A light isolating device and method based on the photomagnetization effect without an external magnetic field

Abstract

The application discloses a kind of based on optical magnetization effect's no additional magnetic field optical isolating device and method, belong to atomic optics and inertial measurement technical field, the device includes polarization control component, atomic gas chamber module and signal detection component;Polarization control component is separated by beam splitter prism and atomic gas chamber module into drive light control component, signal light control component;Atomic gas chamber module includes: square glass gas chamber, non-magnetic heating oven;Wherein, square glass gas chamber is placed in non-magnetic heating oven;Non-magnetic heating oven is provided with temperature gradient structure for making the temperature of square glass gas chamber light passing surface higher than the temperature of other regions of square glass gas chamber: the non-light passing side wall of square glass gas chamber is in contact with ambient air and radiates, and light passing surface is in close contact with the main body of non-magnetic heating oven 7 by heat-conducting silicone grease.The device does not need additional magnetic field, with the advantages of high isolation, wide bandwidth and integration.

Description

Technical Field

[0001] This invention belongs to the field of atomic optics and inertial measurement technology, specifically relating to a photo-magnetization effect-based optical isolation device and method without an external magnetic field. Background Technology

[0002] In the field of ultra-high sensitivity inertial measurement, spin exchange relaxation-free (SERF) atomic spin inertial measurement instruments represent a significant next-generation development direction. These instruments utilize the spin polarization of alkali metal atoms to sense the carrier's angular velocity, thus requiring the system to operate in an extremely low magnetic field (near-zero magnetic field) environment. The semiconductor laser, as the core component of the SERF inertial measurement instrument, is highly susceptible to optical feedback reflected from the optical path, leading to unstable output power and frequency, thereby increasing the noise of the inertial measurement instrument system.

[0003] To suppress feedback light in the optical path, magneto-optical isolators based on the Faraday effect are typically used. However, magneto-optical isolators rely on permanent magnets to generate a strong magnetic field to operate, which introduces a very large external magnetic field into SERF inertial measurement instruments, disrupting the SERF states of atoms and causing the instruments to malfunction. While existing non-magnetic optical isolation technologies (such as electromagnetically induced transparency, photomechanical induction, and nonlinear optical effects) do not require a magnetic field, they generally suffer from low isolation, high insertion loss, narrow bandwidth (typically only a few MHz), large system size, and difficulty in integration. In particular, existing optically induced magnetization (OIM) schemes generally face engineering challenges such as polarization degradation caused by beam splitters, low isolation efficiency and narrow isolation bandwidth, low polarization efficiency of alkali metal atoms, easy condensation on the light-transmitting surface of the gas cell leading to decreased transmittance, magnetic interference from heating circuits, and poor real-time performance in isolation measurement, making it difficult to meet the application requirements of high performance, miniaturization, and long-term stability. Therefore, there is an urgent need for an optical isolator that can achieve high isolation, wide isolation bandwidth, compact structure, and requires no external magnetic field. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] An optical isolation device without an external magnetic field based on photomagnetization effect includes: a polarization control component, an atomic gas cell module, and a signal detection component;

[0006] The polarization control component is divided into a drive light control component and a signal light control component by a beam splitter and an atomic gas cell module, with the atomic gas cell module located between the drive light control component and the signal light control component;

[0007] The atomic gas chamber module includes: a square glass gas chamber filled with alkali metal atoms and a buffer gas, and a non-magnetic heating oven; wherein, the square glass gas chamber is placed inside the non-magnetic heating oven; the square glass gas chamber is filled with nitrogen gas at a specific pressure as a buffer gas; the non-magnetic heating oven is made of a non-magnetic material with high thermal conductivity and is equipped with a temperature gradient structure to make the temperature of the light-transmitting surface of the square glass gas chamber higher than that of other areas of the square glass gas chamber; the non-light-transmitting sidewall of the square glass gas chamber is in contact with the outside air for heat dissipation, and the light-transmitting surface is in close contact with the main body of the non-magnetic heating oven through thermally conductive silicone grease;

[0008] The signal detection component includes a beam splitter, an avalanche photodiode, an FPGA signal processing circuit, and a host computer; the beam splitter is positioned between the drive light control component and the atomic gas chamber module; the avalanche photodiode is positioned in the direction of the reflected light path of the beam splitter; the output terminal of the avalanche photodiode is sequentially connected to the FPGA signal processing circuit and the host computer.

