Microwave photon state density detection system and method based on magneton-photon coupling effect

Abstract

The invention discloses a microwave photon state density detection system and method based on a magneton-photon coupling effect. Comprising the following steps: coupling a magneton mode in a yttrium iron garnet spherical microwave resonator with a microwave photon mode, enabling the square of the coupling strength to be in direct proportion to the local photon state density, and directly representing the photon state density in a microwave device by testing the frequency spectrum of magneton and microwave coupling and extracting the coupling strength. Different from a traditional method that a microwave antenna is used for detecting a radiation field to represent the photon state density, the method is not only suitable for photon state detection of an equivalent Hermite situation with consistent dissipation, but also suitable for non-Hermite photon state detection with non-consistent gain and dissipation. And the detection accuracy is not influenced by gain, dissipation and frequency range, and the method is a more universal, efficient and lossless detection scheme.

Description

Technical Field

[0001] The present invention relates to the field of near-field microwave testing and photon state density detection, and in particular to a microwave photon state density detection system and method based on magnon-photon coupling effect. Background Art

[0002] Microwave photon state density detection is of great significance in science and technology. It not only provides an in-depth understanding of the behavior of photons inside materials or devices, but also shows a wide range of application value in guiding microwave device design, biomedicine, environmental monitoring and other fields. With the sophistication of device design and the requirements of high-precision and non-destructive monitoring and sensing technology, it is necessary to propose an efficient, non-destructive and universally applicable photon state density detection method.

[0003] The traditional method of detecting microwave photon state density is to use microwave antenna to detect the local radiation field intensity in the device under test. This method is only applicable when the device under test is a Hermitian system, that is, each point in the device has consistent gain or dissipation. When the device under test is a non-Hermitian system, that is, each point in the device has inconsistent gain or dissipation, using microwave antenna to measure the radiation field intensity cannot truly reflect the local state density of photons, especially when the non-Hermitian property is large, the traditional detection method will be completely ineffective.

[0004] The traditional method of detecting microwave photon state density uses a non-resonant ring antenna as a probe, which makes it impossible to accurately predict the relationship between the coupling strength with the measured field and the frequency, and thus it is impossible to accurately characterize and compare the photon state density at different frequencies. Summary of the invention

[0005] Based on this, the present invention provides a microwave photon state density detection system and method based on the magnon-photon coupling effect, which has a wider range of applications and can be applied to microwave photon state density detection in both Hermitian and non-Hermitian situations. It is not limited by the test frequency, is more accurate, and is a non-invasive measurement method.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A microwave photon state density detection system based on the magneton-photon coupling effect comprises an electromagnet, a microwave device to be tested, a yttrium iron garnet spherical microwave resonator, a sample rod, a three-dimensional stepping motor, a computer control program and a vector network analyzer; the electromagnet is used to generate an adjustable bias magnetic field; the microwave device to be tested is used to provide an environment for the microwave photon state density to be tested; the yttrium iron garnet spherical microwave resonator is used to couple with the microwave photon mode in the microwave device to be tested; the sample rod is used to fix the yttrium iron garnet spherical microwave resonator; the three-dimensional stepping motor is used to accurately control the position of the sample rod; the computer control program is used to control the three-dimensional stepping motor, the electromagnet and the vector network analyzer; the vector network analyzer is used to test the scattering parameters of the microwave device to be tested;

[0008] The yttrium iron garnet spherical microwave resonator is connected to a three-dimensional stepper motor through a sample rod and placed on a microwave device to be tested, and the two are located together between the two-pole magnetic heads of an electromagnet; the computer control program controls the three-dimensional stepper motor to accurately move the yttrium iron garnet spherical microwave resonator on the microwave device to be tested, and at the same time controls the electromagnet to adjust the bias magnetic field, and tests the transmission spectrum of the coupling between the magnon and the microwave in the yttrium iron garnet spherical microwave resonator through a vector network analyzer to extract the coupling strength and characterize the microwave photon state density in the microwave device to be tested.

[0009] Furthermore, the microwave device to be tested includes but is not limited to a three-dimensional waveguide, a three-dimensional resonant cavity, a two-dimensional planar waveguide, and a two-dimensional planar resonator.

[0010] Furthermore, the microwave device to be tested includes any number of resonant circuits.

