Transverse chirp Bragg grating multi-single-tube external cavity laser module beam combining device

Abstract

The utility model discloses a transverse chirp Bragg grating multi-single-tube external cavity laser module beam combining device which comprises at least three light-emitting modules and diffraction gratings which are arranged in an arc shape, and all the light-emitting modules project light to the diffraction gratings. A focusing optical element close to the light-emitting module and a slow-axis collimation optical element close to the diffraction grating are arranged on a light path between the light-emitting module and the diffraction grating, and after light projected by all the light-emitting modules passes through the focusing optical element and the slow-axis collimation optical element, independent light beams are output by the diffraction grating. According to the device, the wavelength locking of each single-tube semiconductor laser in the beam combining device can be actively and quickly realized by utilizing the transverse chirped volume Bragg grating without heating.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor lasers, in particular to a transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device. Background Art

[0002] The significant advantages of semiconductor lasers are compact structure, small size, long life and high electro-optical conversion efficiency, but the divergence angle of the output beam is generally large and the spatial brightness is low. Some applications in the field of material processing require both high-power and high-beam-quality laser output. When semiconductor lasers are used as pump sources, there are also strict requirements for brightness and wavelength. However, traditional semiconductor laser technologies such as spatial beam combining and polarization beam combining can quickly increase power but cannot significantly improve beam quality. Dense wavelength beam combining can increase the output power of the laser while ensuring high beam quality. Dense wavelength beam combining uses a combination of diffraction elements such as gratings and external cavity mirrors to lock each light-emitting unit at different wavelengths. Sub-beams of different wavelengths are diffracted on the grating into a combined output beam. The diffraction effect of the grating allows the incident light to overlap spatially in the far field and near field. The beam quality of the combined laser beam is similar to that of a single beam combining unit, and the power is the sum of all beam combining units.

[0003] There are many structures that have been reported to use the principle of spectral beam combining to improve the output power and beam quality of semiconductor lasers. Most of these structures use partial reflectors as external cavity mirrors, one side is coated with a reflective film with a reflectivity of 1%-30%, and the other side is coated with an anti-reflection film. The reflector can transmit part of the laser beam, and the other part is reflected in the original path to form external cavity feedback with a single-tube semiconductor laser. However, this traditional structure is difficult to achieve high-power dense beam combining. If the output power is to be increased, the number of single-tube semiconductor lasers needs to be further increased. In order not to increase the size of the device, a common practice is to further reduce the spacing between single-tube lasers in a multi-single-tube semiconductor laser array to increase the number of lasers so that the device can combine more single-tube semiconductor lasers. Under such conditions, relying on reflector reflection to achieve wavelength-locked beam combining can easily lead to feedback crosstalk between each single-tube semiconductor laser, and the quality of the combined beam is reduced.

[0004] In addition, in recent years, there have been reports that the feedback method of Bragg grating (VBG grating) is used to actively achieve wavelength locking of each semiconductor laser unit in the module, so that dense beam can be achieved without the need for a reflector as an external cavity mirror. Specifically, the application number is 201420068597.9, the publication number is CN204067850, and the name is a beam combining device for a semiconductor laser tube core, including multiple semiconductor laser tube cores and fast axis collimating lenses, Bragg volume gratings, fast and slow axis collimating lenses, holographic gratings and beam conversion lens groups arranged on the output optical path of the semiconductor laser tube core. The back of the Bragg volume grating is placed with a fast and slow axis straight through #, so that the laser beams from each semiconductor laser tube core are diffracted to the same direction on the +1 order diffraction stripes, realizing multi-tube core semiconductor laser beam combining. The beam combining technology provides the wavelength stability of each semiconductor laser tube core and also improves the working stability of the entire system. The beam combining technology provides a new method and path for realizing high-brightness and high-power direct semiconductor laser systems. In addition, the Chinese patent application number is 201910569713.2, the authorization announcement number is CN110323672B, and the name is a Bragg grating external cavity laser module beam combining device, wherein the beam combining device includes a plurality of light-emitting modules arranged side by side, and a Bragg grating is used for wavelength locking; the output light is incident on the beam combining element after passing through the focusing optical element for beam combining, and the combined light is reflected by the light splitting element, a portion is transmitted, and a portion is incident on the dispersion element at the diffraction angle of the dispersion element, and parallel light is formed under the action of the transformation optical element; finally, a block of a light beam corresponding to the wavelength of the light-emitting module is formed on the image acquisition mechanism; whether the wavelength of the corresponding light-emitting module is locked is judged by whether there is a deviation between the block formed by the light-emitting module on the image acquisition mechanism and the preset block, which effectively solves the problem of low beam quality of the beam combining device caused by the inability of the existing beam combining device of multiple light-emitting modules to judge and detect the locked wavelength, and the beam combining device has a simple structure, fast judgment and detection, and convenient adjustment.

