CN115327788B - Spectrum beam combining device and method - Google Patents
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Abstract
The invention relates to the technical field of laser, in particular to a spectrum beam combining device and a method, wherein the spectrum beam combining device comprises a laser unit, a conversion lens, a reflection grating, a transmission grating and an external cavity mirror; the spectrum beam combining device takes the Littrow angle of the normal line of the transmission grating as an optical axis, the number of the laser units is two or more, and the two or more laser units are respectively positioned at two sides of the optical axis; the external cavity mirror is perpendicular to the optical axis. The spectrum beam combining device reduces the outline dimension of the spectrum beam combining light source on the premise of not degrading the spectrum beam combining light source, so that the structure is more compact and practical, and meanwhile, the outer cavity mirror is designed to the center position of the spectrum beam combining light source through the structural characteristics, so that the stability of the outer cavity mirror is improved, and the reliability and stability of the spectrum beam combining light source are further improved.
Description
Technical Field
The invention relates to the technical field of lasers, in particular to a spectrum beam combining device and method.
Background
Spectral beam combining technology is currently one of the most feasible techniques for achieving high-power, high beam quality beam combining lasers. From 1999 to date, this technology has been successfully applied to all solid state lasers, fiber lasers, and semiconductor lasers, greatly improving laser performance.
The spectrum beam combining structure currently applied to the field of semiconductor laser is mainly a closed-loop spectrum beam combining structure, and the implementation structure is as follows: the back cavity surface of the laser unit and the outer cavity mirror form a resonant cavity, the front cavity surface of the laser unit is plated with an antireflection film, the antireflection film is arranged in the spectrum beam combining direction and is emitted along the same direction, the laser unit and the outer cavity mirror are jointly incident on the grating under the action of the conversion lens, and then are output to the outer cavity mirror through grating diffraction, so that only light which vertically enters the outer cavity mirror and can be reflected back to the original laser unit can resonate. Due to the effects of grating and external cavity feedback, the laser unit resonates to different laser wavelengths, the laser power after spectrum beam combination is multiplied, the beam quality is consistent with that of the laser unit, but the whole spectrum is widened.
In order to achieve a good spectrum beam combination effect, the light emitting end face of the laser chip and the grating are respectively positioned on front and back focal planes of the conversion lens, namely the distance from the laser chip to the grating is at least twice the focal length of the conversion lens. In addition, no matter the spectrum beam combination structure based on the reflection grating or the spectrum beam combination structure based on the transmission grating, the output light path is not overlapped with the incident light path after grating diffraction, so that the output laser needs to occupy additional space, and the size of the spectrum beam combination structure is further increased. And the external cavity mirror is typically located at the periphery or edge of the spectrally combined light source.
In order to realize effective spectrum beam combination in a proper spectrum range, the current literature generally reports that the focal length of a conversion lens adopted by a near infrared band spectrum beam combination light source is hundreds of millimeters, and in order to compress bandwidth, the focal length of the conversion lens even reaches the order of meters, so that the resonant cavity of an external cavity spectrum light source generally reaches hundreds of millimeters or even a plurality of meters, and the volume size of the whole spectrum beam combination light source is larger.
In addition, the rear cavity mirror serving as the resonant cavity mirror is always positioned at the periphery or the edge of the light source, so that the structural stability of the rear cavity mirror is difficult to ensure, and great hidden danger is brought to the structural stability and long-term reliability of the whole spectrum beam combining light source, and the rear cavity mirror is particularly applied to occasions with high requirements on environmental adaptability.
Disclosure of Invention
The invention aims to solve the problems and provide a spectrum beam combining device and method with more compact structure.
The invention provides a spectrum beam combining device, which comprises a laser unit, a conversion lens, a reflection grating, a transmission grating and an external cavity mirror, wherein the reflection grating is arranged on the laser unit; the spectrum beam combining device takes the Littrow angle of the normal line of the transmission grating as an optical axis, the number of the laser units is two or more, and the two or more laser units are respectively positioned at two sides of the optical axis; the outer cavity mirror is perpendicular to the optical axis;
the laser unit outputs laser beams, the laser beams are acted by the transformation lens and are incident to the transmission grating at different angles, and the laser beams are diffracted by the transmission grating and then are incident to the reflection grating; and the laser beam is output to the external cavity mirror after being diffracted by the transmission grating and the reflection grating.