[0011] Furthermore, the magneton is a quantized description of a spin wave mode. In a yttrium iron garnet spherical resonator, a spin wave mode with consistent spin precession is generated by the combined action of an external bias magnetic field and a microwave field, and its resonance frequency ω m Flexible adjustment by bias magnetic field.

[0012] Further, the magnon mode is coupled to the microwave photon mode; comprising: adjusting the bias magnetic field so that the magnon resonance frequency ω m To the photon mode resonance frequency ω c At this point, the magneton and the photon couple to form two new eigenstates. Experimental observation of two new eigenstates of energy level ω ± , the magneton-photon coupling intensity g is obtained by fitting the following relationship:

[0013]

[0014] in, and are the complex eigenvalues ​​of the magnon and photon modes, respectively, for large detuning conditions, γm is the total dissipation rate of the magnon mode, γ r and κ r is the intrinsic dissipation and external dissipation rate of the photon mode; in strong coupling (g>γ m >γ c +κ c ) case, the coupling strength is equal to the energy level difference Δ=|ω + -ω - |half, that is: g=Δ / 2.

[0015] Furthermore, the local photon state density 1 / V c In essence, it is directly related to the magneton-microwave photon coupling intensity g, satisfying the relationship:

[0016]

[0017] where the constant η≤1 describes the spatial overlap and polarization matching of the magnon mode and the photon mode, χ is the gyromagnetic ratio of YTG, n is the number of spins in YTG, S=5 / 2 is the ground state spin number of the ferric ion, V c is the resonant frequency ω c The photon mode volume at .

[0018] Furthermore, by detecting the new eigenstate ω ± Get the square of the coupling strength g 2 , which can characterize the local photon state density 1 / V c ; In strong coupling (g>γ m >γ c +κ c ) is simplified to the state density being proportional to one-quarter of the square of the energy level difference, that is: 1 / V c ∝Δ 2 / 4.

[0019] Furthermore, the size of the yttrium iron garnet spherical microwave resonator is selected according to the geometric size of the resonance unit of the microwave device to be tested, and the larger the spatial overlap between the yttrium iron garnet sphere and each resonance unit structure, the better, and the polarization direction of the magnetons in the yttrium iron garnet sphere is as perpendicular to the microwave magnetic field component as possible.

[0020] Further, when the system is suitable for detecting the photon state density distribution of the same mode at different spatial positions, the yttrium iron garnet spherical microwave resonator has consistent crystal axis orientation and height relative to the plane to be measured at different positions.

[0021] A microwave photon state density detection method based on magnon-photon coupling effect comprises the following steps:

[0022] The yttrium iron garnet spherical microwave resonator is fixed on the sample rod, and its position is precisely controlled by a three-dimensional stepper motor;

[0023] Placing a yttrium iron garnet spherical microwave resonator and a microwave device to be tested between two pole magnetic heads of an electromagnet;

[0024] The bias magnetic field is changed by adjusting the coil current of the electromagnet through a computer control program;

[0025] The transmission spectrum of the magneton-microwave coupling in the YTG spherical microwave resonator was tested by vector network analyzer under different bias magnetic fields.

[0026] The coupling strength is extracted by fitting the transmission spectrum, and the microwave photon density of states is calculated.

[0027] The beneficial effects of the present invention are as follows: the present invention provides a microwave photon state density detection method that is generally applicable to Hermitian and non-Hermitian situations, and obtains a new eigenstate through the resonance valley or resonance peak of the transmission spectrum to obtain the coupling strength. The coupling strength is a direct representation of the photon state density, avoiding the influence of gain or dissipation on the test results and improving the detection accuracy. Microwave photons of different resonance frequencies have a deterministic effect on the magnon-microwave coupling intensity, and the effect can be deterministically described by a theoretical formula, so the detection scheme is suitable for microwave photon state density measurement in a wide frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of a microwave photon state density detection system provided by an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of the eigenstate of magnon-microwave coupling in an embodiment of the present invention;

[0030] Figure 3 It is a schematic diagram showing the characterization of microwave photon state density by taking non-Hermitian topological boundary states as an example in an embodiment of the present invention.

[0031] In the figure, there are an electromagnet 1, a microwave device to be tested 2, a yttrium iron garnet spherical microwave resonator 3, a sample rod 4, a three-dimensional stepping motor 5, a computer control program 6, and a vector network analyzer 7. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in combination with specific examples and with reference to the accompanying drawings.