[0005] However, during the actual use of the above technical solution, the quality of the combined light beam is reduced due to the deviation between the laser wavelength actually locked by the Bragg grating of each light-emitting module and the preset locked laser wavelength. Later, a report proposed a method of using precision temperature-controlled VBG to achieve active wavelength locking of the module. However, the application of this method requires that each single-tube laser be equipped with precise temperature control equipment, which makes the use cost relatively high. At the same time, in actual applications, the response speed of precise wavelength adjustment is slow. More importantly, the reflection wavelength of VBG changes little with temperature, generally at 0.008nm / C, so to achieve a wavelength adjustment of 0.8nm, a temperature rise of 100 degrees is required, which limits the practicality of this method.

[0006] The Chinese patent also discloses an application number of 202211047426.3 and an authorization announcement number of CN115128820B, and its name is a spectral beam combining device and method with chirped reflective volume Bragg grating feedback. The spectral beam combining device includes a laser unit array, a half-wave plate, a polarization beam splitter, a chirped reflective volume Bragg grating, a transformation lens and a diffraction grating; the front cavity surface of the laser unit array is located on the front focal plane of the transformation lens, and the diffraction grating is located on the back focal plane of the transformation lens; the optical path of the spectral beam combining device includes a spectral beam combining direction and a non-spectral beam combining direction; while realizing the output of different wavelengths, the linear polarization degree of the laser unit resonance is improved to obtain a higher spectral beam combining efficiency, and also improve the reliability of the entire spectral beam combining light source; the distance between the volume Bragg grating as the back cavity surface and the back cavity surface of the laser unit is greatly shortened, which can reduce the structural stability of the resonant cavity.

[0007] However, this technical solution is for semiconductor laser arrays. In actual applications, the spatial position of each light-emitting point in the array changes due to the thermal efficiency of the laser, so the designed wavelength chirp gradient value cannot correspond to the position of each laser chip in the array after the change, resulting in the degradation of the beam combining effect. At the same time, this technology requires a large-sized transverse chirped volume Bragg grating, which is difficult to obtain and very expensive, which limits the practicality of this method. Utility Model Content

[0008] The technical problem to be solved by the utility model is the crosstalk problem of densely bundled multiple single-tube semiconductor lasers, and the wavelength locking of each single-tube semiconductor laser in a beam combining device can be actively and quickly achieved by using a transversely chirped body Bragg grating without heating.

[0009] In order to solve the above technical problems, the technical solution of the utility model is:

[0010] A transverse chirped Bragg grating multi-single-tube external cavity laser module beam combining device comprises at least three light-emitting modules and a diffraction grating arranged in an arc shape, wherein all the light-emitting modules project light to the diffraction grating, and a focusing optical element close to the light-emitting module and a transverse chirped Bragg grating close to the diffraction grating are arranged on the optical path between the light-emitting module and the diffraction grating, and the light projected by all the light-emitting modules passes through the focusing optical element and the transverse chirped Bragg grating, and then outputs a separate light beam by the diffraction grating.

