Method for laser processing material by heating laser-assisted correlated processing laser

Abstract

A method of laser processing a material by heating a laser-assisted correlated processing laser, comprising: co-processing the material with a pair of lasers correlated to each other, one laser being configured to heat or excite, one laser being configured to process or form, the two lasers being correlated to the time and location of action of the material; according to the mutual correlation rule, the heating laser and the machining laser are projected to the material, and machining is carried out through the combined action of the heating laser and the machining laser; setting a relationship among parameters, paths and projection time of the two laser beams, when the heating laser is used for heating the material to be close to a critical point where the material has irrecoverable permanent change, projecting energy to an area required by final processing requirements by using the processing laser according to the determined processing range and quality, and accumulating the energy with basic energy provided by the heating laser, so as to obtain a final processing result; the material is permanently changed, and only the material in the area where the processing laser and the heating laser act together is permanently changed in an unrecoverable mode.

Description

Technical Field

[0001] The invention belongs to the technical field of laser material processing, and relates to a method for heating laser-assisted laser processing materials. Background Art

[0002] Processing materials is one of the most important uses of lasers. The goal of processing is often to cause irreversible, permanent changes in the material through laser irradiation. Processing requirements often limit irreversible, permanent changes to the irradiated area of the material. Furthermore, processing requirements can also include, contrary to the requirements for the irradiated area, leaving unirradiated areas as unaffected as possible or causing as little irreversible, permanent changes as possible.

[0003] Laser material processing, like most other processing technologies, consistently pursues three key objectives: high quality, high speed, and low cost. Quality, speed, and cost are essential factors in evaluating a technology. These three factors constrain each other, forming a triangular relationship known as the "magic triangle" of quality, time, and cost. Similar to the constraining relationship between the various elements of the "impossible triangle" in economics, these factors are ubiquitous and difficult to achieve simultaneously. Implementation can lead to a dilemma of choosing between two or even one of three, resulting in a compromise. This situation is particularly acute when applying existing laser material processing technology to micro-processing materials.

[0004] Laser micromachining is a new field in laser material processing, capable of meeting more stringent quality requirements. Compared to traditional processing methods, it offers numerous advantages, making it one of the best options for future manufacturing processes and, for some products, an irreplaceable processing method. While laser micromachining involves a variety of materials, with varying processing mechanisms and objectives, the requirements related to quality, speed, and cost are largely the same. Quality requirements can be roughly categorized into those for quality, precision, and appearance. Quality requirements include: changes in the processed material, such as cracks, burning, carbonization, remelting, discoloration, burrs, slag, and the size of the heat-affected zone. Precision requirements include: geometric dimensional accuracy, positional accuracy, form and position accuracy, taper from top to bottom, roundness or corners, batch processing precision stability, and precision consistency across different processing areas. Appearance requirements include: the overall morphology of the processed material, discoloration, spatter, contamination, burrs, and the clarity, smoothness, glossiness, and cleanliness of the machined surface, sidewalls, and interfaces. Speed requirements can be categorized into speed requirements for the preparation process, speed requirements for the processing process, and speed requirements for the inspection and measurement processes. Processing speed requirements include: length, area, volume, number of pieces, and number of parts processed per unit time. Cost requirements include: the cost of processing equipment, related supporting facilities, related human resources, processing-related material consumption, energy consumption, maintenance and management costs, and other costs.

[0005] Technological advances, particularly the increasing cost-effectiveness of ultrashort-pulse lasers, are propelling laser material micromachining technology beyond the laboratory and into the industrial realm. However, its current application is limited to solving challenging industrial tasks with high added value. Its widespread application as a universal machining tool in manufacturing remains constrained by a variety of conflicting technical constraints, the most significant of which is the conflict between machining quality and speed.

[0006] First, traditional laser processing mechanisms are either photothermal or a hybrid of photothermal and photochemical processing. The processing effect can be primarily thermal with other effects on the material, primarily photochemical with a small thermal effect, primarily photochemical with a secondary thermal effect, or a combination of photochemical and thermal effects. Regardless of the processing mechanism and the resulting effect, heat diffuses beyond the point of interaction between the light and the material, creating a large heat-affected zone (HAZ) in the processed material, which cannot perfectly meet the requirements of micromachining. For example, CO2 lasers with longer wavelengths are not absorbed by many materials, converting a large proportion of the incident light energy into heat. This inevitably leads to undesirable thermal effects such as burning and slag during the processing process. Furthermore, they are difficult to focus into a small spot, resulting in a small effective processing depth and a large spot diameter. This inherently does not meet the high-precision requirements of micromachining. Consequently, CO2 lasers are rarely used in micromachining.

[0007] For example, commonly used solid-state infrared lasers and fiber lasers with a wavelength of approximately 1064nm, solid-state and fiber-optic green lasers with a wavelength of approximately 532nm, and ultraviolet lasers with a wavelength of approximately 355nm can be focused into a small spot. The effective processing depth of the beam is considerable, and the spot diameter is quite small, which to some extent meets the high-precision requirements of micromachining. However, even with these relatively short-wavelength lasers, including the 355nm laser, the photon energy is not yet high enough to approach or exceed the level that can change or destroy the molecular and atomic structures of most substances. The processing mechanism is still thermal, or a combination of thermal and chemical reactions.

[0008] Compared to CO2 laser processing, this type of processing has a shorter wavelength and a higher absorption rate of light by the material. However, this does not completely eliminate the thermal effect after the light energy is converted to heat energy. The process of light energy conversion to heat energy and the diffusion of heat energy in the material is accompanied by the inevitable diffusion of heat energy beyond the point of action between the laser and the material, resulting in a heat-affected zone within a certain range of the processed material. If the parameters are not set properly, the processed material may crack, burn, remelt, discolor, and carbonize after processing. To improve processing quality, the processing parameters are often compromised between quality and speed, often losing one thing for the other: either reduce the pulse energy and slow the processing speed to meet quality requirements; or maintain the processing speed at a minimum, tolerate certain quality defects, and supplement with appropriate post-processing methods to eliminate the impact of thermal effects.

[0009] Secondly, the conflict between processing quality and speed becomes even more pronounced when using the developing ultrashort pulse laser for material processing, sacrificing speed to some extent. Advanced ultrashort pulse lasers minimize the heat-affected zone during processing, achieving so-called "cold" processing. The processing results meet most quality requirements for micromachining. However, compared to traditional laser processing, they are slower. This processing speed, and the resulting higher costs, makes it unsuitable for micromachining of general-purpose products in most industrial sectors, except for high-value-added, small-batch products.

[0010] Ultrashort pulse lasers are known to achieve very high pulse power densities. They interact with materials at extremely high speeds and for a very short duration. The energy at the point of impact completes the process before it has time to diffuse beyond the point of impact, limiting the area affected by heat to a very small area. This allows, to a certain extent, non-destructive processing of the remaining material on the workpiece. Unfortunately, power density and energy density are two different concepts; high power density does not necessarily mean high energy density. The fact is that, overall, current ultrashort pulse lasers have significantly lower power than common nanosecond lasers, meaning these advanced lasers deliver less energy in the same amount of time. High-speed processing, while also adhering to the law of energy conservation, undoubtedly requires high energy input. This high energy input presents a significant challenge for ultrashort pulse laser technology, requiring both high single-pulse energy and, in return, a high pulse repetition rate. High single-pulse energy ensures a sufficiently large processing volume per pulse. A high pulse repetition rate, coupled with high single-pulse energy, ensures a continuous supply of energy, ensuring a sustained processing process with a sufficiently large single-pulse processing volume. However, the high power density achieved by current ultrashort pulse durations only meets the high-quality processing requirements of so-called "cold" processing. Single-pulse energy and overall laser power are significantly lower than those of traditional CO2, solid-state, and fiber-based lasers, resulting in a very limited amount of material that can be processed per pulse. Compared to common nanosecond lasers, current ultrashort-pulse laser processing technology processes significantly less material per pulse in the same amount of time, resulting in a sluggish processing speed that is unsuitable for manufacturing standard products. For the foreseeable future, it is likely that, due to various limitations, the overall development of ultrashort-pulse laser technology will remain at a plateau. With no sign of a breakthrough in ultrashort-pulse laser technology capable of producing high single-pulse energy and high power, it will be difficult to achieve the high energy levels required for micromachining speeds in standard product manufacturing in the near future. Taking a step back, even with large single pulse energy and a high-repetition-rate laser light source based on large single pulse energy, there is still the problem of how to accurately and quickly transmit and distribute light pulses to the material to be processed. The existing laser material processing system uses a voice coil motor to drive the reflector to perform mechanical movement to distribute light pulses. Its resolution and response speed are too slow compared to the pulse repetition rate of millions, which also restricts the laser material microprocessing technology from entering the field of high processing speed and has become one of the obstacles that are difficult to overcome in the short term.

