CN115663576A - Optical fiber mode purification method and system - Google Patents
Optical fiber mode purification method and system Download PDFInfo
- Publication number
- CN115663576A CN115663576A CN202211301427.6A CN202211301427A CN115663576A CN 115663576 A CN115663576 A CN 115663576A CN 202211301427 A CN202211301427 A CN 202211301427A CN 115663576 A CN115663576 A CN 115663576A
- Authority
- CN
- China
- Prior art keywords
- mode
- order mode
- module
- fiber
- optical fiber
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000013307 optical fiber Substances 0.000 title claims abstract description 155
- 238000000034 method Methods 0.000 title claims abstract description 51
- 238000000746 purification Methods 0.000 title claims abstract description 39
- 239000000835 fiber Substances 0.000 claims abstract description 119
- 230000008878 coupling Effects 0.000 claims abstract description 26
- 238000010168 coupling process Methods 0.000 claims abstract description 26
- 238000005859 coupling reaction Methods 0.000 claims abstract description 26
- 238000005253 cladding Methods 0.000 claims description 36
- 238000006243 chemical reaction Methods 0.000 claims description 28
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 19
- 230000005540 biological transmission Effects 0.000 claims description 16
- 239000011247 coating layer Substances 0.000 claims description 13
- 239000005350 fused silica glass Substances 0.000 claims description 12
- 238000007493 shaping process Methods 0.000 claims description 12
- 239000010453 quartz Substances 0.000 claims description 5
- 230000004927 fusion Effects 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 3
- 239000012510 hollow fiber Substances 0.000 claims description 3
- 238000011282 treatment Methods 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 claims 2
- 238000000576 coating method Methods 0.000 claims 2
- 238000001914 filtration Methods 0.000 description 18
- 230000008569 process Effects 0.000 description 11
- 230000006872 improvement Effects 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 8
- 238000005452 bending Methods 0.000 description 8
- 238000003466 welding Methods 0.000 description 8
- 239000002699 waste material Substances 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 230000009022 nonlinear effect Effects 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 230000003685 thermal hair damage Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 238000005202 decontamination Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000003588 decontaminative effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000021715 photosynthesis, light harvesting Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Abstract
The invention provides a method and a system for purifying an optical fiber mode, wherein the method comprises the steps of stripping, collecting and reconverting a high-order mode in an optical fiber into a fundamental mode, coupling the fundamental mode obtained by converting the high-order mode with the fundamental mode originally existing in the optical fiber and then outputting the coupled fundamental mode to obtain output laser with high beam quality and high power; the system comprises an optical fiber input module, a high-order mode stripping module, an optical fiber beam combining module and a laser output module which are sequentially connected, wherein the high-order mode collecting module is connected to a position away from the signal input end of the high-order mode stripping module by a preset distance, the output end of the high-order mode collecting module is provided with a high-order mode converting module, and the output end of the high-order mode converting module is connected to the optical fiber beam combining module. The invention filters the high-order mode in the fiber laser, collects and converts the high-order mode into the basic mode for output, recycles the high-order mode, optimizes the beam quality, realizes the mode purification and simultaneously improves the output power of the laser.
Description
Technical Field
The invention relates to the technical field of fiber laser, in particular to a fiber mode purification method and a system thereof.
Background
In recent years, the output power of a high-power narrow-linewidth fiber laser is greatly improved under the promotion of the development of technologies such as a pumping source, a large-mode-field doped fiber, a fiber device, coherent synthesis, spectrum synthesis and the like. In order to suppress the nonlinear effect and raise the threshold of Stimulated Brillouin Scattering (SBS), an optical fiber having a large mode field area is widely used. However, the optical fiber with a large mode field area not only supports transmission of a fundamental mode, but also supports transmission of a high-order mode, and when the laser power reaches a threshold, a mode instability effect is caused, further improvement of the power is limited, and the beam quality of the output laser is reduced, thereby affecting the brightness and subsequent applications of the output laser. Therefore, optimizing the beam quality of the output laser is a great trend.
