Superlens and femtosecond laser manufacturing real-time monitoring system using it

Abstract

The present invention provides a superlens and a real-time monitoring system for femtosecond laser manufacturing using the superlens. The superlens includes: a substrate and a nanocolumn array on the substrate. Nanocolumns at different positions in the nanocolumn array independently regulate a first wavelength light wave and a second wavelength light wave, so that the first wavelength light wave satisfies a first phase distribution and the second wavelength light wave satisfies a second phase distribution. The superlens can not only focus the first wavelength light wave and the second wavelength light wave on the same plane, but also control the focal depth of the first wavelength light wave to be greater than the focal depth of the second wavelength light wave, so that the superlens meets the requirements of the real-time monitoring system for femtosecond laser manufacturing, and can not only improve the anti-interference ability during the processing, but also improve the accuracy of axial position monitoring.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a superlens and a femtosecond laser manufacturing real-time monitoring system using the superlens. Background Art

[0002] With the continuous advancement of micro-nanofabrication technology, metasurfaces have gradually demonstrated powerful wavefront manipulation capabilities and are expected to become lightweight and thin alternatives to traditional optical components. By designing and optimizing super-atomic structures, metasurfaces can utilize a variety of wavefront manipulation mechanisms to meet the requirements of target light field phase distribution, complex amplitude distribution, polarization state characteristics, frequency modulation, number of channels, and operating bandwidth. Existing metasurfaces are generally only able to flexibly control the phase of the outgoing light. In practical applications, in order to achieve more complex functions, it is necessary to simultaneously manipulate multiple physical quantities of the outgoing light.

[0003] Metalenses are one of the more important applications of metasurfaces. For example, in the field of traditional femtosecond laser manufacturing monitoring, only by focusing on and monitoring the manufacturing parameters of the processing micro-area in real time during the femtosecond laser manufacturing process can the path of the processed surface be accurately predicted and cross-scale processing of the surface microstructure be achieved. However, due to the existence of chromatic aberration, the focus of the processing beam and the monitoring beam will still deviate, so manual focusing is required during the processing process, and the purpose of real-time monitoring cannot be achieved. At the same time, in high-performance laser processing, it is expected that the focused light spot has low sensitivity to axial fluctuations of the sample worktable, and it is expected that the focused light spot has high sensitivity to changes in sample morphology. These two conflicting requirements are difficult to reconcile in existing technologies. Therefore, if the processing accuracy and processing efficiency of femtosecond laser manufacturing are to be improved, it is urgent to develop a metalens that can not only make light of different wavelengths confocal, but also regulate light of each wavelength. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to overcome the above problems by providing a super lens and a femtosecond laser manufacturing real-time monitoring system.

[0005] The present invention provides a superlens, comprising: a substrate and a nanocolumn array on the substrate, wherein the azimuth angles of the nanocolumns in the nanocolumn array are the same so that the polarization of the nanocolumns is independent;

[0006] The nanopillars at different positions in the nanopillar array of the superlens independently regulate the first wavelength light wave and the second wavelength light wave, so that the first wavelength light wave satisfies the first phase distribution and the second wavelength light wave satisfies the second phase distribution; wherein,

[0007] The first phase distribution is expressed as:

[0008]

[0009] Where λ1 is the first wavelength of light, f1 is the focal length corresponding to λ1, Δf1 is the focal depth corresponding to λ1, R is the radius of the superlens, and r is the distance between each nanopillar in the superlens plane and the center of the superlens;

[0010] The second phase distribution is expressed as:

[0011]

[0012] Where λ2 is the second wavelength light wave, f2 is the focal length corresponding to λ2, and (x, y) is the position of each nanopillar on the superlens in the superlens plane;

[0013] Wherein, f1=f2 so that the first wavelength light wave and the second wavelength light wave have a common focal plane after passing through the super lens, and Δf1 is a preset value so that the first wavelength light wave has a preset depth of focus after passing through the super lens. Furthermore, the nanopillars at each position in the nanopillar array of the super lens are selected from a preset superatom response library based on the target phase corresponding to the first wavelength light wave and the second wavelength light wave at the current position and a preset error calculation model, so that the error of the phase control of the first wavelength light wave and the second wavelength light wave by the selected nanopillars satisfies the preset difference constraint condition; wherein,

[0014] The superatom response library is a database of corresponding relationships between the transmission coefficients of different geometric sizes of nanorods and the first wavelength light wave and the second wavelength light wave respectively;

[0015] The error calculation model is expressed as the following calculation formula:

[0016]

[0017] Where, is the error of the nanorod in controlling the phase of the first wavelength light wave and the second wavelength light wave, t lr_λ1 is the transmission coefficient of the circular polarization conversion ability of nanorods of different sizes under the first wavelength light wave, is the target phase of the first wavelength light wave at the current position, t lr_λ2 is the transmission coefficient of the circular polarization conversion ability of nanorods of different sizes under the second wavelength light wave, is the target phase of the second wavelength light wave at the current position, and abs represents the absolute value.