[0011] In addition, taking a step back, even if there is an ultrashort pulse laser light source that can simultaneously output large single pulse energy and high repetition rate based on large single pulse energy, as well as a beam transmission system that can transmit and distribute laser pulses at high speed, pushing laser material processing technology to a stage with better quality and faster speed, we must also see that the three elements of truly perfect technology are: quality, speed, and cost, and none of them can be missing.

[0012] The current situation is that common lasers with high speed and low price cannot meet quality requirements, and advanced lasers that meet quality requirements cannot meet speed and cost requirements. Commonly used lasers, such as carbon dioxide lasers with longer wavelengths, are sufficiently developed and have a sufficiently low price per watt of power output. Semiconductor lasers with high power, high efficiency, long life, and maintenance-free performance, but with lower beam quality, have a sufficiently low price per watt of power output due to their low manufacturing costs. Solid-state infrared lasers and fiber lasers with a wavelength of approximately 1064nm, commonly used in micromachining, as well as solid-state and fiber-optic green lasers with a wavelength of approximately 532nm and ultraviolet lasers with a wavelength of approximately 355nm, have varying quality and prices. However, as technology matures and competition intensifies, there is still considerable room for price reduction per watt of power output in the future. However, for various reasons, including various objective economic and technical reasons, the price per watt of power output of advanced ultrashort pulse lasers that only have the characteristic of stable high power density output is already expensive enough to be accepted by industrial-scale applications. In the future, even if the expected ultrashort pulse laser light source that can simultaneously output large single pulse energy and high repetition rate based on large single pulse energy appears, it is a luxury to hope that the price per watt of power output does not rise sharply. It is probably just a fantasy that is out of touch with reality if it does not fall or at least remains at the current price.

[0013] Is there a laser material micromachining technology that simultaneously achieves high processing quality, high speed, and low cost? This solves the dilemma of choosing between "quality, speed, and cost" when implementing laser material micromachining solutions. This dilemma often leads to a choice between "two of three," or even "one of three," often sacrificing one over the other. This paper, based on the current state and trends of laser technology development and addressing the universal manufacturing demands for quality, speed, and cost, is dedicated to developing a new technology. By optimizing the essential properties of different laser types, highlighting their respective advantages and mitigating their respective disadvantages, this paper proposes a method for laser material processing using a heating laser-assisted method related to the processing laser. This method aims to advance laser material micromachining technology to a new stage where both high quality and high speed can be achieved at an acceptable cost. Summary of the Invention

[0014] The present invention deeply analyzes the principle of interaction between materials and lasers, decomposes and combines the process of laser and material interaction in multiple dimensions in time and space, uses the heating laser in a pair of correlated lasers to heat the processed material to a critical point close to the material undergoing irreversible permanent change in an area equal to or larger than the final processing requirements, and uses the processing laser in the pair of correlated lasers to project energy onto the area required for the final processing requirements according to the determined processing range and quality. After accumulation with the basic energy provided by the heating laser, the material undergoes permanent change, completing the final processing.

[0015] The present invention believes that the essence of laser processing of materials is that, through laser irradiation, the material undergoes irreversible and permanent changes; the necessary condition for causing the material to change is the input of energy into the material, and the necessary and sufficient condition for causing the material to change is that the energy absorbed by the material exceeds the threshold value for the material to undergo irreversible and permanent changes.

[0016] It is important to understand that irradiating a material with a laser means delivering energy to the material in the form of light energy. However, not all of the energy delivered by the light source can be absorbed by the material, and not all of the absorbed energy can be converted into the energy required to cause irreversible permanent changes in the material. When a laser beam is irradiated on a material, three phenomena can occur: reflection, transmission, and absorption:

[0017] r+a+t=100%

[0018] Here, r is the reflectivity, a is the absorptivity, and t is the transmittance. Of these three physical phenomena, reflection and transmission are the processes of light transmission. In essence, the energy equivalent to this light is not absorbed. Reflected light shines on the material being processed, but is reflected by the material, changing direction before continuing to transmit. Transmitted light, while entering the material, merely passes through it, continuing to propagate. These two portions of light energy are transferred outside the material and continue to exist as light. They do not participate in the material processing and do not produce any processing effects on the material. Of the three physical phenomena, absorption is the process of converting light energy into other forms of energy. The absorbed energy participates in the material processing.

[0019] It can be seen from this that reducing the reflectivity and transmittance of the processed material to the projected laser is an effective way to fully utilize the laser energy generated by the laser and increase the processing speed. For example, in the prior art, there are methods of roughening the processed material to increase diffuse reflection, change the surface morphology of the processed material, and reduce the reflectivity; or methods of coating the surface of the processed material with a high light absorbance material to change the surface morphology of the processed material and reduce the reflectivity. For another example, in the prior art, there are methods of reducing the transmittance by doping the processed material with a light-blocking substance; or methods of using auxiliary lighting, electric baking and other heating means to increase the temperature of the processed material, increase the vibration amplitude of the particles that make up the material, and reduce the transmittance. In the present invention, a creative new method that is different from the prior art will also be used to more effectively reduce the reflectivity and transmittance of the processed material to the projected laser, as a way to make good use of the laser emitted by the light source and increase the processing speed.

[0020] Furthermore, the present invention specifically notes that there is another effective way to fully utilize the laser energy generated by the laser to increase processing speed: more efficiently utilizing the portion of energy absorbed by the material. This is because, even though the portion of light energy absorbed by the material participates in the material processing, not all of the light energy participating in the processing will necessarily cause the desired, permanent, irreversible change in the material, or assist in causing such change. In fact, the present invention has observed that a considerable proportion of the light energy absorbed by the material, during the processing, in the local range within the light action point, at the boundary of the action point, and outside the action point, causes the material to heat up, and then is released in a form that has no effective effect on the final effect, and is therefore wasted; even during the processing process, the action far exceeds the demand, in the local range within the light action point, at the boundary of the action point, and outside the action point, causing the material to overheat, causing negative, irreversible, and permanent changes after the heat is absorbed, resulting in undesirable processing effects on the processed material, such as discoloration, splashing, dirt and other negative thermal effects on the processed material, and destructive processing results such as burrs, cracks, burning, carbonization, remelting, and slag on the processed material. Therefore, it can be seen that more efficient utilization of the part of light energy absorbed by the material can be achieved from two aspects. The first is to reduce the proportion of the energy part that has no effect or negative effect on the final effect by only heating, or to convert the heating effect into the effect of causing irreversible permanent changes in the material as much as possible; the second is to control the light energy within the required range, so as not to overheat or over-process the material, that is, to make the material undergo the expected irreversible permanent change only at the point where the irreversible permanent change is required to occur, and after the expected change has occurred, before the heat is transferred to the material beyond the required processing point, especially before the heat is transferred to the material beyond the required processing point and causes the material to undergo irreversible permanent change, the energy delivery should be terminated immediately.

