Transparent medium internal color pixel array single pulse stereoscopic writing method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2024-03-04
- Publication Date
- 2026-07-21
Smart Images
Figure CN118060751B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for writing color pixels in a transparent medium in the field of ultrafast laser micro-nano fabrication technology, and particularly to a method for writing color pixel arrays in a transparent medium using a single pulse. Background Technology
[0002] With the rapid development of technologies such as artificial intelligence, the total amount of data generated by humans is exploding, and traditional storage technologies can no longer meet the long-term preservation needs of massive amounts of data. In recent years, ultra-high-density permanent data storage technology using all-inorganic transparent dielectrics as carriers has attracted widespread attention. However, due to the inherent high damage threshold and low linear light absorption rate of inorganic transparent dielectrics, it is difficult to efficiently generate micro-nano photonic structures with multi-dimensional information loading capabilities within them using traditional photolithography processes.
[0003] Ultrafast lasers possess extremely high peak power, capable of exciting nonlinear light absorption in materials, thereby inducing spatially selective material modification within transparent media. Research indicates that a single low-energy ultrafast laser pulse can excite intra-pulse coupling effects within lithium niobate crystals, inducing micrometer-scale localized amorphization phase transitions, thus embedding amorphous pixels within the crystal matrix. Due to the distinctly different optical properties of crystalline and amorphous materials, pixel-level interference structural colors can be generated using color polarization effects. By reusing the color and intensity of amorphous pixels, multidimensional optical information integration can be achieved for ultra-high-density data storage. However, current amorphous pixel generation relies on point-by-point processing, requiring frequent adjustments to process parameters and processing positions to generate different color pixels in three-dimensional space. This one-to-one point-by-point processing method limits data writing speed; therefore, there is an urgent need to develop one-to-many three-dimensional processing strategies to improve the efficiency of multidimensional optical data writing. Summary of the Invention
[0004] To achieve high-speed batch writing of multidimensional optical data inside inorganic transparent media, this invention proposes a three-dimensional writing method for color pixel arrays inside transparent media based on single-pulse modulation. This method can realize the one-step fabrication of three-dimensional color pixel arrays inside lithium niobate crystals with a single ultrafast laser pulse, thereby greatly improving the writing efficiency of multidimensional optical data.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] I. A method for single-pulse stereoscopic writing of color pixel array inside a transparent medium
[0007] Step 1: After partitioning the color pixelated pattern, generate multi-focus images of all partitions and extract the color information and Z-axis coordinate information corresponding to each partition;
[0008] Step 2: Combine the color information and Z-axis coordinate information of each partition to generate a hologram for the multifocal image of each partition, and obtain the holograms of all partitions and the corresponding sub-pulse energy;
[0009] Step 3: Fix the crystal sample on the displacement platform, then load the hologram corresponding to each partition into the spatial light modulator and set the mother pulse energy of the optical path system according to the sub-pulse energy of the current partition. Then process the color pixels of the current partition to complete the processing of the current partition. Then process the next partition according to the hologram and sub-pulse energy of the next partition until the processing of all partitions is completed.
[0010] Step 2 specifically involves:
[0011] Step 2.1: Divide the multifocal image of each partition into multiple singlefocal images, and then convert each singlefocal image into a corresponding singlefocal hologram;
[0012] Step 2.2: Based on the color information and Z-axis coordinate information of the current partition, the Fresnel zone plate phase, aberration phase and weighting factor are superimposed on each monofocal hologram, and then the monofocal holograms are superimposed by complex amplitude to obtain a multifocal hologram and the corresponding sub-pulse energy;
[0013] Step 2.3: After using the multifocal hologram as the initial input and performing iterative calculations, the hologram of the current partition is obtained;
[0014] Step 2.4: Repeat steps 2.1-2.3 to calculate the multifocal map of the remaining partitions, thereby obtaining the holograms of all partitions and the corresponding sub-pulse energies.
[0015] In step 2.2, the weight factor of the current partition is determined based on the color information of the current partition, and then the sub-pulse energy of the current partition is determined based on the weight factor of the current partition.
[0016] In step 3, when the sub-pulse energy is small, the angle between the sub-pulse polarization direction and the crystal optical axis is 45°, and when the sub-pulse energy is large, the angle between the sub-pulse polarization direction and the crystal optical axis is 90°.
[0017] In step 1, the number of partitions is determined based on the laser output power, objective lens field of view, and spatial light modulator damage threshold, and then the color pixelated pattern is partitioned based on the number of partitions.
[0018] The crystal sample is a lithium niobate crystal sample.
