High-efficiency wavelength polarization multiplexing multi-path laser beam combining device and method

Abstract

The invention discloses a high-efficiency wavelength polarization multiplexing multi-path laser beam combining device and method, and belongs to the field of laser beam combining.The device comprises a laser light source array, an angle control assembly, a polarization conversion assembly and a wavelength polarization multiplexing multi-path laser beam combiner which are sequentially arranged, the laser light source array comprises two symmetrically arranged array laser groups, the angle control assembly comprises two symmetrically arranged lens groups, the polarization conversion assembly comprises two symmetrically arranged wave plate groups, and the wavelength polarization multiplexing multi-path laser beam combiner adopts an abnormal reflection metasurface with a periodic structure. The abnormal reflection metasurface comprises a plurality of supercell structures arranged periodically, and each supercell structure comprises a plurality of unit cells arranged at equal intervals. By adopting the high-efficiency wavelength polarization multiplexing multi-path laser beam combining device and method, the problem that in the prior art, beam combining of multiple paths of orthogonal incident light with different wavelengths and polarization states can be achieved only by using multiple devices in a combined mode can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser beam combining, and in particular to a high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device and method. Background Art

[0002] Quantum cascade lasers have received widespread attention since their introduction. Compared with traditional medium and long-wave infrared lasers, quantum cascade lasers have the advantages of small size, narrow linewidth and broadband tunability, which makes them widely used in trace gas detection, medical diagnosis, environmental monitoring and industrial control. However, at present, a single quantum cascade laser still has only a watt-level output power in room temperature continuous wave mode. It is difficult to further increase the output power by optimizing the active layer design and device structure, and it will cause oscillation of high-order transverse modes, resulting in deterioration of laser beam quality. In order to obtain high output power and good beam quality, laser beam combining technology has been proven to be an effective method.

[0003] Spectral beam combining and polarization beam combining are the two most commonly used methods of incoherent laser beam combining. Traditional spectral beam combining devices include volume Bragg gratings, blazed gratings and dichroic mirrors, while polarization beam combining devices include Brewster plates and birefringent crystals. Among them, volume Bragg gratings need to be cascaded to achieve spectral beam combining of multiple incident lights, and there are many discrete devices and they are difficult to integrate. Dichroic mirrors are similar to volume gratings. One device can only achieve two-way laser beam combining. For multi-way lasers, multiple devices must be used, and when the spectra of the laser sources are relatively close, the film design and preparation requirements of the beam combiner are very high. Metal blazed gratings can achieve spectral beam combining of multiple lasers and have high diffraction efficiency. They are currently the most ideal multi-way laser spectral beam combining devices. However, blazed gratings do not have the function of polarization beam combining and need to be used in conjunction with polarization beam combining devices to achieve the combination of more lasers. Traditional polarization beam combiners such as Brewster plates and birefringent crystals can only be used for polarization beam combining of two orthogonal polarized lights. In the mid- and long-wave infrared bands, the larger Brewster angle of the Brewster plate and the smaller separation angle of the birefringent crystal make it difficult to adjust the beam combining optical path. Summary of the invention

[0004] The purpose of the present invention is to provide a high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device and method. Through the design of the metasurface microstructure and the optical path design, one device can be used to achieve high-efficiency laser beam combining of multiple orthogonal polarization light beams with different wavelengths, thereby solving the problem in the above-mentioned background technology that multiple devices need to be used in combination to achieve multi-channel incident light beam combining with different wavelengths and orthogonal polarization states.

[0005] To achieve the above-mentioned object, the present invention provides a high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device, comprising a laser light source array, an angle control component, a polarization conversion component, and a wavelength polarization multiplexing multi-channel laser beam combiner arranged in sequence, the laser light source array comprises two groups of symmetrically arranged array laser groups, the angle control component comprises two groups of symmetrically arranged lens groups, the polarization conversion component comprises two groups of symmetrically arranged wave plate groups, and the array laser groups, the lens groups, and the wave plate groups are symmetrically distributed on both sides of the wavelength polarization multiplexing multi-channel laser beam combiner;

[0006] The wavelength polarization multiplexing multi-channel laser beam combiner adopts an abnormal reflection metasurface with a periodic structure. The abnormal reflection metasurface includes a plurality of periodically arranged supercell structures, and each supercell structure includes a plurality of unit cells arranged at equal intervals.