At present, in order to improve the beam quality of the output laser, the main method is to filter the high-order mode to achieve the purpose of purifying the transmission mode in the high-power narrow-linewidth fiber laser, thereby improving the beam quality. Two typical methods for filtering out higher order modes are available: one is to set the fiber in a bent state (bend mode selection), the bending loss of the high-order mode is generally larger than that of the fundamental mode, and the purpose of filtering the high-order mode is achieved after the fiber transmits enough distance by designing a proper bending radius. The patent with application number CN202011595385.2 discloses a signal light high-order mode filtering method, a high-order mode filtering amplification optical path and a laser, wherein the signal light high-order mode filtering method is to wind a passive optical fiber into a curved shape, so that the passive optical fiber filters a high-order mode in the signal light to obtain a fundamental mode signal light, and transmits the fundamental mode signal light to a gain optical fiber. However, the bending of the optical fiber also causes loss of the fundamental mode to a certain extent, and reduces the power of the output laser, and the sensitivity of the optical fibers with different numerical apertures to bending is very different, so that different laser systems need to be designed with different bending radii and optical fiber lengths to efficiently filter the high-order mode, which complicates the design, integration and mass production of the laser, and is not suitable for mass production.
The other method is to adopt a cladding light stripper (CPS) to destroy the waveguide structure of the cladding, strip the pump light and the high-order mode in the cladding of the optical fiber, convert the pump light and the high-order mode into heat energy, and then dissipate the heat energy through air or water cooling. Firstly, the method can only strip the high-order mode in the fiber cladding, and can not filter the high-order mode still transmitted in the fiber core of the optical fiber; secondly, the currently commonly used cladding stripper converts the stripped high-order mode into heat energy for dissipation, which not only causes waste of the high-order mode and reduces the output power of the laser, but also adds complicated heat energy management work and may cause heat damage to the laser.
Therefore, the quality of the light beam of the output laser is improved mainly by filtering the high-order mode at present, so that the high-order mode is directly lost to influence the power of the output laser, and the existing high-order mode filtering method has more or less defects to further influence the quality and the power of the light beam.
Accordingly, there is a need for an improved fiber mode cleaning method and system to solve the above problems.
Disclosure of Invention
The invention aims to provide an optical fiber mode purification method and an optical fiber mode purification system, wherein the method collects and converts a high-order mode in optical fiber laser into a fundamental mode for output while stripping the high-order mode, so that the high-order mode is recycled, the output power of the laser is improved while optimizing the beam quality and realizing mode purification, the waste of the high-order mode power caused by the traditional high-order mode filtering process and the thermal damage of heat generated in the filtering process to components are avoided, no additional thermal management operation is needed, and the reliability of the laser is improved.
In order to achieve the purpose, the invention provides an optical fiber mode purification method, which comprises the steps of stripping, collecting and converting a high-order mode in an optical fiber into a fundamental mode, coupling the fundamental mode obtained by converting the high-order mode with the fundamental mode originally existing in the optical fiber and then outputting the coupled fundamental mode to obtain output laser with high beam quality and high power;
the optical fiber mode purification method is realized by adopting an optical fiber mode purification system, the optical fiber mode purification system comprises an optical fiber input module, a high-order mode stripping module, an optical fiber beam combining module and a laser output module which are sequentially connected, a high-order mode collection module is connected at a preset distance away from a signal input end of the high-order mode stripping module, a high-order mode conversion module is arranged at an output end of the high-order mode collection module, and an output end of the high-order mode conversion module is connected to the optical fiber beam combining module; after laser generated by the optical fiber input module is filtered by the high-order mode stripping module, the original basic mode in the laser continues to be transmitted forwards, the high-order mode in the laser is stripped by the high-order mode stripping module, collected by the high-order mode collecting module and converted into the basic mode by the high-order mode converting module, and the basic mode obtained by conversion of the high-order mode and the original basic mode in the optical fiber are coupled into a beam of laser in the optical fiber beam combining module and output from the laser output module.
As a further improvement of the present invention, the high-order mode stripping module is one of an antiresonant hollow-core fiber and a cladding high-order mode filter, and the high-order mode stripping module leaks the high-order mode in the laser output by the fiber input module to the outside of the fiber core to filter the high-order mode.
As a further improvement of the present invention, the high-order mode collection module and the high-order mode conversion module respectively perform specific processing on two ends of the same segment to realize few-mode optical fibers with different functions; the high-order mode collection module is an optical fiber coupler prepared by stripping a coating layer of the few-mode optical fiber; the high-order mode conversion module is a few-mode long-period fiber grating, and the specific parameters of the few-mode long-period fiber grating are adjusted to meet the phase matching condition, so that the high-order mode collected by the high-order mode collection module is converted into the fundamental mode again.
As a further improvement of the present invention, the antiresonant hollow-core fiber includes a first hollow-core fiber with a coating layer removed and a second hollow-core fiber without a coating layer removed; the first hollow-core optical fiber comprises an air fiber core, an inner quartz capillary cladding and an outer fused quartz cladding which are sequentially arranged from inside to outside, and the high-order mode in the air fiber core is leaked to the outer fused quartz cladding to be filtered by utilizing the characteristic that the anti-resonance hollow-core optical fiber has large high-order mode loss.