[0019] II. A computer device
[0020] The device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method.
[0021] III. A computer-readable storage medium
[0022] The medium stores a computer program that, when executed by a processor, implements the steps of the method.
[0023] IV. A computer program product
[0024] The product includes a computer program / instructions that, when executed by a processor, implement the steps of the method.
[0025] The present invention has the following beneficial effects:
[0026] This invention utilizes spatial light modulation technology to divide a single ultrafast laser pulse into multiple sub-pulses with specified optical parameters and positional information. This allows for the batch printing of color pixel arrays with a specified three-dimensional spatial distribution within a lithium niobate matrix in a one-to-many manner, significantly improving the writing speed of multidimensional optical data. For example, in traditional one-to-one point-by-point writing mode, the data point writing speed is at most comparable to the ultrafast laser repetition frequency, while the one-to-many three-dimensional writing mode can increase the data point writing speed by thousands of times, theoretically achieving GB / s level optical data writing.
[0027] This invention controls the optical parameters and spatial position of a multi-focal point through phase modulation. During the processing, it is only necessary to load the hologram frame by frame into the spatial light modulator and perform a small amount of simple lateral movement in the XY plane to achieve batch printing of three-dimensional color pixel arrays. It does not require the design of complex optical systems and scanning paths, nor does it require frequent adjustment of laser processing parameters. This greatly simplifies the processing steps, further improves processing efficiency, and ensures the stability of the processing.
[0028] This invention actively introduces aberration phase and weighting factors to regulate the focal length and energy distribution of each sub-pulse, thereby enabling each sub-pulse to induce amorphous pixels with different structural characteristics and produce different colors. This combined regulation strategy of focal length and energy distribution allows for one-step single-pulse printing of multiple color pixels with a single set of process parameters. This one-to-many structural color printing can currently only be achieved through the method proposed in this invention. Attached Figure Description
[0029] Figure 1 This is an overall structural diagram of the present invention.
[0030] Figure 2 yes Figure 1A schematic diagram illustrating the generation principle of a single-pulse modulated hologram.
[0031] Figure 3 yes Figure 1 Schematic diagram of a multi-focus array stereo writing system.
[0032] Figure 4 yes Figure 1 A schematic diagram of single-pulse writing of multidimensional data dot matrix. Detailed Implementation
[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0034] The overall design concept of this invention is as follows: A spatial light modulator is used to modulate an ultrafast laser pulse, dividing the incident single ultrafast laser pulse into multiple sub-pulses with specified three-dimensional spatial distribution, pulse energy, and focusing characteristics. Combined with the three-dimensional programmable processing characteristics of ultrafast laser direct writing technology, these sub-pulses can generate a multi-focal array inside a lithium niobate crystal, ultimately creating amorphous pixels with specified structural features, thus displaying different colors. Experiments show that this technology can mass-print color pixel arrays that can be easily recognized by intelligent imaging devices inside lithium niobate crystals, and has broad application prospects in fields such as ultra-high density data storage, three-dimensional color display, and information anti-counterfeiting encryption.
[0035] like Figure 1 As shown, the single-pulse stereoscopic writing of the color pixel array involves spatially modulating a single ultrafast laser pulse using a multi-focal loaded hologram to generate sub-pulses 24 with different parameters capable of inducing various color pixels. These sub-pulses 24 are then processed by the ultrafast laser stereoscopic writing system to ultimately induce a color pixel array. The color pixel array is generated in one step within a lithium niobate crystal using a single ultrafast laser pulse, eliminating the need for frequent adjustments to laser parameters and irradiation positions. A three-dimensional spatially distributed color pixel array can be written according to actual needs, and multi-dimensional information integration can be achieved by reusing colors and intensities.
[0036] like Figure 2 As shown, the present invention includes the following steps:
[0037] Step 1: Due to limitations in laser output power, the damage threshold of the spatial light modulator, and the field of view of the objective lens, the number of sub-pulses 24 that a single master pulse 23 can generate is finite. Therefore, the target pattern needs to be divided into a series of partitions, and the color and position information of all pixels in each partition needs to be extracted. One partition corresponds to one master pulse 23, and each pixel corresponds to one sub-pulse 24. The number of partitions is determined based on the laser output power, objective lens field of view, and spatial light modulator damage threshold. Then, after partitioning the color pixelated pattern to be written, multifocal images (grayscale images, each carrying XY coordinate information) of all partitions are generated, and the color information and Z-axis coordinate information corresponding to each partition are extracted. Among them, the required aberration phase and energy distribution are determined based on the extracted color information (RGB information), and the XYZ coordinates of the pixel are determined based on the extracted position information. The XY coordinates are automatically determined during partitioning, and the required Fresnel zone plate phase is determined based on the Z coordinate. The relationship between the color information and Z coordinates and each functional phase has been determined by a large number of process experiments and is directly called from the database during processing.
