A fully polarized optical isolator

Abstract

The present invention discloses a fully polarized light isolator, which is based on a non-Hermitian system designed by combining anisotropic gain loss with the Faraday effect to achieve the effect of full polarization blocking. It can be achieved by combining a single-layer film with polarization performance with multiple layers of dielectric materials, magneto-optical materials, and metal structures with gain. This method can obtain a new type of fully polarized light isolator based on a non-Hermitian system, which has the advantages of requiring fewer optical elements, low energy loss, even achieving negative loss (gain), and good isolation effect.

Description

Technical Field

[0001] The invention belongs to the field of optical isolators, and in particular relates to a fully polarized optical isolator. Background Art

[0002] An optical isolator is an optical element that allows light to be transmitted in one direction but not in the opposite direction. If an optical isolator is not installed at the laser output end, the reflected light will enter the laser, causing the laser oscillation characteristics to deteriorate, the output intensity to fluctuate (generating intensity noise) and the oscillation wavelength to change (generating phase noise).

[0003] The principle of polarization-dependent optical isolator is that the forward incident signal light becomes linearly polarized light after passing through the 0-degree polarizer, and the polarization direction of the signal light is rotated 45 degrees clockwise / counterclockwise through the Faraday gyromagnetic medium and the magnetic field, and just allows low loss to pass through the analyzer placed at 45 degrees to the polarizer. For reverse light, when the linear polarized light out of the analyzer passes through the placement medium, the deflection direction is also rotated 45 degrees clockwise / counterclockwise, so that the polarization direction of the reverse light is orthogonal to the direction of the polarizer, completely blocking the transmission of the reflected light.

[0004] However, this common isolation device requires two polarizers to achieve full-angle optical isolation, which occupies a relatively large space.

[0005] CN209879056U and CN110488511B disclose an optical isolator that works at all angles. Without affecting the forward light transmission, the return light with a certain angle and not blocked by the light entrance aperture and the light exit aperture is deflected to the outside of the light transmission area that deviates from the light entrance aperture, so as to avoid coupling to the inside of the optical fiber and causing damage to the laser, thereby achieving the effect of full-angle operation. Disadvantages: 1. Many optical elements are required; 2. Reflection or scattering is used, which is not conducive to packaging integration; 3. Large energy loss; CN104656287A provides a new ultra-thin optical isolator and its manufacturing method, a method for making an ultra-thin optical isolator by mounting a polarizing polymer film on a magneto-optical crystal Faraday rotator. Disadvantages: Double-sided coating requires high precision. Summary of the invention

[0006] In order to solve the technical problems existing in the background technology, the present invention aims to provide a fully polarized light isolator, which only requires a single polarizer and occupies a small space; only requires a single layer of polarization film, and is simpler to produce; light transmission can achieve no loss or gain, and the isolation effect is better.

[0007] In order to solve the technical problem, the technical solution of the present invention is:

[0008] A fully polarized light isolator comprises: a fiber collimator, and a polarizer and a composite magneto-optical crystal arranged in sequence along the light path emitted by the fiber collimator, wherein a magnet is arranged on the side of the composite magneto-optical crystal;

[0009] Wherein, the dielectric tensor ε of the composite magneto-optical crystal meets the following conditions:

[0010]

[0011] ε0 represents the dielectric constant, γ represents the gain or loss coefficient, Δ represents the loss, and u represents the magneto-optical parameter, where u=γ.

[0012] Furthermore, the magnets are distributed on both sides of the composite magneto-optical crystal.

[0013] Furthermore, the incident light emitted by the fiber collimator is rotated 45 degrees clockwise from vertical polarization through the polarizer, which is recorded as +45 degrees; then the incident light passes through the composite magneto-optical crystal with a polarization direction of +45 degrees, and after passing through the composite magneto-optical crystal, the incident light is rotated 90 degrees counterclockwise, evolving into the eigenstate of the dielectric tensor of the composite magneto-optical crystal material, -45 degrees.