[0033] The present invention provides a microwave photon state density detection system based on the magneton-photon coupling effect, and its overall structure is as follows: Figure 1As shown, it includes: an electromagnet 1 (the magnetic field strength is controlled by a high-precision current source through a coil), a microwave device to be tested 2, a yttrium iron garnet (YIG) spherical microwave resonator 3, a sample rod 4, a three-dimensional stepping motor 5, a computer control program 6, and a vector network analyzer 7.

[0034] In the example, the diameter of the YIG spherical microwave resonator 3 is 1 mm, and it is fixed at one end of the sample rod 4. The other end of the sample rod 4 is connected to a three-dimensional stepping motor 5. The position of the YIG spherical microwave resonator 3 is controllable by precise control of the three-dimensional stepping motor 5 by a computer control program 6.

[0035] The two ports of the vector network analyzer 7 are connected to the two ports of the microwave device 2 to be tested through coaxial cables to test the scattering parameters of the microwave device to be tested. In this example, the test transmission spectrum S is selected. 21 The applicable microwave devices to be tested include, but are not limited to, three-dimensional waveguides, three-dimensional resonant cavities, two-dimensional planar waveguides, and two-dimensional planar resonators. The applicable microwave devices to be tested may include any number of resonant circuits.

[0036] The YIG spherical microwave resonator 3 is placed on the microwave detection device 2, and the two are placed together between the two-pole magnetic heads of the electromagnet 1; the bias magnetic field between the magnetic heads causes the YIG spherical microwave resonator 3 to be saturated magnetized, and at the same time, the microwave field excites the YIG sphere to produce a spin wave mode with collective spin consistent precession, and its quantization is described as a magnon.

[0037] The computer control program 6 controls the three-dimensional stepping motor 5, the electromagnet 1 and the vector network analyzer 7 at the same time, so that the YIG spherical microwave resonator 3 can be accurately moved on the microwave device 2 to be tested. At a fixed state density position to be tested, the coil current of the scanning electromagnet 1 changes the bias magnetic field. Under different magnetic fields, the transmission spectrum S of the coupling between the magnon and the microwave in the YIG spherical microwave resonator 3 is obtained by testing with the vector network analyzer 7. 21 .

[0038] The resonant frequency ω of the magnon mode in the YIG sphere m It changes linearly with the bias magnetic field, such as Figure 2 As shown by the dotted line, when the bias magnetic field is adjusted to be equal to the microwave photon resonance frequency ω c When the test transmission spectrum S 21 ( Figure 2 The two resonance valleys shown in the inset have a resonance frequency ω ± They correspond to two new eigenstates formed by magnon-microwave coupling.

[0039] By coupling the magnon mode with the microwave photon mode in the YIG spherical microwave resonator, the square of the coupling strength is proportional to the local photon state density. By testing the spectrum of the magnon and microwave coupling and extracting the coupling strength, the microwave photon state density in the microwave device to be tested can be directly characterized.

[0040] Furthermore, the test magnon-microwave coupling spectrum S is fitted by the following formula: 21 (ω m ,ω), and the coupling strength g is obtained:

[0041]

[0042] in, and is the complex eigenvalue of the magnon and photon modes in the large detuned case (uncoupled), γ m is the total dissipation rate of the magnon mode, γ r and κ r are the intrinsic dissipation and external dissipation rates of the photon mode.

[0043] Optionally, when the magnon-microwave coupling is in the strong coupling region (g>γ m >γ c +κ c ),like Figure 2 The energy level splitting indicated by the double arrows in the figure, the coupling strength can be simplified to the energy level difference Δ=|ω + -ω - |half, that is: g=Δ / 2.

[0044] Furthermore, the photon state density 1 / V c In essence, it is directly proportional to the square of the coupling strength g 2 , satisfying the relationship:

[0045]

[0046] Among them, η≤1 is a constant, describing the spatial overlap and polarization matching of the magnon mode and the photon mode, χ is the gyromagnetic ratio of YIG, n is the spin number in YIG, S=5 / 2 is the ground state spin number of the trivalent iron ion, V c is the resonant frequency ω c The photon mode volume at .

[0047] Optionally, when the magnon-microwave coupling is in the strong coupling region (g>γ m >γ c +κ c ), the state density is proportional to one-quarter the square of the energy level difference, that is: 1 / V c ∝Δ 2 / 4.

