A microlens based on two-photon polymerization technology and a manufacturing method thereof

Abstract

The application discloses a light spot shaping microlens based on a two-photon polymerization technology and a manufacturing method thereof, and relates to the technical field of optics and micro-nano processing technology. The light spot shaping microlens based on the two-photon polymerization technology is a cylindrical lens array structure, comprises at least two cylindrical lenses arranged in parallel in sequence, and the fixed arrangement of the cylindrical lenses is realized through support structures on both sides of the cylindrical lenses, and the straight surfaces of the cylindrical lenses are parallel; the cylindrical lens array structure is used for modulating a circular laser spot of incident laser into an elliptical spot. The cylindrical lens array structure is prepared by adopting the two-photon polymerization technology, the machining precision reaches the nanometer level, the accurate preparation of a three-dimensional complex structure can be realized, and the problem that a micro-scale three-dimensional optical structure cannot be prepared by using a traditional process is solved; the prepared microlens can be integrated with a VCSEL (Vertical Cavity Surface Emitting Laser) efficiently, the accurate modulation from a circular spot to an elliptical spot is realized, and the demand of high-precision micro-nano displacement detection is met.

Description

Technical Field

[0001] This invention relates to the fields of optics and micro / nano fabrication technology, specifically to a spot-shaping microlens based on two-photon polymerization technology and its manufacturing method. Background Technology

[0002] On a macroscopic scale, for light sources larger than millimeters, conventional optical lenses or masks can typically be used to control the shape of the light spot. However, with the rapid development of micro-nano photonics and integrated optoelectronics, microscale light sources have gained widespread application in recent years. For example, micrometer-scale vertical-cavity surface-emitting lasers (VCSELs) have played a crucial role in cutting-edge fields such as high-speed optical communication, 3D sensing, and lidar due to their advantages of low power consumption, high spectral purity, small size, and ease of integration. However, the huge scale difference between these micrometer-scale light sources and traditional millimeter-scale optical components presents significant challenges in optical coupling, integrated packaging, and system miniaturization. Therefore, developing microlenses that can be directly integrated with microscale light sources and achieving efficient and flexible spot shaping has become an important research direction in the fields of micro-optics and micro-nano fabrication.

[0003] In the fabrication of microlenses, traditional microelectromechanical systems (MEMS) processes have been widely adopted. For example, combining photoresist patterning with thermal reflow technology can produce microlens arrays with consistent morphology and controllable dimensions; microlens arrays can also be fabricated using multi-size aperture photomask technology combined with controllable chemical wet etching. However, these multi-process combinations are not only complex and costly, but also often lead to a decrease in the precision of lens curvature control, limiting their application in the fabrication of aspherical and complex surface microlenses. In recent years, electrohydrodynamic inkjet (E-jet) technology has provided another effective path for microlens fabrication. This technology uses electric field-driven microdroplet deposition to form high-quality spherical lens structures and has been successfully applied in beam focusing and simple imaging fields. However, E-jet technology is mainly limited to fabricating regularly arranged spherical microlens arrays on planar substrates, and it is still difficult to achieve the controllable fabrication of three-dimensional complex lens structures, such as aspherical and freeform lenses, thus still having significant shortcomings in meeting the needs of complex optical path shaping. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a spot-shaping microlens based on two-photon polymerization technology and its manufacturing method. The prepared microlens can control the shape of the spot of a microscale light source. The preparation process utilizes two-photon polymerization technology to prepare 3D microlenses or microlens groups, which can be integrated with a microscale light source and shape a circular spot into an elliptical spot. The shaped elliptical spot can improve the spot displacement detection sensitivity of a position-sensitive device (PSD).

[0005] The technical solution of this invention is as follows:

[0006] On one hand, the present invention provides a spot-shaping microlens based on two-photon polymerization technology, which is a cylindrical lens array structure, including at least two cylindrical lenses arranged in parallel in sequence, and the cylindrical lenses are fixedly arranged by the support structure on both sides of the cylindrical lenses, and the straight surfaces of the cylindrical lenses are parallel; the cylindrical lens array structure is used to modulate the circular laser spot of the incident laser into an elliptical laser spot.

