CN104765166B - It is a kind of to cascade powerful optoisolator for optical fiber laser - Google Patents

Abstract

The invention discloses a cascadable high-power optical isolator for fiber lasers. The optical isolator includes an optical adjustment component (1), a magnet component (2), an inner fastening component (3), and a base (4) and end cover (5); the base (4) is equipped with light adjustment assembly (1), magnet assembly (2), inner fastening assembly (3), and end cover (5) is installed on the base (4) ); the magnet assembly (2) is installed in the sleeve (32) of the inner fastening assembly (3), and the magneto-active crystal (18) of the light adjustment assembly (1) is arranged at the center of the magnet assembly (2) , the compensation crystal (17) is installed on the fixing seat (34) of the inner fastening component (3). The optical isolator of the present invention adopts a cascadable structure of composite magnetic field, external crystal compensation, and built-in magneto-optical crystal, which realizes the structural design of high power, long life, and miniaturization, so that the optical isolator of the present invention has depolarization low, high isolation performance.

Description

A cascadable high-power optical isolator for fiber lasers

technical field

The invention relates to an optical isolator, more particularly, to a cascadable high-power optical isolator for fiber lasers.

Background technique

An optical isolator is an optical passive device that only allows one-way light to pass through. Its working principle is based on the non-reciprocity of the Faraday effect, which rotates the polarization states of forward incident light and reverse incident light to the same direction by the same angle. , can effectively prevent the backward transmission light in the optical path due to various reasons from causing various adverse effects on the light source and the optical path system, and improve the stability of the overall system. A general optical isolator consists of three basic parts: a polarizer or a polarizing beam splitter, which is composed of a polarizer or a birefringent crystal to obtain polarized light; a Faraday rotator, which rotates the polarization state of the beam; an analyzer or The polarization beam combiner couples out the light that meets the polarization conditions. Refer to the article "Research on the Structural Types of Optical Isolators" published in "Journal of Xi'an University of Posts and Telecommunications" in Volume 8, No. 3, July 2003.

Existing optical isolators are mainly used in laser processing systems and optical communication systems to protect the laser itself and reduce system noise: for example, in distributed feedback (DFB) lasers, the chirp phenomenon caused by optical path echo is reduced; In Erbium Fiber Amplifier (EDFA), it can reduce the optical path noise, protect the front-end light source, and realize the stability of the amplifier.

At present, with the widespread development of high-power fiber lasers and their applications, the demand for high-power isolation devices is gradually increasing, requiring optical isolators to develop in the direction of high power, low cost, and small size. However, the design of domestic optical isolators is mainly concentrated in the low-to-medium power range below 100W. When the work is higher than 100W, the isolation is low, and the thermal effect of temperature is obvious, which affects the stability of the internal magnetic field of the optical isolator and the magneto-optical crystal. The depolarization characteristics make it unable to achieve the expected optical rotation angle, and the volume is large and the structure is complex, so it cannot achieve long-term operation under high-power conditions.

Contents of the invention

In order to realize the high power, long life and small volume of the optical isolator, the present invention designs an optical isolator based on high magnetic field strength combined with external crystal compensation. In the optical isolator, the compensation crystal is externally added to the five-segment magnetic ring structure of the cascaded structure, which is beneficial to reduce the depolarization degree and improve the isolation degree of the optical isolator. The optical isolator of the present invention is arranged in a cascaded manner, so that the volume is small, and it is more suitable for the application of fiber lasers with a power of one hundred watts and above.

The invention is a cascadable high-power optical isolator for fiber lasers, the optical isolator includes an optical adjustment component (1), a magnet component (2), an inner fastening component (3), a base ( 4) and end cap (5);

One end of the base (4) is provided with an external joint (4A), and the open end (4G) of the other end of the base (4) is threadedly connected with the external thread (5A1) of the end cover (5) through an internal thread (4G1). The outer cylinder (4F) of the base (4) is provided with a bottom plate (4C), and the inside of the base (4) is provided with an AB countersunk cavity (4E), an AA countersunk cavity (4D) and an A cavity (4B ). The A cavity (4B) is used to install the A fiber collimator (13), and the incoming fiber (11) on the A fiber collimator (13) protrudes from the outer joint (4A). The AA countersunk cavity (4D) is used to install the A polarizer (15). A fixed seat (34), an inner positioning ring (33), a sleeve (32), and an inner end cover (31) of A are installed in the AB countersunk cavity (4E).

One end of the end cover (5) is provided with a threaded joint (5A), and the other end of the end cover (5) is provided with an external joint (5C), and a circle is formed between the threaded joint (5A) and the external joint (5C). Ring baffle (5D). The middle part of the end cover (5) is provided with a countersunk cavity (5B) and a B cavity (5E). The B cavity (5E) is used to install the B fiber collimator (14), and the pigtail (12) on the B fiber collimator (14) protrudes from the outer joint (5C). The countersunk cavity (5B) is used to install the B polarizer (16).

