Vortex light laser based on novel pumping structure

Abstract

The invention provides a vortex light laser based on a novel pumping structure, and relates to the technical field of lasers. The laser comprises a pumping source, a novel annular lens, a focusing lens and a gain medium which are sequentially arranged in the light propagation direction, the side, close to the pumping source, of the novel annular lens is a lens convex face protruding towards the novel annular lens, and the side, close to the focusing lens, of the novel annular lens is an annular convex face with the double-arc-shaped longitudinal section. A laser resonant cavity is formed between the two end faces of the gain medium, divergent light beams output by the pumping source are converged and shaped into annular light beams through the novel annular lens, the annular light beams are focused by the focusing lens to form annular focusing light spots, and the annular focusing light spots are excited by the gain medium to achieve vortex light beam output. The laser is more compact in structure, has no defect of power loss, can realize high-efficiency shaping, and can obtain annular focusing light spots of dozens to hundreds of microns by matching with different focusing lenses, thereby obtaining high-efficiency oscillation laser output.

Description

Technical Field

[0001] The invention relates to the technical field of lasers, and in particular to a vortex light laser based on a novel pump structure. Background Art

[0002] A vortex beam is a structured beam with a spiral equiphase surface. During the transmission process, the light spirals forward and the photons carry orbital angular momentum. Due to the uncertainty of the central phase of the beam, the vortex beam has a central intensity zero point, and its light intensity distribution is annular. Laguerre-Gaussian (LG) mode beam is a typical vortex beam. Due to its unique light field structure, it has unique advantages in quantum communication, optical detection and other fields, and has always been a research hotspot in the field of optics.

[0003] There are two main ways to generate vortex lasers, including generation outside the resonant cavity and direct generation inside the resonant cavity. Among them, the generation outside the resonant cavity includes using phase modulation devices such as spiral phase plates and spatial light modulators to convert the fundamental mode Gaussian beam into a vortex beam. This type of method generally requires additional devices and has problems such as low efficiency and unstable transmission. Direct generation inside the resonant cavity uses direct oscillation selected from the laser transverse mode to generate a vortex beam. Its main method is to rely on the end face of the annular beam to pump the gain medium, thereby exciting the vortex beam.

[0004] There are two main ways to generate annular pump light: 1) Use an axicon lens to shape the Gaussian beam. First, the Gaussian beam is collimated by a plano-convex lens, and then the axicon lens (such as Figure 1 1) Use defective lenses (such as Figure 2 However, since the pump light before shaping is basically a Gaussian beam, its energy is mainly concentrated in the central area. Therefore, this method will waste most of the energy, resulting in a significant reduction in efficiency. Therefore, achieving high-efficiency and compact ring pump light shaping is a technical problem that needs to be solved in the research of vortex light lasers.

[0005] In view of the above reasons, the present invention proposes a vortex light laser based on a novel pump structure to solve the above technical problems. Summary of the invention

[0006] The object of the present invention is to provide a vortex light laser based on a novel pump structure, which has a compact structure and can achieve high-efficiency shaping to obtain high-efficiency oscillation laser output.

[0007] The present invention provides a vortex laser based on a novel pump structure, comprising: a pump source, a novel annular lens, a focusing lens, and a gain medium arranged in sequence along the light propagation direction. One side of the novel annular lens close to the pump light source is a convex lens surface protruding towards it, and the side of the novel annular lens close to the focusing lens is an annular convex surface with a double-arc longitudinal section. A laser resonator is formed between the two end faces of the gain medium. The divergent light beam output by the pump source is converged and shaped into an annular light beam by the novel annular lens, and the annular light beam is focused by the focusing lens to form an annular focused spot, and the annular focused spot is used to excite the gain medium to achieve the output of a vortex beam.

[0008] Preferably, the pump source is a fiber-coupled semiconductor laser.

[0009] Preferably, the novel annular lens and the focusing lens form an annular pump beam coupling system for pumping the gain medium to generate a vortex beam.

