, and in the coupled whispering gallery mode optical microcavity group, a bidirectional coupling channel caused by isotropic scatterer scattering and a non-reciprocal unidirectional coupling channel caused by single-ended mirror reflection are respectively introduced.

[0041] Preferably here, the phase transformation device uses a phase shifter.

[0042] Further, in one embodiment, each of the whispering gallery mode optical microcavities supports two transmission modes, CW and CCW, and the eigenfrequencies of the four modes are degenerate but the eigenvectors are orthogonal to each other.

[0043] Further, in one of the embodiments, a bidirectional coupling channel caused by scattering is introduced into the microcavity a, enabling bidirectional coupling between the CW mode and the CCW mode in the microcavity a;

[0044] A non-reciprocal unidirectional coupling channel caused by single-ended mirror reflection is introduced into the microcavity b, enabling the CCW mode in the microcavity b to return to the microcavity b through the reflection of the sensing unit via the interconnecting waveguide, while the CW mode passes through the non-reflective end on the right side of the interconnecting waveguide, introducing unidirectional coupling from the CCW mode to the CW mode.

[0045] Further, in one of the embodiments, without considering the input and noise, 、 、 、 are used to represent the amplitudes of the four modes. The effective Hamiltonian of the high-order scattering zero control unit is represented by a 4×4 matrix:

[0046]

[0047] In the formula, are the resonant frequencies of the microcavity a and the microcavity b, are the intrinsic losses of the microcavity a and the microcavity b respectively, is the gain of the microcavity a, are the coupling coefficients between the microcavity a and the bus waveguide, and between the microcavity b and the interconnecting waveguide; is the bidirectional coupling coefficient between the CW and CCW modes in the microcavity a caused by scattering, is the unidirectional coupling coefficient of the CCW mode in the microcavity b coupling to the CW mode through the reflection of the sensing unit via the interconnecting waveguide when there is no optical phase signal in the sensing unit, is the bidirectional coupling coefficient between the microcavity a and the microcavity b, where i represents the imaginary symbol.

[0048] Further, in one of the embodiments, the high-order scattering zero control unit realizes a fourth-order exceptional point, specifically by constructing a fourth-order scattering zero of the transmission spectrum.

[0049] The transmission spectrum is :

[0050]

[0051] In the formula, are the eigenvalues of the effective Hamiltonian H, 、 are fourth-order polynomials related to the frequency w, is 's solution, The solutions are also the eigenvalues of the effective Hamiltonian H. .

[0052] Specifically here:

[0053] Use , , , to represent the amplitudes of the four modes. The system only has a probe light input from the first port and coupled to the CW mode in the a-cavity, and its amplitude is represented by . The output is measured at the second port, and its amplitude is represented by .

[0054] The equations of motion are:

[0055]

[0056] where:

[0057]

[0058] To determine the cavity mode amplitude , the equations of motion can be Fourier-transformed and then Cramer's rule can be used.

[0059]

[0060] is the eigenvalue of the Hamiltonian H, is a fourth-order polynomial, is 's solution.

[0061] Then the expression of the transmission spectrum is:

[0062]

[0063] Preferably, in some embodiments, the fourth-order scattering zeros for constructing the transmission spectrum are obtained by setting the coupling coefficients and gain-loss ratios of the various parts of the high-order scattering zero control unit such that all the roots of the fourth-order polynomial of the transmission spectrum are degenerate.

[0064] Here, the coupling coefficients and gain-loss ratios between the various parts of the control unit can be set according to the normalized parameter relationship. The system's normalized parameter relationship is satisfied such that the coefficients of the and terms of should correspond one-to-one with the coefficients of the same-order terms of , is an auxiliary real number, and fourth-order scattering zeros are obtained.

[0065] Exemplarily, a set of parameters is set according to the normalization parameter relationship as follows: , , .

[0066] Furthermore, in one embodiment, the phase sensing platform further includes:

[0067] A noise feedback unit, configured to, before the phase sensing platform measures, according to the influence of environmental noise on the signal-to-noise ratio under different perturbations and the sensitivity under different perturbations, feedback a phase shift to the phase transformation device on the interconnected waveguide, and adjust the operating point of the high-order scattering zero control unit, i.e., the non-Hermitian multimode non-reciprocal optical system, to a suitable position; the suitable position means that the signal-to-noise ratio is within a preset acceptance range and the sensitivity is greater than a preset standard threshold.