[0009] A method for optical isolation without an external magnetic field based on photomagnetization effect, used in the aforementioned optical isolation device without an external magnetic field based on photomagnetization effect, comprising:

[0010] Step 1: Use a non-magnetic heating circuit to drive a non-magnetic heating oven to heat the square glass air chamber to the working state to increase the density of alkali metal atoms inside; and rely on the temperature gradient structure of the non-magnetic heating oven to make the temperature of the light-transmitting surface of the air chamber higher than that of other areas, so as to prevent alkali metal atoms from condensing on the light-transmitting surface of the square glass air chamber.

[0011] Step 2: Lock the frequencies of the laser driving light and signal light emitted by the external laser source component to the D1 line transition frequency of the alkali metal atom.

[0012] Step 3: Adjust the polarization state of the driving light by the driving light control component to make it pure left-handed circularly polarized light incident in the square glass gas cell in the forward direction, pumping the alkali metal atoms in the square glass gas cell to the ground state Zeeman level, so that the atomic medium exhibits polarized transparency characteristics to circularly polarized light of a specific rotation direction.

[0013] Step 4: During the debugging phase, the polarization state of the signal light is adjusted by the signal light control component, including: adjusting and fixing the second quarter-wave plate at a specific angle so that the signal light becomes pure right-handed circularly polarized light and is incident in the opposite direction into the square glass gas cell. At this time, the polarization state of the signal light corresponds to the strong absorption transition channel of the atom, which is absorbed and blocked by the square glass gas cell.

[0014] Step 5: The beam splitter leads part of the reverse signal light to the avalanche photodiode for photoelectric conversion. The FPGA signal processing circuit collects and calculates the converted signal in real time to obtain the real-time isolation degree. The data is fed back to the host computer to generate an isolation degree curve. Based on the isolation degree curve, corresponding fine-tuning is performed to make the photo-magnetized optical isolation device without external magnetic field reach the optimal working condition.

[0015] The present invention has the following beneficial effects:

[0016] (1) This invention utilizes the photomagnetization effect and non-magnetic structure design to realize non-reciprocal transmission of light, and solves the technical problem that the strong magnetic field generated by the traditional magneto-optical isolator seriously interferes with the normal operation of magnetic sensitive systems such as SERF (Spin Exchange Relaxation Free) atomic spin inertial measurement devices.

[0017] (2) By adding a phase compensation half-wave plate to the polarization control component, the present invention cancels the phase delay error introduced by the beam splitting element in the optical path, ensuring that the driving light incident on the atomic gas cell maintains extremely high circular polarization purity. This solves the engineering problem in the existing photomagnetization isolation scheme where circular polarization degradation is caused by inherent defects of optical elements, which in turn leads to low atomic polarization efficiency and limited maximum isolation.

[0018] (3) By introducing nitrogen gas at a specific pressure (e.g., 60 Torr) into the atomic gas chamber as a buffer gas, the present invention restricts the diffusion movement of alkali metal atoms, reduces the collision depolarization between atoms and the gas chamber wall, significantly improves the isolation bandwidth and maximum isolation of the device, and solves the problems of narrow bandwidth and low isolation efficiency of existing non-magnetic optical isolation schemes.

[0019] (4) This invention uses aluminum nitride (AlN) material with high thermal conductivity to make a non-magnetic heating oven, and with the local heat conduction design to build a temperature gradient where the temperature of the light-transmitting surface is higher than that of other areas, effectively preventing alkali metal atoms from condensing at the light-transmitting window of the gas chamber, ensuring high light transmittance, reducing insertion loss, and solving the problem of performance degradation and poor long-term stability of existing photomagnetization devices due to condensation of the light-transmitting surface.