[0010] Preferably, a dichroic film with high transmittance for pump light and total reflection for oscillating light is coated on the pump light incident end face of the gain medium as the total reflection mirror of the laser resonator, and a partial reflection film for oscillating light is coated on the other end face as the output mirror of the laser resonator.

[0011] Preferably, the transmittance T1 of the dichroic film > 97%.

[0012] Preferably, the reflectivity R of the dichroic film > 99%.

[0013] Preferably, the light intensity distribution of the pump beam emitted by the pump source is a Gaussian distribution.

[0014] Preferably, the lens convex surface on one side of the novel annular lens is an arc-shaped curved surface, and its radius of curvature is smaller than that of the annular convex surface on the other side.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention uses a novel annular lens to shape the Gaussian beam emitted by the pump source into an annular hollow beam. After being focused by the focusing lens, the vortex beam is output through the gain medium. Using this novel annular lens can greatly reduce the size of the pump unit, making the laser structure more compact and with high integration.

[0017] 2. The novel annular lens in the present invention has no defect of power loss compared with existing defective lenses, etc., and can achieve high-efficiency shaping. By cooperating with different focusing lenses, annular focused spots with diameters ranging from dozens to hundreds of micrometers can be obtained, thereby obtaining high-efficiency oscillating laser output. Description of the Drawings

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a cross-sectional view of an axicon lens used to obtain an annular beam in the background art;

[0020] Figure 2 It is a cross-sectional view of a defective lens used to obtain an annular beam in the background art;

[0021] Figure 3 It is a schematic structural diagram of a vortex light laser based on a novel pump structure of the present invention;

[0022] Figure 4 It is a schematic cross-sectional view of a novel annular lens in an embodiment of the present invention;

[0023] Figure 5 It is a schematic diagram of the principle of shaping a pump beam by a novel annular lens in an embodiment of the present invention;

[0024] Figure 6 It is a schematic three-dimensional model diagram of a novel annular lens in an embodiment of the present invention;

[0025] Figure 7 It is the result of simulating the Gaussian beam emitted from a pump source after being shaped by a novel annular lens using optical simulation software. The area composed of white dots in the figure represents the shape of the annular beam;

[0026] Explanation of reference numerals:

[0027] 1: Pump source; 2: Novel annular lens; 3: Focusing lens; 4: Gain medium; 4-1: Crystal pump light incident end face; 4-2: Crystal laser output end face; 5: Convex lens surface; 6: Annular convex surface; 7: Outer beam; 8: Inner beam; 9: Annular beam focus point. Specific embodiments

[0028] The following will clearly and completely describe the technical solutions of the present invention in combination with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0029] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0030] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined. In addition, the terms "mounted", "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] As Figure 3 - 7 shown, the present invention provides a vortex light laser based on a novel pump structure, comprising: a pump source 1, a novel annular lens 2, a focusing lens 3 and a gain medium 4 arranged in sequence along the light propagation direction, wherein the pump source 1 is a fiber-coupled semiconductor laser with the wavelength of the emitted pump beam being 808 nm. One side of the novel annular lens 2 close to the pump light source 1 is a convex lens surface 5 protruding towards it, and one side of the novel annular lens 2 close to the focusing lens 3 is an annular convex surface 6 with a double-arc longitudinal section. A laser resonator is formed between the two end faces of the gain medium 4. The divergent beam output by the pump source 1 is converged and shaped into an annular beam by the novel annular lens 2, and the annular beam is focused by the focusing lens 3 to form an annular focused spot, and the annular focused spot is excited by the gain medium 4 to realize the output of the vortex beam.

[0032] The longitudinal sectional view of the novel annular lens 2 is as Figure 4As shown, the lens convex surface 5 on the left side of the novel annular lens 2 is an arc-shaped curved surface, and its radius of curvature is smaller than that of the annular convex surface 6 on the other side. In this embodiment, the diameter R1 of the novel annular lens 2 is 10 mm, the radius of curvature R2 of the lens convex surface 5 is 5.19 mm, and the radius of curvature R3 of a single arc in the longitudinal section of the annular convex surface 6 is 19 mm. The novel annular lens 2 and the focusing lens 3 form an annular pump beam coupling system for pumping the gain medium to generate a vortex beam. The distance between the pump source 1 and the novel annular lens 2 is 10 mm. The pump beam with a Gaussian intensity distribution emitted by the pump source 1 is shaped into a beam with an annular intensity distribution by the novel annular lens 2, and then further focused by the focusing lens 3 into a small-sized annular focused spot to end-pump the gain medium 4, realizing the output of the vortex beam.

