Semiconductor laser cavity-outside spectrum beam combining device

Abstract

The application discloses a kind of semiconductor laser extracavity spectrum beam combining devices, including the order of light path direction sequentially arranged spectrum synthesis semiconductor module, spectrum spread module and extracavity synthesis module;Wherein, spectrum synthesis semiconductor module and spectrum spread module one to one correspondence, constitute a beam combining unit, beam combining unit is at least two: spectrum synthesis semiconductor module, for the laser generated is carried out spectrum beam combining, exit to spectrum spread module;Spectrum spread module, for the laser received is spread and collimated, collimated laser is coupled into extracavity synthesis module after;Extracavity synthesis module is used for the laser coupled is carried out spectrum beam combining and output;Coupling is to be spliced according to wavelength by laser.The semiconductor laser extracavity spectrum beam combining device provided in the application greatly improves the number of beam combining light, improves the power of laser.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor lasers, and particularly relates to a cavity-outside spectrum beam combining device of a semiconductor laser. BACKGROUND

[0002] Compared with other types of lasers, semiconductor lasers have the advantages of long service life, high electro-optical conversion efficiency and wide wavelength range, and have become an important part of the modern laser field.

[0003] However, the low power, large divergence angle and poor beam quality of semiconductor lasers limit their application and development in some fields. SUMMARY

[0004] The application aims to provide a cavity-outside spectrum beam combining device of a semiconductor laser to improve the output power and the beam quality.

[0005] According to a first aspect of the application, a cavity-outside spectrum beam combining device of a semiconductor laser is provided, which comprises, in sequence along the light path direction, a spectrum combining semiconductor module, a spectrum spreading module and a cavity-outside combining module; wherein the spectrum combining semiconductor module and the spectrum spreading module correspond to each other to form a beam combining unit, and the beam combining unit is at least two: the spectrum combining semiconductor module is used for performing spectrum beam combining on the generated laser and emitting the laser to the spectrum spreading module; the spectrum spreading module is used for spreading and collimating the received laser, and the collimated laser is coupled into the cavity-outside combining module; the cavity-outside combining module is used for performing spectrum beam combining on the coupled laser and outputting the laser; and the coupling is to splice the laser according to the wavelength.

[0006] Further, the beam combining units are arranged in parallel according to the wavelength bands, and output equidistant parallel lasers, and in adjacent beam combining units, the upper limit of the output laser wavelength of one beam combining unit should be less than or equal to the lower limit of the output laser wavelength of the other beam combining unit, to directly form splicing in space.

[0007] Further, the cavity-outside spectrum beam combining device of the semiconductor laser further comprises a spectrum coupling module, the spectrum coupling module is a comb mirror, and the beam combining units are located on both sides of the comb mirror, the lasers generated by the beam combining units form a preset angle with the comb mirror, the reflected light and the transmitted light generated by the lasers generated by the beam combining units located on both sides of the comb mirror are output alternately and equidistantly in parallel after passing through the comb mirror, to form splicing and realize laser coupling.

[0008] Further, the lasers generated by the beam combining units located on both sides of the comb mirror and at symmetrical positions are located in the same wavelength band, the lasers generated by the beam combining units located on the same side of the comb mirror are adjacent in wavelength band, and in adjacent two beam combining units, the upper limit of the output laser wavelength of one beam combining unit should be less than or equal to the lower limit of the output laser wavelength of the other beam combining unit.

[0009] Further, the spectrum synthesis semiconductor module specifically comprises: semiconductor chips, a FAC, a first optical transformation element, a first diffraction optical element and an output coupling mirror arranged in sequence along the light path direction, the semiconductor chip contains only one light emitting unit, at least two semiconductor chips are arranged in sequence along the fast axis direction, and the arrangement interval is set according to requirements; the FAC is arranged at the focal length of the semiconductor chip, and is used for collimating the laser generated by the semiconductor chip; the first diffraction optical element is located at the focal plane of the first optical transformation element; the first optical transformation element and the first diffraction optical element are used for transmitting the received laser after beam combination to the output coupling mirror; and the output coupling mirror and the rear end surface of the light emitting unit of the semiconductor chip constitute a resonant cavity, and the output coupling mirror outputs the laser after beam combination.