[0018] Furthermore, the azimuth angle of each nanopillar in the nanopillar array is 0°.

[0019] Furthermore, the substrate is quartz, and the nanorods are amorphous silicon nanorods.

[0020] Furthermore, the geometric dimensions of the nanocolumns include period, height, major axis length and minor axis length, and the period and height are fixed. By changing the major axis length and minor axis length of the nanocolumns, the transmission coefficients corresponding to different geometric dimensions of the nanocolumns are obtained by simulation based on the rigorous coupled wave method.

[0021] Furthermore, the nanocolumns have a period of 450 nm, a height of 600 nm, a major axis length between 60 nm and 350 nm, and a minor axis length between 60 nm and 350 nm.

[0022] On the other hand, the present invention also provides a femtosecond laser manufacturing real-time monitoring system using the metalens described in the above items, the system comprising: a femtosecond laser processing optical path system and a pupil differential confocal axial monitoring optical path system, the femtosecond laser processing optical path system using a first wavelength light wave to process the sample surface; the pupil differential confocal axial monitoring optical path system using a second wavelength light wave to monitor the axial position of the sample surface; wherein the femtosecond laser processing optical path system and the pupil differential confocal axial monitoring optical path system jointly use the metalens to focus on the sample surface, and the first wavelength light wave has a long focal depth, and the second wavelength light wave has a short focal depth.

[0023] Furthermore, the femtosecond laser processing optical path system includes a femtosecond laser, a space-time shaping module, a two-dimensional scanner and the super lens arranged in sequence along the optical path of the first wavelength light wave, the femtosecond laser incidents the first wavelength light wave into the space-time shaping module, the space-time shaping module shapes the first wavelength light wave in time and space, and incidents the shaped first wavelength light wave into the two-dimensional scanner, the two-dimensional scanner controls the first wavelength light wave to scan the sample surface according to the pattern to be processed, so that the first wavelength light wave emitted by the two-dimensional scanner is focused on the sample surface through the super lens to perform femtosecond laser processing on the sample surface.

[0024] Furthermore, the pupil differential confocal axial monitoring optical path system includes a continuous laser, a first light source collimation module, a first beam splitter, a first dichroic mirror, a second beam splitter and the metalens, which are sequentially arranged along the incident optical path of the second wavelength light wave, and a pupil differential confocal detection module arranged in the reflected optical path of the second wavelength light wave; wherein,

[0025] The laser transmits the second wavelength light wave to the first light source collimation module to form a parallel light beam. The second wavelength light wave emitted by the first light source collimation module is refracted by the first beam splitter and then incident on the first dichroic mirror. The first dichroic mirror reflects the second wavelength light wave to the second beam splitter. The second beam splitter reflects the second wavelength light wave in a direction perpendicular to the sample surface. The second wavelength light wave reflected by the second beam splitter is focused on the sample surface after passing through the super lens. The second wavelength light wave reflected by the sample surface is reflected by the second beam splitter to the first dichroic mirror. The first dichroic mirror reflects the reflected second wavelength light wave to the first beam splitter. The first beam splitter refracts the reflected second wavelength light wave to the pupil differential confocal detection module. The pupil differential confocal detection module obtains a pupil differential confocal response curve, and the axial position of the sample surface is obtained according to the pupil differential confocal response curve.

[0026] Furthermore, the system also includes a Raman spectrum detection module and a microscopic imaging optical path system, wherein:

[0027] The Raman spectrum detection module includes the super lens, a second beam splitter, a first dichroic mirror, a first focusing module and a spectrometer arranged on the optical path of the Rayleigh light reflected from the sample surface.

[0028] The Rayleigh light reflected from the sample surface passes through the metalens, the second beam splitter, and the first dichroic mirror in sequence. The first dichroic mirror refracts the Rayleigh light reflected from the sample surface into the first focusing module. The first focusing module converges the Rayleigh light reflected from the sample surface onto the spectrometer. The spectrometer analyzes and obtains Raman spectrum information of the sample surface, thereby forming a Raman spectrum detection module to monitor the performance parameters of the sample surface.

[0029] The microscopic imaging optical path system includes a white light source, a third beam splitter, a fourth beam splitter, and a second focusing module and a CCD module arranged in sequence along the incident optical path of a preset third wavelength light wave. The white light source emits a third wavelength light wave, which is incident on the third beam splitter. The third beam splitter refracts the third wavelength light wave into the fourth beam splitter. The fourth beam splitter reflects the third wavelength light wave in a direction perpendicular to the sample surface and focuses it on the sample surface through the second beam splitter and the super lens. The third wavelength light wave reflected from the sample surface is refracted into the fourth beam splitter through the super lens and the second beam splitter. The fourth beam splitter reflects the reflected third wavelength light wave into the third beam splitter. The third beam splitter reflects the reflected third wavelength light wave into the second focusing module. The second focusing module converges the reflected third wavelength light wave onto the CCD module, and the CCD module determines the tilt and position of the sample.

