Laser spatial mode monitoring device and method based on cage structure

Abstract

The invention provides a laser spatial mode monitoring device and method based on a cage structure, and belongs to the field of laser mode monitoring. The problems that in the prior art, a laser space mode monitoring method is complex, and a monitoring system is not high in integration degree and inconvenient to use are solved. According to the technical scheme, the device comprises an F-P confocal cavity of a hollow structure, a fixing frame is arranged on the F-P confocal cavity, a mode coupling device and a data acquisition module are connected to the fixing frame, the mode coupling device is connected to the output end of a laser generation device through an optical fiber, and the mode coupling device comprises an optical fiber coupling piece and a plurality of first lenses; a first cavity mirror is arranged at one end, close to the first lens, of the F-P confocal cavity, the data acquisition module comprises a third lens and a photoelectric detection device, the third lens is arranged between the F-P confocal cavity and the photoelectric detection device, and a second cavity mirror is arranged at one end, close to the third lens, of the F-P confocal cavity; the method is applied to laser monitoring.

Description

Technical Field

[0001] The invention provides a laser space mode monitoring device and method based on a cage structure, belonging to the technical field of monitoring. Background Art

[0002] Laser mode monitoring is a core technology in laser physics, and is closely related to laser design, performance optimization, application effect improvement, and basic subject research.

[0003] With the development of high-brightness semiconductor pumping technology and double-clad doped fiber manufacturing technology, the output power of fiber lasers has been significantly improved. Fibers with large mode areas can reduce the power density within the core, effectively avoiding the generation of nonlinear effects such as stimulated Brillouin scattering and stimulated Raman scattering. However, the core of a fiber with a large mode area supports multiple modes. When signal light is injected into a fiber amplifier, although the main energy is concentrated in the fundamental mode, a small number of higher-order modes will inevitably be excited. Under high power conditions, the interference of the fundamental and higher-order modes will form a quasi-periodic temperature distribution in the fiber, which will further modulate the refractive index distribution in the core and form a long-period refraction grating, which will lead to energy coupling between the fundamental and higher-order modes and produce mode instability effects.

[0004] Laser mode instability can lead to increased beam divergence, decreased focusing ability, mode hopping, and mode competition, negatively impacting many fields. For example, in precision machining (such as micro-nano manufacturing), high-order modes can lead to poor beam quality, compromising machining accuracy. In quantum entangled light sources and compressed state preparation, mode purity directly affects quantum state fidelity and disrupts quantum correlations. In industrial processing, high-order modes can lead to uneven energy distribution and uneven material burning. Traditionally, monitoring laser output modes uses a FP cavity mode monitoring scheme. This involves splitting the free-space laser output with a beam splitter. This is then collimated by a pair of light guides and mode-matched by a pair of lenses, enabling the beam to be coupled into the FP cavity. However, each light guide and lens in these steps has up-down, left-right, and forward-backward degrees of freedom, and each setup requires assembly and setup of the mirror frame, making the entire mode monitoring system complex. With the continuous improvement of the stability, convenience, precision, integration and ease of operation of the mode monitoring system, it is particularly important to design a laser space mode monitoring device with high stability, high precision adjustment, easy use and high integration. Summary of the Invention

[0005] In order to solve the technical problems in the prior art of complex laser spatial mode monitoring methods, low monitoring system integration, and inconvenient use, the present invention proposes a laser spatial mode monitoring device and method based on a cage structure.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: a laser spatial mode monitoring device based on a cage structure includes a hollow FP confocal cavity, a fixing frame is provided on the FP confocal cavity, a mode coupling device and a data acquisition module are provided on the fixing frame, the mode coupling device is connected to the output end of the laser generating device via an optical fiber, and the mode coupling device, the FP confocal cavity, and the data acquisition module are arranged in sequence; The mode coupling device includes a fiber coupling element and a plurality of first lenses. The fiber coupling element and the first lenses are parallel to each other. The plurality of first lenses are parallel to each other. The plurality of first lenses are arranged between the FP confocal cavity and the fiber coupling element. A first cavity mirror is arranged on one end of the FP confocal cavity close to the first lenses. The data acquisition module includes a third lens and a photoelectric detection device, wherein the third lens is arranged between the FP confocal cavity and the photoelectric detection device, and a second cavity mirror is arranged on one end of the FP confocal cavity close to the third lens. The FP confocal cavity, the first cavity mirror and the second cavity mirror constitute the FP confocal cavity; A retractable device is provided between the second cavity mirror and the FP confocal cavity, and the photoelectric detection device is electrically connected to the oscilloscope; The first lens, the first cavity mirror, the second cavity mirror, and the third lens are parallel to each other and coaxially arranged.