[0038] Step 2: Combining the color information and Z-axis coordinate information of each partition, a hologram is generated for the multifocal image of each partition, obtaining the holograms of all partitions and the corresponding sub-pulse energies; that is, based on the extracted information, the phase modulation of each partition is designed to induce the colored pixels within it. First, each pixel in a partition is considered a single focal point, thus dividing the partition into a set of single-focal images. Then, the inverse Fourier transform is applied to calculate these single-focal images into a series of single-focal phases with lateral position information (X / Y coordinates). For longitudinal positioning, single-focal phases with different longitudinal position information (Z coordinates) are achieved by introducing Fresnel zone plate phases. For color manipulation, aberration phases are introduced and superimposed on the single-focal phases to adjust the focal length of the single focal point in each partition, and the pulse energy of each sub-pulse is adjusted by multiplying the complex amplitude of the single-focal phase by a weighting factor. The value of the weighting factor is determined by the grayscale of the single-focal image.
[0039] Step 2 is as follows:
[0040] Step 2.1: Divide the multifocal image of each partition into multiple singlefocal images, and then convert each singlefocal image into a corresponding singlefocal hologram;
[0041] Step 2.2: Based on the color information and Z-axis coordinate information of the current partition, the Fresnel zone plate phase, aberration phase, and weighting factor are superimposed onto each monofocal hologram. Then, the monofocal holograms are superimposed using complex amplitude to obtain a multifocal hologram (this hologram can generate a multifocal array with specified parameters, including spatial position, focal length, and energy distribution) and the corresponding sub-pulse energy. The Fresnel zone plate phase is determined by the Z-axis coordinate information, while the aberration phase and weighting factor are determined by the color information. The Fresnel zone plate phase controls the focal Z-axis coordinate, specifically by superimposing the Fresnel zone plate phase onto each monofocal phase. This is because the Fresnel zone plate phase controls the position of the focal point in the laser incident direction (Z direction), i.e., the focal length. The aberration phase controls the focal length, and the weighting factor controls the energy distribution. This strategy is proposed because the structural color in lithium niobate crystals depends on the Z-axis length of the amorphous pixels. Experiments show that the color of a pixel redshifts as the Z-axis length increases, and blueshifts as the Z-axis length decreases. By superimposing aberration phase and weighting factors onto a single-focal phase, the focal length and corresponding pulse energy can be adjusted, thereby controlling the Z-axis length of the pixel. For example, keeping the pulse energy constant, increasing the focal length will decrease the energy density in the focal region, thus reducing the actual induced Z-axis length of the pixel, resulting in a blue shift in the pixel color. Similarly, keeping the focal length constant, increasing the pulse energy will increase the energy density in the focal region, thus increasing the actual induced Z-axis length of the pixel, resulting in a red shift in the pixel color. Experiments show that if appropriate pulse energy is allocated while adjusting the focal length, higher quality colors will be obtained, including improvements in saturation, contrast, and intensity. Therefore, the optimal combination of aberration phase and weighting factors can be determined through a series of orthogonal experiments to achieve high-quality color control. Simultaneously, experiments show that without introducing aberration phase, pixel color control cannot be achieved solely through pulse energy allocation. Therefore, the introduction of aberrations is essential in this technical solution. Specifically, the weighting factor of the current partition is determined based on the color information of the current partition, and then the sub-pulse energy of the current partition is determined based on the weighting factor of the current partition. The weighting factor is the relative magnitude of each focal grayscale value within the same partition.
[0042] Step 2.3: After using the multifocal hologram as the initial input and performing iterative calculations, the hologram of the current partition is obtained;
[0043] Step 2.4: Repeat steps 2.1-2.3 to calculate the multifocal images of the remaining partitions, thereby obtaining the holograms of all partitions and their corresponding sub-pulse energies. The holograms of all partitions are sequentially loaded into the spatial light modulator driving the laser direct-write system. Combined with the ultrafast laser direct-write system, single-pulse one-to-many stereoscopic writing of color pixels can be achieved.
