CN110632713B - Device and method for rapidly coupling large-divergence-angle laser to single-mode fiber - Google Patents
Device and method for rapidly coupling large-divergence-angle laser to single-mode fiber Download PDFInfo
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- CN110632713B CN110632713B CN201910812083.7A CN201910812083A CN110632713B CN 110632713 B CN110632713 B CN 110632713B CN 201910812083 A CN201910812083 A CN 201910812083A CN 110632713 B CN110632713 B CN 110632713B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
- G02B6/4207—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms with optical elements reducing the sensitivity to optical feedback
- G02B6/4208—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms with optical elements reducing the sensitivity to optical feedback using non-reciprocal elements or birefringent plates, i.e. quasi-isolators
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
- G02B6/4214—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
- G02B6/422—Active alignment, i.e. moving the elements in response to the detected degree of coupling or position of the elements
- G02B6/4221—Active alignment, i.e. moving the elements in response to the detected degree of coupling or position of the elements involving a visual detection of the position of the elements, e.g. by using a microscope or a camera
- G02B6/4222—Active alignment, i.e. moving the elements in response to the detected degree of coupling or position of the elements involving a visual detection of the position of the elements, e.g. by using a microscope or a camera by observing back-reflected light
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4296—Coupling light guides with opto-electronic elements coupling with sources of high radiant energy, e.g. high power lasers, high temperature light sources
Abstract
The invention provides a device and a method for quickly coupling large-divergence-angle laser to a single-mode fiber, which have the advantages of simple structure, small volume and suitability for coupling of the large-divergence-angle laser. The invention comprises a laser chip, a collimating mirror, a beam splitter prism, a pyramid prism, an industrial camera, a coupling objective and an optical fiber circulator; the method for carrying out optical fiber coupling comprises the following steps: the method comprises the steps of lightening a laser chip, forming a reference light spot on an industrial camera through a beam splitter prism and a pyramid prism, lightening a fiber laser, enabling a laser beam emitted by the fiber laser to enter from a first port of a fiber circulator and then exit from a second port of the fiber circulator, enabling the laser beam to reach the beam splitter prism after passing through a coupling objective lens and a diaphragm, and imaging in the industrial camera after reflecting to form a coupling light spot; and finally, enabling the reference light spot and the coupling light spot in the image of the industrial camera to coincide, indicating that the laser chip (1) is aligned with the coupling end face of the single-mode fiber to be coupled, and completing coupling. The invention can be applied to the field of optical fibers.
Description
Technical Field
The invention relates to the field of optical fibers, in particular to a device for rapidly coupling large-divergence-angle laser to a single-mode optical fiber and a method for coupling the large-divergence-angle laser to the single-mode optical fiber by using the device.
Background
The optical fiber is a transmission channel of optical signals and is a key material for optical fiber communication. Two main characteristics of optical fibers are loss and dispersion. The loss is the attenuation or loss of an optical signal per unit length, expressed in db/km, which is related to the transmission distance of the optical signal, the greater the loss, the shorter the transmission distance. The dispersion of the fiber is primarily related to pulse broadening.
The transmission modes of light in the optical fiber can be classified into: single mode optical fibers and multimode optical fibers. The central glass core of the multimode Fiber (Multi Mode Fiber) is thicker (50 or 62.5 μm), and can transmit light of multiple modes. However, the intermodal dispersion is large, which limits the frequency of the transmitted digital signal and is more severe with increasing distance. For example: a600 MB/KM fiber has a bandwidth of only 300MB at 2 KM. Thus, multimode fibers are relatively close in transmission distance, typically only a few kilometers. The central glass core of a Single Mode Fiber (Single Mode Fiber) is thin (the core diameter is generally 9 or 10 μm), and can only transmit light of one Mode. Therefore, the dispersion between the modes is very small, and the optical fiber is suitable for remote communication, and because the single-mode optical fiber has good optical transmission characteristics and most optical devices are based on the single-mode optical fiber, the single-mode optical fiber is used in more and more scenes.
Optical fiber devices have important applications in free space optical communications, where coupling spatially light transmitted over long distances into single mode optical fibers is a precision project. In practical applications, coupling free space light emitted from a laser chip into an optical fiber is one of the most critical steps, the coupling efficiency determines the amount of energy at the output end of the optical fiber, and since the core diameter of a single-mode optical fiber is narrow, how to couple as much light emitted from the laser chip into the optical fiber as possible becomes a great difficulty.