[0030] The present invention provides a superlens and a real-time monitoring system for femtosecond laser manufacturing using the superlens. By encoding and arranging each nanopillar in a nanopillar array, nanopillars at different positions in the nanopillar array independently regulate a first wavelength light wave and a second wavelength light wave, so that the first wavelength light wave satisfies a first phase distribution and the second wavelength light wave satisfies a second phase distribution. The superlens can not only focus the first wavelength light wave and the second wavelength light wave on the same plane, but also control the focal depth of the first wavelength light wave to be greater than the focal depth of the second wavelength light wave, so that the superlens meets the requirements of the real-time monitoring system for femtosecond laser manufacturing, and can not only improve the anti-interference ability during the processing, but also improve the accuracy of axial position monitoring.

[0031] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiment below. The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention. In the accompanying drawings:

[0033] Figure 1 This is a schematic diagram of the optical path of a femtosecond laser manufacturing real-time monitoring system according to an embodiment of the present invention;

[0034] Figure 2 A detailed optical path diagram of the metalens in the system according to an embodiment of the present invention;

[0035] Figure 3 is the FDTD simulation intensity distribution of the xz cross section of the designed superlens under the incident polarization condition of the embodiment of the present invention, where:

[0036] (a) FDTD simulation intensity distribution when λ1 = 780 nm;

[0037] (b) FDTD simulation intensity distribution when λ2 = 633 nm;

[0038] Figure 4 FDTD simulation results of the long-short focal depth confocal focusing of the processing beam and the monitoring beam according to the embodiment of the present invention, wherein:

[0039] (c) FDTD simulation intensity distribution at long focal depth when λ1 = 780 nm;

[0040] (d) FDTD simulation intensity distribution at short focal depth when λ2 = 633 nm;

[0041] Figure 5 This is an optical path diagram of a femtosecond laser processing optical path system according to an embodiment of the present invention;

[0042] Figure 6 is a light path diagram of a monitoring system according to an embodiment of the present invention;

[0043] Figure 7 1 is a pupil differential confocal response curve of an embodiment of the present invention. DETAILED DESCRIPTION

[0044] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0045] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art in the art to which the present invention pertains. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with those in the context of the prior art and, unless specifically defined, will not be interpreted in an idealized or overly formal sense.

[0046] Reference Figure 1 The real-time monitoring system provided by an embodiment of the present invention includes a femtosecond laser processing optical system 1 and a pupil-splitting differential confocal axial monitoring optical system 2. The femtosecond laser processing optical system 1 uses a first wavelength of light to process the sample surface, while the pupil-splitting differential confocal axial monitoring optical system 2 uses a second wavelength of light to monitor the axial position of the sample surface. The femtosecond laser processing optical system 1 and the pupil-splitting differential confocal axial monitoring optical system 2 both use a superlens 5 to focus on the sample surface. The surface of the superlens 5 is composed of an array of nanorods 22 of different sizes and the same azimuth angle, so that the first wavelength and the second wavelength are focused on the same plane, and the first wavelength has a long focal depth, while the second wavelength has a short focal depth.

[0047] Among them, ensuring that the first wavelength light wave and the second wavelength light wave are focused on the same plane can realize real-time monitoring during the processing, making the first wavelength light wave have a long focal depth can avoid processing errors caused by slight disturbances of the platform, and making the second wavelength light wave have a short focal depth can improve the sensitivity of axial detection.

[0048] In a specific embodiment of the present invention, the first wavelength lightwave is the processing beam, specifically 780 nm, and the second wavelength lightwave is the monitoring beam, specifically 633 nm. The metalens 5 provided in this embodiment of the present invention focuses the first and second wavelength lightwaves on the same plane, enabling real-time axial position monitoring during femtosecond laser processing. The metalens 5 also improves the anti-interference capability of the processing process by increasing the focal depth of the first wavelength lightwave and reducing the focal depth of the second wavelength lightwave, thereby improving the accuracy of axial position monitoring.

[0049] Reference Figure 2-Figure 4 In order to meet the needs of femtosecond laser manufacturing and monitoring, the embodiment of the present invention designs a dual-wavelength, polarization-independent superlens 5 for the two working wavelengths of the processing beam (λ1: 780nm) and the monitoring beam (λ2: 633nm), in order to focus the processing beam and the monitoring beam on the same focal plane. The superlens 5 designed by the present invention is composed of Figure 2 The amorphous silicon nanorod arrays of different sizes and the same azimuth angle are shown. The designed super lens 5 is used to independently control the wavefronts of the processing beam and the monitoring beam.

[0050] Furthermore, each nanorod 22 of the metasurface provided by the embodiment of the present invention satisfies the following condition: when circularly polarized light is incident on a nanorod 22 with an azimuth angle of θ, the Jones vector of the outgoing light can be expressed as:

[0051]

[0052] Among them, the transmission coefficient t ij In the equation, the first subscript is the outgoing polarization state, and the second subscript is the incident polarization state. x and E y These are the polarization states of the outgoing light in the x and y directions, respectively.