As a further improvement of the present invention, the input end of the high-order mode collection module is connected to a position away from the input end of the first hollow-core optical fiber by a preset distance, and the high-order mode leaked into the outer fused silica cladding layer is coupled and collected into the core of the few-mode optical fiber of the high-order mode collection module by means of the action of an evanescent field for transmission.
As a further improvement of the invention, the length of the first hollow-core optical fiber is 10-50cm; the high-order mode collection module is connected to a position 5-40cm away from the port of the signal input end of the first hollow-core optical fiber, and the input end of the high-order mode collection module is connected to a position away from the input end of the first hollow-core optical fiber by a certain distance, so that high-order modes in laser can be completely stripped.
As a further improvement of the invention, the etched high-order mode filter of the cladding high-order mode filter destroys the total reflection transmission condition by the etched part of the cladding to leak the high-order mode, thereby realizing the filtering of the high-order mode.
As a further improvement of the present invention, the fiber input module and the high-order mode stripping module are connected by fusion or spatial coupling, so as to realize transmission of laser from the fiber input module to the high-order mode stripping module, further strip the high-order mode in the fiber core by the high-order mode stripping module, and keep the fundamental mode in the fiber core to continue to be transmitted forward.
As a further improvement of the present invention, a shaping coupling lens is disposed between the fiber input module and the high-order mode stripping module, and is configured to transmit a signal in the fiber input module to the high-order mode stripping module by means of spatial coupling.
In order to achieve the above object, the present invention further provides an optical fiber mode purification system, which is used for implementing any one of the above optical fiber mode purification methods, and the optical fiber mode purification system includes an optical fiber input module, a high-order mode stripping module, an optical fiber beam combining module, and a laser output module, which are connected in sequence, wherein the high-order mode collection module is connected at a preset distance from a signal input end of the high-order mode stripping module, a high-order mode conversion module is arranged at an output end of the high-order mode collection module, and an output end of the high-order mode conversion module is connected to the optical fiber beam combining module.
The invention has the beneficial effects that:
(1) The optical fiber mode purification method provided by the invention is characterized in that a high-order mode in the optical fiber is stripped, collected and converted into a fundamental mode, then the fundamental mode converted from the high-order mode is coupled with the fundamental mode originally existing in the optical fiber and then output, and output laser with high beam quality and high power is obtained. The method and the device have the advantages that the high-order mode in the fiber laser is removed, simultaneously, the high-order mode is collected and converted into the basic mode for output again, the high-order mode is recycled, the output power of the laser is improved while the beam quality is optimized and the mode purification is realized, the waste of the high-order mode power caused by the traditional high-order mode filtering process and the thermal damage of the heat generated in the filtering process to the component are avoided, the additional thermal management operation is not needed, and meanwhile, the reliability of the laser is improved.
(2) According to the optical fiber mode purification system provided by the invention, the high-order mode stripping module is utilized to strip the high-order mode, and compared with the traditional mode of bending mode selection and filtering the high-order mode, the high-order mode stripping module does not increase the design difficulty of a laser system due to bending mode selection in the high-order mode filtering process, and simultaneously does not lose the fundamental mode transmitted in a fiber core; the method has the advantages that the high-order mode is converted into the fundamental mode for recycling while the fundamental mode is not lost, the waste of the power of the high-order mode is avoided, the power of output laser is improved while mode purification is realized, and a new idea is provided for preparing the output laser with high beam quality and high power.
In addition, the preferable anti-resonance hollow-core optical fiber has important application value for inhibiting the nonlinear effect in the high-power narrow-linewidth optical fiber laser, long-distance transmission of the low nonlinear effect of the high-power narrow-linewidth optical fiber laser can be realized by prolonging the length of the anti-resonance hollow-core optical fiber, and the application scene of the high-power narrow-linewidth optical fiber laser can be further expanded.
(3) The optical fiber mode purification system provided by the invention can replace a cladding light stripper (CPS) to be used as a tail fiber output integrated device in a laser system, and the stripped high-order mode is collected and reused to be converted into a basic mode again for output, so that no power waste and heat loss are generated, the beam quality is optimized, and the high efficiency of the laser is kept.
Drawings
FIG. 1 is a flow chart of a fiber mode decontamination method of the present invention.
FIG. 2 is a schematic diagram of a fiber mode decontamination system of the present invention.
Figure 3 is a schematic cross-sectional view of the first hollow-core fiber of figure 2.