[0007] Furthermore, the optical fiber coupling element, the FP confocal cavity and the first lens are coaxially arranged.

[0008] Furthermore, a first lens protection cover is provided on the first cavity mirror; A second lens protection cover is provided on the second cavity mirror, and a retractable device, a second cavity mirror and a protective gasket are crimped in sequence between the second lens protection cover and the FP confocal cavity. The retractable device is crimped between the second cavity mirror and the FP confocal cavity, and the protective gasket is crimped between the second cavity mirror and the second lens protection cover.

[0009] Furthermore, the fixing frame includes a first connecting member and a second connecting member, the first connecting member includes a plurality of first connecting rods, the plurality of first connecting rods are fixedly connected to the first end surface of the FP confocal cavity, the plurality of first connecting rods constitute a first cage structure, and the mode coupling device is placed in the first cage structure; The second connecting member includes a plurality of second connecting rods, which are fixedly connected to the second end surface of the FP confocal cavity. The plurality of second connecting rods constitute a second cage structure. The third lens and the photoelectric detection device are in the second cage structure. The first cage structure and the second cage structure are arranged opposite to each other.

[0010] Furthermore, the plurality of first connecting rods are distributed along the edge of the first end surface of the FP confocal cavity; and the plurality of second connecting rods are distributed along the edge of the second end surface of the FP confocal cavity.

[0011] Furthermore, the fixing frame includes a third connecting member, the third connecting member is disposed in the FP confocal cavity, and the third connecting member and the FP confocal cavity are parallel to each other.

[0012] Furthermore, the photoelectric detection device includes a signal processing module, which is electrically connected to the oscilloscope. The signal processing module is also electrically connected to a photodiode. The photodiode, the third lens and the FP confocal cavity are coaxially arranged.

[0013] Furthermore, the laser generating device adopts one of a fiber laser, a solid-state laser or a gas laser.

[0014] Furthermore, the retractable device is made of piezoelectric ceramics.

[0015] Furthermore, the above-mentioned laser spatial mode monitoring device based on the cage structure is used.

[0016] The laser spatial mode monitoring method based on a cage structure adopts the laser spatial mode monitoring device based on a cage structure described above.

