Miniature optical isolation core

Abstract

The utility model discloses an optical communication wave band micro isolator core CORE structure with a circular cross section of a crystal group, and compared with the prior art, the optical communication wave band micro isolator core CORE structure has the beneficial effects that the crystal group with the circular cross section is matched with a cylindrical magnetic tube, so that invalid and wasted space can be saved, and the size of the isolation core CORE can be smaller; the crystal group with the circular cross section can save more materials, so that the cost of the isolation core CORE can be reduced; the adhesive layer can be more uniform and full, so that the temperature stability of the isolation core CORE can be improved.

Description

Technical Field

[0001] The present invention relates to the manufacture of optical isolation cores, and particularly to an optical isolation core structure in which the cross-section of a crystal group is circular along the optical transmission direction. Background Art

[0002] An optical isolator is an optical device that utilizes the Faraday magneto-optical effect to enable forward conduction of a light beam while isolating it in the reverse direction. For an optical isolator used in the optical communication band (such as 1310 nm or 1550 nm), the core that realizes the Faraday magneto-optical effect is called an optical isolation core CORE. A typical structure is as Figure 1 shown. A cylindrical hollow magnetic ring 2 has a crystal group 1 fixed inside it. The three-dimensional structure of the crystal group 1 is as Figure 2 shown. In the center is a yttrium iron garnet YIG Faraday crystal 5, commonly known as a black sheet, and on the front and back sides are crystal (such as lithium niobate) wedge angle sheets 4, commonly known as white sheets. If fiber collimators are added to both ends of the CORE, a polarization-independent optical isolator can be made. The isolation core CORE can also be directly used in a collimated optical path, called a free space isolator FSI. In the FSI, the polarization and analyzing crystal wedge angle sheets 4 on both sides of the black sheet are changed to polarization flat sheets of 0° and 45°, becoming a polarization-dependent optical isolator.

[0003] Figure 1 The reason why the cross-section of the crystal group in is square is that in the optical communication industry, YIG is supplied in large thin sheets, for example, with dimensions of 11 mm * 11 mm * 0.42 mm. Optical isolator manufacturers use a dicing machine to cut the large sheet into small square grains horizontally and vertically, for example, with dimensions of 0.78 mm * 0.78 mm * 0.42 mm. The wedge angle sheets 4 (or polarization flat sheets) on both sides of the YIG black sheet 5 also need to be made into a square cross-sectional shape. When the crystal group 1 is inserted into the cylindrical magnetic tube 2, the four edges of the crystal group 1 contact the inner wall of the magnetic tube (actually with a small gap), and when bonding, the glue 3 also becomes four long glue strips along the four edges of the crystal group. Obviously, the four crescent-shaped spaces between the crystal group 1 and the inner wall of the magnetic tube 2 are wasted. For a crystal group 1 with a square cross-section, for a light beam with a circular cross-section (such as a diameter of 0.5 mm) passing through, the four sharp corner areas are also wasted. Due to the differences in the size and uniformity of the colloid 3, it also affects the temperature stability of the CORE.

[0004] However, in a 1064 nm fiber isolator with a larger size, as Figure 3 shown, since the magneto-optical crystal 7 used (such as terbium gallium garnet TGG) is itself a long column type, for example, with crystal dimensions of diameter 3 mm * length 15 mm, when it is inserted into the magnetic tube 2, it is the outer cylindrical surface of the crystal that contacts the inner cylindrical wall of the magnetic tube 2, and the glue layer 8 is a uniform and full cylinder. Summary of the Invention

[0005] An isolator in the optical communication band. In the prior art, the crystal group is made into a shape with a square cross-section. The technical problem solved by this application is to cut the commercially available YIG into a shape with a circular cross-section. Correspondingly, the crystal wedge angle pieces or polarization flat pieces on both sides of the YIG are also cut into shapes with circular cross-sections. In this way, the isolation core CORE can be made smaller in volume (because wasted space is saved), the cost can be reduced (because crystal materials are more saved), and the temperature stability of the isolation core CORE can be improved (because the adhesive layer is more uniform).