[0007] Furthermore, the cylindrical lens is made of a photopolymer material, and the photopolymerization parameters of the photopolymer material are adjustable.

[0008] Furthermore, in the cylindrical lens array structure, the curvature of all cylindrical lenses is adjustable to achieve an adjustable ratio of the major axis to the minor axis of the elliptical light spot.

[0009] Furthermore, the distance between all cylindrical lenses and the vertical cavity surface-emitting laser (VCSEL), which serves as the light source, is adjustable, enabling the size of the elliptical laser spot to be dynamically adjusted with distance.

[0010] On the other hand, the present invention provides an integrated component of a spot-shaping microlens based on two-photon polymerization technology, including a vertical cavity surface-emitting laser and a cylindrical lens array structure;

[0011] The vertical cavity surface emitter (VCSEL) is placed horizontally on the operating table and is used to emit laser light in a direction perpendicular to the horizontal plane and directly above it. The cylindrical lens array structure is placed directly above the VCSEL, so that the laser light passes through each cylindrical lens in the cylindrical lens array structure in sequence, modulating the circular laser spot into an elliptical spot.

[0012] Thirdly, this application proposes a method for manufacturing a spot-shaping microlens based on two-photon polymerization technology, comprising the following steps:

[0013] Determine the parameters of the vertical cavity surface-emitting laser, including its size, laser wavelength, and divergence angle;

[0014] Based on the parameters of a vertical cavity surface-emitting laser (VCSEL), optical simulation software was used to design the curvature of each cylindrical lens in the cylindrical lens array structure and its relative position to the VCSEL.

[0015] Based on the curvature of each cylindrical lens as designed, a cylindrical lens array structure is fabricated using two-photon polymerization technology;

[0016] According to the relative position of each cylindrical lens in the determined cylindrical lens array structure to the vertical cavity surface-emitting laser, the prepared cylindrical lens array structure is aligned with the vertical cavity surface-emitting laser, and encapsulated with photocurable adhesive to form an integrated component.

[0017] Furthermore, the fabrication of the cylindrical lens array structure using two-photon polymerization technology, based on the curvature of each designed cylindrical lens, specifically includes the following steps:

[0018] S1: The three-dimensional motion platform of the two-photon polymerization system is fixed after the substrate is cleaned and dried;

[0019] S2: Photoresist is coated on the substrate surface. First, the photoresist is exposed in shell polymerization mode with set precision parameters to obtain the first support structure. Then, the photoresist is exposed in layer-by-layer scanning polymerization mode with a higher precision than the set precision parameters to obtain the first cylindrical lens. The support structure and the cylindrical lens are exposed in sequence according to the exposure method of the first support structure and the first cylindrical lens until the set cylindrical lens is obtained, thus obtaining the lens array structure sample.

[0020] S3: After exposure, the lens array structure sample is developed in a developer and then cleaned in a cleaning agent to remove unpolymerized photoresist. Subsequently, the incompletely polymerized photoresist is cured in an ultraviolet curing chamber to obtain the cylindrical lens array structure.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention uses two-photon polymerization technology to prepare cylindrical lens array structures with nanometer-level processing precision, which can realize the precise preparation of complex three-dimensional structures and solve the problem that traditional processes cannot prepare microscale three-dimensional optical structures.

[0023] 2. The fabricated microlens can be efficiently integrated with VCSELs to achieve precise modulation from circular spot to elliptical spot, meeting the requirements for high-precision micro-nano displacement detection.

[0024] 3. The microlens uses photopolymer materials, which have high transmittance and good stability. After encapsulation, the component is small in size, which is compatible with the miniaturization characteristics of VCSELs and can be widely used in various integrated optical systems. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the working principle of the VCSEL-PSD displacement detection system in an embodiment of the present invention.