The inner fastening component (3) includes an inner end cover (31), a sleeve (32), an inner positioning ring (33) and a fixing seat (34). The middle part of inner end cover (31) is provided with A through hole (31C), and the disc (31A) of inner end cover (31) is provided with A convex round table (31B), and this A convex round table (31B) is provided with outer thread. The middle part of the sleeve (32) is a B through hole (32A), and one end of the sleeve (32) is provided with a retaining ring (32B). The retaining ring (32B) is provided with external threads, and the other end of the sleeve (32) An inner concave cavity (32C) is provided, and internal threads are arranged on the inner concave cavity (32C). The A convex round platform (31B) of the inner end cap (31) is placed in the inner concave cavity (32C) of the sleeve (32), and is threaded. The middle part of the inner positioning ring (33) is provided with a C through hole (33A), and an end panel of the disc (33C) of the inner positioning ring (33) is provided with a convex ring (33B), and the inner positioning ring (33 ) The other end panel of the disk (33C) is provided with a B convex round platform (33D), and the B convex round platform (33D) is provided with external threads. The B boss (33D) of the inner positioning ring (33) is placed in the stop ring (32B) of the sleeve (32), and is threaded. The middle part of the fixed seat (34) is provided with a D through hole (34A), and one end panel of the disc (34E) of the fixed seat (34) is provided with a C inner cavity (34B) and a D inner cavity (34C), and the fixed The other end panel of the disk (34E) of the seat (34) is provided with a groove (34D). A positioning plate (19) is installed in the inner concave cavity (34B) of C, a compensation crystal (17) is installed in the inner concave cavity (34C) of D, and a convex circle of the inner positioning ring (33) is installed in the groove (34D) Ring (33B).

The magnet assembly (2) includes a first magnetic ring (21) with a BA through hole (21A) in the middle, a second magnetic ring (22) with a BB through hole (22A) in the middle, and a BC through hole (22A) in the middle. 23A), the third magnetic ring (23), the fourth magnetic ring (24) with the BD through hole (24A) in the middle, and the fifth magnetic ring (25) with the BE through hole (25A) in the middle. The second magnetic ring (22) has the same structure as the third magnetic ring (23), and the fourth magnetic ring (24) has the same structure as the fifth magnetic ring (25).

The light adjustment component (1) includes A fiber collimator (13), B fiber collimator (14), A polarizer (15), B polarizer (16), compensation crystal (17), magneto-optical rotation crystal (18) and positioning plate (19); Wherein, the structure of A fiber collimator (13) and B fiber collimator (14) is identical, and the structure of A polarizer (15) is identical with B polarizer (16). The optical fiber on the A fiber collimator (13) is the input fiber (11) of the optical isolator, and the optical fiber on the B optical fiber collimator (14) is the pigtail fiber (12) of the optical isolator. A fiber collimator (13), A polarizer (15), positioning plate (19), compensation crystal (17), magneto-optical rotation crystal ( 18), B polarizer (16) and B fiber collimator (14). The middle part of the positioning plate (19) is provided with a through hole (19A), and one side of the positioning plate (19) is provided with an A groove (19B) and a B groove (19C).

The magnet assembly (2), the internal fastening assembly (3) and the compensating crystal (17) in the light adjustment assembly (1), the magneto-optical rotation crystal (18) and the positioning plate (19) are assembled to form a cascade unit (10) . A cascaded optical isolator obtained by connecting two cascaded units (10) in series. A triple cascaded optical isolator obtained by connecting three cascaded units (10) in series.

The beneficial effect of the optical isolator designed by the present invention is:

The first is to design a composite magnetic field. The composite magnetic field is composed of five-segment magnets with axial magnetic field, radial magnetic field and oblique magnetic field, which can generate a strong magnetic field with better uniformity, reduce depolarization caused by uneven magnetic field and thermal effect, and realize Shorten the length of the magneto-optical active crystal, and improve the isolation of the optical isolator under high-power conditions.

The second is to combine the external crystal compensation with the magneto-optical crystal, and add a compensation crystal with opposite thermal characteristics to the magneto-optical crystal at the front of the magnet structure. By matching the crystal orientation of the compensation crystal and the magneto-optic crystal, and compensating The thermally induced depolarization effect of the optically active crystal improves the maximum allowable incident power value of the optical isolator under certain isolation and insertion loss requirements.

The third is to design a cascadable structure. The optical isolator with a detachable cascaded structure has a wider range of applications and can meet the isolation requirements of different magneto-optical crystal materials.

In the results of the optical isolator designed in the present invention, the length of the magnetoactive crystal and the magnet is shortened, and the cascaded structure has good heat dissipation performance, which greatly reduces the thermally induced depolarization effect and the magnetically induced depolarization effect, and improves the optical isolation The working stability of the device, and the number of cascades can be selected according to the specific requirements of the magneto-optical crystal material and the optical isolator. It is easy to assemble and disassemble, and has a wide range of applications.