[0020] (5) This invention uses high-frequency alternating current (e.g., 100kHz) to drive a non-magnetic heating circuit. It utilizes the principle that the frequency of the high-frequency magnetic field is much higher than the bandwidth of the atomic magnetic resonance response to prevent the magnetic field generated by the heating current from interfering with the spin polarization state of the atom. This solves the problem of the introduction of magnetic noise or the need to add a thick magnetic shielding layer in the prior art, which leads to a large volume.

[0021] (6) By integrating an FPGA-based signal processing unit and a photoelectric detection circuit, this invention enables real-time acquisition and calculation of the isolation signal of the device during the debugging process, and realizes visualized monitoring of the device performance. This solves the problem of poor real-time performance and reliance on external instruments for calculation during the debugging process of the previous non-magnetic optical isolator, and greatly speeds up the operator's parameter fine-tuning speed. Attached Figure Description

[0022] Figure 1This is a schematic diagram of the optical isolation device without external magnetic field based on photomagnetization effect of the present invention; wherein, 1-first half-wave plate, 2-first polarizing beam splitter, 3-second half-wave plate, 4-first quarter-wave plate, 5-beam splitter, 6-square glass gas chamber, 7-non-magnetic heating oven, 8-second quarter-wave plate, 9-second polarizing beam splitter, 10-third half-wave plate, 11-avalanche photodiode, 12-FPGA signal processing circuit, 13-host computer, 14-non-magnetic heating circuit. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] like Figure 1 As shown, the present invention provides an optical isolation device (or simply device) based on photomagnetization effect without external magnetic field, comprising: a polarization control component, an atomic gas cell module, and a signal detection component.

[0025] An external laser source component is also required to provide laser light with a frequency locked to the D1 line transition frequency of alkali metal atoms (such as Rb). This laser light consists of a driving light and a signal light; the driving light and the signal light have the same frequency, and the power of the driving light is greater than that of the signal light, with an intensity ratio greater than 10:1. Figure 1 As shown, the driving light is defined to propagate in the forward direction, that is, it enters from the leftmost side of the device and propagates to the right; the signal light is defined to propagate in the reverse direction, that is, it enters from the rightmost side of the device and propagates to the left. The driving light and the signal light achieve beam overlap (beam combining) within the atomic gas cell module.

[0026] Specifically, such as Figure 1 As shown, the positions and connections of the components of the device are as follows:

[0027] The polarization control component is divided into a drive light control component and a signal light control component by the beam splitter 5 and the atomic gas cell module. The atomic gas cell module is located between the drive light control component and the signal light control component.

[0028] The driving light control assembly includes a first half-wave plate 1, a first polarizing beam splitter 2, a second half-wave plate 3, and a first quarter-wave plate 4. The function of the driving light control assembly is to adjust the optical power and polarize the incident driving light using the first half-wave plate 1 in conjunction with the first polarizing beam splitter 2. Then, the second half-wave plate 3 performs phase compensation, and the first quarter-wave plate 4 delays the phase, resulting in high-purity circularly polarized light. Specifically, the second half-wave plate 3 compensates for the polarization degradation introduced by the beam splitter 5 in the optical path, ensuring that the driving light incident on the square glass gas chamber 6 is high-purity circularly polarized light.

[0029] The signal light control component includes a third half-wave plate 10, a second polarizing beam splitter 9, and a second quarter-wave plate 8 arranged sequentially along the signal light propagation direction. The function of the signal light control component is to convert the incident signal light into circularly polarized light and direct it into the square glass gas cell 6, thus cooperating with the subsequent signal detection component to complete the isolation measurement. The second polarizing beam splitter 9 and the third half-wave plate 10 are used to adjust the signal light power and polarize it.