[0026] Figure 2 This is a scanning electron microscope image of the cylindrical lens array structure in an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the optical simulation of the cylindrical lens array structure in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the layered exposure process for fabricating a cylindrical lens array structure using two-photon polymerization in an embodiment of the present invention;

[0029] Figure 5 This is the displacement-voltage relationship curve of the circular light spot in an embodiment of the present invention;

[0030] Figure 6 This is the displacement-voltage relationship curve of the elliptical light spot in an embodiment of the present invention;

[0031] In the figure: 1 – Photopolymerization material (IP-S); 2 – Two-photon polymerization technology (TPP); 3 – Support structure; 4 – Cylindrical lens array structure (Lens1 is the first cylindrical lens, Lens2 is the second cylindrical lens); 5 – Vertical cavity surface-emitting laser (VCSEL). Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] Example 1:

[0034] This embodiment proposes a spot-shaping microlens based on two-photon polymerization technology, which is suitable for spot shaping of vertical cavity surface-emitting laser (VCSEL) 5 and can be widely used in high-precision micro-nano displacement detection, 3D sensing and optical communication.

[0035] A spot-shaping microlens based on two-photon polymerization technology is a cylindrical lens array structure, comprising at least two cylindrical lenses arranged in parallel in sequence, and the cylindrical lenses are fixedly arranged by support structures 3 on both sides of the cylindrical lenses, and the straight surfaces of the cylindrical lenses are parallel; the cylindrical lens array structure is used to modulate the circular laser spot of the incident laser into an elliptical laser spot.

[0036] The cylindrical lens is made of photopolymer material 1, and the photopolymerization parameters of the photopolymer material 1 are adjustable;

[0037] In the cylindrical lens array structure, the curvature of the first cylindrical lens is adjustable, and the curvature of the second cylindrical lens is adjustable, so as to achieve an adjustable ratio of the major axis to the minor axis of the elliptical light spot.

[0038] The distance between the first cylindrical lens and the vertical cavity surface-emitting laser (VCSEL) that serves as the light source is adjustable, and the distance between the second cylindrical lens and the VCSEL is also adjustable. This design ensures that the size of the elliptical spot dynamically adjusts with distance within a detection distance of 100 millimeters.

[0039] In this embodiment, a spot-shaping microlens based on two-photon polymerization technology is integrated into a VCSEL-PSD displacement detection system. By observing the improvement in the detection sensitivity of the VCSEL-PSD displacement detection system after integrating the spot-shaping microlens based on two-photon polymerization technology, the performance of the spot-shaping microlens based on two-photon polymerization technology provided by this invention is verified.

[0040] Under the condition that the total laser energy is constant, when the elliptical light spot moves along the minor axis direction, the current change amount in the four quadrants of the PSD is greater than that of the circular light spot; assuming the radius of the circular light spot is R, the major axis of the elliptical light spot is α, and the minor axis is β (α = R, β < R), through the derivation of the current change amount formula, it can be obtained that when the elliptical light spot moves the same displacement Δy along the minor axis direction, the current change amount ΔI elliptical > ΔI circle , where ΔI elliptical is the current change amount when the elliptical light spot moves the same displacement Δy along the minor axis direction, and ΔI circle is the current change amount when the circular light spot moves the same displacement Δy along the same direction; and the smaller the minor axis β, the larger the current change amount ΔI elliptical , the higher the detection sensitivity, and the smaller the detection range. As Figure 1 shown, it proves that a spot-shaping microlens based on two-photon polymerization technology provided in the present invention can achieve adjustable improvement amplitude of detection sensitivity by adjusting the value of β, and its value should balance sensitivity and detection range to achieve an optimal balance between sensitivity improvement and range loss.

[0041] Example 2:

[0042] This example also provides an integrated component of a spot-shaping microlens based on two-photon polymerization technology. As Figure 2 shown, it includes a vertical-cavity surface-emitting laser (VCSEL) and a cylindrical lens array structure;

[0043] The vertical-cavity surface-emitting laser (VCSEL) is horizontally placed on the operating table and is used to emit laser in the direction perpendicular to the directly above of the horizontal plane. The cylindrical lens array structure is placed directly above the vertical-cavity surface-emitting laser (VCSEL), so that the laser passes through each cylindrical lens in the cylindrical lens array structure in turn, and modulates the circular laser spot into an elliptical light spot.

