Two-photon stereolithography writing system

Abstract

A stereolithography writing apparatus (1) for performing two-photon polymerization in a photopolymerizable substrate medium (100) comprises an electromagnetic radiation source (10) that emits a beam of photons (B) suitable for causing two-photon polymerization in the substrate medium (100), means (M1, M2, M3, WP1, AOM1, WP2, AOM2, M4, M5, WP3, AOD1, AOD2, M6, AL1, S, M7, AL2, M8, M9, OBJ1) for defining the optical propagation path of the photon beam (B) as it moves from the electromagnetic radiation source (10) toward the substrate medium (100), and beam control means (AOM1, AOM2, AOD1, AOD2) within the optical propagation path, which can manipulate the photon beam (B) to enable the occurrence of two-photon polymerization. The system comprises a beam control means for focusing the photon beam (B) within a selected target region of a substrate medium (100), and a means (30) for moving the substrate medium (100) relative to the photon beam so as to sequentially expose different target regions of the substrate medium (100) to the photon beam (B) and sequentially cause two-photon polymerization in those different target regions of the substrate medium (100), wherein the beam control means comprises at least one acousto-optic deflector (AOD1, AOD2) for spatially controlling the direction of the photon beam (B) as it travels along the optical propagation path, and at least one acousto-optic modulator (AOM1, AOM2) for modulating the intensity and / or frequency and / or cross-sectional parameters of the photon beam (B) as it travels along the optical propagation path.

Description

Technical Field

[0001] The present invention relates to a two-photon stereolithography writing system. More specifically, but without limitation, the present invention relates to a two-photon stereolithography writing apparatus capable of operating with a single or a plurality of optical writing beams for use in producing objects or structures, in particular two-dimensional or three-dimensional objects or structures, based on the principle of two-photon polymerization in a substrate medium, in particular a volumetric substrate medium. Such objects or structures may generally be very small or high-precision or fine microstructures, and have applications in various research, development, industrial and commercial fields, such as biology, medicine and physics, as well as other technical applications where very special functional surfaces are required, for example as security features. The present invention also relates to a method of forming such an object or structure using the apparatus, and to such an object or structure produced thereby. Background Art

[0002] Two-photon polymerization (hereinafter "2PP") is a well-known general concept. It generally involves projecting beams carrying two (or more) photons substantially simultaneously into a polymerizable substrate medium (usually a liquid) to form a voluminous (i.e., three-dimensional) object or structure in the medium by defining selected minute regions (called "voxels") in the medium where highly selective polymerization of the medium occurs at that point due to two-photon absorption. By gradually scanning the simultaneous two-photon beams across a suitable three-dimensional space within the substrate medium, points upon points and / or layers upon layers can be built from the polymerized solid material to construct the corresponding three-dimensional object or structure. This basic technique is often called "stereolithography." The method of fabricating such objects or structures by what is essentially a "writing" technique is therefore often called "stereolithographic writing" (hereinafter abbreviated as "SLW"). To date, many different types of objects or structures have been made possible by this technology, and they are typically three-dimensionally complex or particularly small in size and scale.

[0003] However, when it is desired to reduce the size of the objects or structures to be polymerized to microns or less, or even smaller, or to fabricate particularly complex three-dimensional structures, the current problem in this field when applying it to mass production on a feasible commercial scale is that most known SLW systems cannot perform the necessary optical scanning quickly or with sufficient precision. These limitations on writing speed and resolution impose significant constraints on the extent to which SLW technology can be designed and utilized to achieve favorable technical and economic effects in many technical and commercial fields.

