A biomimetic brain-like multilayer stack controllable step-by-step branch micro-crack optical waveguide storage medium

Abstract

The application discloses a kind of biomimetic brain multilayer stack controllable step-by-step branch microcrack optical waveguide storage medium, including brittle optical transparent substrate, three-dimensional guide etching channel is prepared by femtosecond laser, gradient directional stress induced cracking forming, three processes of partition differentiation low-temperature annealing stress regulation are prepared and formed, the step-by-step branch optical waveguide network including main trunk transmission light path, first branch light path, secondary distal end storage light path is formed in substrate, naturally form interlayer assembly accommodating cavity between multilayer structure, matched three-dimensional bidirectional closed loop light path and signal attenuation adaptive control module.The application realizes the controllable standardization preparation of microcrack light path, and has multilayer stacked structure and gradient stress distribution, and can be used as the standardization core substrate of photonic storage and calculation integrated device.

Description

Technical Field

[0001] This invention belongs to the technical field of brain-like photonic neural networks, three-dimensional integrated optical storage and photonic computing hardware, specifically involving a multi-layer stacked controllable hierarchical branched microcrack optical waveguide storage substrate based on stress-oriented molding process. Background Technology

[0002] Currently, there are only two main technological paths for the core transmission carrier of artificial photonic neural networks: The first is the femtosecond laser single-point direct-write planar optical waveguide process. This process has the advantage of nanometer-level processing precision, but the point-by-point scanning forming efficiency is extremely low. It can only realize the fabrication of two-dimensional planar optical waveguides and cannot construct multi-layer stacked three-dimensional neural topology structures. It is completely unable to replicate the operating logic of multi-level signal serial + parallel collaborative processing in the human cerebral cortex, and the hardware integration has a natural upper limit. The second is the unguided random stress-induced cracking fabrication of microcrack optical path scheme. This process has a higher forming efficiency, but the microcrack propagation path is completely random and unpredictable, the structural consistency between batches is extremely poor, it cannot form a standardized hierarchical branch topology architecture, the stability of the interference optical field signal cannot be guaranteed, and it is difficult to support high-precision matrix operations and long-term data storage application scenarios. The two existing mainstream technical solutions cannot simultaneously meet the two core requirements of large-scale mass production efficiency and three-dimensional structured controllable molding. Moreover, there is no integrated substrate solution in the industry that can simultaneously realize high-speed optical signal transmission, beam splitting and distribution, and non-volatile optical signal retention within a single optical substrate. This has become a key technical bottleneck restricting the application of high-end brain-like photonic chips. Summary of the Invention

[0003] This invention aims to overcome the technical shortcomings of existing planar laser direct writing processes, such as limited three-dimensional expansion and uncontrollable topology in random stress cracking processes. It provides a biomimetic, brain-like, multi-layered, controllable, hierarchically branched microcrack optical waveguide storage medium. It relies on laser pre-etched guiding channels to lock the crack propagation trajectory, and uses gradient-oriented stress-induced cracking to achieve standardized multi-level branching structure formation. Through a partitioned differentiated annealing process, a gradient residual stress field is constructed inside the substrate. A high-speed backbone transmission network and a long-lasting terminal storage array are simultaneously built in a single brittle optically transparent substrate, providing a standardized core substrate solution for photonic in-memory computing chips. To achieve the above-mentioned objectives, the present invention adopts the following complete technical solution: A controllable hierarchically branched microcrack optical waveguide storage medium, the main body of which is a brittle optically transparent substrate. The substrate is prepared by three core processes: pre-fabrication of three-dimensional guided etching channels by a femtosecond ultrashort pulse laser, gradient-oriented stress-induced cracking, and zoned differentiated low-temperature annealing stress control. A multi-layer stacked controllable hierarchically branched microcrack optical waveguide network is generated inside the substrate, which is divided into a main transmission optical path, a first-level branch beam splitting optical path, and a secondary terminal storage optical path. The interlayer assembly cavities are naturally formed between the multi-layer optical waveguide structures. Preferably, the brittle optically transparent substrate can be selected from fused silica glass, borosilicate optical glass, optically transparent ceramics, or single-crystal optical media; preferably, different annealing process parameters are configured for different optical path layers, and the secondary terminal storage optical path retains the gradient distribution of residual internal stress; preferably, a coherent optical field modulation unit is integrated inside the interlayer assembly cavity, and the optical path nodes are configured with photoinduced refractive index modulation nodes and a total internal reflection optical resonant closed-loop structure; preferably, the microcrack sidewalls form a process-specific periodic nanostep micro-marker morphology; preferably, the stress loading mode and refractive index modulation mode can be flexibly replaced and adapted according to the application scenario; preferably, the optical waveguide network can be constructed as a three-dimensional bidirectional closed-loop optical path structure, equipped with a signal attenuation adaptive control module with a 50Hz sampling frequency. Attached Figure Description