[0007] Preferably, each array laser group includes a plurality of lasers with different output wavelengths, and the output lights of the lasers with the same number in the two groups have the same central wavelength and are linearly polarized with the same polarization direction.

[0008] Preferably, each lens group includes a plurality of collimating lenses arranged in an array, the number of collimating lenses in each lens group is the same as the number of lasers in each array laser group, and the array laser group is located at the back focal plane of the corresponding lens group.

[0009] Preferably, each wave plate group includes a plurality of quarter wave plates, the number of quarter wave plates in each wave plate group is the same as the number of lasers in each array laser group, the incident surface of the quarter wave plate is perpendicular to the optical axis of the light beam output from the collimating lens, and the quarter wave plate is used to convert the polarization state of each pair of lasers with the same central wavelength into orthogonal circularly polarized light.

[0010] Preferably, the wavelength polarization multiplexing multiplexer is located in a high spatial overlap region of parallel light emitted from each polarization conversion component.

[0011] Preferably, the light beams emitted by the lasers of each array laser group are incident on the wavelength polarization multiplexing multi-channel laser beam combiner at symmetrical angles.

[0012] Preferably, the parallel light beams reaching each side of the wavelength polarization multiplexing multi-channel laser combiner have different central wavelengths, different angles between the transmission direction and the normal of the wavelength polarization multiplexing multi-channel laser combiner, and the same polarization state, which is left-handed or right-handed circularly polarized light.

[0013] Preferably, each unit cell has a different rotation angle, and each unit cell includes a bottom layer, a middle layer and an upper layer, the bottom layer is made of copper, the middle layer is made of silicon dioxide, and the upper layer is an amorphous silicon column.

[0014] The present invention provides a beam combining method for a high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device, comprising the following steps:

[0015] Step 1: The lens group converts the output beam of the laser into multiple parallel beams with different transmission directions;

[0016] Step 2: After passing through the polarization conversion component, the multiple parallel light beams are converted into left-handed circularly polarized light or right-handed circularly polarized light, and the left-handed circularly polarized light and the right-handed circularly polarized light are symmetrical on both sides of the wavelength polarization multiplexing multi-channel laser beam combiner;

[0017] Step three, left-handed circularly polarized light and right-handed circularly polarized light are respectively incident on the wavelength polarization multiplexing multi-channel laser beam combiner from two symmetrical sides. The wavelength polarization multiplexing multi-channel laser beam combiner is used to reflect the light beams with orthogonal polarization states, different wavelengths and different incident angles incident from both sides to the same direction, thereby realizing wavelength polarization multiplexing of multiple incident lasers.

[0018] Therefore, the present invention adopts the above-mentioned high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device and method, which has the following effects:

[0019] (1) The key device of the present invention is a wavelength polarization multiplexing multi-channel laser beam combiner, which can achieve abnormal reflection of the incident light beam in a wide band, greatly improving the beam combining efficiency;

[0020] (2) The wavelength polarization multiplexing multi-channel laser beam combiner of the present invention can not only perform abnormal reflection on wavelengths in a wide band, but also realize abnormal reflection beam combining of incident light of the same wavelength and orthogonal polarization states, and can realize incoherent beam combining of multiple incident lasers of different wavelengths and orthogonal polarization states.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of a high-efficiency wavelength polarization multiplexing multi-channel laser beam combining structure of the present invention;

[0023] Figure 2 is a schematic structural diagram of a beam combining device according to an embodiment of the present invention;

[0024] Figure 3 A schematic diagram of a unit cell structure of a wavelength polarization multiplexing multi-channel laser beam combiner according to an embodiment of the present invention;

[0025] Figure 4 A top view of a unit cell structure of a wavelength polarization multiplexing multi-channel laser beam combiner according to an embodiment of the present invention;

[0026] Figure 5 This is a graph of the polarization conversion efficiency of a single cell of a wavelength polarization multiplexing multi-channel laser beam combiner according to an embodiment of the present invention;

[0027] Figure 6A schematic diagram of a supercell structure of a wavelength polarization multiplexing multi-channel laser beam combiner according to an embodiment of the present invention;

[0028] Figure 7 It is a relationship diagram between the normalized far-field reflection intensity and the reflection angle of the wavelength polarization multiplexing multi-channel laser beam combiner under right-hand circular polarization (RCP) and left-hand circular polarization (LCP) at wavelengths of 4.0 μm, 4.6 μm, and 4.8 μm in an embodiment of the present invention;

[0029] Figure 8 This is a relationship diagram between the near-field phase distribution and propagation distance of the reflected field of the wavelength polarization multiplexing left-handed circular polarization combiner in the RCP and LCP polarization states at wavelengths of 4.0μm, 4.6μm, and 4.8μm according to an embodiment of the present invention.

