Optical isolator and optical path system thereof

Abstract

The present invention discloses an optical isolator and its optical path system, comprising: a first uniaxial crystal, a second uniaxial crystal, and a third uniaxial crystal connected in sequence; wherein a Faraday rotator and a magnetic ring are respectively arranged between the first uniaxial crystal and the second uniaxial crystal and between the second uniaxial crystal and the third uniaxial crystal, and the magnetic ring provides an environmental magnetic field for the Faraday rotator; the second uniaxial crystal is provided with a plurality of half-wave plates, and the half-wave plates, the Faraday rotator and the third uniaxial crystal are used to combine the o light and the e light to realize the forward transmission of the optical signal with low loss; an absorption film is arranged on one side of the second uniaxial crystal, and the absorption film absorbs the reversely transmitted and deflected e light signal to realize the isolation effect. The optical isolator of the present invention has the characteristics of simple optical path structure and low loss and high isolation.

Description

Technical Field

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

[0002] The magneto-optical effect is a physical phenomenon with great application value, and has good application prospects in magneto-optical modulators, magneto-optical isolators, etc. The application of magneto-optical isolators is mainly based on its magneto-optical rotation phenomenon, which originates from the Zeeman effect. When polarized light passes through a medium in a magnetic field along the direction of magnetic field lines, it will rotate, resulting in magnetic circular dichroism and Faraday effect. Moreover, when polarized light rotates under the action of the Faraday effect, it has nothing to do with the transmission direction of light. Another situation where polarized light will rotate is the wave plate. When polarized light passes through a half-wave plate, when its vibration direction has an angle with the fast axis or slow axis of the crystal material of the wave plate, the polarized light will rotate twice the angle based on the fast axis or slow axis, and this rotation angle is related to the transmission direction of the optical signal, that is, after the transmission direction from left to right changes to from right to left, the half-wave plate's rotation angle of polarized light remains unchanged, but the direction is opposite.

[0003] With the rapid development of optical fiber communication and the application of other optical fiber technologies, more and more optical passive components are required, and higher and higher requirements are placed on the performance of the components. Optical isolators are one of the important optical passive components, which require that the optical signal is transmitted in one direction, that is, the optical signal can play a good isolation role when it is transmitted in the reverse direction, and the optical signal transmitted in the forward direction has a low loss when passing through the optical isolator. Researchers and related companies have been committed to researching and producing optical isolators with lower loss and higher isolation, especially isolators with high isolation.

[0004] At present, in the prior art, optical isolators use a method of cascading two isolator cores to improve isolation. Optical isolators are all composed of wedge-shaped pieces, Faraday rotators, and magnetic rings made of uniaxial crystal materials. Two optical isolators are cascaded. As a result of the cascade, the isolation is improved to a certain extent, but the insertion loss is reduced a lot, resulting in a relatively large loss when the optical signal passes in the forward direction. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes an optical isolator and an optical path system thereof to solve the above problems existing in the prior art.

[0006] To achieve the above object, the present invention provides an optical isolator, comprising:

[0007] A first uniaxial crystal, a second uniaxial crystal, and a third uniaxial crystal connected in sequence, wherein the first uniaxial crystal, the second uniaxial crystal, and the third uniaxial crystal are all cuboids;

[0008] A Faraday rotator and a magnetic ring are respectively arranged between the first uniaxial crystal and the second uniaxial crystal and between the second uniaxial crystal and the third uniaxial crystal, and the magnetic ring provides an environmental magnetic field for the Faraday rotator;

[0009] The second uniaxial crystal is provided with a plurality of half-wave plates, and the o-light and the e-light are combined by the half-wave plates, the Faraday rotator and the third uniaxial crystal to realize the forward transmission of the optical signal with low loss;

[0010] An absorption film is disposed on one side of the second uniaxial crystal, and the absorption film absorbs the reversely transmitted and deflected e-light signal to achieve isolation.

[0011] Preferably, the refractive index of the second uniaxial crystal is greater than that of the first uniaxial crystal and the third uniaxial crystal.

[0012] Preferably, the opposite surfaces of the cuboid are polished to a fixed smoothness to achieve incident and emitted light signals.

[0013] Preferably, the number of the half-wave plates is four, and the half-wave plates are respectively photo-bonded to the opposite surfaces of the second uniaxial crystal, and then the other side of the half-wave plate on the opposite surface is processed and polished to meet the size requirements.