Preferably, the transformation lens includes a through hole having a diameter equal to or smaller than a diameter of the laser beam diffracted to the external cavity mirror through the transmission grating and the reflection grating; the center of the through hole coincides with the optical axis.
Preferably, the front cavity surface of the laser unit is located at the front focal surface of the conversion lens.
Preferably, the front cavity surface of the laser unit is located in the focal length doubling range of the conversion lens, and the spectrum beam combining device further comprises a compensation mirror, wherein the compensation mirror and the conversion lens are combined to form an imaging mirror, and the front cavity surface of the laser unit is imaged to the outer cavity mirror.
Preferably, the reflection grating is a first-order diffraction grating, the first-order diffraction efficiency of the reflection grating is greater than 90%, and the diffraction polarization direction of the reflection grating is matched with the polarization direction of the laser beam.
Preferably, the transmission grating is a negative first-order diffraction grating, the negative first-order diffraction efficiency of the transmission grating is greater than 90%, and the diffraction polarization direction of the transmission grating is matched with the polarization direction of the laser beam.
Preferably, two or more of the laser units output laser beams of different wavelengths, respectively.
Preferably, the laser unit comprises a laser device and an optical element, the optical element performs at least one of collimation, shaping or polarization direction adjustment on a laser beam output by the laser device, and the laser device is coated with an antireflection film on the end face of the output laser beam; the laser device is a semiconductor laser, a fiber laser or an all-solid-state laser.
The invention also provides a spectrum beam combining method which is realized by the spectrum beam combining device, and the spectrum beam combining method comprises the following steps:
S1, the spectrum beam combining device takes a Littrow angle of a normal line of the transmission grating as an optical axis; the laser units are positioned on two sides of the optical axis; the laser unit outputs a laser beam;
S2, the laser beam is incident to the transmission grating at different angles under the action of the transformation lens,
S3, the laser grating is diffracted by the transmission grating and then is incident to the reflection grating for diffraction;
s4, the laser beam is output to the external cavity mirror after being diffracted for many times by the transmission grating and the reflection grating; the external cavity mirror is perpendicular to the optical axis.
The spectrum beam combining device and the method provided by the invention have the following outstanding effects:
(1) Higher spectral beam combining efficiency. The grating is used as a key element of spectrum beam combination, the diffraction efficiency of the grating directly determines the spectrum beam combination efficiency, and in the spectrum beam combination device structure, all gratings realize diffraction under the Littrow diffraction angle, so that the highest diffraction efficiency can be achieved by the grating, and the spectrum beam combination structure has higher spectrum beam combination efficiency;
(2) A more compact structure. The multiple of the dispersion capacity of the dispersion element is increased by multiplexing the transmission grating and the reflection grating, the same spectrum combination bandwidth can be realized by adopting a short-focus conversion lens, and the correspondingly formed spectrum combination resonant cavity is greatly shortened, so that the overall size of the spectrum combination light source is reduced, and meanwhile, the light path after diffraction of the grating and the external cavity mirror are overlapped with an incident light path, so that the light path does not occupy additional space, the light source size is further reduced, and a more compact structure is realized;
(3) Higher environmental adaptability and stability. The high spectrum beam combining efficiency enables the laser to have higher effective external cavity feedback rate, and resonance is easier even if the resonant cavity has small mismatch; the compact structure of the whole light source is more beneficial to the stability of the whole light source; the most critical point is that the external cavity mirror is designed into the resonant cavity, so that the structure stability is higher, and the reliability and stability of the spectrum beam combining light source are improved.
Drawings
Fig. 1 is a schematic structural view of a spectrum combining device according to a first embodiment of the present invention.
Fig. 2 is a schematic structural view of a spectrum combining device according to a second embodiment of the present invention.
Fig. 3 is a schematic diagram of a transmission grating structure in a spectral beam combining device according to an embodiment of the present invention.
Fig. 4 is a schematic structural view of a spectrum combining device of a first comparative example in the prior art.
Fig. 5 is a schematic structural view of a spectrum combining device of a second comparative example in the prior art.
