Collimated vortex dual-mode laser source system

Abstract

This invention discloses a collimated vortex dual-mode laser source system. The system includes a laser and a superlens. The superlens comprises a substrate and a nanopillar array on the substrate. The surface of the superlens away from the nanopillar array is integrated onto the laser emission surface of the laser. The nanopillar array comprises multiple nanopillars, and the phase at the center of each nanopillar satisfies: ; is the vortex phase and the collimated lens phase, and ; where is the topological charge carried by the vortex phase, θ is the azimuth angle of the center of each nanopillar in the polar coordinate system with the center of the superlens as the origin, f is the focal length of the superlens, r is the distance from the center of each nanopillar to the origin in the polar coordinate system with the center of the superlens as the origin, and λ is the wavelength of the incident light. This laser source system can emit a collimated vortex laser beam and propagate it in the far field, providing a compact solution for multidimensional optical field manipulation.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optical technology, specifically relating to a collimated vortex dual-mode laser source system. Background Technology

[0002] A vortex beam is a special type of beam with a helical phase wavefront. It carries orbital angular momentum (OAM) and, theoretically, can carry an infinite number of topological charges of different integer orders, which are orthogonal to each other, making it a hot research topic in wireless optical communication. Currently, OAM keying (OAM-SK) and OAM multiplexing (OAM-DM) have been applied in the field of optical communication. Simultaneously, the orbital angular momentum characteristics of vortex beams are also used to manipulate particles to rotate around the vortex beam.

[0003] Obtaining a collimated vortex beam capable of long-range propagation is a crucial prerequisite for the practical application of vortex beams. In existing technologies, the generation of collimated vortex beams is primarily achieved through methods such as spiral phase plates, fork gratings, or spatial light modulators. The most common method involves first collimating and expanding the laser output from the laser using a lens group, and then converting it into a collimated vortex beam using a spatial light modulator.

[0004] However, existing methods for generating collimated vortex beams have complex optical paths and require additional optical devices to control the light field and to be coupled with the light source, which hinders the lightweight practical application of collimated vortex beams.

[0005] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a collimated vortex dual-mode laser source system. Utility Model Content

[0006] The purpose of this invention is to provide a collimated vortex dual-mode laser source system that can emit a collimated vortex beam that can propagate in the far field.

[0007] To achieve the above objectives, the technical solution provided by an embodiment of this utility model is as follows:

[0008] A collimated vortex dual-mode laser source system includes a laser and a superlens. The superlens includes a substrate and a nanopillar array located on the substrate. The surface of the superlens away from the nanopillar array is integrated into the laser emission surface of the laser. The nanopillar array includes multiple nanopillars, and the phase of the center of each nanopillar is... satisfy: ;

[0009] It is the vortex phase, and

[0010] For the collimating lens phase, and ;

[0011] in, θ is the topological charge carried by the vortex phase, θ is the azimuth angle of the center of each nanopillar in the polar coordinate system with the center of the superlens as the origin, f is the focal length of the superlens, r is the distance from the center of each nanopillar to the origin in the polar coordinate system with the center of the superlens as the origin, and λ is the wavelength of the incident light.

[0012] In one embodiment, the divergence angle of the laser emitted by the laser is 5° to 25°.

[0013] In one embodiment, the laser includes a laser chip and a packaging structure, and the superlens is integrated on the laser chip or the packaging structure.

[0014] In one embodiment, the laser is a gallium nitride laser.

[0015] In one embodiment, the laser is an edge-emitting laser or a vertical-cavity surface-emitting laser.

[0016] In one embodiment, the nanopillar is a cuboid, the period of the nanopillar array is 100nm~600nm, the side length of the nanopillar is 50nm~480nm, and the height of the nanopillar is 300nm~1000nm.

[0017] In one embodiment, the focal length of the superlens is 100μm to 3000μm.