[0014] Preferably, the number of the Faraday rotator plates and the number of the magnetic rings are two respectively, the cut Faraday rotator plates are placed on the magnetic rings, one of the magnetic rings is fixed to a polished surface of the first uniaxial crystal with optical glue, and the other magnetic ring is fixed to a polished surface of the third uniaxial crystal with optical glue.

[0015] In order to achieve the above technical objectives, the present invention also provides an optical path system of an optical isolator. Based on the optical isolator, the optical path system includes:

[0016] The forward transmission subsystem is used to decompose the optical signal into e-light and o-light through the first uniaxial crystal, wherein the e-light is sequentially emitted through the first Faraday rotator and the first group of half-wave plates and vertically incident on the second uniaxial crystal and the third uniaxial crystal to obtain the e-light deflected upward; wherein the o-light is sequentially emitted through the second group of half-wave plates and the second Faraday rotator and vertically incident on the third uniaxial crystal; the o-light and the e-light of the third uniaxial crystal are combined and emitted vertically from the surface of the third uniaxial crystal to realize the forward conduction of the optical isolator.

[0017] The reverse transmission subsystem is used to vertically emit the e-light decomposed by the third uniaxial crystal and incident on the second Faraday rotator, and then vertically incident on the incident surface of the second uniaxial crystal through the second set of half-wave plates. The e-light is deflected downward based on the refractive index of the second uniaxial crystal and transmitted to the opposite side of the incident surface of the second uniaxial crystal, and finally absorbed by the absorption film on the opposite side.

[0018] Preferably, the first Faraday rotator is located between the first uniaxial crystal and the second uniaxial crystal, and the second Faraday rotator is located between the second uniaxial crystal and the third uniaxial crystal.

[0019] Preferably, the first group of half-wave plates is located on one side of the second uniaxial crystal, and the second group of half-wave plates is located on the opposite side of the second uniaxial crystal.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] The present invention provides an optical isolator and an optical path system thereof, which realizes the separation and beam combination of o-light and e-light through a rectangular uniaxial crystal, greatly improves the optical processing accuracy of the uniaxial crystal, and greatly reduces the processing difficulty of the uniaxial crystal; the present invention adopts an ingenious combination of a half-wave plate and a Faraday rotator plate to realize the conversion of o-light and e-light inside the optical isolator, so that the optical signal passes through with low loss in the forward direction, and the optical signal transmitted in the reverse direction can be absorbed by the absorption film through ingenious conversion, thereby realizing a very high isolation degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0023] Figure 1 is a light path system diagram of an optical isolator according to an embodiment of the present invention;

[0024] Figure 2 FIG. 4 is a schematic diagram of a second uniaxial crystal according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0027] Embodiment 1

[0028] like Figure 1 As shown, in this embodiment, an optical isolator is provided, comprising:

[0029] A first uniaxial crystal, a second uniaxial crystal, and a third uniaxial crystal connected in sequence, wherein the first uniaxial crystal, the second uniaxial crystal, and the third uniaxial crystal are all cuboids;

[0030] A Faraday rotator and a magnetic ring are respectively arranged between the first uniaxial crystal and the second uniaxial crystal and between the second uniaxial crystal and the third uniaxial crystal, and the magnetic ring provides an environmental magnetic field for the Faraday rotator;

[0031] The second uniaxial crystal is provided with a plurality of half-wave plates, and the o-light and the e-light are combined by the half-wave plates, the Faraday rotator and the third uniaxial crystal to realize the forward transmission of the optical signal with low loss;

[0032] An absorption film is disposed on one side of the second uniaxial crystal, and the absorption film absorbs the reversely transmitted and deflected e-light signal to achieve isolation.

[0033] Specifically, the optical path system of the optical isolator is as follows: Figure 1 As shown, the optical system consists of three birefringent uniaxial crystals, four half-wave plates (referred to as half-wave plates) made of the same material, two Faraday rotators and two magnetic rings for generating an environmental magnetic field for the Faraday rotators.

[0034] In this embodiment, the lower one-third of the surface of the second uniaxial crystal facing the forward transmission light signal is coated with an absorption film, such as Figure 2 In the black area shown, the second uniaxial crystal has a larger refractive index difference between o-light and e-light than the first and third uniaxial crystals, and its thickness is also larger, so that the reversely transmitted e-light will not overlap with the forwardly transmitted optical signal area after being refracted downward by the uniaxial crystal, and can be transmitted to the area coated with the absorption film, so that the reversely transmitted optical signal can be completely isolated, achieving a very high isolation. The optical isolator has the important parameters of high isolation and low insertion loss.

[0035] Furthermore, the light refractive index of the second uniaxial crystal is greater than that of the first uniaxial crystal and the third uniaxial crystal.

[0036] Specifically, the first uniaxial crystal and the third uniaxial crystal are made of the same material and have the same thickness, the second uniaxial crystal is a high birefringence crystal, and the refractive index difference between o-light and e-light in the second uniaxial crystal is much larger than that of the first uniaxial crystal and the third uniaxial crystal, so that when o-light and e-light are incident on the second uniaxial crystal in reverse, the e-light has a larger deflection angle.

[0037] Furthermore, the opposite surfaces of the cuboid are polished to a fixed smoothness to achieve incident and emitted light signals.

[0038] Specifically, two opposite faces of the first uniaxial crystal, the second uniaxial crystal, and the third uniaxial crystal of the cuboid are polished to a finish of 20 / 10 or 10 / 5. The first face and the second face of the second uniaxial crystal are the light incident and light exiting surfaces, such as Figure 2 shown.

[0039] Furthermore, the number of the half-wave plates is four, and the half-wave plates are respectively photo-bonded to the opposite surfaces of the second uniaxial crystal, and then the other side of the half-wave plate on the opposite surface is processed and polished to meet the size requirements.

[0040] Specifically, the thickness of the half-wave plate is very thin, and the two surfaces are polished to a finish of 20 / 10 or 10 / 5. One surface is polished first, and then photo-bonded to the polished surface of the uniaxial crystal, and then the other surface of the polished wave plate is processed.

[0041] Furthermore, the number of the Faraday rotator and the number of the magnetic ring are two respectively, the cut Faraday rotator is placed on the magnetic ring, one of the magnetic rings is fixed to a polished surface of the first uniaxial crystal with optical glue, and the other magnetic ring is fixed to a polished surface of the third uniaxial crystal with optical glue.

[0042] In this embodiment, the manufacturing process of the optical isolator is as follows: the polished surfaces of the first uniaxial crystal, the second uniaxial crystal, the third uniaxial crystal, and the polished surface of the half-wave plate are wiped clean with anhydrous ethanol and set aside for use; Figure 1 As shown, two wave plates are optically bonded to one surface of the second uniaxial crystal (such as Figure 2 As shown), the other two sheets of optical glue are attached to the two surfaces of the second uniaxial crystal (as shown Figure 2 Then, the other side of the wave plate on the 1st and 2nd surfaces is processed and polished to a finish of 20 / 10 or 10 / 5 and meets the size requirements; the cut Faraday rotator is placed on the magnetic ring, as shown in FIG. Figure 1 As shown, one of the magnetic rings is fixed to a polished surface of the first uniaxial crystal with optical glue, and the other magnetic ring is fixed to a polished surface of the third uniaxial crystal with optical glue; finally, according to Figure 1 The position relationship shown is to encapsulate them in a sleeve, and connect the left and right ends to the optical fiber collimator.

[0043] Embodiment 2

[0044] This embodiment provides an optical path system of an optical isolator. Based on the optical isolator described in Embodiment 1, the optical path system includes:

[0045] The forward transmission subsystem is used to decompose the optical signal into e-light and o-light through the first uniaxial crystal, wherein the e-light is sequentially emitted through the first Faraday rotator and the first group of half-wave plates and vertically incident on the second uniaxial crystal and the third uniaxial crystal to obtain the e-light deflected upward; wherein the o-light is sequentially emitted through the second group of half-wave plates and the second Faraday rotator and vertically incident on the third uniaxial crystal; the o-light and the e-light of the third uniaxial crystal are combined and emitted vertically from the surface of the third uniaxial crystal to realize the forward conduction of the optical isolator.

[0046] The reverse transmission subsystem is used to vertically emit the e-light decomposed by the third uniaxial crystal and incident on the second Faraday rotator, and then vertically incident on the incident surface of the second uniaxial crystal through the second set of half-wave plates. The e-light is deflected downward based on the refractive index of the second uniaxial crystal and transmitted to the opposite side of the incident surface of the second uniaxial crystal, and finally absorbed by the absorption film on the opposite side.

[0047] Furthermore, the first Faraday rotator is located between the first uniaxial crystal and the second uniaxial crystal, and the second Faraday rotator is located between the second uniaxial crystal and the third uniaxial crystal.

[0048] Furthermore, the first group of half-wave plates is located on one side of the second uniaxial crystal, and the second group of half-wave plates is located on the opposite side of the second uniaxial crystal.

[0049] Specifically, Figure 1 As shown, forward transmission is from left to right, specifically including: the optical signal is vertically incident on the first uniaxial crystal and is decomposed into e-light vibrating on the paper surface and o-light vibrating perpendicular to the paper surface, the o-light maintains the incident direction and continues to transmit forward until it is vertically emitted from the crystal surface, the emitted o-light is rotated 45° clockwise / counterclockwise by a Faraday rotation plate, and then rotated 45° counterclockwise / clockwise by a half-wave plate, and then vertically incident on the second uniaxial crystal as an o-light and then vertically emitted, the emitted o-light is rotated 45° clockwise / counterclockwise by a half-wave plate, and then rotated 45° clockwise / counterclockwise by a Faraday rotation plate, and vertically incident on the third uniaxial crystal as an o-light, and then emitted as an e-light and incident on the third uniaxial crystal, and then deflected upward according to the refractive index of the e-light of the third uniaxial crystal. Finally, the vertically incident o-light and the e-light deflected upward in the third uniaxial crystal at point 2 are combined and emitted vertically from the surface of the third uniaxial crystal, ultimately achieving forward conduction of the optical isolator, and the optical signal passes with extremely low loss.

[0050] Figure 1From right to left is reverse transmission, specifically including: the optical signal is vertically incident on the third uniaxial crystal and is decomposed into e-light vibrating on the paper surface and o-light vibrating perpendicular to the paper surface, the o-light maintains the incident direction unchanged and is transmitted forward, the vertically emitted o-light passes through the Faraday rotation plate and is rotated 45° clockwise / counterclockwise, and then passes through the half-wave plate and is rotated 45° clockwise / counterclockwise, and then is emitted as e-light perpendicular to the half-wave plate and vertically incident on the surface of the second uniaxial crystal, and then is deflected downward and transmitted to the surface opposite to the incident surface of the second uniaxial crystal, and is absorbed by the absorption film plated at this position.

[0051] During reverse transmission, the e-light decomposed by the third uniaxial crystal is deflected downward according to the refractive index of the e-light of the third uniaxial crystal, then emitted vertically and incident on the Faraday rotation plate, rotated 45° clockwise / counterclockwise and then incident vertically on the surface of the wave plate. The half wave plate rotates it 45° counterclockwise / clockwise, and then it is still incident vertically on the surface of the second uniaxial crystal as e-light, and then deflected downward according to the refractive index of the e-light of the second uniaxial crystal and transmitted to the opposite surface of the incident surface of the second uniaxial crystal, and is also absorbed by the absorption film plated at this position.

[0052] Beneficial effects of this embodiment:

[0053] This embodiment uses a rectangular uniaxial crystal to achieve the separation and combination of o-light and e-light, which greatly improves the optical processing accuracy of the uniaxial crystal and greatly reduces the processing difficulty of the uniaxial crystal; this embodiment uses a clever combination of a half-wave plate and a Faraday rotator to achieve the conversion of o-light and e-light inside the optical isolator, so that the optical signal passes through with low loss in the forward direction, and the optical signal transmitted in the reverse direction can be absorbed by the absorption film through clever conversion, thereby achieving a high degree of isolation;

[0054] In addition, in addition to using a combination of a wave plate and a Faraday rotator to achieve the conversion of o-light and e-light, this embodiment mainly adds a rectangular uniaxial crystal in the middle to guide the reversely transmitted light beam to the area outside the forward transmission signal path and then process it. The middle uniaxial crystal uses a material with a relatively large difference in refractive index between o-light and e-light. On the one hand, the beam diameter of the forward light signal is relatively small after the uniaxial crystal that separates o-light and e-light is separated. On the other hand, the e-light signal that is reversely transmitted and incident on the middle uniaxial crystal has a relatively large deflection angle, ensuring that the deflected e-light beam will not overlap with the small-diameter beam of forward transmission. At the same time, an absorption film is plated on the non-overlapping surface area of ​​the middle uniaxial crystal, so that the absorption film can completely absorb the reversely transmitted light signal, thereby achieving a very high isolation degree.

[0055] In this embodiment, a rectangular uniaxial crystal is used, which is convenient for processing. Figure 1It can also be seen from the figure that in the forward transmission, the o-light and the e-light are combined together, while the o-light and the e-light of the current wedge-shaped optical isolator are output in parallel, and the combined output of this embodiment has a better effect on reducing insertion loss. Therefore, this embodiment uses a half-wave plate and a Faraday rotator to cleverly transform the o-light and the e-light and uses three rectangular uniaxial crystals to achieve reverse optical isolation, which has the characteristics of simple optical path structure, low loss and high isolation.

[0056] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An optical isolator, characterized in that: include: A first uniaxial crystal, a second uniaxial crystal, and a third uniaxial crystal connected in sequence, wherein the first uniaxial crystal, the second uniaxial crystal, and the third uniaxial crystal are all cuboids; A Faraday rotator and a magnetic ring are respectively arranged between the first uniaxial crystal and the second uniaxial crystal and between the second uniaxial crystal and the third uniaxial crystal, and the magnetic ring provides an environmental magnetic field for the Faraday rotator; The second uniaxial crystal is provided with a plurality of half-wave plates, and the o-light and the e-light are combined by the half-wave plates, the Faraday rotator and the third uniaxial crystal to realize the forward transmission of the optical signal with low loss; The second uniaxial crystal guides the reversely transmitted light beam to the outside of the area of ​​the forwardly transmitted signal path and then processes it. The material with a relatively large difference in refractive index between the o-light and the e-light is used. On the one hand, the diameter of the forward light signal is relatively small after the uniaxial crystal that separates the o-light and the e-light is separated. On the other hand, the e-light signal that is transmitted in the reverse direction and incident on the second uniaxial crystal has a larger deflection angle, ensuring that the deflected e-light light beam does not overlap with the small-diameter light beam of the forward transmission. An absorption film is disposed on one side of the second uniaxial crystal, and the absorption film absorbs the reversely transmitted and deflected e-light signal to achieve isolation.

2. The optical isolator according to claim 1, characterized in that: The light refractive index of the second uniaxial crystal is greater than that of the first uniaxial crystal and the third uniaxial crystal.

3. The optical isolator according to claim 1, characterized in that: The opposite surfaces of the cuboid are polished to a fixed finish to achieve incident and emitted light signals.

4. The optical isolator according to claim 1, characterized in that: There are four half-wave plates, which are optically bonded to the opposite surfaces of the second uniaxial crystal, and then the other side of the half-wave plate on the opposite surface is processed and polished to meet the size requirements.

5. The optical isolator according to claim 1, wherein: There are two Faraday rotators and two magnetic rings respectively. The cut Faraday rotators are placed on the magnetic rings, one of the magnetic rings is fixed to a polished surface of the first uniaxial crystal with optical glue, and the other magnetic ring is fixed to a polished surface of the third uniaxial crystal with optical glue.

6. An optical path system of an optical isolator, characterized in that: Based on the optical isolator according to any one of claims 1 to 5, the optical path system comprises: A forward transmission subsystem is used to decompose the optical signal into e-light and o-light through the first uniaxial crystal, wherein the e-light sequentially passes through the first Faraday rotator and the first group of half-wave plates and is vertically incident on the second uniaxial crystal and the third uniaxial crystal to obtain the e-light deflected upward; wherein the o-light sequentially passes through the second group of half-wave plates and the second Faraday rotator and is vertically incident on the third uniaxial crystal; the o-light and the e-light of the third uniaxial crystal are combined and emitted vertically from the surface of the third uniaxial crystal to realize the forward conduction of the optical isolator; The reverse transmission subsystem is used for the e-light and o-light decomposed by the third uniaxial crystal, wherein the o-light keeps the incident direction unchanged and transmits forward, and the vertically emitted o-light passes through the second Faraday rotator and the second group of half-wave plates and is vertically incident on the incident surface of the second uniaxial crystal; the e-light is vertically emitted and incident on the second Faraday rotator, and passes through the second group of half-wave plates and is vertically incident on the incident surface of the second uniaxial crystal; then the o-light is emitted perpendicularly to the half-wave plate in the posture of the e-light and is vertically incident on the incident surface of the second uniaxial crystal, the o-light and the e-light are combined together, the refractive index is deflected downward and transmitted to the opposite side of the incident surface of the second uniaxial crystal, and finally absorbed by the absorption film on the opposite side.

7. The optical path system according to claim 6, characterized in that: The first Faraday rotator is located between the first uniaxial crystal and the second uniaxial crystal, and the second Faraday rotator is located between the second uniaxial crystal and the third uniaxial crystal.

8. The optical path system according to claim 6, characterized in that: The first group of half-wave plates is located on one side of the second uniaxial crystal, and the second group of half-wave plates is located on the opposite side of the second uniaxial crystal.

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