[0017] The beneficial effects of the present invention compared to the prior art are: 1. The laser spatial mode monitoring device based on the cage structure of the present invention is connected to the output end of the laser generating device through an optical fiber, which reduces the restrictions on the placement of the laser generating device by the laser spatial mode monitoring device and makes laser spatial mode monitoring more convenient; 2. The laser spatial mode monitoring device of the present invention press-fits a protective gasket between the second cavity mirror and the second lens protection cover to prevent the second cavity mirror from being damaged when the retractable device retracts along the length direction of the confocal cavity FP; 3. The fixing device of the present invention adopts a cage structure, integrating the coupling mode module, the confocal cavity FP and the data acquisition module into one body, thereby improving the integration of the laser spatial mode monitoring device of the present invention and minimizing the use of optical components such as reflectors and lenses. At the same time, the cage structure that is easy to assemble and disassemble simplifies the structural design of the laser spatial mode monitoring device, reduces the space occupied, and facilitates maintenance. 4. The laser spatial mode monitoring device of the present invention is simpler to operate. When monitoring the laser spatial mode output by a laser generating device, it is only necessary to connect the optical fiber to the output end of the laser generating device. The lasers output by different laser generating devices can be monitored, which greatly improves the efficiency of laser spatial mode monitoring and expands the scope of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the accompanying drawings: Figure 1 The structure of the present invention is schematically shown Figure 1 ; Figure 2 The structure of the present invention is schematically shown Figure 2 ; Figure 3 This is a front view of the laser spatial mode monitoring device of the present invention; Figure 4 It is a left side view of the laser spatial mode monitoring device of the present invention; Figure 5 Schematic diagram of the positional relationship between the confocal cavity FP and the first cavity mirror and the second cavity mirror of the present invention; Figure 6 Schematic diagram of the structure of the confocal cavity FP of the present invention; Figure 7 Schematic diagram of the coordination relationship between the confocal cavity FP and the first cavity mirror of the present invention; Figure 8 Schematic diagram of the cooperation relationship between the first cavity mirror and the first lens protection cover of the present invention; Figure 9 Schematic diagram of the cooperation relationship between the retractable device and the second lens protection cover of the present invention; Figure 10 Schematic diagram of the structure of the second lens protection cover of the present invention; Figure 11 A schematic structural diagram of the photoelectric detection device of the present invention; Figure 12 It is a front view of the photoelectric detection device of the present invention; Figure 13 This is a schematic structural diagram of the photoelectric detection device of the present invention with the housing removed; Figure 14 This is a transmission peak curve graph outputted to an oscilloscope by the laser spatial mode monitoring device based on a cage structure of the present invention; Figure 15 Schematic diagram of the structure of the optical fiber coupling component of the present invention Figure 1 ; Figure 16 Schematic diagram of the structure of the optical fiber coupling component of the present invention Figure 2 ; In the figure: 1 is the FP confocal cavity, 2 is the optical fiber coupling component, 3 is the first lens holder, 4 is the third lens holder, 5 is the photoelectric detection device, 6 is the first lens protection cover, 7 is the second lens protection cover, 8 is the first lens, 9 is the third lens, 10 is the first cavity mirror, 11 is the second cavity mirror, 12 is the telescopic device, 13 is the x adjustment device, 14 is the y adjustment device, 15 is the first connecting rod, 16 is the second connecting rod, 17 is the first through hole, 18 is the second through hole, 19 is the housing, 20 is a threaded hole, 21 is a third through hole, 22 is a photodiode, 23 is an SMA connector, 24 is a circuit board, 25 is an electrode, 26 is a working status indicator, 27 is a switch device, 28 is a fourth through hole, 29 is a fifth through hole, 30 is a screw hole, 31 is a fiber coupling head, 32 is an x adjustment screw, 33 is a y adjustment screw, 34 is a z adjustment screw, 35 is a mounting plate, 36 is a mounting hole, 37 is a laser output end, 38 is a primary transmission peak, and 39 is a secondary transmission peak DETAILED DESCRIPTION

[0019] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate relative positions or positional relationships, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second" and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0020] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0021] like Figures 1 to 16As shown, the present invention provides a laser spatial mode monitoring device based on a cage structure, including a hollow FP confocal cavity 1, the FP confocal cavity 1 having a square structure, a fixed frame fixedly connected to the FP confocal cavity 1, a mode coupling device and a data acquisition module connected to the fixed frame, the mode coupling device, the FP confocal cavity 1, and the data acquisition module are connected in sequence, and the mode coupling device is connected to the output end of the laser generating device via an optical fiber. Specifically, the mode coupling device and the data acquisition module are both arranged along the length direction of the FP confocal cavity 1, and the mode coupling device and the data acquisition module are symmetrically arranged about the FP confocal cavity 1. A plurality of screw holes 30 are also provided on the outer wall of the FP confocal cavity 1 for fixing the FP confocal cavity 1 in a preset position to complete the laser spatial mode monitoring.

[0022] The fixing frame includes a first connecting member and a second connecting member. The FP confocal cavity 1 is fixedly connected to the mode coupling device via the first connecting member. The FP confocal cavity 1 is fixedly connected to the data acquisition module via the second connecting member.

