A method for preparing an elliptical micro-lens array on a hard and brittle material based on femtosecond laser and dry etching and a device thereof

Abstract

The application provides a method for preparing an elliptical micro convex lens array on a hard and brittle material based on a femtosecond laser and a dry etching method and a device thereof, and comprises the following steps: processing a through hole on a substrate surface, processing a micro-nano composite structure on the substrate surface for forming a super-hydrophilic surface; coating PDMS glue on the surface of the hard and brittle material, placing the hard and brittle material coated with the PDMS glue at the bottom of a container with liquid; contacting the super-hydrophilic surface with the surface of the hard and brittle material coated with the PDMS glue, and applying a downward pressure; through the action of surface tension and the downward pressure, the PDMS glue in the rectangular through hole of the substrate forms an elliptical micro convex lens structure; the PDMS is stripped through evaporation to obtain a hard and brittle material with residual PDMS; and the hard and brittle material with residual PDMS is subjected to plasma dry etching to obtain an elliptical micro convex lens array structure on the hard and brittle material. The application can efficiently and flexibly form a high-quality elliptical micro convex lens array on a hard and brittle material.

Description

Technical Field

[0001] This invention relates to the field of optical components, and in particular to a method and apparatus for fabricating elliptical micro-convex lens arrays on hard and brittle materials based on femtosecond laser and dry etching. Background Technology

[0002] Elliptical microlens arrays, as important miniaturized optical components, have significant applications in collimation, astigmatism correction, and beam homogenization of semiconductor lasers due to their different focal lengths along the major and minor axes. Common methods for fabricating elliptical microlenses include photopolymerization, inkjet printing, thermal reflow, photolithography, hot molding, and screen printing. However, these methods are generally limited to processing polymer materials, which are difficult to use in extreme environments such as high temperature and pressure. Hard and brittle materials (such as quartz, sapphire, and optical glass) possess excellent properties such as wear resistance, high temperature resistance, and resistance to thermal cycling, maintaining good performance even under extreme conditions, which better meets the needs of practical applications. However, their brittle and hard characteristics further increase the difficulty of processing. Currently, common industrial methods for processing hard and brittle elliptical microlenses include diamond milling and mask-moving lithography. However, the surface quality of elliptical microlenses processed by diamond milling is not high, and the processing accuracy of mask-moving lithography heavily depends on the movement accuracy of the stepper motor, and its processing flexibility is insufficient. Therefore, the efficient and high-quality fabrication of elliptical microlens arrays remains a significant challenge.

[0003] Femtosecond lasers have proven to be an effective tool for processing arbitrary shapes on any material. Methods for processing elliptical microlenses using femtosecond lasers mainly include femtosecond laser direct writing, femtosecond laser direct writing-assisted annealing, and two-photon polymerization-assisted dry etching. Each method has its limitations. Femtosecond laser direct writing is flexible and can process microstructures of arbitrary shapes, but its surface roughness is relatively poor. Femtosecond laser direct writing-assisted annealing offers high efficiency and high surface precision, but this method has strict requirements on the annealing temperature profile and poor control over the shape of the microstructure. Two-photon polymerization-assisted dry etching offers high processing accuracy and flexibility, but its processing efficiency is low and it is difficult to adapt to large-area array processing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method and apparatus for fabricating an elliptical microlens array on a hard and brittle material using femtosecond laser and dry etching. The method involves directly writing a superhydrophilic surface (due to the immiscibility of PDMS colloid with water, superhydrophilic is equivalent to superhydrophobic PDMS) onto an intrinsically hydrophilic porous (rectangular hole) material plate using a femtosecond laser. Then, pressure is applied underwater to the polydimethylsiloxane (PDMS) coated on the hard and brittle material using this porous superhydrophilic material plate. Under the combined action of surface tension and applied pressure, PDMS forms smooth elliptical microlenses within the rectangular holes of the porous superhydrophilic material plate. The water is then evaporated and the PDMS is solidified. Finally, inductively coupled plasma (ICP) etching is used to dry-etch the sample, transferring the elliptical microlens array shape of the PDMS onto the underlying hard and brittle material. This method offers high processing efficiency, eliminates the need for precise control of the amount of material removed during direct writing, produces high surface quality (the surface morphology is spontaneously formed under the action of surface tension), does not depend on the precision of the motion platform, and can perform large-area processing. It can be applied to a variety of difficult-to-process materials, providing a simple, efficient, flexible, and widely applicable solution for forming high-quality elliptical micro-convex lens arrays on the surface of hard and brittle materials.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A method for fabricating elliptical microlens arrays on hard and brittle materials based on femtosecond laser and dry etching includes the following steps:

[0007] A series of rectangular through holes are arrayed on the surface of the substrate, and a micro-nano composite structure is fabricated on the surface of the substrate by femtosecond laser direct writing scanning, so that the surface of the substrate is formed into a superhydrophilic surface.

[0008] PDMS colloid is coated on the surface of a hard and brittle material, and the hard and brittle material coated with PDMS colloid is placed at the bottom of a container containing liquid;

[0009] The superhydrophilic surface of the substrate is brought into contact with the surface of a hard and brittle material coated with PDMS colloid, and downward pressure is applied. Through the action of surface tension and downward pressure, the PDMS colloid in the rectangular through-hole of the substrate forms an elliptical micro-convex lens structure.

[0010] The PDMS colloid is cured by heating the container; the cured PDMS, substrate and hard and brittle material are taken out of the container, and after evaporation treatment, the PDMS is peeled off to obtain the hard and brittle material with residual PDMS.

[0011] An elliptical microlens array structure on a hard and brittle material with residual PDMS was obtained by inductively coupled plasma dry etching.

[0012] Furthermore, the hard and brittle material includes quartz, sapphire, or optical glass.

[0013] Furthermore, the heating temperature for curing the PDMS colloid in the heating container is 80 degrees Celsius, and the temperature is maintained for 1 hour.

[0014] Furthermore, in the inductively coupled plasma dry etching process, a mixture of sulfur hexafluoride (SF6) and methane (CF3) is selected as the etching gas, with flow rates of 40 sccm and 200 sccm, respectively.

[0015] Furthermore, the vacuum level inside the etching chamber in the inductively coupled plasma dry etching process is less than 200 mTorr, and the power of the upper and lower electrodes is set to 300 W and 50 W, respectively.

[0016] An apparatus for fabricating an elliptical microlens array on a hard and brittle material using femtosecond laser and dry etching includes a femtosecond laser system, an attenuator, a mechanical switch, a beam splitter, a white light source, a CCD, a dichroic mirror, a plano-convex lens, a six-degree-of-freedom translation stage, a computer control system, a liquid container, and an inductively coupled plasma etching system. The femtosecond laser system generates an ultrashort pulse femtosecond laser beam, which passes sequentially through the attenuator, mechanical switch, dichroic mirror, and plano-convex lens before being focused onto the workpiece, which is placed on the six-degree-of-freedom translation stage. The white light source generates white light, which passes through the beam splitter, dichroic mirror, and plano-convex lens before illuminating the processing area of ​​the workpiece, and then returns along the same path to the beam splitter. The reflected light from the beam splitter enters the CCD.

[0017] The liquid container is used to form an elliptical micro-convex lens structure between the surface of the processed part and the hard and brittle material coated with PDMS colloid.

[0018] The inductively coupled plasma etching system is used for inductively coupled plasma dry etching of hard and brittle materials with residual PDMS.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. The method for fabricating elliptical micro-convex lens arrays on hard and brittle materials based on femtosecond laser and dry etching described in this invention has a wide range of applications. It can select any porous intrinsically hydrophilic material as the direct writing object, and can process elliptical micro-convex lens arrays on the surface of any hard and brittle material (such as sapphire, quartz, diamond, etc.), meeting different practical application scenarios and having a wide range of applications.