[0011] In the above technical solution, the focusing optical element is used to collimate the laser beam emitted by the single-tube semiconductor laser, which can compress the divergence angle of the laser beam in the fast axis direction; the transverse chirped Bragg grating is used to control the emission wavelength of the single-tube laser; the reflector is used to reflect the collimated laser beam; the light emitted by each single tube passes through the transverse chirped Bragg grating after being closely arranged by the reflector, and the transverse chirped Bragg grating can simultaneously compress the divergence angle of each single-tube laser beam in the slow axis direction. The reflectors corresponding to all the multiple single-tube semiconductor lasers are located on the same side of the Fourier transform lens, and a diffraction grating is provided on the other side of the Fourier transform lens.

[0012] Preferably, the light emitting module comprises a plurality of single-tube semiconductor lasers arranged in a transverse linear manner side by side, which is convenient for practical application.

[0013] Preferably, the single-tube semiconductor laser outputs visible light.

[0014] Preferably, one of the light-emitting modules is a reference multi-single-tube close-packed light-emitting module, and the remaining light-emitting modules are multi-single-tube close-packed light-emitting modules.

[0015] Preferably, the focusing optical element is a Fourier transform lens, which is used to receive the collimated laser beam reflected by the reflector and perform Fourier transform.

[0016] Preferably, the transverse chirped Bragg grating is a transverse chirped Bragg grating. The length and width of the transverse chirped Bragg grating are 4 mm and 1.5 mm respectively. In the long direction, the reflection wavelength of the transverse chirped Bragg grating gradually increases or decreases with the length, and generally spans an interval of 0.3nm-1nm. In this way, the output reflection wavelength required by the single-tube laser can be adjusted arbitrarily according to the deviation of the actual position to achieve the purpose of quickly and conveniently adjusting the output laser wavelength of the single-tube laser without the need for complex and expensive temperature control equipment to heat the VBG with a single reflection wavelength.

[0017] Preferably, the central reflection wavelength range of the transverse chirped Bragg grating is 400-700 nm, and the central reflectivity is 5%-30%.

[0018] Preferably, the central reflection wavelength range of the transverse chirped Bragg grating is 1500-3000 nm, and the central reflectivity is 5%-30%.

[0019] Preferably, the diffraction grating is a transmission grating.

[0020] Preferably, the diffraction grating is a reflective grating.

[0021] Preferably, the diffraction angles of the diffraction gratings are all the grating blaze angles of the diffraction gratings. The diffraction gratings are placed at a specific angle so that the incident angle of the Fourier-transformed laser beam on the diffraction grating is equal to its diffraction angle, and all laser beams are diffracted and output at the same exit angle and the diffracted output laser beams become a single beam.

[0022] The utility model has the following characteristics and beneficial effects:

[0023] The utility model provides a transverse chirped Bragg grating multi-single-tube external cavity laser module beam combining device, each light-emitting module includes multiple single-tube semiconductor lasers, and the output lasers of the multiple single-tubes are densely arranged in space to achieve spatial beam combining. By using single-tube semiconductor lasers as beam combining light sources, the beam quality of the laser beam after beam combining can be greatly improved. The chirped Bragg gratings emitted by the multiple single-tube lasers of each module are theoretically locked at different wavelengths without crosstalk. The laser wavelengths of each beam combining module are regulated and locked by the chirped body Bragg grating according to the actual needs of setting the locked wavelength, and there is no need to control the temperature of the chirped body Bragg grating; the beam combining modules are arranged in a fan shape, so that each beam combining mode shares the same diffraction grating, and the output beams overlap, which saves costs, improves the brightness and output power of the laser, and can greatly improve the output power of the final spectral beam combining. Compared with the existing methods, this method can couple higher laser power into optical fibers with thinner core diameters.

