CN216929158U

CN216929158U - High-power optical fiber laser

Info

Publication number: CN216929158U
Application number: CN202220569893.1U
Authority: CN
Inventors: 刘茵紫; 兰根书; 王勇
Original assignee: Wuhan Juhere Photonics Technologies Co ltd
Current assignee: Wuhan Juhere Photonics Technologies Co ltd
Priority date: 2022-03-16
Filing date: 2022-03-16
Publication date: 2022-07-08
Anticipated expiration: 2032-03-16

Abstract

The utility model is suitable for the technical field of lasers, and provides a high-power optical fiber laser which comprises a pumping light source, a first convex lens, a second convex lens, a reflector and a laser resonant cavity which are sequentially arranged, wherein the laser resonant cavity comprises two end caps which are oppositely arranged, the two end caps are connected through an active optical fiber, the end caps are a convex surface, a cylindrical part, a circular table part and a tail cylinder in sequence from the outer side to the inner side, the tail cylinders of the two end caps are welded with the active optical fiber on the corresponding side, and the surface of the convex surface is plated with an antireflection film. The utility model realizes the integration of the laser resonant cavity, the large-mode-field active optical fiber and the end cap by reasonably designing the optical path structure of the laser, greatly reduces the influence of a complex spatial optical path on the stability of the system, simultaneously improves the end surface damage threshold value and reduces the interference of backward return light on the system.

Description

High-power optical fiber laser

Technical Field

The utility model belongs to the field of lasers, and particularly relates to a high-power fiber laser.

Background

In recent years, high-power fiber lasers have made rapid progress in both continuous wave and pulse lasers, and are widely applied to the fields of material processing, military, national defense, aerospace, aviation and the like. With the increase of output power, Large-mode aera (LMA) fiber is generally used to reduce the influence of adverse factors such as nonlinear effect and end face damage in the fiber core. For example, for an ytterbium-doped LMA fiber with a core diameter of 20 μm, continuous wave output powers of up to 810W can be achieved with almost a single transverse mode. However, as the core of the active fiber is further increased to more than 25 μm, challenges are posed to the fabrication of passive devices matched with the active fiber, such as Fiber Bragg Gratings (FBGs) as high mirrors and output couplers, on one hand, since there are multiple modes in the LMA fiber that are transmitted simultaneously, the reflectivity of the FBGs cannot be determined from their transmission spectra; on the other hand, two modes in the LMA fiber, whose propagation constants are close to each other, may interfere after reflection by the FBG. Therefore, when a high-power laser is built by using a large-mode-field multimode active fiber as a gain medium, a space structure is generally adopted in a system structure because a Fiber Bragg Grating (FBG) pair matched with the large-mode-field multimode active fiber is lacked to form a resonant cavity. However, the space structure of the conventional high-power optical fiber laser is complex in connection and not compact enough, and the complex space optical path is not beneficial to realizing high-power stability, high long-term reliability and compact packaging of the system, so that the service life of the laser is shortened, and the use cost is increased.

SUMMERY OF THE UTILITY MODEL

In view of the above problems, an object of the present invention is to provide a high power fiber laser, which aims to solve the technical problem of low stability of the conventional high power fiber laser.

The utility model adopts the following technical scheme:

high power fiber laser is including the pumping light source, first convex lens, second convex lens, speculum and the laser resonator who places in order, the laser resonator is including two end caps that set up relatively, and one of them end cap is the input end cap, and another end cap is the output end cap, connects through active fiber between two end caps, and the structure of two end caps is the same, is convex surface, cylinder portion, boss portion, afterbody cylinder in proper order from the outside to inboard, and the afterbody cylinder and the active fiber fusion of corresponding side of two end caps have plated the antireflection coating on the surface of convex surface.

Further, the laser resonator includes the box body, there are ring groove and control panel in the box body, the symmetry is opened there is the wire casing on the ring groove, there is the connector box body both sides, the box body inboard corresponds the connector position and installs fixed cover, fixed cover includes platelet and position sleeve, the platelet is fixed in the box body inboard, the position sleeve openly has the aperture, the aperture diameter is located the diameter range of two terminal surfaces of boss portion, the end cap is installed to the position sleeve in and is exposed the afterbody cylinder, active fiber place in the ring groove, and active fiber both ends pass and correspond the side wire casing and with the butt fusion of corresponding afterbody cylinder.

Furthermore, the annular groove is provided with a pressing plate, and the pressing plate covers the wire groove.

Furthermore, L-shaped brackets are formed downwards on two sides of the bottom of the box body.

Furthermore, the back of the L-shaped bracket is provided with a fixing hole.