[0010] Further, the spectrum synthesis semiconductor module generates laser with different wavelengths but in the same waveband.

[0011] Further, the distance between the light emitting units of the adjacent semiconductor chips is M millimeters, the spot size generated by the laser after passing through the FAC is N millimeters, and M>2N.

[0012] Further, the spectrum expansion module comprises a second diffraction optical element and a second optical transformation element, the second diffraction optical element is used for expanding the received light beam, and the second optical transformation element is used for collimating the expanded laser; the second diffraction optical element is a grating, and the first diffraction optical element is a dual grating.

[0013] Further, the cavity-out synthesis module specifically comprises: a third optical transformation element, used for transmitting the spliced laser to a third diffraction optical element, and the third diffraction optical element is located at the focal plane of the third optical transformation element and is used for outputting the spliced laser after beam combination.

[0014] Further, the first diffraction optical element, the second diffraction optical element and the third diffraction optical element form a predetermined included angle with the optical axis, and the included angle is determined by the incident angle and the diffraction angle in the following formula:

[0015] λ=d(sinα+sinβ)

[0016] Wherein, λ is the wavelength of the central waveband of the laser incident thereon, d is the groove pitch, α is the incident angle, and β is the diffraction angle.

[0017] The above technical solutions of the application have the following beneficial technical effects:

[0018] The semiconductor laser cavity-out spectral beam combining device provided by the above-mentioned embodiments of the present application further performs spectral beam combining outside the cavity again on the basis of the cavity-in beam combining of the spectral synthesis semiconductor module, greatly improving the beam combining scale; meanwhile, the semiconductor chip in the spectral synthesis semiconductor module of the present application only contains one light emitting unit, the plurality of semiconductor chips do not affect each other, and the output laser can only be formed by the light resonated by the resonant cavity of the spectral synthesis semiconductor module, avoiding the problem of spectral overlap in the cavity. From the spectral point of view, the spectrum of the spectral synthesis semiconductor module is a plurality of completely independent and uniformly spaced lasing wavelength peaks, without the existence of other secondary peaks, and the wavelength of the light emitting unit of the semiconductor chip can be well locked. The laser generated by the spectral synthesis semiconductor module is further combined outside the cavity, avoiding crosstalk during external cavity beam combining. Compared with simply increasing the number of beam combining units of the spectral beam combining module of the semiconductor laser, the quality of the obtained laser beam is better. Meanwhile, the different wavebands of the lasers generated by the plurality of spectral synthesis semiconductor modules are coupled according to the wavebands during beam combining, which further avoids the mutual influence between the lasers during beam combining, further improving the output power and beam quality of the laser. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structural schematic diagram of the semiconductor laser cavity-out spectral beam combining device of the present application;

[0020] Figure 2 is another structural schematic diagram of the semiconductor laser cavity-out spectral beam combining device of the present application;

[0021] Figure 3 is a structural schematic diagram of the semiconductor laser cavity-out spectral beam combining device containing four beam combining units. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the present application is further described in detail below in combination with specific embodiments and with reference to the drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0023] In the drawings, the schematic diagrams of layer structures according to the embodiments of the present application are shown. These drawings are not drawn to scale, in which certain details are exaggerated for the purpose of clarity, and certain details can be omitted. The shapes of various regions, layers shown in the drawings and their relative sizes, positional relationships are only exemplary, and in actuality, they can be deviated due to manufacturing tolerances or technical limitations, and the regions / layers with different shapes, sizes, relative positions can be additionally designed by the person skilled in the art according to actual needs.

[0024] Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0025] In the description of the present application, it should be noted that the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0026] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0027] The present application provides a kind of semiconductor laser cavity spectrum beam combination device, comprising: spectrum synthesis semiconductor module 1 is arranged in sequence along the direction of light path for the laser generated is carried out spectrum beam combination, forms a beam of combined light and exports to spectrum expansion module 2;Laser is same wave band and different wavelength, the laser generated is sequentially arranged in same wave band according to wavelength;

[0028] Spectrum expansion module 2, for the laser beam generated by spectrum synthesis semiconductor module 1 is carried out spectrum expansion and collimation, the laser spectrum after collimation is independent and the uniform interval of lasing wavelength peak, so as to realize the locking of wavelength;

[0029] Collimated laser, after coupling, enters cavity synthesis module 4, and cavity synthesis module 4 is used for carrying out spectrum beam combination and output to the laser after coupling.