[0021] The present invention believes that in-depth analysis of the details of the laser-material interaction during the processing process will help find methods to ensure processing quality and improve processing efficiency. The present invention analyzes the interaction between laser and material from two aspects: the bonding and separation of materials, and the mechanism of the laser-material interaction.

[0022] Regarding the mechanisms of laser-material interactions in the field of laser processing, this paper notes several existing technologies, as well as several scattered proposals regarding these technologies found in publications or online. These proposals, each applicable to different situations, are summarized in the following categories: a thermal equilibrium mechanism explaining the interaction between lasers and materials from a physical perspective, a bond energy mechanism explaining the interaction between lasers and materials from a molecular perspective, and a Coulomb explosion mechanism and multiphoton effect mechanism explaining the interaction between lasers and materials at the scale of the relationship between atomic nuclei and extranuclear electrons.

[0023] From a physical perspective, the thermal balance mechanism of the interaction between lasers and materials suggests that when a laser strikes a material, the light (or light energy) entering the material can be divided into two components: energy that contributes to processing and energy that contributes to heating. On the one hand, as the exposure time increases, this energy gradually accumulates, focuses, and transforms into thermal energy, causing the temperature within a certain volume of the material to rise above a certain threshold, thus processing the material. On the other hand, due to the temperature difference between the affected volume and adjacent materials, the accumulated energy is transferred to the surrounding area in the form of heat. However, the temperature rise of the carrier material does not reach the threshold for material damage, resulting in only a limited heating effect on the material. During the time when the laser interacts with the material, as the light energy is input, the temperature in a certain volume of the affected material continues to rise, exceeding the range of energy values required to cause the material to undergo irreversible permanent changes. The material then undergoes phenomena such as melting, vaporization, and carbonization, which are permanent and irreversible, producing a processing effect. However, as the light energy is input, in a larger volume of the affected material, when the temperature rises to a certain value and the thermal effect expands to a certain extent, the temperature no longer rises and the range of action no longer expands due to the transfer of heat to adjacent materials in space. That is, when the heat input from the light source is equal to the heat output to the surrounding material space, a certain form of thermal equilibrium is reached. Although the volume of the material within the action range undergoes irreversible permanent changes, in a larger range and larger volume of the material, the direct light energy and the energy indirectly obtained through heat transfer are not enough to cause irreversible permanent changes in the material. When the external light energy transmission is stopped, the material returns to its original form, and only a limited-time heating effect is produced on this part of the material. During the laser processing process, for a certain material and certain processing parameters, when equilibrium is reached, the longitudinal depth and radial range of action on the material are both determined. The thermal equilibrium mechanism of the action between the laser and the material can roughly explain or calculate the effective radial range and axial depth of action of continuous laser or pulsed laser processing.

[0024] The molecular-level explanation of the bond energy mechanism of laser-material interaction focuses on molecular structure and laser wavelength. The interaction between lasers and materials is described based on the degree of match between photon energy and the energy required to induce internal molecular motion and disrupt molecular structure. This mechanism uses coupling to describe the degree of interaction between lasers and materials. Good coupling refers to a high proportion of the total energy entering the material, which in turn translates to high absorptivity, meaning that the resulting process more closely matches the intended target. The absorptivity depends on a variety of factors, but primarily on the laser wavelength and the material itself. The mechanism by which the absorbed laser interacts with the material—the difference between the desired process and the desired result—depends on the atomic structure and bond energy of the material's molecules, as well as the laser wavelength. Explanations can be broadly categorized as photothermal or photochemical.

[0025] The wavelengths of more common industrial laser equipment, from long to short, are roughly 10.6μm and 1064nm in the infrared band, 532nm in the visible light band, and 355nm in the ultraviolet band. The photon energy of lasers of different wavelengths is different. The shorter the wavelength, the greater the energy. In comparison, infrared light photons have low energy and their main effect on materials is thermal. Ultraviolet light photons have high energy and their main effect on materials is chemical. The wavelength of carbon dioxide laser is about 10.6μm, which is in the mid-infrared band of the infrared band. For example, when processing polymer materials, the laser of this wavelength is exactly equivalent to the stretching and rotational vibration frequency of plastic macromolecules, and is easily absorbed by plastics. However, the incident depth is at the level of hundreds of microns, the volume of the affected material is large, the optical power density per unit volume is low, and the energy of a single photon is low, about 0.12 electron volts. The energy of 0.12 electron volts cannot open the internal bonds of most polymer molecules. Therefore, carbon dioxide laser usually relies on the photothermal effect generated by the collision with the material structure to soften, melt, vaporize, and sublime the material to achieve the processing purpose, and the thermal effect accounts for a large proportion in the interaction with the material.

[0026] When processing the same polymer material, most materials are inherently transparent or translucent to visible and near-infrared light. Transparency, in this context, means that when light strikes the plastic surface, most of the energy is not absorbed, but rather gradually dissipated or transferred as it travels through the material, effectively failing to achieve the focused processing effect. Fiber lasers, the mainstream in the market today, have a wavelength of approximately 1μm and photon energy of approximately 1.16eV. Due to their low absorption rate and dispersed energy, they are insufficient to directly destroy macromolecules. Instead, they increase molecular motion and exert a significant thermal effect.

[0027] When processing polymer materials, lasers in the UV band are also easily absorbed by materials. For example, even for lasers with a longer wavelength of 355nm in the UV band, the absorption rate is quite large, the incidence depth is only a few microns, the volume of the affected material is small, the optical power density per unit volume is relatively high, and the energy of a single photon is high, up to about 3.5 electron volts, which is equivalent to the binding energy of some polymer molecules (polymers are mainly composed of H, C, O, and N, where the bond energy of the CH bond is about 3.5eV). A single photon can directly destroy the carbon-hydrogen bond of the polymer molecule itself. Therefore, the chemical reaction between the UV band laser and the polymer is obvious, the thermal effect is relatively small, and cold processing accounts for a large proportion of the processing process.

[0028] In the field of picosecond and femtosecond laser material processing, people use the Coulomb explosion mechanism and multiphoton effect to explain the mechanism of laser-material interaction from the scale of the relationship between the atomic nucleus and extranuclear electrons.

[0029] The Coulomb explosion mechanism states that when an ultrashort pulse, with a duration as short as picoseconds or femtoseconds, strikes the surface of a material, the laser light power density per unit volume is extremely high within a range comparable to the beam diameter but with a very small absorption depth, i.e., within a very small volume of material. This results in a very large number of photons acting instantaneously. Furthermore, due to the extremely large number of photons and the extremely high photon density, a considerable amount of the laser light energy is absorbed by electrons almost simultaneously within a very short period of time, converting it into kinetic energy. When the energy of the free electrons is sufficiently high, they break free from the constraints of the crystal lattice and escape, forming a positively charged plasma region on the surface of the material. Because the local area is no longer neutral, the charged particles form a self-consistent electric field, and the ions in the plasma are also subject to their own Coulomb repulsion. As the laser acts, the electric field strength increases. When it exceeds the critical threshold of the lattice potential, the repulsive force becomes greater than the lattice's binding force, causing these ions to become free particles and escape from the lattice, a phenomenon known as a Coulomb explosion. When the Coulomb explosion occurs, because the process lasts for an extremely short time, electron-phonon scattering has not yet occurred, that is, the temperature of the material has almost no obvious change, resulting in the formation of a new bonding structure between the material particles, which gradually tends to be stable, achieving a processing effect of no heat generation, or very little heat generation but causing irreversible permanent changes in the material.