[0053] The first term in the formula is the non-polarization conversion term, which can be reduced by optimizing the geometric dimensions of each unit nanorod 22 (making the nanorod 22 approximately regarded as a local half-wave plate). ±i2θ This is the phase modulation term caused by the polarization conversion process and can be explained accordingly by the geometric phase principle. When left-handed / right-handed circularly polarized light is incident on a nanopillar 22 with an azimuth angle θ = 0° / 90°, the phase modulation generated by the reverse polarization channel is the same. However, any polarization state can always be decomposed into a superposition of left-handed and right-handed circularly polarized components with different amplitude ratios. Therefore, by fixing the azimuth angle of each unit nanopillar 22 to 0° and adjusting the geometric dimensions of the anisotropic nanopillar 22 according to the desired phase distribution, the desired wavefront control function can be achieved under polarization-independent conditions.

[0054] Furthermore, in order to satisfy that the first wavelength light wave and the second wavelength light wave are focused on the same plane, and the focal depth of the first wavelength light wave is greater than the focal depth of the second wavelength, the nanopillars 22 at different positions in the nanopillar array 22 of the superlens 5 independently regulate the first wavelength light wave and the second wavelength light wave, so that the first wavelength light wave satisfies the first phase distribution and the second wavelength light wave satisfies the second phase distribution; wherein,

[0055] The first phase distribution is expressed as:

[0056]

[0057] Where λ1 is the first wavelength of light, f1 is the focal length corresponding to λ1, Δf1 is the focal depth corresponding to λ1, R is the radius of the superlens, and r is the distance between each nanopillar in the superlens plane and the center of the superlens;

[0058] The second phase distribution is expressed as:

[0059]

[0060] Where λ2 is the second wavelength light wave, f2 is the focal length corresponding to λ2, and (x, y) is the position of each nanopillar on the superlens in the superlens plane;

[0061] Here, f1=f2 so that the first wavelength light wave and the second wavelength light wave have a common focal plane after passing through the super lens, and Δf1 is a preset value so that the first wavelength light wave has a preset depth of focus after passing through the super lens.

[0062] Furthermore, the nanopillars 22 at each position in the array of nanopillars 22 of the superlens 5 are selected from a preset superatom response library based on the target phases corresponding to the first wavelength lightwave and the second wavelength lightwave at the current position and a preset error calculation model, so that the errors of the phase control of the first wavelength lightwave and the second wavelength lightwave by the selected nanopillars meet the preset difference constraint conditions; wherein, the superatom response library is a database of the correspondence between the transmission coefficients corresponding to the first wavelength lightwave and the second wavelength lightwave of different geometric sizes of the nanopillars 22, respectively, constructed based on the rigorous coupled wave method.

[0063] The error calculation model is expressed as the following calculation formula:

[0064]

[0065] Where ε is the error of the phase control of the first wavelength light wave and the second wavelength light wave by the nanorod 22, t lr_λ1 is the transmission coefficient of the circular polarization conversion capability of nanorods 22 of different sizes under the first wavelength light wave, is the target phase of the first wavelength light wave at the current position, tlr_λ2 is the transmission coefficient of the circular polarization conversion ability of nanorods of different sizes under the second wavelength light wave, is the target phase of the second wavelength light wave at the current position, and abs represents the absolute value.

[0066] The transmission coefficient of circular polarization conversion capability can be expressed by the transmission coefficient under the linear polarization basis vector as follows:

[0067]

[0068] Where i = 1 or 2, t xx is the transmission coefficient of linearly polarized light when both the outgoing polarization state and the incident polarization state are in the x direction, t yy is the transmission coefficient of linearly polarized light in the y direction when both the outgoing polarization state and the incident polarization state are in the y direction, t xy is the transmission coefficient of linearly polarized light with the outgoing polarization state in the x direction and the incident polarization state in the y direction, t yx is the transmission coefficient of linearly polarized light with the outgoing polarization state in the y direction and the incident polarization state in the x direction.

[0069] In the specific embodiment of the present invention, since the azimuth angle of each nanorod 22 is 0°, t xy and t yx The values ​​of are all zero.

[0070] Furthermore, the meta-atom response library is obtained through simulation using the rigorous coupled wave method. In this embodiment of the present invention, the geometric dimensions of the nanopillars 22 include a period P, a height H, a major axis length L, and a minor axis length W. The period P and height H are fixed. By varying the major axis L and minor axis W of the nanopillars, the amplitude and phase of the transmission coefficient corresponding to different nanopillar geometric dimensions are simulated using the rigorous coupled wave method.