[0023] The laser generator is used to output a laser signal. The laser generator can be a fiber laser, a solid-state laser, or a gas laser. The laser generator in this embodiment uses a fiber laser, which is connected to the output end of the laser generator via an optical fiber. The output power of the laser generator is set to within 100mW. If a solid-state laser or a gas laser is used, the laser signal output must be coupled into an optical fiber so that the laser signal can be injected into the mode coupling device through the optical fiber.

[0024] The mode coupling device is used to couple the laser signal output by the laser generator into the cavity of the FP confocal cavity 1. The mode coupling device includes a fiber coupler 2 and a plurality of first lenses 8. The laser output end 37 of the fiber coupler 2 corresponds to the first lens 8. In this embodiment, the fiber coupler 2 includes a fiber coupling head 31, which is fixedly connected to a mounting plate 35 by screws. The mounting plate 35 has four mounting holes 36, and the mounting plate 35 is fixedly connected to the fixing frame through the four mounting holes 36. The fiber coupling head 31 is model CP08FP / M and includes one x-adjustment screw 32, one y-adjustment screw 33, and three z-adjustment screws 34. Rotating the x-adjustment screw 32 adjusts the x-axis orientation of the lens mounted on the offset plate of the fiber coupling head 31. Rotating the y-adjustment screw 33 adjusts the y-axis orientation of the lens mounted on the offset plate of the fiber coupling head 31. Rotating the three z-adjustment screws 34 adjusts the distance between the lens mounted on the offset plate of the fiber coupling head 31 and the optical fiber. Rotating a single z-adjustment screw 34 adjusts the angle between the lens mounted on the offset plate of the fiber coupling head 31 and the optical fiber. This fiber coupling head 31 allows for adjustment in five degrees of freedom, enabling better coupling of laser light into the FP confocal cavity 1. The fiber coupler 2 is fixedly connected to the first connector via a coupling bracket. The fiber coupler 2 is connected to the output end of the laser generator via an optical fiber, effectively improving the convenience of laser spatial mode monitoring and reducing restrictions on the placement of the laser generator. This allows for greater flexibility in the relative positioning of the laser generator and the coupling mode device, facilitating laser mode monitoring. The fiber coupler 2 is parallel to the first lens 8, and multiple first lenses 8 are parallel to each other. The multiple first lenses 8 are positioned between the FP confocal cavity 1 and the fiber coupler 2. The first lens 8 is fixedly connected to the first lens holder 3, which is screwed to the first connector. In this embodiment, two first lenses 8 are provided, one concave and one convex. The concave and convex lenses cooperate to couple laser light into the FP confocal cavity 1. The order of mounting the concave and convex lenses can be adjusted based on the specific implementation environment, as long as the laser light output from the fiber coupler 2 is effectively coupled into the FP confocal cavity 1. A first cavity mirror 10 is fixedly connected to the side of the FP confocal cavity 1 close to the first lens 8. Specifically, the first cavity mirror 10 is bonded to the FP confocal cavity 1 using ultraviolet glue. A first lens protection cover 6 is installed on the first cavity mirror 10, and the first lens protection cover 6 is fixedly connected to the FP confocal cavity 1 by screws.

[0025] The first connecting member includes a plurality of first connecting rods 15, each of which is parallel to each other. The plurality of first connecting rods 15 are fixedly connected to the end face of the FP confocal cavity 1, and the plurality of first connecting rods 15 are distributed along the edge of the end face of the FP confocal cavity 1. Specifically, a fourth through hole 28 is reserved in the end face of the FP confocal cavity 1, and a screw is threadedly connected to the inner surface of the fourth through hole 28. The first connecting rods 15, the FP confocal cavity 1, the fourth through hole 28, and the screw cooperate to press the first connecting rods 15 onto the first end face of the FP confocal cavity 1. The plurality of first connecting rods 15 constitute a first cage structure, and the mode coupling device is placed within the first cage structure. In this embodiment, four first connecting rods 15 are provided, and the number of first connecting rods 15 can be adaptively adjusted according to the specific implementation environment.