[0030] The multi-photon effect believes that under the irradiation of a high-intensity laser beam generated by an ultrashort pulse of picosecond or femtosecond level, a very limited micro-area on the surface of the workpiece may absorb several, dozens, or even hundreds or thousands of photons at the same time, or even more. Compared with microsecond and nanosecond pulse lasers, the number increases by millions or thousands of times. Although the total energy of this multi-photon absorption that occurs almost at the same time is not large, the laser light power density per unit volume is extremely large at an extremely limited depth of action and within an extremely limited action volume, that is, a large number of photons can act at the same time. On the other hand, the materials in the area where the laser is applied, such as plastic polymer materials, have relatively complex composition and structure, and there are many mechanisms for the change of their properties, which can be the main chain, It can also be a branch chain, or a change in a certain group in the polymer, it can be a change in composition, or a change in the relationship between each other or in a statistical sense. After multi-photon absorption, because there are enough photons acting on the material at the same time, these photons can all satisfy or successively satisfy, relay, superimpose, and complement each other to satisfy one or more of the various changes required for composition changes, structural changes, energy level changes, changes in mutual relationships, etc., including the main chain bond energy, side chain bond energy, other binding forces, and the energy required for the force. Moreover, because the process lasts for a very short time, the vibration of the material particles that produce the thermal effect is not completed, and a processing effect of no heat, or very little heat causing irreversible permanent changes in the material is achieved.

[0031] The Coulomb explosion mechanism, or the multiphoton effect, best explains why when the optical power density is sufficiently high—that is, when a sufficient number of photons simultaneously impact a material—the multiphoton effect's impact on processing performance outweighs that of the laser wavelength / frequency. Even with infrared laser processing, when pulse widths are in the picosecond or femtosecond range, while the energy of a single pulse is low, ranging from tens to hundreds of microjoules, the power density—the power per unit area, typically measured in square centimeters—can reach millions, tens of millions, or even hundreds of millions of watts. Thus, when the power density exceeds a certain threshold, the multiphoton effect can achieve ideal processing results. Existing technologies exploit the multiphoton effect, using picosecond and femtosecond lasers to control the laser power per unit area per unit time, i.e., the laser power density, or laser intensity. This allows sufficient photons per unit area to sublimate and ionize the material, thereby altering its properties and achieving irreversible, permanent changes. The multiphoton effect not only explains why, when a single laser pulse of a given energy is compressed to the picosecond or femtosecond range, its interaction with materials becomes less dependent on the laser's wavelength (i.e., photon energy) than with microsecond and nanosecond lasers, and its dependence on the material type and structure becomes weaker. Furthermore, the multiphoton effect mechanism also explains why, compared to the processing results of commonly used lasers with longer wavelengths, such as CO2 lasers and fiber lasers, or lasers with weaker material coupling, plastics can achieve more optimal processing without the addition of light-blocking or light-absorbing additives. Furthermore, this processing is not a conventional hot process, but rather a sublimation and ionization micro-removal process acting only on a very small volume, a form of cold processing. In addition to the processing mechanisms of ultrashort laser pulses like picosecond and femtosecond lasers, the multiphoton effect and Coulomb explosion mechanism also explain, to some extent, the laser-material interaction phenomena that are difficult to achieve with continuous lasers but feasible with pulsed lasers or high-power single-point lasers.

[0032] In addition to the above-mentioned common mechanisms of laser-material interaction, through experiments, induction and analysis, the present invention conducts the following new explorations on materials and the interaction between lasers and materials.

[0033] In terms of materials, the present invention notes that common processed materials are mainly in gaseous, liquid and solid states. Among them, liquid and solid states are called condensed states. In the condensed state, the distance between atoms is very short, generating interaction forces. Because of this interaction force, the atoms are bound together to form a bond, which largely determines the morphology of the material. Atomic bonding is a bonding method of materials. Bonding is a description of the bonding force and bonding method between atoms, that is, the interaction force and interaction method between atoms, which greatly affects the performance of the material. At present, common bonding can be summarized as ionic bonds, covalent bonds, metallic bonds, van der Waals forces and hydrogen bonds. Among them, ionic bonds, covalent bonds and metallic bonds have stronger binding forces and possess stronger bonding forces, which are called chemical bonds, primary bonds and primary bonds. Metal materials are generally metallic bonds, inorganic materials are generally ionic bonds, and polymer materials are generally covalent bonds; van der Waals forces / bonds and hydrogen bonds have weaker binding forces and possess weaker bonding forces than general chemical bonds. They are often produced between molecules and are called physical bonds, weak chemical bonds and secondary bonds. The bonds between entire molecules and between entire molecular chains are van der Waals bonds and hydrogen bonds.

[0034] The present invention notes that common processed materials exhibit both atomic and molecular bonds, bonding based on a single type of bonding force, bonding based on two or more types of bonding forces at the same strength level, bonding based on two or more types of bonding forces at the same strength level, and bonding based on two or more types of bonding forces at different strength levels. For example, when metal atoms such as W, Ta, and Pb condense into solids, their bonding is a mixture of metallic and covalent bonds. For another example, oxide ceramic materials contain a significant number of covalent bonds in addition to ionic bonds. Polymers, polymer plastics, and composite materials are composed of numerous components, and their bonds involve atomic structure, molecular structure, and molecular morphology; they involve the primary components, as well as various components such as functional additives and fillers used for various purposes, such as modification; they involve bonds within a component and between components, resulting in a variety of bond types and varying bond strengths.

[0035] Based on the above understanding of material bonding, and after exploring the mechanism of laser-material interaction, the present invention proposes that: materials are composed of particles. Under certain statistical conditions, namely, at certain temperatures and pressures, there are relatively definite statistically or geometrically defined positional relationships between the particles. These relationships can be interpreted as inter-particle forces or fields. When the force or field weakens or is destroyed, the original state of the particles changes until they escape freely or stabilize in another state. When the original state of the particles that make up the material changes until they escape freely or stabilize in another state, the original structure or state of the material is destroyed, forming a new structure or state. This process is the processing of the material, and the result of the processing process is the processing result of the material.

[0036] The processing result can be a new structure or state produced when the original state of two, more than two, or all particles constituting the material changes until they escape freely or stabilize in another state, and the original structure or state of the material no longer exists; it can also be a new structure or state produced when the original state of one, two, or more than two particles, but not all particles, constituting the material changes until they escape freely or stabilize in another state, and the original structure or state of the material no longer exists.

[0037] The particles of the material are constantly moving in the form of vibration or other forms. The amplitude and frequency of the movement, the range of movement or the probability of occurrence within a certain range are affected by the energy received by the particles and are related to the temperature. Under certain statistical conditions, that is, under certain temperature and pressure, they are in a basic state in equilibrium with the thermodynamic state, or called the original state or normal state. For material processing, the basic state, original state, and normal state here refer to the state of the particles of the workpiece material before processing, in the environment of the processing site, but before being processed in the present invention.

[0038] The amplitude and frequency of material particle movement, the range of movement or the probability of occurrence within a certain range, reflect the strength of the force or field between particles. After the material particles receive energy, the amount of energy received changes the strength of the force or field between particles.

[0039] Although the amplitude and frequency of material particle movement, the range of movement or the probability of occurrence within a certain range are divided into levels, they are only divided into levels under certain measurement or observation methods. The actual levels may be more than what can be observed at present.

[0040] The amplitude and frequency of the movement of material particles, the range of movement or the probability of appearing within a certain range, and the change to a larger, higher, wider state, or to a smaller, lower, narrower state require a certain amount of time.