[0004] In recent years, this limitation has been partially overcome by the rapid development of suitable femtosecond laser sources and recording media, thereby enabling the fabrication of some complex three-dimensional microstructures. Furthermore, some known UV single-photon SLW systems achieve high writing speeds along with relatively large voxel sizes, but their effectiveness and usefulness are limited by the diffraction limits of the focusing or imaging optics. Some two-photon SLW systems are known that can write partially diffracted structures with details as small as tens of nanometers. However, even with such high-end SLW devices (typically using galvanic mirrors to control the photon beam), the writing speed is still significantly slower than often required or ideal, especially in relation to the increasingly complex and precision-dependent structures that are increasingly desired to be fabricated using SLW technology. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] European Patent Application Publication No. 4163083 [Patent Document 2] International Publication No. 2022 / 034042 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, the main objective of the present invention is to address and mitigate the shortcomings and limitations of the known technologies of the above-mentioned SLW systems and apparatus, and to provide a new and improved form of SLW system and apparatus based on a novel optical control system that enables significantly faster SLW writing speeds and / or writing resolutions. [Means for solving the problem]

[0007] Therefore, in a first embodiment, the present invention provides a stereolithography writing apparatus, in particular a stereolithography writing apparatus for carrying out two-photon polymerization in a photopolymerizable substrate medium, the apparatus is An electromagnetic radiation source that emits a beam of photons suitable for inducing two-photon polymerization in a substrate medium, A means for defining the optical propagation path of a photon beam as it travels from an electromagnetic radiation source toward a substrate medium, A beam control means in an optical propagation path, which manipulates a photon beam to focus it into a selected target region of a substrate medium capable of generating two-photon polymerization, The system comprises means for moving the substrate medium relative to a photon beam so as to sequentially expose different target regions of the substrate medium to the photon beam and sequentially cause two-photon polymerization in those different target regions of the substrate medium, The beam control means is, At least one acousto-optic deflector that spatially controls the direction of the photon beam as it travels along the optical propagation path, The system comprises at least one acousto-optic modulator that modulates the intensity and / or frequency and / or cross-sectional parameters of a photon beam as it propagates along an optical path.

[0008] In a second embodiment, the present invention provides a method for producing an object or structure by the principle of two-photon polymerization in a photopolymerizable substrate medium, the method being: (i) Provide a stereolithography writing device according to the first aspect of the present invention or any embodiment thereof, (ii) Emitting a photon beam from an electromagnetic radiation source, operating the apparatus to propagate the beam along a light propagation path toward a substrate medium, controlling the photon beam by maneuvering it to focus it on a selected target region of the substrate medium so that two-photon polymerization occurs in the substrate medium, and moving the substrate medium relative to the photon beam so that different target regions of the substrate medium are sequentially exposed to the photon beam and two-photon polymerization occurs sequentially in those different target regions of the substrate medium, Controlling a photon beam includes spatially controlling the direction of the photon beam as it travels along the optical path by the action of at least one acousto-optic deflector, and modulating the intensity and / or frequency and / or cross-sectional parameters of the photon beam as it travels along the optical path by the action of at least one acousto-optic modulator.

[0009] In many embodiments of the second aspect of the above method, the method may be a method for producing a two-dimensional or (particularly) three-dimensional object or structure by the principle of two-photon polymerization in a volumetric, photopolymerizable substrate medium.

[0010] In a third aspect, the present invention provides an object or structure, in particular a two-dimensional or (in particular) three-dimensional object or structure, formed by the principle of two-photon polymerization in a photopolymerizable substrate medium using a stereolithography writing apparatus according to a first aspect of the present invention or any embodiment thereof, or a method according to a second aspect of the present invention or any embodiment thereof.

[0011] In a fourth embodiment, the present invention provides a control system for controlling a photon beam emitted by an electromagnetic radiation source of a stereolithography writing apparatus that performs two-photon polymerization in a photopolymerizable substrate medium, wherein the control system is located in the optical propagation path of the photon beam as it travels from the electromagnetic radiation source toward the substrate medium, and the control system is constructed and operable to steer the photon beam to focus it within a selected target region of the substrate medium in which two-photon polymerization can occur, and the control system At least one acousto-optic deflector that spatially controls the direction of the photon beam as it travels along the optical propagation path, At least one acousto-optic modulator modulates the intensity and / or frequency and / or cross-sectional parameters of a photon beam as it propagates along an optical path. It is equipped with beam control means that includes [the following components].