The document with publication number CN 108663758A proposes a scheme of collimating laser light by using a collimator and coupling the laser light to a single-mode optical fiber, but the focal length of the collimator only reaches 5m, which results in that the size of the whole device is above 5m, the size is too large, and more of the devices are limited to experimental application, and it is difficult to realize large-scale and industrialization.
The lens coupling method is one of the most common methods for coupling free space light source and optical fiber. The lens generally includes a single spherical lens, an aspherical lens, a multi-lens system, etc., wherein the single spherical lens is simplest and easiest to manufacture, but the coupling efficiency of the single spherical lens is inferior to that of other lenses due to the existence of spherical aberration. Therefore, a coupled objective lens or an aspherical lens is commonly used at present. The efficiency of the coupling mode is much higher than that of the sleeve direct coupling mode, but the design requirement on the lens is higher, and an appropriate lens needs to be selected according to the characteristics of a laser chip light source and the characteristics of an optical fiber. The cylindrical lens coupling method is also a common method, and the principle structure of the cylindrical lens coupling method is similar to that of a single ball lens coupling method, and the coupling efficiency of the cylindrical lens coupling method mainly depends on the size of the lens, the distance between the lens and the laser chip, and the refractive index of the lens. The coupling efficiency can be increased by decreasing the radius of the lens, otherwise unchanged. However, in practical application, the positioning precision of the adjusting mechanism is high, and the adjusting mechanism is very sensitive to external vibration, so that the application of the adjusting mechanism is limited to a certain extent.
If the design requirement for the lens can be reduced, the stability of interaction between devices can be improved, and the induction to external vibration can be reduced, the lens coupling method can greatly save the volume, can also be applied to the field of industrial automation, and can also couple laser with a large divergence angle.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art, and provide a device for rapidly coupling the large-divergence-angle laser to the single-mode fiber, which has a simple structure and a small volume, and is suitable for coupling the large-divergence-angle laser, and a method for coupling the large-divergence-angle laser to the single-mode fiber by using the device.
The device for rapidly coupling the large-divergence-angle laser to the single-mode fiber adopts the technical scheme that: it comprises a laser chip to be coupled into an optical fiber and having a large divergence angle, and also comprises a collimating lens, a beam splitter prism, a coupling objective lens and an optical fiber circulator which are sequentially arranged on an optical axis of the laser chip, the front end of the coupling objective is provided with a diaphragm, the circulator comprises a first port, a second port and a third port, the first port is provided with a fiber laser chip, the second port is arranged at the focus of the coupling objective lens, the light emitting surface of the laser chip is arranged at the object focus of the collimating lens, the beam splitter prism is arranged on the emergent light path of the collimating lens, the coupling objective lens is arranged on the transmission light path of the beam splitter prism, and an industrial camera is arranged on the other side of the light splitting prism and positioned on the reflection light path of the pyramid prism.
The technical scheme shows that the laser chip emits laser, the laser is collimated by the collimating mirror and then becomes a parallel light beam parallel to the optical axis of the laser chip, the parallel light beam is divided into transmission light and reflection light by the beam splitter prism, the reflection light enters the pyramid prism after being reflected by the beam splitter prism, the reflection light returns according to the original path, and the reference light spot is formed after being transmitted by the beam splitter prism and imaged in the industrial camera; the light beam of another way transmission of beam splitter prism directly arrives and sets up on the coupling objective of distal end, reachs the port two of optic fibre circulator after the convergence of coupling objective, and most light will the coupling gets into optic fibre circulator, and follow the exit of the port three of optic fibre circulator is setting up in the back is lighted to the fiber laser of the port one of optic fibre circulator, and laser beam follows the port one couples into in the optic fibre circulator, follows again the exit of port two, through behind coupling objective and the diaphragm, reachs beam splitter prism and reflection arrive the industry camera forms the coupling facula in industry camera department, adjusts the coincidence of reference facula and coupling facula that finally forms in the industry camera to guarantee that the light emitting area of the port two of optic fibre circulator and laser chip is the counterpoint unanimity, the laser beam that laser chip sent can directly couple and get into the optic fibre circulator, connecting external optical fibers at three ports of the optical fiber circulator, namely realizing the rapid coupling of light beams from the laser chip to the optical fibers; in the process, the applied collimating lens, the beam splitter prism, the pyramid prism, the industrial camera, the coupling objective lens and the like are all conventional components, and additional customization is not needed, so that the cost is greatly saved; the debugging is simple, the weight and the volume of the element are small, the manual adjusting machine can be made, and the space is reserved for the automation of the whole equipment; compared with the collimator which is expensive and huge in size, the volume and the cost of the device are greatly reduced; the invention utilizes the beam splitting prism to lead out a beam of reference light as an evaluation standard in the middle process of debugging, the evaluation standard is used as a reference when in debugging, and the laser beam can be quickly judged to be coupled into the optical fiber as long as judging whether a coupling light spot formed by light emitted from a second port of the optical fiber circulator in a camera is superposed with the reference light spot or not; in addition, the arrangement of the collimating mirror can collimate the light beam emitted by the laser chip with a large divergence angle, and the collimated light can meet the requirements of transmission and reflection of the beam splitter prism, so that the follow-up laser coupling is guaranteed; the arrangement of the optical fiber circulator provides more stable conditions for the access of optical fibers, the optical fiber circulator can be used for quickly realizing optical fiber coupling, the stability of a light path is kept, and the reliability can be ensured even if components between a laser chip and the circulator are removed; the fiber laser emits light beams at one port of the fiber circulator, so that the intensity of the coupled light spots is greatly enhanced, and the influence of an external vibration source on the device is greatly reduced.