[0041] After receiving a certain amount of energy, a particle in a certain equilibrium state will experience a change in its amplitude, frequency, range, or probability of movement within a certain range. Although the amplitude, frequency, range, or probability of movement within a certain range will not allow it to escape freely or stabilize in another state, it will still move toward a larger, higher, and wider state, reaching a new equilibrium and entering an excited state with even higher internal energy. When the amplitude, frequency, range, or probability of movement within a certain range reach a certain level, i.e., a new ground state with even higher internal energy, and before returning to the original ground state, the amplitude, frequency, range, or probability of movement within a certain range will continue to expand, increase, and widen as the particle continues to gain energy, thus reaching a new equilibrium. Its internal energy will increase again from the original energy, placing it in a renewed state with further increased internal energy, a secondary excited state. This renewal process can continue until, as the particles continue to gain energy, their amplitude and frequency of motion, their range of motion, or the probability of appearing within a certain range, expand, increase, and widen to a certain point, such that if the particles gain further energy, they will irreversibly change and restructure the structural relationships between the original particles, or detach or escape from the original particle environment, permanently unable to return to the ground state, original state, or normal state. At this point, the particles are in a critical state or threshold state with extremely high intrinsic energy. For material processing, in the present invention, the level of the critical state and threshold state depends on the type of processing laser and the parameter settings.

[0042] Destroying the balance of forces or fields between particles of a certain intrinsic energy ground state causes the amplitude and frequency of its movement, the range of movement or the probability of appearing within a certain range to change towards a larger, higher and wider state, resulting in the free escape of particles or stabilization in another state. This can be accomplished at one time by a type A photon or photon stream with a sufficiently strong interaction with the material, or by the joint action of several photons or photon streams with different interaction intensities with the material, such as type A photons or photon streams and type B photons or photon streams in the form of succession, relay, superposition and supplementation. Specifically, it means that, compared with using only one type A photon or photon stream with sufficiently strong interaction intensity with the material, photons or photon streams with interaction intensity that can only make the particle reach its critical state, such as type B photons or photon streams and type C photons or photon streams, are sequentially, quasi-synchronously, or synchronously irradiated onto the particle in the basic state. Photons or photon streams, for example, type B photons or photon streams and type C photons or photon streams, and photons or photon streams that are type A photons or photon streams but whose interaction intensity with the material is not strong enough, jointly transmit energy to the particle, that is, rely on the sum of the energy transmitted by photons or photon streams with different interaction intensities, so that the particle passes through an excited state, a secondary excited state, one state, two or more critical states, and reaches the result of freely escaping the particle or stabilizing in another state. Moreover, the number of particles that freely escape or the number of particles that are stabilized in another state is greater than, much greater than, the number of particles that freely escape or the number of particles that are stabilized in another state that can be achieved by only type A photons or photon streams. In particular, it also means that, compared with using only one type A photon or photon flow of type A with a sufficiently strong interaction intensity with the material, photons or photon flows of type B and photon flows of type C are sequentially, quasi-synchronously, or synchronously projected onto the particle in the basic state, whose interaction intensity can only cause the particle to reach its critical state. For example, photons or photon flows of type A are no longer needed, and only photons or photon flows of type B and photon flows of type C are used to jointly transport energy to the particle. That is, the sum of the energy transported by photons or photon flows with interaction intensity weaker than that of type A causes the particle to pass through an excited state, a secondary excited state, one state, two or more critical states, and achieve the result of freely escaping the particle or stabilizing in another state. Moreover, the number of particles that freely escape or the number of particles that stabilize in another state is greater than, far greater than, the number of particles that freely escape or the number of particles that stabilize in another state that can be achieved by using only photons or photon flows of type A.

[0043] To destroy the balance of forces or fields between particles in a ground state of intrinsic energy, so that the amplitude and frequency of its movement, the range of movement or the probability of appearing within a certain range, change towards a larger, higher and wider state, and finally cause the particles to escape freely or stabilize in another state, the number of photons and photon streams required, that is, the strength of the interaction with the material, the difficulty of completing the interaction by multiple photons and photon streams in the form of succession, relay, superposition and supplement, that is, the number of steps of excited state, secondary excited state and critical state experienced, depends on the intrinsic energy of the state of the particle, which is manifested as the temperature of the material; the intrinsic energy of the state of the particle The higher the quantity, the higher the material temperature, the closer to the critical state of the particle, which will eventually lead to the free escape of the particle, or stabilization in another state, the fewer photons and photon streams are required, and the easier it will be to complete the task by the joint action of multiple photons and photon streams in the form of succession, relay, superposition, and supplement; in other words, under the premise of a fixed number of photons and photon streams, and under the premise of a fixed intensity of the joint action of multiple photons and photon streams in the form of succession, relay, superposition, and supplement, the higher the intrinsic energy of the particle's state, the higher the material temperature, and the closer to the critical state of the particle, which will eventually lead to a significant increase in the number of particles escaping freely or the number of particles stabilizing in another state.

[0044] For a short period of time, or a limited time, materials that are in a state of high internal energy and high temperature, including excited state, secondary excited state, and critical state, before reaching the level of free escape or stabilization in another state, if the particles no longer continue to gain energy, after a certain period of time, the material will return to the relatively definite statistical or geometric positional relationship between the particles under the corresponding temperature and pressure, that is, the inter-particle force or field state before the material was processed, that is, the basic state, original state, and normal state. At this time, under certain measurement or observation means, no processing traces will be shown, and this part of the material can still be restored to its normal state before the material was processed, that is, although it has been irradiated by laser photons or photon streams, the performance of the material will not be changed.

[0045] In a short time, or within a limited time, after the balance of the forces or fields between the particles in the basic state has been destroyed, the amplitude of its movement, the frequency of its movement, the range of its movement, or the probability of its occurrence within a certain range, will change towards a larger, higher, and wider state, eventually leading to the free escape of particles, or stabilization in another state. Under the premise of continuing to provide photons or photon streams with an intensity that can break the original critical state, the original critical state will continue to be broken, leading to the free escape of particles, or stabilization in another state. In a short time, or within a limited time, for a certain type of material, after the balance of the forces or fields between the particles in the basic state has been destroyed, the amplitude of its movement and the frequency of its movement will change towards a larger, higher, and wider state, eventually leading to the free escape of particles, or stabilization in another state. The rate, range of movement or probability of appearing within a certain range will change towards a larger, higher and wider state, which will eventually lead to the free escape of particles. Or under the premise of being stable in another state, continuing to provide photons or photon streams with an intensity less than that of photons or photon streams that can break the original critical state can also continue to break the original critical state, leading to the free escape of particles, or stabilization in another state. That is to say, once the critical state is broken, leading to the free escape of particles, or stabilization in another state, there will be a chain reaction, and the intensity of photons or photon streams required to continue to maintain the free escape of particles or stabilization in another state will become smaller.

[0046] While forming the above understanding, in the process of exploring the mechanism of the interaction between lasers and materials, the present invention was also inspired by the concepts of activated molecules, activation energy, and effective molecular collisions introduced by van't Hoff and Arrhenius when observing the relationship between chemical reaction rate and temperature. A heating or excitation laser is used to provide a sufficiently high basic energy for the processing laser, which is in a critical active state, so that the processing laser only serves to make up for the difference in energy between reaching and exceeding the energy required to cause irreversible permanent changes in the material.

[0047] In the process of exploring the mechanism of the interaction between laser and materials, the present invention is also inspired by the phenomenon that material damage often starts from the weak link. It is believed that destruction is a gradual process. First, some defect points are created in the material, causing the material to undergo point-like local damage. The energy required for destruction is continuously increased, so that the damage gradually increases until it penetrates and develops into a damage line, a damage surface, and a damage body, thereby achieving the processing effect.