Description of drawings

Fig. 1 is an external structure diagram of a cascadable high-power optical isolator for fiber laser designed in the present invention.

FIG. 1A is a left side view of FIG. 1 .

Fig. 1B is an enlarged cross-sectional view of A-A.

Fig. 1C is an exploded view of the cascadable high-power optical isolator for fiber laser designed in the present invention.

Fig. 2 is a structural diagram of the base designed by the present invention.

Fig. 2A is a cross-sectional view of the base designed in the present invention.

Fig. 3 is a cross-sectional view of the end cap designed by the present invention.

Fig. 4A is a structural view of the inner end cap in the inner fastening assembly designed by the present invention.

Fig. 4B is a structural view of the sleeve in the inner fastening assembly designed by the present invention.

Fig. 4C is a structural view of the positioning ring in the inner fastening component designed by the present invention.

Fig. 4D is a structural view of the positioning seat in the inner fastening assembly designed by the present invention.

Fig. 4E is another perspective structural view of the positioning seat in the inner fastening assembly designed by the present invention.

Fig. 5 is a structural diagram of the positioning plate designed by the present invention.

Fig. 6 is a structural diagram of a cascade unit of the present invention.

Fig. 6A is a cross-sectional view of a cascaded unit of the present invention.

Fig. 7 is a structural diagram of two cascade units of the present invention.

Figure 7A is a cross-sectional view of two cascaded units of the present invention.

Fig. 8 is a graph showing the relationship between isolation and power of multiple cascaded units in the optical isolator designed in the present invention.

Fig. 9 is a schematic diagram of the magnetic structure of the magnetic ring assembly of the present invention.

Fig. 9A is a magnetic field distribution curve of the magnetic ring assembly of the present invention in the magneto-optical crystal region.

1. Light adjustment components 11. Fiber entry 12. Pigtail 13.A fiber collimator 14.B fiber collimator 15. A polarizer 16.B Polarizer 17. Compensation crystal 18. Magneto-active crystals 19. Positioning plate 19A. Through hole 19B.A groove 19C.B groove 2. Magnet assembly 21. The first magnetic ring 21A.BA through hole 22. The second magnetic ring 22A.BB countersunk through hole 23. The third magnetic ring 23A.BC countersunk through hole 24. The fourth magnetic ring 24A.BD through hole 25. The fifth magnetic ring 25A.BE through hole 3. Internal fastening components 31. Inner end cap 31A. Disc 31B.A Convex table 31C.A through hole 32. Sleeve 32A.B through hole 32B. Ring baffle 32C.A concave cavity

33. Inner positioning ring 33A.C through hole 33B. Convex ring 33C. Disc 33D.B Convex table 34. Fixing seat 34A.D through hole 34B.C concave cavity 34C.D inner cavity 34D. groove 34E. Disc 4. Base 4A. External connector 4B.A cavity 4C. Bottom plate 4D.AA countersunk cavity 4E.AB countersunk cavity 4F. Outer cylinder 4G. Open end 4G1. Internal thread 5. End cap 5A. Threaded joints 5A1. External thread 5B. Countersunk cavity 5C. Outer connector 5D. Ring baffle 5E.B cavity 10. A cascade unit 20.B cascade unit 217.B compensation crystal 218.B Magneto-optical active crystal 219.B positioning board 221. The sixth magnetic ring 222. Seventh magnetic ring 223. The eighth magnetic ring 224. Ninth Magnetic Ring 225. The tenth magnetic ring 231.B inner end cover 232.B Sleeve 233.B Inner positioning ring 234.B fixed seat 30. Two-stage optical isolator

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings.

Referring to Fig. 1, Fig. 1A, Fig. 1B, and Fig. 1C, a cascadable high-power optical isolator for fiber lasers designed by the present invention, the optical isolator includes an optical adjustment assembly 1, a magnet Component 2, inner fastening component 3, base 4 and end cap 5.

The assembly of a cascadable high-power optical isolator for fiber lasers designed by the present invention is as follows: referring to shown in Figure 1B, the magneto-active optical crystal 18 is first installed in the magnet assembly 2; then the A fiber is collimated The device 13 is installed at the external joint 4A of the base 4, and the optical fiber of the A fiber collimator 13 stretches out from the external joint 4A of the base 4, and the A polarizer 15 is installed in the AA countersunk cavity 4D of the external joint 4A; The positioning plate 19 is installed in the C inner cavity 34B of the fixed seat 34, the compensation crystal 17 is installed in the D inner cavity 34C, and the convex ring 33B of the inner positioning ring 33 is installed in the groove 34D; the B convex ring 33 of the inner positioning ring 33 The round platform 33D is placed in the stop ring 32B of the sleeve 32, the magnet assembly 2 is installed in the sleeve 32, and the inner end cover 31 is installed at the other end of the sleeve 32; then the B polarizer 16 is installed in the countersunk cavity 5B of the end cover 5 Among them, the B fiber collimator 14 is installed in the B cavity 5E of the end cap 5, and the optical fiber of the B fiber collimator 14 protrudes from the end cap 5; finally, the end cap 5 is screwed to the base 4.