[0030] The atomic gas chamber module is positioned between the two parts of the polarization control component. It includes: a square glass gas chamber 6 filled with alkali metal atoms and a buffer gas, a non-magnetic heating oven 7, a non-magnetic heating circuit 14, and an insulating shell (not shown in the figure); wherein, the square glass gas chamber 6 is placed inside the non-magnetic heating oven 7, the non-magnetic heating circuit 14 is electrically connected to a non-magnetic flexible heating film (not shown in the figure) attached to the surface of the non-magnetic heating oven 7, and the insulating shell covers the outside of the non-magnetic heating oven 7 to reduce heat loss.

[0031] The square glass chamber 6 is filled with nitrogen gas at a specific pressure as a buffer gas to suppress atomic depolarization and widen the isolation bandwidth. The non-magnetic heating oven 7 is made of a high thermal conductivity non-magnetic material (aluminum nitride, AlN), and is cylindrical with a square cavity inside to house the square glass chamber 6. It is designed with a temperature gradient structure to ensure that the temperature of the light-transmitting surface of the square glass chamber 6 is higher than that of other areas of the chamber. Specifically, the non-light-transmitting sidewall of the square glass chamber 6 is exposed to the outside air for heat dissipation, while the light-transmitting surface is in close contact with the main body of the non-magnetic heating oven 7 through thermally conductive silicone grease. This design makes the temperature of the light-transmitting surface 0.03℃-1℃ higher than that of other walls of the chamber, thereby preventing alkali metal condensation.

[0032] The non-magnetic heating circuit 14 uses a high-frequency sine wave (100kHz) to drive the non-magnetic flexible heating film attached to the surface of the non-magnetic heating oven 7, which can greatly reduce the interference magnetic field generated during heating.

[0033] The signal detection assembly includes a beam splitter prism 5, an avalanche photodiode 11, an FPGA signal processing circuit 12, and a host computer 13. Their positions are as follows: Figure 1As shown, the beam splitter 5 is positioned between the first part of the polarization control component (driving light control component) and the atomic gas cell module; the avalanche photodiode 11 is positioned in the direction of the reflected light path of the beam splitter 5 (perpendicular to the light paths of the driving light and signal light); the output terminal of the avalanche photodiode 11 is sequentially connected to the FPGA signal processing circuit 12 and the host computer 13. The reflected light path of the beam splitter 5 is perpendicular to the main light path where the driving light and signal light are located; the avalanche photodiode 11 is positioned in the reflected light path, and its photosensitive window faces the reflected beam.

[0034] The avalanche photodiode 11 is used to receive the signal light that passes through the square glass air chamber 6 from right to left and is reflected by the beam splitter prism 5. It converts the optical power of the signal light into a photovoltage signal and sends the photovoltage signal of the avalanche photodiode 11 to the FPGA signal processing circuit 12 to realize the real-time acquisition and calculation of the isolation signal. The signal is then sent to the host computer 13 to generate an isolation curve, which is convenient for the operator to observe and fine-tune the polarization control component or the heating temperature of the square glass air chamber 6.

[0035] The best embodiment of the invention is as follows: Figure 1 As shown, it mainly consists of a polarization control component, an atomic gas cell module, and a signal detection component.

[0036] The external incident light source uses a distributed feedback semiconductor laser (DFB), with the wavelength locked to... 87 The D1 line (794.98 nm) of Rb atoms. In the optical path design, the driving light and the signal light use the same wavelength light source.