[0030] Coupling is carried out by spectrum coupling module, or directly spliced in space according to wavelength.

[0031] In the present application, one spectrum synthesis semiconductor module 1 and one spectrum expansion module 2 correspond to each other, to form a combined beam unit for generating combined light, and the number of combined beam units is at least two.

[0032] In a specific embodiment:

[0033] As Figure 1As shown, the spectral synthesis semiconductor module 1 in the present application includes semiconductor chips 1-1, fast-axis collimation elements FAC 1-2, first optical transformation elements 1-3, first diffraction optical elements 1-4 and output coupling mirrors 1-5 arranged in sequence along the light path direction. Compared with the slow-axis, the semiconductor chip has a smaller divergence angle in the fast-axis direction and a better beam quality, so the present application chooses to combine beams in the fast-axis direction of the semiconductor chip. The spectral synthesis semiconductor module 1 contains at least two or more semiconductor chips 1-1, which are arranged in sequence along the fast-axis direction. The arrangement interval is set according to the need, and is preferably equal interval M millimeters. In order to further improve the beam combining quality and avoid crosstalk caused by multiple light emitting units in one semiconductor chip due to being in different planes, each semiconductor chip 1-1 contains only one light emitting unit. The rear end surface of the semiconductor chip 1-1 is coated with a high reflectivity film for output laser, and the front end surface is coated with an anti-reflection film for output laser. Preferably, the reflectivity of the high reflectivity film is greater than 99.8%, and the transmittance of the anti-reflection film is greater than 99.8%, so that the output laser of the light emitting unit is emitted through the front end surface. Here, the surface of the light emitting unit close to the FAC 1-2 is the front end surface, and the surface far away from the FAC 1-2 is the rear end surface. The laser emitted from the light emitting unit of the semiconductor chip 1-1 passes through the FAC 1-2 and then passes through the first optical transformation element 1-3. In order to achieve better collimation effect, the FAC 1-2 is arranged at the focal length of the semiconductor chip 1-1, and the laser forms a spot with a size of N millimeters after passing through the FAC 1-2. In order to ensure subsequent spectral sequential expansion and avoid crosstalk between spectra, and achieve better beam combining effect, the relationship M>2N needs to be met. In the present embodiment, the first optical transformation element 1-3 is coated with a high transmittance film for output laser, which is used to converge the output laser. Preferably, the transmittance of the first optical transformation element 1-3 is greater than 99.8%, and the first transformation optical element 1-3 can be a lens for convergence such as a cylindrical lens or a cylindrical lens group. The FAC 1-2 is coated with a high transmittance film for output laser with a transmittance greater than 99.8%. In a preferred embodiment, the thickness of the semiconductor chip light emitting area in the fast-axis direction is 1.2 μm-2 μm, the length of the semiconductor chip light emitting area gain region in the slow-axis direction is 1000 μm, and the FAC 1-2 is a short focal length cylindrical lens with a focal length of 0.5-1.2 millimeters.

[0034] The laser transmitted through the first optical transformation element 1-3 reaches the first diffraction optical element 1-4. In order to realize the beam combining of the laser by the first diffraction optical element 1-4, the first diffraction optical element 1-4 is located at the focal plane of the first optical transformation element 1-3. The inclination angle of the first diffraction optical element is determined by the following relationship:

[0035] λ=d(sinα+sinβ)--------Formula 1

[0036] Where λ is the center wavelength of the laser passing through the first diffractive optical element 1-4, d is the groove spacing of the first diffractive optical element 1-4, α is the incident angle, β is the diffraction angle, and the wavelength λ and groove spacing d are within the maximum separation angle range that the grating guarantees the diffraction power. The incident angle and diffraction angle of the corresponding laser and the grating can be determined, and then the tilt angle of the diffractive optical element can be determined. The tilt angle is the angle between the diffraction surface of the first diffractive optical element and the laser incident on its surface.