[0014] Furthermore, the reverse incident light, after polarized incidence, will evolve into the eigenstate of the magneto-optical material at -45 degrees, which is orthogonal to the polarizer at +45 degrees, thus achieving an isolation effect.

[0015] Furthermore, the composite magneto-optical crystal includes: a sheet magneto-optical material layer, a semiconductor gain medium layer and a loss medium layer.

[0016] Furthermore, the sheet-like magneto-optical material layer, the semiconductor gain medium layer and the loss medium layer are cross-arranged and bonded together to form a composite magneto-optical crystal.

[0017] Furthermore, the lossy dielectric layer includes: a metal strip and an insulating medium, and the metal strip and the insulating medium are combined with each other to form the lossy dielectric layer.

[0018] Furthermore, the semiconductor gain medium layer is made of gallium arsenide.

[0019] Furthermore, the insulating medium is made of quartz.

[0020] Furthermore, the metal strip is made of Au.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] Based on the non-Hermitian system designed by combining anisotropic gain loss with the Faraday effect, the full polarization blocking effect can be achieved. It can be achieved by combining a single layer of thin film with polarization performance with multiple layers of dielectric materials, magneto-optical materials, and metal structures with gain. This method can obtain a new type of full polarization optical isolator based on a non-Hermitian system, which has the advantages of fewer optical components required, low energy loss, even negative loss (gain), and good isolation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 , a structural diagram of a fully polarized optical isolator of the present invention;

[0024] Figure 2 , Line graph of reflected light isolation in different polarization states when the insertion loss is 0;

[0025] Figure 3 , Line graph of reflected light isolation in different polarization states when the forward transmission energy increases 10 times;

[0026] Figure 4 , and the structure diagram of composite magneto-optical materials. DETAILED DESCRIPTION

[0027] The specific implementation mode of the present invention is described below in conjunction with embodiments:

[0028] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0029] At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0030] Example 1

[0031] A fully polarized optical isolator, such as Figure 1 As shown, it includes a fiber collimator 11, a polarizer 12, and a dielectric tensor 13 arranged in sequence. A composite magneto-optical crystal material 13 in the form of a magneto-optical crystal having a magnet 14 disposed around the magneto-optical crystal;

[0032] The polarizer rotates 45 degrees clockwise from vertical polarization (represented as +45 degrees). After the light signal passes through the polarizer, it passes through the magneto-optical crystal material with a polarization direction of +45 degrees. Finally, the outgoing light rotates 90 degrees counterclockwise and evolves into the eigenstate (-45 degrees) of the dielectric tensor of the magneto-optical material.

[0033] The reverse incident light, regardless of any polarization, will eventually evolve into the eigenstate of the magneto-optical material (-45 degrees), which is orthogonal to the polarizer (+45 degrees), achieving an isolation effect. When the thickness of the magneto-optical material is 3mm, the isolation effect is as follows: Figure 2 As shown, for reflected light of any polarization, the minimum isolation can reach 65dB, and at this time there is no loss in forward transmission;

[0034] Keeping the thickness of magneto-optical material at 3 mm, after appropriately changing the gain-loss parameters, the following can be achieved: Figure 3 The effect shown is that when the forward transmission energy is increased by 10 times, the reverse isolation can still reach about 50dB, achieving the effect of forward gain and reverse isolation;

[0035] The magneto-optical material crystal that meets the requirements can be formed by cross-arranging a common sheet magneto-optical material layer 21, a semiconductor gain medium layer 22, and a loss layer composed of a metal 23 and an insulating medium 24. Figure 4 The composite magneto-optical material shown in the figure can make the emitted light meet the above dielectric tensor form and achieve the effect of no loss or gain by selecting different materials to adjust the corresponding gain / loss parameters;

[0036] The polarizer can be realized by coating a single layer of a thin film with polarization properties on the composite magneto-optical material, for example, a grating structure can be coated.