[0068] Here, preferably, the preset standard threshold is of the maximum sensitivity.

[0069] Preferably, in some embodiments, the noise feedback unit specifically implements:

[0070] Introduce sensitivity, and obtain the response curves of the valley point frequency splitting, sensitivity of the phase sensing platform under ideal conditions respectively with respect to phase perturbation;

[0071] Obtain the response curve of the signal-to-noise ratio and perturbation under noise in the measurement environment; the signal-to-noise ratio is defined as the ratio of the valley point frequency splitting under ideal conditions to the fluctuation of the valley point frequency splitting caused by noise;

[0072] Based on the above response curves, select the position where the signal-to-noise ratio is within the preset acceptance range and the sensitivity is greater than the preset standard threshold as the operating point of the non-Hermitian multimode non-reciprocal optical system, denote the phase perturbation at this position as , and feedback it as a phase shift to the phase transformation device on the interconnected waveguide, so that on the basis of the phase shift for implementing the scattering zero, an additional phase shift for changing the operating point is added (by adding on the basis of the phase shift that satisfies the high-order scattering zero in the phase shifter, to achieve the offset of the operating point).

[0073] Here, the phase brought by the sensing unit acts on the unidirectional coupling process, changing the coupling coefficient to , which is input as a perturbation to the control unit, and after the coupling process, it is converted into a quantifiable spectral characteristic. Specifically, the transmittance spectrum has a transmittance of 0 at the center frequency when is 0, and at When it is not zero, the transmittance at the center frequency is 1, and there will be a valley at each of its left and right ends. The absolute value of the frequency difference between the left and right valley bottoms is defined as the valley frequency splitting. The valley frequency splitting increases with increasing, and is proportional to at

[0074] Exemplarily, for simulating measurements, it is necessary to consider how the system interacts with its environment and how noise affects the output signal. Input noise is introduced into the system, including the incoherent input vector of the radiation noise source, and the incoherent input vector of the dissipative noise source.

[0075] The noise functions included in the noise vector satisfy the following conditions. The noise functions obeying the Gaussian distribution have the following properties:

[0076]

[0077]

[0078] Among them, are the noise functions related to the radiation and amplification / dissipation channels respectively, and have autocorrelation, i = 1, 2.

[0079] Based on the standard coupled-mode theory, the evolution of an open, noisy system with 4 resonances and 4 ports can be written as:

[0080]

[0081]

[0082] Among them, is the input matrix, is the incoherent input vector of the radiation noise source input from the waveguide, is the incoherent input vector of the dissipative noise source. N is a 4×4 diagonal matrix that describes how the dissipative noise couples with the modes. For the radiation noise source, the noise input of the port with only unidirectional output can be suppressed by an optical isolator. Therefore, we consider that there is no radiation noise at the second port of the BWG and the reflectionless end of the IWG. The noise related to the radiation and the amplification / dissipation channels

[0083] has autocorrelation and is assumed to be low-frequency thermal noise. , , where , are the noises , Noise and the dissipative noise input vector on the amplitude of the CW mode in cavity a. Therefore, the noisy transmission spectrum can be written as:

[0084]

[0085] Since , it is approximated as , where is the transmission spectrum in the theoretical case.

[0086] In the presence of noise, the relationship between the frequency splitting of the measured valley points and the phase perturbation of the sensing unit is shown in (b) of Figure 2 . Under the interference of Gaussian noise, there are some fluctuations in the curve, but it does not prevent the identification of its trend and line type. This is due to the fact that the realization of the high-order scattering zeros does not bring noise amplification accompanied by the collapse of the eigenvalues. The eigenvalues of the Hamiltonian can have negative imaginary parts, and the evanescent fields in the solution will decay quickly and are more stable. It can be found that for small phase perturbations, the frequency splitting of the valley points and show an almost perfect fourth-root relationship, showing a fourth-order EP-like splitting behavior, that is, ∆W ∝ . However, as the perturbation increases, the fourth-root correlation relationship diverges, and the slope of the curve in the logarithmic coordinate axis increases, as shown in the inset of (b) in Figure 2 . In addition, the minimum detection limit is defined as the frequency fluctuation caused by the maximum noise, and the measured minimum detection limit is 0.12 - 0.18 MHz, that is, at least 0.001 rad (the noise is randomly generated in each measurement, so it is a range. The perturbation of 0.001 rad corresponds to a frequency splitting of 0.2 MHz without noise).