[0018] In one embodiment, the nanopillar array has a circular outline with a diameter of 200 μm to 2000 μm; or,

[0019] The outline of the nanopillar array is square, with a side length of 200μm to 2000μm.

[0020] In one embodiment, the superlens further includes a dielectric film layer located on a substrate, and the nanopillars located on the dielectric film layer, wherein the dielectric film layer and the nanopillars are made of the same material.

[0021] In one embodiment, the substrate is any one of gallium nitride substrate, silicon carbide substrate, sapphire substrate, lithium niobate substrate, and diamond substrate; and / or,

[0022] The nanopillars are any one of gallium nitride nanopillars, titanium oxide nanopillars, tantalum oxide nanopillars, and silicon nanopillars.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention designs and fabricates a superlens based on the principle of phase superposition, which can shape incident plane light into a collimated vortex beam. It integrates the superlens with a laser to create a miniaturized light source system capable of outputting a collimated vortex beam. This avoids the problem of reduced efficiency after coupling in traditional optical paths, while greatly simplifying the optical system and significantly reducing the complexity of traditional laser light source light field control systems. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the collimated vortex dual-mode laser source system in Embodiment 1 of this utility model;

[0027] Figure 2 This is a schematic diagram of the superlens structure in Embodiment 1 of this utility model;

[0028] Figure 3 This is a schematic diagram of the structure of the nanopillar in Embodiment 1 of this utility model;

[0029] Figure 4 This is a schematic diagram illustrating the design principle of the superlens in Embodiment 1 of this utility model;

[0030] Figure 5 The phase and transmittance curves of nanopillars with different side lengths obtained by simulation in Embodiment 1 of this utility model;

[0031] Figure 6 Figure 1 shows a simulation diagram of the light field distribution after a point light source is incident on a superlens in Embodiment 1 of this utility model. Figure 1a shows the light field distribution in the XZ plane after the superlens, Figure 2b shows the light field distribution in the XY plane at 640μm after the superlens, Figure 2c shows the light field distribution in the XY plane at 4000μm after the superlens, and Figure 3d shows the light field distribution in the XY plane at 8000μm after the superlens.

[0032] Figure 7 This is an optical microscope image of the superlens in Embodiment 1 of this utility model;

[0033] Figure 8 These are SEM images of the superlens at different magnifications in Embodiment 1 of this utility model;

[0034] Figure 9 This is a SEM image of the edge portion of the superlens in a 45° view of Embodiment 1 of this utility model;

[0035] Figure 10 This is a schematic diagram of the test optical path in Embodiment 1 of this utility model;

[0036] Figure 11 Figure 1 shows the light field distribution of the emitted beam from the collimated vortex dual-mode laser source system in Embodiment 1 of this utility model. Figure 1a shows the light field distribution in the XY plane at 5600μm behind the superlens, and Figure 1b shows the light field distribution in the YZ plane behind the superlens.

[0037] Explanation of key figure labels:

[0038] 10-Collimated vortex dual-mode laser source system, 11-Superlens, 111-Substrate, 112-Nanopillar, 12-Laser, 121-Metal tube base, 122-Laser chip, 123-Encapsulation cap, 20-20x objective lens, 30-Lens, 40-CCD. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0040] This invention discloses a collimated vortex dual-mode laser source system, including a laser and a superlens. The superlens includes a substrate and a nanopillar array located on the substrate. The side of the superlens away from the nanopillar array is integrated into the laser emission surface of the laser. The nanopillar array includes multiple nanopillars, and the phase of the center of each nanopillar is... satisfy: ;

[0041] It is the vortex phase, and

[0042] For the collimating lens phase, and ;

[0043] in, θ is the topological charge carried by the vortex phase, θ is the azimuth angle of the center of each nanopillar in the polar coordinate system with the center of the superlens as the origin, f is the focal length of the superlens, r is the distance from the center of each nanopillar to the origin in the polar coordinate system with the center of the superlens as the origin, and λ is the wavelength of the incident light.