Furthermore, the first port is an input end of the second port, the third port is an output end of the second port, and an optical power probe connected with an optical power meter is arranged at the third port. Therefore, the optical power probes capable of detecting the optical power and the optical power meter capable of displaying the optical power in real time are arranged at the three positions of the port of the optical fiber circulator, when whether the light beam transmitted from the light splitting prism reaches the optimal state after being coupled to the optical fiber circulator or not is detected, the judgment can be rapidly carried out according to the display result of the optical power meter, when the optimal effect is achieved, the fact that all lasers are coupled into the optical fiber circulator is determined, and the efficiency is greatly improved.
Still further, the collimating lens is a non-spherical lens with a single-chip diffraction limit, and an antireflection film matched with the wavelength of the laser emitted by the laser chip is arranged on a light transmitting surface. Therefore, the aspheric lens is used as the collimating lens, and has a better curvature radius, so that good aberration correction can be maintained to obtain the required performance, and the aspheric lens can bring more excellent sharpness and higher resolution, and provide a better environment for the laser coupling optical fiber; the antireflection film further reduces the generation of stray light and avoids adverse effects on the coupling result.
Still further, the beam splitter prism is a beam splitter, and the reflection-transmission ratio R: T of the beam splitter prism is 10: 90-50: 50. Therefore, the beam splitter is used as a beam splitter prism, the requirements of generating reflected light and transmitted light can be met, and the beam splitter is used as a conventional optical lens, so that the cost is greatly reduced compared with the existing collimator with high price and huge size; the range of the reflection transmittance of the beam splitter can be selected, so that the coupling requirements of the laser with different wavelengths can be met.
Furthermore, an antireflection film matched with the wavelength of the laser emitted by the laser chip is arranged on the incident surface of the pyramid prism, and a matting paint is coated on the reflecting surface of the pyramid prism. Therefore, the arrangement of the antireflection film reduces the increase of stray light at the corner cube prism, and ensures the accuracy of reference light spots obtained by the industrial camera.
Still further, the coupling objective is an infinity objective, and the stop is integrally formed with the coupling objective. Therefore, the infinite objective lens is used as the coupling objective lens, so that the transmitted light of the beam splitter prism can be better focused, and the coupling effect of the optical fiber circulator is ensured.
More specifically, the reflection-transmission ratio R: T of the beam splitter prism is 10: 90. It follows that selecting a lower reflectance to transmittance can ensure the final coupling efficiency of the fiber.
In addition, the method for coupling laser to a single-mode optical fiber by using the device for rapidly coupling the large-divergence-angle laser to the single-mode optical fiber is realized on a five-axis adjusting platform, a linear guide rail is arranged on the five-axis adjusting platform, and a beam quality analyzer capable of moving along the linear guide rail is arranged on the linear guide rail, and the method comprises the following steps:
A. through the cooperation of the five-axis adjusting platform, the linear guide rail and the beam quality analyzer, the poses of the laser chip, the collimating mirror, the beam splitter prism, the pyramid prism, the industrial camera, the coupling objective lens and the optical fiber circulator are adjusted in place;
B. the laser chip is lightened, a laser beam emitted by the laser chip is collimated by the collimating mirror to form parallel light and is directly emitted to the beam splitter prism, the beam splitter prism splits incident light into transmitted light and reflected light, the transmitted light continuously passes through the diaphragm and the coupling objective lens and is finally coupled to a second port of the optical fiber circulator, and the reflected light split by the beam splitter prism is incident to the pyramid prism and is reflected by the pyramid prism to the industrial camera for imaging to form a reference light spot;
C. the optical fiber laser is lightened, a laser beam emitted by the optical fiber laser enters from a first port of the optical fiber circulator and then exits from a second port of the optical fiber circulator, the laser beam passes through the coupling objective lens and the diaphragm and then reaches the beam splitter prism, the laser beam is imaged in the industrial camera after being reflected, and a coupling light spot is formed on the industrial camera;
D. and adjusting the axial distance between the second port and the coupling objective lens to focus a corresponding light spot in the image of the industrial camera, and then adjusting the vertical axis XY position of the first port to enable a reference light spot and a coupling light spot in the image of the industrial camera to coincide, so that the coupling end face of the laser chip and the coupling end face of the single-mode optical fiber to be coupled are aligned and consistent, and the coupling is completed.