[0037] The combined laser beam is transmitted to the output coupling mirror 1-5, and after coupling by the output coupling mirror 1-5, it is output to the spectral expansion module 2. The coupling mirror 1-5 and the rear cavity surface of the semiconductor chip 1-1 form a resonant cavity, where the beam conforming to the dispersion relationship of the first diffractive optical element 1-4 and perpendicular to the output coupling mirror 1-5 oscillates. In this embodiment, the first diffractive optical element 4 is a grating, preferably a multilayer dielectric grating or a volume Bragg grating with a line density higher than 1000 lines / mm. The output coupling mirror 1-5 is coated with a film having a predetermined reflectivity for the output laser, preferably 7% to 30%.

[0038] The spectral unwrapping module 2, located in the output optical path of the spectral synthesis semiconductor module 1, includes a second diffractive optical element 2-1 and a second optical transformation element 2-2. The second diffractive optical element 2-1 and the first diffractive optical element 1-4 in the spectral synthesis semiconductor module 1 form a dual grating with the same parameters as the first diffractive optical element 1-4. This grating is used to unwrap the combined laser beam, which is then collimated by the second optical transformation element 2-2. The angle between the second diffractive optical element and the laser incident on its surface is also determined according to Formula 1, and will not be elaborated further here. The second optical transformation element 2-2 is coated with a film with high transmittance for the transmitted laser, with a transmittance greater than 99.8%. Preferably, the second optical transformation element 2-2 is an optical element such as a cylindrical lens or a group of cylindrical lenses that can achieve collimation.

[0039] In an optional embodiment, such as Figure 2 As shown, the laser combining units are arranged vertically in parallel order according to the output laser wavelength. The lasers are output in parallel with equal spacing, which is set as needed. The output lasers are directly spliced ​​in space according to their wavelengths, and in adjacent combining units, the upper limit of the output wavelength of one combining unit should be less than or equal to the lower limit of the output wavelength of another combining unit, thereby achieving laser coupling. Specifically, one combining unit outputs lasers in the wavelength range of 991nm to 1011nm, and the other combining unit outputs lasers in the wavelength range of 1011nm to 1031nm.

[0040] In an alternative embodiment, the semiconductor laser out-coupler further comprises a spectrum coupling module 3. In order to improve the quality of the beam combination and avoid crosstalk, two or more beam combination units are arranged on both sides of the spectrum coupling module 3. The beam combination units on both sides are symmetrically arranged with the spectrum coupling module as the axis. The laser generated by the beam combination units on both sides is in the same waveband. The laser generated by the beam combination units on the same side is in adjacent wavebands. That is, the highest wavelength of the laser generated by the spectrum synthesis semiconductor module 1 in one beam combination unit is less than the lowest wavelength of the laser generated by the spectrum synthesis semiconductor module 1 in another beam combination unit. As shown in Figure 1 The semiconductor laser out-coupler in the embodiment comprises two beam combination units arranged on both sides of the spectrum coupling module 3. The spectrum coupling module splices the laser according to the wavelength. Specifically, the two beam combination units on both sides of the spectrum coupling module 3 are symmetrically arranged with the spectrum coupling module as the axis. The waveband of the output laser is 965nm-978nm.

[0041] Preferably, the spectrum coupling module 3 is a comb mirror. The laser output by the beam combination unit on one side is reflected by the comb mirror. The laser output by the beam combination unit on the other side is transmitted by the comb mirror. The beam combination units on both sides form a predetermined angle with the comb mirror and are symmetrically arranged with the comb mirror as the axis. The reflected light and the transmitted light are alternately and equally spacedly output in parallel, so as to realize the laser coupling. Preferably, the beam combination units on both sides form a 45° angle with the comb mirror.