Reference numerals
1-an optical fiber input module; 2-a high order mode stripping module; 3-a fiber beam combining module; 4-a laser output module; 5-a high order mode collection module; 6-a high-order mode conversion module; 7-a shaping coupling lens; 211-air core; 212-inner quartz capillary cladding; 213-outer fused silica cladding.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the aspects of the present invention are shown in the drawings, and other details not closely related to the present invention are omitted.
In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Referring to fig. 1, the present invention provides a method for purifying a fiber mode, which comprises stripping, collecting and converting a high-order mode in a fiber into a fundamental mode, coupling the fundamental mode converted from the high-order mode with the fundamental mode originally existing in the fiber, and outputting the coupled fundamental mode to obtain an output laser with high beam quality and high power. By the operation, the high-order mode in the fiber laser is filtered, collected and converted into the basic mode for output, so that the high-order mode is recycled, the beam quality is optimized, and the mode purification is realized; the output power of the laser is improved; meanwhile, the generation of heat energy in the traditional high-order mode filtering process is avoided, additional heat management operation is not needed, heat damage to components is avoided, and the reliability of the laser is improved.
Referring to fig. 2, the present invention further provides an optical fiber mode purification system for implementing the optical fiber mode purification method, including an optical fiber input module 1, a high order mode stripping module 2, an optical fiber beam combining module 3, and a laser output module 4, which are connected in sequence, wherein a high order mode collection module 5 is connected to a position (the distance is freely set according to the type of the high order mode stripping module 2) away from the signal input end of the high order mode stripping module 2, and meanwhile, a high order mode conversion module 6 is arranged at the output end of the high order mode collection module 5, and the output end of the high order mode conversion module 6 is connected to the input end of the optical fiber beam combining module 3. In this way, after the laser generated by the optical fiber input module 1 is filtered by the high-order mode stripping module 2, the original fundamental mode in the laser is continuously transmitted forwards, the high-order mode in the laser is stripped by the high-order mode stripping module 2 and then enters the high-order mode collecting module 5 for collection, and the high-order mode collected by the high-order mode collecting module 5 is converted into the fundamental mode by the high-order mode converting module 6 and then enters the optical fiber beam combining module 3; then, the fundamental mode obtained by the high-order mode conversion and the fundamental mode originally existing in the optical fiber are coupled into a beam of laser in the optical fiber beam combining module 3, and the beam is output through the laser output module 4 to obtain the output laser with high beam quality and high power.
The optical fiber input module 1 is an input optical fiber (solid core optical fiber), the diameter of a fiber core of the input optical fiber is 20-50 mu m, and the input optical fiber can be a common large-mode field passive optical fiber in a high-power narrow-linewidth optical fiber laser amplifier. Specifically, the input fiber is a tail fiber of a large mode field passive fiber commonly used in a fiber laser amplifier.
The optical fiber input module 1 is coupled into the high-order mode stripping module 2 through welding or spatial coupling (realized through lens transformation), the high-order mode stripping module 2 strips the high-order mode in the fiber core, and the forward transmission of the fundamental mode in the fiber core is kept. In actual work, the optical fiber input module 1 and the high-order mode stripping module 2 can be coupled and connected in a fusion welding or lens conversion mode according to different requirements.
The high-order mode stripping module 2 may have various options in order to achieve stripping of the high-order modes from the core into the cladding of the fiber. Specifically, the high-order mode stripping module 2 comprises one of an anti-resonant hollow fiber and a cladding high-order mode filter, wherein one end of the high-order mode stripping module 2, which is close to the fiber input module 1, is a first fiber part with a coating layer stripped, and the other end, which is far away from the fiber input module 1, is a second fiber part without the coating layer stripped; the high-order mode collection module 5 is connected to a position away from the signal input end port of the first optical fiber part by a preset distance. The high-order mode collection module 5 is disposed at different positions of the first optical fiber portion depending on the high-order mode stripping module 2 used. By such arrangement, the high-order mode in the fiber input module 1 can be completely stripped and collected.
Specifically, when the anti-resonance hollow-core optical fiber is selected as the high-order mode stripping module 2, the transmission loss of a high-order mode in a fiber core of the anti-resonance hollow-core optical fiber is simulated through numerical simulation software, the length of a first optical fiber part is set according to the loss value, the high-order mode is completely stripped and collected, and the length of the first optical fiber part is 10-50cm; the high-order mode collection module 5 is connected to a position 5-40cm away from the signal input end port of the first optical fiber part. When the high-order mode stripping module 2 selects a cladding high-order mode filter (i.e. a cladding etched high-order mode filter), the high-order mode collecting module 5 is arranged at the etched part of the cladding of the first optical fiber part, so that heat energy dissipation is reduced.
