阅读说明：本技术 一种偏振相关反射型光隔离器 (Polarization-dependent reflective optical isolator ) 是由 陆众 张峰 陆海龙 韦琪 郜军红 龙跃金 于 2020-04-10 设计创作，主要内容包括：本发明公开了一种偏振相关反射型光隔离器,包括封装在金属壳内、从左至右沿所述金属壳体的中心轴线依次排开的以下部件：第一保偏双纤准直器、第一波片、第二波片、第一磁光晶体、第一渥拉斯顿棱镜、第一光束反射元件；所述第二波片与所述第一磁光晶体紧密贴合,所述第一磁光晶体与所述第一渥拉斯顿棱镜紧密贴合,所述第一波片与所述第一渥拉斯顿棱镜贴合,所述第一光束反射元件尽可能地与渥拉斯顿棱镜靠近。本发明通过设置第一保偏双纤准直器、第一波片、第二波片、第一磁光晶体、第一渥拉斯顿棱镜、第一光束反射元件,偏振相关反射型光隔离器具有结构简单、低损耗、体积小巧。(The invention discloses a polarization-dependent reflective optical isolator which comprises the following components, wherein the following components are packaged in a metal shell and are sequentially arranged along the central axis of the metal shell from left to right: the polarization maintaining optical fiber laser comprises a first polarization maintaining double-fiber collimator, a first wave plate, a second wave plate, a first magneto-optical crystal, a first Wollaston prism and a first light beam reflecting element; the second wave plate is tightly attached to the first magneto-optical crystal, the first magneto-optical crystal is tightly attached to the first Wollaston prism, the first wave plate is attached to the first Wollaston prism, and the first light beam reflection element is close to the Wollaston prism as far as possible. According to the polarization-dependent reflection type optical isolator, the first polarization-preserving dual-fiber collimator, the first wave plate, the second wave plate, the first magneto-optical crystal, the first Wollaston prism and the first light beam reflection element are arranged, so that the polarization-dependent reflection type optical isolator is simple in structure, low in loss and small in size.)

1. A polarization dependent reflective optical isolator comprising the following components enclosed in a metal housing, arranged in sequence from left to right along a central axis of said metal housing:

the polarization maintaining optical fiber laser comprises a first polarization maintaining double-fiber collimator, a first wave plate, a second wave plate, a first magneto-optical crystal, a first Wollaston prism and a first light beam reflecting element;

the second wave plate is closely attached to the first magneto-optical crystal, the first magneto-optical crystal is closely attached to the first Wollaston prism, the first wave plate is attached to the first Wollaston prism, the first light beam reflection element is close to the Wollaston prism as far as possible, the first wave plate is arranged on the left half portion of the reflection-type isolator, and the second wave plate and the first magneto-optical crystal are arranged on the right half portion of the reflection-type isolator.

2. The polarization dependent reflective optical isolator of claim 1, wherein said first polarization maintaining dual fiber collimator comprises a polarization maintaining dual fiber head and a Lens assembly, said Lens assembly being a C-Lens or a Grin-Lens; the grinding surface of the polarization-maintaining double-fiber head is an 8-degree surface, so that the return loss can be improved.

3. The polarization dependent reflective optical isolator of claim 2, wherein said polarization maintaining dual fiber contains two ports of the optical isolator, said ports being on the same side.

4. The polarization dependent reflective optical isolator of claim 1, wherein said first waveplate and said second waveplate are half waveplates, said first waveplate changing the angle of the incident polarized light by 45 ° and said second waveplate changing the angle of the incident polarized light by 90 °.

5. The polarization dependent reflective optical isolator of claim 4, wherein said first waveplate is a 22.5 ° half waveplate and said second waveplate is a 45 ° half waveplate.

6. The polarization dependent reflective optical isolator of claim 1, wherein said first magneto-optical crystal has an outer layer with a magnetic ring, said first magneto-optical crystal changing a polarization state of polarized light under an external magnetic field; the first magneto-optical crystal is a 45-degree Faraday polarimeter.

7. The polarization dependent reflective optical isolator of claim 1, wherein said first wollaston prism is formed by gluing two birefringent wedges having optical axes perpendicular to each other to separate the o and e light beams.