[0021] 2. The method for fabricating an elliptical micro-convex lens array on a hard and brittle material based on femtosecond laser and dry etching described in this invention allows for quantitative control of the height of the fabricated elliptical micro-convex lenses according to the applied pressure. The major and minor axis dimensions can be freely selected based on the pore shape and size of the intrinsically hydrophilic porous material plate, and the duty cycle can be determined based on the pore duty cycle of the porous material plate. Therefore, the adjustment of the size and distribution of the micro-convex lenses has great flexibility.

[0022] 3. The method for fabricating elliptical micro-convex lens arrays on hard and brittle materials based on femtosecond laser and dry etching described in this invention has no size requirements for the micro-nano composite structures formed by direct writing on porous material plates by femtosecond laser. Therefore, the processing method of this invention has a high fault tolerance rate, making the processing method of this invention simple and efficient.

[0023] 4. The method for fabricating an elliptical micro-convex lens array on a hard and brittle material based on femtosecond laser and dry etching described in this invention utilizes the elliptical micro-convex shape formed by the combined action of the surface tension and pressure of PDMS as a mask. Its surface is very smooth, so the elliptical micro-convex lenses formed after subsequent ICP etching have very high surface quality. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For those skilled in the art, it is obvious that other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the device for fabricating an elliptical micro-convex lens array on a hard and brittle material based on femtosecond laser and dry etching, as described in this invention.

[0026] Figure 2 This is a schematic diagram illustrating the process of fabricating an elliptical micro-convex lens array structure on the PDMS surface using this method.

[0027] Figure 3 This diagram illustrates the process of forming an elliptical microlens array on the surface of a hard and brittle material by etching PDMS using ICP technology.

[0028] Figure 4 This is a schematic diagram of the elliptical micro-convex lens array that was finally processed on a hard and brittle material using this method.

[0029] In the picture:

[0030] 1-Femtosecond laser system, 2-Attenuator, 3-Mechanical switch, 4-Beam splitter, 5-White light source, 6-CCD, 7-Dichroic mirror, 8-Plan-convex lens, 9-Sample, 10-Six-DOF translation stage, 11-Computer control system. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0033] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] The method for fabricating elliptical micro-convex lens arrays on hard and brittle materials based on femtosecond laser and dry etching, as described in this invention, includes the following steps:

[0035] A series of rectangular through holes are arrayed on the surface of the substrate, and a micro-nano composite structure is fabricated on the surface of the substrate by femtosecond laser direct writing scanning, so that the surface of the substrate is formed into a superhydrophilic surface.

[0036] PDMS colloid is coated on the surface of a hard and brittle material, and the hard and brittle material coated with PDMS colloid is placed at the bottom of a container containing liquid;

[0037] The superhydrophilic surface of the substrate is brought into contact with the surface of a hard and brittle material coated with PDMS colloid, and downward pressure is applied. Through the action of surface tension and downward pressure, the PDMS colloid in the rectangular through-hole of the substrate forms an elliptical micro-convex lens structure.

[0038] The PDMS colloid is cured by heating the container; the cured PDMS, substrate and hard and brittle material are taken out of the container, and after evaporation treatment, the PDMS is peeled off to obtain the hard and brittle material with residual PDMS.

[0039] An elliptical microlens array structure on a hard and brittle material with residual PDMS was obtained by inductively coupled plasma dry etching.

[0040] The following example, exemplified by Example 1, illustrates this point:

[0041] In Example 1, the femtosecond laser system 1 generates a Gaussian laser beam with a wavelength of 800 nm, a pulse width of 50 fs, and a repetition rate of 1 kHz for processing.

[0042] S01: A series of rectangular through holes are arrayed on the surface of a stainless steel substrate. These rectangular through holes can be arranged in a circular or rectangular array. (See attached image) Figure 2 As shown in (a), a femtosecond laser beam was used to perform line-by-line direct writing scanning on the surface of an intrinsically hydrophilic rectangular-hole stainless steel plate. The micro-nano composite structure generated by the femtosecond laser direct writing was utilized to form a superhydrophilic surface on the porous stainless steel plate, as shown in the attached figure. Figure 2 As shown in (b); simultaneously, the PDMS colloid obtained by mixing PDMS liquid and curing agent at a ratio of 10:1 was applied to the quartz surface, and then the entire assembly was placed in a water container, as shown in the attached diagram. Figure 2 As shown in (c)-2(d).

[0043] S02: Immerse the porous superhydrophilic stainless steel plate obtained in S01 in water, as shown in the attached diagram. Figure 2 As shown in (e), the laser-treated superhydrophilic surface is brought into contact with PDMS colloid and pressure is applied downwards. Since the stainless steel surface is superhydrophilic, its micro-nano composite structure is quickly filled with water. At the same time, the PDMS colloid is immiscible with water. Therefore, when the stainless steel plate comes into contact with the PDMS colloid and pressure is applied, the PDMS colloid will flow into the rectangular hole of the stainless steel plate. Under the combined action of surface tension and pressure, the PDMS colloid in the rectangular hole will form an elliptical micro-convex lens structure.

[0044] S03: As attached Figure 2 As shown in (f), the sample obtained in SO2, along with a water container, was placed in a muffle furnace and heated to 80°C for 1 hour to allow the PDMS colloid to solidify.

[0045] S04: As attached Figure 2As shown in (g)-2(h), the PDMS cured in SO3, together with the porous stainless steel plate and the quartz sample, was taken out of the water container, and the PDMS was peeled off after the excess moisture was completely evaporated in the air.

[0046] S05: As attached Figure 3 As shown, the PDMS / quartz sample obtained in SO4 was dry etched using ICP technology. A mixture of sulfur hexafluoride (SF6) and methane (CF3) was selected as the etching gas for ICP technology, with flow rates of 40 sccm and 200 sccm, respectively. The vacuum degree in the etching chamber was less than 200 mTorr, and the power of the upper and lower electrodes was set to 300 W and 50 W, respectively. The shape change of the PDMS elliptical microlens was observed in real time during the ICP etching process. After the PDMS was completely removed, the remaining quartz sample was taken out, and the quartz elliptical microlens array structure was obtained.

[0047] like Figure 1 As shown, the apparatus for fabricating an elliptical microlens array on a hard and brittle material based on femtosecond laser and dry etching according to the present invention includes a femtosecond laser system 1, an attenuator 2, a mechanical switch 3, a beam splitter 4, a white light source 5, a CCD 6, a dichroic mirror 7, a plano-convex lens 8, a six-degree-of-freedom translation stage 10, a computer control system 11, a liquid container, and an inductively coupled plasma etching system. The femtosecond laser system 1 is used to generate an ultrashort pulse femtosecond laser beam, which passes sequentially through the attenuator 2, the mechanical switch 3, the dichroic mirror 7, and the plano-convex lens 8 before being injected into the workpiece. 9. The workpiece 9 is placed on a six-degree-of-freedom translation stage 10; the white light source 5 is used to generate white light, which is then irradiated on the processing area of ​​the workpiece 9 after passing through a beam splitter 4, a dichroic mirror 7, and a plano-convex lens 8, and then returns to the beam splitter 4 along the same path, and the reflected light from the beam splitter 4 is injected into the CCD 6; the liquid container is used to form an elliptical micro-convex lens structure between the surface of the processed workpiece 9 and the hard and brittle material coated with PDMS colloid; the inductively coupled plasma etching system is used to perform inductively coupled plasma dry etching on the hard and brittle material with residual PDMS.

[0048] The femtosecond laser system 1 generates a Gaussian laser with a wavelength of 800 nm, a pulse width of 50 fs, and a repetition rate of 1 kHz. The laser energy is changed by the attenuator 2, and the mechanical switch 3 is controlled by the computer system 11. The laser direction is changed by the dichroic mirror 7 so that the laser is perpendicularly incident into the plano-convex lens 8 (f = 250 mm). The femtosecond laser focused by the lens irradiates the surface of the sample 9, which is fixed on the six-degree-of-freedom translation stage 10. During this process, the white light emitted by the white light source 5 passes through the beam splitter 4, the dichroic mirror 7, and the plano-convex lens 8 to irradiate the processing area of ​​the sample 9, and returns along the original path to the beam splitter 4. The beam splitter 4 changes the propagation direction of the returning white light to the CCD 6 to observe the processing status of the sample in real time.

[0049] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0050] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating an elliptical microlens array on a hard and brittle material based on femtosecond laser and dry etching, characterized in that, Includes the following steps: A series of rectangular through holes are arrayed on the surface of the substrate, and a micro-nano composite structure is fabricated on the surface of the substrate by femtosecond laser direct writing scanning, so that the surface of the substrate is formed into a superhydrophilic surface. PDMS colloid is coated on the surface of a hard and brittle material, and the hard and brittle material coated with PDMS colloid is placed at the bottom of a container containing liquid; The superhydrophilic surface of the substrate is brought into contact with the surface of a hard and brittle material coated with PDMS colloid, and downward pressure is applied. Through the action of surface tension and downward pressure, the PDMS colloid in the rectangular through-hole of the substrate forms an elliptical micro-convex lens structure. The PDMS colloid is cured by heating the container; the cured PDMS, substrate and hard and brittle material are taken out of the container, and after evaporation treatment, the PDMS is peeled off to obtain the hard and brittle material with residual PDMS. An elliptical microlens array structure on a hard and brittle material with residual PDMS was obtained by inductively coupled plasma dry etching.

2. The method for fabricating an elliptical micro-convex lens array on a hard and brittle material based on femtosecond laser and dry etching according to claim 1, characterized in that, The hard and brittle material includes quartz, sapphire, or optical glass.

3. The method for fabricating an elliptical micro-convex lens array on a hard and brittle material based on femtosecond laser and dry etching according to claim 1, characterized in that, In inductively coupled plasma dry etching, a mixture of sulfur hexafluoride (SF6) and methane (CH4) is used as the etching gas, with flow rates of 40 sccm and 200 sccm, respectively.

4. The method for fabricating an elliptical micro-convex lens array on a hard and brittle material based on femtosecond laser and dry etching according to claim 3, characterized in that, In inductively coupled plasma dry etching, the vacuum level in the etching chamber is less than 200 mTorr, and the power of the upper and lower electrodes is set to 300 W and 50 W, respectively.

5. An apparatus for fabricating an elliptical microlens array on a hard and brittle material based on femtosecond laser and dry etching according to any one of claims 1-4, characterized in that, The system includes a femtosecond laser system (1), an attenuator (2), a mechanical switch (3), a beam splitter (4), a white light source (5), a CCD (6), a dichroic mirror (7), a plano-convex lens (8), a six-degree-of-freedom translation stage (10), a liquid container, and an inductively coupled plasma etching system. The femtosecond laser system (1) is used to generate an ultrashort pulse femtosecond laser beam. The femtosecond laser beam passes through the attenuator (2), the mechanical switch (3), the dichroic mirror (7), and the plano-convex lens (8) in sequence before entering the workpiece (9). The workpiece (9) is placed on the six-degree-of-freedom translation stage (10). The white light source (5) is used to generate white light. The white light passes through the beam splitter (4), the dichroic mirror (7), and the plano-convex lens (8) before illuminating the processing area of ​​the workpiece (9). The light then returns to the beam splitter (4) along the same path. The reflected light from the beam splitter (4) enters the CCD (6). The liquid container is used to form an elliptical micro-convex lens structure between the surface of the processed part (9) and the hard and brittle material coated with PDMS colloid; The inductively coupled plasma etching system is used for inductively coupled plasma dry etching of hard and brittle materials with residual PDMS.

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