Therefore, the device is constructed by the conventional components such as the collimating lens, the beam splitter prism, the pyramid prism, the industrial camera, the coupling objective and the optical fiber circulator, compared with the existing scheme adopting the large-volume collimator, the device greatly reduces the cost and the volume, and is convenient for large-scale industrialization and automation; the light beam emitted by the optical fiber laser enters the optical fiber circulator from the first port and is emitted from the first port, the light beam passes through the coupling objective and the diaphragm and then reaches the beam splitter prism, and is finally reflected on the industrial camera to form a coupling light spot, the position and the posture of the optical fiber circulator are adjusted by judging the coincidence degree between the coupling light spot and the reference light spot, and finally the coupling light spot is completely coincided with the reference light spot, so that the light emitting surface of the laser chip is completely opposite to the second port of the optical fiber circulator and keeps the alignment consistency, and the complete coupling of the laser emitted by the laser chip to the optical fiber is realized, the method is simple to operate and effective, and through testing, all the laser can be coupled into the optical fiber, so that compared with the prior art, the method greatly saves the equipment cost, improves the coupling efficiency and reduces the equipment volume; after the optical fiber coupling is finished, equipment can be conveniently removed, energy loss caused by the existence of the coupling equipment can be avoided, and the coupling quality is ensured; in addition, the introduction of the optical fiber circulator ensures the stability of the whole device and can reduce the vibration sensitivity to the outside simultaneously.
Further, the method comprises the following steps:
E. the port I is an input end of the port II, the port III is an output end of the port II, an optical power probe connected with an optical power meter is arranged at the port III, the optical power probe arranged at the port III detects the light velocity intensity emitted from the port III of the optical fiber circulator, the optical power meter displays the optical power change of a light beam transmitted from the beam splitter prism and coupled into the optical fiber circulator in the process of adjusting the vertical axis XY position of the port I, and when a reference light spot and a coupling light spot in an industrial camera image are superposed and the optical efficiency displayed by the optical power meter is maximum, the best degree of laser coupling into the optical fiber circulator is determined.
According to the scheme, the optical power probe and the optical power meter are arranged, whether the light transmitted from the light splitting prism is coupled into the optical fiber circulator to the maximum extent or not can be judged quickly according to the display result of the optical power meter, when the optimal effect is achieved, the fact that all the laser is coupled into the optical fiber circulator is determined, and the efficiency is greatly improved.
Still further, the specific steps of step a are as follows:
a. adjusting the pose of the laser chip: fixing the lighted laser chip on the five-axis adjusting platform, aligning a laser spot to the beam quality analyzer, recording a spot image by using the beam quality analyzer, adjusting the inclination angle of the laser chip in the process of changing the distance between the laser chip and the beam quality analyzer, and finishing the pose adjustment of the laser chip when the XY position of the center of the laser spot is always kept at the same position on the image under the conditions of different working distances;
b. adjusting the pose of the collimating mirror: arranging the collimating mirror on a five-axis adjusting platform, adjusting the axial distance between the collimating mirror and the laser chip, pulling the beam quality analyzer from near to far until the sizes of the laser spots at different distances are the same, adjusting the vertical axis XY position of the collimating mirror, pulling the beam quality analyzer from near to far, and keeping the XY positions of the centers of the laser spots at different distances at the same position on the image, wherein the adjustment of the collimating mirror is completed;
c. adjusting the pose of the coupling objective lens: arranging the coupling objective lens on a five-axis adjusting platform, then adjusting the vertical axis XY position and the inclination angle of the coupling objective lens to enable a light beam to pass through the centers of the diaphragm and the coupling objective lens, pulling the light beam quality analyzer from near to far, and completing adjustment when the XY positions of the centers of laser spots at different distances are all kept at the same position on an image;
d. pose adjustment of the beam splitter prism and the industrial camera: arranging the pyramid prism at one side of the light splitting prism, aligning a reflecting surface of the light splitting prism with the pyramid prism, arranging an industrial camera at the other side of the light splitting prism, focusing a lens of the industrial camera to an infinite position, turning on the industrial camera to take a picture, adjusting the position of the pyramid prism, enabling the split beam reflected by the light splitting prism to be incident to the central position of the pyramid prism, and finishing the pose adjustment of the light splitting prism and the industrial camera;
e. and (3) optical fiber coupling adjustment: and arranging a second port of the optical fiber circulator at the focus of the coupling objective lens, connecting the optical fiber laser with the first port of the optical fiber circulator, lighting the optical fiber laser, and adjusting the axial distance between the second port and the coupling objective lens to focus a corresponding light spot in the image of the industrial camera, so as to finish light spot imaging of the laser beam incident from the first port on the industrial camera.