Light Adjustment Components 1

Referring to Fig. 1B and shown in Fig. 1C, the light adjustment assembly 1 includes A fiber collimator 13, B fiber collimator 14, A polarizer 15, B polarizer 16, compensation crystal 17, magnetically induced optical rotation crystal 18 and positioning Plate 19; wherein, the A fiber collimator 13 and the B fiber collimator 14 have the same structure, and the A polarizer 15 and the B polarizer 16 have the same structure. The optical fiber on the A fiber collimator 13 is the input fiber 11 of the optical isolator, and the optical fiber on the B fiber collimator 14 is the pigtail fiber 12 of the optical isolator. Arranged in order from the input fiber 11 to the pigtail 12 are A fiber collimator 13, A polarizer 15, positioning plate 19, compensation crystal 17, magneto-rotating crystal 18, B polarizer 16 and B fiber collimator 14 .

As shown in FIG. 5 , the positioning plate 19 is an integrally formed structural member. A through hole 19A is provided in the middle of the positioning plate 19 , and an A groove 19B and a B groove 19C are provided on one side of the positioning plate 19 . The two grooves ( 19B, 19C) arranged symmetrically are beneficial to the lamination of the A polarizer 15 and the panel of the positioning plate 19 .

In the present invention, the central wavelength of the A fiber collimator 13 and the B fiber collimator 14 is 1064nm, and the maximum optical power is 150W, and the model SR1406006A produced by Shenzhen Guangyue Technology Co., Ltd. can be selected.

In the present invention, the use wavelength of A polarizer 15 and B polarizer 16 is 700-3500nm, the transmittance reaches 95% at 1064nm, and the extinction ratio is less than 5×10 ^-6 , which can be selected from Fuzhou Hanguang Optoelectronics Co., Ltd. The PGL1708 model produced by the company.

In the present invention, the crystal orientation of the compensation crystal 17 is 001, and the transmittance is greater than 99% under the condition of 1064nm. The Win3025 model produced by Fuzhou Hanguang Optoelectronics Co., Ltd. can be selected.

In the present invention, the working wavelength of the magneto-optical active crystal 18 is 1064nm and the extinction ratio is less than 10 ^-3 , and the magneto-optic crystal with crystal orientation 001 produced by Shenzhen Mingchuang Optoelectronics Co., Ltd. can be selected.

For high-power optical isolators based on cascaded Faraday rotators, in order to withstand high-power working environments, high-power double-clad fiber collimators are used. The pigtail is double-clad fiber, and the collimator using fixed refractive index lenses The device achieves collimation and high efficiency for high-power beam transmission. The light-transmitting surface of each crystal and optical device is coated with an anti-reflection film, which can effectively reduce the return loss. The coupling efficiency of the fiber collimator reaches more than 95%, and the collimation distance of the working space of the fiber collimator can reach 150mm, which meets the collimation requirements of a long distance.

Magnet Assembly 2

Referring to Fig. 1B and Fig. 1C, the magnet assembly 2 includes a first magnetic ring 21, a second magnetic ring 22, a third magnetic ring 23, a fourth magnetic ring 24 and a fifth magnetic ring 25, the second magnetic ring 22 has the same structure as the third magnetic ring 23 , and the fourth magnetic ring 24 has the same structure as the fifth magnetic ring 25 .

The middle part of the first magnetic ring 21 is provided with a BA through hole 21A.

The middle part of the second magnetic ring 22 is provided with a BB countersunk through hole 22A.

The middle part of the third magnetic ring 23 is provided with a BC countersunk through hole 23A.

The middle part of the fourth magnetic ring 24 is provided with a BD through hole 24A.

The middle part of the fifth magnetic ring 25 is provided with a BE through hole 25A.

In the present invention, magneto-active crystals 18 are installed in the through holes of the second magnetic ring 22 , the first magnetic ring 21 and the third magnetic ring 23 . That is, the magneto-optical crystal 18 is first placed in the BC countersunk through hole 23A of the third magnetic ring 23, then the first magnetic ring 21 is socketed on the outside of the magneto-optical crystal 18, and finally the third magnetic ring is socketed twenty three.

In the present invention, the material of the magnetic ring in the magnet assembly 2 is sintered NdFeB. The magnetic ring selects the N48H type magnet produced by Jiaozuo Jicheng Magnetic Electric Co., Ltd.

Referring to Figure 9, in the present invention, the magnetization directions of the magnetic rings are arranged as follows:

The first magnetic ring 21 is an axially magnetized magnet. That is, the magnetization direction of the first magnetic ring 21 is parallel to the X-axis of the optical isolator.