[0071] In a specific embodiment of the present invention, the wavelengths of the incident light are set to λ in =633nm and 780nm, with the height H and period P of the nanopillars 22 fixed, where the period P is set to 450nm and the height H is set to 600nm, a two-dimensional parametric sweep of the major axis L and minor axis W of the nanopillars 22 is performed using the rigorous coupled wave analysis (RCWA) method (L: 60nm~350nm, W: 60nm~350nm). The transmission coefficient t corresponding to nanopillars 22 of different sizes is obtained by simulation. lr Amplitude and phase.

[0072] In a specific embodiment of the present invention, a dual-wavelength, polarization-independent superlens 5 (NA>0.7) with an aperture of 36 μm and a focal length of 18 μm is designed according to the above-mentioned superlens 5 design method. The processing beam (780 nm) and the monitoring beam (633 nm) can be focused on the same focal plane. The finite difference time domain (FDTD) method is used to perform full-wave simulation on the designed superlens 5, and the working wavelengths are set to 633 nm and 780 nm respectively, and the incident polarization state is set to x-direction linear polarization light, y-direction linear polarization light, 45° linear polarization light, 135° linear polarization light, left-handed and right-handed circularly polarized light, and the following is obtained. Figure 3 The intensity distribution of the xz cross section under different incident conditions is shown. In the simulation, when the incident light wavelengths are 633nm and 780nm, the corresponding average focal lengths for the six polarization states are 18.083μm and 18.106μm, respectively. The FDTD simulation results show that the proposed method can focus the processing beam and the monitoring beam of two different wavelengths onto the same focal plane.

[0073] Furthermore, lenses with long focal depths have crucial applications in fields such as tomography, lithography, and information processing. To achieve this long focal depth, a continuously varying phase distribution, either radially or angularly modulated, must be encoded within the optical element. To achieve a long focal depth for the processing beam and a short focal depth for the monitoring beam, this project employed the design approach of Axilenses.

[0074] The metalens 5 of the embodiment of the present invention independently regulates the first wavelength light wave and the second wavelength light wave, wherein the focal depth required for the first wavelength light wave is Δf1, and the calculated and By encoding them simultaneously in the same metalens 5, the long-short focal depth confocal focusing function of the dual-wavelength, polarization-independent metalens 5 can be realized for the processing beam and the monitoring beam. Based on the above-mentioned long-short focal depth confocal focusing design method of the dual-wavelength, polarization-independent metalens 5, a metalens 5 with an aperture of 36μm (due to the size of computer memory, the simulation aperture of the metalens 5 is set to 36μm) is designed. Among them, the 633nm monitoring beam has a short focal depth f2 = 18μm, the processing beam has a long focal depth f1 = 18μm, and Δf1 = 6μm. Figure 4 The FDTD simulation results shown can effectively demonstrate that the proposed method can independently control the processing beam and the monitoring beam to achieve long-short focal depth confocal plane focusing.

[0075] When designing metasurfaces to realize lens focusing and holographic imaging, considering factors such as computer memory and simulation time, smaller metasurfaces (<100×100μm) are usually designed. 2) and used simulation software to verify the feasibility of the design method. When actually fabricated, large-scale computer simulations were then used to design the required larger metasurface. In this project, the metalens 5 is expected to have an aperture of 2.5 mm and an NA > 0.7. These simulation results fully demonstrate the feasibility of the long-short focal depth confocal focusing design method for the dual-wavelength, polarization-independent metalens 5.

[0076] The metalens 5 provided in the embodiment of the present invention can not only focus the first wavelength lightwave and the second wavelength lightwave on the same plane, but also adjust the focal depth of the first wavelength lightwave and the focal depth of the second wavelength lightwave, and make the metalens 5 polarization-independent. The metalens can not only focus the first wavelength lightwave and the second wavelength lightwave on the same plane, but also control the focal depth of the first wavelength lightwave to be greater than the focal depth of the second wavelength lightwave, so that it meets the requirements of the real-time monitoring system of femtosecond laser manufacturing, not only improving the anti-interference ability during the processing, but also improving the accuracy of axial position monitoring.

[0077] Specifically, Figure 1 This is a schematic diagram of the optical path of the real-time monitoring system for femtosecond laser manufacturing parameters according to an embodiment of the present invention. Figure 5 The femtosecond laser processing optical path system 1 of the embodiment of the present invention is composed of Figure 1 and Figure 2 It can be seen that the femtosecond laser processing optical path system 1 and the spectral pupil differential confocal axial monitoring optical path system 2, the femtosecond laser processing optical path system 1 uses a first wavelength light wave to process the sample surface; the spectral pupil differential confocal axial monitoring optical path system 2 uses a second wavelength light wave to monitor the axial position of the sample surface; wherein, the femtosecond laser processing optical path system 1 and the spectral pupil differential confocal axial monitoring optical path system 2 jointly use the super lens 5 to focus on the sample surface, and the first wavelength light wave has a long focal depth, and the second wavelength light wave has a short focal depth.