[0048] In the process of exploring the mechanism of the interaction between laser and materials, the present invention is also inspired by the PN junction avalanche breakdown and Zener breakdown phenomena, and believes that destruction is an explosive process starting from a point. First, some defect points are created in the material to cause point-like local destruction of the material. Then, the energy required for destruction is increased rapidly and significantly, allowing the destruction to develop in a chain, avalanche, multiplication, or synchronous breakthrough manner, forming overall destruction, thereby achieving the processing effect.

[0049] Based on the above understanding and inspiration, the present invention has found a method for processing materials using two or more lasers, which is called combined laser processing in the present invention. That is, the heating laser in a pair of lasers that are correlated in time and space heats the processed material to a point close to, but not exceeding, the critical point at which the material undergoes irreversible permanent change in an area equal to or larger than the final processing requirements, wherein close means reaching the (1-x%) critical point. As needed, x can be 0.1, 0.2, 0.3, ..., 1, 2, 3, ..., 10, etc., and the subsequent mention of "close" is applicable to this limitation and will not be further explained. The processing laser in a pair of lasers that are correlated in time and space irradiates an appropriate amount of energy onto the material according to the range and quality determined by the processing requirements, and accumulates the energy with the basic energy provided by the heating laser. That is, it does not rely solely on the energy delivered by the heating laser or the energy delivered by the processing laser, but uses the heating or excitation laser and the processing laser to jointly deliver energy to the material, so that the energy absorbed by the material exceeds the threshold value at which the material undergoes irreversible permanent change, causing the material to undergo permanent change and completing the final processing. During the processing, it is necessary to control the effect of the energy delivered by the heating or excitation laser on the material so that it does not independently cause irreversible effects on the material.

[0050] The method of the present invention is to jointly process a material using a pair of mutually correlated lasers. One laser provides the necessary basis for processing, while the other provides the necessary and sufficient option for processing. One laser is configured to heat or stimulate, while the other is configured to process or shape. The time and location of the two lasers' interactions with the material are correlated. Following the rules of their correlation, the heating laser and the processing laser are projected onto the material, with the combined action of the heating and processing lasers effecting the processing. The parameters, paths, and exposure times of the two lasers are set. When the heating laser heats the material to a point near the critical point where irreversible permanent change occurs, the processing laser is then directed to the area required for the final processing, based on the processing range and quality. This energy, combined with the base energy provided by the heating laser, causes the material to undergo permanent changes. The irreversible permanent change occurs only in the area where the processing and heating lasers interact, completing the final processing. Among them, the power density of the heating laser and the power density of the processing laser can be set separately, but the range and time of the heating laser's action on the material are related to the processing laser. The power density of the heating laser is set to be less than and close to the threshold power density that causes irreversible changes in the material. The heating laser is used to pump light energy to the processed material as the basic energy of the processing process, heating the material to a critical point close to the material's irreversible permanent change; the spot diameter, processing path, and power density of the processing laser are set according to the range and quality required for the final processing. The processing laser is used to project energy on the area required for the final processing requirements. After accumulating with the basic energy provided by the heating laser, the power density acting on the material reaches and exceeds the threshold power density that causes irreversible permanent changes in the material, thereby achieving the final processing requirements.

[0051] In the present invention, depending on the material and processing task, and based on the present invention's understanding of the interaction mechanism between lasers and materials, the heating laser delivers auxiliary energy over a large area and in large doses, heating, exciting, and stimulating the material to an excited state with higher intrinsic energy, thereby indirectly amplifying the energy of the single pulse of the processing laser. The heating laser, which is correlated with the processing laser, pumps light energy into the processed material, serving as the basic energy for the processing process. This rapidly and significantly raises the material's temperature, increases the material's entropy, and increases the vibration amplitude, velocity, and frequency of one or more particles or groups in the material, thereby increasing effective collisions and reactions between particles. This allows particles in a certain equilibrium state to move at a range, frequency, or probability of appearing within a certain range, close to their free escape or stabilize in another state. This improves the processability of the processed material when irradiated by the processing laser, expands the processing parameter window for the processing laser, and reduces the requirements for processing laser power density and quality, thereby reducing the technical difficulty of laser material processing and achieving the goal of improving processing quality and efficiency.

[0052] It should be noted that the goal of the present invention is application. Just for the convenience of description and understanding, the lasers that are correlated with each other are divided into heating lasers and processing lasers, or into necessary lasers that provide basic energy and sufficient lasers that implement selectivity, or into excitation lasers that make the material reach an excited state, a secondary excited state, or a critical state and a destructive laser that causes particles to escape or stabilize in another state, or a breaking point laser that causes local defects to appear and a forming laser that maintains, expands, chains, and avalanches the range of destruction on the basis of the defects to achieve the final result. In the present invention, the auxiliary effect, heating effect, excitation effect, or stimulation effect, or even processing effect, forming effect, etc. of the lasers that are correlated with each other are not strictly distinguished, because according to the understanding of the present invention, in fact, the processing and forming are completed under the joint action of these lasers.

[0053] According to the present invention's understanding of the mechanism of action between laser and material, in the present invention, laser material processing is subdivided into two aspects: processing and auxiliary processing. Among them, processing specifically refers to forming a specific structure or texture on a material or workpiece as required. The spatial range of the processing effect on the material or workpiece is, within the error range suitable for the processing, less than, overlaps with, or roughly overlaps with the spatial range of the specific structure or texture to be formed. Auxiliary processing specifically refers to providing the necessary environment to ensure that the structure and texture of the processing meet the requirements in order to form a specific structure or texture on the material or workpiece as required. The spatial range of the auxiliary processing effect on the material or workpiece is less than, equal to / overlaps with, or roughly overlaps with the spatial range of the specific structure or texture to be formed, and intentionally and obviously, within a determined spatial range and time, is equal to / overlaps with or greater than the spatial range of the specific structure or texture to be formed.

[0054] In the present invention, the essence of the processing process of forming a specific structure and texture on a material or workpiece as required is to destroy the balance of force or field between one or more particles of the material under a certain basic state of intrinsic energy, so that the amplitude and frequency of movement of one or more particles constituting the material, the range of movement or the probability of appearing within a certain range, change towards a larger, higher and wider state. By causing one or more particles to escape freely or stabilize in another state, the original structure or state of the material is destroyed and a new structure or state is formed.

[0055] In the prior art, the aforementioned processing is accomplished in a single process using a single type of photon or photon stream, typically a laser of a single quality and technical grade. However, the present invention utilizes photons or photon streams of several lasers of varying quality and technical grades, acting in succession, relay, superposition, and supplementary fashion. Furthermore, the efficiency of the process, which creates specific structures and textures on materials and workpieces—in other words, the number of particles that escape freely or stabilize in another state—is significantly greater than using only lasers of a single quality and technical grade.

[0056] The present invention specifically refers to the method of sequentially, quasi-simultaneously, or synchronously irradiating one or more material particles in a base state with photons or photon streams of a lower quality, lower technical grade, with a lower intensity laser, as opposed to the photons or photon streams irradiated by the higher quality, higher technical grade laser used in the prior art. These photons or photon streams, combined with the photons or photon streams irradiated by the higher quality, higher technical grade laser used in the prior art, deliver energy to the particles. In other words, the sum of the energy delivered by the photons or photon streams of different intensities irradiated by the different quality, higher technical grade lasers causes the particles to pass through an excited state, a secondary excited state, one, two, or more critical states, and ultimately to escape freely or stabilize in another state, thereby achieving the desired processing result. Furthermore, the efficiency of the processing process for forming a specific structure or texture on a material or workpiece, i.e., the number of particles escaping freely or stabilizing in another state, is greater than that achieved using only the prior art laser of the same quality and technical grade.