According to the scheme, the adjusting platform consisting of the five-axis adjusting platform, the linear guide rail and the light beam quality analyzer is established, and each component is optically adjusted based on the adjusting platform, so that the difficulty of setting the device is greatly simplified, the cost is reduced, the consistency of the device before and after setting is ensured, the condition of reworking is avoided, and the precision of the device is further ensured.
Drawings
FIG. 1 is a simplified schematic diagram of the laser chip pose adjustment;
FIG. 2 is a simplified schematic diagram of the collimator mirror pose adjustment;
FIG. 3 is a simplified schematic diagram of the coupled objective pose adjustment;
FIG. 4 is a simplified schematic diagram of the pose of the beam splitting prism, cube corner prism and industrial camera;
FIG. 5 is a schematic diagram of a simplified construction of the apparatus of the present invention;
FIG. 6 is a schematic diagram of a simplified construction of the fiber optic circulator;
fig. 7 is a simple structure diagram of the coincidence process of the coupling light spot and the reference light spot.
Detailed Description
The present invention is described in more detail below with reference to the accompanying drawings, as shown in fig. 1 to 7.
A laser chip 1 to be coupled into an optical fibre is shown in figure 1, the laser chip having a divergence angle of 2 theta, the dotted line representing the optical axis.
A linear guide rail 9 is arranged on the five-axis adjusting platform, and a beam quality analyzer 10 which can move along the linear guide rail 9 is arranged on the linear guide rail 9. Through the cooperation of the five-axis adjusting platform, the linear guide rail 9 and the beam quality analyzer 10, the poses of the laser chip 1, the collimating mirror 2, the beam splitter prism 3, the pyramid prism 4, the industrial camera 5, the coupling objective 6 and the optical fiber circulator 7 are adjusted in place. Specifically, the following operation is performed.
As shown in fig. 1, a laser chip 1 is fixed on a five-axis adjustment platform. The laser chip is lit, the beam quality analyzer 10 is then fixed to the mount of the linear guide 9, the light spot is aligned with the beam quality analyzer, and the beam quality analyzer records the image of the light spot. Adjusting the inclination angle of the laser chip in the process of changing the distance between the laser chip and the beam quality analyzer; and when the XY position of the center of the light spot is kept at the same position on the image under the condition of different working distances, finishing the inclination adjustment of the laser chip. As shown in fig. 2, a collimator lens 2 is added and then fixed on a three-axis adjustment stage. And adjusting the axial distance between the collimating mirror and the laser chip, and drawing the beam quality analyzer 10 from near to far so that the sizes of light spots at different distances are the same. And adjusting the XY position of the vertical axis of the collimating mirror, and pulling the beam quality analyzer from near to far so that the XY positions of the centers of the laser spots at different distances are all kept at the same position on the image, thereby completing the setting of the collimating mirror.
As shown in fig. 3, a coupling objective 6 is added and then fixed on a five-axis adjustment stage. And then adjusting the vertical axis XY position and the inclination angle of the objective lens to enable the light beam to pass through the center of the diaphragm of the coupling objective lens. The beam quality analyzer 10 is pulled from near to far, and when the XY positions of the laser spot centers at different distances are all kept at the same position on the image, the adjustment of the coupling objective lens is completed. As shown in fig. 4, the corner cube 4 and the beam splitter prism 3 are added, and 10% of the reflection surface is aligned with the corner cube. An industrial camera 5 is added, focusing the lens to infinity. And opening camera software to take a picture, and adjusting the position of the pyramid prism to enable 10% of the beam split light to be incident to the central position of the pyramid prism, so that the arrangement of the beam split prism, the pyramid prism and the industrial camera is completed.