The high-order mode stripping module 2 is preferably an anti-resonant hollow-core fiber. The anti-resonant hollow-core fiber has a first hollow-core fiber 21 (i.e., a bare fiber portion) with a coating layer stripped at one end close to the fiber input module 1, and a second hollow-core fiber 22 without a coating layer stripped at the other end far away from the fiber input module 1. As shown in fig. 3, the first hollow-core optical fiber 21 includes an air core 211, an inner silica capillary cladding 212, and an outer fused silica cladding 213, which are arranged in this order from the inside to the outside. By utilizing the characteristic that the anti-resonance hollow-core fiber has large high-order mode loss, the high-order mode in the air fiber core 211 is leaked into the outer fused silica cladding 213 to realize the filtering of the high-order mode.
The high-order mode collection module 5 and the high-order mode conversion module 6 are a section of few-mode optical fiber with two ends respectively processed differently to realize different functions. Specifically, the high-order mode collection module 5 is an optical fiber coupler prepared by removing a coating layer of a few-mode optical fiber, the input end of the high-order mode collection module 5 is connected with the first hollow-core optical fiber 21, and high-order modes leaked into a cladding of the first hollow-core optical fiber 21 are coupled and collected by the action of an evanescent field in a fiber core of the at least-mode optical fiber for transmission.
The high-order mode conversion module 6 is a prepared few-mode long-period fiber grating, specific parameters of the long-period fiber grating are adjusted to meet phase matching conditions, the high-order modes collected by the high-order mode collection module 5 can be converted into fundamental modes again and transmitted, and the high-order modes are prevented from being converted into heat energy to be dissipated.
The fundamental mode (fundamental mode converted from the high-order mode) transmitted by the high-order mode conversion module 6 and the fundamental mode (fundamental mode originally existing in the laser) transmitted by the second hollow-core fiber 22 simultaneously enter the fiber beam combining module 3 to be combined to obtain the laser only with the fundamental mode and output the laser, and then enter the laser output module 4 to finally obtain the output laser output with high beam quality and high power.
The optical fiber beam combining module 3 is a beam combiner made of two optical fibers and made into 2 multiplied by 1.
The laser output module 4 is a collimating end cap and is used for realizing collimating output of laser.
The output end of the second hollow-core fiber 22 and the output end of the high-order mode conversion module 6 are fused with the laser output module 4 by using carbon dioxide laser after fusion tapering (i.e. two fibers are made into a similar 2 × 1 beam combiner for beam combining). Specifically, as shown in fig. 2, the output end of the second hollow-core optical fiber 22 is a coated hollow-core optical fiber, and the specific structure is different from that of the first hollow-core optical fiber 21; the output end of the high-order mode conversion module 6 is a few-mode optical fiber with a coating layer stripped. The cutting angle of the end faces of the two optical fibers is less than 0.5 degrees in the carbon dioxide laser welding process, the end faces of the optical fibers on two sides are clean, the proper discharge power and the proper overlapping degree are adjusted, and the phenomena of collapse deformation of the anti-resonance hollow optical fiber microstructure and insufficient welding strength are avoided. After welding, the mechanical strength of the welding points should be checked and the welding loss should be detected, so that the welding loss is less than 10%.
The working principle of the optical fiber mode purification system is as follows:
example 1
The utility model provides a fiber mode clean system, is including fiber input module 1, high order mode stripping module 2, optic fibre that connect gradually restraints module 3 and laser output module 4, and the distance department is preset apart from high order mode stripping module 2 signal input end and is connected with high order mode collection module 5, and the output of high order mode collection module 5 is provided with high order mode conversion module 6 simultaneously, and the output of high order mode conversion module 6 is connected to the input that fiber closed restraints module 3.
Specifically, the optical fiber input module 1 is an input optical fiber with the model number of PLMA-GDF-25/400. As shown in fig. 2, in the present embodiment, the laser output end of the input fiber is provided with a spherical structure to realize the light-gathering collimation function. The spherical structure is formed by heating and melting the output end of the input optical fiber to be spherical. The method specifically comprises the following steps: an ultrasonic cleaner and alcohol are used for cleaning an input optical fiber, a proper ball burning program is selected, and carbon dioxide laser is continuously used for heating the output end of the optical fiber to enable the output end of the optical fiber to be melted into a ball shape. The spot size of the collimated laser output by the input optical fiber is measured by adopting a 90%/10% knife edge method, and the collimated laser with the spot radius of about 0.98mm is obtained by taking an average value through multiple measurements.