[0057] The present invention specifically refers to the method of delivering energy to one or more material particles in a basic state by sequentially, quasi-simultaneously, or synchronously delivering photons or photon streams with an intensity sufficient to cause one or more particles to reach their critical state, compared to the photons or photon streams delivered by higher-quality, higher-tech lasers used in the prior art. This energy is then transferred to the particles by the combined delivery of photons or photon streams of lower-quality, lower-tech lasers at varying intensities, thereby causing the particles to pass through an excited state, a secondary excited state, and one, two, or more critical states, ultimately leading to the particles escaping freely or stabilizing in another state, thereby achieving the desired processing result. Furthermore, the cost of completing the processing process to form a specific structure or texture on a material or workpiece, i.e., the cost of the lasers required to achieve the same number of particles escaping freely or stabilizing in another state as in the prior art, is lower than that of using only lasers of the prior art quality and technical grade.

[0058] In the present invention, when a laser of higher quality and higher technical level in the existing technology is applied, its function is the processing function defined in the present invention, that is, forming a specific structure and texture on the material or workpiece as required; its range of action, within the error range suitable for the processing, is less than, overlaps with, or roughly overlaps with the spatial range of the specific structure and texture to be formed.

[0059] Compared to the higher-quality, higher-tech lasers commonly used in the prior art, when lower-quality, lower-tech lasers are used, their effects can be either processing or auxiliary processing as defined in this invention. This includes forming a specific structure or texture on a material or workpiece as desired; it also includes providing the necessary environment to ensure that the processed structure or texture meets the desired requirements. The scope of this laser's effect can be smaller than, equal to, overlap with, or roughly overlap with the spatial extent of the specific structure or texture to be formed; or it can be intentionally and clearly equal to, overlap with, or larger than the spatial extent of the specific structure or texture to be formed within a specified spatial range and timeframe.

[0060] The core of this invention lies in its increased application of lower-quality, lower-technical-grade lasers compared to existing technologies. On one hand, whether used for processing, auxiliary, or heating, lower-quality, lower-technical-grade lasers can rapidly and significantly raise the material's temperature, increase its entropy, and enhance the vibration amplitude, velocity, and frequency of particles or groups within it, thereby increasing effective collisions and reactions, thereby improving processing efficiency and reducing costs. On the other hand, even if this increased application is intentional, obvious, or necessary to optimize quality, efficiency, and cost, within a defined spatial and temporal range, its action range is set larger than the spatial range of the specific structure or texture to be formed. Due to its parameters, path, and exposure time, it has both overlapping areas with the processing laser, producing a processing effect, and independent areas of action. This limits the scope, duration, and degree of action on the workpiece being processed. Its exposure to or heating of the material does not adversely affect the processing process or results, or the structure, texture, or properties of the material or workpiece without the specific structure or texture, and serves only as an auxiliary processing aid. This is consistent with the understanding formed after the present invention explored the mechanism of interaction between lasers and materials, namely: for a short time, or a limited time, for materials in a high-temperature excited state or a critical state, as long as the particles have not yet escaped freely or the material has stabilized in another state, the energy input will be withdrawn. After a certain period of time, the material will return to its original state without showing any signs of processing, and exposure to lower-quality, lower-tech lasers will not change the material's performance.

[0061] The laser pair described in the present invention also includes a group of lasers that are correlated with each other, that is, two or more lasers that jointly process materials, wherein the function of some lasers is set to heating, and the function of other lasers is set to processing; includes a group of lasers that are correlated with each other, that is, two or more lasers that jointly process materials, wherein the function of some lasers is set to heating, the function of some lasers is set to processing, and the function of some lasers is set to both heating and processing.

[0062] The wavelengths of the heating laser and the processing laser are the same or different, and preferably the wavelength of the processing laser is smaller than the wavelength of the heating laser; the heating laser and the processing laser are both pulsed lasers, continuous lasers, or a combination of pulsed lasers and continuous lasers, and preferably the heating laser and the processing laser are both pulsed lasers; the pulse durations of the heating laser and the processing laser are the same or similar, or different or not close, and preferably the pulse duration of the processing laser is shorter.

[0063] The spot diameter of the heating laser interacting with the material is larger than the spot diameter of the processing laser interacting with the material.

[0064] When processing a continuous area of the material, the heating laser and the processing laser act together on the same point of the material at least for a relatively short period of time.

[0065] When the irradiation onto the material surface starts, the processing laser is delayed or synchronized with the heating laser; when the irradiation onto the material surface stops, the processing laser is delayed or synchronized with the heating laser.

[0066] The advantages and effects of the present invention are: increasing the single-pulse energy of the processing laser, improving the overall laser processing quality and efficiency, and reducing the processing difficulty. By utilizing a heating laser that is correlated with the processing laser to pump light energy into the processed material as the basic energy for the processing process, this method, on the one hand, raises the temperature of the material, increases the entropy of the material, improves the machinability of the processed material, expands the processing laser processing parameter window, reduces the requirements for processing laser power density and quality, reduces the difficulty of processing technology, and improves processing quality and efficiency. On the other hand, the parameters, path, and exposure time of the heating laser are correlated with the processing laser, and the scope, duration, and degree of effect on the processed workpiece are limited. Therefore, its exposure to and heating of the material will not adversely affect the processing process, processing results, or the properties of the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the optical path structure of a method for laser processing materials using a heating laser-assisted, correlated processing laser according to an embodiment of the present application.

[0068] Figure 2 It is a schematic diagram of the optical path structure of a method for laser processing materials using a heating laser-assisted, correlated processing laser according to another embodiment of the present application.

[0069] Figure 3 Schematic diagram of the spot sizes of the heating laser and the processing laser in a method for laser processing materials using a heating laser-assisted, correlated processing laser according to an embodiment of the present application. DETAILED DESCRIPTION

[0070] The present invention will be further described below with reference to the following embodiments. The following embodiments are illustrative, not restrictive, and the scope of protection of the present invention cannot be limited by the following embodiments.

[0071] Figure 1 This is a schematic diagram of the optical path structure of a method for laser processing materials with a heating laser-assisted related processing laser according to an embodiment of the present application. Figure 2 This is a schematic diagram of the optical path structure of a method for laser processing materials with a heating laser-assisted related processing laser according to another embodiment of the present application. Figure 3 Schematic diagram of the spot sizes of the heating laser and the processing laser in a method for laser processing materials using a heating laser-assisted, correlated processing laser according to an embodiment of the present application.

[0072] Example 1

[0073] This method uses a laser to process materials using a heating laser that is related to the processing laser. This embodiment uses a dual-laser combined light processing mode. The correlation lies in the fact that part of the optical path is coaxial transmission and acts on the same position of the material. For fixed-depth processing of alumina ceramics, this embodiment uses a combined light mode, using an infrared fiber laser for pre-processing, and then using a traditional green light picosecond laser for fixed-depth processing. While meeting quality requirements, the overall processing speed is increased from 40um to 50um. The specific implementation plan is as follows:

[0074] Step 1: Follow the steps below Figure 1 The structure shown in the figure is used to build the hardware optical path: infrared fiber laser 1, green picosecond laser 2, first infrared green light total reflection mirror 3, second infrared green light total reflection mirror 4, third infrared green light total reflection mirror 8, fourth infrared green light total reflection mirror 9, infrared transmission green light reflection mirror 5, green light beam 6, infrared light beam 7, first galvanometer mirror 10, and field mirror 11. Among them, the infrared light beam 7 is reflected by the first infrared green light total reflection mirror 3 and the second infrared green light total reflection mirror 4, and then transmits through the infrared transmission green light reflection mirror 5. The green light beam 6 is reflected by the infrared transmission green light reflection mirror 5. The two laser beams are coaxially transmitted, reflected by the third infrared green light total reflection mirror 8, and reflected by the fourth infrared green light total reflection mirror 9, and are incident on the first galvanometer mirror 10 and the field mirror 11. They are processed simultaneously during processing.