The utility model has the beneficial effects that: the utility model realizes the integration of the laser resonant cavity, the large mode field active optical fiber and the end cap by reasonably designing the optical path structure of the laser, greatly reduces the influence of a complex spatial optical path on the stability of the system, simultaneously improves the end surface damage threshold value and reduces the interference of backward return light on the system.

Drawings

Fig. 1 is a schematic diagram of a high power fiber laser provided by an embodiment of the present invention;

FIG. 2 is a block diagram of an end cap provided by an embodiment of the present invention;

FIG. 3 is a block diagram of a laser resonator provided by an embodiment of the present invention;

fig. 4 is a partially enlarged view of fig. 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and do not limit the utility model.

In order to illustrate the technical means of the present invention, the following description is given by way of specific examples.

Fig. 1 illustrates a structure of a high power fiber laser provided by an embodiment of the present invention, and only a portion related to the embodiment of the present invention is illustrated for convenience of description.

As shown in fig. 1, the high-power fiber laser provided by this embodiment includes a pump light source 04, a first convex lens 05, a second convex lens 06, a mirror 07, and a laser resonant cavity 08, which are sequentially disposed, where the laser resonant cavity 08 includes two end caps disposed oppositely, one end cap is an input end cap 02, the other end cap is an output end cap 03, and the two end caps are connected through an active fiber 01. As shown in fig. 2, the two end caps have the same structure, and include, in order from the outside to the inside, a convex surface 021, a cylindrical portion 022, a boss portion 023, and a tail cylinder 024, wherein the tail cylinder 024 of the two end caps is welded to the corresponding side active fiber 01, and the surface of the convex surface 021 is coated with an antireflection film.

In the structure, the pumping light source can be a semiconductor laser with tail fiber output, and the end face of the optical fiber is positioned on the focus of the first convex lens. The first and second convex lenses are used for collimating and focusing the pump light, the damage threshold is greater than the maximum power density of the pump light incident on the mirror surface of the first and second convex lenses, and the focal lengths of the first and second convex lenses can be determined according to practical application. The reflector is a 45-degree reflector, the surface of the reflector is coated with a film, the reflector is highly reflective to the pump light (the reflectivity is more than or equal to 99.9% @915nm/976nm), the mirror surface of the reflector is positioned on the focal plane of the second biconvex lens, and the damage threshold of the reflector is greater than the maximum power density of the focused pump light.

The active optical fiber has a large mode fieldThe source optical fiber has a core diameter of 25 μm or more, and comprises three parts, a core, a cladding and a coating layer, wherein the refractive indices are n₁，n₂And n₃，n₁Is always greater than n₂And forming a core-cladding waveguide structure. The active fiber may be single clad or double clad. When the active fiber is single clad, n₂＜n₃A fiber core pump is adopted; when the active fiber is double-clad, n₂＞n₃Cladding pumping is used.

The front end of the input end cap 02 is polished into a convex surface 021 with optical mirror finish, the outer surface of the input end cap is plated with an antireflection film, the antireflection film is highly transparent to pump light (the transmittance is more than or equal to 99.5% @915nm/976nm) and highly reflective to laser light (the reflectivity is more than or equal to 99.9% @ 1000-1100 nm), and the diameter of a spherical surface is far larger than the diameter of a light spot of incident pump light. The curvature of the convex surface 021 is determined according to the divergence angle of the transmitted laser, and the straight line of the laser propagation direction in the divergence angle is ensured to be vertical to the convex surface 021. The cylindrical portion 022 is the end cap middle portion. The circular truncated cone portion 023 is the rear portion of the end cap which is polished to be circular truncated cone shape, and the included angle between any two buses of the circular truncated cone is guaranteed to be far larger than the numerical aperture angle of the optical fiber. The tail cylinder 024 is an optical fiber tail cylinder and is used for fusion splicing with an active optical fiber, the end face of the tail cylinder also ensures the smoothness of an optical mirror face, the diameter of the tail cylinder is larger than that of the active optical fiber, the center of a front-end convex surface and the center of a rear-end tail cylinder plane are on the same horizontal line, and the focal length of the front-end convex surface is equal to the length of an end cap. The output end cap 03 and the input end cap 02 have the same size and specification, but have certain difference in the parameters of the antireflection film plated on the outer surface of the convex surface of the output end cap, and have high transmittance (the transmittance is more than or equal to 99.5% @915nm/976nm) for pump light and high transmittance (the transmittance is more than or equal to 90% @ 1000-1100 nm) for laser light. The tail cylinder of the output end cap is welded with the large-mode-field active optical fiber, and the front convex focal length is equal to the length of the end cap.