[0026] The data acquisition module includes a third lens 9 and a photoelectric detection device 5. The third lens 9 is a convex lens, and the photoelectric detection device 5 is electrically connected to the oscilloscope. The third lens 9 and the photoelectric detection device 5 are both fixedly connected to the second connector. Specifically, the third lens 9 is fixedly mounted on the third lens holder 4, and the third lens holder 4 is fixedly connected to the second connector by screws. The third lens 9 is placed between the FP confocal cavity 1 and the photoelectric detection device 5. The side of the FP confocal cavity 1 close to the third lens 9 is fixedly connected to the second lens protection cover 7 by screws. The retractable device 12, the second cavity mirror 11 and the protective gasket are sequentially crimped between the second lens protection cover 7 and the FP confocal cavity 1. The retractable device 12 is crimped between the second cavity mirror 11 and the FP confocal cavity 1. The protective gasket is crimped between the second cavity mirror 11 and the second lens protection cover 7. The protective gasket is crimped between the second cavity mirror 11 and the second lens protection cover 7 to protect the second cavity mirror 11. The FP confocal cavity 1, the first cavity mirror 10 and the second cavity mirror 11 constitute the FP confocal cavity. In this embodiment, the protective gasket is an annular rubber ring.

[0027] The first lens protection cover 6 and the second lens protection cover 7 are both provided with a first through hole 17 and a second through hole 18. Screws pass through the first through hole 17 to fix the first lens protection cover 6 and the second lens protection cover 7 to the FP confocal cavity 1. The second through hole 18 is used to transmit the laser beam.

[0028] The retractable device 12 utilizes a piezoelectric ceramic, model HXmt150 / 12-6 / 10. The piezoelectric ceramic is connected to a power supply via a wire 13. Applying a 25 Hz triangular wave high-voltage signal to the piezoelectric ceramic causes it to expand and contract along the length of the FP confocal cavity 1. This causes the length of the FP confocal cavity, formed by the FP confocal cavity 1, the first cavity mirror 10, and the second cavity mirror 11, to periodically change. This allows lasers of different modes that meet resonance conditions to resonate within the FP confocal cavity and be transmitted. The triangular wave high-voltage signal is determined by the specifications of the selected piezoelectric ceramic. As long as the applied voltage causes the piezoelectric ceramic to produce a retractile motion that periodically changes the length of the FP confocal cavity, it is sufficient. In this embodiment, the voltage applied to the piezoelectric ceramic is within the range of 0 to 150 V, and the piezoelectric ceramic scanning frequency is 25 Hz. Those skilled in the art can make appropriate adjustments to the structure of the retractable device 12, as long as the retractable device 12 can be controlled so that when the retractable device 12 undergoes periodic deformation, it can drive the second laparoscope 11 to move to change the distance between the first laparoscope 10 and the second laparoscope 11, so that the distance between the first laparoscope 10 and the second laparoscope 11 changes periodically.

[0029] When the FP confocal cavity length is an integer multiple of half the wavelength of the laser light injected into FP confocal cavity 1, the laser light injected into FP confocal cavity 1 can resonate within FP confocal cavity 1. During the periodic variation of the FP confocal cavity length, the cavity lengths of different FP confocal cavities are integer multiples of half the wavelength of their corresponding laser longitudinal modes, allowing different laser longitudinal modes to be transmitted sequentially, outputting transmission peak signals. This process ensures that the peak value of the main transmission peak 38 in the transmission peak signal output by FP confocal cavity 1 reaches its adjustable maximum value. By monitoring the output transmission peak signal through a data acquisition module, laser mode monitoring can be achieved.

[0030] The photoelectric detection device 5 includes a signal processing module, which is electrically connected to the oscilloscope. The signal processing module is also electrically connected to the photodiode 22 . The photodiode 22 , the third lens 9 and the FP confocal cavity 1 are coaxially arranged.