[0037] In the atomic gas chamber module: a square glass gas chamber 6 (with dimensions such as 15×15×15mm) is filled with isotopes. 87 Rb and 60 Torr nitrogen were used as buffer gases. Experimental results showed that this measure significantly enhanced the collision between atoms and the buffer gas, reduced the mean free path of atoms, and prolonged the interaction time of atoms in the beam region, thereby increasing the 20dB isolation bandwidth from the MHz level to the GHz level (2.93GHz in this embodiment). Since copper may generate magnetic field interference under high current, aluminum nitride (AlN) was used as the material for the non-magnetic heating oven 7. AlN has high thermal conductivity (approximately 170 W / (m·K)) and insulating non-magnetic properties. The temperature of the square glass gas chamber 6 was controlled by the non-magnetic heating circuit 14. The non-magnetic heating circuit 14 adopted a single-chip microcomputer-based digital proportional-integral-derivative (PID) circuit to generate a 100kHz sine wave, which was then amplified by an operational amplifier circuit and applied to the non-magnetic flexible heating film. The non-magnetic flexible heating film was designed to counteract the magnetic field generated during the heating process, which could be controlled to the tens of nT level.

[0038] This invention further provides a method for optical isolation without an external magnetic field based on photomagnetization effect, which is applied to the above-mentioned optical isolation device without an external magnetic field based on photomagnetization effect. The specific workflow is as follows:

[0039] Step 1: The non-magnetic heating circuit 14 drives the non-magnetic heating oven 7 to heat the square glass air chamber 6 to the working state to increase the internal alkali metal atom density; and relying on the temperature gradient structure of the non-magnetic heating oven 7, the temperature of the light-transmitting surface of the air chamber is higher than that of other areas, preventing alkali metal atoms from condensing on the light-transmitting surface of the square glass air chamber 6.

[0040] Step 2: Lock the frequencies of the driving light and signal light emitted by the external laser source component to the D1 line transition frequency of the alkali metal atom.

[0041] Step 3: The polarization state of the driving light is adjusted by the first part of the polarization control component (driving light control component) so that it becomes pure left-handed circularly polarized light incident in the square glass gas cell 6. This pumps the alkali metal atoms in the square glass gas cell 6 to the ground state Zeeman level, so that the atomic medium exhibits polarized transparency to circularly polarized light of a specific rotation direction.

[0042] Step 4: During the debugging phase, the polarization state of the signal light is adjusted through the second part of the polarization control component (signal light control component). Specifically, the second quarter-wave plate 8 is adjusted and fixed at a specific angle so that the signal light becomes pure right-handed circularly polarized light and is incident in the opposite direction onto the square glass gas cell 6. At this time, the polarization state of the signal light corresponds to the strong absorption transition channel of the atom, which is absorbed and blocked by the square glass gas cell 6, thereby achieving optical isolation.

[0043] Step 5: The beam splitter 5 leads part of the reverse signal light to the avalanche photodiode 11 for photoelectric conversion. The FPGA signal processing circuit 12 collects and calculates the converted signal in real time to obtain the real-time isolation degree and feeds the data back to the host computer 13 to generate an isolation degree curve. The operator makes corresponding fine adjustments according to the displayed isolation degree curve to make the device reach the optimal working condition.

[0044] The working principle of this invention is as follows: The device first uses a non-magnetic heating circuit 14 to drive a non-magnetic heating oven 7, increasing the density of alkali metal atoms in the square glass chamber 6 by raising the temperature. The temperature gradient designed in the oven ensures that the temperature of the light-transmitting surface of the square glass chamber 6 is slightly higher than that of other areas of the square glass chamber 6, forcing atoms to condense in other areas of the square glass chamber 6, completely eliminating adhesion to the light-transmitting surface and ensuring extremely low optical path insertion loss. The appropriate amount of buffer gas filled into the square glass chamber 6 effectively restricts the diffusion thermal motion of atoms and reduces the wall collision depolarization rate.

