A fiber coupling system based on synchronous fast axis compression and slow axis self-polarization prism

Abstract

The application discloses a fiber coupling system based on synchronous fast-axis compression and slow-axis self-polarization prism, comprising a plurality of groups of semiconductor laser stacks composed of a plurality of bars; the output of each bar in each group of semiconductor laser stacks is collimated by a fast-axis collimating lens and a slow-axis collimating lens, then is incident on a synchronous fast-axis compression and slow-axis self-polarization prism through a half-wave plate arranged along the slow-axis direction of the beam half-width, so that the light beam is offset in the fast-axis direction and is polarized and combined with the light beam in the slow-axis direction after the light beam in the slow-axis direction is polarized and combined, and the light of each adjacent two bars is offset in the fast-axis direction and is close to each other; the emergent light beam of the prism is compressed and filled by a beam compression and filling prism, then is combined by a wavelength combining mirror, and is focused and coupled into a target optical fiber by an aspheric lens. The application can offset and compress the dark area of the light beam in the fast-axis direction, and combines the polarization and combining technology, so that the light beam in the slow-axis direction is polarized and combined, and the uniform light beam quality is achieved.

Description

Technical Field

[0001] This invention relates to an optical fiber coupling system. Background Technology

[0002] Semiconductor lasers are widely used in industrial processing, laser pumping, and biomedicine due to their advantages of small size, long lifespan, and high electro-optical conversion efficiency. To increase power, light-emitting bars are stacked vertically, which can lead to dark areas in the beam along the fast axis and uneven beam quality along the fast and slow axes. This makes it difficult for the beam to couple into the target fiber, making the beam shaping function of the fiber coupling module crucial.

[0003] Current mainstream beam shaping methods for addressing beam quality inhomogeneity primarily utilize reflection and refraction techniques to cut and rearrange the slow-axis beam, such as double-cut beam shaping and step-cut rotating prisms, to achieve uniform beam quality between the fast and slow axes. They then use total internal reflection effects, such as step mirrors, to compress the beam and eliminate dark areas. However, these methods require a large number of prisms, demand high manufacturing precision, are difficult to adjust, and have low coupling efficiency. Summary of the Invention

[0004] Purpose of the invention: In view of the above-mentioned prior art, an optical fiber coupling system based on synchronous fast-axis compression and slow-axis self-polarizing prism is proposed. Without the need for step mirrors, stripe prisms or prism stacks, the system utilizes the beam compression of the dark area in the fast-axis direction and the polarization combining of the slow-axis direction to uniformly improve the beam quality on both the fast and slow axes, which greatly reduces the number of prisms used and achieves efficient optical fiber coupling.

[0005] Technical Solution: A fiber optic coupling system based on a synchronous fast-axis compression and slow-axis self-polarizing prism includes: several groups of semiconductor laser stacks composed of multiple bars; the output of each bar in each semiconductor laser stack is collimated by a fast-axis collimating lens and a slow-axis collimating lens, and then incident on a half-wave plate with a beam half-width set along the slow axis direction onto the synchronous fast-axis compression and slow-axis self-polarizing prism, causing the beam to be deflected in the fast axis direction and combined with the beam polarized in the slow axis direction before exiting, and the light from each pair of adjacent bars in the semiconductor laser stack is deflected and moved closer to each other in the fast axis direction; the exit beam of the synchronous fast-axis compression and slow-axis self-polarizing prism is then compressed and filled by a beam compression and filling prism; the light from each semiconductor laser stack after compression and filling is combined by a wavelength beam combiner and then focused and coupled into the target fiber by an aspherical lens.

[0006] Furthermore, each bar in the semiconductor laser stack corresponds to one of the aforementioned synchronous fast-axis compression and slow-axis self-polarizing prisms, and each pair of adjacent synchronous fast-axis compression and slow-axis self-polarizing prisms are mirrored.

[0007] The prism that simultaneously achieves fast-axis compression and slow-axis self-polarization is obtained by cutting an orthographic prism. The specific cutting method includes the following steps:

[0008] Step 1: According to the system design, the offset of the beam of each bar in the fast axis direction is Δh, the refractive index of the rhombus prism is n1, the length of the rhombus prism along the beam axis is l, and the base angle θ of the parallelogram of the side of the rhombus prism along the beam axis direction is calculated according to the formula.

[0009]

[0010] Where n is the relative refractive index of the rhombic prism;

[0011] Step 2: Determine the height of the rhombic prism based on the distance H between adjacent bars, determine the width of the rhombic prism based on the slow axis width D of the beam, and then combine l and θ to obtain the specific shape of a single rhombic prism.