[0042] In another alternative embodiment, as shown in Figure 3As shown, the combiner includes four beam combining units, namely, beam combining unit 5, beam combining unit 6, beam combining unit 7 and beam combining unit 8, which are evenly distributed on both sides of the combiner. The beam combining units located on the same side of the combiner output laser beams of the same wavelength. For example, the beam combining unit 5 and the beam combining unit 7 output laser beams of the same wavelength, and the beam combining unit 6 and the beam combining unit 8 output laser beams of the same wavelength. The laser beams output by the beam combining units located on the same side of the combiner are sequentially arranged according to the wavelength. For example, the beam combining unit 5 and the beam combining unit 6 output laser beams of adjacent wavelengths, and the upper limit of the wavelength output by one of the beam combining units is less than or equal to the lower limit of the wavelength output by the other beam combining unit, so as to achieve good wavelength shift. Similarly, the beam combining unit 7 and the beam combining unit 8 output laser beams of the same wavelength, and the details are not described herein. Specifically, the beam combining unit 5 and the beam combining unit 7 output laser beams of the wavelength of 965 nm to 978 nm, and the beam combining unit 6 and the beam combining unit 8 output laser beams of the wavelength of 978 nm to 991 nm. The beam combining units on both sides form a predetermined angle with the combiner. The laser beams output by the two beam combining units on one side are reflected by the combiner, and the laser beams output by the two beam combining units on the other side are transmitted by the combiner. After passing through the combiner, the transmitted light and the reflected light of the same wavelength are output alternately and equidistantly in parallel. For example, the reflected light generated by the laser beam output by the beam combining unit 5 after passing through the combiner is output alternately with the transmitted light generated by the laser beam output by the beam combining unit 7 after passing through the combiner, and the output laser beams are parallel and equidistant. In this way, the influence between the light beams can be avoided, and the beam quality of the finally generated combined light can be improved. The number of beam combining units can be set according to actual needs.

[0043] As understood by those skilled in the art, the output laser beams of the beam combining units can be coupled by a spectral coupling module to realize laser splicing and laser coupling, as shown in Figure 1 Alternatively, the laser splicing and laser coupling can be realized by directly splicing the laser beams in space, as shown in Figure 2 Alternatively, the laser splicing and laser coupling can be realized by directly splicing the laser beams in space, as shown in Figure 3 Alternatively, the laser splicing and laser coupling can be realized by directly splicing the laser beams in space, as shown in

[0044] The transmission laser reaches the cavity-out synthesis module 4, and beam synthesis is performed again. The cavity-out synthesis module 4 comprises a third optical transformation element 4-1 and a third diffractive optical element 4-2. The third diffractive optical element 4-2 is located at the focal plane of the third optical transformation element 4-1. The diffraction surface of the third diffractive optical element 4-2 forms a preset included angle with the incident laser thereon. The included angle is determined by formula 1, which will not be described herein again. The third optical transformation element 4-1 is used for beam combining. The combined laser exits through the third diffractive optical element 4-2, thereby realizing the final combined laser output. Preferably, the third diffractive optical element 4-2 is a grating, in particular a multilayer dielectric grating or a volume Bragg grating with a line density higher than 1000 lines / mm. The light transmission surface of the third optical transformation element 4-1 is coated with a film having a predetermined transmittance for the output laser. The transmittance is greater than 99.8%.

[0045] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative, rather than limiting. Those skilled in the art can make many forms under the inspiration of the present application without departing from the scope of the present application and the scope protected by the claims, which all belong to the protection of the present application.