[0012] In the fourth embodiment of the control system described herein, the apparatus may be a stereolithography writing apparatus having functions including (in particular) beam control means as defined in the first embodiment or any embodiment thereof of the present invention as defined or described herein.

[0013] Therefore, the SLW system of the present invention may, in various embodiments, be used to create objects or structures that are typically defined as merely two-dimensional (for example, a surface or face (or surface or layer) of a particular material, or the material itself, in the form of a very thin planar film, web, or layer, in either case accompanied by fine surface details or textures substantially located within the thickness of such surface / face (or surface / layer) or film / web / layer itself), or, in practice, truly three-dimensional in nature, which is more common and useful. The SLW writing system of the present invention can be particularly effectively used to create often complex three-dimensional structures, such as microstructures, complex functional surfaces with complex three-dimensional surface features, etc., using 2PP.

[0014] In fact, the novel, high-speed, and high-precision method of the present invention, which controls the photon beam when maneuvering it to focus it on the surface / inside of any given selected target region of the substrate medium, makes it possible to write structures at a significantly higher speed and with greater precision than conventionally possible with known SLW systems (i.e., forming structures voxel by voxel through 2PP, particularly in a continuous or sequential writing surface), thereby enabling the rapid and high-precision formation of more complex structures, particularly in terms of forming voxels with greater precision and speed and joining adjacent voxels together.

[0015] More specifically, embodiments of the SLW apparatus and method of the present invention may be designed and operable to configure and operate a multi-beam, particularly two-beam or four-beam SLW system for writing / recording by generating 2PP substantially simultaneously in multiple regions / locations, for example, within a given voxel in a substrate medium, or in multiple regions / locations within adjacent but separate voxels.

[0016] Therefore, in some such two-beam systems according to embodiments of the present invention, beam control means, or in particular at least one acousto-optic deflector thereof, may be constructed and operable to perform simultaneous but separate spatial control, i.e., simultaneous but separate control of deflection, of first and second independent photon partial beams propagating substantially parallel to each other along at least a portion of the optical propagation path to the substrate medium.

[0017] In some such two-beam embodiment systems, the beam control means may comprise at least two acousto-optic deflectors, namely at least first and second acousto-optic deflectors, the first acousto-optic deflector being configured and operable to split the original photon beam into two separate sub-beams in the x-axis direction, and the second acousto-optic deflector being configured and operable to deflect the split sub-beams together in the y-axis direction, aligning them substantially parallel to each other, thereby in a desired final output direction for propagation thereafter to the substrate medium.

[0018] Accordingly, in some such four-beam systems according to embodiments of the present invention, beam control means, or in particular at least one acousto-optic deflector thereof, may be constructed and operable to perform simultaneous but separate spatial control, i.e., simultaneous but separate control of deflection, of first, second, third, and fourth independent photon partial beams propagating substantially parallel to one another along at least a portion of the optical propagation path to the substrate medium.

[0019] Further correspondingly, in some such four-beam embodiment systems, the beam control means may comprise at least first and second acousto-optic deflectors of the at least two acousto-optic deflectors, wherein the first said acousto-optic deflector is configured and operable to split the original photon beam into two separate partial beams in the x-axis direction, and the second said acousto-optic deflector is configured and operable to further split each of the two partial beams into two sub-partial beams in the y-axis direction (i.e., to form a total of four sub-partial beams), arrange them in a substantially mutually parallel configuration, thereby providing a desired final output direction for subsequent propagation to the substrate medium.

[0020] In any of the multi-beam embodiment types (i.e., two-beam or four-beam) of the SLW apparatus of the present invention defined above, each respective splitting and / or configuration of each respective beam or partial beam is effected by any of the following (i), (ii), or (iii), that is, (i) the nature of the combined control signal applied to one or more of the at least one acousto-optic deflector, (ii) dynamic modification of the combined control signal applied to one or more of the at least one acousto-optic deflector, (iii) a combination of (i) and (ii) may be implemented.