[0006] The specific content is as follows:

[0007] A micro optical isolation core, characterized in that it consists of a cylindrical magnetic tube and a crystal group adhesively bonded in the inner hole of the magnetic tube. The crystal group is circular in the cross-section along the optical transmission direction. The crystal group consists of a central YIG crystal sheet and crystal wedge angle pieces or polarization flat pieces on both sides. The optical transmission wavelength of the crystal group is the wavelength in the optical communication band.

[0008] Furthermore, for the YIG crystal sheet and the crystal wedge angle pieces or polarization flat pieces on both sides, the circular outer cylindrical surface is an ablation splitting surface formed after laser cutting a hole string and splitting the chips.

[0009] This application discloses a structure of a micro isolation core CORE in the optical communication band with a circular cross-section of the crystal group. Compared with the prior art, the beneficial effects that can be obtained are as follows: The crystal group with a circular cross-section can cooperate with the inner wall of the cylindrical magnetic tube, saving the ineffective and wasted space. Therefore, the isolation core CORE can be smaller in volume; the crystal group with a circular cross-section can save more materials, so the isolation core CORE can reduce costs; because the adhesive layer can be more uniform and full, the temperature stability performance of the isolation core CORE can be improved. Description of the Drawings

[0010] Figure 1 Is a front view of an isolation core with a square cross-section;

[0011] Figure 2 Is a three-dimensional schematic diagram of the crystal group of an isolation core with a square cross-section;

[0012] Figure 3 Is a front view of an isolation core with a circular cross-section;

[0013] Figure 4 Is a schematic diagram of cutting a large crystal piece into circular and square shapes;

[0014] Figure 5 Is a three-dimensional schematic diagram of the crystal group of an isolation core with a circular cross-section. Detailed Implementation Modes

[0015] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, rather than limiting the present application.

[0016] To solve the problems in the background art, the present application provides a new method for cutting black wafers and white wafers, that is, using a laser cutting machine to perform non-contact cutting on a crystal wafer (or a crystal group). After scribing, a crystal wafer (or a crystal group) with a circular cross-section in the light-transmitting direction is obtained.

[0017] Laser cutting of glass or crystals is a modern process, which can partially replace the traditional process of mechanical cutting plus grinding. Most laser cutting equipment uses fiber lasers, with various specifications, such as infrared, visible or ultraviolet wavelengths, picosecond or femtosecond pulse widths, and powers ranging from several watts to several hundred watts. For the commonly used cutting method of micro-precision lenses, a series of fine holes with a diameter in the micron range and a spacing in the micron range are drilled, and then "scribing" is performed to remove the waste edges and corners to obtain an optical lens with the desired shape.

[0018] In specific implementation, the applicant used a picosecond fiber laser with a wavelength of 1064 nm and a power of 50 W to drill holes in a YIG crystal. The obtained series of fine holes is a circular track series of fine holes with a single-hole diameter of 5 μm and a center distance of 8 μm between adjacent two holes. After scribing, the obtained crystal cylindrical surface is an ablation and splitting surface, and its roughness is like a finely ground surface under a microscope, and the thickness of the rough layer is about ten microns. The detailed laser drilling and scribing operation processes of the cutting machine are not described in detail in the present application.

[0019] As Figure 4 shown, still taking the example of scribing 0.78*0.78 small grains on an 11*11 large YIG piece in the prior art (for the convenience of description and understanding, the width of the slit formed by the scribing machine blade or the "slit" formed by the laser perforation series is equivalent and is included in the concept of the 0.78 dimension), 196 small square grains 5 can be cut out according to the prior art.