As shown in fig. 5 and 6, a coupling objective 6, a fiber circulator 7 and a fiber laser 8 are added. The port 2 of the fiber circulator is placed at the coupling objective focal position, and then the fiber laser is connected to the fiber circulator port 1. And port 3 is an output port, add optical power probe 11 and optical power meter 12, connect the optical power probe and the optical power meter, and then align the optical power probe with fiber circulator port 3. And (3) lightening the fiber laser, and adjusting the axial distance between the port 2 of the fiber circulator and the coupling objective lens 6 to focus corresponding light spots in the image of the industrial camera. The vertical axis XY position of port 1 is then adjusted so that the reference and coupling spots in the image coincide as shown in figure 7.
As shown in fig. 5, in the present embodiment 1, a laser chip to be coupled into an optical fiber is defined to have a divergence angle of 2 θ. The laser chip is placed on the object focus of the collimating mirror 2, the focal length of the collimating mirror is f1, and after passing through the collimating mirror, the laser is collimated into parallel light. In order to reduce the wave aberration as much as possible, the collimating lens should be a single-chip diffraction-limited aspheric lens, which is often used to collimate the output light of an optical fiber or a laser diode, and the surfaces of the aspheric lens are designed to be aplanatic. The collimated laser is divided into two paths of light rays for transmission and reflection through the beam splitter prism 3. The reflection transmittance of the beam splitter prism can be R: T =10:90, R: T =30:70 and R: T =50:50, and the side length of the beam splitter prism can be 10mm, 15mm or 20 mm. And 4 is a corner cube prism which functions to return the same path as the incident light for a range of angles normal to the normal. In order to reduce stray light and protect the prism, the reflecting surface of the pyramid needs to be coated with a matting paint. The reflected light having passed through the beam splitter prism is reflected by the corner cube prism, and then reflected back on the original path, and received by the industrial camera 5. The light emitting area of the laser is S1, the size on the image plane of the camera is S2, S1/S2= f1/f2, wherein f2 is the focal length of the camera lens. The light ray is defined as reference light, and the formed light spot is the reference light spot. After passing through the beam splitter prism, the transmitted beam passes through a diaphragm at the front end of the microscope objective 6 and is focused by the coupling objective. The magnification of the coupling objective lens can be 10X, 20X and 50X, the magnification of the objective lens is related to the focal length, and the divergence angle and the light spot size of the coupling light need to be matched with the optical fiber. The clear aperture of the coupling objective lens is larger than or equal to the diameter of the collimated light beam; the working spectrum of the coupling objective lens is consistent and adaptive with the spectrum of the laser; the coupled objective lens should be an infinity objective lens. And 7, a fiber optic circulator which is a three-port device, and light can only propagate along one direction. As shown in fig. 6, if a signal is input from the first port 71, the signal is output from the second port 72; and the signal is input from the second port 72 and is output from the third port 73, and the output loss is small. When light is input from the second port 72, the loss is large when light is output from the first port 71, and when light is input from the third port 73, the loss is large when light is output from the first port and the second port. The fiber optic circulator is an irreversible optical device. The optical fiber circulator has the advantages of high isolation and low insertion loss. By placing port two 72 of the fiber optic circulator at the focus of the microscope objective, the beam will be coupled into the fiber and then out port three 73. And connecting the optical fiber laser with the first port 71 of the optical fiber circulator to light the optical fiber laser. Two light spots are seen on an industrial camera, one light spot is reflected by the laser chip 1 through a pyramid, the other light spot is emitted by the optical fiber laser 8, the size and the position of the light spot of a coupling light path can be seen to change by adjusting the three-dimensional position of the optical fiber, and when the coupling light spot is adjusted to be in a focusing state and the position of the coupling light spot is overlapped with the position of a reference light spot, the laser is coupled into the optical fiber. If not specifically stated, the working surfaces of all optical elements need to be plated with antireflection films corresponding to the laser wavelength, and the reflectivity is not more than 0.5%.
Compared with the prior art, the invention adopts the industrial lens and the industrial camera to construct the auto-collimation light path, and abandons the collimator with high price and huge size as the auto-collimation equipment. The diaphragm is added in front of the coupling objective lens, so that the coupled light is ensured to pass through the center of the objective lens and is matched with the numerical aperture of the optical fiber, and finally, the laser can be efficiently coupled into the optical fiber. And the optical fiber circulator is added, so that the optical fiber output optical power can be detected in real time in the adjusting process. Meanwhile, the problem of optical fiber end face position deviation caused by optical fiber disassembly after coupling is finished can be avoided. The coupling scheme is feasible and proved by experiments. The system has small size and can be integrated in industrial automation application.