[0044] Example 3:

[0045] This example also provides a manufacturing method of a spot-shaping microlens based on two-photon polymerization technology, including the following steps:

[0046] Step 1: Determine the parameters of the vertical-cavity surface-emitting laser (VCSEL), including size, laser wavelength, divergence angle, etc.;

[0047] The method for determining the divergence angle is: measure the diameters D1 and D2 of the circular light spot at the set distance d1 and the set distance d2 from the circular light spot of the vertical-cavity surface-emitting laser (VCSEL) respectively, and obtain the divergence angle of the vertical-cavity surface-emitting laser (VCSEL) through geometric calculation, providing basic parameters for lens design;

[0048] In this embodiment, a test platform based on a beam quality analyzer was constructed. The parameters of the vertical-cavity surface-emitting laser (VCSEL) are: size 1000 μm × 235 μm × 150 μm, laser wavelength 850 nm, and laser array spacing 250 μm. The spot diameter D1 = 3.494 mm was measured at a set distance d1 = 8 mm, and D2 = 4.853 mm was measured at a set distance d2 = 11.5 mm. The divergence angle was calculated to be 10.5°.

[0049] Step 2: Based on the parameters of the vertical-cavity surface-emitting laser (VCSEL), use optical simulation software to design the curvature of each cylindrical lens in the cylindrical lens array structure and its relative position to the VCSEL.

[0050] In this embodiment, an optical simulation software was used to design a cylindrical lens array structure. The first cylindrical lens has a curvature of 0.09 mm and is 0.09 mm away from the vertical-cavity surface-emitting laser (VCSEL); the second cylindrical lens has a curvature of 0.185 mm and is 0.303 mm away from the VCSEL. Simulation verification shows that at 11.5 mm, the major axis of the elliptical spot is 4.395 mm, the minor axis is 2.098 mm, and the major axis / minor axis ratio is approximately 2. Figure 3 As shown. Simulation results demonstrate that this design can modulate a circular light spot into an elliptical light spot while maintaining a stable shaping effect within a range of 100 millimeters;

[0051] Step 3: Based on the curvature of each cylindrical lens in the design, fabricate the cylindrical lens array structure using two-photon polymerization technology, such as... Figure 4 As shown;

[0052] Step 3.1: After cleaning and drying the substrate, fix it onto the three-dimensional motion platform of the two-photon polymerization system;

[0053] In this embodiment, the substrate is an ITO substrate (25×25 mm).

[0054] Step 3.2: Photoresist is coated on the substrate surface. First, the photoresist is exposed in shell polymerization mode with low precision parameters (2 μm) to obtain the first support structure 3. Then, the photoresist is exposed in layer-by-layer scanning polymerization mode with high precision parameters (100 nm) to obtain the first cylindrical lens. The support structure 3 and the cylindrical lens are exposed in sequence according to the exposure method of the first support structure and the first cylindrical lens until the set cylindrical lens is obtained, and the lens array structure sample is obtained.

[0055] In this embodiment, the photoresist is IP-S dedicated photopolymer material 1; the exposure parameters are: 25× oil immersion lens, laser power 5mW, and scanning speed 10 mm / s.

[0056] Step 3.3: After exposure, the lens array structure sample is developed in a developer and then cleaned in a cleaning agent to remove unpolymerized photoresist. Subsequently, the incompletely polymerized photoresist is cured in a UV curing chamber to improve the structural strength and obtain a cylindrical lens array structure.

[0057] In this embodiment, development was performed using a propylene glycol methyl ether acetate solution (99% concentration) for 20 minutes; cleaning was done with isopropanol (99% concentration) for 3 minutes; and curing was performed using a 15 W UV lamp for 10 minutes, resulting in a structural strength ≥5 MPa after curing.

[0058] Step 4: According to the relative positions of each cylindrical lens in the determined cylindrical lens array structure and the vertical cavity surface emitting laser (VCSEL), align the prepared cylindrical lens array structure and the VCSEL using a precision displacement platform, and encapsulate them with photocurable adhesive to form an integrated component, ensuring that the size is compatible with the VCSEL and meets the requirements of integrated applications.

