Optical isolator

Abstract

The invention discloses an optical isolator, which relates to the field of passive optical devices and comprises a first collimator, a second collimator, a first optical rotation assembly, a second optical rotation assembly, a first polarizing beam splitter, a second polarizing beam splitter, a third polarizing beam splitter, a fourth polarizing beam splitter and a shell. Compared with a conventional optical isolator, the optical isolator has the advantages that depolarization of the magneto-optical crystal caused by a thermally induced birefringence effect can be compensated by utilizing the additional magneto-optical crystal and the quartz optical rotation sheet, the isolation degree of the optical isolator during incidence of high-power laser is improved, and the effective bearing power of the optical isolator is improved.

Description

Technical Field

[0001] The invention belongs to the field of passive optical devices, and in particular relates to an optical isolator. Background Art

[0002] An optical isolator is a passive optical device that allows light to pass in one direction and blocks light from passing in the opposite direction. It is a key component in high-power laser systems, used to block the return light of the system to prevent it from damaging the light source. As the power of lasers continues to increase, the power requirements of optical isolators are also increasing.

[0003] The current optical isolator is mainly based on the Faraday effect, which realizes unidirectional light transmission by causing the polarization direction of polarized light to rotate non-reciprocally under the action of a magnetic field. An optical isolator is usually composed of components such as a polarizer, a Faraday rotator and an analyzer.

[0004] The Faraday rotator, the core component of the current optical isolator, is prone to thermal effects under the action of high-power lasers, especially the thermally induced birefringence effect, which causes its performance to deteriorate. In addition, the structural design of traditional optical isolators may not be sufficient to withstand the high intensity of lasers under high-power conditions, resulting in device damage or shortened life. Therefore, the application of existing optical isolators in high-power laser systems is limited and it is difficult to meet the growing demand for high-power lasers. Summary of the invention

[0005] The object of the present invention is to provide an optical isolator to solve the problem that the isolation of the existing optical isolator is reduced due to the thermally induced birefringence effect in a high power environment, thereby improving the isolation of the optical isolator.

[0006] The technical solution for achieving the purpose of the present invention is: an optical isolator, comprising a first collimator, a second collimator, a first optical rotator component, a second optical rotator component, a first polarization beam splitter, a second polarization beam splitter, a third polarization beam splitter, a fourth polarization beam splitter and a shell; wherein the first collimator, the second collimator, the first optical rotator component, the second optical rotator component, the first polarization beam splitter, the second polarization beam splitter, the third polarization beam splitter and the fourth polarization beam splitter are all arranged in the shell; the first collimator, the first polarization beam splitter, the first optical rotator component and the second polarization beam splitter are arranged in sequence along the first optical axis; the third polarization beam splitter, the second optical rotator component, the fourth polarization beam splitter and the second collimator are arranged in sequence along the second optical axis; the first optical axis is parallel to the second optical axis; the third polarization beam splitter is located in the reflection light path of the first polarization beam splitter; the fourth polarization beam splitter is located in the reflection light path of the second polarization beam splitter.

[0007] The isolation iso of the optical isolator satisfies the following formula:

[0008]

[0009] Among them, α is the absorption coefficient of the magneto-optical crystal, κ is the thermal conductivity of the magneto-optical crystal, L is the length of light in the magneto-optical crystal, ζ is the optical anisotropy parameter of the magneto-optical crystal, Q is the thermo-optical coefficient of the magneto-optical crystal, λ is the wavelength of the incident light, P0 is the incident light power, F is the magnetic field inhomogeneity, and A1 and A2 are coefficients.

[0010] Compared with the prior art, the present invention has the following significant advantages:

[0011] The optical isolator includes a permanent magnet with high magnetic induction intensity, which reduces the length of the magneto-optical crystal and thus reduces the thermally induced birefringence effect of the magneto-optical crystal, and includes an additional magneto-optical crystal and a quartz rotator plate for compensating for the thermally induced birefringence effect of the magneto-optical crystal, thereby improving the isolation degree when a high-power laser is incident, thereby increasing the carrying power of the optical isolator. Meanwhile, the existing optical isolators usually use a polarization beam splitter prism or a beam splitter plate, while the present invention uses a polarization beam splitter, which is more conducive to integration and thus reduces the volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the structure of the optical isolator of the present invention.

[0013] Figure 2 It is a schematic diagram of the forward transmission light path of the optical isolator of the present invention.