Reference numerals
1001. Optical axis, 100, laser unit array, 101, first laser unit, 102, second laser unit, 2001, first order diffraction direction, 20, conversion lens, 30, transmission grating, 301, first transmission grating, 302, second transmission grating, 303, third transmission grating, 30N, nth transmission grating, 40, reflection grating, 50, external cavity mirror, 60, compensation mirror, 70, and collimator mirror.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limiting the invention.
Referring to fig. 1, a schematic structure of a spectrum combining device according to a first embodiment of the present invention is shown, where the spectrum combining device includes a laser unit, a conversion lens 20, a reflection grating 40, a transmission grating 30, and an external cavity mirror 50; the spectrum beam combining device takes the Littrow angle of the normal line of the transmission grating as an optical axis 1001, two laser units are adopted, namely a first laser unit 101 and a second laser unit 102, the laser units are not placed at the position of the optical axis 1001, and the two laser units are respectively positioned at two sides of the optical axis 1011; in a preferred embodiment, two laser units are symmetrically arranged on both sides of the optical axis 1011, and output laser beams along the same direction z; the outer endoscope 50 is perpendicular to the optical axis 1001; it should be noted that, in order to better describe the solution of the present invention, the optical axis 1001 is introduced, but the optical axis 1001 is not actually present, but is merely an axis similar to a coordinate axis for illustration.
The laser unit outputs a laser beam, the laser beam is acted by the conversion lens 20, is incident to the transmission grating 30 at different angles, is diffracted by the transmission grating 30, and then is incident to the reflection grating 40; the laser beam is output to the external cavity mirror after being diffracted by the transmission grating 30 and the reflection grating 40; specifically, the laser beams output by the first laser unit 101 and the second laser unit 102 are incident on different positions of the transmission grating 30 at different angles, and are diffracted at different angles, and the incident angle and the diffraction angle of the laser beams satisfy the grating equation of the transmission grating 30. After multiple diffractions, the laser beam is incident on the same position on the transmission grating 30 and then diffracted in the same direction at the last diffraction. The incidence angle of the optical axis 1001 on the transmission grating 30 is a littrow angle, the laser beams are diffracted by the transmission grating 30, then are further incident on the reflection grating 40 at the littrow angle, are diffracted by the reflection grating 40, then are returned along the original path to be incident on the transmission grating 30 at the littrow angle, the laser beams output by the first laser unit 101 and the second laser unit 102 are overlapped on the transmission grating 30, and finally are diffracted by the transmission grating 30 along the same direction, and the diffraction direction is overlapped with the optical axis 1001 and is incident on the external cavity mirror 50 perpendicular to the optical axis. The first laser unit 101 and the second laser unit 102 may output laser beams of different wavelengths; each laser unit resonates to different wavelengths through the feedback of the external cavity mirror 50 and the dispersion action of the transmission grating 30 and the reflection grating 40, the light spot and the divergence angle output by the external cavity mirror 50 are consistent with the unit light beam, and the power is the sum of the powers of all the laser units.
In a specific embodiment, the laser beam output by the laser unit includes a chief ray, and the chief ray specifically refers to a ray parallel to the optical axis 1001 output from each laser unit; the principal rays output by each laser unit are symmetrically distributed on two sides of the transmission grating 30 and the reflection grating 40 in the Littrow angle direction, and after the laser beams are diffracted by the transmission grating 30 and the reflection grating 40, when diffraction occurs for the last time, the principal rays output by all laser units are coincident with the Littrow angle direction of the last grating.
The incidence angle and the diffraction angle of the principal ray and the transmission grating are Littrow angles; the incidence angle and the diffraction angle of the main light ray and the reflection grating are all littrow angles. In other embodiments, the number of the laser units may be other, for example, three, four, five, six, etc., and these laser units are all distributed on two sides of the optical axis 1001, where the optical axis 1001 is located, and no laser unit is provided, and in a preferred embodiment, different laser units are symmetrically arranged on two sides of the optical axis 1001, so as to achieve the highest diffraction efficiency; the laser units at different positions can output laser beams with different wavelengths.