[0045] After the temperature of the square glass chamber 6 stabilizes, when the driving light is polarized by the first part of the polarization control component, a second half-wave plate 3 is introduced for phase pre-compensation to counteract the phase delay of the optical path beam splitter prism 5, resulting in pure left-handed circularly polarized light. This beam efficiently pumps the atoms in the square glass chamber 6 to a specific ground-state Zeeman level, breaking the thermodynamic equilibrium and photomagnetizing the medium in the absence of a magnetic field. At this time, the reverse-incident signal light is transformed into pure right-handed circularly polarized light by the second part of the polarization control component and is incident back into the square glass chamber 6. Its function is to simulate the reflected light in the actual optical path. This circularly polarized light with this rotation direction precisely corresponds to the strong absorption channel of the polarized atoms and is strongly absorbed and dissipated in the square glass chamber 6, thereby achieving efficient optical isolation.

[0046] In addition, the system guides the signal light to the avalanche photodiode 11 through the beam splitter prism 5, where the FPGA signal processing circuit 12 performs high-speed acquisition and digital calculation of the isolation data, and feeds the isolation data back to the host computer 13. This closed-loop monitoring mechanism allows the operator to intuitively fine-tune the angle and temperature parameters of the polarization control component, ensuring that the isolation device is always in optimal operating condition.

[0047] This invention also relates to a miniaturized integrated design of the aforementioned device, which integrates a polarization control component and an atomic gas cell module. When integrated with the SERF inertial measurement system, this photomagnetization-based, magnetic field-free optical isolation device, fixed to the output port of the semiconductor laser, effectively blocks reflected light in the optical path without requiring an external magnetic shield, and does not cause broadening of the magnetic resonance linewidth in the SERF atomic gas cell, verifying its excellent non-magnetic characteristics.

[0048] The above description is merely an embodiment of the present invention and does not limit the scope of the invention. Any equivalent structural or procedural transformations made based on the description and drawings of this invention, or direct or indirect applications in other related system fields, are similarly included within the protection scope of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A photo-magnetization-based optical isolation device without an external magnetic field, characterized in that, include: Polarization control components, atomic gas cell module, and signal detection components; The polarization control component is divided into a drive light control component and a signal light control component by a beam splitter and an atomic gas cell module, with the atomic gas cell module located between the drive light control component and the signal light control component. The atomic gas chamber module includes: a square glass gas chamber filled with alkali metal atoms and a buffer gas, and a non-magnetic heating oven; wherein, the square glass gas chamber is placed inside the non-magnetic heating oven; the square glass gas chamber is filled with nitrogen gas at a specific pressure as a buffer gas; the non-magnetic heating oven is made of a non-magnetic material with high thermal conductivity and is equipped with a temperature gradient structure to make the temperature of the light-transmitting surface of the square glass gas chamber higher than that of other areas of the square glass gas chamber; the non-light-transmitting sidewall of the square glass gas chamber is in contact with the outside air for heat dissipation, and the light-transmitting surface is in close contact with the main body of the non-magnetic heating oven through thermally conductive silicone grease; The signal detection component includes a beam splitter, an avalanche photodiode, an FPGA signal processing circuit, and a host computer; the beam splitter is positioned between the drive light control component and the atomic gas chamber module; the avalanche photodiode is positioned in the direction of the reflected light path of the beam splitter; the output terminal of the avalanche photodiode is sequentially connected to the FPGA signal processing circuit and the host computer.

2. The optical isolation device without external magnetic field based on photomagnetization effect according to claim 1, characterized in that, Also includes: An external laser source component is used to provide a laser whose frequency is locked at the transition frequency of the D1 line of alkali metal atoms. The laser is divided into a driving light and a signal light. The driving light and the signal light have the same frequency, and the power of the driving light is greater than that of the signal light. The reflected light path of the beam splitter is perpendicular to the main light path where the driving light and the signal light are located. The avalanche photodiode is placed on the reflected light path, and its photosensitive window is directly facing the reflected beam.

3. The optical isolation device without external magnetic field based on photomagnetization effect according to claim 2, characterized in that, The external incident light source is a distributed feedback semiconductor laser.

4. The optical isolation device without external magnetic field based on photomagnetization effect according to claim 1, characterized in that, The non-magnetic heating oven is cylindrical with a square cavity inside.