The high-order mode stripping module 2 is an anti-resonance hollow-core optical fiber. The end of the antiresonant hollow-core fiber close to the fiber input module 1 is a first hollow-core fiber 21 (i.e. a bare fiber) with a coating layer stripped, and the end far away from the fiber input module 1 is a second hollow-core fiber 22 without a coating layer stripped. The input end of the high-order mode collection module 5 is connected to a position 10cm away from the signal input end port of the first hollow-core optical fiber 21, and the length of the first hollow-core optical fiber 21 is 20cm.
In this embodiment, to avoid bending losses, the antiresonant hollow-core fiber is coiled into a loose circle with a radius greater than 25cm and placed on the optical bench. By adopting a full vector finite element method and using numerical simulation software, the geometric structure parameters of the anti-resonance hollow-core fiber are designed from the angle of inhibiting the high-order mode in the fiber core to realize single-mode transmission, so that the high-order mode transmitted in the air fiber core 211 is matched with the cladding mode in the inner quartz capillary cladding 212 to realize phase matching, the loss of the high-order mode in the fiber core is caused, and the high-order mode is leaked into the outer fused quartz cladding 213.
Based on this statement and the principle of guiding light of the antiresonant hollow-core fiber (i.e., antiresonant reflective optical waveguide principle), the specific parameters of the first hollow-core fiber 21 shown in fig. 3 are as follows: the number of the inner quartz capillary tube cladding 212 is 7, the capillary tube wall thickness t is 405nm, the capillary tube diameter D is 14 μm, the diameter D of the air fiber core 211 is 23 μm, the length of the whole anti-resonance hollow fiber is 5-20m, and the coiling radius of the fiber is larger than 25cm. By the formula
Calculate anti-resonance hollow coreThe effective mode field area of the fiber, and thus the effective mode field radius of the fiber was 8.6 μm.
Wherein, A eff The effective mode field area is obtained by calculation;
f (x, y) is the mode field distribution of a fundamental mode transmitted in the anti-resonance hollow-core optical fiber and is obtained through simulation of numerical simulation software;
in this embodiment, the optical fiber input module 1 is coupled into the high-order mode stripping module 2 in a space coupling manner, and specifically, a shaping coupling lens 7 is disposed between the optical fiber input module 1 and the high-order mode stripping module 2. The shaping coupling lens 7 couples the collimated laser output by the optical fiber input module 1 into the high-order mode stripping module 2 for transmission so as to strip the high-order mode.
The focal length of the shaping coupling lens 7 is calculated and selected according to the spatial coupling principle of the thin lens for Gaussian beam transformation, and is determined by the size of a collimated laser spot output by the input optical fiber. The calculation formula of the focal length of the shaping coupling lens 7 is approximate to
Wherein F is the focal length of the shaping coupling lens 7;
omega is the radius of a collimated laser spot output by the optical fiber input module 1 and is obtained by measurement;
λ is the central wavelength of the transmitted laser, and is a known value;
ω′ 0 the effective mode field radius of the anti-resonant hollow-core fiber is obtained by calculation.
The shaping coupling lens 7 is made of fused quartz, and an antireflection film is plated on the surface of the lens. The thermally induced focal length offset of the fused quartz lens is 0.015 mm/DEG C, so that the lens deformation caused by the thermal effect caused by high-power laser can be effectively reduced, and the influence of the thermal effect on the coupling efficiency is effectively reduced.
Placing the incident end face of the first hollow-core optical fiber 21 at the focal length of the shaping coupling lens 7 obtained by calculation, so that the focused light spot is coupled into the first hollow-core optical fiber 21; the positions and angles of the spherical output end of the optical fiber input module 1 (input optical fiber), the shaping coupling lens 7 and the incident end of the first hollow optical fiber 21 are adjusted to ensure that the central axes of the spherical output end, the shaping coupling lens 7 and the incident end of the first hollow optical fiber 21 are overlapped, and the highest coupling efficiency is achieved after adjustment.
The high-order mode collection module 5 and the high-order mode conversion module 6 are a section of few-mode optical fiber with two ends respectively subjected to different treatments and different functions. Specifically, the high-order mode collection module 5 is an optical fiber coupler prepared by stripping a coating layer from a few-mode optical fiber.
The high-order mode conversion module 6 is a prepared few-mode long-period fiber grating, realizes the coupling of a 1-micron wave band fundamental mode and a high-order mode, and realizes the conversion from the high-order mode to the fundamental mode; the carbon dioxide laser spot writing technology is adopted, and the proper period length, the period number, the writing power and the like are designed and adjusted.