[0078] Furthermore, the femtosecond laser processing optical path system 1 provided in an embodiment of the present invention includes a femtosecond laser 11, a spatiotemporal shaping module, a two-dimensional scanner 13, and the metalens 5, which are sequentially arranged along the optical path of a first wavelength light wave. The femtosecond laser 11 is used to incident the first wavelength light wave into the spatiotemporal shaping module (spatiotemporal shaping module 12), which performs temporal and spatial shaping on the first wavelength light wave and then incidents the shaped first wavelength light wave into the two-dimensional scanner 13. The two-dimensional scanner 13 controls the first wavelength light wave according to the pattern to be processed and scans the sample surface, so that the first wavelength light wave emitted by the two-dimensional scanner 14 is focused on the sample surface through the metalens 5 to perform femtosecond laser processing on the sample surface. In addition, the femtosecond laser processing optical path system 1 may further include an optical path adjustment module 14 composed of a diverging lens and a collimating lens to facilitate expanding the beam range of the first wavelength light wave.

[0079] It should be noted here that other optical lenses are also provided in the optical path of the femtosecond laser processing optical path system 1. The function of the other optical lenses is to converge light from different directions onto the same path and convert them into light perpendicular to the sample surface. Since the other optical lenses do not change the transmission path of the first wavelength light wave, they will not be repeated here.

[0080] Furthermore, if Figure 6 As shown, the pupil differential confocal axial monitoring optical path system 2 includes a continuous laser 21, a first light source collimation module 22, a first beam splitter 23, a first dichroic mirror 42, a second beam splitter 41 and the super lens 5, which are arranged in sequence along the incident optical path of the second wavelength light wave, and a pupil differential confocal detection module arranged in the reflected optical path of the second wavelength light wave.

[0081] The pupil-splitting differential confocal axial monitoring optical path system 2 uses a continuous laser 21 to input the second wavelength light wave into the first light source collimating module 22 to form a parallel light beam, wherein the first light source collimating module can also be a collimating lens to radially expand the continuous laser and convert it into a parallel light beam.

[0082] The second wavelength light wave emitted by the first light source collimating module 22 is refracted by the first beam splitter 22 and then incident on the first dichroic mirror 42. The first dichroic mirror 42 reflects the second wavelength light wave to the second beam splitter 41. The second beam splitter 41 reflects the second wavelength light wave in a direction perpendicular to the sample surface. The second wavelength light wave reflected by the second beam splitter 41 is focused on the sample surface after passing through the super lens 5. The second wavelength light wave reflected by the sample surface is reflected by the second beam splitter 41 to the first dichroic mirror 42. The first dichroic mirror 42 reflects the reflected second wavelength light wave to the first beam splitter 22. The first beam splitter 22 refracts the reflected second wavelength light wave to the pupil differential confocal detection module. The pupil differential confocal detection module obtains a pupil differential confocal response curve, and the axial position of the sample surface is obtained according to the pupil differential confocal response curve.

[0083] Furthermore, the pupil-splitting differential confocal detection module includes a relay lens 24, a D-type aperture 25, and a pinhole two-quadrant detector 26, arranged sequentially along the optical path. The D-type aperture 25 can block half of the light beam. The pinhole two-quadrant detector 26 is a pair of point detectors symmetrical about the optical axis. This produces a bipolar, highly sensitive, and highly linear axial response curve that is linearly correlated with the height variation of the device under test, enabling height measurement of the processed component. Combined with the high-speed lateral beam scanning method of the galvanometer, the lateral dimensions of the processed component can be measured.

[0084] like Figure 7 As shown, the pupil-splitting differential confocal light intensity response curve can be obtained according to the pinhole two-quadrant detector 26. When the sample to be measured is located at the front focus position u0, the measured front focus light intensity signal I AWhen the sample under test is at the back focus position u2, the measured back focus light intensity signal I B The two signals are differentially subtracted to obtain the pupil differential confocal signal I diff When the sample is at the focal position u1, the pupil differential confocal signal I diff The pupil-differential confocal signal exhibits excellent linearity near the zero point, with a large slope and bipolarity in the fitted line. For thin samples whose height variation is within the linear region, the height profile of the device under test can be obtained without axial scanning. For large-scale devices, axial scanning can be performed at larger axial intervals, reducing the number of scanning layers.

[0085] Furthermore, the real-time monitoring system provided by the embodiment of the present invention also includes a Raman spectrum detection module 4, which includes the super lens 5, the second beam splitter 41, the first dichroic mirror 42, the first focusing module 44 and the spectrometer 45 arranged on the optical path of the Rayleigh light reflected from the sample surface. The Rayleigh light reflected from the sample surface is reflected to the first dichroic mirror 42 through the second beam splitter 41. The first dichroic mirror 42 refracts the Rayleigh light reflected from the sample surface into the first focusing module 44. The first focusing module 44 converges the Rayleigh light reflected from the sample surface onto the spectrometer 45. The spectrometer 45 analyzes and obtains Raman spectrum information of the sample surface to monitor the performance parameters of the sample surface.