[0087] To further quantify the efficiency of the sensing platform of the present invention, the sensitivity χ = ∂ / ∂ is introduced. As shown in (a) of Figure 3 , it shows a divergence near the scattering zero. For an N-order EP sensor device, the frequency splitting response of its spectrum is proportional to the Nth root of the perturbation, that is, its sensitivity should show a divergence of the perturbation power near the EP, which further proves the EP-like characteristics of the fourth-order high-order scattering zeros. In fact, this is the case. Near a specific state, compared with a second-order EP sensor, the sensitivity of the fourth-order scattering zero sensing system is significantly higher.

[0088] Figure 2 Although it can be obtained from Figure 2As can be seen from (b) in [reference], noise does not cause significant fluctuations in the response curve. However, the non-linearity of the sensitivity to perturbations results in different degrees of measurement interference of noise for different perturbations.

[0089] To more comprehensively demonstrate the performance of the sensing scheme proposed in the present invention and further reveal the influence of noise on measurement, the signal-to-noise ratio is defined as the ratio of the valley point frequency splitting in the ideal case to the fluctuation of the valley point frequency splitting caused by noise. The variation of the signal-to-noise ratio with perturbations is as Figure 3 shown in (b) in [reference]. It can be seen that when the initial perturbation is small, the system sensitivity is very high, and the influence of noise on measurement is large, manifested as a relatively low signal-to-noise ratio. As the perturbation increases, although the sensitivity decreases, the degree of influence of noise on measurement decreases, manifested as the signal-to-noise ratio gradually increasing and tending to be stable.

[0090] As can be seen from the above, the balance between sensitivity and anti-interference ability can be achieved by changing the initial working point. The specific implementation method is to adjust the phase shifter to add an additional phase shift that changes the working point on the basis of the phase shift for implementing the scattering zero point.

[0091] In summary, for the high-order scattering zero point enhanced phase sensing platform proposed in the present invention, without adjusting the sensor parameters, only by controlling the control unit to implement the high-order scattering zero point and measuring the change of the transmission spectrum, the phase change at the sensor can be accurately measured. Here, the enhancement of the phase measurement sensitivity stems from the fourth root behavior of the zero points of the molecular polynomial in the transmission spectrum expression, which is the main factor determining the valley characteristics of the transmission spectrum. In addition, the small perturbations received by the system will be presented as amplified spectral changes. The valley frequency splitting of the transmission spectrum is proportional to the fourth root of the optical phase change under small perturbations, thereby realizing the enhanced measurement of the small signal of the induced phase change. Therefore, the present invention can expand the applicability of the high-order scattering zero point enhancement technology to conventional optical sensors. In addition, the platform of the present invention also has a noise feedback unit, which moves the working point to a position where the signal-to-noise ratio is within an acceptable range and the sensitivity is at least greater than the maximum value by monitoring the noise in the environment and feeding back the phase shift to achieve the balance between sensitivity and anti-interference ability.

[0092] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-order scattering zero-point enhanced phase sensing platform, characterized in that: The phase sensing platform includes a high-order scattering zero point control unit and a sensing unit. The sensor parameters do not need to be adjusted. The high-order scattering zero point is achieved by regulating the high-order scattering zero point control unit and measuring the change in the transmission spectrum, thereby measuring the phase change at the sensor. The sensing unit is an inserted external sensor separated from the high-order scattering zero point control unit, and the sensor can change the optical phase in response to the disturbance caused by the sensing target or the external field. The high-order scattering zero point control unit is a non-Hermitian multimode non-reciprocal optical system composed of two mutually coupled whispering gallery mode optical microcavities and a waveguide, and in the coupled whispering gallery mode optical microcavity group, a bidirectional coupling channel caused by scattering of an isotropic scatterer and a non-reciprocal unidirectional coupling channel caused by single-ended mirror reflection are respectively introduced. The two whispering gallery mode optical microcavities are respectively recorded as microcavity a and microcavity b; the high-order scattering zero point control unit also includes a bus waveguide, an interconnecting waveguide and a phase conversion device, the microcavity a is coupled with the bus waveguide, the detection light is input from port one of the bus waveguide, and the transmission spectrum is measured from port two of the bus waveguide; the microcavity b is coupled with the interconnecting waveguide, the left side of the interconnecting waveguide is connected to the phase conversion device and the sensing unit in sequence, and the right side is used as a non-reflection end; the phase conversion device is used to adjust the phase of the coupling coefficient to meet the conditional parameters for realizing the high-order scattering zero point.

