A high temperature bonding method applied to erbium glass and cobalt spinel

Abstract

The application discloses a high-temperature bonding method applied to erbium glass and cobalt spinel, which comprises the following steps: polishing the erbium glass and the cobalt spinel respectively, then photo-cementing the two to form a photo-cement body, and performing high-temperature bonding sintering after confirming that there is no defect. The application realizes the molecular level combination between two different materials, realizes the fusion bonding of the gain medium and the Q crystal, reduces the interface loss, and can effectively reduce the packaging process and the packaging volume of the laser.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser crystal bonding, and relates to a high-temperature bonding method applied to erbium glass and cobalt spinel. BACKGROUND

[0002] Human eye safety laser can be used in laser ranging, laser irradiation, laser radar, target recognition, laser medical treatment and fiber communication and other fields, especially in the fields of laser ranging and laser radar, the product update and popularization speed are very rapid. At present, with the progress of laser technology, the laser is smaller and stronger, so that the laser range finder is used more and more in the national defense market and is used more and more widely. Now it has been expanded from a single soldier handheld observation instrument to a single soldier gun sighting equipment, a ground gun shooting command system, a target optical tracking instrument, a theodolite, and a ranging instrument for shipborne, airborne, tank and vehicle gun systems.

[0003] In order to realize miniaturization, higher requirements are put forward for the packaging structure of laser components, which is changed from the original separated packaging structure to bonded integrated packaging, so the bonding technology route of erbium glass and cobalt spinel is a new challenge. Erbium glass and spinel are both high-temperature diffusion bonding raw materials; in a laser system, erbium glass is used as a gain medium to realize laser conversion, and spinel is used as a passive Q-switch to adjust the laser pulse width and energy.

[0004] In the field of laser crystal bonding technology, there are deepening photo adhesive bonding technology, low-temperature bonding technology, high-temperature bonding technology and surface activation bonding technology, and different bonding technologies are suitable for different crystal bonding. Deepening photo adhesive bonding technology needs to be bonded after forming an antireflection film on the bonding surface by evaporating a bonding layer, the process is complex, and there is laser loss on the bonding surface, which is easy to cause laser damage, and is not conducive to the long-term use stability of the laser. Although the low-temperature bonding technology does not need to apply a bonding agent to the bonding surface, the bonding surface is not firm enough after bonding, and cracking is easy to occur, which is also not conducive to the long-term use stability of the laser. In the field of high-temperature bonding technology, especially in the bonding of cobalt spinel and erbium glass and silicate glass, the main technical defects are the poor interface firmness between these materials and the easy laser damage at the interface. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned defects, and to provide a high-temperature bonding method applied to erbium glass and cobalt spinel, which is a bonding method without bonding agent on the bonding surface, can improve the bonding strength of the bonding surface and reduce the interface loss, and improve the damage threshold of the bonding surface. The present application is suitable for the crystal bonding of erbium glass and cobalt spinel with a surface area of less than 10*10mm.

[0006] The technical scheme of the present application is as follows: a high-temperature bonding method applied to erbium glass and cobalt spinel, having the following steps:

[0007] 1) preparing erbium glass and cobalt spinel as gain medium and Q crystal;

[0008] 2) polishing the gain medium in 1) to achieve a surface roughness Ra<0.3 nm and a surface profile better than λ / 10;

[0009] 3) polishing the Q crystal in 1) to achieve a surface roughness Ra<0.4 nm and a surface profile better than λ / 10;

[0010] 4) removing polishing residues from the polished products of steps 2) and 3), and then wiping and forming an optical cement in an ultra-clean room to obtain an optical cement body;

[0011] 5) checking the optical cement body in 4) for air bubbles or impurity particles on the optical cement surface after optical cementing, and performing high-temperature bonding sintering after confirming no defects;

[0012] 6) placing the optical cement body in 5) on a ceramic plate, and then placing the ceramic plate into a constant-temperature sintering furnace, wherein the constant-temperature sintering furnace adopts a vacuum atmosphere, and the ceramic plate is an alumina ceramic plate;

[0013] 7) slowly heating the constant-temperature sintering furnace in 6) from room temperature to 200℃ at a rate of 35-45℃ / h, and keeping the temperature constant for 5h; and then slowly heating to 520-540℃ at a rate of 20-25℃ / h, and keeping the temperature constant for 30h;

[0014] 8) slowly cooling the constant-temperature sintering furnace in 7) from the highest temperature to room temperature at a rate of 20-25℃ / h;

[0015] 9) taking out the bonded crystal in the constant-temperature sintering furnace in 8). Dust-free gloves are worn when taking out the crystal.