[0024] The utility model provides a transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device, which does not require a temperature control device and adjusts the working position of the transverse chirped Bragg grating so that the output light of the light emitting module reaches a preset locking wavelength.

[0025] The module is composed of multiple single tubes closely arranged, and a single lens is used for uniform collimation in the slow axis direction. This eliminates the need to use slow axis collimation for each single tube, reducing costs and difficulty in installation and adjustment.

[0026] The transmission lens acts as a converging lens to focus the light beams of each light-emitting unit onto the grating, thereby realizing the spatial superposition of multiple light-emitting units. Since the transmission lens acts as a focusing lens, it is not necessary to collimate the light beams of each light-emitting unit, the position of each single tube only needs to ensure equal optical path, and it is no longer necessary to strictly place it on the focal plane of the transmission lens. The distance between the two can be very close, and the overall optical path is shortened by nearly 1 / 2, thereby reducing the size of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 This is a transmission-type grating dense wavelength beam combining device of multiple single-tube closely-packed light-emitting modules in an embodiment of the utility model.

[0029] Figure 2 This is a reflective grating dense wavelength beam combining device of multiple single-tube closely packed light-emitting modules in an embodiment of the utility model.

[0030] Figure 3 This is a principle diagram of the light path of a light emitting module with multiple single tubes closely packed in an embodiment of the utility model.

[0031] Figure 4 This is the structural principle diagram of the transversely chirped Bragg grating.

[0032] In the figure, 1-light emitting module, 101-single tube semiconductor laser, 2-focusing optical element, 3-transverse chirped Bragg grating, 103-VBG element, 4-diffraction grating. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0034] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below with reference to the accompanying drawings.

[0035] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the following detailed description of the present invention. Those skilled in the art can fully understand the present invention without the description of these details.

[0036] Example 1

[0037] This embodiment provides a transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device, such as Figure 1 , Figure 3 and Figure 4As shown, it includes at least three light emitting modules 1 and diffraction gratings 4 arranged in an arc shape, and all the light emitting modules 1 project light to the diffraction gratings 4. In this embodiment, the diffraction gratings 4 are transmission gratings. The diffraction angles of the diffraction gratings 4 are all grating blaze angles of the diffraction gratings 4.

[0038] The output lasers of multiple single tubes are densely arranged in space to achieve spatial beam combining. By using single-tube semiconductor lasers as beam combining light sources, the beam quality of the laser beam after beam combining can be greatly improved. The chirped Bragg gratings emitted by multiple single-tube lasers in each module are theoretically locked at different wavelengths without crosstalk. The laser wavelengths of each beam combining module are regulated and locked by the chirped body Bragg grating according to the actual needs of setting the locked wavelength, and there is no need to control the temperature of the chirped body Bragg grating; the beam combining modules are arranged in a fan shape, so that each beam combining mode shares the same diffraction grating, and the output beams overlap, which saves costs, improves the brightness and output power of the laser, and can greatly increase the output power of the final spectral beam combining.

[0039] In this embodiment, three light emitting modules 1 are provided and arranged in an arc shape.

[0040] A focusing optical element 2 close to the light emitting module 1 and a transverse chirped Bragg grating 3 close to the diffraction grating 4 are arranged on the optical path between the light emitting module 1 and the diffraction grating 4, wherein the focusing optical element 2 is a focusing lens.

[0041] Furthermore, the light emitting module 1 includes a plurality of transversely densely arranged single-tube semiconductor lasers 101, which project visible light. The transversely chirped Bragg grating 3 includes a plurality of VBG elements 103, each of which corresponds to a VBG element 103 to achieve wavelength locking. Since different positions of the transversely chirped Bragg grating can reflect different wavelengths, the output wavelength of the single-tube laser can be adjusted by adjusting the position of the transversely chirped Bragg grating.