In a specific embodiment, the transforming lens 20 includes a through hole, and the diameter of the through hole is smaller than or equal to the diameter of the laser beam diffracted to the external cavity mirror 50 by the transmission grating 30 and the reflection grating 40, so as to scatter and filter the laser beam exceeding the aperture of the through hole; the center of the through hole coincides with the optical axis 1001; i.e. the through holes may directly pass the laser beam diffracted from the transmission grating 30 and the reflection grating 40 to the external cavity mirror 50.
In a specific embodiment, the front facet of the laser unit is located at the front focal plane of the conversion lens 20. In another specific embodiment, the front cavity surface of the laser unit is located within the focal length doubling range of the conversion lens 20, the spectrum beam combining device further comprises a compensation mirror 60, and the compensation mirror 60 and the conversion lens 20 are combined to form an imaging mirror to image the front cavity surface of the laser unit to the external cavity mirror 50; the compensation mirror 60 may be a positive lens or a negative lens.
As shown in fig. 2, in this embodiment, the front facet of the laser unit is not located at the front focal plane of the conversion lens 20, but is within a double focal length, and the laser beam diffracted by the transmission grating 30 and the reflection grating 40 is not collimated light, and the combination of the conversion lens 20 and the compensation mirror 60 images the end face of the laser unit onto the external cavity mirror 50, so that the overall size of the spectral beam combining light source can be further reduced when resonance is achieved.
In a specific embodiment, the reflection grating 40 is a first-order diffraction grating, the first-order diffraction efficiency of the reflection grating 40 is greater than 90%, and the high-efficiency diffraction polarization direction of the reflection grating 40 is matched with the polarization direction of the laser beam. The transmission grating 30 is a negative-order diffraction grating, the negative-order diffraction efficiency of the transmission grating 30 is greater than 90%, and the high-efficiency diffraction polarization direction of the transmission grating 30 is matched with the polarization direction of the laser beam. The transmission grating 30 and the reflection grating 40 may have the same grating constant or different grating constants, and only needs to meet the littrow angle incidence and diffraction of the corresponding grating, and the optical path of the laser beam may return to output along the optical axis direction.
In other embodiments, the number of the transmission gratings 30 is two or more, that is, a combination of multiple transmission gratings, and as shown in fig. 3, the number of the transmission gratings 30 is multiple, that is, a combination of multiple negative-order diffraction gratings, including a first transmission grating 301, a second transmission grating 302, a third transmission grating 303 …, and an nth transmission grating 30N, where the negative-order diffraction efficiency of each transmission grating is greater than 90% and the adjacent transmission gratings are not parallel to each other. In the combination scheme of a plurality of transmission gratings, each transmission grating can have the same grating constant or different grating constants, when the grating constants are the same, the angles of the incident angle and the diffraction angle are the same, and when the grating constants are different, the incident angle and the diffraction angle of each transmission grating are the same; each transmission grating is within a double focal length range of the conversion lens 20, and an included angle between the (N-1) -th transmission grating and the N-th transmission grating 30N is (θ L(N-1)+ θLN), where θ L(N-1) is the littrow angle of the (N-1) -th transmission grating, and θ LN is the littrow angle of the N-th transmission grating 30N.
In a specific embodiment, the laser unit includes a laser device and an optical element, the optical element performs at least one of collimation, shaping or polarization direction adjustment on a laser beam output by the laser device, and the laser device is coated with an antireflection film on an end face of the output laser beam; the laser device is a semiconductor laser, a fiber laser or an all-solid-state laser.
The invention further provides a spectrum beam combining method, which comprises the following steps:
S1, the spectrum beam combining device takes a Littrow angle of a normal line of the transmission grating as an optical axis; the laser units are positioned on two sides of the optical axis; the laser unit outputs a laser beam;
S2, the laser beam is incident to the transmission grating at different angles under the action of the transformation lens,
S3, the laser grating is diffracted by the transmission grating and then is incident to the reflection grating for diffraction;
s4, the laser beam is output to the external cavity mirror after being diffracted for many times by the transmission grating and the reflection grating; the external cavity mirror is perpendicular to the optical axis.