[0020] If a fiber laser is used to cut circular wafers, then (14 + 13)*8 = 216 small circular grains 6 can be cut out. Therefore, on an 11*11 large piece, under the premise of ensuring the same light-transmitting aperture, the number of small grains 6 that can be cut out is 10.2% more than the number of small grains 5 cut out by the prior art. This means that the raw material cost of the YIG crystal decreases, which represents a significant reduction space for the cost of optical communication isolators.

[0021] The crystal group with a circular cross-section obtained by laser cutting can be assembled into an isolation core CORE as Figure 3 shown. In this way, there is no four moon-shaped waste spaces between the crystal group and the inner wall of the magnetic tube as Figure 1 shown. As Figure 1For the circular light-transmitting cross-section beam, the four wasted sharp-corner areas are also gone. When the cross-section is a 0.78 * 0.78 square, 0.78 * 1.414 = 1.10, and the inner hole diameter of the magnetic tube can be selected as 1.15 mm; when the cross-section is a circle with a diameter of 0.78, the inner hole diameter of the magnetic tube can be selected as 0.83 mm. That is, on the premise of ensuring the same light-transmitting aperture diameter, the inner hole diameter (and the corresponding outer cylindrical surface diameter) of the magnetic tube can be made smaller. For example, the inner diameter of the magnetic tube is 0.83 mm and the outer diameter of the magnetic tube is 1.20 mm. In this way, the volume of the CORE is about 60% of the volume of the CORE when the crystal is cut into a square, which also means that cutting the cross-section of the crystal group into a circle is more conducive to the miniaturization of the CORE.

[0022] Since according to Figure 3 shown, the glue layer 8 is a cylindrical thin layer, which is more uniform than Figure 1 the four long glue strips, and the stress of the glue layer on the crystal group is more symmetrical, and the overall temperature stability of the CORE is improved compared to Figure 1 the structure.

[0023] There are two technical routes for manufacturing the crystal group of the optical isolation core. The first is to bond three independent small grains into a crystal group, and the second is to glue three large pieces and then cut the crystal group grains. Both the polarization-independent wedge angle piece type crystal group and the polarization-dependent polarizer type crystal group are acceptable, and the latter is particularly suitable for the second method. Laser cutting is applicable to both technical routes, that is, it can cut a single wafer or a large wafer group after bonding.

[0024] As Figure 5 shown, a small YIG crystal grain 6 with a circular light-transmitting cross-section and two small lithium niobate wedge angle pieces 9 with circular light-transmitting cross-sections can be combined into a crystal group of a polarization-independent CORE. It should be noted here that when laser cutting the small grain of the wedge angle piece 9, the cutting light beam needs to be shot vertically from the flat end rather than the inclined end of the wedge angle piece to prevent the cutting laser beam from refracting and deflecting in the crystal. This is the technical detail of laser cutting.

[0025] Obviously, the magneto-optical effect crystal targeted by this application is YIG, and the wavelength of the light transmitted by the crystal group is in the optical communication band, such as O-band, E-band, S-band, C-band, L-band, etc.

[0026] The above is only the preferred embodiment of this application and the technical principles applied. For those skilled in the art, without departing from the concept of the present invention, more other equivalent embodiments can be generated, and the protection scope of the present invention is determined by the scope of the appended claims.

Claims

1. A micro optical isolation core, characterized in that It is composed of a cylindrical magnetic tube and a crystal group adhesively fixed in the inner hole of the magnetic tube. The crystal group is circular in the cross-section along the light transmission direction. The crystal group is composed of a central YIG crystal sheet and crystal wedge angle sheets or polarization flat sheets on both sides. The light transmission wavelength of the crystal group is the wavelength in the optical communication band.

2. The miniature optical isolation core according to claim 1, characterized in that, The circular outer cylindrical surfaces of the YIG crystal sheet and the crystal wedge angle sheets or polarization flat sheets on both sides are ablation splitting surfaces formed after laser cutting hole series and splitting the chips.

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