[0033] Specifically, as Figure 5 shown, the divergent pump beam output from the optical fiber of the pump source 1 is incident on the lens convex surface 5 of the novel annular lens 2. The lens convex surface 5 converges the divergent pump beam into a nearly parallel light. The light entering the novel annular lens 2 can be divided into two parts: one part is the outer beam 7 located outside the arc vertex of the annular convex surface 6, and the other part is the inner beam 8 located inside the arc vertex. When the pump beam passes through the annular convex surface 6, the outer beam 7 converges inward, and the inner beam 8 converges outward, jointly focusing on the annular beam focus point 9. The generated annular beam is further focused by the focusing lens 3, and an annular focused spot with a size of dozens to hundreds of micrometers can be formed.

[0034] In this embodiment, the gain medium 4 is made of Nd:YAG crystal. The crystal pump light incident end face 4-1 of the gain medium 4 is coated with a dichroic film with high transmittance (transmittance T1 > 97%) for 808 nm pump light and total reflection (reflectivity R > 99%) for 1064 nm oscillating light as the total reflection mirror of the laser resonator. The other end of the crystal laser output end face 4-2 is coated with a partial reflection film for 1064 nm oscillating light as the output mirror of the laser resonator, and its transmittance T2 = 10%. Since the intensity of the vortex beam is annularly distributed, the annular focused spot generated by using the novel pump structure end-pumps the gain medium 4, and the vortex beam and the pump light can achieve better mode matching, oscillate preferentially in the resonator, and realize the output of the vortex beam.

[0035] It should be noted that the gain medium 4 in this embodiment uses Nd:YAG crystal, but it is not the only option. Other laser gain media can also be selected according to different output parameters.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vortex light laser based on a novel pump structure, characterized in that Including: A pump source, a novel annular lens, a focusing lens, and a gain medium are arranged in sequence along the light propagation direction. The side of the novel annular lens close to the pump light source is a convex lens surface protruding towards it. The side of the novel annular lens close to the focusing lens is an annular convex surface with a double-arc longitudinal section. A laser resonator cavity is formed between the two end faces of the gain medium. The divergent light beam output by the pump source is converged and shaped into an annular light beam by the novel annular lens. The annular light beam is focused by the focusing lens to form an annular focused light spot. The annular focused light spot is excited through the gain medium to achieve the output of a vortex light beam.

2. The vortex light laser based on the novel pump structure according to claim 1, characterized in that, The pump source is a fiber-coupled semiconductor laser.

3. The vortex light laser based on the novel pump structure according to claim 1, characterized in that, The novel annular lens and the focusing lens form an annular pump beam coupling system for pumping the gain medium to generate a vortex light beam.

4. The vortex optical laser based on the novel pump structure according to claim 1, characterized in that, The pump light incident end face of the gain medium is coated with a dichroic film that is highly transmissive to pump light and fully reflective to oscillating light as the total reflection mirror of the laser resonator cavity, and the other end face is coated with a partial reflection film of oscillating light as the output mirror of the laser resonator cavity.

5. The vortex light laser based on the novel pumping structure according to claim 4, wherein The transmittance T1 of the dichroic film is > 97%.

6. The vortex light laser based on the novel pumping structure according to claim 4, characterized in that, The reflectivity R of the dichroic film is > 99%.

7. The vortex optical laser based on the novel pump structure according to claim 2, characterized in that The light intensity distribution of the pump beam emitted by the pump source is a Gaussian distribution.

8. The vortex light laser based on the novel pump structure according to claim 1, characterized in that, The lens convex surface on one side of the novel annular lens is an arc-shaped curved surface, and its curvature radius is smaller than the curvature radius of the annular convex surface on the other side.

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