The second magnetic ring 22 is an obliquely magnetized magnet. That is, there is an angle γ between the magnetization direction of the second magnetic ring 22 and the positive direction of the X-axis of the optical isolator, and this angle is also called a magnetization angle.

The third magnetic ring 23 is an obliquely magnetized magnet. That is, there is an angle between the magnetization direction of the third magnetic ring 23 and the negative direction of the X-axis of the optical isolator, and the angle is the same as the magnetization angle γ.

The fourth magnetic ring 24 is a radially magnetized magnet. That is, the magnetization direction of the fourth magnetic ring 24 is perpendicular to the X-axis of the optical isolator and faces outward.

The fifth magnetic ring 25 is a radially magnetized magnet. That is, the magnetization direction of the fifth magnetic ring 25 is perpendicular to the X-axis of the optical isolator and faces inward.

In the present invention, the magnet assembly is designed in five sections, which improves the attraction force of each magnet and also improves the efficiency of the permanent magnet. In addition, the magnetoactive crystal 18 is nested in the cavity formed by the through holes on the first magnetic ring 21, the second magnetic ring 22 and the third magnetic ring 23 through the interference fit of the copper film, making the structure more compact and stable. The performance is better, and it is also beneficial to the heat dissipation of the magneto-optical crystal 18.

In the present invention, the compensation crystal 17 is clamped in the cavity of the fixed seat 34, and the crystal orientation of the fixed seat 34 is rotated to match the crystal orientation of the magneto-optical active crystal 18 to achieve the maximum thermal compensation effect.

In order to verify the correlation between the magnetic field distribution of the magnet assembly 2 and the compensation crystal 17 and the magneto-optical crystal 18: by determining the inner diameter and outer diameter of the magnet, simulate the thickness of each section of the magnet (a ₂₁ is the thickness of the first magnetic ring, a ₂₂ is the thickness of the second magnetic ring, a ₂₃ is the thickness of the third magnetic ring, a ₂₄ is the thickness of the fourth magnetic ring, a ₂₅ is the thickness of the fifth magnetic ring, and a ₂₂ =a ₂₃ , a ₂₄ =a ₂₅ ), so that The magnetic field strength is the largest and the uniformity is better, thereby improving the isolation of high-power optical isolators. If the high-performance permanent magnet material NdFeB (Nd ₂ Fe ₁₄ B) is used for the magnetic ring, when the inner diameter of the magnet is 5mm and the outer diameter is 25mm, the simulation is carried out according to K.Halbach's rotation theorem and the basic principle of magnetic field design, and the current a ₂₂ ＝a ₂₃ ＝4.6mm, the positive X-axis magnetization angle γ＝2.1rad, that is, when a ₂₄ ＝a ₂₅ ＝21mm, a ₂₁ ＝4.8mm, as shown in Figure 9A, the magnet assembly designed by the present invention The central magnetic induction of 2 can reach a maximum of 2.4T, and the average magnetic induction is 2.2T. If the cubic crystal TGG (terbium gallium garnet) is used as the magnetoactive crystal, the length of the magnetoactive crystal only needs to be 10.2 mm to meet the requirement. The isolator designed by applying the invention realizes the goals of high isolation, low cost and small volume.

In the present invention, an external compensation crystal 17 cooperates with the magneto _- optical active crystal 18, which can greatly reduce the thermally induced depolarization effect of the fiber laser. Crystal, for an optical isolator of a cascade unit, the power of the optical isolator is above the order of 100 watts, and the isolation of the optical isolator can be increased by 10dB.

Inner fastening component 3

Referring to FIG. 1B and FIG. 1C , the inner fastening assembly 3 includes an inner end cap 31 , a sleeve 32 , an inner positioning ring 33 and a fixing seat 34 .

Referring to FIG. 4A , the inner end cover 31 is an integrally formed structural member. A through hole 31C is provided in the middle of the inner end cover 31, and an A convex round platform 31B is provided on the disk 31A of the inner end cover 31, and an external thread is provided on the A convex round platform 31B.

Referring to FIG. 4B , the sleeve 32 is an integrally formed structural member. The middle part of the sleeve 32 is a B through hole 32A, and one end of the sleeve 32 is provided with a stop ring 32B, and the stop ring 32B is provided with an external thread, and the other end of the sleeve 32 is provided with an inner cavity 32C, and the inner cavity 32C There are internal threads on it. The A-convex platform 31B of the inner end cap 31 is placed in the inner concave cavity 32C of the sleeve 32 and is screwed.

Referring to FIG. 4C , the inner positioning ring 33 is an integrally formed structural member. The middle part of the inner positioning ring 33 is provided with a C through hole 33A, and one end panel of the disc 33C of the inner positioning ring 33 is provided with a convex ring 33B, and the other end panel of the inner positioning ring 33 of the disc 33C is provided with a C through hole 33A. The B convex platform 33D is provided with an external thread on the B convex platform 33D. The B boss 33D of the inner positioning ring 33 is placed in the retaining ring 32B of the sleeve 32 and is threaded.