[0021] Furthermore, in some such embodiments of the preceding paragraph, such dynamic modification of the combined control signal applied to one or more of the acousto-optic deflectors may not only be used to control the cross-section of one or more of the deflected beams, but can also be usefully used to control the size of one or each respective voxel to be recorded / written (or at least one or more thereof), together with control of the position of said one or each respective voxel to be recorded / written (or at least one or more thereof).

[0022] In many embodiments of the present invention, the beam control means is Multiple acousto-optic deflector devices that spatially control the direction of a photon beam as it travels along its optical propagation path, The system may include a plurality of acousto-optic modulator devices that modulate the intensity and / or frequency and / or cross-sectional parameters of a photon beam as it propagates along an optical path.

[0023] In many embodiments of the present invention, beam control means including one or more acousto-optic deflectors and one or more acousto-optic modulators may form part of means for defining an optical propagation path, thereby ensuring that at least one acousto-optic deflector and at least one acousto-optic modulator are present in the optical propagation path, and that the photon beam interacts with both the at least one acousto-optic deflector and the at least one acousto-optic modulator as it travels along the optical propagation path.

[0024] In some embodiments of the present invention, the control of the photon beam by one or more acousto-optic modulators by modulating the intensity and / or frequency of the photon beam is performed on the following photon beam parameters, namely: (i) Amplitude of electromagnetic radiation forming the beam, (ii) Cross-sectional shape of the beam, (iii) Timing of radiation dose that can be propagated by the beam, (iv) The frequency (or wavelength) of the electromagnetic radiation that forms the beam. This may include controlling the photon beam by modulating any one or more of the following:

[0025] In the context of the present invention, one or each acousto-optic modulator may be any suitable acousto-optic modulator device that functions, or is capable of operating in such a way, to control the transmission intensity, power, cross-section, or frequency of a laser beam using electrically driven / controlled signals. That is, it may be a device that functions, or is capable of operating in such a way, to modulate one or more properties of electromagnetic radiation, in particular one or more of the transmission intensity, power, cross-section, or frequency, via acousto-optic effects. As a technical concept, acousto-optic effects are well known in the art and are based on the periodic modulation of the refractive index of a medium due to the presence of sound waves in that medium. Sound waves create in the medium what is substantially a grid of refractive indices, and electromagnetic waves interact with this grid in particular by diffraction. Thus, when used in embodiments of the present invention, an acousto-optic modulator may be a device that utilizes acousto-optic effects and uses sound waves to diffract electromagnetic radiation and shift its frequency. Such an acousto-optic modulator may also function to modulate the intensity of the propagating photon beam of electromagnetic radiation.

[0026] Generally, acousto-optic modulators can typically be equipped with piezoelectric transducers that generate sound waves in various types of materials, such as glass, quartz, or various crystalline materials, and various different types of acousto-optic modulator devices are known in the art for various practical applications that utilize such acousto-optic effects.

[0027] A suitable practical example of an acousto-optic modulator device that can be used in embodiments of the present invention is any of the various series available commercially and widely, for example, from CSRayzer or AAA Opto (and possibly other manufacturers / suppliers).

[0028] In many practical embodiments of the present invention, at least one acousto-optic modulator, and in particular at least one of a plurality of acousto-optic modulators, forming part of the beam control means may be of the "high-speed" type. That is, it may be an acousto-optic modulator where the velocity of sound waves in the medium is at least about 2000, 3000, or even 4000 m / s or higher (for example, in the case of a crystal of TeO2 as just one example of such a medium, the velocity of sound waves in the crystal is in the range of about 4200 m / s). This is in contrast to a "low-speed" type acousto-optic modulator (for example, operating in "shear" mode) where the velocity of sound waves in the medium is at most about 1000 m / s or lower (for example, in the case of the same crystal of TeO2, the velocity of sound waves in the crystal is in the range of about 650 m / s).