[0004] Figure 1 is a schematic diagram of the longitudinal cross-sectional structure of the multilayer stacked microcracked optical waveguide substrate according to an embodiment of the present invention; Figure 2 is a schematic diagram of the planar topological layout of the hierarchically branched microcracked optical waveguide according to an embodiment of the present invention. Detailed Implementation

[0005] High-purity fused silica glass was selected as the initial substrate preform. A femtosecond ultrashort pulse laser was used to perform layer-by-layer scanning etching of three-dimensional nanoscale guided etching channels within the preform, following a pre-defined three-level biomimetic neural branch topology. The channel depth coordinates corresponded one-to-one with the subsequent multilayer stacking layers, and the channel extension vector was pre-matched and calibrated with the subsequent stress loading vector. In this embodiment, the laser energy density was set to 2 μJ / μm, and the laser single-scan step size was set to 100 nm. The substrate blank with pre-etched guiding channels is fixed inside a high-precision directional stress loading fixture. A linearly increasing tensile stress is applied at a constant stress loading rate of 2 MPa / min, driving microcracks to extend strictly along the preset three-dimensional guiding etching channels. This sequentially forms the main transmission optical path, the first-level branch beam splitting optical path, and the secondary terminal storage optical path, constituting a complete hierarchical branched optical waveguide network. During the crack extension process, closed interlayer assembly cavities are naturally formed at the interlayer gaps. In this embodiment, the directional extension rate of microcracks can reach over 92%, and the surface roughness of the microcrack sidewalls is ≤200 nm. After forming, the microcrack sidewalls retain a periodic nanostep micromorphology bound to the laser scanning step size, with the step height stably maintained at 10 nm. This is a unique physical characteristic of this fabrication process and can be used as a basis for infringement tracing and identification. In this embodiment, the optical path cross-sectional dimensions are strictly matched according to 5:2:1. The width of the main transmission optical path is 100μm, the width of the first-level branch splitting optical path is 40μm, and the width of the secondary terminal storage optical path is 20μm. The vertical cavity height of the interlayer assembly accommodating cavity is set to 200μm. The molded substrate is placed in a zoned temperature-controlled annealing furnace to perform stress control processes: long-term heat preservation and low-speed linear cooling processes are performed on the main transmission optical path and the first-level branch splitting optical path areas to fully release internal residual stress and ensure the stability of long-distance optical signal transmission; short-term heat preservation and rapid cooling processes are performed on the secondary terminal storage optical path areas to retain the gradient distribution of residual internal stress field in a directional manner. The more distant the terminal branch is from the main optical path, the higher the residual stress value. At key intersection points of the optical path, the substrate lattice is densified and modified by localized focused irradiation with a femtosecond laser, generating photo-induced refractive index modulation nodes with an adjustable refractive index range of 10⁻³~10⁻². The optical path weights can be dynamically adjusted by external secondary laser irradiation. High-reflectivity dielectric films are deposited on all optical path end faces, with a film reflectivity ≥99.5%, constructing a total internal reflection optical resonant closed-loop structure to form a self-sustaining cyclic interference optical field. Coherent laser diodes are embedded inside the interlayer assembly cavity as standardized coherent optical field modulation units. In addition to the tensile stress loading and photo-induced lattice modification schemes used in this embodiment, compressive stress, temperature gradient thermal stress, ultrasonic coupling stress loading modes, or electro-optic phase modulation, thermo-optic coefficient modulation, and magneto-optic polarization modulation schemes can all achieve the same technical effect. Preferred Implementation Example 1 (Low Power Parameter Scheme) Borosilicate optical glass was selected as the substrate preform. The femtosecond laser energy density was set to 0.5 μJ / μm, and the laser scanning step size was set to 80 nm. Static compressive stress mode was used for stress loading, and the loading rate was set to 1 MPa / min. After molding, the directional extension rate of microcracks reached 91%, and the height of the periodic nanosteps on the sidewalls of the microcracks was approximately 8 nm. The cross-sectional dimensions of the optical path followed a ratio of 3:1.5:1, with a main transmission optical path width of 60 μm, a first-level branch width of 30 μm, and a secondary terminal width of 20 μm. The vertical cavity height of the interlayer assembly cavity was set to 100 μm. In the annealing process, the holding time of the main optical path was extended by 20%, and the cooling rate of the terminal optical path was increased by 30%, forming a more significant gradient stress distribution, which is suitable for low-power consumer applications. Preferred Implementation Example 2 (High Power Parameter Scheme) Single-crystal sapphire was selected as the substrate blank. The femtosecond laser energy density was set to 8 μJ / μm, and the laser scanning step size was set to 150 nm. Stress loading adopted a temperature gradient thermal stress mode, with a loading rate set to 4 MPa / min. After molding, the directional extension rate of microcracks reached 93%, and the height of the periodic nanosteps on the microcrack sidewalls was approximately 18 nm. The optical path cross-sectional dimensions followed a 5:2:1 ratio, with a main transmission optical path width of 200 μm, a first-level branch width of 80 μm, and a secondary terminal width of 40 μm. The vertical cavity height of the interlayer assembly cavity was set to 400 μm. This design is suitable for high-computing-power industrial applications. Instructions for implementing new features This solution introduces a new three-dimensional bidirectional closed-loop optical path structure. A reverse feedback optical path is deployed between the main transmission optical path and the secondary terminal storage optical path to form a bidirectional signal transmission closed loop, which can realize reverse verification of calculation results and weight closed-loop control. Simultaneously, a signal attenuation feedback adaptive control module with a fixed sampling frequency of 50Hz is integrated to collect the signal attenuation value of the terminal optical path in real time and dynamically adjust the output power of the coherent optical field modulation unit to ensure the stability of the signal strength of the entire optical path, and the signal fluctuation amplitude can be controlled within ±3%. The core working principle of this solution is divided into two parts: the forming mechanism and the operating mechanism. Forming Mechanism: The three-dimensional guided etching channel pre-etched by femtosecond laser forms a continuous mechanically weak surface inside the substrate. The gradient directional stress will be preferentially released along the mechanically weak surface, realizing full-process controllability of the microcrack propagation path and fundamentally avoiding the uncontrollable defects of random stress cracking path. The partitioned differentiated annealing process constructs a continuous gradient stress field inside the substrate by giving different layers of optical paths differentiated thermal histories. The high-stress terminal optical path can lock the phase state of the interference optical field to achieve data retention, while the low-stress main optical path ensures the lowest optical transmission loss. Operating Mechanism: The coherent optical field modulation unit outputs a reference coherent optical signal, which is distributed globally via the main transmission optical path. The photo-induced refractive index modulation node modulates the phase and intensity distribution of the optical field interference through refractive index changes, realizing linear matrix operations. After interference, the optical signal is split into the secondary terminal storage optical path through the first-level branch beam splitter path. The optical phase information is fixed by the residual stress field to complete non-volatile data storage, realizing the integration of storage and operation functions within a single substrate. The three-dimensional bidirectional closed-loop optical path and adaptive sampling module can realize closed-loop signal control, ensuring the stability of the optical path under all operating conditions. Beneficial effects

[0006] This invention uses laser pre-etched guide channels to anchor the crack propagation trajectory, and combines gradient directional stress-induced cracking to achieve controllable, standardized, hierarchical branching of microcracks. This solves the common technical bottlenecks in the industry, such as random paths and poor batch consistency in traditional stress cracking methods, while also taking into account both the efficiency of large-scale preparation and the accuracy of three-dimensional structure forming. The process naturally forms a multi-layer stacked structure and interlayer assembly cavities, eliminating the need for additional slotting, which greatly simplifies the fabrication process of three-dimensional photonic devices and provides standardized installation space for subsequent functional device integration. Differentiated stress distribution is achieved by using a partitioned annealing process. The stress in the main optical path is fully released to ensure transmission stability, while the gradient stress in the terminal optical path is retained to meet long-term storage requirements. For the first time, native integration of in-memory computing functions is achieved in a single optical substrate. The three core process parameters are deeply coupled, and the formed microcracks have detectable structural features such as high directional elongation and high sidewall regularity. The technical solution can be stably reproduced. The unique micro-step morphology of the process can be used as a product traceability feature, which greatly reduces the cost of proving intellectual property infringement. The addition of a three-dimensional bidirectional closed-loop optical path and adaptive sampling control significantly improves the stability and anti-interference capability of the optical path, making it suitable for complex operating conditions.