The compact and high-reliability spectrum beam combining device and method provided by the invention have the advantages that firstly, the transmission grating and the reflection grating are multiplexed, the dispersion capacity of the dispersion element is improved, and the focal length of the conversion lens can be reduced by several times under the condition that the number of laser units and the spectrum beam combining bandwidth are not changed, so that the resonant cavity and the overall dimension of the whole spectrum beam combining light source are reduced. Meanwhile, whether the transmission grating or the reflection grating is adopted, the Littrow angle is used as an incident angle and a diffraction angle, so that maximization of grating efficiency is facilitated, effective feedback quantity is improved, stable external cavity resonance is established, and resonance stability of the spectrum beam combination light source is improved. In addition, through the light path design, the grating diffraction output light and the incident laser light path are overlapped, the outer cavity mirror is positioned in the middle of the light path, the structural stability of the outer cavity mirror is easy to keep, the outer cavity mirror is not easily influenced by external environment, and the reliability of the spectrum beam combining light source is improved so as to meet the application requirements of special environments.
Further description will be given below with reference to specific comparative examples and examples.
Comparative example 1
Reference (B.Chann,R.K.Huang,L.J.Missaggia,et al. Near-diffraction-limited diode laser arrays by wavelength beam combining[J].optics letters,2005,30(16):2104-2106) reports a structure for spectral beam combination based on a reflection grating, in which an external cavity mirror 50 and a rear cavity surface of a laser unit array 100 form a resonant cavity, and a front cavity surface of the laser unit array 100 and the reflection grating 40 are located on front and rear focal planes of a conversion lens 20, respectively. After the laser unit is acted by the conversion lens 20 with the focal length f, the laser unit is incident on the reflection grating 40 at different angles, and then is diffracted by the reflection grating 40, the diffracted laser beam is output to the external cavity mirror 50, and only the light vertically incident on the external cavity mirror 50 can return to the original laser unit to form resonance. The incident laser beam and the diffracted laser beam of the reflection grating 40 are separated, and in order to achieve high grating diffraction efficiency, the separation angle of the two is small (< 10 °) and is close to the littrow angle of the grating, respectively. Each laser unit resonates to different wavelengths through the feedback of the external cavity mirror 50 and the grating dispersion, the light spot and the divergence angle output by the external cavity mirror 50 are consistent with the unit light beam, and the power is the sum of the powers of all the laser units. Specifically, as shown in fig. 3, a conversion lens 20 with a focal length of 200mm is used to perform beam conversion on 915nm laser units with an antireflection (R < 1%) of 100 front cavity surfaces, a reflection grating 40 with a grating period of 1800 lines/mm is used to perform diffraction, and then an external cavity mirror 50 with a reflectivity of 10% is used to perform feedback to realize spectrum beam combination, and the output spectrum after beam combination is 17nm. As can be seen from the figure, the light exit surface of the laser chip is at least 400mm from the grating. It is explicitly mentioned in the content of this document that "For best efficiency the incidence angle on the grating is limited to several degrees around the Littrow angle",, i.e. the angle of incidence and the angle of diffraction of the reflection grating 40 deviate from the littrow angle of the grating, which is limited to a few degrees as much as possible for good efficiency, and specific values are not reported, while it is known from the text that the direction of light transmission diffracted by the reflection grating 40 does not coincide with the incident light, that the physical dimension is increased in the X-direction, and that the external cavity mirror 50 is not included inside the spectral beam-combining structure.
Example 1
Based on the principle shown in fig. 4, the spectrum beam combining device structure of the present invention specifically adopts a combination of 2 transmission gratings 30 and 1 reflection grating 40, the number of grating lines of the transmission gratings 30 and the reflection gratings 40 is 1800 lines/mm, the same 17nm combined spectrum bandwidth is maintained, the focal length f of the conversion lens 20 can be reduced to 67mm, the physical distance from the laser chip to the last transmission grating is directly reduced to 134mm without considering the folding effect of the transmission grating 30 and the reflection grating 40 on the light path, and the folding effect of the transmission grating 30 and the reflection grating 40 is superimposed, and the physical distance is shorter, namely, the space dimension in the Z direction is at least changed to 1/3 of the original space dimension. At the same time, the diffracted light path overlaps the incident laser beam and places the reflection grating 40 next to the transmission grating 20, without considering the increase in space in the X direction, so that the size of the combined light source becomes smaller, either from the X or Z direction. If a combination of 3 transmissive gratings and 1 reflective grating is used, the conversion lens focal length can be reduced to 40mm. In addition, in this embodiment, the external cavity mirror 50 can be directly designed into the optical path, which significantly enhances the structural stability of the spectrum combination.