[0012] Step 3: After the collimated beam enters the rhombic prism, it is deflected along the fast axis. Using the beam deflection surface as the reference surface, the rhombic prism is cut by two surfaces with a distance of D / 2 at a 45° angle perpendicular to the reference surface. The triangular prism that is directly opposite the half-wave plate after cutting is discarded, and a P-polarized light thin film is coated on the other cut surface.

[0013] Furthermore, the offset of each bar beam in the fast axis direction is Δh = 0.669 mm, the length of the rhombic prism along the beam axis is l = 5.2 mm, the refractive index of the rhombic prism is n1 = 1.516, and the base angle θ of the parallelogram of the side of the rhombic prism along the beam axis is 70°.

[0014] Furthermore, the spacing H between adjacent bars ranges from 1.6 to 1.9 mm.

[0015] Furthermore, the light source wavelengths of each semiconductor laser stack are different.

[0016] Furthermore, the beam compression filling prism consists of three isosceles right-angled triangular prisms spaced apart along the beam width direction.

[0017] Furthermore, the fast-axis collimating lens is an aspherical microcylindrical lens (FAC), and the slow-axis collimating lens is a cylindrical microlens array (SAC).

[0018] Furthermore, the three isosceles right-angled triangular prisms in the beam compression filling prism have the same height, with the height ranging from 5 to 10 mm.

[0019] Beneficial effects: This invention can offset the beam along the fast axis to compress the dark area and combine it with polarization beam combining technology to achieve beam polarization beam combining along the slow axis, resulting in uniform beam quality. This invention does not require cutting and rearranging techniques such as double-cut beam shaping or step-cutting rotating prisms to achieve uniform beam quality and fill the dark area along both axes. The entire beam shaping process is simple, compact, practical, easy to set up and implement, and has high coupling efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the optical fiber coupling system of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of the fiber optic coupling system of the present invention before the simultaneous realization of fast-axis compression and slow-axis self-polarizing prism cutting.

[0022] Figure 3 This is a schematic diagram of the structure of the fiber optic coupling system of the present invention after synchronous fast-axis compression and slow-axis self-polarizing prism cutting.

[0023] Figure 4 This is a top view of the optical fiber coupling system of the present invention after synchronous fast-axis compression and slow-axis self-polarizing prism cutting.

[0024] Figure 5 This is the optical path diagram for the simultaneous realization of fast-axis compression and slow-axis self-polarizing prism beam offset compression in the optical fiber coupling system of the present invention.

[0025] Figure 6 This is an optical path diagram of slow-axis beam polarization combining based on synchronous realization of fast-axis compression and slow-axis self-polarizing prism in the fiber coupling system of the present invention.

[0026] Figure 7 This is the optical path diagram of the fast-axis beam offset compression and slow-axis beam polarization combining based on the synchronous realization of fast-axis compression and slow-axis self-polarizing prisms in the fiber coupling system of the present invention.

[0027] Figure 8 This is a schematic diagram of the beam compression filling prism in the fiber optic coupling system of the present invention;

[0028] Figure 9 The optical path diagram for beam compression and filling in the fiber coupling system of this invention is shown. Detailed Implementation

[0029] The invention will now be further explained with reference to the accompanying drawings.

[0030] like Figure 1As shown, an optical fiber coupling system based on synchronous fast-axis compression and slow-axis self-polarizing prism includes: three sets of semiconductor laser stacks 1, each semiconductor laser stack 1 is composed of 8 cm-bar bars, the spacing of each bar is H = 1.8 mm, and the light source is P polarized; each set of semiconductor laser stacks 1 outputs a different wavelength, denoted as λ1, λ2, and λ3 respectively.

[0031] Each semiconductor laser stack 1 is equipped with a fast-axis collimating lens 4, a slow-axis collimating lens 5, a half-wave plate 6, a prism 7 that simultaneously achieves fast-axis compression and slow-axis self-polarization, and a beam compression and filling prism 9 before its output end. Specifically, the output beam of each bar in each semiconductor laser stack 1 is collimated by the fast-axis collimating lens 4 and the slow-axis collimating lens 5, and then horizontally incident on the prism 7 that simultaneously achieves fast-axis compression and slow-axis self-polarization via the half-width of the beam along the slow axis. This causes the beam to deflect in the fast-axis direction and combine with the beam in the slow-axis direction before exiting. Simultaneously, the light from each pair of adjacent bars in each semiconductor laser stack 1 is offset and approaches each other in the fast-axis direction, such as... Figure 5 As shown.