[0075] In step 2, infrared laser is used alone for processing. The infrared laser uses 20W power, 100kHz frequency, and a processing speed of 400mm / s. Under these parameters, there is no change in the alumina ceramic, including changes in physical properties and other properties. It is considered to be heating auxiliary light (i.e., heating laser).

[0076] Step 3: Use green laser alone for processing. The green laser uses 18W power, 400kHz frequency, and 400mm / s processing speed. Under these parameters, the depth of alumina ceramic removal is 40.76um.

[0077] Step 4: Use an infrared laser and a green laser to process together, turning on the lasers simultaneously and processing the same area. The green laser uses 18W power, 400kHz frequency, and a processing speed of 400mm / s as the processing light; the infrared laser uses 20W power, 100kHz frequency, and a processing speed of 400mm / s as the heating light. Figure 3 This is a diagram showing the relationship between the heating laser and the processing laser at the material being processed. Under these parameters, the depth of alumina ceramic removal is 48.9 μm.

[0078] This shows that the energy provided by infrared lasers as heating lasers per unit volume and per unit time is insufficient to cause irreversible damage to the material, whereas green light as processing light alters the material's properties. The combined effect of the heating and processing lasers is greater than that of the processing lasers alone, improving processing efficiency.

[0079] Example 2

[0080] This method uses a laser to process materials using a heating laser that is related to the processing laser. This embodiment uses a dual-laser combined light processing mode. The correlation lies in the fact that part of the optical path is coaxial transmission and acts on the same position of the material. For fixed-depth processing of alumina ceramics, this embodiment adopts a combined light mode, using an ultraviolet nanosecond laser as the heating light, and then using an ultraviolet picosecond laser for fixed-depth processing. While meeting quality requirements, the overall processing speed is increased from 190um to 220um. The specific implementation plan is as follows:

[0081] Step 1: Follow the steps below Figure 2 The optical path structure shown in the figure is constructed as follows: first ultraviolet nanosecond laser 12, first ultraviolet picosecond laser 13, second ultraviolet nanosecond laser 14, second ultraviolet picosecond laser 15, first ultraviolet reflector 16, second ultraviolet reflector 17, third ultraviolet reflector 18, fourth ultraviolet reflector 22, first half-wave plate 19, second half-wave plate 20, ultraviolet polarization beam splitter 21, second galvanometer 23, and telecentric field mirror 24. The second ultraviolet nanosecond laser 14 is converted to parallel polarized light by the first half-wave plate 19. After passing through the first and third ultraviolet reflectors 16 and 18, it is transmitted through the ultraviolet polarization beam splitter 21. The second ultraviolet picosecond laser 15 is converted to perpendicular polarized light by the second half-wave plate 20. After passing through the second ultraviolet reflector 17 and reflecting from the ultraviolet polarization beam splitter 21, it is transmitted coaxially with the second ultraviolet nanosecond laser 14. The two beams are reflected by reflector 22 and focused by the second galvanometer 23 and telecentric field mirror 24 to process the same location.

[0082] In step 2, ultraviolet nanosecond laser is used alone for processing. The ultraviolet nanosecond laser uses 2W power, 100kHz frequency, 300mm / s processing speed, and 20 processing passes. Under this parameter, there is no change in the alumina ceramic, including changes in physical properties and other properties, which is considered to be heating auxiliary light (i.e., heating laser).

[0083] Step 3: Use a UV picosecond laser alone for processing. The UV picosecond laser uses 5W power, 800kHz frequency, and a processing speed of 300mm / s. Under these parameters, the alumina ceramic is removed to a depth of 190um.

[0084] Step 4: Use a UV nanosecond laser and a UV picosecond laser to process together, turning on the lasers simultaneously and processing the same area. The UV nanosecond laser uses 2W power, 100kHz frequency, and a processing speed of 300mm / s as the heating light; the UV picosecond laser uses 5W power, 800kHz frequency, and a processing speed of 300mm / s as the processing light (i.e., the processing laser). Figure 3 This is a diagram showing the relationship between the heating laser and the processing laser at the material being processed. The number of processing passes is 20, and the depth of alumina ceramic removed under these parameters is 220 μm.

[0085] This shows that the energy provided per unit volume and time by a UV nanosecond laser as a heating laser is insufficient to irreversibly damage the material. However, a UV picosecond laser as a processing laser can alter the material's properties. The combined effect of heating and processing light is greater than that of processing light alone, improving processing efficiency.

Claims

1. A method for heating a laser-processed material by laser-assisted processing with a laser having a correlation, characterized in that include: A pair of lasers that are correlated with each other are used to jointly process materials, wherein the function of one laser is set to heat or excite, and the function of the other laser is set to process or form, and the time and position of the two lasers acting on the material are correlated; according to the mutual correlation rule, the heating laser and the processing laser are projected onto the material, and the processing is carried out by the joint action of the heating laser and the processing laser; the parameters, paths, and projection time relationship of the two laser beams are set, and when the material is heated by the heating laser to the critical point where the material undergoes irreversible permanent change, the processing laser is used to project energy on the area required for the final processing requirements according to the determined processing range and quality, and after accumulating with the basic energy provided by the heating laser, the material undergoes permanent change, and only the material in the area where the processing laser and the heating laser have acted together undergoes irreversible change. The power density of the heating laser and the power density of the processing laser can be set separately, but the range and time of the action of the heating laser on the material are related to the processing laser. The power density of the heating laser is set to be less than the threshold power density that causes irreversible changes in the material. The heating laser is used to pump light energy to the processed material as the basic energy of the processing process to heat the material to the critical point where the material undergoes irreversible permanent changes; the spot diameter, processing path and power density of the processing laser are set according to the range and quality required for the final processing. The processing laser is used to project energy on the area required for the final processing requirements. After accumulating with the basic energy provided by the heating laser, the power density acting on the material reaches and exceeds the threshold power density that causes irreversible permanent changes in the material, thereby achieving the final processing requirements.

2. The method according to claim 1, wherein: The method comprises processing a material with a group of lasers that are correlated with each other, each group of lasers comprising two or more lasers, wherein the function of some lasers is configured to heat and the function of other lasers is configured to process; or It includes using a group of lasers that are related to each other to jointly process materials, each group of lasers includes three or more lasers, among which the function of some lasers is set to heat, the function of some lasers is set to process, and the function of some lasers is set to heat and process.

3. The method according to claim 1, wherein: The wavelength of the heating laser is the same as or different from that of the processing or shaping laser; Preferably, the processing laser wavelength is shorter than the heating laser wavelength.

4. The method according to claim 1, wherein: The heating laser and the processing laser are both pulse lasers, continuous lasers, or a combination of pulse lasers and continuous lasers; Preferably, the heating laser and the processing laser are both pulse lasers.

5. The method according to claim 1, wherein: The pulse durations of the heating laser and the processing laser are the same or different; Preferably, the processing laser pulse duration is shorter than the heating laser pulse duration.

6. The method according to claim 1, wherein: The spot diameter of the heating laser interacting with the material is larger than the spot diameter of the processing laser interacting with the material.

7. The method according to claim 1, wherein: When processing a continuous area of the material, the heating laser and the processing laser act together on the same point of the material at least part of the time.

8. The method according to claim 1, wherein: When the irradiation onto the material surface starts, the processing laser is delayed or synchronized with the heating laser; when the irradiation onto the material surface stops, the processing laser is delayed or synchronized with the heating laser.

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