[0048] The principles and methods of detecting photon state density based on coupling effect can be extended to any system with coupling interaction. The specific practice requires designing and selecting the object as the probe according to the detection frequency band and the type of coupling interaction.

[0049] It should be noted that in specific practice, the size of the YIG sphere used for detection needs to be selected according to the geometric dimensions of the resonant unit. When practice permits, the greater the spatial overlap between the YIG sphere and each resonant unit structure, the better, and the polarization direction of the magnetons in the YIG sphere should be as perpendicular to the microwave magnetic field component as possible.

[0050] For detecting the photon state density distribution of the same mode at different spatial positions, it should be ensured that the YIG sphere has a consistent crystal axis orientation at different positions and a consistent height relative to the plane to be measured.

[0051] The present invention provides a microwave photon state density detection method based on the magneton-photon coupling effect, comprising the following steps:

[0052] A yttrium iron garnet spherical microwave resonator 3 is fixed on a sample rod 4, and its position is precisely controlled by a three-dimensional stepping motor 5; the yttrium iron garnet spherical microwave resonator 3 and the microwave device 2 to be tested are placed between the two pole magnetic heads of an electromagnet 1; the coil current of the electromagnet 1 is adjusted by a computer control program 6 to change the bias magnetic field; under different bias magnetic fields, the transmission spectrum of the coupling between magnons and microwaves in the yttrium iron garnet spherical microwave resonator 3 is tested by a vector network analyzer 7; the coupling strength is extracted by fitting the transmission spectrum, and the microwave photon state density is calculated.

[0053] exist Figure 3 In the embodiment shown, the non-Hermitian topological boundary state in the planar waveguide is used as an example for detection. The non-Hermitian topological lattice contains 12 resonant units and has two topological boundary states with one large and one small dissipation. The simulation results of the microwave magnetic field distribution show that for microwaves input from the left port and output from the right port, the field distribution is exponentially localized at the left end of the lattice, and only one boundary state with small dissipation is presented (if the microwave input direction is opposite, only another boundary state with large dissipation localized on the right is presented), which shows that the characterization of the state density only by detecting the radiation field through the microwave antenna is not accurate and comprehensive enough.

[0054] exist Figure 3 In the embodiment shown, the method of the present invention is used to detect microwave photon state density, the height (about 0.2 mm) of the YIG ball relative to the microwave device 2 to be tested and the crystal axis orientation are kept constant, the YIG ball is moved to each resonant unit position in the non-Hermitian topological lattice, and the square of the coupling strength obtained by testing at each position is as follows: Figure 3 As shown in the scattered points, it is in good agreement with the theoretical photon state density distribution (bar graph), where blue and red represent the photon state density distribution with small dissipation and large dissipation, respectively.

[0055] The test method does not rely on the observed scattering parameter S ij , S ij represents the transmission coefficient from port j to port i, that is, whether it is the detection S 21 , S 12 Or S 11 , S 22 , does not affect the coupling intensity and the detection results of microwave photon state density. This method is applicable to photon state density detection in both Hermitian and non-Hermitian cases, and is a more efficient, non-destructive and accurate detection method.

[0056] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A microwave photon state density detection system based on magneton-photon coupling effect, characterized in that: The invention comprises an electromagnet, a microwave device to be tested, a yttrium iron garnet spherical microwave resonator, a sample rod, a three-dimensional stepping motor, a computer control program and a vector network analyzer; the electromagnet is used to generate an adjustable bias magnetic field; the microwave device to be tested is used to provide an environment of microwave photon state density to be tested; the yttrium iron garnet spherical microwave resonator is used to couple with the microwave photon mode in the microwave device to be tested; the sample rod is used to fix the yttrium iron garnet spherical microwave resonator; the three-dimensional stepping motor is used to accurately control the position of the sample rod; the computer control program is used to control the three-dimensional stepping motor, the electromagnet and the vector network analyzer; the vector network analyzer is used to test the scattering parameters of the microwave device to be tested; The yttrium iron garnet spherical microwave resonator is connected to a three-dimensional stepper motor through a sample rod and placed on a microwave device to be tested, and the two are located together between the two-pole magnetic heads of an electromagnet; the computer control program controls the three-dimensional stepper motor to accurately move the yttrium iron garnet spherical microwave resonator on the microwave device to be tested, and at the same time controls the electromagnet to adjust the bias magnetic field, and tests the transmission spectrum of the coupling between the magnon and the microwave in the yttrium iron garnet spherical microwave resonator through a vector network analyzer to extract the coupling strength and characterize the microwave photon state density in the microwave device to be tested.