[0029] In such embodiments comprising multiple acousto-optic modulators, at least one of which is of the "high-speed" type, at least one other acousto-optic modulator among them, other than the at least one "high-speed" acousto-optic modulator, may be of the "low-speed" (or "normal" / "standard") type.

[0030] In the context of the present invention, one or each acousto-optic deflector may be any suitable acousto-optic deflector device that functions or is capable of operating in such a way as a photon beam travels through a medium within the device or as it is incident on a medium, thereby spatially controlling the direction or propagation direction of the photon beam. That is, it may be a device that functions or is capable of operating in such a way as to spatially modulate electromagnetic radiation or modulate its propagation direction via the acousto-optic effect. An acousto-optic deflector is a device that can be used to deflect an electromagnetic radiation (e.g., laser) beam in a given direction by a variable angle using the acousto-optic effect, wherein an electrically driven signal of (usually) constant power but variable frequency is applied to an acoustic transducer. Thus, when the acousto-optic deflector is in operation, the power driving the acoustic transducer is kept on, in particular at a constant level (although a variable level is also possible), while the acoustic frequency is changed to deflect the radiation beam to different angular positions. The acousto-optic deflector utilizes a diffraction angle that depends on the acoustic frequency, where the change in the diffraction angle is a function of the change in the acoustic frequency.

[0031] The amplitude of the acoustic grating in one or each acousto-optic deflector determines the modulation of the power of the deflected electromagnetic radiation beam. Therefore, the combination of the amplitude of the acoustic grating formed in one or each acousto-optic deflector and the frequency of the drive signal applied to it modulates both the electromagnetic radiation beam with respect to the deflection angle and the power of the deflected radiation beam.

[0032] Therefore, in basic physics terms, an acousto-optic deflector is similar to an acousto-optic modulator, but it is connected and operates differently in order to modulate the interacting electromagnetic radiation beam in a different way.

[0033] Similar to acousto-optic modulators, acousto-optic deflectors can generally comprise piezoelectric transducers that generate sound waves in various types of materials, such as glass, quartz, or various crystalline materials. Various different types of acousto-optic deflector devices are known in the art for various practical applications that utilize such acousto-optic effects when operating as acousto-optic deflectors using a frequency-variable drive signal.

[0034] A suitable practical example of an acousto-optic deflector device that can be used in embodiments of the present invention may be any of the various series available commercially and widely from, for example, AAA Opto (and possibly various other manufacturers / suppliers).

[0035] In some practical embodiments of the present invention, at least one acousto-optic deflector, in particular at least one of a plurality of acousto-optic deflectors, forming part of the beam control means may be of a "low-speed" type. That is, it may be an acousto-optic deflector where the velocity of sound waves in the medium is at most about 1000 m / s or less (for example, in the case of a crystal of TeO2 as just one example of such a medium, the velocity of sound waves in the crystal is in the range of about 650 m / s). This is in contrast to a "high-speed" type acousto-optic deflector where the velocity of sound waves in the medium is at least about 2000, 3000, or even 4000 m / s or higher (for example, in the case of the same crystal of TeO2, the velocity of sound waves in the crystal is in the range of about 4200 m / s). The use of such a "low-speed" type acousto-optic deflector may be acceptable (or even desirable) in terms of the electronic equipment used to control it (in terms of its nature, complexity, operation, and / or cost).

[0036] However, in some alternative practical embodiments of the present invention, where desired or appropriate, at least one acousto-optic deflector, or at least one of a plurality of acousto-optic deflectors, forming part of the beam control means may instead be of the "high-speed" type.

[0037] In embodiments comprising two or more such acousto-optic deflector devices, those two or any two such acousto-optic deflector devices may be oriented, positioned, or tilted such that each reference plane of those acousto-optic deflector devices is at a non-zero or non-180-degree angle with respect to each other, in particular at 90 degrees, i.e., perpendicularly, with respect to each other. In other words, within two or any two such acousto-optic deflector devices, they may be oriented, positioned, or tilted such that each reference plane is at a non-zero or non-180-degree angle with respect to each other, in particular at 90 degrees, i.e., perpendicularly, with respect to each other. Each such reference plane is defined by a plane that coincides with (or includes) the respective mounting base of the respective acousto-optic deflector device or is parallel to it. This perpendicular relative positioning or orientation may enable multiple such acousto-optic deflector devices to function to independently deflect photon beams in each of two orthogonal axial directions.