Comparative example 2
Reference (Jun Zhang,Hangyu Peng,Xihong Fu,et al.CW 50W/M2 ＝10.9diode laser source by spectral beam combining based on a transmission grating[J].optics express,2013,21(3):3627-3632) reports a structure for spectral beam combination based on a transmission grating, in which an external cavity mirror 50 and a rear cavity surface of a laser unit array 100 form a resonant cavity, and a front cavity surface of the laser unit array 100 and the transmission grating 30 are located on front and rear focal planes of a conversion lens 20, respectively. The laser beams output by the laser unit array 100 are acted by the collimating lens 70 with focal lengths f f and f s and then are incident on the transmission grating 30 with different angles after being acted by the conversion lens 20 with focal length f t, wherein the incidence angle of the laser beams output by the laser units in the middle position of the laser unit array 100 is the same as the littrow angle of the transmission grating, and specifically, as shown by the first-order diffraction direction 2001 in the figure, the laser beams are diffracted by the transmission grating 30, the diffraction beams coincide with the littrow angle direction of the transmission grating, the diffracted light is output to the external cavity mirror 50, and only the laser beams vertically incident on the external cavity mirror 50 can return to the original laser units to form resonance. The incident laser beam and the diffracted laser beam of the transmission grating 30 are separated, and in order to achieve high grating diffraction efficiency, the incident angle and the diffraction angle of the transmission grating 30 are both Littrow angles (θlittrow) of the grating, and the included angle between the incident laser beam and the diffracted laser beam is 180-2×θlittrow, in this document, θlittrow is 50.6 °, and the included angle between the incident laser beam and the diffracted laser beam is 78.8 °.
Specifically, as shown in fig. 5, a conversion lens 20 with a focal length of 150mm is used for carrying out beam conversion on 970nm laser units with anti-reflection (R < 0.5%) on 19 front cavity surfaces, a transmission grating 30 with a grating period of 1600 lines/mm is used for carrying out diffraction, and then an external cavity mirror 50 with a reflectivity of 20% is used for carrying out feedback to realize spectrum beam combination, and the output spectrum after beam combination is 24.1nm. As can be seen from the figure, the light exit surface of the laser chip is at least 300mm from the transmission grating 30. Although the angles of the incident laser beam and the diffracted laser beam and the transmission grating 30 are littrow angles, high diffraction efficiency can be obtained, the included angle of the incident laser beam and the diffracted laser beam reaches 78.8 degrees, almost forms a right angle, so that the whole light source structure occupies a large space, if the distance between the external cavity mirror 50 and the transmission grating 30 is 100mm, the dimension of nearly 100mm is directly increased in the X direction, and the external cavity mirror 50 is completely positioned at the far end of the spectrum beam combining structure, so that a stable structure is not easy to realize.
Example 2
Based on the principle shown in fig. 5, the spectrum beam combining device structure of the present invention, specifically referring to the structure shown in fig. 1, adopts the combination of the monolithic transmission grating 30 and the monolithic reflection grating 40, the number of grating lines of the transmission grating 30 and the reflection grating 40 is 1600 lines/mm, the same 24.1nm combined spectrum bandwidth is maintained, the focal length of the conversion lens 20 can be reduced to 50mm, the physical distance from the laser chip to the last transmission grating 30 is directly reduced to 100mm without considering the folding effect of the transmission grating 30 and the reflection grating 40 on the light path, and the folding effect of the transmission grating 30 and the reflection grating 40 is superimposed, wherein the physical distance is shorter, i.e. the spatial dimension in the Z direction is at least changed to 1/3 of the original spatial dimension. Meanwhile, the diffracted light path and the incident laser light form superposition, and the reflection grating 40 and the transmission grating 30 are placed next to each other, so that the size of the direction is greatly reduced without considering the increase of the space in the X direction, and therefore, the size of the beam combining light source becomes smaller no matter from the X direction or the Z direction. If more transmission gratings 30 are used, such as a combination of multiple transmission gratings, the overall spectral beam-combining structure may be further reduced in size. In addition, in this embodiment, the external cavity mirror 50 can be directly designed into the optical path of the laser beam, so that the stability of the external cavity mirror is greatly improved compared with the structure shown in fig. 5, and the structural stability of the spectrum combination is obviously enhanced.