[0044] Step 3: Fix the lithium niobate crystal sample on the displacement platform, then load the hologram corresponding to each partition into the spatial light modulator, and set the master pulse energy of the optical path system according to the sub-pulse energy of the current partition. Then process the color pixels of the current partition to complete the processing of the current partition. Next, process the next partition according to the hologram of the next partition and the sub-pulse energy, until all partitions are processed. It is necessary to adjust the polarization direction of the sub-pulse so that the polarization direction of the sub-pulse is set at an angle to the optical axis of the crystal. When the sub-pulse energy is small (<200nJ), the angle between the polarization direction of the sub-pulse and the optical axis of the crystal is 45°, and when the sub-pulse energy is large (>200nJ), the angle between the polarization direction of the sub-pulse and the optical axis of the crystal is 90°.
[0045] The printing process of this invention involves printing partitions one by one. One master pulse can print all the color pixels within a partition, thus achieving a one-to-many printing process. Experiments show that this printing strategy can increase the writing speed of multidimensional optical data by thousands of times, achieving GB / s level data writing. The number of partitions is only limited by the laser output power, objective lens field of view, and spatial light modulator damage threshold; the fewer the partitions, the faster the printing speed. Theoretically, the writing speed of this printing strategy has no physical upper limit and can be infinitely increased as long as hardware conditions permit.
[0046] The basic process of single-step stereoscopic writing of multi-dimensional data dot matrix inside a transparent medium is as follows:
[0047] like Figure 4 As shown, based on the designed color pixel pattern 21, a multi-focus hologram 22 required to generate the color pixel array is designed. The calculated hologram is loaded into the spatial light modulator 6, the pulse energy of the mother pulse 23 is set, the mother pulse 23 is modulated to generate a sub-pulse 24, and the sub-pulse 24 is focused into the lithium niobate crystal 18 through the objective lens 15 to generate a multi-focus array 16. A section of color pixels 17 is printed, and then it is moved to a new position to print the next section of color pixels 17. This process is repeated until the actual color pixel pattern 25 is finally printed.
[0048] Figure 3This is a single-step stereoscopic writing system for multi-dimensional data dot matrix inside a transparent medium. Computer 1 is connected to an ultrafast laser 2, shutter 3, spatial light modulator 6, and displacement platform 19 to control the laser processing. Specifically, computer 1 and ultrafast laser 2 control parameters such as the output power, repetition rate, and pulse width of the ultrafast laser pulses. The opening and closing of shutter 3 controls the pulse's passage and truncation. Half-wave plate 4 controls the pulse's polarization direction to meet the spatial light modulator 6's requirements for the incident light's polarization state. Reflectors 5 and 7 introduce and extract the laser into and from the spatial light modulator. Lenses 8 and 10 form a 4f system, matching the modulated laser beam with the entrance pupil of objective lens 15. Half-wave plate 9 adjusts the polarization state of sub-pulse 24. Dichroic mirror 14 reflects the ultrafast laser while transmitting visible light. The modulated ultrafast laser is focused by objective lens 15 into the lithium niobate crystal 18, generating a multifocal array 16, ultimately achieving the writing of color pixels 17. A lithium niobate crystal 18 is fixed on a displacement platform 19. The control port of the displacement platform 19 is connected to a computer 1 to realize the three-dimensional movement of the lithium niobate crystal 18. An illumination source 21 is placed below the displacement platform 19 to illuminate the sample for observation of the processing. A lens 12 and a camera 11 are used for real-time observation of the processed color pixels 17.
[0049] A single-pulse stereoscopic writing method for color pixel arrays inside a transparent medium includes the following steps:
[0050] Step 1: As Figure 3 As shown, the lithium niobate crystal 18 is fixed on the displacement platform 19 with its optical axis direction perpendicular to the laser incident direction. A 50x objective lens with a numerical aperture of 0.8 is used, and the camera 11 is used to determine a suitable processing position for subsequent stereoscopic writing of color pixel array.
[0051] Step 2: Input the processing parameters into computer 1, including the pulse energy, pulse width, shutter opening / closing, motion trajectory, and a series of multifocal holograms for printing all drives and all zones. Specific motion parameters are as follows: set the pulse width to 0.2-6 ps, the processing depth to 20-5000 μm, and set the pulse energy of the mother pulse 23 according to the laser output power, the damage threshold of the spatial light modulator, the field of view of the objective lens, and the energy distribution requirements of the sub-pulses. The shutter opening / closing and motion trajectory are determined according to the zone configuration. Furthermore, the scanning path needs to be determined based on the design requirements of the color pixelated pattern to be written.