[0030] Reference numerals

[0031] 1. Laser light source array; 2. Angle control component; 3. Polarization conversion component; 4. Wavelength polarization multiplexing multi-channel laser beam combiner. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0033] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products or devices.

[0034] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0035] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0036] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] Example

[0038] like Figure 1 As shown, a high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device described in the present invention includes a laser light source array 1, an angle control component 2, a polarization conversion component 3, and a wavelength polarization multiplexing multi-channel laser beam combiner 4 arranged in sequence.

[0039] Figure 2 An example of the high-efficiency wavelength polarization multiplexing multi-channel laser beam combining technology involved in the present invention is shown in detail. The laser light source array 1 includes two groups of array laser groups arranged symmetrically on the left and right, and each group of array laser groups includes three independent lasers with different output wavelengths, and the lasers are mid-infrared lasers. The two groups of array laser groups are respectively located on the +X-axis direction side and the -X-axis direction side of the combined light. The output light center wavelength of the lasers with the same number in the two groups is the same and is linearly polarized with the same polarization direction. The output light power of the six mid-infrared lasers is 500mW, the output spatial mode is the fundamental transverse mode, the spectral linewidth is 20-30nm, the polarization state is linearly polarized light, and the vertical distance from the reflection surface of the wavelength polarization multiplexing multi-channel laser beam combiner 4 is 1000mm. Among them, when the light beams of the three mid-infrared lasers on each side of the +X axis and -X axis are arranged from near to far from the beam combining optical axis, their central wavelengths are 4.0μm, 4.6μm and 4.8μm respectively, and the distances from the optical axis of the output beam after beam combining are 228mm, 264mm and 277mm respectively. The spectral line width of each mid-infrared laser is smaller than the central wavelength interval to ensure that the laser spectra of each channel do not overlap. The outgoing beams of the six mid-infrared lasers are perpendicular to the incident end face of the angle control component 2.

[0040] The angle control component 2 includes two symmetrically arranged lens groups, each lens group includes three collimating lenses (aspheric plano-convex lenses). The number of collimating lenses in each lens group is the same as the number of lasers in each array laser group. The array laser group is located at the back focal plane of the corresponding lens group. The aspheric plano-convex lens is made of germanium (Ge), has an aperture of 10mm, and a back focal length of 6.2mm. The six aspheric plano-convex lenses are all 6.2mm away from the six mid-infrared laser exit end faces, and the optical axis of the mid-infrared laser exit laser and the optical axis of the aspheric plano-convex lens have an offset along the +X axis or -X axis direction. The three laser output beams with wavelengths of 4.0μm, 4.6μm and 4.8μm on the +X axis side are offset from the optical axis of the aspheric plano-convex lens along the -X axis, and the offsets of the laser output beams with wavelengths of 4.0μm, 4.6μm and 4.8μm and the optical axis of the aspheric plano-convex lens are 1.41mm, 1.64mm and 1.72mm, respectively. The three laser output beams with wavelengths of 4.0μm, 4.6μm and 4.8μm on the -X direction side are offset from the optical axis of the aspheric plano-convex lens along the +X direction, and the offsets are 1.41mm, 1.64mm and 1.72mm, respectively. Therefore, after passing through the angle control component 2, the six laser beams are converted into six parallel light beams with different propagation directions. The propagation directions are symmetrical about the Z axis, and the angles with the +Z direction are 15.47°, 14.80°, 12.84°, -12.84°, -14.80° and -15.47° respectively.

[0041] The polarization conversion component 3 includes two groups of symmetrically arranged wave plates, each group of wave plates includes three quarter wave plates, and the number of quarter wave plates in each group of wave plates is the same as the number of lasers in each array laser group. The incident surface of the quarter wave plate is perpendicular to the optical axis of the light beam emitted by the collimating lens, and the quarter wave plate is used to convert the polarization state of each pair of lasers with the same central wavelength into orthogonal circularly polarized light. The net aperture of the quarter wave plate is 10mm, the substrate material is magnesium fluoride (MgF2), the front and rear surfaces are coated with anti-reflection film, the reflectivity at the design wavelength is less than 0.25%, and its incident end face is perpendicular to the six different directions of the light beam. The three light beams on the +X side are converted into right-handed circularly polarized light (RCP) after passing through the polarization conversion component 3, and the three light beams on the -X side are converted into left-handed circularly polarized light (LCP) after passing through the polarization conversion component 3.