[0044] The present utility model will be further described below with specific examples.

[0045] Embodiment 1:

[0046] Refer Figure 1 and in combination with Figure 2 as shown, the collimated vortex dual-mode laser source system 10 in this embodiment includes a laser 12 and a metalens 11. The metalens 11 includes a substrate 111 and a nanocolumn array located on the substrate. One side surface of the metalens 11 away from the nanocolumn array is integrated on the laser output surface of the laser 12. The nanocolumn array includes a plurality of nanocolumns 112, and the phase of the center of each nanocolumn 112 satisfies: ;

[0047] is the vortex phase, and

[0048] is the collimating lens phase, and ;

[0049] wherein, is the topological charge number carried by the vortex phase, θ is the azimuth angle of the center of each nanocolumn in the polar coordinate system with the center of the metalens as the origin, f is the focal length of the metalens, r is the distance from the center of each nanocolumn to the origin in the polar coordinate system with the center of the metalens as the origin, and λ is the wavelength of the incident light.

[0050] Among them, the substrate 111 is any one of a gallium nitride substrate, a silicon carbide substrate, a sapphire substrate, a lithium niobate substrate, and a diamond substrate, and the nanocolumn 112 is any one of a gallium nitride nanocolumn, a titanium oxide nanocolumn, a tantalum oxide nanocolumn, and a silicon nanocolumn.

[0051] Preferably, the substrate is selected as a gallium nitride substrate, and the nanocolumn is a gallium nitride nanocolumn. Using a gallium nitride homogeneous metalens can give full play to the excellent properties of the gallium nitride material, such as low absorption rate and high refractive index.

[0052] Furthermore, in other multiple embodiments, the metalens may further include a dielectric film layer. The dielectric film layer is located on the substrate, and the nanocolumns are located on the dielectric film layer. The material of the dielectric film layer is the same as that of the nanocolumns.

[0053] Refer Figure 3 as shown, preferably, the nanocolumns in this embodiment are cuboids. In the visible light range, the period of the nanocolumn array (i.e., the center distance between adjacent two nanocolumns) P is 100 nm to 600 nm, the side length L of each nanocolumn in the array is from 50 nm to 480 nm, and the height H is from 300 nm to 1000 nm.

[0054] Refer Figure 4As shown, in this embodiment, a superlens with a phase distribution that satisfies the phase distribution of the collimated vortex beam is designed based on the principle of phase superposition and the linear superposition of the vortex phase and the collimating lens phase.

[0055] Specifically, the design method includes the following steps:

[0056] S1. Based on the wavelength of the laser beam and the target focal length, preset the size and phase distribution of the superlens, as well as the periodic range and height range of the nanopillar.

[0057] Specifically, considering that the laser beam emitted by the laser has a large divergence angle of 5°~25°, the divergence angle of the laser beam is 5°~10° along the normal direction of the laser beam's output end face and 10°~25° along the direction parallel to the laser beam's output end face. In order to enable the superlens to be directly integrated on the laser beam's output end face to directly control the laser beam's optical field and shape the plane light emitted by the laser beam into a collimated vortex beam, the target focal length of the superlens is 100μm~3000μm. That is, the distance between the nanopillars arrayed on the superlens and the laser beam's output end face is 100μm~3000μm.

[0058] In addition, to ensure the control effect of the laser beam emitted by the laser, the superlens needs to cover the laser's output end face, that is, the size of the superlens should not be too small.

[0059] Specifically, in this embodiment, the outline shape of the nanopillar array is circular with a diameter of 200μm to 2000μm. In other embodiments, the outline shape of the nanopillar array can also be square with a side length of 200μm to 2000μm.

[0060] It should be understood that the period range of the nanopillar array and the height range of the nanopillars must meet the matching relationship with the wavelength, and the period must be smaller than the wavelength of the incident light.