2. The high-order scattering zero-point enhanced phase sensing platform according to claim 1 is characterized in that: Each of the whispering gallery mode optical microcavity supports two transmission modes, CW and CCW. The eigenfrequencies of the four modes are degenerate but the eigenvectors are mutually orthogonal.

3. The high-order scattering zero-point enhanced phase sensing platform according to claim 2 is characterized in that: Introducing a bidirectional coupling channel caused by scattering in the microcavity a, so that the CW mode and the CCW mode in the microcavity a are bidirectionally coupled; A non-reciprocal unidirectional coupling channel caused by single-ended mirror reflection is introduced into the microcavity b, so that the CCW mode in the microcavity b returns to the microcavity b through the reflection of the interconnected waveguide and the sensor unit, while the CW mode passes through the non-reflective end on the right side of the interconnected waveguide, introducing unidirectional coupling from the CCW mode to the CW mode.

4. The high-order scattering zero-point enhanced phase sensing platform according to claim 3 is characterized in that: The effective Hamiltonian of the high-order scattering zero control unit Represented as a 4×4 matrix: ； In the formula, is the resonant frequency of microcavity a and microcavity b, are the intrinsic losses of microcavity a and microcavity b respectively, is the gain of microcavity a, is the coupling coefficient between microcavity a and bus waveguide, and between microcavity b and interconnect waveguide; is the bidirectional coupling coefficient between CW and CCW modes caused by scattering in microcavity a, is the unidirectional coupling coefficient of the CCW mode in microcavity b reflected back to microcavity b through the interconnected waveguide and the sensing unit without the action of the optical phase signal, is the bidirectional coupling coefficient between microcavity a and microcavity b, where i represents the imaginary number.

5. The high-order scattering zero-point enhanced phase sensing platform according to claim 1 is characterized in that: The high-order scattering zero point control unit realizes a fourth-order quasi-singular point, which is specifically realized by constructing a fourth-order scattering zero point of a transmission spectrum.

6. The high-order scattering zero-point enhanced phase sensing platform according to claim 5 is characterized in that: The transmission spectrum is : ； In the formula, is the eigenvalue of the effective Hamiltonian H, , is a fourth-order polynomial related to frequency w, for The solution, The solution of is also the eigenvalue of the effective Hamiltonian H, .

7. The high-order scattering zero-point enhanced phase sensing platform according to claim 6 is characterized in that: The fourth-order scattering zero point of the transmission spectrum is constructed by controlling the coupling coefficient and gain-loss ratio of each part of the high-order scattering zero point control unit to make the transmission spectrum The roots of the fourth-order polynomial are all degenerate.

8. The high-order scattering zero-point enhanced phase sensing platform according to claim 1 is characterized in that: The phase sensing platform further comprises: The noise feedback unit is used to feed back the phase shift to the phase conversion device on the interconnected waveguide according to the influence of environmental noise on the signal-to-noise ratio under different disturbances and the sensitivity under different disturbances before the phase sensing platform measures, so as to adjust the working point of the high-order scattering zero point control unit, i.e., the non-Hermitian multimode non-reciprocal optical system, to a suitable position; the suitable position means that the signal-to-noise ratio is within a preset acceptance range and the sensitivity is greater than a preset standard threshold.

9. The high-order scattering zero-point enhanced phase sensing platform according to claim 8, characterized in that: The noise feedback unit is specifically implemented as follows: Introduce sensitivity to obtain the frequency splitting, sensitivity and phase disturbance response curves of the valley point of the phase sensing platform under ideal conditions; Obtaining a response curve of a signal-to-noise ratio and a disturbance under noise in a measurement environment; the signal-to-noise ratio is defined as a ratio of a valley point frequency splitting under an ideal condition to a valley point frequency splitting fluctuation caused by noise; Based on the above response curve, the position where the signal-to-noise ratio is within the preset acceptance range and the sensitivity is greater than the preset standard threshold is selected as the working point of the non-Hermitian multimode non-reciprocal optical system. The phase perturbation at this position is recorded as , and feed it back as a phase shift to the phase conversion device on the interconnected waveguide, so that it adds a phase shift that changes the working point on the basis of the phase shift of the scattering zero point.

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