Referring to FIG. 4D and FIG. 4E , the fixing seat 34 is an integrally formed structural member. The middle part of fixed seat 34 is provided with D through hole 34A, is provided with C inner cavity 34B and D inner concave cavity 34C on the one end panel of the disk 34E of fixed seat 34, is provided with on the other end panel of the disc 34E of fixed seat 34. There is groove 34D. A positioning plate 19 is installed (such as bonding) in the C inner cavity 34B, a compensation crystal 17 is installed (such as bonding) in the D inner cavity 34C, and a convex ring 33B of the inner positioning ring 33 is installed in the groove 34D .

Referring to Fig. 1B, the assembly of the inner fastening component 3 is as follows: the positioning plate 19 is installed in the inner cavity 34B of the C of the fixed seat 34, the compensation crystal 17 is installed in the inner cavity 34C of the D cavity, and the inner positioning ring is installed in the groove 34D The convex ring 33B of 33; the B convex round platform 33D of the inner positioning ring 33 is placed in the retaining ring 32B of the sleeve 32, and the other end of the sleeve 32 is installed with an inner end cover 31.

The inner fastening assembly 3 is sleeved on the outside of the magnet assembly 2, which can improve the magnetic concentration effect of the magnet assembly 2, and can also reduce the temperature of the magnet assembly 2 in the working state. The internal fastening assembly 3 is used to position the compensation crystal 17, the magneto-optical rotator crystal 18 and the positioning plate 19 in the magnet assembly 2 and the light adjustment assembly 1, so as to realize the integration of cascaded units, and when multiple cascaded units are connected in series, the It is ensured that the crystal orientations of the compensation crystal 17 and the magneto-optical crystal 18 have a certain included angle, which is beneficial to improve the isolation. The magnet assembly 2 and part of the light adjustment assembly 1 are assembled through the inner fastening assembly 3 , then installed in the base 4 , and finally the upper end cover 5 is screwed.

In the present invention, the inner fastening component 3 is processed with metal materials, such as aluminum alloy (such as 6063 grade).

Base 4

Referring to FIG. 1 , FIG. 1A , FIG. 1B , FIG. 1C , FIG. 2 , and FIG. 2A, the base 4 is an integrally formed structural member. One end of the base 4 is provided with an external joint 4A, and the other end of the base 4 is an opening. A bottom plate 4C is provided on the outer cylinder 4F of the base 4, and the optical isolator designed in the present invention can be stably placed through the bottom plate 4C. The inside of the base 4 is provided with an AB countersunk cavity 4E, an AA countersunk cavity 4D and an A cavity 4B.

The A cavity 4B inside the base 4 is used for installing (for example, bonding) the A fiber collimator 13 , and the input fiber 11 on the A fiber collimator 13 extends out of the outer connector 4A.

The AA countersunk cavity 4D inside the base 4 is used for installing (such as bonding) the A polarizer 15 . There is an interval b (in millimeters) between the A polarizer 15 and the A fiber collimator 13, where b=1˜5 mm.

The AB countersunk cavity 4E inside the base 4 is equipped with a fixed seat 34, an inner positioning ring 33, a sleeve 32, and an inner end cover 31 of A. Thread 5A1 realizes threaded connection. The base 4 is used to install the A fiber collimator 13 and the A polarizing plate 15 on the light adjustment assembly 1, which facilitates the layout of the cascaded units in series and enables the realization of a miniaturized structure.

In the present invention, the base is processed with metal materials, such as aluminum alloy (such as 6063 grade).

end cap 5

Referring to FIG. 1 , FIG. 1B , FIG. 1C , and FIG. 3 , the end cover 5 is an integrally formed structural member. One end of the end cover 5 is provided with a threaded joint 5A, and the other end of the end cover 5 is provided with an outer joint 5C, and an annular baffle 5D is located between the threaded joint 5A and the outer joint 5C. The middle part of the end cap 5 is provided with a countersunk cavity 5B and a B cavity 5E.

The B cavity 5E is used for installing (such as bonding) the B fiber collimator 14, and the pigtail 12 on the B fiber collimator 14 extends out of the outer joint 5C.

The countersunk cavity 5B is used for installing (such as bonding) the B polarizer 16 . There is an interval d (in millimeters) between the B polarizer 16 and the B fiber collimator 14, where d=10-25 mm.

An external thread 5A1 is provided on the external joint 5C of the end cap 5 , and the external thread 5A1 is used for thread engagement with the internal thread 4G1 on the open end 4G of the base 4 to realize the fixing of the end cap 5 and the base 4 . Using the end cap 5 to install the B fiber collimator 14 and the B polarizer 16 on the light adjustment assembly 1 facilitates the layout of the series cascaded units and enables the realization of a miniaturized structure.