5. The optical isolation device without external magnetic field based on photomagnetization effect according to claim 1, characterized in that, The driving light control assembly includes a first half-wave plate, a first polarizing beam splitter, a second half-wave plate, and a first quarter-wave plate arranged sequentially along the driving light path; The function of the driving light control component is to adjust the optical power of the incident driving light and polarize it in conjunction with the first half-wave plate and the first polarizing beam splitter. Then, after phase compensation by the second half-wave plate and phase delay by the first quarter-wave plate, high-purity circularly polarized light is generated. The second half-wave plate is used to compensate for the polarization degradation introduced by the beam splitter in the optical path, ensuring that the driving light incident on the square glass gas cell is high-purity circularly polarized light. The signal light control component includes a third half-wave plate, a second polarizing beam splitter, and a second quarter-wave plate arranged sequentially along the signal light propagation direction; it is used to convert the incident signal light into circularly polarized light and incident it into a square glass gas cell; wherein, the second polarizing beam splitter and the third half-wave plate are used to adjust the signal light power and polarize it.

6. The optical isolation device without external magnetic field based on photomagnetization effect according to claim 1, characterized in that, The atomic gas chamber module also includes a non-magnetic heating circuit and an insulating shell; the non-magnetic heating circuit is electrically connected to a non-magnetic flexible heating film attached to the surface of the non-magnetic heating oven, and the insulating shell covers the outside of the non-magnetic heating oven to reduce heat loss.

7. The optical isolation device without external magnetic field based on photomagnetization effect according to claim 6, characterized in that, The non-magnetic heating circuit uses a high-frequency sine wave to drive the non-magnetic flexible heating film attached to the surface of the non-magnetic heating oven.

8. The optical isolation device without external magnetic field based on photomagnetization effect according to claim 1, characterized in that, Aluminum nitride is used as the material for the non-magnetic heating oven.

9. The optical isolation device without external magnetic field based on photomagnetization effect according to claim 6, characterized in that, The non-magnetic heating circuit uses a microcontroller-based digital proportional-integral-differential circuit. The generated sine wave is amplified by an operational amplifier circuit and then applied to the non-magnetic flexible heating film.

10. A method for optical isolation without an external magnetic field based on photomagnetization effect, used in any one of claims 1 to 9, characterized in that, include: Step 1: Use a non-magnetic heating circuit to drive a non-magnetic heating oven to heat the square glass air chamber to the working state to increase the density of alkali metal atoms inside; and rely on the temperature gradient structure of the non-magnetic heating oven to make the temperature of the light-transmitting surface of the air chamber higher than that of other areas, so as to prevent alkali metal atoms from condensing on the light-transmitting surface of the square glass air chamber. Step 2: Lock the frequencies of the driving light and signal light emitted by the external laser source component to the D1 line transition frequency of the alkali metal atom. Step 3: Adjust the polarization state of the driving light by the driving light control component to make it pure left-handed circularly polarized light incident in the square glass gas cell in the forward direction, pumping the alkali metal atoms in the square glass gas cell to the ground state Zeeman level, so that the atomic medium exhibits polarized transparency characteristics to circularly polarized light of a specific rotation direction. Step 4: During the debugging phase, the polarization state of the signal light is adjusted by the signal light control component, including: adjusting and fixing the second quarter-wave plate at a specific angle so that the signal light becomes pure right-handed circularly polarized light and is incident in the opposite direction into the square glass gas cell. At this time, the polarization state of the signal light corresponds to the strong absorption transition channel of the atom, which is absorbed and blocked by the square glass gas cell. Step 5: The beam splitter leads part of the reverse signal light to the avalanche photodiode for photoelectric conversion. The FPGA signal processing circuit collects and calculates the converted signal in real time to obtain the real-time isolation degree. The data is fed back to the host computer to generate an isolation degree curve. Based on the isolation degree curve, corresponding fine-tuning is performed to make the photo-magnetized optical isolation device without external magnetic field reach the optimal working condition.

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