[0086] Furthermore, the real-time monitoring system provided by the embodiment of the present invention also includes a microscopic imaging optical path system 3, which includes a white light source 31, a third spectroscope 32, a fourth spectroscope 33, which are sequentially arranged along the incident optical path of the preset third wavelength light wave, and a second focusing module 34 and a CCD module 35 which are arranged on the reflection optical path of the third wavelength light wave. The white light source 31 emits a third wavelength light wave, and the third wavelength light wave is incident on the third spectroscope 32. The third spectroscope 32 refracts the third wavelength light wave into the fourth spectroscope 33, and the fourth spectroscope 33 reflects the third wavelength light wave. The long light wave is reflected in a direction perpendicular to the sample surface and is focused on the sample surface through the second beam splitter 41 and the super lens 5. The third wavelength light wave reflected from the sample surface is refracted into the fourth beam splitter 33 through the super lens 5 and the second beam splitter 41. The fourth beam splitter 33 reflects the reflected third wavelength light wave into the third beam splitter 31. The third beam splitter 31 reflects the reflected third wavelength light wave into the second focusing module 34. The second focusing module 34 converges the reflected third wavelength light wave onto the CCD module 35, which determines the tilt and position of the sample.

[0087] The Raman spectroscopy detection module 4 provided in the embodiment of the present invention simultaneously monitors the sample morphology and performance parameters. The morphological parameters of the sample are monitored using the post-pupil laser differential confocal system 2 and the microscopic imaging system 3. Taking advantage of the wide applicability and rich measurement information of Raman spectroscopy, the Rayleigh light and reflected light reflected by the sample are collected through the superlens 5 and coupled into the spectrometer. By analyzing the detected spectral data, performance parameters such as sample composition, stress, and temperature are monitored in real time. This lays the foundation for the integration of the monitoring system with the processing system in the later stage of the project to achieve real-time monitoring of the morphology and performance of the processing area.

[0088] The present invention provides a real-time monitoring system for femtosecond laser manufacturing parameters based on superlens confocal focusing. The superlens 5 is used to focus a first wavelength light wave used for femtosecond processing and a second wavelength light wave used for axial monitoring on the same plane, and the first wavelength light wave has a long focal depth and the second wavelength light wave has a short focal depth, so that the femtosecond laser processing process can achieve real-time axial position monitoring. By increasing the focal depth of the first wavelength light wave, the anti-interference ability of the processing process is improved, and by reducing the focal depth of the second wavelength light wave, the accuracy of axial position monitoring is improved.

[0089] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of the present invention and to form different embodiments. For example, any of the claimed embodiments may be used in any combination.

[0090] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A metalens, characterized in that The metalens comprises: a substrate and a nanocolumn array on the substrate, wherein the azimuth angles of the nanocolumns in the nanocolumn array are the same so that the polarization of the nanocolumns is independent; The nanopillars at different positions in the nanopillar array of the superlens independently regulate the first wavelength light wave and the second wavelength light wave, so that the first wavelength light wave satisfies the first phase distribution and the second wavelength light wave satisfies the second phase distribution; wherein, The first phase distribution is expressed as: Where λ1 is the first wavelength of light, f1 is the focal length corresponding to λ1, Δf1 is the focal depth corresponding to λ1, R is the radius of the superlens, and r is the distance between each nanopillar in the superlens plane and the center of the superlens; The second phase distribution is expressed as: Where λ2 is the second wavelength light wave, f2 is the focal length corresponding to λ2, and (x, y) is the position of each nanopillar on the superlens in the superlens plane; Here, f1=f2 so that the first wavelength light wave and the second wavelength light wave have a common focal plane after passing through the super lens, and Δf1 is a preset value so that the first wavelength light wave has a preset depth of focus after passing through the super lens.

2. The metalens according to claim 1, wherein The nanopillars at each position in the nanopillar array of the metalens are selected from a preset meta-atom response library according to the target phases corresponding to the first wavelength light wave and the second wavelength light wave at the current position and a preset error calculation model, so that the errors of the phase control of the first wavelength light wave and the second wavelength light wave by the selected nanopillars meet the preset difference constraint conditions; wherein, The superatom response library is a database of corresponding relationships between the transmission coefficients of different geometric sizes of nanorods and the first wavelength light wave and the second wavelength light wave respectively; The error calculation model is expressed as the following calculation formula: Where ε is the error of the nanorod in controlling the phase of the first wavelength light wave and the second wavelength light wave, t lr_λ1 is the transmission coefficient of the circular polarization conversion ability of nanorods of different sizes under the first wavelength light wave, is the target phase of the first wavelength light wave at the current position, t lr_λ2 is the transmission coefficient of the circular polarization conversion ability of nanorods of different sizes under the second wavelength light wave, is the target phase of the second wavelength light wave at the current position, and abs represents the absolute value.

