Laser heating system adopting off-axis parabolic mirror

Abstract

The invention discloses a laser heating system adopting an off-axis parabolic reflector, which comprises a laser emitter, a beam expanding lens, a collimating lens and the off-axis parabolic reflector, and is characterized in that the beam expanding lens is arranged at the light path output end of the laser emitter and is used for expanding a laser beam, the collimating lens is arranged at the light path output end of the beam expanding lens, and the off-axis parabolic reflector is arranged on the collimating lens. The collimator is used for receiving the expanded light beams and collimating the light beams into parallel light beams; the off-axis parabolic mirror is used for receiving the parallel light beams and reflecting and focusing the parallel light beams to a single-crystal optical fiber heating area, a single-crystal optical fiber via hole vertically penetrates through the center of the reflecting surface of the off-axis parabolic mirror, and the single-crystal optical fiber via hole and the single-crystal optical fiber heating area are vertically opposite to each other. The off-axis parabolic reflector is adopted for focusing reflection, so that the optical path can be effectively shortened, the utilization rate of laser energy is improved, the structure is simple, all the devices are high in coaxiality and adjustability, the manufacturing cost is low, and by means of the heating system, the single crystal optical fiber can be effectively heated so as to achieve growth of the single crystal optical fiber.

Description

Technical Field

[0001] The present invention relates to the technical field of laser heating, and in particular to a laser heating system using an off-axis parabolic reflector. Background Art

[0002] Single-crystal optical fiber (SCFO) is an optical fiber made from a single crystal. It inherits the chemical and physical properties of single crystals while also offering the unique advantages of optical fiber, such as strong resistance to electromagnetic interference, excellent light transmission, compact size, and light weight. In recent years, with the rapid development of fiber optic sensing and fiber laser technologies, as well as continued advancements in single-crystal optical fiber fabrication techniques, the growth processes and application development of SCFOs based on various substrates have attracted increasing attention from industry researchers.

[0003] However, single-crystal optical fibers require relatively small crystal diameters, making traditional crystal growth methods inadequate. In contrast, laser heating offers significant advantages for crystal growth: it can form a smaller melt zone, achieve extremely high melt temperatures, and provide a large temperature gradient, facilitating the rapid growth of high-quality optical fibers. Its crucible-free growth method effectively avoids impurity contamination. Furthermore, its low material consumption and low power consumption significantly improve energy efficiency. Consequently, laser-heated crystal growth has gained widespread application in the preparation of single-crystal optical fibers.

[0004] Existing laser heating devices typically include a beam expander lens, a collimating lens, a beam-changing ring reflector, a folding mirror, and a focusing mirror. The beam expander lens and beam-changing ring reflector are mounted within a fixed cavity, and their coaxiality is completely dependent on the cavity's machining accuracy. This design can cause unpredictable optical path deviation or distortion during subsequent use if the device deforms, severely impacting laser focusing and heating efficiency, leading to poor single-crystal fiber growth quality. Existing focusing mirrors utilize an annular bowl-shaped design, which requires the use of a beam-changing ring reflector and a folding mirror to achieve beam focusing. This complex optical path layout not only significantly increases the optical path length but also significantly increases laser energy loss during transmission, reducing laser energy utilization. Furthermore, the addition of the beam-changing ring reflector and the folding mirror increases the number of optical path adjustment elements, making adjustment more complex and difficult. This not only increases equipment commissioning time and maintenance costs, but also potentially affects equipment stability and reliability. Furthermore, since the laser beam itself is invisible, adjusting the coaxiality of the various components is extremely difficult, a problem that existing devices do not address. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a laser heating system using an off-axis parabolic reflector to solve the problem that the optical path of the existing laser heating device is too long, resulting in low laser energy utilization.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A laser heating system using an off-axis parabolic reflector includes a laser emitter, a beam expander lens, a collimating lens and an off-axis parabolic reflector. The beam expander lens is installed at the optical path output end of the laser emitter to expand the laser beam. The collimating lens is arranged at the optical path output end of the beam expander lens to receive the expanded beam and collimate it into a parallel beam. The off-axis parabolic reflector is used to receive the parallel beam and reflect and focus it onto a single-crystal optical fiber heating area. A single-crystal optical fiber via hole is vertically penetrated through the center of the reflecting surface of the off-axis parabolic reflector. The single-crystal optical fiber via hole and the single-crystal optical fiber heating area are directly opposite each other.