[0061] Specifically, in this embodiment, the wavelength of the incident light is 520nm, the period of the nanopillar array is 100nm~500nm, the height of the nanopillar is 400nm~900nm, and the phase and transmission optical response of the above period and height ranges at a wavelength of 520nm are simulated.

[0062] More specifically, in this embodiment, the target focal length is 640 μm, the outline shape of the nanopillar array is circular with a diameter of 210 μm, and the topological charge number is... Given a value of 1, the phase distribution required for the superlens is determined based on the phase formula for the nanopillars described above.

[0063] It should be noted that the topological charge numbers can be arbitrarily superimposed as needed, and theoretically, an infinite number of them can be set in the communication field, including but not limited to ±1, ±2, ±3. The more the number, the greater the transmission information that can be carried, and different topological charges do not interfere with each other. Substituting the topological charge numbers into the formula, by regulating the multi-dimensional parameters of the length, width, and height of the nanocolumns in the nanocolumn array, the generation of vortex light with different topological charges can be achieved.

[0064] S2. Select a period within the period range of the nanocolumn array and a height within the height range of the nanocolumns, simulate the phase distribution and transmittance distribution of nanocolumns with different sizes, and establish a database.

[0065] As Figure 5 shown in the figure, according to the simulation results, select the period of the nanocolumn array as 300 nm, the height of the nanocolumns as 800 nm within the range of step 1 above, and the contour shape of the nanocolumns is square. The side length of the nanocolumns needs to be less than the period. Use the finite-difference time-domain method to calculate the phase and transmission optical response of the nanocolumns with different side lengths within the range of 80 nm to 240 nm of the side length to establish a database for the design of the superlens.

[0066] Specifically, in the simulation, an x-polarized or y-polarized light source with a wavelength of 520 nm is set in the substrate, the layer in the z direction is assumed to be perfectly matched, and periodic boundary conditions are set along the x direction and the y direction.

[0067] S3. Select the optimal size parameters of the nanocolumns at the corresponding phase according to the data in the database, and construct a nanocolumn array.

[0068] Specifically, screen the side lengths of the nanocolumns according to the data in the database, construct a nanocolumn array with a circular overall contour shape of gradient distribution. While realizing the generation of vortex light, use the nanocolumn array with gradient distribution to perform gradient modulation on the phase of the incident light and maintain the far-field divergence angle.

[0069] As Figure 6 shown in the figure, perform a light field distribution simulation on the designed superlens. The point light source is incident 640 μm in front of the superlens. The simulation results show that the designed superlens can shape the incident light, and the incident light can generate a collimated vortex beam after passing through the superlens and propagate over a long distance, presenting as a vortex beam in the far field.

[0070] The present utility model designs the superlens by using the propagation phase, adjusts the phase of the nanocolumns by controlling the size of the nanocolumns, and the designed superlens is easier to process and is suitable for standard micro-nano processing technologies.

[0071] The preparation method of the superlens in this embodiment includes the following steps:

[0072] S1. Select a gallium nitride single crystal wafer as the raw material, spin-coat an electron beam photoresist on the gallium nitride single crystal wafer. The electron beam photoresist is preferably PMMA (polymethyl methacrylate) A4 photoresist with a thickness of 250 nm;

[0073] S2. Use the electron beam lithography process to expose the electron beam photoresist to prepare a patterned electron beam photoresist with the above-designed superlens pattern;

[0074] S3. Adopt the electron beam evaporation process to deposit a Ni metal thin film on the gallium nitride single crystal wafer and the patterned electron beam photoresist, and use the stripping process to remove the electron beam photoresist and the Ni metal thin film thereon to achieve pattern transfer;

[0075] S4. Use the Ni metal thin film as a mask, adopt the inductively coupled plasma etching process to etch the gallium nitride single crystal wafer, and remove the remaining Ni metal thin film after etching to form an array of nanocolumns on the gallium nitride single crystal wafer, obtaining a gallium nitride homogeneous superlens.