[0042] The wavelength polarization multiplexing multi-channel laser beam combiner 4 is placed in the high spatial overlap area of ​​the six parallel lights emitted by the polarization conversion component 3. The wavelength polarization multiplexing multi-channel laser beam combiner 4 is a broadband anomalous reflection metasurface with a periodic structure. The incident angles of the six parallel lights relative to the broadband anomalous reflection metasurface are 15.47°, 14.80°, 12.84° and -12.84°, -14.80°, -15.47° respectively. The anomalous reflection metasurface can reflect parallel light beams with different transmission directions and polarization states orthogonal to the same direction. Due to the high anomalous reflectivity, high-efficiency wavelength polarization multiplexing combined beam laser output can be achieved.

[0043] The broadband anomalous reflection metasurface consists of several periodically arranged supercell structures, each of which contains ten equally spaced unit cells. Figure 3 As shown, each unit cell is composed of three layers of different materials. The bottom layer is copper (Cu), with a thickness of h3 = 0.3μm, and a length and width of P = 1.8μm; the middle layer is silicon dioxide (SiO2), with a thickness of h2 = 0.5μm, and a length and width of P = 1.8μm; the upper layer is an amorphous silicon column (Si), with a thickness of h1 = 2.3μm, a length of L = 1.4μm, and a width of W = 0.4μm. The refractive index in the 4-5μm band is 2.9. Each Si column rotates counterclockwise around the Z axis by a certain angle, as shown in Figure 1. Figure 4 As shown in the figure, the rotation angle is represented by θ. By changing the value of θ, the unit cell can obtain different phase responses. Figure 5 As shown, the polarization conversion efficiency of the unit cell is higher than 80% in the entire range of 3.7 to 5 μm, indicating that the metasurface can realize efficient reflection of incident light in a broadband range.

[0044] like Figure 6 As shown in the figure, a single supercell structure is composed of ten unit cells with different rotation angles. The 10 unit cell rotation angles θ are arranged along the X direction, which are 9°, 27°, 45°, 63°, 81°, 99°, 117°, 135°, 153° and 171° respectively. The total length of the supercell structure is D x =18μm, width P = 1.8μm. The entire metasurface is composed of 50×500 supercells, forming a beam combining device with a size of 900μm×900μm. According to the generalized Snell reflection law, when the six-way three-wavelength parallel light with orthogonal polarization states emitted by the polarization conversion component 3 is incident on the broadband anomalous reflection metasurface at angles of 15.47°, 14.80°, 12.84°, -12.84°, and -14.80°-15.47°, the reflection direction is all in the +Z direction, so the metasurface has a beam combining function.

[0045] like Figure 7As shown in the figure, the intensity distribution of the six beams after abnormal reflection is centered at 0°, and the corresponding abnormal reflection efficiencies (from left to right) are 95.3%, 93.2%, 90.9%, 95.3%, 93.2% and 90.9%, respectively, indicating that the beam combiner achieves high-efficiency beam combining of the six lasers. Figure 7 As shown in the figure, six plane wave incident beams with three different wavelengths and orthogonal polarization states still propagate in the form of plane waves after reflection, and the wavefront is continuous and relatively flat, indicating that the metasurface simultaneously realizes the abnormal reflection of six incident lasers. The normal direction of the maximum or minimum plane of the six reflected light wavefront interference is all in the 0° direction, indicating that the combined laser beam has the same propagation direction. Figure 7 and Figure 8 The results show that six incident light beams with three different wavelengths and orthogonal polarization states are successfully combined into a beam of parallel light with a transmission direction of 0° after reflection, and the combining efficiency is higher than 90%, that is, the high-efficiency wavelength polarization multiplexing combining of six mid-infrared lasers is achieved. The reflection combining efficiency of the six light beams is combined with the transmittance of the angle control component 2 of 90% and the transmittance of the polarization conversion component 3 of 99%, and the total combining efficiency of the wavelength polarization multiplexing multi-channel laser combining device in this embodiment is 83.0%, and the total output laser power is 2489.5mW.