[0031] Specifically, the photodetection device 5 includes a square housing 19, which forms a cavity within. The housing 19 is provided with a plurality of threaded holes 20. In this embodiment, four threaded holes 20 are provided, distributed at the four corners of the housing 19. The threaded holes 20 are loosely fitted with the second connecting rod 16. The threaded holes 20 and the second connecting rod 16 cooperate to securely connect the photodetection device 5 to the mounting bracket. A third through hole 21 is provided on a side wall of the housing 19. The third through hole 21 is located at the center of the housing 19. The third through hole 21 corresponds to and is coaxially arranged with the third lens 9. A photodiode 22 is fixedly connected to the third through hole 21. The photosensitive surface of the photodiode 22 corresponds to the center of the third lens 9. The photosensitive surface of the photodiode 22 cooperates with the third lens 9 to converge the laser light emitted from the FP confocal cavity 1 through the third lens 9 onto the photosensitive surface of the photodiode 22, thereby converting the laser light signal into a current signal. In this embodiment, the type of photodiode is not limited; as long as it can convert the laser light signal into an electrical signal, it will be sufficient.

[0032] A circuit board 24 is placed in the housing 19, and a signal processing module is integrated on the circuit board 24. The signal processing module is specifically a transimpedance amplifier circuit module that can convert a current signal into a voltage signal. The input end of the transimpedance amplifier circuit module is connected to the electrode 25 of the photodiode 22, and the output end of the transimpedance amplifier circuit module is electrically connected to the oscilloscope, outputting a voltage signal, which is the peak signal of the transmission peak. The output end of the transimpedance amplifier circuit module is connected to one end of the SMA connector 23 via a cable. The SMA connector 23 is nested on a side wall of the housing 19, and the other end of the SMA connector 23 is located outside the housing 19. The other end of the SMA connector 23 is used to electrically connect to the input end of the oscilloscope.

[0033] A working status indicator light 26 is also integrated on the circuit board 24 . The working status indicator light 26 is electrically connected to a switch device 27 . Both the working status indicator light 26 and the switch device 27 extend beyond the housing 19 .

[0034] Specifically, the laser emitted from the FP confocal cavity 1 is converged on the photosensitive surface of the photodiode 22 of the DC photodetection device 5 through the third lens 9, and the optical signal is converted into an electrical signal and then transmitted to the transimpedance amplifier circuit module. The electrical signal is amplified and output through the DC output end of the photodetection device 5. The electrical signal is transmitted to the oscilloscope through a cable, and the transmission peak signal is displayed on the oscilloscope. If the laser signal output by the laser generating device does not contain a high-order mode, the transmission peak of the oscilloscope has only one main transmission peak 38. If the laser signal output by the laser generating device contains a high-order mode, the transmission peak signal of the oscilloscope will display a main transmission peak 38 and a secondary transmission peak 39 that is smaller than the peak value of the main transmission peak 38. The laser spatial mode can be conveniently and effectively monitored by the oscilloscope. Figure 14As shown in the figure, the transmission peak signal displayed on the oscilloscope when the scanning frequency of the piezoelectric ceramic is 25Hz. The horizontal axis in the figure represents the time value, and the vertical axis represents the peak value of the transmission peak. The transmission peak curve includes a main transmission peak 38 and a secondary transmission peak 39 which is smaller than the peak value of the main transmission peak 38. The main transmission peak 38 represents the fundamental mode signal, and the secondary transmission peak 39 represents the high-order mode signal, that is, the laser signal output by the laser generating device includes the fundamental mode and the high-order mode.

[0035] The photoelectric detection device 5 is powered by two 1.5V batteries, which can further improve the integration and convenience of the laser spatial mode monitoring device based on the cage structure of the present invention.

[0036] Furthermore, the first lens 8, the first cavity mirror 10, the second cavity mirror 11, and the third lens 9 are parallel to each other, and the optical fiber coupler 2, the first lens 8, the first cavity mirror 10, the FP confocal cavity 1, the second cavity mirror 11, and the third lens 9 are coaxially arranged.