[0014] Figure 3 It is a schematic diagram of the reverse transmission light path of the optical isolator of the present invention.

[0015] Figure 4 It is a schematic diagram of the structure of the permanent magnet included in the optical isolator of the present invention.

[0016] Figure 5 This is a graph showing how the isolation of the optical isolator in the implementation case and the optical isolator in the prior art changes with the incident laser power.

[0017] Figure 6 It is a graph showing the variation of the axial magnetic induction intensity on the axis of the permanent magnet with the distance in the implementation case. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation case methods described herein are only used to illustrate and explain the case of the present invention, and are not used to limit the embodiments of the present invention.

[0019] The Faraday rotator commonly included in existing optical isolators includes a permanent magnet and a magneto-optical crystal. Due to the anisotropy of the magneto-optical crystal, there is an obvious thermally induced birefringence effect under high-power laser incidence conditions, which causes the depolarization of linearly polarized light and thus leads to a decrease in isolation.

[0020] like Figure 1As shown, the optical isolator of the present invention comprises a first collimator 1, a second collimator 2, a first optical rotator assembly 3, a second optical rotator assembly 4, a first polarization beam splitter 5, a second polarization beam splitter 6, a third polarization beam splitter 7, a fourth polarization beam splitter 8 and a housing 9. The first collimator 1, the second collimator 2, the first optical rotator assembly 3, the second optical rotator assembly 4, the first polarization beam splitter 5, the second polarization beam splitter 6, the third polarization beam splitter 7 and the fourth polarization beam splitter 8 are all arranged in the housing 9; the first collimator 1, the first polarization beam splitter 5, the first optical rotator assembly 3 and the second polarization beam splitter 6 are arranged in sequence along the first optical axis; the third polarization beam splitter 7, the second optical rotator assembly 4, the fourth polarization beam splitter 8 and the second collimator 2 are arranged in sequence along the second optical axis; the first optical axis is parallel to the second optical axis; the third polarization beam splitter 7 is located in the reflection light path of the first polarization beam splitter 5; the fourth polarization beam splitter 8 is located in the reflection light path of the second polarization beam splitter 6.

[0021] The first optical rotation component 3 includes a first λ / 2 wave plate 35 and a first Faraday rotator 30; the first Faraday rotator 30 includes a first magneto-optical crystal 31, a second magneto-optical crystal 32, a first quartz optical rotator 33 and a first permanent magnet 34; wherein the first permanent magnet 34 is in a ring shape, and the first magneto-optical crystal 31, the second magneto-optical crystal 32 and the first quartz optical rotator 33 are arranged at intervals at the center of the ring along a first optical axis; the second optical rotation component 4 includes a second λ / 2 wave plate 45 and a second Faraday rotator 40; the second Faraday rotator 40 includes a third magneto-optical crystal 41, a fourth magneto-optical crystal 42, a second quartz optical rotator 43 and a second permanent magnet 44; wherein the second permanent magnet 44 is in a ring shape, and the third magneto-optical crystal 41, the fourth magneto-optical crystal 42 and the second quartz optical rotator 43 are arranged at intervals at the center of the ring along a second optical axis.

[0022] like Figure 2 As shown, the first permanent magnet 34 is the same as the second permanent magnet 44; the permanent magnet includes a first annular magnet 11, a second annular magnet 12, a third annular magnet 13, a magnet-conducting sleeve 14 and a permanent magnet housing 15. The first annular magnet 11, the second annular magnet 12 and the third annular magnet 13 are coaxially arranged in the magnet-conducting sleeve 14 in sequence, and the permanent magnet housing 15 is sleeved outside the magnet-conducting sleeve 14.

[0023] The first annular magnet 11 is composed of 10 sector magnets, made of N48M, with an inner diameter of 24mm, an outer diameter of 120mm, a thickness of 50mm, and is magnetized from the outside to the inside in a direction perpendicular to the axis; the second annular magnet 12 is made of N38H, with an inner diameter of 24mm, an outer diameter of 110mm, and a thickness of 35mm, and is magnetized along the axis from the third annular magnet 13 toward the first annular magnet 11. The third annular magnet 13 is composed of 10 sector magnets, made of N48M, with an inner diameter of 24mm, an outer diameter of 120mm, and a thickness of 50mm, and is magnetized from the inside to the outside in a direction perpendicular to the axis; the magnetic conductive sleeve 14 is made of pure iron material, which can effectively prevent demagnetization, and the permanent magnet housing 15 is made of copper material, which can effectively conduct heat. The axial magnetic induction intensity on the permanent magnet axis is as follows Figure 5 As shown, the magnetic induction intensity distribution of the permanent magnet of this embodiment has a wider flat area and a larger magnetic induction intensity. Using the magnetic field in the middle flat part, the magneto-optical rotation effect shows that the magnetic field parallel to the light propagation direction will cause the rotation angle of the polarization direction of the transmitted light to be:

[0024] θ=VBL (1)

[0025]

[0026] Where V is the Verdet coefficient of the medium, L is the length of the light in the magneto-optical crystal, and B z is the magnetic induction intensity along the light propagation direction z, and B is the average magnetic induction intensity.

[0027] like Figure 3As shown, the forward incident polarization-independent light beam is expanded and collimated by the first collimator 1, and is split into two beams of a first vertical polarized light and a first horizontal polarized light whose polarization directions are perpendicular to each other after passing through the first polarization beam splitter 5, wherein the first vertical polarized light continues to propagate along the incident direction, and the horizontal polarized light is reflected at an angle of 45°, that is, the emitting direction of the first vertical polarized light forms an angle of 90° with the first horizontal polarized light, and the reflected first horizontal polarized light propagates to the third polarization beam splitter 7 and is reflected again at an angle of 45°. Subsequently, after the first vertical polarized light passes through the first λ / 2 wave plate 34, the first magneto-optical crystal 31, the first quartz rotator 33 and the second magneto-optical crystal 32 in sequence, the polarization direction of the polarized light rotates 90° clockwise to become the second horizontal polarized light; wherein the first λ / 2 wave plate 34 rotates the polarized light by 67.5° clockwise, the first magneto-optical crystal 31 rotates the polarization direction of the polarized light by 22.5° counterclockwise, the first quartz rotator 33 rotates the polarization direction of the polarized light by 67.5° clockwise, and the fourth magneto-optical crystal 32 rotates the polarized light by 22.5° counterclockwise. After the first horizontal polarized light passes through the second λ / 2 wave plate 45, the third magneto-optical crystal 41, the second quartz rotator 43 and the fourth magneto-optical crystal 42 in sequence, the polarization direction of the light rotates 90° clockwise to become the second vertical polarized light; wherein the second λ / 2 wave plate 45 rotates the polarized light clockwise by 67.5°, the third magneto-optical crystal 41 rotates the polarization direction of the polarized light counterclockwise by 22.5°, the second quartz rotator 43 rotates the polarization direction of the polarized light clockwise by 67.5°, and the fourth magneto-optical crystal 42 rotates the polarized light counterclockwise by 22.5°. At this time, the second horizontal polarized light is reflected by the second polarization beam splitter 6 and the fourth polarization beam splitter 8 in sequence at an angle of 45°, and the second vertical polarized light propagates in the original direction after passing through the fourth polarization beam splitter 8; the second vertical polarized light and the second horizontal polarized light are combined into a polarization-independent light beam after passing through the fourth polarization beam splitter 8, and coupled to the optical fiber output through the second collimator 2.

[0028] like Figure 4As shown, the reverse incident polarization-independent light beam is expanded and collimated by the second collimator 2, and is split into two beams of a third vertical polarized light and a third horizontal polarized light with mutually perpendicular polarization directions after passing through the fourth polarization beam splitter 8, wherein the third vertical polarized light continues to propagate along the incident direction, and the third horizontal polarized light is reflected at an angle of 45°, that is, the third vertical polarized light exit direction forms an angle of 90° with the third horizontal polarized light, and the reflected third horizontal polarized light propagates to the second polarization beam splitter 6 and is reflected again at an angle of 45°. The third vertical polarized light is still vertically polarized light after passing through the fourth magneto-optical crystal 42, the second quartz rotator 43, the third magneto-optical crystal 41, and the second λ / 2 wave plate 45 in sequence; wherein the fourth magneto-optical crystal rotates the polarization direction of the polarized light by 22.5° clockwise, the second quartz rotator rotates the polarization direction of the polarized light by 67.5° clockwise, the third magneto-optical crystal rotates the polarized light by 22.5° clockwise, and the second λ / 2 wave plate rotates the polarized light by 112.5° counterclockwise. The third horizontal polarized light passes through the second magneto-optical crystal 32, the first quartz rotator 33, the first magneto-optical crystal 31 and the first λ / 2 wave plate 35 in sequence, and is still horizontally polarized light; wherein, the second magneto-optical crystal 32 rotates the polarization direction of the polarized light by 22.5° clockwise, the second quartz rotator 33 rotates the polarization direction of the polarized light by 67.5° clockwise, the first magneto-optical crystal 31 rotates the polarized light by 22.5° clockwise, and the first λ / 2 wave plate 35 rotates the polarized light by 112.5° counterclockwise. At this time, the third vertical polarized light continues to propagate to the housing 9 along the original direction after passing through the third polarization beam splitter 7, and the third horizontal polarized light is reflected at 45° by the first polarization beam splitter 5 and propagates to the housing 9, and the housing 9 is provided with a black trap-shaped light absorber to absorb the two beams of light.

