Super-resolution micro lens and preparation method thereof

Abstract

The invention discloses a super-resolution micro lens and a preparation method thereof. The lens comprises a photoresist spherical micro lens and a mixed substrate plane lens which are sequentially arranged from top to bottom. The specific preparation method comprises the following steps: S1, preparing a photoresist cylinder on a quartz substrate; s2, reflowing the photoresist cylinder into a micron lens by using a photoresist reflowing process; s3, preparing a mixed substrate plane lens on the surface of the to-be-detected sample; and S4, transferring the micron lens to the surface of the mixed substrate plane lens. By changing the thickness of the mixed substrate plane lens, adjustment of the amplification coefficient and the numerical aperture can be realized, and compared with a micro lens without a mixed substrate, the micro lens has higher imaging resolution. The method has a wide prospect in the technical field of optical imaging.

Description

Technical Field

[0001] This invention relates to the field of optical microscopy imaging technology, specifically to a super-resolution microlens and its fabrication method. Background Technology

[0002] Research shows that micron-scale plano-convex lenses, especially hyperspherical and subspherical designs, exhibit superior imaging performance. By precisely controlling the geometric characteristics of these lenses, such as thickness, shape, and size, diverse variations in focal length and object distance can be effectively achieved, thereby allowing for on-demand adjustment of image magnification and numerical aperture to meet the needs of different optical applications.

[0003] Currently, the mainstream manufacturing process for micron-sized plano-convex lenses heavily relies on costly and technically complex top-down microfabrication methods, such as electron beam lithography and focused ion beam milling. In contrast, polymer solid immersion lenses offer simpler and more economical design and production processes; however, their inherent low refractive index (typically n < 1.6) remains a key factor limiting their optical and imaging performance. Subsequently, the scientific community has extensively explored the use of nanoparticle self-assembly technology to construct hemispheres for nanoscale imaging. Although nanoparticle materials themselves possess the advantage of high refractive index (n > 2), unavoidable interparticle gaps during assembly result in the final hemisphere having a refractive index lower than that of the material itself. Furthermore, these self-assembled hemispheres are fragile and susceptible to damage from external forces or liquid environments. In addition to the methods mentioned above, thermal reshaping and laser direct writing technologies have also been considered alternatives for manufacturing micron-sized plano-convex lenses. However, the application of these technologies is limited to specific materials with low melting points, and challenges remain in the precise control of lens geometry and the optimization of surface roughness. Meanwhile, the imaging performance of existing hemispherical micron-sized plano-convex lenses has reached the limit of this topographic design. Therefore, a new solution is urgently needed to address the aforementioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a super-resolution microlens and its fabrication method.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a super-resolution microlens, comprising a photoresist spherical microlens and a hybrid substrate planar lens arranged sequentially from top to bottom.

[0006] Furthermore, the hybrid substrate planar lens is a planar substrate made of a mixture of photoresist and propylene glycol methyl ether acetate.

[0007] Furthermore, the thickness of the hybrid substrate planar lens is from 100 nm to 10 μm.

[0008] In a second aspect, the present invention provides a method for preparing the above-mentioned super-resolution microlens, comprising the following steps:

[0009] Step S1: Prepare a photoresist cylinder on a quartz substrate;

[0010] Step S2: Use a photoresist reflow process to reflow the photoresist cylinder into a micron lens;

[0011] Step S3: Prepare a hybrid substrate planar lens on the surface of the sample to be tested;

[0012] Step S4: Transfer the micron lens to the surface of the hybrid substrate planar lens.

[0013] Step S1 is as follows: The quartz substrate is cleaned using acetone ultrasonication for 20 minutes. Afterward, the substrate is transferred to a hot plate and baked for 25 minutes. Photoresist (n~1.59) is uniformly coated onto the quartz substrate at 8000 rpm using a spin coater. Then, a pre-baking process at 70°C for 8 minutes is performed to evaporate the solvent inside the photolithography machine. Immediately afterwards, the photoresist is exposed for 50 seconds using a 25 μm diameter Cr disk mask.

[0014] Step S2 is as follows: The photoresist cylinder substrate is transferred to a hot plate and subjected to a photoresist reflow process at 190°C for 1 hour, causing it to reflow into a micron-sized lens under surface tension. The lens is then rigidly peeled off from the substrate to obtain a plano-convex lens with an aspect ratio of approximately 1:2.

[0015] Step S3 is as follows: The photoresist and PGMEA are thoroughly mixed at a volume ratio of 1:1 and then evenly coated onto the sample surface. By setting different times and speeds on the spin coater, substrate layers of varying thicknesses can be obtained.