3. The metalens according to claim 2, wherein The azimuth angle of each nanopillar in the nanopillar array is 0°.

4. The metalens according to claim 3, wherein The substrate is quartz, and the nanorods are amorphous silicon nanorods.

5. The metalens according to claim 2, wherein The geometric dimensions of the nanocolumns include period, height, major axis length and minor axis length. The period and height are fixed. By changing the major axis length and minor axis length of the nanocolumns, the transmission coefficients corresponding to different geometric dimensions of the nanocolumns are obtained by simulation based on the rigorous coupled wave method.

6. The metalens according to claim 5, wherein The nanocolumns have a period of 450 nm, a height of 600 nm, a major axis length between 60 nm and 350 nm, and a minor axis length between 60 nm and 350 nm.

7. A femtosecond laser manufacturing real-time monitoring system using the metalens according to any one of claims 1 to 6, characterized in that: The system includes: a femtosecond laser processing optical path system and a pupil-splitting differential confocal axial monitoring optical path system, wherein the femtosecond laser processing optical path system uses a first wavelength light wave to process the sample surface; the pupil-splitting differential confocal axial monitoring optical path system uses a second wavelength light wave to monitor the axial position of the sample surface; wherein the femtosecond laser processing optical path system and the pupil-splitting differential confocal axial monitoring optical path system jointly use the metalens to focus on the sample surface, and the first wavelength light wave has a long focal depth, and the second wavelength light wave has a short focal depth.

8. The system according to claim 7, characterized in that The femtosecond laser processing optical path system includes a femtosecond laser, a space-time shaping module, a two-dimensional scanner and the super lens which are sequentially arranged along the optical path of the first wavelength light wave. The femtosecond laser inputs the first wavelength light wave into the space-time shaping module. The space-time shaping module performs temporal and spatial shaping on the first wavelength light wave and inputs the shaped first wavelength light wave into the two-dimensional scanner. The two-dimensional scanner controls the first wavelength light wave to scan the sample surface according to the pattern to be processed, so that the first wavelength light wave emitted by the two-dimensional scanner is focused on the sample surface through the super lens to perform femtosecond laser processing on the sample surface.

9. The system according to claim 8, characterized in that The pupil differential confocal axial monitoring optical path system comprises a continuous laser, a first light source collimating module, a first beam splitter, a first dichroic mirror, a second beam splitter and the metalens, which are sequentially arranged along the incident optical path of the second wavelength light wave, and a pupil differential confocal detection module arranged in the reflected optical path of the second wavelength light wave; wherein, The laser transmits the second wavelength light wave to the first light source collimation module to form a parallel light beam. The second wavelength light wave emitted by the first light source collimation module is refracted by the first beam splitter and then incident on the first dichroic mirror. The first dichroic mirror reflects the second wavelength light wave to the second beam splitter. The second beam splitter reflects the second wavelength light wave in a direction perpendicular to the sample surface. The second wavelength light wave reflected by the second beam splitter is focused on the sample surface after passing through the super lens. The second wavelength light wave reflected by the sample surface is reflected by the second beam splitter to the first dichroic mirror. The first dichroic mirror reflects the reflected second wavelength light wave to the first beam splitter. The first beam splitter refracts the reflected second wavelength light wave to the pupil differential confocal detection module. The pupil differential confocal detection module obtains a pupil differential confocal response curve, and the axial position of the sample surface is obtained according to the pupil differential confocal response curve.

10. The system according to claim 9, characterized in that The system also includes a Raman spectrum detection module and a microscopic imaging optical path system, wherein: The Raman spectrum detection module includes the super lens, a second beam splitter, a first dichroic mirror, a first focusing module and a spectrometer arranged on the optical path of the Rayleigh light reflected from the sample surface. The Rayleigh light reflected from the sample surface passes through the metalens, the second beam splitter, and the first dichroic mirror in sequence. The first dichroic mirror refracts the Rayleigh light reflected from the sample surface into the first focusing module. The first focusing module converges the Rayleigh light reflected from the sample surface onto the spectrometer. The spectrometer analyzes and obtains Raman spectrum information of the sample surface, thereby forming a Raman spectrum detection module to monitor the performance parameters of the sample surface. The microscopic imaging optical path system includes a white light source, a third beam splitter, a fourth beam splitter, and a second focusing module and a CCD module arranged in sequence along the incident optical path of a preset third wavelength light wave. The white light source emits a third wavelength light wave, which is incident on the third beam splitter. The third beam splitter refracts the third wavelength light wave into the fourth beam splitter. The fourth beam splitter reflects the third wavelength light wave in a direction perpendicular to the sample surface and focuses it on the sample surface through the second beam splitter and the super lens. The third wavelength light wave reflected from the sample surface is refracted into the fourth beam splitter through the super lens and the second beam splitter. The fourth beam splitter reflects the reflected third wavelength light wave into the third beam splitter. The third beam splitter reflects the reflected third wavelength light wave into the second focusing module. The second focusing module converges the reflected third wavelength light wave onto the CCD module, and the CCD module determines the tilt and position of the sample.

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