[0016] In the present application, the erbium glass is Er and Yb co-doped phosphate or silicate glass, and the Q crystal is Co-doped spinel.

[0017] In the present application, the surface size of the gain medium and the Q crystal is 10×10 mm or less.

[0018] In the present application, the gain medium and the Q crystal are polished by using super-smooth surface polishing technology.

[0019] In the present application, the polished products in step 4) are cleaned by ultrasonic cleaning to remove polishing residues.

[0020] In step 4), the surface inspection of the photocolloid needs to be performed under a 100x optical microscope. The diameter of bubbles or impurity particles must be less than 1 μm. Excessive size or number of defects will affect the bonding strength or laser performance. There should be no obvious interference fringes at the edge (the presence of interference fringes indicates that the photocolloid was unsuccessful), and the bonded surfaces are prone to detachment during or after bonding.

[0021] In step 6), the constant temperature sintering furnace adopts a vacuum atmosphere, with a vacuum degree of <1×10⁻⁶. -3 The temperature is increased when Pa.

[0022] After the bonded crystal described in step 9) is removed, it is tested, including bonding strength tensile testing and cutting testing. After the tests, the end face is polished, followed by interface loss testing. After the interface loss test, the crystal is coated, and post-coating light emission energy and laser stability are tested.

[0023] This invention employs ultra-smooth polishing technology to polish erbium glass and spinel, achieving a surface roughness of Ra<0.5nm, which is significantly improved compared to traditional polishing. The optical index—surface profile—is better than 1 / 10λ, exceeding the standard for optical adhesives in general optical devices. Furthermore, the invention improves the cleaning effect of polishing residues on the product surface by using ultrasonic cleaning with different solvents after optical polishing through ultrasonic cleaning with different solvents.

[0024] The high-temperature sintering process used in this invention limits the heating and cooling rates, the isothermal time, and the maximum temperature setting. Setting the heating and cooling rates can prevent the crystal and glass from cracking due to excessive heating, and prevent the photoresist surface from separating or deforming due to uneven stress caused by excessive heating. Setting the isothermal time provides sufficient time for bonding to complete the interface bonding. Setting the maximum temperature can prevent the glass from melting due to overheating.

[0025] The innovative aspects of this invention are as follows:

[0026] 1. Finding the optimal bonding temperature to achieve the best bonding strength between the Q crystal and the gain medium. This invention experimentally analyzed the consistent melting point of the two materials; through different maximum temperature experimental conditions, it explored the highest temperature range suitable for bonding. Within the range of 520℃-540℃, a micro-melting state can be achieved on the surface of the erbium glass. Bonding under this state easily achieves the best bonding surface, and the bonding strength is significantly higher than that of low-temperature bonding. However, bonding at higher temperatures is prone to melting of the erbium glass or silicate glass at the bonding surface, resulting in a decrease in the bonding interface strength and the appearance of molten pit defects.

[0027] 2. Two dissimilar materials with significantly different melting points are bonded together using high-temperature thermal diffusion technology;

[0028] 3. This invention employs an ultra-smooth polishing process for cobalt spinel; ultra-smooth polishing can significantly reduce surface defects and increase the surface damage threshold after bonding.

[0029] This invention also relates to an ultrasonic cleaning process for erbium glass and cobalt spinel; polishing residue is also a major factor affecting interface loss and interface damage threshold. Ultrasonic cleaning can remove polishing residue after polishing, while traditional optical wiping methods cannot remove deep polishing residue.

[0030] This invention utilizes ultra-smooth polishing technology, binder-free photopolymerization technology, and a vacuum atmosphere isothermal sintering furnace. Through temperature rise and fall control and isothermal time control, it enhances the bonding force at the bonding interface, reduces interface loss, and increases the interface damage threshold, while simultaneously reducing the packaging difficulty of laser devices. This invention achieves a technological breakthrough by employing high-temperature bonding technology at the consistent melting points of the gain medium and the Q crystal, enabling high-temperature bonding between the gain medium and the Q crystal, thus enhancing interface robustness, reducing interface loss, and increasing the interface damage threshold. Attached Figure Description

[0031] Figure 1 These are front and side views of the polished 10×10×2mm erbium glass, the gain medium of this invention.

[0032] Figure 2 These are schematic diagrams of the front and side views of the polished Q crystal 10×10×2mm spinel product of this invention.

[0033] Figure 3 This is a schematic diagram of a 10×10×4mm photocolloid sample of the present invention;

[0034] Figure 4 This is a schematic diagram showing the relative positions of the photocolloids on the alumina ceramic plate.

[0035] Figure 5 This is a schematic diagram showing the relative positions of the photocolloid and the alumina ceramic plate in a constant-temperature sintering furnace. Detailed Implementation

[0036] Example 1

[0037] The erbium glass and cobalt spinel are bonded at high temperature according to the following steps:

[0038] 1) Prepare erbium glass and cobalt spinel with a surface size of 10×10mm as the gain medium and Q crystal; the erbium glass is Er and Yb co-doped phosphate glass;

[0039] 2) The gain medium described in 1) is polished using an ultra-smooth surface polishing technique to achieve a surface roughness Ra < 0.3 nm and a surface profile better than λ / 10; for exampleFigure 1 ;

[0040] 3) Polish the Q crystal described in 1) using ultra-smooth surface polishing technology to achieve a surface roughness Ra < 0.4 nm and a surface profile better than λ / 10; for example Figure 2 ;

[0041] 4) After ultrasonically cleaning to remove polishing residue from the polished products from steps 2) and 3), wipe them in a cleanroom and form a photocolloid using a photopolymer adhesive, such as... Figure 3 The two materials are tightly bonded together; the surface of the photocolloid is examined under a 100x optical microscope, and the diameter of bubbles or impurity particles must be less than 1μm.

[0042] 5) After the photocolloid described in 4) is photocoated, check the surface of the photocolloid for bubbles or impurity particles. After confirming that there are no defects, proceed with the high-temperature bonding and sintering process.

[0043] 6) Place the photocolloid described in 5) vertically on the alumina ceramic plate, without tilting it, such as... Figure 4 Then the ceramic plate is placed in a constant temperature sintering furnace, such as... Figure 5 The constant temperature sintering furnace adopts a vacuum atmosphere;

[0044] 7) Slowly raise the temperature of the isothermal sintering furnace described in 6) from room temperature to 200℃ at a rate of 40℃ / h, and hold the temperature for 5 hours; then slowly raise the temperature to 520℃ at a rate of 20℃ / h, and hold the temperature for 30 hours; the isothermal furnace should be kept at a vacuum level of <1×10 -3 Heat up when Pa is reached;

[0045] 8) Slowly cool the constant temperature sintering furnace described in 7) from the highest temperature to room temperature at a rate of 20℃ / h;

[0046] 9) Remove the bonded crystal from the constant temperature sintering furnace described in 8), wearing clean gloves when removing the crystal.

[0047] 10) After the bonded crystal is removed, it is tested, including bond strength tensile test and cutting test.

[0048] 11) After the test, perform end-face polishing, followed by interface loss testing. After the interface loss test, perform crystal coating, and then perform post-coating light output energy testing and laser stability testing.

[0049] Performance testing of bonded products:

[0050] 1. Interface durability test

[0051] 1) Tensile test: Tensile test was performed using a tensile testing instrument. A suitable fixture was made to fix the two end faces of the crystal, and axial tensile force and transverse shear stress tensile force tests were conducted. The experimental result of the axial tensile force test was 20 kg / cm². 2 The lateral tensile test result was 12 kg / cm. 2 ;

[0052] 2) Strength test method 2: The strength is verified by the inner circle cutting destructive test. A 1.5×1.5 cross section square strip is selected and the cross section is observed to see if there is any cracking or separation. Then, a temperature cycling test is carried out. The test results show that the strength can reach the point where the crystal does not show any abnormalities after cutting and temperature cycling.