[0029] The isolation iso of the optical isolator of the present invention satisfies formula (3):

[0030] iso=-10log(γ)=-10log(γ1+γ2) (3)

[0031] Wherein, γ is the degree of depolarization, γ1 is the degree of depolarization caused by the radial inhomogeneity of the magnetic field, γ2 is the depolarization caused by the depolarization due to the thermally induced birefringence effect, and γ1 satisfies formula (4):

[0032]

[0033] Where ξ is the normalized radial coordinate of the magneto-optical crystal, a is the characteristic radius of the beam, R is the radius of the magneto-optical medium, I(ξ) is the optical power density at position ξ, P0 is the incident optical power, is the angle difference between the actual magneto-optical rotation angle and the ideal magneto-optical rotation angle at position ξ, Satisfying formula (5):

[0034]

[0035] in, is the ideal magneto-optical rotation angle, ξ* is the position of the ideal magneto-optical rotation angle, B(ξ) is the average magnetic induction intensity at the position ξ, and B(ξ*) is the average magnetic induction intensity at the position ξ*. is the magneto-optical rotation angle at position ξ, is the magneto-optical rotation angle at position ξ*. The radial distribution of magnetic induction intensity of the permanent magnet cross section of this embodiment satisfies formula (6):

[0036] B(ξ)=B0[1+Fξ] (6) Wherein, B0 is the average magnetic induction intensity at the center of the permanent magnet cross section, and F is the magnetic field inhomogeneity. At this time, the depolarization degree γ1 caused by the radial inhomogeneity of the magnetic field satisfies equation (7):

[0037]

[0038] The depolarization γ2 caused by the depolarization due to the thermally induced birefringence effect satisfies the formula (8):

[0039]

[0040] Where ρ is the radial coordinate of the magneto-optical crystal, I(ρ) is the power density at position ρ, Γ(ρ) is the degree of local depolarization at position ρ, and Γ(ρ) satisfies equation (9):

[0041]

[0042] Among them, E in (ρ) is the input light complex amplitude of the optical rotation component at position ρ, E out (ρ) is the output light complex amplitude of the optical rotation component at position ρ, is a unit vector perpendicular to the polarization direction of the ideal output light, E out (ρ) and E in (ρ) satisfies formula (10):

[0043]

[0044] Among them, δ lin is the linear phase retardation caused by the thermally induced birefringence effect, δ c is the circular birefringence phase delay caused by the magneto-optical rotation effect, and the total phase delay δ lin Satisfying formula (11):

[0045]

[0046] Where L is the length of light in the magneto-optical crystal, ζ is the optical anisotropy parameter of the magneto-optical crystal, ρ is the radial coordinate, is the polar angle, Q is the thermo-optical coefficient of the magneto-optical crystal, λ is the wavelength of the incident light, and T is the temperature of the magneto-optical crystal. When the incident light is a Gaussian beam, the isolation of the optical isolator satisfies equation (12):

[0047]

[0048] Among them, α is the absorption coefficient of the magneto-optical crystal, κ is the thermal conductivity of the magneto-optical crystal, and the coefficient A1 and the coefficient A2 are both constants, and they satisfy equations (13) and (14) respectively:

[0049]

[0050] like Figure 6 The first magneto-optical crystal 31, the second magneto-optical crystal 32, the third magneto-optical crystal 41 and the fourth magneto-optical crystal 42 are all cylindrical TGG crystals, the crystal axis orientation of the TGG crystals is

[001] , the length of the TGG crystals is 6.3 mm and the diameter is 12.7 mm. When the isolation of the optical isolator of the present invention is greater than 30 dB, the incident light power is greater than 1500 W, and under different incident light power conditions, it is better than the conventional optical isolator without thermally induced birefringence effect compensation, which improves the isolation of the optical isolator when high-power laser is incident, that is, the effective carrying power of the optical isolator is improved.