In summary, according to the optical fiber mode purification method and the system thereof provided by the present invention, the high-order mode in the optical fiber laser is filtered, and simultaneously collected and converted into the fundamental mode for output, so that the high-order mode is recycled, the beam quality is optimized, the mode purification is realized, and simultaneously the output power of the laser is improved, the waste of the high-order mode power caused by the conventional high-order mode filtering process and the thermal damage of the heat generated in the filtering process to the component are avoided, no additional thermal management operation is required, and simultaneously the reliability of the laser is improved, thereby providing a new idea for preparing the output laser with high beam quality and high power.
Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.
Claims (10)
1. A fiber mode purification method is characterized in that a high-order mode in an optical fiber is stripped, collected and converted into a fundamental mode, then the fundamental mode converted from the high-order mode is coupled with the fundamental mode originally existing in the optical fiber and then output, and output laser with high beam quality and high power is obtained;
the optical fiber mode purification method is realized by adopting an optical fiber mode purification system, the optical fiber mode purification system comprises an optical fiber input module, a high-order mode stripping module, an optical fiber beam combining module and a laser output module which are sequentially connected, a high-order mode collection module is connected at a preset distance away from a signal input end of the high-order mode stripping module, a high-order mode conversion module is arranged at an output end of the high-order mode collection module, and an output end of the high-order mode conversion module is connected to the optical fiber beam combining module; after the laser generated by the optical fiber input module is filtered by the high-order mode stripping module, the original basic mode in the laser is continuously transmitted forwards, the high-order mode in the laser is stripped by the high-order mode stripping module, collected by the high-order mode collecting module and converted into the basic mode by the high-order mode converting module, and the basic mode converted by the high-order mode and the original basic mode in the optical fiber are coupled into a beam of laser in the optical fiber beam combining module and output from the laser output module.
2. The fiber mode purification method according to claim 1, wherein the high-order mode stripping module is one of an antiresonant hollow fiber and a cladding high-order mode filter, and the high-order mode stripping module leaks the high-order mode in the laser output by the fiber input module to the outside of the fiber core to filter the high-order mode.
3. The optical fiber mode purification method according to claim 1, wherein the high-order mode collection module and the high-order mode conversion module are respectively subjected to specific treatment at two ends of the same section so as to realize few-mode optical fibers with different functions; the high-order mode collection module is an optical fiber coupler prepared by stripping a coating layer of the few-mode optical fiber; the high-order mode conversion module is a few-mode long-period fiber grating, and the specific parameters of the few-mode long-period fiber grating are adjusted to meet the phase matching condition, so that the high-order mode collected by the high-order mode collection module is converted into the fundamental mode again.
4. The fiber mode purification method of claim 2, wherein the antiresonant hollow-core fiber comprises a first hollow-core fiber with a coating removed and a second hollow-core fiber without a coating removed; the first hollow-core optical fiber comprises an air fiber core, an inner quartz capillary cladding and an outer fused silica cladding which are sequentially arranged from inside to outside, and the high-order mode in the air fiber core is leaked into the outer fused silica cladding to filter the high-order mode by utilizing the characteristic that the anti-resonance hollow-core optical fiber has large high-order mode loss.
5. The fiber mode cleaning method according to claim 4, wherein the input end of the high-order mode collection module is connected at a predetermined distance from the input end of the first hollow-core fiber, and the high-order mode leaked into the outer fused silica cladding is collected by evanescent field coupling into the core of the few-mode fiber of the high-order mode collection module for transmission.
6. The fiber mode purification method of claim 5, wherein the length of the first hollow-core fiber is 10-50cm; the high-order mode collection module is connected to a position 5-40cm away from the port of the signal input end of the first hollow-core optical fiber, and the input end of the high-order mode collection module is connected to a position away from the input end of the first hollow-core optical fiber by a certain distance, so that high-order modes in laser can be completely stripped.
7. The fiber mode purification method of claim 2, wherein the cladding high order mode filter comprises a cladding etched high order mode filter, wherein the high order mode filter is configured to filter the high order mode by breaking a total reflection transmission condition at the cladding etched portion.
8. The fiber mode purification method according to claim 1, wherein the fiber input module and the high-order mode stripping module are connected by fusion or spatial coupling to realize transmission of laser from the fiber input module to the high-order mode stripping module, so that the high-order mode in the fiber core is stripped by the high-order mode stripping module, and the forward transmission of the fundamental mode in the fiber core is kept.
9. The fiber mode purification method according to claim 8, wherein a shaping coupling lens is disposed between the fiber input module and the high-order mode stripping module, and is configured to transmit the signal in the fiber input module to the high-order mode stripping module by spatial coupling.