[0007] Furthermore, the beam expander lens, the collimating lens and the off-axis parabolic reflector are mounted and fixed using the same cage frame, and the cage frame is used to ensure that the centers of the two lenses and the center of the off-axis parabolic reflector are on the same axis.

[0008] Furthermore, the system also includes a visible light emitter, a visible light reflector and a beam combining mirror, wherein the visible light reflector is used to reflect the visible light beam emitted by the visible light emitter; the beam combining mirror is arranged at the intersection of the output light path of the visible light reflector and the laser emitter, and is used to combine the visible light beam and the laser light beam into a coaxial light beam, and the beam expanding lens is installed on the light output path of the coaxial light beam, and is used to expand the coaxial light beam.

[0009] Furthermore, the system also includes an adjustable attenuation device, which is arranged between the beam combiner and the beam expander lens and is used to adjust the intensity of the light beam.

[0010] Furthermore, the laser emitter, adjustable attenuation device, beam expander lens, and collimating lens are all installed in a dustproof and sealed structure.

[0011] Furthermore, a vertically upward annealing device is coaxially arranged in the single crystal optical fiber through hole to slow down the temperature change of the single crystal optical fiber.

[0012] Furthermore, the off-axis parabolic reflector is arranged in a sealed cavity, and a window mirror is provided on a side of the sealed cavity facing the collimating lens, and the window mirror is located on the light output path of the collimating lens.

[0013] Furthermore, the system also includes a CCD diameter measuring device, which is arranged toward the single crystal optical fiber heating area and is used to monitor the diameter and melting zone morphology of the single crystal optical fiber.

[0014] Furthermore, a water cooling device is provided on the side of the off-axis parabolic reflector facing away from the collimating lens.

[0015] Furthermore, the surfaces of the beam expander lens and the collimator lens are coated with an infrared light anti-reflection film.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Compared with the traditional optical path, the laser heating system of the present invention adopts an off-axis parabolic reflector as a focusing reflector, which greatly reduces the number of light beam reflections, shortens the optical path, and improves the laser energy utilization rate.

[0017] 2. The present invention installs the beam expander lens, the collimating lens and the off-axis parabolic reflector in the same cage frame, which is highly adjustable and effectively ensures the coaxiality of the optical path, reduces the incidence of optical path distortion and the energy loss of the laser beam in the optical path; and by adjusting the distance between the two lenses, it can also ensure that the beam after expansion is the beam size required for ideal use, further enhancing the adjustability of the laser heating system.

[0018] 3. This invention combines a visible light beam and a laser beam onto a single optical axis. This allows operators to determine the laser's focusing efficiency based on the visible light's focusing effect, thereby controlling and adjusting the laser emitter. This visual integration of the optical path increases the accuracy of optical path adjustment and ensures effective single crystal heating. Furthermore, the off-axis parabolic reflector and cage mount used in this invention are both mature products, significantly reducing the cost of the laser heating system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a specific implementation method of a laser heating system using an off-axis parabolic reflector disclosed in the present invention; Explanation of the accompanying symbols: laser emitter 1, visible light emitter 2, visible light reflector 3, beam combiner 4, adjustable attenuation device 5, beam expander lens 6, collimating lens 7, off-axis parabolic reflector 8, annealing device 9, window mirror 10, CCD diameter measuring device 11, single crystal optical fiber 12. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention. Example

[0021] See also Figure 1The present invention provides a laser heating system using an off-axis parabolic reflector, comprising a laser emitter 1, a beam expander lens 6, a collimating lens 7 and an off-axis parabolic reflector 8. The beam expander lens 6 is installed at the optical path output end of the laser emitter 1 to expand the laser beam. The collimating lens 7 is arranged at the optical path output end of the beam expander lens 6 to receive the expanded beam and collimate it into a parallel beam; the off-axis parabolic reflector 8 is used to receive the parallel beam and reflect and focus it to the heating area of ​​the single crystal optical fiber 12. A single crystal optical fiber via hole is vertically penetrated through the center of the reflecting surface of the off-axis parabolic reflector 8, and the single crystal optical fiber via hole and the heating area of ​​the single crystal optical fiber 12 are directly opposite each other.

[0022] In practice, the beam expander lens 6, collimator lens 7, and off-axis parabolic reflector 8 are mounted and fixed using a cage mount. This cage mount ensures that the centers of the two lenses and the center of the off-axis parabolic reflector 8 are coaxial. Adjusting the cage mount ensures that the two lenses remain coaxial, thereby reducing the incidence of optical path distortion and energy loss in the laser beam, improving the stability of the laser heating system and the energy utilization of the laser. Furthermore, by adjusting the distance between the two lenses, the expanded beam can be maintained at the desired size, further increasing the adjustability of the laser heating system.

[0023] In a specific implementation, the system also includes a visible light emitter 2, a visible light reflector 3, and a beam combiner 4. The visible light reflector 3 is used to reflect the visible light beam emitted by the visible light emitter 2. The beam combiner 4 is disposed at the intersection of the visible light reflector 3 and the output optical path of the laser emitter 1, and is used to combine the visible light beam and the laser beam into a coaxial beam. The beam expander 6 is installed on the output optical path of the coaxial beam to expand the coaxial beam. In the present invention, the laser emitted by the laser emitter 1 is a high-power laser with a wavelength of 10.6μm, which is invisible to the naked eye. This structural arrangement can convert the invisible laser and visible light into a coaxial beam. By observing the beam path of the visible light, the beam path of the laser beam can be determined. This greatly improves the convenience of beam adjustment and the efficiency of device adjustment. In a specific implementation, the optical path can be adjusted to the appropriate position by turning on only the visible light emitter 2. Before formal growth, only the laser emitter 1 can be turned on to verify the completion of optical path adjustment by observing the focusing effect and the single crystal heating effect.

[0024] In practice, the system further includes an adjustable attenuation device 5, disposed between the beam combiner 4 and the beam expander 6, for adjusting the intensity of the beam. This allows the laser intensity to be adjusted to meet the growth requirements of different single-crystal optical fibers 12 while preventing the laser emitter 1 from operating at a power level other than the optimal level to meet the fiber growth requirements, thereby affecting the stability of the laser emitter 1.

[0025] In a specific implementation, a vertically upward annealing device 9 is coaxially disposed within the single-crystal fiber through-hole to slow down the temperature change of the single-crystal fiber 12. In the present invention, an off-axis parabolic reflector 8 is used as a focusing reflector. When the single-crystal fiber 12 grows, the temperature will drop significantly when it grows to a position above the melting zone. Since the single-crystal fiber 12 grows at a relatively fast rate, a rapid drop in temperature may cause cracks in the single-crystal fiber 12, affecting the performance of the fiber. The annealing device 9 is added to the central hole of the off-axis parabolic reflector 8 to slow down the temperature change of the single-crystal fiber 12 when it passes through the annealing device 9, thereby improving the growth quality of the single-crystal fiber 12.

[0026] In a specific implementation, the system also includes a CCD diameter measuring device 11, which is positioned toward the heating area of ​​the single-crystal fiber 12 and is used to monitor the diameter and melt zone morphology of the single-crystal fiber 12. This image recognition method is used to observe the growth status of the single-crystal fiber 12, allowing personnel to obtain data on the current growth of the single-crystal fiber 12, thereby facilitating adjustments to parameters such as laser power and growth rate.

[0027] In specific implementation, a water cooling device is provided on the side of the off-axis parabolic reflector 8 facing away from the lens. The water cooling device is a curved copper tube. Cooling water is passed into the copper tube to cool the off-axis parabolic reflector 8. Cooling the off-axis parabolic reflector 8 during laser heating can prevent the off-axis parabolic reflector 8 from being damaged by high temperature, thereby extending the service life of the off-axis parabolic reflector 8.

[0028] In specific implementation, the material of the lens is a material with high transmittance to infrared light, such as zinc selenide or germanium. The surface of the lens is also coated with an infrared light anti-reflection film through existing technology, so that the transmittance of infrared light with a wavelength of 10.6μm can exceed 99.5%.

[0029] In specific implementation, the base material of the off-axis parabolic reflector 8 is made of copper or fused quartz, and the surface of the off-axis parabolic reflector 8 is coated with a reflective film, which is generally made of gold material. The surface of the reflective film is also coated with a layer of oxide protective film, which can prevent the gold from being scratched and affecting the surface accuracy.

[0030] In a specific implementation, the off-axis parabolic reflector 8, annealing device 9, and single crystal optical fiber 12 are all disposed in a sealed cavity. A window mirror 10 is provided on the side of the sealed cavity facing the collimating lens 7. The window mirror 10 is located on the light output path of the collimating lens 7. An observation window is provided on the side of the sealed cavity facing the CCD diameter measuring device 11 to facilitate data acquisition by the CCD diameter measuring device 11. Since the growing optical fiber needs to pass through the off-axis parabolic reflector 8 and the annealing device 9, and different environmental atmospheres (such as vacuum or inert atmosphere) may be required when growing different optical fibers, a portion of the off-axis parabolic reflector 8 and the annealing device 9 are installed in a cage-type mirror frame and extend into the same sealed cavity to provide the different conditions required for optical fiber growth. In a specific implementation, the sealed cavity adopts a stainless steel sealed furnace, and the window mirror 10 is fixed to the flange window of the stainless steel sealed furnace.

[0031] In a specific implementation, the laser emitter 1, the adjustable attenuation device 5, the beam expander lens 6, the collimating lens 7, and the cage-type mirror frame for mounting the beam expander lens 6 and the collimating lens 7 are all mounted in a dustproof sealing structure. The dustproof sealing structure can be a vacuum-sealed cavity or a retractable bellows. When the dustproof sealing structure is a bellows, the laser emitter 1, the adjustable attenuation device 5, the mounting bracket of the beam expander lens 6, the mounting bracket of the collimating lens 7, and the sealed cavity are all provided with bellows mounting positions to facilitate the installation of the bellows. In a specific implementation, a section of bellows is provided between the laser emitter 1 and the adjustable attenuation device 5, between the adjustable attenuation device 5 and the mounting bracket of the beam expander lens 6, between the mounting bracket of the beam expander lens 6 and the mounting bracket of the collimating lens 7, and between the mounting bracket of the collimating lens 7 and the sealed cavity outside the off-axis parabolic reflector 8. When assembling the cage mount, fix one end of the two bellows to the mounting frame of the beam expander lens 6 and the mounting frame of the collimating lens 7 respectively. After the subsequent lenses and reflectors are installed and debugged, directly fix the other ends of the two bellows to the mounting frame of the collimating lens 7 and the sealing cavity respectively. This can achieve the sealing of the cage mount without affecting the coaxiality of the lenses and reflectors.

[0032] In practice, the laser emitter 1, visible light emitter 2, visible light reflector 3, beam combiner 4, and the portion of the cage mount housing the beam expander 6 and collimator 7 are all mounted on an optical platform. The position and orientation of each device are adjustable. The cage mount and associated brackets include a three-dimensionally adjustable frame, cage mount mounting posts, a horizontal displacement adjustment platform, a vertical displacement adjustment platform, and other components. Adjusting the cage mount and brackets is conventional and will not be detailed here. Mounting all of the aforementioned devices in the laser heating system on an optical platform significantly simplifies optical path adjustment.

[0033] Directions: During installation: Install the laser emitter 1 and visible light emitter 2 on an optical platform. Then, place the visible light reflector 3 on the light output path of the visible light emitter 2. Place the beam combiner 4 at the intersection of the visible light reflector 3 and the output path of the laser emitter 1. Use the beam combiner 4 to combine the visible light beam and the laser beam into a coaxial beam. (In actual applications, the visible light reflector 3 and the beam combiner 4 are usually fixed as an integrated beam combining device. It is only necessary to adjust the relative position of the laser emitter 1 and the visible light emitter 2, and then move the beam combining device to align with the light output paths of the two emitters to obtain a coaxial beam.) Then, place the adjustable attenuation device 5 and the cage mount in the light output path of the laser emitter 1, and install the beam expander lens 6, the collimating lens 7, and the off-axis parabolic reflector 8 on the cage mount in sequence along the light output direction of the laser. Adjust the cage mount so that the centers of the two lenses and the reflection center of the off-axis parabolic reflector 8 are on the same axis. Afterwards, the annealing device 9 is installed vertically upward in the through hole of the single crystal optical fiber 12, and the single crystal optical fiber 12 is placed right below the through hole of the single crystal optical fiber.

[0034] Verify the accuracy of the optical path: After the device is installed, turn on the visible light emitter 2 and observe whether a circular light spot appears in the heating area of ​​the single crystal optical fiber 12. If so, it proves that the optical path is installed and adjusted to the appropriate position. If not, the optical path needs to be readjusted until a circular light spot appears in the heating area of ​​the single crystal optical fiber 12. After the visible light path is adjusted, turn off the visible light emitter 2, turn on the laser emitter 1, and place a piece of paper in the heating area of ​​the single crystal optical fiber 12. Observe whether a circular mark is burned on the paper to verify whether the laser light path is adjusted in place. If a circular mark is burned on the paper, single crystal optical fiber growth can be carried out. If not, the positions of the laser emitter 1 and the visible light emitter 2 need to be fine-tuned until a circular mark is burned on the paper, and then optical fiber growth can begin.

[0035] Single-crystal fiber growth: Keep the visible light emitter off and turn on the laser emitter for heating. During the heating process, the upward conveying device at the bottom of the single-crystal fiber 12 slowly transports the single-crystal fiber 12 upward at a constant speed. The top of the single-crystal fiber 12 is slowly pulled upward by the seed crystal and passes through the single-crystal fiber via. After slow cooling in the annealing device 9, the single-crystal fiber 12 of the desired size is obtained. During the heating process of the single-crystal fiber 12, the diameter and melt zone morphology of the single-crystal fiber 12 can also be monitored by the CCD diameter measuring device 11. This allows personnel to obtain current single-crystal fiber 12 growth data and timely adjust parameters such as laser power and growth rate.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described with reference to the preferred embodiments of the present application, those skilled in the art should understand that various changes can be made in form and details without departing from the spirit and scope of the present application as defined in the appended claims.

Claims

1. A laser heating system using an off-axis parabolic reflector, characterized in that: It includes a laser emitter, a beam expander lens, a collimating lens and an off-axis parabolic reflector. The beam expander lens is installed at the optical path output end of the laser emitter to expand the laser beam. The collimating lens is arranged at the optical path output end of the beam expander lens to receive the expanded beam and collimate it into a parallel beam; the off-axis parabolic reflector is used to receive the parallel beam and reflect and focus it to the single crystal fiber heating area. The center of the reflecting surface of the off-axis parabolic reflector is vertically penetrated by a single crystal fiber via hole, and the single crystal fiber via hole and the single crystal fiber heating area are directly opposite each other.

2. The laser heating system according to claim 1, characterized in that: The beam expander lens, collimating lens and off-axis parabolic reflector are installed and fixed using the same cage-type mirror frame, and the cage-type mirror frame is used to ensure that the centers of the two lenses and the center of the off-axis parabolic reflector are on the same axis.

3. The laser heating system according to claim 1, characterized in that: The system also includes a visible light emitter, a visible light reflector and a beam combining mirror. The visible light reflector is used to reflect the visible light beam emitted by the visible light emitter; the beam combining mirror is arranged at the intersection of the output light path of the visible light reflector and the laser emitter, and is used to combine the visible light beam and the laser beam into a coaxial light beam. The beam expanding lens is installed on the light output path of the coaxial light beam, and is used to expand the coaxial light beam.

4. The laser heating system according to claim 3, characterized in that: The system further comprises an adjustable attenuation device, which is arranged between the beam combiner and the beam expander lens and is used to adjust the intensity of the light beam.

5. The laser heating system according to claim 4, characterized in that: The laser emitter, the adjustable attenuation device, the beam expanding lens and the collimating lens are all installed in a dustproof sealing structure.

6. The laser heating system according to claim 1, characterized in that: A vertically upward annealing device is coaxially arranged in the single crystal optical fiber through hole to slow down the temperature change of the single crystal optical fiber.

7. The laser heating system according to claim 1, characterized in that: The off-axis parabolic reflector is arranged in a sealed cavity. A window mirror is arranged on the side of the sealed cavity facing the collimating lens. The window mirror is located on the light output path of the collimating lens.

8. The laser heating system according to claim 1, characterized in that: The system further comprises a CCD diameter measuring device, which is arranged toward the single crystal optical fiber heating area and is used to monitor the diameter and melting zone morphology of the single crystal optical fiber.

9. The laser heating system according to claim 1, characterized in that: A water cooling device is provided on the side of the off-axis parabolic reflector facing away from the collimating lens.

10. The laser heating system according to claim 1, characterized in that: The surfaces of the beam expanding lens and the collimating lens are coated with infrared light anti-reflection films.

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