[0016] Step S4 is as follows: The plano-convex lens is transferred to the substrate surface using a heated and stretched optical fiber. Ultrapure water is then added to cover both the plano-convex lens and the substrate, and the mixture is baked on a 70°C hot plate for 25 minutes. At this point, the plano-convex lens adheres firmly to the substrate, forming a planar-spherical microlens (PSML) with a higher numerical aperture.

[0017] Furthermore, the PSML amplification rate proposed in this invention is positively correlated with the thickness of the substrate layer, that is, the thicker the mixed substrate layer, the greater the PSML amplification rate.

[0018] Compared to existing technologies, this invention has the following advantages: It obtains a micron lens through a photoresist thermal reflow process, and further fabricates a hybrid substrate planar lens. Placing the hybrid substrate planar lens below the micron lens, and then thermally annealing, yields a planar-spherical microlens (PSML) with higher numerical aperture and magnification. Furthermore, thanks to the relationship between magnification and numerical aperture and the PSML's aspect ratio, PSMLs with different imaging effects can be obtained by fabricating substrate layers of varying thicknesses, further improving practicality. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a super-resolution microlens disclosed in this invention;

[0020] Figure 2 This is a flowchart of a method for preparing a super-resolution microlens disclosed in this invention. Detailed Implementation

[0021] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0022] like Figure 1 As shown, the present invention provides a super-resolution microlens, comprising a photoresist spherical microlens and a hybrid substrate planar lens arranged sequentially from top to bottom.

[0023] like Figure 2 As shown, a method for fabricating a super-resolution microlens specifically includes the following steps:

[0024] Step S1 is as follows: The quartz substrate is cleaned using acetone ultrasonication for 20 minutes. Afterward, the substrate is transferred to a hot plate and baked for 25 minutes. Photoresist (n~1.59) is uniformly coated onto the quartz substrate at 8000 rpm using a spin coater. Then, a pre-baking process at 70°C for 8 minutes is performed to evaporate the solvent inside the photolithography machine. Immediately afterwards, the photoresist is exposed for 50 seconds using a 25 μm diameter Cr disk mask.

[0025] Step S2 is as follows: The photoresist cylinder substrate is transferred to a hot plate and subjected to a photoresist reflow process at 190°C for 1 hour, causing it to reflow into a micron-sized lens under surface tension. The lens is then rigidly peeled off from the substrate to obtain a plano-convex lens with an aspect ratio of approximately 1:2.

[0026] Step S3 is as follows: The photoresist and PGMEA are thoroughly mixed at a volume ratio of 1:1 and then evenly coated onto the sample surface. By setting different times and speeds on the spin coater, substrate layers of varying thicknesses can be obtained.

[0027] Step S4 is as follows: The plano-convex lens is transferred to the substrate surface using a heated and stretched optical fiber. Ultrapure water is then added to cover both the plano-convex lens and the substrate, and the mixture is baked on a 70°C hot plate for 25 minutes. At this point, the plano-convex lens adheres firmly to the substrate, forming a planar-spherical microlens (PSML) with a higher numerical aperture.

[0028] The above description is merely a preferred embodiment of the present invention. It should be noted that for those skilled in the art, other parts not specifically described are existing technology or common knowledge. 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 super-resolution microlens, characterized in that, It includes photoresist spherical microlenses and hybrid substrate planar lenses arranged sequentially from top to bottom.

2. The super-resolution microlens according to claim 1, characterized in that, The hybrid substrate planar lens is a planar substrate made of a mixture of photoresist and propylene glycol methyl ether acetate.

3. The super-resolution microlens according to claim 1, characterized in that, The thickness of the hybrid substrate planar lens is from 100 nm to 10 μm.

4. A method for preparing a super-resolution microlens as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step S1: Prepare a photoresist cylinder on a quartz substrate; Step S2: Use a photoresist reflow process to reflow the photoresist cylinder into a micron lens; Step S3: Prepare a hybrid substrate planar lens on the surface of the sample to be tested; Step S4: Transfer the micron lens to the surface of the hybrid substrate planar lens.

5. The method for preparing a super-resolution microlens according to claim 4, characterized in that, Step S3 is as follows: Photoresist and propylene glycol methyl ether acetate (PGMEA) are thoroughly mixed in a 1:1 volume ratio and evenly coated onto the sample surface. Different substrate thicknesses are prepared by setting different spin coat times and rotation speeds.

Images