10. An optical fiber mode purification system for implementing the optical fiber mode purification method according to any one of claims 1 to 9, wherein the optical fiber mode purification system comprises an optical fiber input module, a high-order mode stripping module, an optical fiber beam combining module and a laser output module which are connected in sequence, the high-order mode collection module is connected at a preset distance from the signal input end of the high-order mode stripping module, the output end of the high-order mode collection module is provided with a high-order mode conversion module, and the output end of the high-order mode conversion module is connected to the optical fiber beam combining module.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211301427.6A CN115663576A (en) | 2022-10-24 | 2022-10-24 | Optical fiber mode purification method and system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211301427.6A CN115663576A (en) | 2022-10-24 | 2022-10-24 | Optical fiber mode purification method and system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115663576A true CN115663576A (en) | 2023-01-31 |
Family
ID=84990911
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211301427.6A Pending CN115663576A (en) | 2022-10-24 | 2022-10-24 | Optical fiber mode purification method and system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115663576A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116154593A (en) * | 2023-04-19 | 2023-05-23 | 武汉中科锐择光电科技有限公司 | Device, system and method for realizing mode self-cleaning of multimode optical fiber amplifier |
| CN116774346A (en) * | 2023-08-25 | 2023-09-19 | 中国航天三江集团有限公司 | Method and system for designing optical fiber cladding for inhibiting mode instability in optical fiber amplifier |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111596403A (en) * | 2020-05-08 | 2020-08-28 | 武汉锐科光纤激光技术股份有限公司 | Optical fiber device and method for manufacturing the same |
| CN111856646A (en) * | 2020-08-04 | 2020-10-30 | 中国人民解放军国防科技大学 | High-order mode filter |
-
2022
- 2022-10-24 CN CN202211301427.6A patent/CN115663576A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111596403A (en) * | 2020-05-08 | 2020-08-28 | 武汉锐科光纤激光技术股份有限公司 | Optical fiber device and method for manufacturing the same |
| CN111856646A (en) * | 2020-08-04 | 2020-10-30 | 中国人民解放军国防科技大学 | High-order mode filter |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116154593A (en) * | 2023-04-19 | 2023-05-23 | 武汉中科锐择光电科技有限公司 | Device, system and method for realizing mode self-cleaning of multimode optical fiber amplifier |
| CN116774346A (en) * | 2023-08-25 | 2023-09-19 | 中国航天三江集团有限公司 | Method and system for designing optical fiber cladding for inhibiting mode instability in optical fiber amplifier |
| CN116774346B (en) * | 2023-08-25 | 2023-11-21 | 中国航天三江集团有限公司 | Method and system for designing optical fiber cladding for inhibiting mode instability in optical fiber amplifier |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN115663576A (en) | Optical fiber mode purification method and system | |
| CN103229370B (en) | Fiber laser | |
| US4265699A (en) | Etching of optical fibers | |
| CN103490273A (en) | High-power optical fiber transmission system | |
| EP3104202B1 (en) | Structure for eliminating escaping light, and fiber laser | |
| CN210296855U (en) | High-power pump stripper based on hollow anti-resonance optical fiber | |
| CN102116902A (en) | Optic fiber power beam combiner and preparation method thereof | |
| EP1579257A1 (en) | Optical fiber lens and method of manufacture | |
| WO2007116792A1 (en) | Light input/output port of optical component and beam converting apparatus | |
| CN109768459A (en) | A kind of pump light stripper of laser ablation and preparation method thereof | |
| CN105487173A (en) | Mode field matching device and optical fiber laser | |
| WO2014002715A1 (en) | Optical fiber and optical cable | |
| CN105572802A (en) | Fiber welding point processing method | |
| CN101556352B (en) | Method for inhibiting propagation of energy-transmitting optical fibers at cladding mode | |
| US10833470B2 (en) | Optical fiber and fiber laser | |
| JP2007293298A (en) | Light input/output port of optical component | |
| CN110011170A (en) | A method of efficiently filtering out optical fiber high-order mode | |
| JP2007293300A (en) | Beam converting apparatus | |
| CN202837591U (en) | Diaphragm type optical fiber laser coupler | |
| CN112713490A (en) | Intermediate infrared band continuous all-fiber oscillator | |
| JP2014010258A (en) | Optical fiber and optical cable | |
| CN203574218U (en) | High-power optical fiber transmission system | |
| CN115657211A (en) | Mid-infrared optical fiber combiner based on end-face pumping and manufacturing method thereof | |
| Liu | The approximate ABCD matrix for a parabolic lens of revolution and its application in calculating the coupling efficiency | |
| CN114400493B (en) | Cladding light filtering structure of three-cladding optical fiber and manufacturing method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |