CN102931585A - External-cavity-beam-combination semiconductor laser fiber coupling module - Google Patents

Abstract

The invention relates to an external cavity combined semiconductor laser fiber coupling module, which includes a plurality of single-tube semiconductor lasers of the same wavelength; each of the single-tube semiconductor lasers is fixed on an arc-shaped heat sink; Multiple beams are incident on the diffraction grating through different inclination angles, and the spots overlap on the diffraction grating. Under the light splitting effect of the diffraction grating and the feedback of the external cavity mirror, the beam emitted by each single-tube semiconductor laser is transmitted by the back cavity of the laser. The external cavity feedback and wavelength locking are realized in the resonant cavity formed by the external cavity surface and the external cavity mirror, and the multi-path beams are combined into one beam by the diffraction grating to realize the external cavity beam combination, and finally coupled into the multimode fiber through the focusing mirror. The invention combines the beams emitted by multiple single-tube semiconductor lasers and outputs them with the beam quality of a single laser, and can realize the laser output with fine core diameter, high power and high beam quality of the fiber coupling module.

Description

A semiconductor laser fiber coupling module for external cavity beam combining

technical field

The invention relates to the technical field of single-tube semiconductor lasers, in particular to an external cavity combining semiconductor laser fiber coupling module.

Background technique

Because the single-tube semiconductor laser has the advantages of high beam quality, good heat dissipation, and long life, the fiber-coupled module made of single-tube beam combining technology has great advantages in laser medical treatment, fiber laser pumping, laser monitoring, and laser processing. Wide range of applications. However, with the development of semiconductor laser technology application in recent years, there are higher requirements for the output power and beam quality of fiber-coupled modules in practical applications. Most of the beam combining of single-tube semiconductor lasers in the world adopts the traditional spatial beam combining method, because the spatial beam combining is only to make the beams closely superimpose multiple one-dimensional or two-dimensional arrays side-to-side in space, increasing the The power also degrades the beam quality. Here, multiple single-tube semiconductor lasers are arranged in an arc, and the diffraction grating is used to realize beam combining in the external cavity, and the beam quality of a single laser is output. Compared with the fiber coupling module made of ordinary space beam combining, the beam quality is much better increase in magnitude.

Figure 4 is a schematic diagram of a fiber-coupled module that uses a spatial beam combining method for single-tube beam combining, which is currently the main single-tube beam combining technology in the world (100 W / 100 μm passively cooled, fiber coupled diode laser at 976 nm based on multiple 100 μm single emitters, Marcel Werner, Christian Wessling, Stefan Hengesbach, Proc. of SPIE Vol. 7198 71980P-1). The device shown in FIG. 4 fixes a plurality of single-tube semiconductor lasers 11 on each step of a stepped metal heat sink 12 , and each step has the same shape. The light emitted by each laser is collimated by the fast-axis collimating mirror 13 and the slow-axis collimating mirror 14, and then the beam is reflected by the reflector 15, and the light emitted by all lasers is reflected in the fast-axis direction for spatial beam combining. Focusing is then performed by a focusing mirror 16 . The beam spot after beam combining is shown in Figure 5. This method of spatial beam combining increases the power and at the same time increases the spot size of the entire beam, deteriorating the beam quality and making it difficult to obtain laser output with high beam quality.

Contents of the invention

In order to solve the problems of low output brightness and poor beam quality of the beam combining module in the existing single-tube semiconductor laser beam combining technology, the present invention provides an external cavity beam combining semiconductor laser fiber coupling module that can achieve high brightness and high beam quality output .

In order to solve the problems of the technologies described above, the technical solution of the present invention is specifically as follows:

An external cavity combined semiconductor laser fiber coupling module, including a plurality of single-tube semiconductor lasers of the same wavelength; each of the single-tube semiconductor lasers is fixed on a transitional heat sink, and the transitional heat sink is fixed on an arc-shaped heat sink ; Multiple beams emitted by multiple single-tube semiconductor lasers are incident on the diffraction grating through different inclination angles, and the spots overlap on the diffraction grating, and then diffracted to the external cavity mirror at the same diffraction angle; after the multiple beams are fed back by the external cavity mirror Return along the original optical path, so that each single-tube semiconductor laser receives its own output feedback; the multi-column beams after the output feedback are combined into one beam after passing through the diffraction grating, and coupled into the multimode fiber through the focusing mirror.

In the above technical solution, the front cavity surface of each single-tube semiconductor laser (2) is coated with an anti-reflection film with a transmittance above 99%.

In the above technical solution, a fast-axis collimator and a slow-axis collimator for reducing the divergence angle of the fast and slow axes of the laser are respectively installed in front of each single-tube semiconductor laser; the fast-axis collimator is a cylinder A microlens or a spherical microlens; the slow axis collimator is a cylindrical microlens or a spherical microlens.

In the above technical solution, the number of the single-tube semiconductor lasers on the arc-shaped heat sink is at least two.

In the above technical solution, the diffraction grating is a transmission type diffraction grating or a reflection type diffraction grating.

In the above technical solution, the external cavity mirror is a parallel flat plate with a certain reflectivity, and the reflectivity value is from 1% to 50%.

In the above technical solution, the placement direction of the external cavity mirror is strictly perpendicular to the direction of the diffracted light beam.

In the above technical solution, the focusing mirror is a spherical lens, an aspherical lens or two separate cylindrical mirrors.

In the above technical solution, the wavelength of the single-tube semiconductor laser is from 400nm to 2000nm.

In the above technical solution, the core diameter of the multimode optical fiber ranges from 50 μm to 600 μm, the numerical aperture ranges from 0.1 to 0.3, and the optical power output ranges from 1W to 200W.

The external cavity beam combining semiconductor laser fiber coupling module of the present invention has the following advantages:

The external cavity beam combining semiconductor laser fiber coupling module of the present invention uses a diffraction grating in the single tube beam combining, and under the light splitting effect of the diffraction grating and the feedback of the external cavity mirror, the beam emitted by each single tube semiconductor laser is generated by The external cavity feedback and wavelength locking are realized in the resonant cavity formed by the rear cavity surface of the laser and the external cavity mirror, and the multi-path beams are combined into one beam by the diffraction grating to realize the external cavity beam combination, and finally coupled into the multimode fiber through the focusing mirror.

This method can combine the beams emitted by multiple single-tube semiconductor lasers and output them with the beam quality of a single laser, and can realize the fine-core diameter, high-power, and high-beam quality laser output of the fiber-coupled module.

In the structure of the external cavity combined semiconductor laser fiber coupling module of the present invention, the number of lasers can be determined according to the total laser power required and the power, mechanical size, and heat dissipation conditions of a single laser, which is very flexible. The upper limit of the laser depends on the gain spectral width of the laser, the diffraction ability of the diffraction grating and the damage threshold of the diffraction grating.

Description of drawings

Fig. 1 is a structural schematic diagram of a specific embodiment of the external cavity beam combining semiconductor laser fiber coupling module of the present invention, and its diffraction grating is a reflective diffraction grating;

Fig. 2 is a structural schematic diagram of another specific embodiment of the external cavity beam combining semiconductor laser fiber coupling module of the present invention, and its diffraction grating is a transmission type diffraction grating;

Fig. 3 is a schematic diagram of the light spot after combining beams through a diffraction grating in the specific embodiment shown in Fig. 1 of the present invention;

Fig. 4 is a schematic diagram of an external cavity beam combining semiconductor laser fiber coupling module realized by existing spatial beam combining technology;

Fig. 5 is a schematic diagram of spot placement after beam combining of the external cavity beam combining semiconductor laser fiber coupling module realized by the existing spatial beam combining technology.

Detailed ways

The inventive idea of the present invention is: a semiconductor laser single-tube beam-combining fiber coupling module, including a plurality of single-tube semiconductor lasers of the same wavelength; each of the single-tube semiconductor lasers is fixed on a transitional heat sink, and the transitional heat sink Fixed on the arc-shaped heat sink; multiple beams emitted by multiple single-tube semiconductor lasers are incident on the diffraction grating through different inclination angles, and the light spots overlap on the diffraction grating, and then diffract to the external cavity mirror at the same diffraction angle; multiple beams The beam is fed back by the external cavity mirror and returns along the original optical path, so that each single-tube semiconductor laser receives its own output feedback; multiple beams after the output feedback pass through the diffraction grating and then synthesize into one beam, which is coupled into the multimode fiber through the focusing mirror . A fast-axis collimating mirror and a slow-axis collimating mirror for reducing the divergence angle of the fast and slow axes of the laser are respectively installed in front of each single-tube semiconductor laser.

In the external cavity combining semiconductor laser fiber coupling module of the present invention, the front cavity surface of the single-tube laser used is coated with an anti-reflection film, and the transmittance is above 99%. The single-tube laser is welded on the transitional heat sink, and the transitional heat sink passes through the The fixing screw is fixed with the arc-shaped heat sink, and all the lasers are emitted in an arc and are on the same plane. The light emitted by all single-tube semiconductor lasers has a small divergence angle after passing through the fast-axis collimator mirror and the slow-axis collimator mirror. Each beam is incident on the diffraction grating at a certain inclination angle, and each beam spot Superposition occurs on , and the superimposed spot is the same as that of a beam of light. Semiconductor lasers have a wide spectrum, usually up to 2-3nmFWHM. Reversing the spectroscopic function and wavelength selection function of the grating, the wavelength of the beam emitted by the laser and the light whose corresponding incident angle satisfies the grating equation are diffracted to the external cavity mirror at the same angle. Due to the partial feedback of the external cavity mirror and the reversibility according to the optical path Principle, this part of the light beam vertically incident on the external cavity mirror will return to the respective laser cavity through the diffraction grating according to the original optical path, so that each laser will receive the output feedback of its own unit and will be connected by the rear end face of the laser. Oscillation is carried out in the new resonant cavity formed by the external cavity mirror, and the wavelength fed back by each laser changes linearly in turn. According to the mode competition theory of semiconductor lasers, the effect of feedback forces each laser to excite laser output with the same wavelength as the injected feedback. In this way, each laser excites light beams with slightly different wavelengths and is incident on the diffraction grating. At this time, the wavelength of each beam and its respective incident angle satisfy the grating equation. The diffraction grating can convert these light beams with different wavelengths and incident angles into the same The diffraction angles are combined into one beam and output through the external cavity mirror to realize the external cavity beam combination, and finally coupled into the multimode fiber through the focusing mirror.

The present invention will be described in further detail below in conjunction with the embodiment given with accompanying drawing.

1 and 3 show a specific embodiment of the external cavity beam combining semiconductor laser fiber coupling module of the present invention. Referring to Fig. 1, the external cavity beam combining semiconductor laser fiber coupling module of the present invention includes a transitional heat sink 1, multiple single-tube semiconductor lasers 2 of the same wavelength, an arc heat sink 3, fixing screws 4, and a fast axis collimator 5. Slow axis collimating mirror 6, diffraction grating 7, external cavity mirror 8, focusing mirror 9, multimode optical fiber 10.

The laser used in the present invention is a single-tube semiconductor laser 2 with an AlN ceramic chip module package. The single-tube semiconductor laser 2 can be fixed on the transitional heat sink 1 by welding, and the transitional heat sink 1 can be fixed on the arc by the fixing screw 4. On the heat sink 3, both the transition heat sink 2 and the arc heat sink 3 should be made of metal with high thermal conductivity, such as oxygen-free copper; of course, in other specific embodiments, the laser can also be directly sintered on the arc heat Shen 3 on. All single-tube semiconductor lasers 2 are arranged in an arc and on the same plane as shown in Fig. on the same plane. Since the sub-module of the laser is made of AlN material, it is not necessary to take insulation measures no matter whether it is connected in series or in parallel.

The external cavity beam combining semiconductor laser fiber coupling module of the present invention installs the fast axis collimating mirror 5 in front of the cavity of each laser 2 through a six-axis precision adjustment frame and ultraviolet glue, so that the beam in the fast axis direction is collimated. The bottom of the slow-axis collimating mirror 6 can be supported by a mechanical mirror base, and the slow-axis collimating mirror 6 and the mechanical mirror base are glued and fixed with ultraviolet glue. During the assembly process of the fast-axis collimating mirror 5 and the slow-axis collimating mirror 6, it is necessary to check whether the far-field spot positions of all lasers overlap on the predetermined position plane of the diffraction grating.

In the external cavity combined semiconductor laser fiber coupling module of the present invention, the diffraction grating 7 is made of photolithographic coating on the base material, the base material of the transmission grating is glass ceramics, and the base material of the reflection grating is metal. The diffraction grating 7 is adjusted by clamping the diffraction grating 7 with a six-axis adjustment frame and an appropriate fixture, and the diffraction grating 7 is placed at the overlapping position of the light spots, and fixed with ultraviolet glue or mechanical methods after adjustment.

In the external cavity beam combining semiconductor laser fiber coupling module of the present invention, the external cavity mirror 8 is a parallel flat plate, and the reflectivity value is from 1% to 50%. The base material of the external cavity mirror 8 is optical glass, one side is coated with an anti-reflection film, and the other side is coated with a semi-transparent and semi-reflective film, and the direction of the semi-transparent and semi-reflective film faces the diffraction grating 7 to realize optical feedback. The external cavity mirror 8 is clamped by the six-axis adjustment frame and an appropriate fixture for adjustment, so that the placement direction of the external cavity mirror 8 is strictly perpendicular to the diffraction direction of the diffraction grating 7 . Then install the focusing mirror 9 and the multimode optical fiber 10 in the optical path, and adjust them through the adjustment frame until the highest output power of the optical fiber is obtained, thus completing the adjustment of the optical path system.