8. The polarization dependent reflective optical isolator of claim 1, wherein said first beam refractive element is a reflective prism or a two-piece mirror.

9. The polarization dependent reflective optical isolator of claim 8, wherein said first beam reflecting element is a reflecting prism having an antireflection coating on its incident surface and a reflecting coating on the other surface.

10. The polarization dependent reflective optical isolator of claim 9, wherein said first beam reflecting element is comprised of a roof prism having a range of angles: 30 to 90.

Technical Field

The invention relates to the technical field of photoelectricity, in particular to a polarization-dependent reflective optical isolator.

Background

Since the 80 s of the 20 th century, optical information technology has revolutionized the communication industry with its significant advantages of extremely wide frequency band, large information capacity, low transmission loss, etc. At present, optical fiber communication is developing towards a high-performance, large-capacity and flexible all-optical network, and key devices for realizing the all-optical network include an optical switch, an optical coupler, an optical isolator, tunable laser and the like. In the optical fiber device, the polarization-maintaining optical fiber device can transmit linearly polarized light, has stronger polarization maintaining capability, can improve the coherent signal-to-noise ratio of signals, and can be widely applied to the fields of aerospace, aviation, navigation, industrial manufacturing technology, communication and the like.

The polarization-dependent optical isolator is used as an important component of a polarization-maintaining optical fiber device, has the function of allowing light to pass through forward and reverse isolation, and simultaneously has strong polarization-maintaining capacity, so that the polarization-dependent optical isolator becomes a key device of various civil or military interference type sensors and coherent communication.

The structure of the optical isolator can be classified into a transmission type and a reflection type according to the transmission direction of the optical signal. The transmission type optical isolator is mature in process and relatively simple in assembly, but the volume of the optical circulator is larger due to the fact that light beams are transmitted in the same direction for a long time. The reflection-type optical isolator uses the reflection principle, can reduce the number of elements in the structure, has compact structure, and is an important direction for the miniaturization development of the optical isolator; but also has the problems of large volume, small isolation, low extinction ratio, high cost and the like.

The prior art is therefore still subject to further development.

Disclosure of Invention

In view of the above technical problems, embodiments of the present invention provide a polarization dependent reflective optical isolator, which can solve the related technical problems in the prior art.

The embodiment of the invention provides a polarization-dependent reflective optical isolator which is characterized by comprising the following components, wherein the following components are packaged in a metal shell and are sequentially arranged along the central axis of the metal shell from left to right:

the polarization maintaining optical fiber laser comprises a first polarization maintaining double-fiber collimator, a first wave plate, a second wave plate, a first magneto-optical crystal, a first Wollaston prism and a first light beam reflecting element;

the second wave plate is closely attached to the first magneto-optical crystal, the first magneto-optical crystal is closely attached to the first Wollaston prism, the first wave plate is attached to the first Wollaston prism, the first light beam reflection element is close to the Wollaston prism as far as possible, the first wave plate is arranged on the left half portion of the reflection-type isolator, and the second wave plate and the first magneto-optical crystal are arranged on the right half portion of the reflection-type isolator.

Optionally, the first polarization-maintaining twin-fiber collimator includes a polarization-maintaining twin-fiber head and a Lens assembly, and the Lens assembly is a C-Lens or a Grin-Lens; the grinding surface of the polarization-maintaining double-fiber head is an 8-degree surface, so that the return loss can be improved.

Optionally, the polarization maintaining double-fiber comprises two ports of the optical isolator, and the two ports are on the same side.

Optionally, the first wave plate and the second wave plate are half-wave plates, the first wave plate may change the angle of the incident polarized light by 45 °, and the second wave plate may change the angle of the incident polarized light by 90 °.

Optionally, the first wave plate is a 22.5 ° half wave plate, and the second wave plate is a 45 ° half wave plate.

Optionally, an outer layer of the first magneto-optical crystal may be provided with a magnetic ring, and the first magneto-optical crystal changes a polarization state of polarized light under the action of an external magnetic field; the first magneto-optical crystal is a 45-degree Faraday polarimeter.

Optionally, the first wollaston prism is formed by gluing two birefringent wedges with optical axes perpendicular to each other, and can separate o light from e light.

Optionally, the first beam refracting element is a reflecting prism or a two-piece mirror.