[0059] In this embodiment, a displacement sensitivity testing platform was built after encapsulation. Test results show that the displacement sensitivity of the circular light spot is 1.428 V / mm, with a detection range of 7 mm; the displacement sensitivity of the elliptical light spot is 2.272 V / mm, with a detection range of 4.4 mm, representing a sensitivity improvement of 59.1%, which meets the design requirements. Figure 5 and Figure 6 As shown.

Claims

1. A spot-shaping microlens based on two-photon polymerization technology, characterized in that, It is a cylindrical lens array structure, including at least two cylindrical lenses arranged in parallel in sequence, and the cylindrical lenses are fixedly arranged by the support structure on both sides of the cylindrical lenses, and the straight surfaces of the cylindrical lenses are parallel; the cylindrical lens array structure is used to modulate the circular laser spot of the incident laser into an elliptical laser spot.

2. The spot-shaping microlens based on two-photon polymerization technology according to claim 1, characterized in that, The cylindrical lens is made of a photopolymer material, and the photopolymerization parameters of the photopolymer material are adjustable.

3. A spot-shaping microlens based on two-photon polymerization technology according to claim 1, characterized in that, In the cylindrical lens array structure, the curvature of all cylindrical lenses is adjustable to achieve an adjustable ratio of the major axis to the minor axis of the elliptical light spot.

4. A spot-shaping microlens based on two-photon polymerization technology according to claim 1, characterized in that, The distance between all cylindrical lenses and the vertical cavity surface-emitting laser (VCSEL), which serves as the light source, is adjustable, enabling the size of the elliptical laser spot to be dynamically adjusted with distance.

5. An integrated component for a spot-shaping microlens based on two-photon polymerization technology according to any one of claims 1-4, characterized in that, Includes a vertical-cavity surface-emitting laser and a cylindrical lens array structure; The vertical cavity surface emitter (VCSEL) is placed horizontally on the operating table and is used to emit laser light in a direction perpendicular to the horizontal plane and directly above it. The cylindrical lens array structure is placed directly above the VCSEL, so that the laser light passes through each cylindrical lens in the cylindrical lens array structure in sequence, modulating the circular laser spot into an elliptical spot.

6. A method for manufacturing a spot-shaping microlens based on two-photon polymerization technology as described in any one of claims 1-4, characterized in that, Includes the following steps: Determine the parameters of the vertical cavity surface-emitting laser, including its size, laser wavelength, and divergence angle; Based on the parameters of a vertical cavity surface-emitting laser (VCSEL), optical simulation software was used to design the curvature of each cylindrical lens in the cylindrical lens array structure and its relative position to the VCSEL. Based on the curvature of each cylindrical lens as designed, a cylindrical lens array structure is fabricated using two-photon polymerization technology; According to the relative position of each cylindrical lens in the determined cylindrical lens array structure to the vertical cavity surface-emitting laser, the prepared cylindrical lens array structure is aligned with the vertical cavity surface-emitting laser, and encapsulated with photocurable adhesive to form an integrated component.

7. The method for manufacturing a spot-shaping microlens based on two-photon polymerization technology according to claim 6, characterized in that, The process of fabricating a cylindrical lens array structure using two-photon polymerization technology based on the curvature of each designed cylindrical lens specifically includes the following steps: S1: The three-dimensional motion platform of the two-photon polymerization system is fixed after the substrate is cleaned and dried; S2: Photoresist is coated on the substrate surface. First, the photoresist is exposed in shell polymerization mode with set precision parameters to obtain the first support structure. Then, the photoresist is exposed in layer-by-layer scanning polymerization mode with a higher precision than the set precision parameters to obtain the first cylindrical lens. The support structure and the cylindrical lens are exposed in sequence according to the exposure method of the first support structure and the first cylindrical lens until the set cylindrical lens is obtained, thus obtaining the lens array structure sample. S3: After exposure, the lens array structure sample is developed in a developer and then cleaned in a cleaning agent to remove unpolymerized photoresist. Subsequently, the incompletely polymerized photoresist is cured in an ultraviolet curing chamber to obtain the cylindrical lens array structure.

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