Claims

1. An optical isolator, characterized in that: The invention comprises a first collimator (1), a second collimator (2), a first optical rotation component (3), a second optical rotation component (4), a first polarization beam splitter (5), a second polarization beam splitter (6), a third polarization beam splitter (7), a fourth polarization beam splitter (8) and a housing (9); wherein the first collimator (1), the second collimator (2), the first optical rotation component (3), the second optical rotation component (4), the first polarization beam splitter (5), the second polarization beam splitter (6), the third polarization beam splitter (7) and the fourth polarization beam splitter (8) are all arranged in the housing. (9); a first collimator (1), a first polarization beam splitter (5), a first optical rotation component (3) and a second polarization beam splitter (6) are arranged in sequence along the first optical axis; a third polarization beam splitter (7), a second optical rotation component (4), a fourth polarization beam splitter (8) and a second collimator (2) are arranged in sequence along the second optical axis; the first optical axis is parallel to the second optical axis; the third polarization beam splitter (7) is located in the reflection light path of the first polarization beam splitter (5); and the fourth polarization beam splitter (8) is located in the reflection light path of the second polarization beam splitter (6).

2. The optical isolator according to claim 1, characterized in that: The first optical rotation component (3) comprises a first λ / 2 wave plate (35) and a first Faraday rotator (30); the first Faraday rotator (30) comprises a first magneto-optical crystal (31), a second magneto-optical crystal (32), a first quartz optical rotator (33) and a first permanent magnet (34); wherein the first permanent magnet (34) is in the shape of a ring, and the first magneto-optical crystal (31), the second magneto-optical crystal (32) and the first quartz optical rotator (33) are arranged at intervals at the center of the ring along a first optical axis; The second optical rotation component (4) comprises a second λ / 2 wave plate (45) and a second Faraday rotator (40); the second Faraday rotator (40) comprises a third magneto-optical crystal (41), a fourth magneto-optical crystal (42), a second quartz optical rotation plate (43) and a second permanent magnet (44); wherein the second permanent magnet (44) is in the shape of a ring, and the third magneto-optical crystal (41), the fourth magneto-optical crystal (42) and the second quartz optical rotation plate (43) are arranged at intervals at the center of the ring along a second optical axis.

3. The optical isolator according to claim 2, characterized in that: The first permanent magnet (34) is the same as the second permanent magnet (44); the permanent magnet comprises a first annular magnet (11), a second annular magnet (12), a third annular magnet (13), a magnetic conductive sleeve (14) and a permanent magnet housing (15); the first annular magnet (11), the second annular magnet (12) and the third annular magnet (13) are coaxially arranged in sequence in the magnetic conductive sleeve (14), and the permanent magnet housing (15) is sleeved outside the magnetic conductive sleeve (14).

4. The optical isolator according to claim 3, characterized in that: The first annular magnet (11) is magnetized from outside to inside in a direction perpendicular to the axis; the second annular magnet (12) is magnetized along the axis from the third annular magnet (13) toward the first annular magnet (11), and the third annular magnet (13) is magnetized from inside to outside in a direction perpendicular to the axis; the magnetic conductor sleeve (14) is made of pure iron material, which can effectively prevent demagnetization, and the permanent magnet housing (15) is made of copper material, which can effectively conduct heat.