[0046] The method of the high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device described in the present invention comprises the following steps:

[0047] The aspheric plano-convex lens converts the output light beams of six mid-infrared lasers into six parallel light beams with different transmission directions, and each of the six beams forms a group of three, with different wavelengths and the same polarization state; after passing through the polarization conversion component 3, the output lights of the three lasers in one of the laser light source arrays 1 are converted into three left-handed circularly polarized lights, and the output lights of the three lasers in the other laser light source array 1 are converted into three right-handed circularly polarized lights, which are incident on the wavelength polarization multiplexing multi-channel laser beam combining metasurface from the +X and -X directions respectively. The incident directions of a pair of incident lights with the same wavelength and orthogonal polarization states in each group of laser light source arrays 1 are symmetrical about the Z axis. With the help of the broadband anomalous reflection of the wavelength polarization multiplexing multi-channel laser beam combining metasurface, the six incident lights will all be anomalously reflected to form a combined laser with consistent reflection directions.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device, characterized in that: It includes a laser light source array, an angle control component, a polarization conversion component, and a wavelength polarization multiplexing multi-channel laser beam combiner arranged in sequence, wherein the laser light source array includes two groups of symmetrically arranged array laser groups, the angle control component includes two groups of symmetrically arranged lens groups, and the polarization conversion component includes two groups of symmetrically arranged wave plate groups, and the array laser group, the lens group, and the wave plate group are symmetrically distributed on both sides of the wavelength polarization multiplexing multi-channel laser beam combiner; The wavelength polarization multiplexing multi-channel laser beam combiner adopts an abnormal reflection metasurface with a periodic structure. The abnormal reflection metasurface includes a plurality of periodically arranged supercell structures, and each supercell structure includes a plurality of unit cells arranged at equal intervals.

2. The high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device according to claim 1, characterized in that: Each array laser group includes a number of lasers with different output wavelengths, and the output lights of the lasers with the same number in the two groups have the same central wavelength and are linearly polarized with the same polarization direction.

3. The high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device according to claim 2, characterized in that: Each lens group includes a plurality of collimating lenses arranged in an array. The number of collimating lenses in each lens group is the same as the number of lasers in each array laser group. The array laser group is located at the back focal plane of the corresponding lens group.

4. The high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device according to claim 3, characterized in that: Each wave plate group includes several quarter wave plates. The number of quarter wave plates in each wave plate group is the same as the number of lasers in each array laser group. The incident surface of the quarter wave plate is perpendicular to the optical axis of the light beam emitted by the collimating lens. The quarter wave plate is used to convert the polarization state of each pair of lasers with the same central wavelength into orthogonal circularly polarized light.

5. The high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device according to claim 1, characterized in that: The wavelength polarization multiplexing multiplexer is located in a high spatial overlap region of parallel light emitted from each polarization conversion component.

6. The high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device according to claim 2, characterized in that: The light beams emitted by the lasers of each array laser group are incident on the wavelength polarization multiplexing multi-channel laser combiner at symmetrical angles.

7. The high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device according to claim 1, characterized in that: The parallel light beams reaching each side of the wavelength polarization multiplexing multi-channel laser beam combiner have different central wavelengths, different angles between the transmission directions and the normal line of the wavelength polarization multiplexing multi-channel laser beam combiner, and the same polarization states, which are all left-handed or right-handed circularly polarized light.

8. The high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device according to claim 1, characterized in that: Each unit cell has a different rotation angle. Each unit cell includes a bottom layer, a middle layer and an upper layer. The bottom layer is made of copper, the middle layer is made of silicon dioxide, and the upper layer is an amorphous silicon column.

9. A beam combining method for a high-efficiency wavelength polarization multiplexing multi-channel laser beam combining device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: The lens group converts the output beam of the laser into multiple parallel beams with different transmission directions; Step 2: After passing through the polarization conversion component, the multiple parallel light beams are converted into left-handed circularly polarized light or right-handed circularly polarized light, and the left-handed circularly polarized light and the right-handed circularly polarized light are symmetrical on both sides of the wavelength polarization multiplexing multi-channel laser beam combiner; Step three, left-handed circularly polarized light and right-handed circularly polarized light are respectively incident on the wavelength polarization multiplexing multi-channel laser beam combiner from two symmetrical sides. The wavelength polarization multiplexing multi-channel laser beam combiner is used to reflect the light beams with orthogonal polarization states, different wavelengths and different incident angles incident from both sides to the same direction, thereby realizing wavelength polarization multiplexing of multiple incident lasers.

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