While embodiments of the present invention have been illustrated and described above, it will be appreciated that the above described embodiments are illustrative and should not be construed as limiting the invention. Variations, modifications, alternatives and variations of the above-described embodiments may be made by those of ordinary skill in the art within the scope of the present invention.
The above embodiments of the present invention do not limit the scope of the present invention. Any other corresponding changes and modifications made in accordance with the technical idea of the present invention shall be included in the scope of the claims of the present invention.
Claims (9)
1. The spectrum beam combining device is characterized by comprising a laser unit, a conversion lens, a reflection grating, a transmission grating and an external cavity mirror; the spectrum beam combining device takes the Littrow angle of the normal line of the transmission grating as an optical axis, the number of the laser units is two or more, and the two or more laser units are respectively positioned at two sides of the optical axis; the outer cavity mirror is perpendicular to the optical axis;
the laser unit outputs laser beams, the laser beams are acted by the transformation lens and are incident to the transmission grating at different angles, and the laser beams are diffracted by the transmission grating and then are incident to the reflection grating; and the laser beam is output to the external cavity mirror after being diffracted by the transmission grating and the reflection grating.
2. The spectral beam combining apparatus according to claim 1, wherein the conversion lens includes a through hole having a diameter equal to or smaller than a diameter of the laser beam diffracted to the external cavity mirror through the transmission grating and the reflection grating; the center of the through hole coincides with the optical axis.
3. The spectral beam combining apparatus of claim 1, wherein a front facet of the laser unit is located at a front focal plane of the conversion lens.
4. The spectral beam combining apparatus of claim 1, wherein the front facet of the laser unit is located within a focal length of one of the conversion lenses, the spectral beam combining apparatus further comprising a compensation mirror, the compensation mirror in combination with the conversion lenses forming an imaging mirror, the front facet of the laser unit being imaged to the external cavity mirror.
5. The spectral beam combining apparatus of claim 1, wherein the reflection grating is a first order diffraction grating, the reflection grating has a first order diffraction efficiency greater than 90%, and the diffraction polarization direction of the reflection grating matches the polarization direction of the laser beam.
6. The spectral beam combining apparatus of claim 1, wherein the transmission grating is a negative first order diffraction grating, the negative first order diffraction efficiency of the transmission grating is greater than 90%, and the diffraction polarization direction of the transmission grating matches the polarization direction of the laser beam.
7. The spectral beam combining apparatus of claim 1, wherein two or more of the laser units output laser beams of different wavelengths, respectively.
8. The optical spectrum beam combining apparatus as claimed in claim 1, wherein the laser unit comprises a laser device and an optical element, the optical element performs at least one of collimation, shaping or polarization direction adjustment on the laser beam output by the laser device, and the laser device is coated with an antireflection film on an end face of the output laser beam; the laser device is a semiconductor laser, a fiber laser or an all-solid-state laser.
9. A method of spectral beam combination, characterized in that it is achieved by a spectral beam combination device according to any one of claims 1 to 8, comprising the steps of:
S1, the spectrum beam combining device takes a Littrow angle of a normal line of the transmission grating as an optical axis; the number of the laser units is two or more, and the laser units are positioned on two sides of the optical axis; the laser unit outputs a laser beam;
S2, the laser beam is incident to the transmission grating at different angles under the action of the transformation lens,
S3, the laser grating is diffracted by the transmission grating and then is incident to the reflection grating for diffraction;
s4, the laser beam is output to the external cavity mirror after being diffracted for many times by the transmission grating and the reflection grating; the external cavity mirror is perpendicular to the optical axis.
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| WO2019205500A1 (en) * | 2018-04-28 | 2019-10-31 | Ii-Vi Suwtech Inc. | Semiconductor laser beam combining device |
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