[0052] Step 3: The first hologram is loaded into the spatial light modulator. The ultrafast laser 2 is activated, allowing a master pulse 23 to enter the optical path system along the center line of symmetry. The shutter 3 in the optical path system controls the passage and blocking of the master pulse 23, and the first half-wave plate 4 controls the polarization direction of the master pulse 23, enabling it to be modulated by the spatial light modulator 6. The modulated master pulse 23 is then guided into the spatial light modulator 6 through the mirror 5. The modulated master pulse 23 is split into sub-pulses 24, which are guided into the optical path through the mirror 7 and adapted to the entrance pupil of the objective lens 15 through a 4f system composed of the first lens 8 and the second lens 10. The second half-wave plate 9 is used to adjust the polarization direction of the sub-pulse 24, and the dichroic mirror 14 is used to guide the sub-pulse 24 into the objective lens 15. Finally, the sub-pulse 24 is focused by the objective lens 15 into the lithium niobate crystal 18, realizing the processing of a zone of colored pixels 17.
[0053] Step 4: Observe the printing quality of the colored pixels 17 through camera 11. Polarizers 13 and 20 form a cross-polarization system to generate color polarization signals for observing the color of the colored pixels 17. If the inspection is correct, control the displacement platform 19 to move the sample to a new position, load the next hologram into the spatial light modulator 6, and then control the ultrafast laser 2 to output a pulse to print the next partition. Repeating this process allows for single-pulse one-to-many stereo printing of a large number of colored pixels, achieving the desired effect. Figure 4 The actual printed color pixel pattern 25 is shown.
[0054] The entire cycle can be summarized as: loading the hologram - adjusting the energy of the master pulse - outputting the master pulse - moving the position - loading the hologram. The printed colored pixels can be used in fields such as 3D display, optical anti-counterfeiting, information encryption, and long-life ultra-high-density optical storage.
[0055] Finally, it should be noted that the above embodiments and descriptions are only used to illustrate the technical solutions of the present invention and not to limit it. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the disclosure of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the protection scope of the claims of the present invention.
Claims
1. A method for single-pulse stereoscopic writing of a color pixel array inside a transparent medium, characterized in that, Includes the following steps: Step 1: After partitioning the color pixelated pattern, generate multi-focus images of all partitions and extract the color information and Z-axis coordinate information corresponding to each partition; Step 2: Combine the color information and Z-axis coordinate information of each partition to generate a hologram for the multifocal image of each partition, and obtain the holograms of all partitions and the corresponding sub-pulse energy; Step 2 specifically involves: Step 2.1: Divide the multifocal image of each partition into multiple singlefocal images, and then convert each singlefocal image into a corresponding singlefocal hologram; Step 2.2: Based on the color information and Z-axis coordinate information of the current partition, the Fresnel zone plate phase, aberration phase and weighting factor are superimposed on each monofocal hologram, and then the monofocal holograms are superimposed by complex amplitude to obtain a multifocal hologram and the corresponding sub-pulse energy; Step 2.3: After using the multifocal hologram as the initial input and performing iterative calculations, the hologram of the current partition is obtained; Step 2.4: Repeat steps 2.1-2.3 to calculate the multifocal map of the remaining partitions, thereby obtaining the holograms of all partitions and the corresponding sub-pulse energies; Step 3: Fix the crystal sample on the displacement platform, then load the hologram corresponding to each partition into the spatial light modulator and set the mother pulse energy of the optical path system according to the sub-pulse energy of the current partition. Then process the color pixels of the current partition to complete the processing of the current partition. Then process the next partition according to the hologram and sub-pulse energy of the next partition until the processing of all partitions is completed.
2. The method for single-pulse stereoscopic writing of a color pixel array inside a transparent medium according to claim 1, characterized in that, In step 2.2, the weight factor of the current partition is determined based on the color information of the current partition, and then the sub-pulse energy of the current partition is determined based on the weight factor of the current partition.
3. The method for single-pulse stereoscopic writing of a color pixel array inside a transparent medium according to claim 1, characterized in that, In step 3, when the sub-pulse energy is <200 nJ, the angle between the sub-pulse polarization direction and the crystal optical axis is 45°, and when the sub-pulse energy is >200 nJ, the angle between the sub-pulse polarization direction and the crystal optical axis is 90°.
4. The method for single-pulse stereoscopic writing of a color pixel array inside a transparent medium according to claim 1, characterized in that, In step 1, the number of partitions is determined based on the laser output power, objective lens field of view, and spatial light modulator damage threshold, and then the color pixelated pattern is partitioned based on the number of partitions.
5. The method for single-pulse stereoscopic writing of a color pixel array inside a transparent medium according to claim 1, characterized in that, The crystal sample is a lithium niobate crystal sample.
6. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.
7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.
8. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method according to any one of claims 1 to 5.