[0037] The parameters in the material parameter configuration of the present invention can be adjusted, and the total length needs to be adjusted accordingly. The composite material of this configuration can have this property.

[0038] For example, the thickness of the sheet magneto-optical material layer (21), the semiconductor gain medium layer (22) and the loss medium layer can be selected as 100um, 35um and 15um respectively, and 20 layers of the above materials can be combined and cross-arranged to form a composite magneto-optical crystal (13). Of course, the more layers, the better the effect. The preferred magneto-optical crystal material is bismuth-doped yttrium iron garnet (Bi:YIG), cerium-doped yttrium iron garnet (Ce:YIG), etc.; the semiconductor gain material can be selected from gallium arsenide (GaAs), aluminum gallium arsenide (AlGaAs), indium gallium arsenide (InGaAs), etc.; the metal can be selected from gold, platinum, silver, etc.; the insulating medium can be selected from quartz, etc.

[0039] Solution 2, which can achieve the proposed isolation effect, uses organic magneto-optical materials such as (3-hexylthiophene-2,5-diyl) (stereoregular) and achieves the effect by doping with dichroic materials or unidirectionally arranged metal rods. The liquid organic magneto-optical material will form a film, which will achieve an optical rotation effect under the action of a magnetic field. The dichroic material or the unidirectionally arranged metal rods achieve an anisotropic gain-loss effect.

[0040] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

[0041] Many other changes and modifications may be made without departing from the concept and scope of the present invention.It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A fully polarized optical isolator, characterized in that: include: An optical fiber collimator (11), and a polarizing plate (12) and a composite magneto-optical crystal (13) arranged in sequence along a light path emitted from the optical fiber collimator (11), wherein a magnet (14) is arranged on a side surface of the composite magneto-optical crystal (13); The dielectric tensor ε of the composite magneto-optical crystal (13) satisfies: ε0 represents the dielectric constant, γ represents the gain or loss coefficient, Δ represents the loss, and u represents the magneto-optical parameter, where u=γ.

2. A fully polarized optical isolator according to claim 1, characterized in that: The magnets (14) are distributed on both sides of the composite magneto-optical crystal (13).

3. The fully polarized optical isolator according to claim 1, characterized in that: The incident light emitted by the optical fiber collimator (11) is rotated 45 degrees clockwise from vertical polarization through the polarizer (12), which is recorded as +45 degrees; then the incident light passes through the composite magneto-optical crystal (13) with a polarization direction of +45 degrees, and after passing through the composite magneto-optical crystal (13), the incident light is rotated 90 degrees counterclockwise, evolving into an eigenstate of the dielectric tensor of the composite magneto-optical crystal (13) material at -45 degrees.

4. The fully polarized optical isolator according to claim 1, characterized in that: After the reverse incident light is polarized, it will evolve into the eigenstate of the magneto-optical material at -45 degrees, which is orthogonal to the polarizer at +45 degrees, thus achieving an isolation effect.

5. The fully polarized optical isolator according to claim 1, characterized in that: The composite magneto-optical crystal (13) comprises: a sheet-shaped magneto-optical material layer (21), a semiconductor gain medium layer (22) and a loss medium layer.

6. A fully polarized optical isolator according to claim 5, characterized in that: The sheet-like magneto-optical material layer (21), the semiconductor gain medium layer (22) and the loss medium layer are cross-arranged and bonded together to form a composite magneto-optical crystal (13).

7. A fully polarized optical isolator according to claim 6, characterized in that: The lossy dielectric layer comprises: a metal strip (23) and an insulating medium (24), and the metal strip (23) and the insulating medium (24) are combined with each other to form the lossy dielectric layer.

8. The fully polarized optical isolator according to claim 6, characterized in that: The semiconductor gain medium layer (22) is made of gallium arsenide.

9. The fully polarized optical isolator according to claim 7, characterized in that: The insulating medium (24) is made of quartz.

10. The fully polarized optical isolator according to claim 7, characterized in that: The metal strip (23) is made of Au.

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