Claims

1. A controllable, hierarchically branched microcrack optical waveguide storage medium, characterized in that, The invention includes a brittle optically transparent substrate, which is fabricated using a femtosecond ultrashort pulse laser to pre-fabricate three-dimensional guided etching channels, a gradient-oriented stress-induced cracking process, and a zoned differentiated low-temperature annealing stress control process. The brittle optically transparent substrate contains a multi-layered, stacked, controllable, hierarchically branched microcrack optical waveguide network. This waveguide network is divided into a main transmission optical path, a first-level branch splitting optical path, and a secondary terminal storage optical path. Interlayer assembly cavities are formed between the multi-layered waveguide structures. The three-dimensional guided etching channels are arranged according to a preset multi-level branch topology trajectory, with the channel extension vector matched and coupled to the gradient stress loading vector. The microcracks extend directionally along the preset guided channels, with a directional extension rate ≥90%.

2. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, The brittle optically transparent substrate is selected from any one of fused silica glass, borosilicate optical glass, optically transparent ceramics, and single-crystal optical media, and the substrate lattice parameters are matched and adapted to the femtosecond laser pre-etched phase parameters.

3. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, The main transmission optical path, the first-level branch splitting optical path, and the secondary terminal storage optical path adopt differentiated annealing and heat preservation time and linear cooling slope process parameters, and the secondary terminal storage optical path retains the gradient distribution residual internal stress field.

4. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, The interlayer assembly cavity is equipped with a coherent optical field modulation unit, which is a laser emitting chip or an integrated coherent laser diode. The center wavelength of its output coherent light is matched and adapted to the geometric width of the microcrack slit, with an absolute wavelength deviation of ≤5nm.

5. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, Photoinduced refractive index modulation nodes are arranged on the microcracked optical path in a hierarchical manner. The refractive index of the nodes can be dynamically adjusted by external directional laser irradiation. The refractive index adjustment method is selected from any one of photoinduced lattice modification, electro-optic phase modulation, thermo-optic coefficient modulation, and magneto-optic polarization modulation. A total internal reflection optical resonant closed-loop structure is constructed on the end face of the microcracked optical path. The total internal reflection optical resonant closed-loop structure is a high reflectivity medium optical coating layer or an integrated total internal reflection prism.

6. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, The microcrack sidewalls generate periodic nanostep micromorphology corresponding to the laser scanning step size, with the height range of a single step being 5nm~20nm; the cross-sectional width ratio of the main transmission optical path, the first-level branch beam splitting optical path, and the secondary terminal storage optical path is (3~5):(1.5~2):

1.

7. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, The vertical cavity height of the interlayer assembly accommodating cavity ranges from 50μm to 500μm.

8. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, The energy density range of the prefabricated three-dimensional guided etching channel of the femtosecond ultrashort pulse laser is 0.1μJ / μm~10μJ / μm, and the stress loading rate range of the gradient directional stress induced cracking forming process is 0.5MPa / min~5MPa / min; the gradient stress loading mode is selected from any one of directional tensile stress, static compressive stress, temperature gradient thermal stress, and ultrasonic-assisted coupling stress.

9. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, The hierarchically branched microcracked optical waveguide network is constructed as a three-dimensional bidirectional closed-loop optical path structure. A reverse feedback optical path is set between the main transmission optical path and the secondary terminal storage optical path to form a bidirectional signal transmission closed loop.

10. The controllable hierarchical branched microcrack optical waveguide storage medium according to claim 1, characterized in that, The substrate integrates a signal attenuation feedback adaptive control module with a fixed sampling frequency of 50Hz. It can dynamically adjust the output power of the coherent optical field modulation unit according to the signal attenuation value of the terminal optical path.

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