[0076] It should be noted that in many other embodiments, a substrate with a gallium nitride thin film, a titanium oxide thin film or a tantalum oxide thin film formed on its surface can also be selected as the raw material, and all or part of the thin film is etched during the etching process, that is, the superlens includes a substrate and nanocolumns stacked in sequence or a substrate, a dielectric film layer and nanocolumns stacked in sequence.

[0077] See Figure 7 、 Figure 8 As shown, the quality of the superlens prepared in this embodiment is good, Figure 9 The SEM image of the edge part of the superlens under a 45° view is shown, showing that the prepared nanocolumns have good perpendicularity.

[0078] Furthermore, gallium nitride-based lasers have achieved important applications in the fields of laser display, laser projection, visible light communication, etc. due to their advantages such as high luminous efficiency, narrow linewidth, and high color rendering index. Therefore, the laser in this embodiment is preferably a gallium nitride laser.

[0079] Specifically, the laser can be a gallium nitride green laser or a gallium nitride blue laser, and the wavelength of the emitted laser is 400 nm - 540 nm. The laser in this embodiment is a gallium nitride green laser.

[0080] Furthermore, the laser is an edge-emitting laser or a vertical cavity surface-emitting laser, and the superlens is integrated with the laser by bonding.

[0081] In addition, the laser includes a laser chip and a packaging structure, and the superlens can be integrated on the laser chip or the packaging structure.

[0082] Specifically, in combination with Figure 1As shown in the figure, the laser in this embodiment is a vertical cavity surface emitting laser, which includes a metal header 121 and a laser chip 122 located on the metal header 121. The encapsulation structure includes an encapsulation cap 123, which is formed on the metal header 121 and encapsulates the laser chip 122. The laser emits from the surface of the encapsulation cap, and the laser chip 122 is a vertical cavity surface emitting laser chip.

[0083] More specifically, the metalens 11 is integrated on the encapsulation cap 123. When integrating, the thickness of the encapsulation cap, the thickness of the substrate, and the gap are considered. Therefore, the focal length of the metalens is set to be 1000 μm to 3000 μm.

[0084] It should be noted that in many other embodiments, for a vertical cavity surface emitting laser, the laser emitting surface can also be directly selected as the top surface of the laser chip, that is, the metalens can also be directly integrated on the laser chip. When integrating, only the thickness of the metalens substrate and the gap need to be considered. The focal length of the metalens can be set to be 100 μm to 300 μm, and then the whole is encapsulated after integration.

[0085] In addition, for an edge-emitting laser, the encapsulation structure of the laser includes a heat sink and an encapsulation cap. The metalens can be integrated on the top surface of the heat sink or on the top surface of the encapsulation cap, and the focal length of the metalens is set within the range of 100 μm to 3000 μm according to the actual structure of the integrated device.

[0086] Aiming at the problems of volume redundancy and poor mode stability existing in the traditional discrete vortex light generation light source system, in this embodiment, the metalens is innovatively monolithically integrated with the laser. Based on the metasurface for phase modulation, the synchronous dynamic modulation of different topological charge numbers of the vortex light and the quasi-orthogonal beam is realized through the phase superposition architecture of the nano-column array. At the same time, based on the actual requirements of the focal length in the integration of the metalens and the laser, the focal length parameter in the nano-column phase formula is designed, and the metalens is successfully directly integrated on the light-emitting end surface of the laser to perform optical field modulation on the laser beam emitted by the laser, obtaining a miniaturized integrated vortex-collimated dual-mode laser source system that can directly output a collimated vortex beam, and performing far-field propagation, removing the collimation optical path system and the spatial modulator in the traditional beam generation system, simplifying the optical system and having no problem of reduced efficiency after coupling in the traditional optical path, and having application prospects in the fields of optical communication, particle capture, and biomedicine.