As an example, a semiconductor laser with a tail fiber is used as a pump source, the laser wavelength is 915nm, the size of a core/cladding of an output optical fiber is 200/220 microns, the numerical aperture is 0.22, the output power of a single pump source is 500W, and the number of the pump sources and the pump power can be adjusted according to the required laser power. The pump light emergent point is positioned on the focus of the first convex lens, the focal length of the convex lens is 5mm, the diameter of the lens is 25mm, and the diameter of the lens is larger than the diameter of an incident pump light spot. After passing through the first convex lens, the divergent pumping light is collimated into parallel light, the focal length of the second convex lens is 10mm, the parallel light is converged, and the diameter of a converged light spot is smaller than the diameter of a large mode field active optical fiber cladding by controlling the spherical aberration of the lenses. The pump light is injected into the active fiber inner cladding through the input end cap by the mirror 07. Rare earth doped ions in the active optical fiber absorb photons to generate stimulated amplification radiation, and the stimulated amplification radiation oscillates and amplifies back and forth in a resonant cavity formed by the two coating end caps to form laser output.

Conduct laser resonator's a concrete structure, as shown in fig. 3, 4, laser resonator 08 includes box body 81, there are circular ring groove 82 and control panel 83 in the box body 81, the symmetry is opened on the circular ring groove 82 has wire casing 84, there is connector 85 box body 81 both sides, fixed cover is installed to box body 81 inboard correspondence connector position, fixed cover includes platelet 86 and position sleeve 87, platelet 86 is fixed in box body 81 inboard, position sleeve 87 openly has aperture 89, aperture 86 diameter is located the diameter range of two terminal surfaces of round platform portion 023, the end cap is installed to the position sleeve 87 in and is exposed the afterbody cylinder, active optical fiber places 01 in circular ring groove 82, and active optical fiber 01 both ends pass correspond side wire casing 84 and with the butt fusion of corresponding afterbody cylinder.

In the structure, a cover plate (not shown) is arranged on the box body, the connector is an optical fiber connector, a light path reflected by the reflector is connected to the optical fiber connector through optical fiber guiding, then the light path enters the input end cap and the active optical fiber, rare earth doped ions in the active optical fiber absorb photons to generate stimulated amplification radiation, and the light path oscillates and amplifies back and forth in a resonant cavity formed by the two coated end caps to form laser output. The end cap is arranged in the positioning sleeve in the structure, and part of the end cap is exposed out of the small hole of the positioning sleeve, so that welding is facilitated. The end cap and the positioning sleeve are integrally fixed on the side wall of the box body through the small plate, so that the stability of the mounting structure is improved. In addition, a pressing plate 88 is arranged on the annular groove 82, and the pressing plate 88 covers the wire groove 84, so that the active optical fiber can be prevented from shaking and separating, and the working stability is ensured.

In addition, L-shaped supports 11 are formed downwards on two sides of the bottom of the box body 1, fixing holes (not shown in the figure) are formed in the back faces of the L-shaped supports 11, and the device is installed on the platform through the L-shaped supports and cannot shake randomly.

To sum up, the utility model discloses a reasonable light path and structural design adopt big mode field active optical fiber as the gain medium, connect the two through the butt fusion, have reduced the influence of complicated space light path to system stability on the one hand, and on the other hand has improved the terminal surface damage threshold value, has reduced the interference to the system to the back return light.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. The utility model provides a high power fiber laser, its characterized in that, high power fiber laser is including the pumping light source, first convex lens, second convex lens, speculum and the laser resonator who places in order, the laser resonator is including two end caps that set up relatively, and one of them end cap is the input end cap, and another end cap is the output end cap, connects through active optical fiber between two end caps, and the structure of two end caps is the same, is convex surface, cylinder portion, circular table portion, afterbody cylinder from outside to inboard in proper order, and the afterbody cylinder of two end caps and the butt fusion of the active optical fiber of corresponding side, antireflection coating has been plated on the surface of convex surface.

2. The high-power optical fiber laser device as claimed in claim 1, wherein the laser resonant cavity includes a box body, the box body has a circular groove and a control board, the circular groove has wire grooves symmetrically opened thereon, the box body has connectors on both sides, a fixing sleeve is installed on the inner side of the box body corresponding to the positions of the connectors, the fixing sleeve includes a small plate and a positioning sleeve, the small plate is fixed on the inner side of the box body, the positioning sleeve has a small hole on the front side, the diameter of the small hole is within the diameter range of the two end faces of the circular table portion, the end cap is installed into the positioning sleeve and exposes the tail cylinder, the active optical fiber is placed in the circular groove, and the two ends of the active optical fiber pass through the corresponding side wire grooves and are welded with the corresponding tail cylinder.

3. The high power fiber laser of claim 2, wherein the annular groove has a platen thereon, and the platen covers the wire groove.

4. The high power fiber laser of claim 3, wherein L-shaped brackets are formed downward on both sides of the bottom of the box.

5. The high power fiber laser of claim 4, wherein the L-shaped support is backed with a fixation hole.