[0053] 2. Loss Test

[0054] Interface scanning was performed using a weak absorption tester. The experimental results showed that the weak absorption at the cross-section was 300 ppm, which met the laser cross-sectional loss condition and the absorption was less than that of the film layer.

[0055] 3. Light emission energy test

[0056] The light output energy test is a test of the laser energy index of the packaged laser. The light output energy will be different for different crystal parameters.

[0057] Test results show that crystals bonded using the method of this invention have high interface strength, low interface consumption, and a high interface damage threshold.

[0058] This invention achieves bonding between erbium glass and cobalt spinel. This is accomplished through precision polishing and photoresist application, followed by a technological process to achieve molecular-level bonding between the two different materials. This invention also relates to a technique for bonding low-melting-point and high-melting-point crystals. This invention investigates the consistent melting point of the gain medium and the Q crystal, employing high-temperature bonding technology to achieve a technological breakthrough, enhancing interface strength, reducing interface loss, and increasing the interface damage threshold.

[0059] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0060] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0061] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A high-temperature bonding method for erbium glass and cobalt spinel, characterized in that, The bonding method comprises the following steps: 1) Prepare erbium glass and cobalt spinel as gain media and Q crystal; 2) Polish the gain medium described in 1) to achieve a surface roughness Ra < 0.3 nm and a surface profile better than λ / 10; 3) Polish the Q crystal described in 1) to achieve a surface roughness Ra < 0.4 nm and a surface shape better than λ / 10; 4) After removing polishing residue from the polishing products of steps 2) and 3), wipe them in the cleanroom to form a photocolloid. 5) After the photocolloid described in 4) is photocoated, check the surface of the photocolloid for bubbles or impurity particles. After confirming that there are no defects, perform the following high-temperature bonding and sintering. 6) Place the photocolloid described in 5) on a ceramic plate and place it in a constant temperature sintering furnace, wherein the constant temperature sintering furnace adopts a vacuum atmosphere; 7) Slowly raise the temperature of the constant temperature sintering furnace described in 6) from room temperature to 200℃ at a rate of 35-45℃ / h and hold it at that temperature for 5h; then slowly raise the temperature to 520-540℃ at a rate of 20-25℃ / h and hold it at that temperature for 30h. 8) Slowly cool the constant temperature sintering furnace described in 7) from the highest temperature to room temperature at a rate of 20-25℃ / h; 9) Remove the bonded crystal from the isothermal sintering furnace described in 8).

2. The high-temperature bonding method for erbium glass and cobalt spinel according to claim 1, characterized in that, The erbium glass is an Er and Yb co-doped phosphate or silicate glass; the Q crystal is a Co-doped spinel.

3. The high-temperature bonding method for erbium glass and cobalt spinel according to claim 1, characterized in that, The surface dimensions of the gain medium and the Q crystal are 10×10 mm or less.

4. The high-temperature bonding method for erbium glass and cobalt spinel according to claim 1, characterized in that, The gain medium and Q crystal are polished using an ultra-smooth surface polishing technique.

5. The high-temperature bonding method for erbium glass and cobalt spinel according to claim 1, characterized in that, The polished product in step 4) is ultrasonically cleaned to remove polishing residue.

6. The high-temperature bonding method for erbium glass and cobalt spinel according to claim 1, characterized in that, The surface of the photocolloid in step 4) is examined under a 100x optical microscope, and the diameter of bubbles or impurity particles must be less than 1μm.

7. The high-temperature bonding method for erbium glass and cobalt spinel according to claim 1, characterized in that, After the bonded crystal described in step 9) is removed, the test in step 10) is performed. The test includes bond strength tensile test and cutting test.

8. The high-temperature bonding method for erbium glass and cobalt spinel according to claim 1, characterized in that, After the test in step 10) is completed, the end face is polished and then the interface loss test is performed. After the interface loss test is completed, crystal coating is performed, and then optical energy test and laser stability test are performed.

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