[0032] The emitted beams from the synchronous fast-axis compression and slow-axis self-polarizing prism 7 corresponding to each semiconductor laser stack 1 are then compressed and filled by the beam compression and filling prism 9. After compression and filling, the light from each semiconductor laser stack 1 is combined by the wavelength beam combiner 10 to increase its power, and then focused and coupled into the target optical fiber 13 by the aspherical lens 12.

[0033] In this system, each bar output in each semiconductor laser stack 1 is directly opposite a synchronous fast-axis compression and slow-axis self-polarizing prism 7, and every two adjacent synchronous fast-axis compression and slow-axis self-polarizing prisms 7 are mirrored. For example... Figures 2 to 4 As shown, the fast-axis compression and slow-axis self-polarizing prism 7 is obtained by cutting an orthorhombic prism. The specific cutting method includes the following steps:

[0034] Step 1: According to the system design, the offset of each bar beam in the fast axis direction is Δh, the refractive index of the rhombic prism is n1, the refractive index of air is n0, then the relative refractive index n = n1 / n0, the length l of the rhombic prism along the beam axis direction, and the base angle θ of the parallelogram of the side of the rhombic prism along the beam axis direction are calculated according to the formula.

[0035]

[0036] Where n is the relative refractive index of the rhombic prism;

[0037] Step 2: Determine the height of the rhombic prism based on the distance H between adjacent bars, determine the width of the rhombic prism based on the slow axis width D of the beam, and then combine l and θ to obtain the specific shape of a single rhombic prism.

[0038] Step 3: After the collimated beam is incident on the rhomboid prism, it is deflected along the fast axis. The beam deflection surface is used as the reference surface. The rhomboid prism is cut with two surfaces of D / 2 at a 45° angle perpendicular to the reference surface. The triangular prism that is directly opposite the half-wave plate 6 after cutting is discarded. A thin film for passing through P polarized light is coated on another cut surface.

[0039] like Figure 6 , Figure 7 As shown, the portion of the half-width beam of each bar whose polarization state is changed by the half-wave plate 6, that is, the portion whose polarization state changes from P polarization to S polarization, is incident into the first prism between the two cutting surfaces. The other portion, still in P polarization, is directly incident into the right-angle prism on one side. The S polarization portion undergoes two reflections in the first prism. Because the inclined surface (i.e., the cutting surface) of the right-angle prism is coated with a thin film that allows P polarization to pass through, the S polarization beam is reflected and emitted. That is, the first prism acts as a deflector of the optical axis. The P polarization beam incident from the right-angle surface of the right-angle prism can be directly transmitted through the coating on the inclined surface and combined with the beam in the first prism before being output. This completes the beam polarization combination in the slow axis direction, achieving uniform beam quality in both the fast and slow axis directions.

[0040] In this embodiment, in order to reduce phase difference and divergence angle after collimation to improve efficiency, the fast-axis collimating lens 4 is an aspherical microcylindrical lens FAC, and the slow-axis collimating lens 5 is a cylindrical microlens array SAC.

[0041] To simultaneously achieve fast-axis compression and slow-axis self-polarizing, the material refractive index of the prism 7 is n1 = 1.516, and the refractive index of air is n0 = 1. Therefore, the relative refractive index n = n1 / n0 = 1.516. The design induces a beam offset Δh = 0.669 mm along the fast axis. Thus, after the light from each pair of adjacent bars in the semiconductor laser stack 1 shifts and approaches each other along the fast axis, the distance becomes H-2Δh = 0.462 mm, achieving dark area compression. The inclined surface of the right-angle prism is coated with a P-polarized thin film, enabling polarization combining of the beam along the slow axis to achieve uniform beam quality in both the fast and slow axis directions.

[0042] In the specific design process of the fast-axis compression and slow-axis self-polarizing prism 7 of this invention, based on the pre-determined three parameters among Δh, n1, θ, and l, the value of the third parameter can be calculated using a formula. For example... Figure 3As shown, the height of the rhombic prism is 1.8 mm, the width is 10 mm, the length of the rhombic prism along the optical axis of the beam is l = 5.2 mm, the base angle θ of the parallelogram side of the rhombic prism along the optical axis of the beam is 70°, the refractive index of air is n0 = 1, the refractive index of the prism material is n1 = 1.516, and the relative refractive index is n = n1 / n0 = 1.516. These values ​​can be calculated using Snell's law and geometric relationships.