2. The microwave photon state density detection system based on the magneton-photon coupling effect according to claim 1 is characterized in that: The microwave device to be tested includes but is not limited to a three-dimensional waveguide, a three-dimensional resonant cavity, a two-dimensional planar waveguide, and a two-dimensional planar resonator.

3. The microwave photon state density detection system based on the magneton-photon coupling effect according to claim 1 is characterized in that: The microwave device to be tested includes any number of resonant circuits.

4. The microwave photon state density detection system based on the magneton-photon coupling effect according to claim 1 is characterized in that: The magnon is a quantized description of the spin wave mode. In the yttrium iron garnet spherical resonator, the spin wave mode with consistent spin precession is generated by the combined action of the external bias magnetic field and the microwave field. Its resonance frequency ω m Flexible adjustment by bias magnetic field.

5. The microwave photon state density detection system based on the magneton-photon coupling effect according to claim 1 is characterized in that: Coupling the magnon mode to the microwave photon mode; comprising: adjusting the bias magnetic field to make the magnon resonance frequency ω m To the photon mode resonance frequency ω c At this point, the magneton and the photon couple to form two new eigenstates. Experimental observation of two new eigenstates of energy level ω ± , the magneton-photon coupling intensity g is obtained by fitting the following relationship: in, and are the complex eigenvalues ​​of the magnon and photon modes, respectively, for large detuning conditions, γ m is the total dissipation rate of the magnon mode, γ r and κ r is the intrinsic dissipation and external dissipation rate of the photon mode; in strong coupling (g>γ m >γ c +κ c ) case, the coupling strength is equal to the energy level difference Δ=|ω + -ω - |half, that is: g=Δ / 2.

6. The microwave photon state density detection system based on the magneton-photon coupling effect according to claim 5 is characterized in that: Local photon state density 1 / V c In essence, it is directly related to the magneton-microwave photon coupling intensity g, satisfying the relationship: where the constant η≤1 describes the spatial overlap and polarization matching of the magnon mode and the photon mode, X is the gyromagnetic ratio of YTG, n is the number of spins in YTG, S=5 / 2 is the ground state spin number of the ferric ion, V c is the resonant frequency ω c The photon mode volume at .

7. The microwave photon state density detection system based on the magneton-photon coupling effect according to claim 6 is characterized in that: By detecting the new eigenstate ω ± Get the square of the coupling strength g 2 , which can characterize the local photon state density 1 / V c ; In strong coupling (g>γ m >γ c +κ c ) is simplified to the state density being proportional to one-quarter of the square of the energy level difference, that is: 1 / V c ∝Δ 2 / 4.

8. The microwave photon state density detection system based on the magneton-photon coupling effect according to claim 1 is characterized in that: The size of the yttrium iron garnet spherical microwave resonator is selected according to the geometric size of the resonance unit of the microwave device to be tested, and the larger the spatial overlap between the yttrium iron garnet sphere and each resonance unit structure, the better, and the polarization direction of the magneton in the yttrium iron garnet sphere is as perpendicular to the microwave magnetic field component as possible.

9. The microwave photon state density detection system based on the magneton-photon coupling effect according to claim 1, characterized in that: When the system is suitable for detecting the photon state density distribution of the same mode at different spatial positions, the yttrium iron garnet spherical microwave resonator has consistent crystal axis orientation and height relative to the plane to be measured at different positions.

10. A microwave photon state density detection method based on magnon-photon coupling effect, characterized in that: The following steps are involved: The yttrium iron garnet spherical microwave resonator is fixed on the sample rod, and its position is precisely controlled by a three-dimensional stepper motor; Placing a yttrium iron garnet spherical microwave resonator and a microwave device to be tested between two pole magnetic heads of an electromagnet; The bias magnetic field is changed by adjusting the coil current of the electromagnet through a computer control program; The transmission spectrum of the magneton-microwave coupling in the YTG spherical microwave resonator was tested by vector network analyzer under different bias magnetic fields. The coupling strength is extracted by fitting the transmission spectrum, and the microwave photon density of states is calculated.

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