[0042] In a further configuration of this embodiment, the central reflection wavelength of the transversely chirped Bragg grating changes with the position in the length direction, satisfying the following relationship:

[0043] λ(x)=λ0+C(x)x

[0044] Where λ(x) is the reflection wavelength of the transverse chirped Bragg grating 10 when the transverse coordinate is x, λ0 is the central wavelength when the transverse coordinate is equal to 0; C(x) is the chirp coefficient of the wavelength changing with the X coordinate, and the unit is nm / mm. It can be seen from the formula that the reflection wavelength of the transverse chirped Bragg grating changes linearly with the transverse position, and the desired reflection wavelength can be selected according to needs in actual use.

[0045] Specifically, in this embodiment, the central reflection wavelength range of the transverse chirped Bragg grating is 400-700 nm, and the central reflectivity is 5%-30%.

[0046] Example 2

[0047] The difference between this embodiment and embodiment 1 is that Figure 2 As shown, the diffraction grating 4 is a reflective grating.

[0048] The other features of this embodiment are the same as those of Embodiment 1, except that the transmission grating is replaced by a reflection grating. Since the diffraction principles of the two gratings are the same, no specific description is given in this embodiment.

[0049] Example 3

[0050] The difference between this embodiment and embodiment 1 is that the central reflection wavelength range of the transverse chirped Bragg grating is 1500-3000 nm, and the central reflectivity is 5%-30%.

[0051] The other features of this embodiment are the same as those of Embodiment 1 and are not described in detail in this embodiment.

[0052] The above is a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principles and spirit of the present invention, various changes, modifications, substitutions and variations of these embodiments including components still fall within the scope of protection of the present invention.

Claims

1. A transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device, characterized in that: The invention comprises at least three light-emitting modules (1) and a diffraction grating (4) arranged in an arc shape, wherein all the light-emitting modules (1) project light onto the diffraction grating (4), and a focusing optical element (2) close to the light-emitting module (1) and a transverse chirped Bragg grating (3) close to the diffraction grating (4) are arranged on the optical path between the light-emitting module (1) and the diffraction grating (4). The light-emitting module (1) comprises a plurality of single-tube semiconductor lasers (101) arranged linearly side by side in a transverse direction, and the transverse chirped Bragg grating (3) comprises a plurality of VBG elements (103), and each of the single-tube semiconductor lasers (101) corresponds to a VBG element (103).

2. The transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to claim 1, characterized in that: The single-tube semiconductor laser (101) outputs visible light.

3. The transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to claim 1, characterized in that: One of the light-emitting modules (1) is a reference multi-single-tube close-packed light-emitting module, and the remaining light-emitting modules (1) are multi-single-tube close-packed light-emitting modules.

4. The transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to claim 1, characterized in that: The focusing optical element (2) is a Fourier transform lens.

5. The transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to claim 1, characterized in that: The central reflection wavelength range of the transverse chirped Bragg grating is 400-700nm, and the central reflectivity is 5%-30%.

6. The transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to claim 1, characterized in that: The central reflection wavelength range of the transverse chirped Bragg grating is 1500-3000nm, and the central reflectivity is 5%-30%.

7. The transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to claim 1, characterized in that: The central reflection wavelength of the transverse chirped Bragg grating changes with the position in the length direction, satisfying the following relationship: λ(x)=λ0+C(x)x Wherein λ(x) is the reflection wavelength of the transverse chirped Bragg grating 10 when the transverse coordinate is x, λ0 is the central wavelength when the transverse coordinate is equal to 0; C(x) is the chirp coefficient of the wavelength changing with the X coordinate, and the unit is nm / mm.

8. A transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to any one of claims 1 to 7, characterized in that: The diffraction grating (4) is a transmission grating.

9. A transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to any one of claims 1 to 7, characterized in that: The diffraction grating (4) is a reflective grating.

10. The transverse chirped Bragg grating multi-single tube external cavity laser module beam combining device according to claim 1, characterized in that: The diffraction angles of the diffraction grating (4) are all the grating blaze angles of the diffraction grating (4).

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