Optionally, the first light beam reflecting element is a reflecting prism, an antireflection film is coated on an incident surface of the reflecting prism, and a reflecting film is coated on the other surface of the reflecting prism.

Optionally, the first light beam reflecting element is composed of a roof prism, and the angle range of the roof prism is: 30 to 90.

According to the polarization-dependent reflective optical isolator, the first polarization-dependent dual-fiber collimator, the first wave plate, the second wave plate, the first magneto-optical crystal, the first Wollaston prism and the first light beam reflecting element are arranged, so that the polarization-dependent reflective optical isolator is simple in structure, low in loss and small in size;

high isolation, high extinction ratio, same side of port and low cost.

Drawings

In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below.

FIG. 1 is an exploded view of one embodiment of an optical isolator according to the present invention;

FIG. 2 is a side view of the optical isolator of the present invention;

FIG. 3 is a top view of the forward path of an optical isolator according to the present invention;

FIG. 4 is a top view of the reverse path of an optical isolator according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The following detailed description of embodiments of the invention refers to the accompanying drawings.

FIG. 1 is an exploded view of an embodiment of an optical isolator according to the present invention. Referring to fig. 1, the optical isolator is enclosed in a metal shell, and the optical isolator is sequentially disposed along a central axis from left to right, and sequentially comprises a first polarization maintaining dual-fiber collimator 11, a first wave plate 21, a second wave plate 31, a first magneto-optical crystal 41, a first wollaston prism 51, and a first beam reflecting element 61.

The second wave plate 31 is closely attached to the first magneto-optical crystal 41, the first magneto-optical crystal 41 is closely attached to the first wollaston prism 51, and the first wave plate 21 is also attached to the first wollaston prism 51. Meanwhile, the first beam reflecting element 61 is also as close as possible to the first wollaston prism 51, so that the optical isolator is compact in structure and small in size. Since the number of components is small, the optical isolator has the advantages of high isolation, low loss and low cost.

Further, the first polarization-maintaining twin-fiber collimator 11 comprises a polarization-maintaining twin-fiber head and a C-Lens. Two ports 01 and 02 of the optical isolator are contained in the polarization-maintaining double fiber head, and the two ports 01 and 02 are positioned on the same side (the left side in the figure 1) of the polarization-maintaining double fiber head, so that the volume of the reflection-type optical isolator can be optimized.

Specifically, the polarization maintaining double-fiber head 11 is composed of two polarization maintaining optical fibers and a double-cone micro-tube. The two polarization maintaining fibers are panda polarization maintaining fibers, and the polarization direction of the two polarization maintaining fibers plays a key role in the yield of the whole device in the axial operation. In the invention, the two optical fiber heads are both in fast axis cut-off and slow axis work. The direction of the slow axis is defined as the Z-axis direction, and the direction of the fast axis is defined as the X-axis direction. The slow axis directions of the two optical fiber heads are parallel and parallel, the slow axis direction of the optical fiber heads is accurately placed, and the extinction ratio of the optical isolator can be improved.

It is understood that the first wave plate 21 and the second wave plate 31 are half-wave plates, but the optical axis directions of the two wave plates are different. In one embodiment:

the first wave plate 21 is a half-wave plate with the optical axis and the X axis of the wave plate forming 45 degrees, and can change the polarization state of the normal incident light, so that the polarization state of the light is changed by 90 degrees;

the second wave plate 31 is a half-wave plate whose optical axis and X axis are 22.5 °, and if light is incident from left to right, the polarization state of the light changes by 45 ° clockwise, and if light is incident from right to left, the polarization state of the light changes by 45 ° counterclockwise.

The first magneto-optical crystal 41 is a faraday optical rotation plate and can be matched with a magnetic ring, and the magnetic ring is arranged on the outer layer of the first magneto-optical crystal 41 in the reflection-type optical isolator. Under the action of an external magnetic field, the polarization state of normally incident light can be changed, so that the polarization state of the light is changed by 45 degrees clockwise.

From left to right in fig. 1, toward the plane X0Z, the first wave plate 21 is in the left half of the reflective optical isolator, and the second wave plate 31 and the first magneto-optical crystal 41 are in the right half of the reflective isolator. All parts of the optical isolator are tightly attached or matched, the position of all the parts after being positioned is fixed, and the effect is achieved on the premise of keeping the size to be small.

The first wollaston prism 51 is a birefringent polarizing device made of natural calcite crystals, the rhombohedral crystals of which the main component is CaCO 3. An incident linearly polarized light beam is divided into 2 linearly polarized light beams with mutually vertical polarization directions. The separation angle of the two beams is substantially symmetrical with respect to the optical axis. The prevailing separation angles are 5 °, 10 °, 5 ° and 20 °, respectively.

In this embodiment, the first wollaston prism 51 is formed by gluing two uniaxial birefringent crystal wedge angle pieces with mutually matched angles, the optical axes of the two wedge angle pieces are mutually orthogonal, and the optical axes are both perpendicular to the incident light direction. If the normal incident light is natural light, the light can be refracted to form o light and e light, the o light and the e light are greatly separated at the gluing interface, the o light is deflected upwards, and the e light is deflected downwards, so that the first wollaston prism 51 can play a role in deflecting and displacing the light beam, and is equivalent to a polarization beam splitter.

The first light beam reflecting element 61 is composed of a ridge prism with a proper angle, the selected angle of the ridge prism is 90 degrees, an antireflection film needs to be plated on an incident surface, and reflecting films need to be plated on other surfaces, so that the light path is mainly deflected, namely, the transmission direction of the light beam is reversely changed, the light beam can be reflected and transmitted, the components are reduced to the greatest extent, and the optical isolator is small in size and simple in structure. Of course in other embodiments the prism angle may be selected according to the optical path, ranging from 30 ° to 90 °.

Fig. 2 is a side view of the optical path of the optical isolator of the present invention, and fig. 3 is a top view of the forward optical path of the optical isolator of the present invention, i.e., a top view of the optical paths from fiber port 01 to fiber port 02 of the reflective optical isolator. Referring to fig. 2 and 3, a linearly polarized light 010 is input from the optical fiber port 01, the slow axis and the Z axis of the first polarization maintaining dual-fiber collimator 1 (panda polarization maintaining fiber head) are placed in parallel, and the linearly polarized light is output from the C-Lens (or Grin-Lens) of the first polarization maintaining dual-fiber collimator 11, the polarization state of the linearly polarized light is parallel along the Z axis direction, and the light beam mark is 011.

When the light beam 011 passes through the first wave plate 21, the first wave plate 21 can change the polarization state of the normally incident polarized light by 90 °, that is, the orthogonal deflection occurs, the vibration direction of the linearly polarized light is parallel to the X-axis direction, and the light beam mark is 012. The light beam continues to travel and the polarization state does not change because the second wave plate 31 and the first magneto-optical crystal 41 are not in the direction of travel of the light beam. When passing through the first wollaston prism 51, the polarized light will be deflected upward at the bonding interface of the two wedges, but the polarization state of the light beam is not changed, i.e. the polarization direction is parallel to the X axis, and the light beam is marked 013. And then passes through the first light beam reflection element 61, the displacement of the light beam can be deflected and changed, the light beam is transmitted reversely, the polarization direction is not changed, namely, the vibration direction is parallel to the X axis, and the light beam marks 021. When the light beam is reflected back, the light beam passes through the first Wollaston prism 51 again, the light path is deflected downwards, the polarization state is still unchanged, and the light beam mark is 022. 022 the light beam passes through a first magneto-optical crystal 41, and the first magneto-optical crystal 41 may change the polarization state of the polarized light beam by 45 ° counterclockwise, where the light beam is denoted by 023. The light beam 023 then passes through the second wave plate 31, and since the polarization state of the incident light from right to left is changed 45 ° counterclockwise by the second wave plate 31, the light beam is designated 024, and the polarization state of the light beam 024 is orthogonally deflected with respect to the polarization state of the light beam 022.