Claims (10)
1. A device for fast coupling of a large divergence angle laser to a single mode fiber, comprising a laser chip (1) to be coupled into the fiber and having a large divergence angle, characterized in that: it still sets gradually on the optical axis of laser chip (1) collimating mirror (2), beam splitter prism (3), coupling objective (6) and optic fibre circulator (7) the front end of coupling objective (6) is provided with the diaphragm, circulator (7) including port one (71), port two (72) and port three (73), port one (71) is provided with fiber laser (8), port two (72) set up in the focus department of coupling objective (6), the light emitting area of laser chip (1) set up in the object side focus department of collimating mirror (2), beam splitter prism (3) set up on the emergent light path of collimating mirror (2), coupling objective (6) set up on the transmission light path of beam splitter prism (3) set up on the emergent light path of the reflected light of beam splitter prism (3) has angle cone prism (4), and an industrial camera (5) is also arranged on the other side of the light splitting prism (3) and on the reflection light path of the pyramid prism (4).
2. The apparatus of claim 1, wherein the optical fiber comprises: the first port (71) is an input end of the second port (72), the third port (73) is an output end of the second port (72), and an optical power probe (11) connected with an optical power meter (12) is arranged at the third port (73).
3. The apparatus of claim 2, wherein the optical fiber comprises: the collimating lens (2) is a non-spherical lens with a single-chip diffraction limit, and an antireflection film matched with the wavelength of the laser emitted by the laser chip (1) is arranged on a light transmitting surface.
4. The apparatus of claim 2, wherein the optical fiber comprises: the beam splitter prism (3) is a beam splitter, and the reflection-transmission ratio R: T of the beam splitter prism (3) ranges from 10:90 to 50: 50.
5. The apparatus of claim 2, wherein the optical fiber comprises: and an antireflection film matched with the wavelength of the laser emitted by the laser chip (1) is arranged on the incident surface of the pyramid prism (4).
6. The apparatus of claim 2, wherein the optical fiber comprises: the coupling objective lens (6) is an infinite objective lens, and the diaphragm and the coupling objective lens (6) are integrally formed.
7. The apparatus of claim 4, wherein the optical fiber comprises: the reflection-transmission ratio R: T of the light splitting prism (3) is 10: 90.
8. A method for coupling laser light to a single-mode optical fiber by using the apparatus for rapidly coupling a large-divergence-angle laser light to a single-mode optical fiber according to claim 1, the method being implemented on a five-axis adjusting platform, a linear guide rail (9) being provided on the five-axis adjusting platform, and a beam quality analyzer (10) being provided on the linear guide rail (9) and being movable along the linear guide rail (9), the method comprising the steps of:
A. the pose of the laser chip (1), the collimating mirror (2), the beam splitter prism (3), the pyramid prism (4), the industrial camera (5), the coupling objective lens (6) and the optical fiber circulator (7) is adjusted in place through the matching of the five-axis adjusting platform, the linear guide rail (9) and the beam quality analyzer (10);
B. the laser chip (1) is lightened, a laser beam emitted by the laser chip (1) is collimated by the collimating mirror (2) to form parallel light and is directly emitted to the light splitting prism (3), the light splitting prism (3) splits incident light into transmitted light and reflected light, the transmitted light continuously passes through the diaphragm and the coupling objective lens (6), and is finally coupled to a second port (72) of the optical fiber circulator (7), and the reflected light split by the light splitting prism (3) is reflected by the pyramid prism (4) to the industrial camera (5) to be imaged after being incident to the pyramid prism (4), so that a reference light spot is formed;
C. the optical fiber laser (8) is lightened, a laser beam emitted by the optical fiber laser (8) enters from a first port (71) of the optical fiber circulator (7), then exits from a second port (72) of the optical fiber circulator (7), passes through the coupling objective lens (6) and the diaphragm, reaches the beam splitting prism (3), is reflected and imaged in the industrial camera (5), and forms a coupling light spot on the industrial camera (5);
D. and adjusting the axial distance between the second port (72) and the coupling objective lens (6) to focus a corresponding light spot in the image of the industrial camera (5), and then adjusting the vertical axis XY position of the first port (71) to make a reference light spot and a coupling light spot in the image of the industrial camera coincide, so that the laser chip (1) is aligned with the coupling end face of the single-mode fiber to be coupled, and the coupling is completed.