[0037] The second connecting member includes a plurality of second connecting rods 16, which are fixedly connected to the second end face of the FP confocal cavity 1. Specifically, a fifth through hole 29 is reserved on the second end face of the FP confocal cavity 1, and a screw is threadedly connected to the inner surface of the fifth through hole 29. The second connecting rods 16, the FP confocal cavity 1, the fifth through hole 29, and the screw cooperate to press the second connecting rods 16 onto the second end face of the FP confocal cavity 1. The plurality of second connecting rods 16 are distributed along the edge of the end face of the FP confocal cavity 1, and are parallel to each other. The plurality of second connecting rods 16 form a second cage structure, and the third lens 9 and the photoelectric detection device 5 are located within the second cage structure. In this embodiment, four second connecting rods 16 are provided.

[0038] An adjustment device is fixedly connected to the first lens frame 3 and the third lens frame 4. The adjustment device and the first lens frame 3 (third lens frame 4) cooperate with each other to have a three-dimensional adjustment function, which can accurately adjust the position of the first lens frame 3 and / or the third lens frame 4 in the horizontal direction (left and right), vertical direction (up and down), and depth direction (front and back), thereby changing the spatial positioning of the two on the fixed frame, thereby improving the accuracy of laser spatial mode monitoring.

[0039] Specifically, the adjustment device includes an x adjustment device 13 and a y adjustment device 14. By operating the x adjustment device 13, the horizontal (left and right) position of the first lens frame 3 (third lens frame 4) can be adjusted. By operating the y adjustment device 14, the vertical (up and down) position of the first lens frame 3 (third lens frame 4) can be adjusted. By operating the first lens frame 3 (third lens frame 4) to move along the direction of the fixed frame, the depth direction (front and back) position of the first lens frame 3 (third lens frame 4) can be adjusted.

[0040] In another embodiment, the first connector and the second connector form an integrated structure, referred to as a third connector. The third connector extends through the FP confocal cavity 1, thereby sequentially connecting the mode coupling device, the FP confocal cavity 1, and the data acquisition module. The third connector includes four third connecting rods, which are located at the four corners of the FP confocal cavity 1.

[0041] The laser space mode monitoring method based on a cage structure provided by the present invention adopts the laser space mode monitoring device based on a cage structure.

[0042] The working principle of the present invention is: After the laser generator outputs a laser signal, the size and position of the waist spot of the output laser beam are adjusted through the optical fiber coupler 2, and the left and right, up and down positions of the laser beam output by the optical fiber coupler 2 are adjusted. Then, the laser beam output by the laser generator enters the first lens 8, and the laser signal is pattern matched in the first lens 8. The output laser signal is coupled into the FP confocal cavity 1. The FP confocal cavity 1 can separate the mode of the continuous laser signal emitted by the laser generator, and change the cavity length of the FP confocal cavity under the action of piezoelectric ceramics to transmit laser light that meets the resonance conditions, thereby causing the FP confocal cavity 1 to output a transmission peak signal. The transmission peak signal is displayed on the oscilloscope after passing through the third lens 9 and the photoelectric detection device 5 in sequence. On the oscilloscope, whether the laser emitted by the laser generator contains a high-order mode is judged according to the type of the displayed transmission peak.