The light beam 022 continues to travel because the first wave plate 21 is not in the reflected light path and thus the polarization state of the light beam is not changed, i.e., the direction of vibration is parallel to the Z-axis, labeled as light beam 025. Finally, because the polarization state of the light beam 025 is consistent with the slow axis of the polarization-maintaining dual-fiber head port 020 of the first polarization-maintaining dual-fiber collimator 11, and the position of the linearly polarized light beam is consistent with the position of the port 020, the linearly polarized light beam can be output through the port 020 of the first polarization-maintaining dual-fiber collimator 11, so that the polarized light beam of the device is positively transmitted to the port 020 from the port 010. Two polarization maintaining optical fibers in the polarization maintaining optical fiber head work in a fast axis stop mode and a slow axis mode, namely the directions of working axes are consistent, the polarization maintaining optical fiber head is easy to assemble, and high extinction ratio and low insertion loss of the optical isolator can be achieved.

Fig. 3 is a top view of the reverse optical path of the optical isolator of the present invention, i.e., the optical path from fiber port 02 to fiber port 01 of the optical isolator.

Referring to fig. 3 and 4, linearly polarized light 120 is input from the optical fiber port 02 and output from the C-Lens of the first polarization-preserving dual-fiber collimator 11, the polarization state of the linearly polarized light is parallel to the Z-axis direction, and the light beam is marked as 121. Since the first wave plate 21 is not in the optical path, the light beam keeps the original polarization state and advances along the original optical path. When passing through the second wave plate 31, the polarization state of the incident light from left to right is changed by 45 ° clockwise by the second wave plate 31, and the light beam is denoted by 122. Since the first magneto-optical crystal 41 can change the polarization state of the polarized light beam by 45 ° counterclockwise, the light beam 122 passes through the first magneto-optical crystal 41, the polarization state of the light beam is deflected by 45 ° counterclockwise, and the light beam is denoted by 123. Thus, the polarization state of beam 123 is the same as the polarization state of beam 121, i.e., the polarization state is parallel to the Z-axis direction. When the light beam 123 passes through the first wollaston prism 51, the light path direction is deflected downward at the bonding interface of the two wedges, the vibration direction is not changed, and the light beam mark is 124.

First beam reflecting element 61 then deflects beam 124 only to change the path, transmitting the beam in the reverse direction, with no change in polarization, and beam designated 131. When the light beam is reflected back, the light beam passes through the first wollaston prism 51 again, and the light beam is deflected upwards, the polarization state is still unchanged, and the light beam is marked as 132. Since the first magneto-optical crystal 41 and the second wave plate 31 are not in the reflected light path, the polarization state of the light beam is not changed, i.e. the vibration direction is still parallel to the Z-axis. Finally, since the first waveplate can change the polarization state of the normally incident polarized light by 90 °, the vibration direction of the light beam is orthogonally deflected, i.e., the polarization state of the light beam is parallel to the X-axis, denoted by 133. The polarization state of the light beam 133 is just vertical to the slow axis vibration direction of the polarization maintaining fiber of the port 01, and the position of the light path is not at the position of the port 01, so that the function of preventing light from passing in the reverse direction of the device is realized. Meanwhile, when the light is reversely transmitted from the port 02 to the port 01, on a reverse reflection light path, due to the deflection effect of the light path of the first Wollaston prism 51, part of the light overflows the light path, the whole light path has a good isolation effect, and the isolation degree of the reflection-type optical isolator is improved.

In summary, the reflective light isolator is provided with the first polarization maintaining dual-fiber collimator 11, the first wave plate 21, the second wave plate 31, the first magneto-optical crystal 41, the first wollaston prism 51, and the first light beam reflecting element 61, so that the reflective light isolator has a compact structure and a small volume. Since the number of components is small, the optical isolator has the advantages of high isolation, low loss and low cost.

The slow axis directions of the two optical fiber heads in the first polarization maintaining double-fiber collimator 11 are parallel and parallel, the slow axis direction of the optical fiber heads is accurately placed, and the extinction ratio of the reflection-type optical isolator can be improved. Two polarization maintaining optical fibers in the polarization maintaining optical fiber head work in a fast axis stop mode and a slow axis mode, namely the directions of working axes are consistent, the polarization maintaining optical fiber head is easy to assemble, and high extinction ratio and low insertion loss of the optical isolator can be achieved.

On the reverse reflection light path, due to the light path deflection effect of the first wollaston prism 51, part of light overflows the light path, the whole light path has a good isolation effect, and the isolation degree of the reflection-type optical isolator is improved.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.