[0087] Refer Figure 10 As shown in the figure, in this embodiment, the optical field characteristic verification test is carried out on the laser source system after the integration of the metalens and the gallium nitride green laser. In the test, the collimated vortex dual-mode laser source system 10 is placed at the forefront of the test optical path, and the 20× objective lens 20, the lens 30, and the CCD camera 40 are successively fixed on the displacement stage. The centers of the collimated vortex dual-mode laser source system 10, the 20× objective lens

[0088] Specifically, after imaging the surface of the metalens during the test, the displacement stage was gradually moved along the Z-axis away from the spatial light adjustment system. The displacement interval was 28 μm each time, and the X-Y plane light intensity distribution at each position was gradually photographed until reaching 5600 μm behind the metalens.

[0089] As Figure 11 shown, the integrated collimated vortex dual-mode laser source system can stably output collimated vortex beams and perform far-field propagation.

[0090] From the above technical solutions, it can be seen that the present utility model has the following beneficial effects:

[0091] The present utility model designs and prepares a metalens capable of shaping incident plane light into a collimated vortex beam based on the principle of phase superposition, and integrates it with a laser to prepare a miniaturized light source system capable of outputting collimated vortex beams, avoiding the problem of reduced efficiency after coupling in the traditional optical path. At the same time, the optical system is greatly simplified, and the complexity of the traditional laser light source light field regulation system is greatly reduced.

[0092] For those skilled in the art, it is obvious that the present disclosure is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present disclosure. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present disclosure is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present disclosure. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0093] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A collimated vortex dual-mode laser source system, characterized in that, The collimated vortex dual-mode laser source system includes a laser and a superlens. The superlens includes a substrate and a nanopillar array located on the substrate. The surface of the superlens away from the nanopillar array is integrated into the laser emission surface of the laser. The nanopillar array includes multiple nanopillars, and the phase of the center of each nanopillar is... satisfy: ; for the vortex phase, and for the collimator lens phase, and ; in, θ is the topological charge carried by the vortex phase, θ is the azimuth angle of the center of each nanopillar in the polar coordinate system with the center of the superlens as the origin, f is the focal length of the superlens, r is the distance from the center of each nanopillar to the origin in the polar coordinate system with the center of the superlens as the origin, and λ is the wavelength of the incident light.

2. The collimated vortex dual-mode laser source system of claim 1, wherein, The laser emitted by the laser has a divergence angle of 5° to 25°.

3. The collimated vortex dual-mode laser source system of claim 1, wherein, The laser includes a laser chip and a packaging structure, and the superlens is integrated on the laser chip or the packaging structure.

4. The collimated vortex dual-mode laser source system of claim 1, wherein, The laser is a gallium nitride laser.

5. The collimated vortex dual-mode laser source system of claim 1, wherein, The laser is either an edge-emitting laser or a vertical-cavity surface-emitting laser.

6. The collimated vortex dual-mode laser source system of claim 1, wherein, The nanopillars are cuboids, the period of the nanopillar array is 100nm~600nm, the side length of the nanopillars is 50nm~480nm, and the height of the nanopillars is 300nm~1000nm.

7. The collimated vortex dual-mode laser source system according to claim 1, characterized in that, The focal length of the superlens is 100μm~3000μm.

8. The collimated vortex dual-mode laser source system of claim 1, wherein, The nanopillar array has a circular outline with a diameter of 200 μm to 2000 μm; or, The outline of the nanopillar array is square, with a side length of 200μm to 2000μm.

9. The collimated vortex dual-mode laser source system of claim 1, wherein, The superlens further includes a dielectric film layer located on a substrate, and the nanopillars located on the dielectric film layer. The dielectric film layer and the nanopillars are made of the same material.

10. The collimated vortex dual-mode laser source system of claim 1, wherein, The substrate is any one of gallium nitride substrate, silicon carbide substrate, sapphire substrate, lithium niobate substrate, and diamond substrate; and / or, The nanopillars are any one of gallium nitride nanopillars, titanium oxide nanopillars, tantalum oxide nanopillars, and silicon nanopillars.

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