[0043] Regarding the specific structure of the present invention, it should be noted that the connection relationship between the various component modules adopted in the present invention is definite and feasible. Except for those specifically described in the embodiments, the specific connection relationship can bring about corresponding technical effects and solve the technical problems raised by the present invention without relying on the execution of corresponding software programs. The components, modules, models of specific components appearing in the present invention, the connection methods between each other, and the conventional usage methods and expected technical effects brought about by the above-mentioned technical features, except for those specifically described, all belong to the disclosed contents in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by technical personnel in this field before the application date, or belong to the existing technologies such as conventional technology and common knowledge in this field. There is no need to elaborate, so that the technical solution provided in this case is clear, complete, and feasible, and the corresponding physical products can be reproduced or obtained based on this technical means.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser spatial mode monitoring device based on a cage structure, characterized by: A FP confocal cavity (1) having a hollow structure is provided on the FP confocal cavity (1), a fixing frame is provided on the fixing frame, a mode coupling device and a data acquisition module are provided on the fixing frame, the mode coupling device is connected to the output end of the laser generating device via an optical fiber, and the mode coupling device, the FP confocal cavity (1), and the data acquisition module are provided in sequence; The mode coupling device comprises an optical fiber coupling member (2) and a plurality of first lenses (8), the optical fiber coupling member (2) and the first lenses (8) are parallel to each other, the plurality of first lenses (8) are parallel to each other, the plurality of first lenses (8) are arranged between the FP confocal cavity (1) and the optical fiber coupling member (2), and a first cavity mirror (10) is arranged on one end of the FP confocal cavity (1) close to the first lenses (8); The data acquisition module comprises a third lens (9) and a photoelectric detection device (5), wherein the third lens (9) is arranged between the FP confocal cavity (1) and the photoelectric detection device (5), and a second cavity mirror (11) is arranged on one end of the FP confocal cavity (1) close to the third lens (9), and the FP confocal cavity (1), the first cavity mirror (10) and the second cavity mirror (11) constitute the FP confocal cavity; A retractable device (12) is provided between the second cavity mirror (11) and the FP confocal cavity (1), and the photoelectric detection device (5) is electrically connected to an oscilloscope; The first lens (8), the first cavity mirror (10), the second cavity mirror (11), and the third lens (9) are parallel to each other and are coaxially arranged.

2. The laser spatial mode monitoring device based on a cage structure according to claim 1, characterized in that: The optical fiber coupling element (2), the FP confocal cavity (1) and the first lens (8) are coaxially arranged.

3. The laser spatial mode monitoring device based on a cage structure according to claim 1, characterized in that: A first lens protection cover (6) is provided on the first cavity mirror (10); A second lens protection cover (7) is provided on the second cavity mirror (11); a retractable device (12), the second cavity mirror (11) and a protective gasket are sequentially crimped between the second lens protection cover (7) and the FP confocal cavity (1); the retractable device (12) is crimped between the second cavity mirror (11) and the FP confocal cavity (1); and the protective gasket is crimped between the second cavity mirror (11) and the second lens protection cover (7).

4. The laser spatial mode monitoring device based on a cage structure according to claim 1, characterized in that: The fixing frame comprises a first connecting member and a second connecting member, the first connecting member comprises a plurality of first connecting rods (15), the plurality of first connecting rods (15) are fixedly connected to a first end face of the FP confocal cavity (1), the plurality of first connecting rods (15) constitute a first cage structure, and the mode coupling device is placed in the first cage structure; The second connecting member comprises a plurality of second connecting rods (16), the plurality of second connecting rods (16) being fixedly connected to the second end face of the FP confocal cavity (1), the plurality of second connecting rods (16) forming a second cage structure, the third lens (9) and the photoelectric detection device (22) being located in the second cage structure, and the first cage structure and the second cage structure being arranged relative to each other.

5. The laser spatial mode monitoring device based on a cage structure according to claim 4, characterized in that: A plurality of first connecting rods (15) are distributed along the edge of the first end surface of the FP confocal cavity (1); and a plurality of second connecting rods (16) are distributed along the edge of the second end surface of the FP confocal cavity (1).

6. The laser spatial mode monitoring device based on a cage structure according to claim 1, characterized in that: The fixing frame comprises a third connecting member, the third connecting member is arranged in the FP confocal cavity (1), and the third connecting member and the FP confocal cavity (1) are parallel to each other.

7. The laser spatial mode monitoring device based on a cage structure according to claim 1, characterized in that: The photoelectric detection device (5) comprises a signal processing module, which is electrically connected to an oscilloscope. The signal processing module is also electrically connected to a photodiode (22). The photodiode (22), the third lens (9) and the FP confocal cavity (1) are coaxially arranged.

8. The laser spatial mode monitoring device based on a cage structure according to claim 1, characterized in that: The laser generating device adopts one of a fiber laser, a full solid-state laser or a gas laser.

9. The laser spatial mode monitoring device based on a cage structure according to claim 1, characterized in that: The retractable device (12) is made of piezoelectric ceramics.

10. A laser spatial mode monitoring method based on a cage structure, characterized in that: A laser spatial mode monitoring device based on a cage structure as described in any one of claims 1 to 9 is used.

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