9. The method of claim 8, further comprising the steps of:
E. the port one (71) is an input end of the port two (72), the port three (73) is an output end of the port two (72), an optical power probe (11) connected with an optical power meter (12) is arranged at the port three (73), the optical power probe (11) arranged at the port three (73) detects the light velocity intensity emitted from the port three (73) of the optical fiber circulator (7), displaying, by the optical power meter (12), an optical power change of a light beam transmitted from the beam splitting prism (3) and coupled into the fiber circulator (8) during adjustment of a vertical axis XY position of the port one (71), and when the reference light spot and the coupling light spot in the industrial camera image are superposed and the optical efficiency displayed by the optical power meter (12) is maximum, determining that the laser is coupled into the optical fiber circulator (8) to the best extent.
10. The method according to claim 8, wherein the step a comprises the following steps:
a. adjusting the pose of the laser chip: fixing the lighted laser chip (1) on the five-axis adjusting platform, aligning a laser spot to the beam quality analyzer (10), recording a spot image by using the beam quality analyzer (10), adjusting the inclination angle of the laser chip (1) in the process of changing the distance between the laser chip (1) and the beam quality analyzer (10), and finishing the pose adjustment of the laser chip (1) when the XY position of the center of the laser spot is always kept at the same position on the image under the conditions of different working distances;
b. adjusting the pose of the collimating mirror: arranging the collimating mirror (2) on a five-axis adjusting platform, adjusting the axial distance between the collimating mirror (2) and the laser chip (1), pulling the beam quality analyzer (10) from near to far until the sizes of light spots at different distances are the same, adjusting the XY position of the vertical axis of the collimating mirror (2), pulling the beam quality analyzer (10) from near to far, and keeping the XY positions of the centers of the laser light spots at different distances at the same position on an image, wherein at the moment, the collimating mirror is adjusted;
c. adjusting the pose of the coupling objective lens: arranging the coupling objective lens (6) on a five-axis adjusting platform, then adjusting the vertical axis XY position and the inclination angle of the coupling objective lens (6) to enable a light beam to pass through the centers of the diaphragm and the coupling objective lens, pulling the light beam quality analyzer (10) from near to far, and completing adjustment when the XY positions of the centers of laser spots at different distances are all kept at the same position on an image;
d. pose adjustment of the beam splitter prism and the industrial camera: arranging the pyramid prism (4) at one side of the light splitting prism (3), aligning the reflecting surface of the light splitting prism (3) with the pyramid prism (4), arranging an industrial camera (5) at the other side of the light splitting prism (3), focusing the lens of the industrial camera (5) to an infinite distance, opening the industrial camera (5) to take a picture, adjusting the position of the pyramid prism (4) to enable the split beam reflected by the light splitting prism (3) to be incident to the central position of the pyramid prism (4), and finishing the posture adjustment of the light splitting prism and the industrial camera (5);
e. and (3) optical fiber coupling adjustment: setting a second port (72) of the optical fiber circulator (7) at the focus of the coupling objective lens (6), connecting the optical fiber laser (8) with a first port (71) of the optical fiber circulator (7), lighting the optical fiber laser (8), and adjusting the axial distance between the second port (72) and the coupling objective lens (6) to focus a corresponding light spot in the image of the industrial camera (5), so as to finish the light spot imaging of the laser beam incident from the first port (71) on the industrial camera (5).
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| CN111308619B (en) * | 2020-01-20 | 2022-04-15 | 武汉联特科技股份有限公司 | Light emitting device and coupling method thereof |
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| CN114371534A (en) * | 2022-01-11 | 2022-04-19 | 成都光创联科技有限公司 | Collimating system coupling method |
| CN114690342A (en) * | 2022-03-30 | 2022-07-01 | Nano科技(北京)有限公司 | Surface parallelism adjusting system for coupling optical fiber array and silicon optical chip end face |
| CN114660741B (en) * | 2022-04-01 | 2023-04-28 | 中国科学技术大学 | Single-mode fiber automatic coupling method and system under large offset based on defocusing |
| CN114935828B (en) * | 2022-04-29 | 2023-04-11 | 中国科学院西安光学精密机械研究所 | Method for debugging focal plane of optical fiber coupling lens |
| CN115079346B (en) * | 2022-07-20 | 2022-11-29 | 之江实验室 | Installation and adjustment device and method for coupling space light to optical fiber |
| CN115267985B (en) * | 2022-08-10 | 2024-02-27 | 武汉联特科技股份有限公司 | Lens coupling collimation system and method |
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