5. The optical isolator according to claim 4, characterized in that: The forward incident polarization-independent light beam is expanded and collimated by a first collimator (1), and is split into two beams of a first vertical polarized light and a first horizontal polarized light whose polarization directions are perpendicular to each other after passing through a first polarization beam splitter (5), wherein the first vertical polarized light continues to propagate along the incident direction, and the horizontal polarized light is reflected at an angle of 45°, that is, the exit direction of the first vertical polarized light forms an angle of 90° with the first horizontal polarized light, and the reflected first horizontal polarized light propagates to a third polarization beam splitter (7) and is reflected again at an angle of 45°; then the first vertical polarized light continues to propagate along the incident direction, and the horizontal polarized light is reflected at an angle of 45°. After the light passes through the first λ / 2 wave plate 34, the first magneto-optical crystal (31), the first quartz rotator (33) and the second magneto-optical crystal (32) in sequence, the polarization direction of the polarized light rotates 90 degrees clockwise to become the second horizontally polarized light; wherein the first λ / 2 wave plate 34 rotates the polarized light clockwise by 67.5 degrees, the first magneto-optical crystal (31) rotates the polarization direction of the polarized light counterclockwise by 22.5 degrees, the first quartz rotator (33) rotates the polarization direction of the polarized light clockwise by 67.5 degrees, and the fourth magneto-optical crystal rotates the polarization direction of the polarized light counterclockwise by 22.5 degrees. (32) rotates the polarized light counterclockwise by 22.5°; after the first horizontally polarized light passes through the second λ / 2 wave plate (45), the third magneto-optical crystal (41), the second quartz rotator (43) and the fourth magneto-optical crystal (42) in sequence, the polarization direction of the light rotates 90° clockwise to become the second vertically polarized light; wherein the second λ / 2 wave plate (45) rotates the polarized light clockwise by 67.5°, the third magneto-optical crystal (41) rotates the polarization direction of the polarized light counterclockwise by 22.5°, the second quartz rotator (4 3) the polarization direction of the polarized light is rotated 67.5° clockwise, and the fourth magneto-optical crystal (42) rotates the polarized light 22.5° counterclockwise; at this time, the second horizontal polarized light is reflected by the second polarization beam splitter (6) and the fourth polarization beam splitter (8) at an angle of 45° in sequence, and the second vertical polarized light propagates in the original direction after passing through the fourth polarization beam splitter (8); the second vertical polarized light and the second horizontal polarized light are combined into a polarization-independent light beam after passing through the fourth polarization beam splitter (8), and coupled to the optical fiber output through the second collimator 2; The reverse incident polarization-independent light beam is expanded and collimated by the second collimator (2), and is split into two beams of a third vertical polarized light and a third horizontal polarized light with polarization directions perpendicular to each other after passing through a fourth polarization beam splitter (8), wherein the third vertical polarized light continues to propagate along the incident direction, and the third horizontal polarized light is reflected at an angle of 45°, that is, the third vertical polarized light exit direction forms an angle of 90° with the third horizontal polarized light, and the reflected third horizontal polarized light propagates to the second polarization beam splitter (6) and is reflected again at an angle of 45°; the third vertical polarized light is still vertically polarized light after passing through the fourth magneto-optical crystal (42), the second quartz rotator (43), the third magneto-optical crystal (41) and the second λ / 2 wave plate (45) in sequence; wherein the fourth magneto-optical crystal rotates the polarization direction of the polarized light by 22.5° in the clockwise direction, the second quartz rotator rotates the polarization direction of the polarized light by 67.5° in the clockwise direction, and the third magneto-optical crystal rotates the polarized light by 2° in the clockwise direction. The second λ / 2 wave plate rotates the polarized light by 22.5° in the clockwise direction, and the second λ / 2 wave plate rotates the polarized light by 112.5° in the counterclockwise direction. The third horizontally polarized light passes through the second magneto-optical crystal (32), the first quartz rotator (33), the first magneto-optical crystal (31) and the first λ / 2 wave plate (35) in sequence, and is still horizontally polarized light. The second magneto-optical crystal (32) rotates the polarization direction of the polarized light by 22.5° in the clockwise direction, and the second quartz rotator (33) rotates the polarization direction of the polarized light in the clockwise direction. The first magneto-optical crystal (31) rotates the polarized light by 22.5° in the clockwise direction, and the first λ / 2 wave plate (35) rotates the polarized light by 112.5° in the counterclockwise direction; at this time, the third vertical polarized light passes through the third polarization beam splitter (7) and continues to propagate in the original direction to the housing (9), and the third horizontal polarized light passes through the first polarization beam splitter (5) and is reflected at 45° and then propagates to the housing (9), and the housing (9) is provided with a black trap-shaped light absorber to absorb the two beams of light.

6. The optical isolator according to claim 5, characterized in that: The isolation iso of the optical isolator satisfies the following formula: Among them, α is the absorption coefficient of the magneto-optical crystal, κ is the thermal conductivity of the magneto-optical crystal, L is the length of light in the magneto-optical crystal, is the optical anisotropy parameter of the magneto-optical crystal, Q is the thermo-optic coefficient of the magneto-optical crystal, λ is the wavelength of the incident light, p0 is the incident light power, F is the magnetic field inhomogeneity, and A1 and A2 are both coefficients.

7. The optical isolator according to claim 6, characterized in that A1 satisfies the following formula: 。 8. The optical isolator according to claim 6, characterized in that: A2 satisfies the following formula: 。

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