In the present invention, the end cap is processed with metal materials, such as aluminum alloy (eg, 6063 grade).

Optical Isolator in Cascaded Structure

Referring to Fig. 6 and Fig. 6A, in the present invention, after the magnet assembly 2, the internal fastening assembly 3, and the compensation crystal 17, the magneto-optic crystal 18, and the positioning plate 19 in the light adjustment assembly 1 are assembled, a cascade is formed. Unit 10.

In order to achieve high isolation of the optical isolator under high power, no more than three cascaded units can be connected in series, and the isolation comparison of the cascaded structure optical isolator obtained in series is shown in Figure 8.

Referring to FIG. 7 and FIG. 7A , it is a structural diagram of a cascaded optical isolator 30 (without a base and an end cover) obtained by connecting two cascaded units 10 in series. The B cascade unit 20 includes a B magnet component, a B inner fastening component, a B compensation crystal 217 , a B magneto-optical crystal 218 and a B positioning plate 219 .

The B magnet assembly includes a sixth magnetic ring 221 , a seventh magnetic ring 222 , an eighth magnetic ring 223 , a ninth magnetic ring 224 and a tenth magnetic ring 225 . The B magnet assembly has the same structure as the magnet assembly 2 .

The B inner fastening assembly includes a B inner end cap 231 , a B sleeve 232 , a B inner positioning ring 233 and a B fixing seat 234 . The internal fastening component of B has the same structure as the internal fastening component 3 .

Referring to FIG. 8 , the figure shows the variation of the isolation degree of one to three optical isolators with and without compensation crystals with the incident light power. Fig. 8 does not take into account the maximum optical power carried by the fiber collimator (13, 14). As the number of cascaded optical isolators increases, the isolation of the optical isolator increases gradually, but the insertion loss of the isolator also increases.

In the present invention, if the fiber laser system requires a higher isolation degree of the optical isolator, a triple cascaded optical isolator formed by connecting three cascaded units in series is selected. When the incident power of the three-cascade optical isolator is 1000W, the isolation is higher than 35dB.

In the present invention, if the fiber laser system requires higher insertion loss of the optical isolator, a cascaded optical isolator formed by connecting two cascaded units in series is selected. When the incident power of the two-stage optical isolator is 1000W, the isolation is higher than 30dB.

In the present invention, if the optical isolator needs to be miniaturized in the fiber laser system, a single-stage optical isolator with a cascaded unit is selected. When the incident power of the single cascade optical isolator is 1000W, the isolation can reach 27dB.

Claims (7)