Claims

1. An extracavity spectral beam combining device for a semiconductor laser, characterized in that, The spectrum synthesis semiconductor module (1), the spectrum expansion module (2) and the out-cavity synthesis module (4) are sequentially arranged along the light path direction; The spectrum synthesis semiconductor module (1) and the spectrum expansion module (2) are one-to-one corresponding and constitute a beam combination unit, and the beam combination unit is at least two: The spectrum synthesis semiconductor module (1) is used for emitting the spectrum combined laser to the spectrum expansion module (2); the spectrum expansion module (2) is used for expanding and collimating the combined laser and coupling the collimated laser into the out-cavity synthesis module (4); the spectrum expansion module (2) comprises a second diffractive optical element (2-1) and a second optical transformation element (2-2); the second diffractive optical element (2-1) is used for expanding the received light beam; The second optical transformation element (2-2) is used for collimating the expanded laser; The out-cavity synthesis module (4) is used for combining the coupled laser and outputting; The out-cavity synthesis module (4) comprises a third optical transformation element (4-1) and a third diffractive optical element (4-2); The third optical transformation element (4-1) is used for transmitting the spliced laser to the third diffractive optical element (4-2), and the third diffractive optical element (4-2) is located on the focal plane of the third optical transformation element (4-1) and is used for combining and outputting the spliced laser; The spectrum coupling module (3) is a comb mirror, a plurality of the beam combination units are symmetrically arranged on both sides of the comb mirror, the laser output light paths of the beam combination units are at a preset angle with the comb mirror, and the reflected light and the transmitted light generated after the lasers output by the beam combination units on both sides pass through the comb mirror are output alternately and equidistantly in parallel to form splicing.

2. The semiconductor laser external cavity spectrum combining apparatus according to claim 1, wherein, The plurality of the beam combination units are sequentially and equidistantly arranged according to the wave bands, the plurality of the beam combination units collectively output equidistantly parallel lasers, and in the two adjacent beam combination units, the upper limit of the laser wavelength output by one beam combination unit should be less than or equal to the lower limit of the laser wavelength output by the other beam combination unit.

3. The semiconductor laser extracavity spectral beam combining apparatus of claim 2, wherein, The lasers output by the beam combination units on both sides of the comb mirror and at the symmetric positions are located in the same wave band, the wave bands of the lasers generated by the beam combination units on the same side of the comb mirror are adjacent, and in the two adjacent beam combination units, the upper limit of the laser wavelength output by one beam combination unit should be less than or equal to the lower limit of the laser wavelength output by the other beam combination unit.

4. The semiconductor laser extracavity spectral beam combining apparatus of claim 1 or 2, wherein, The spectrum synthesis semiconductor module (1) comprises a semiconductor chip (1-1), an FAC (1-2), a first optical transformation element (1-3), a first diffractive optical element (1-4) and an output coupling mirror (1-5) which are sequentially arranged along the light path direction; The semiconductor chip (1-1) only contains one light emitting unit, and a plurality of the semiconductor chips (1-1) are sequentially arranged along the fast axis direction; The FAC (1-2) is arranged at the focal length of the semiconductor chip (1-1) and is used for collimating the laser generated by the semiconductor chip (1-1); The first diffractive optical element (1-4) is located at the focal plane of the first optical transformation element (1-3); The first optical transformation element (1-3) and the first diffractive optical element (1-4) are used for transmitting the received laser after beam combination to the output coupling mirror (1-5); The output coupling mirror (1-5) and the rear end surface of the light emitting unit of the semiconductor chip (1-1) constitute a resonant cavity, and the output coupling mirror (1-5) outputs the laser after beam combination.

5. The semiconductor laser external cavity spectrum combining apparatus according to claim 1, wherein, The spectral synthesis semiconductor module (1) is used for generating lasers with different wavelengths but in the same waveband.

6. The semiconductor laser external cavity spectrum combining apparatus according to claim 4, wherein, The distance between the light emitting units of the two adjacent semiconductor chips (1-1) is M millimeters, and the spot size generated by the laser after passing through the FAC (1-2) is N millimeters, wherein M>2N.

7. The semiconductor laser out-of-cavity spectral beam combination device according to claim 4, characterized in that, The second diffractive optical element (2-1) is a grating, and the second diffractive optical element (2-1) and the first diffractive optical element (1-4) are a pair of grating.

8. The semiconductor laser extracavity spectral beam combining apparatus of claim 7, wherein, The first diffractive optical element (1-4), the second diffractive optical element (2-1) and the third diffractive optical element (4-2) form a predetermined angle with the optical axis, and the incident angle and the diffraction angle in the following formula determine the angle: λ=d(sinα+sinβ) Wherein: λ is the wavelength of the central waveband of the laser, d is the groove spacing, α is the incident angle, and β is the diffraction angle.

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