[0043]

[0044] The prism 7, obtained by cutting to simultaneously achieve fast-axis compression and slow-axis self-polarization, is, in its top view, a parallelogram and two isosceles right triangles. The adjacent side lengths of the parallelogram are 5mm and 7.07mm, and the base angle is 45°. The right-angled side length of the isosceles right triangle is 5mm. The prism retains the parallelogram and lower isosceles right-angled triangle portion in its top view. After passing through the prism, the beam is deflected and compressed by a height Δh = 0.669mm in the fast-axis direction, and the distance between adjacent beams is H-2Δh = 0.462mm.

[0045] like Figure 9 As shown, the beam compression filling prism 9 is used to reflect and fill the beam. For example... Figure 8 As shown, the beam compression filling prism 9 consists of three isosceles right-angled triangular prisms spaced apart along the beam width direction. The two isosceles right-angled triangular prisms on the sides have a base right angle side length of 0.7mm, a hypotenuse length of 0.99mm, and a prism height of 10mm. The middle isosceles right-angled triangular prism has a base right angle side length of 2.22mm, a hypotenuse length of 3.14mm, and a prism height of 10mm.

[0046] Both first-wavelength beam combiners 10 are coated with thin films of transmission wavelength λ1 and reflection wavelengths λ2 and λ3 to complete wavelength beam combining and improve power.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fiber optic coupling system based on synchronous fast-axis compression and a slow-axis self-polarizing prism, characterized in that, include: Several groups of semiconductor laser stacks (1) are composed of multiple bars; the output of each bar in each group of semiconductor laser stacks (1) is collimated by a fast-axis collimating lens (4) and a slow-axis collimating lens (5), and then incident on a half-wave plate (6) set along the half-width of the beam in the slow axis direction to a prism (7) that simultaneously realizes fast-axis compression and slow-axis self-polarization, so that the beam is deflected in the fast axis direction and combined with the beam in the slow axis direction before exiting. The light of each two adjacent bars in the semiconductor laser stack (1) is deflected and close to each other in the fast axis direction; the outgoing beam of the prism (7) that simultaneously realizes fast-axis compression and slow-axis self-polarization is then compressed and filled by a beam compression filling prism (9); the light of each semiconductor laser stack (1) after compression and filling is combined by a wavelength beam combiner (10) and then focused and coupled into the target fiber (13) by an aspherical lens (12); In the semiconductor laser stack (1), each bar corresponds to one of the synchronous fast axis compression and slow axis self-polarizing prisms (7), and each pair of adjacent synchronous fast axis compression and slow axis self-polarizing prisms (7) are mirrored. The synchronous fast-axis compression and slow-axis self-polarizing prism (7) is obtained by cutting an orthographic prism. The specific cutting method includes the following steps: Step 1: According to the system design, the offset of the beam of each bar in the fast axis direction is Δh, the refractive index of the rhombus prism is n1, the length of the rhombus prism along the beam axis is l, and the base angle θ of the parallelogram of the side of the rhombus prism along the beam axis direction is calculated according to the formula. Step 2: Determine the height of the rhombic prism based on the distance H between adjacent bars, determine the width of the rhombic prism based on the slow axis width D of the beam, and then combine l and θ to obtain the specific shape of a single rhombic prism. Step 3: After the collimated beam enters the rhombic prism, it is deflected along the fast axis. The beam deflection surface is used as the reference surface. The rhombic prism is cut by two surfaces with a distance of D / 2 at a 45° angle perpendicular to the reference surface. The triangular prism that is directly opposite the half-wave plate (6) after cutting is discarded, and a P-polarized light thin film is coated on the other cut surface.

2. The fiber optic coupling system according to claim 1, characterized in that, The offset of the beam of each bar in the fast axis direction is Δh = 0.669 mm, the length of the rhombic prism along the beam axis is l = 5.2 mm, the refractive index of the rhombic prism is n1 = 1.516, and the base angle θ of the parallelogram of the side of the rhombic prism along the beam axis is 70°.

3. The fiber optic coupling system according to claim 1, characterized in that, The spacing H between adjacent bars ranges from 1.6 to 1.9 mm.

4. The fiber optic coupling system according to any one of claims 1-3, characterized in that, The light source wavelengths of each group of semiconductor laser stacks (1) are different.

5. The fiber optic coupling system according to any one of claims 1-3, characterized in that, The beam compression filling prism (9) consists of three isosceles right-angled triangular prisms spaced apart along the beam width direction.

6. The fiber optic coupling system according to any one of claims 1-3, characterized in that, The fast-axis collimating lens (4) is an aspherical micro-cylindrical lens (FAC), and the slow-axis collimating lens (5) is a cylindrical microlens array (SAC).

7. The fiber optic coupling system according to claim 5, characterized in that, The three isosceles right-angled triangular prisms in the beam compression filling prism (9) have the same height, and the height range is 5 to 10 mm.

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