1. A cascadable high-power optical isolator for fiber lasers, characterized in that: the optical isolator includes an optical adjustment assembly (1), a magnet assembly (2), an inner fastening assembly (3 ), the base (4) and the end cap (5); the center magnetic induction of the magnet assembly (2) reaches a maximum of 2.4T, and the average magnetic induction is 2.2T; One end of the base (4) is provided with an external joint (4A), and the open end (4G) of the other end of the base (4) is threadedly connected with the external thread (5A1) of the end cover (5) through an internal thread (4G1); The outer cylinder (4F) of the seat (4) is provided with a bottom plate (4C), and the inside of the base (4) is provided with an AB countersunk cavity (4E), an AA countersunk cavity (4D) and an A cavity (4B) ; A cavity (4B) is used to install the A fiber collimator (13), and the input fiber (11) on the A fiber collimator (13) stretches out of the external connector (4A); AA countersunk head cavity (4D) is used A polarizer (15) is installed; a fixed seat (34), an inner positioning ring (33), a sleeve (32), and an inner end cover (31) of A are installed in the AB countersunk cavity (4E); One end of the end cover (5) is provided with a threaded joint (5A), and the other end of the end cover (5) is provided with an external joint (5C), and a circle is formed between the threaded joint (5A) and the external joint (5C). A ring baffle (5D); the middle part of the end cover (5) is provided with a countersunk cavity (5B) and a B cavity (5E); the B cavity (5E) is used to install a B fiber collimator (14), And the pigtail (12) on the B fiber collimator (14) stretches out from the outer joint (5C); the countersunk cavity (5B) is used to install the B polarizer (16); The inner fastening assembly (3) includes an inner end cover (31), a sleeve (32), an inner positioning ring (33) and a fixing seat (34); the middle part of the inner end cover (31) is provided with a through hole ( 31C), the disc (31A) of the inner end cap (31) is provided with an A convex round table (31B), and the A convex round table (31B) is provided with external threads; the middle part of the sleeve (32) is a B through hole ( 32A), one end of the sleeve (32) is provided with a retaining ring (32B), and the retaining ring (32B) is provided with an external thread, and the other end of the sleeve (32) is provided with a concave cavity (32C), and the concave The cavity (32C) is provided with an internal thread; the A convex round platform (31B) of the inner end cover 31 is placed in the inner concave cavity (32C) of the sleeve (32), and is threaded; the inner positioning ring (33) The middle part is provided with C through hole (33A), and an end panel of the disk (33C) of the inner positioning ring (33) is provided with a convex ring (33B), and the inner positioning ring (33) of the disk (33C) The other end panel is provided with a B convex round table (33D), and the B convex round table (33D) is provided with external threads; the B convex round table (33D) of the inner positioning ring (33) is placed in the retaining ring ( 32B), and is threaded; the middle part of the fixed seat (34) is provided with a D through hole (34A), and one end panel of the disc (34E) of the fixed seat (34) is provided with a C inner cavity (34B) and D inner concave cavity (34C), the other end panel of the disc (34E) of the fixed seat (34) is provided with groove (34D); C inner concave cavity (34B) is equipped with positioning plate (19), D inner A compensation crystal (17) is installed in the concave cavity (34C), and a convex ring (33B) of the inner positioning ring (33) is installed in the groove (34D); the crystal orientation of the compensation crystal (17) is 001, and the magnetism The crystal orientation of the optically active crystal (18) is 001; The magnet assembly (2) includes a first magnetic ring (21) with a BA through hole (21A) in the middle, a second magnetic ring (22) with a BB through hole (22A) in the middle, and a BC through hole (22A) in the middle. 23A), the third magnetic ring (23), the fourth magnetic ring (24) with the BD through hole (24A) in the middle, and the fifth magnetic ring (25) with the BE through hole (25A) in the middle. The second magnetic ring (22) has the same structure as the third magnetic ring (23), and the fourth magnetic ring (24) has the same structure as the fifth magnetic ring (25); The light adjustment component (1) includes A fiber collimator (13), B fiber collimator (14), A polarizer (15), B polarizer (16), compensation crystal (17), magneto-optical rotation crystal (18) and positioning plate (19); Wherein, the structure of A fiber collimator (13) is identical with B fiber collimator (14), and the structure of A polarizer (15) is identical with B polarizer (16); The optical fiber on the A fiber collimator (13) is the fiber entry (11) of the optical isolator, and the optical fiber on the B fiber collimator (14) is the pigtail fiber (12) of the optical isolator; A fiber optic collimator (13), a polarizer (15), a positioning plate (19), a compensation crystal (17), and a magneto-rotating crystal (18) are arranged in sequence from the fiber (11) to the pigtail (12) , B polarizer (16) and B fiber collimator (14); The middle part of positioning plate (19) is provided with through hole (19A), and one side of positioning plate (19) is provided with A groove (19B) and B groove (19C); the interval between A polarizer (15) and A fiber collimator (13) is 1-5 mm; the interval between B polarizer (16) and B fiber collimator (14) 10-25mm; The magnet assembly (2), the internal fastening assembly (3) and the compensating crystal (17) in the light adjustment assembly (1), the magneto-optical rotation crystal (18) and the positioning plate (19) are assembled to form a cascade unit (10) . 2. A cascadable high-power optical isolator for fiber lasers according to claim 1, characterized in that it is a cascaded optical isolator obtained by connecting two cascading units (10) in series. 3. A cascadable high-power optical isolator for fiber lasers according to claim 1, characterized in that: three cascaded optical isolators obtained in series by three cascaded units (10). 4. A kind of cascadable high-power optical isolator for fiber laser according to claim 1 or 2 or 3, characterized in that: The first magnetic ring (21) is an axially magnetized magnet; that is, the magnetization direction of the first magnetic ring (21) is parallel to the X-axis of the optical isolator; The second magnetic ring (22) is an oblique magnetized magnet; that is, there is an included angle γ between the magnetization direction of the second magnetic ring (22) and the positive direction of the X-axis of the optical isolator, and this included angle is also called a magnetized included angle; The third magnetic ring (23) is an oblique magnetized magnet; it is an oblique magnetized magnet; that is, there is an angle between the magnetization direction of the third magnetic ring (23) and the negative direction of the X axis of the optical isolator, and the angle is the same as that of the optical isolator. The angle of the magnetization angle γ is the same; The fourth magnetic ring (24) is a radially magnetized magnet; that is, the magnetization direction of the fourth magnetic ring (24) is perpendicular to the X-axis of the optical isolator and outward; The fifth magnetic ring (25) is a radially magnetized magnet; that is, the magnetization direction of the fifth magnetic ring (25) is perpendicular to the X-axis of the optical isolator and faces inward. 5. A cascadable high-power optical isolator for fiber lasers according to claim 1, 2 or 3, characterized in that: the three-cascade optical isolator has a high isolation when the incident power is 1000W at 35dB. 6. A cascadable high-power optical isolator for fiber lasers according to claim 1, 2 or 3, characterized in that: when the incident power of the cascaded optical isolator is 1000W, the isolation is high at 30dB. 7. A cascadable high-power optical isolator for fiber lasers according to claim 1, 2 or 3, characterized in that: when the incident power of a single cascaded optical isolator is 1000W, the isolation reaches 27dB.