In the external cavity combined semiconductor laser fiber coupling module of the present invention, a multimode optical fiber with a core diameter of 50 μm to 600 μm and a numerical aperture range of 0.1 to 0.3 can be used, and the laser wavelength is from 400nm to 2000nm. By selecting different laser numbers 2 ~Several units can obtain optical power output from 1W to 200W. The single-tube semiconductor laser 1 can be in the same polarization state or in different polarization states. The focusing mirror 9 can also be a spherical lens, and the fast-axis collimating mirror 5 and the slow-axis collimating mirror 6 are cylindrical microlenses. Of course, in other specific embodiments, the focusing mirror 9 can also be an aspheric lens or two separate cylindrical mirrors; the fast axis collimating mirror 5 and the slow axis collimating mirror 6 can also be respectively spherical microlenses.

The semiconductor laser fiber coupling module for external cavity beam combining of the present invention uses a diffraction grating in the single-tube beam combining, and the diffraction grating diffracts the light emitted by all single-tube lasers to the external cavity mirror at the same diffraction angle. Partial feedback, the beam will return to the cavity of the single-tube laser after passing through the diffraction grating. Due to the wavelength selection effect of the grating, each laser is forced to emit laser light with the same wavelength as the injected feedback, and finally these beams are combined into a single laser beam through the diffraction grating again. The beams are combined in the external cavity, and finally coupled into the multimode fiber through the focusing mirror. This method can combine the beams emitted by multiple single-tube semiconductor lasers and output them with the beam quality of a single laser, and can realize the fine-core diameter, high-power, and high-beam quality laser output of the fiber-coupled module.

Fig. 2 shows another specific embodiment of the external cavity beam combining semiconductor laser fiber coupling module of the present invention. The difference from the specific embodiment shown in FIG. 1 is that the diffraction grating is a transmission type diffraction grating. The working principle of the external cavity beam-combining semiconductor laser fiber coupling module in this specific embodiment is the same as that in the specific embodiment shown in FIG. 1 , so it will not be repeated here.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. An external cavity combined semiconductor laser fiber coupling module, characterized in that it includes multiple single-tube semiconductor lasers (2) of the same wavelength; each of the single-tube semiconductor lasers (2) is fixed on a transitional heat sink (1 ), the transitional heat sink (1) is fixed on the arc-shaped heat sink (3); multiple beams emitted by multiple single-tube semiconductor lasers (2) are incident on the diffraction grating (7) through different inclination angles, and the light spots are in the The diffraction grating (7) overlaps, and then diffracts to the external cavity mirror (8) at the same diffraction angle; multiple beams are fed back by the external cavity mirror (8) and return along the original optical path, so that each single-tube semiconductor laser (2 ) receives its own output feedback; the multiple light beams that have passed the output feedback pass through the diffraction grating (7) and then combine into one beam, which is coupled into the multimode optical fiber (10) through the focusing lens (9). 2. The external-cavity beam-combining semiconductor laser fiber coupling module according to claim 1, characterized in that, the front cavity surface of each single-tube semiconductor laser (2) is coated with an anti-reflection film with a transmittance of more than 99%. membrane. 3. The external-cavity beam-combining semiconductor laser fiber coupling module according to claim 1, characterized in that, each of the single-tube semiconductor lasers (2) is equipped with a fast axis for reducing the divergence angle of the fast and slow axes of the laser. A collimating mirror (5) and a slow-axis collimating mirror (6); the fast-axis collimating mirror (5) is a cylindrical microlens or a spherical microlens; the slow-axis collimating mirror (6) is a cylindrical microlens lens or spherical microlens. 4. The external cavity beam combining semiconductor laser fiber coupling module according to any one of claims 1-3, characterized in that the number of the single-tube semiconductor lasers (2) on the arc-shaped heat sink (3) is at least two. 5. The external cavity beam combining semiconductor laser fiber coupling module according to any one of claims 1-3, characterized in that the diffraction grating (7) is a transmission type diffraction grating or a reflection type diffraction grating. 6. The external cavity beam combining semiconductor laser fiber coupling module according to any one of claims 1-3, characterized in that, the external cavity mirror (8) is a parallel plate with a certain reflectivity, and the reflectivity value ranges from 1% to to 50%. 7. The external cavity beam combining semiconductor laser fiber coupling module according to claim 6, characterized in that the placement direction of the external cavity mirror (8) is strictly perpendicular to the direction of the diffracted beam. 8. The external cavity beam combining semiconductor laser fiber coupling module according to any one of claims 1-3, characterized in that the focusing lens (9) is a spherical lens, an aspheric lens or two separate cylindrical lenses. 9. The external cavity beam combining semiconductor laser fiber coupling module according to any one of claims 1-3, characterized in that the wavelength of the single-tube semiconductor laser (2) is from 400nm to 2000nm. 10. The external cavity beam combining semiconductor laser fiber coupling module according to any one of claims 1-3, characterized in that, the core diameter of the multimode fiber (10) ranges from 50 μm to 600 μm, and the numerical aperture ranges from 0.1 to 0.3, the optical power output is 1W~200W.

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