[0038] In embodiments of the present invention, means for defining the optical propagation path, in particular, one or more parts of the defining means other than at least one acousto-optic deflector and at least one acousto-optic modulator may comprise any number and any type of optical components that are either optically transparent or optically reflective, so that together they form or define the overall path of propagation or progression of a photon beam emitted by a radiation source and traveling toward a substrate sample.

[0039] Such optical components, which are either optically transparent or optically reflective, may include one or more mirrors for reflecting a photon beam in a desired modified direction of propagation, and / or one or more delay plates for changing the polarization (or other applicable parameter) of the photon beam passing through them. Suitable practical examples of such optically transparent or optically reflective optical components are widely available commercially, and their forms and functions are well known in the field of optics.

[0040] Therefore, from the definitions and general description above, it will become clear that the major difference between the SLW system according to the embodiments of the present invention and any known single-photon polymerization SLW writing system lies primarily in the writing resolution achieved by our new system. Furthermore, compared to other known two-photon polymerization SLW writing systems, the new system according to the embodiments of the present invention can achieve significantly higher writing speeds. This is achieved by (a) using high-speed optical devices (i.e., acousto-optic modulators and deflectors) instead of the galvanic micromirrors most commonly used in the prior art, which may need to be compensated for imperfections (e.g., non-homogeneity, nonlinearity), and (b) enabling a multi-beam writing mode, which in certain cases can enable writing speeds an order of magnitude faster. For example, while typical known 2PP-SLW writers have writing speeds of 100-625 mm / s, prototype embodiments of our new system can achieve speeds of approximately 600-3000 mm / s (about five times faster). Therefore, our new system significantly improves writing speed primarily by using a novel optical beam control system based on a new combination of acousto-optic deflectors and acousto-optic modulators, each consisting of multiple units, and often in unique combinations of specific types.

[0041] In practical embodiments of the present invention, the photopolymerizable substrate medium may comprise any suitable components or composition that provide, or enable, two-photon photopolymerization using the stereolithography writing apparatus of the embodiments of the present invention. Such a two-photon polymerizable substrate medium or composition may comprise any suitable substance or composition already known in the field of two-photon polymerization (2PP) to be suitable for fabricating two-dimensional or (particularly) three-dimensional objects or structures by the 2PP reaction process.

[0042] As used herein, the term “photopolymerization” is intended to be interpreted broadly and encompasses not only the true polymerization reaction of monomers initiated by electromagnetic radiation (e.g., UV or other wavelengths of light), but also the photo-induced crosslinking or curing of already partially polymeric or oligomeric precursors of the final polymerized or crosslinked or cured polymer material.

[0043] The recording material, i.e., the substrate medium on which 2PP is generated, must be absorbed and polymerized (or, since the word “polymerize” and its linguistic equivalent are intended to be encompassed when used herein) at an appropriate wavelength provided by an electromagnetic radiation source (e.g., a laser) and crosslinked or cured. In practical embodiments of the present invention, the recording material (i.e., the substrate medium on which 2PP is generated) may typically be mounted or housed in or on a suitable carrier, the carrier being, for example, a pad, plate, wafer, mat, container, or other transport structure, and may be any suitable material and size, shape and configuration, for example, depending on the shape and configuration of the final structure to be formed. As an example, preferred forms of such carriers may include, for example, silicon polished wafers and glass plates, as well as various other shapes of carrier structures.

[0044] Typically, in practical embodiments of the present invention, the recording material (i.e., the substrate medium on which 2PP is generated) may include a monomer or polymer precursor base and a two-photon polymerization initiator (i.e., a photoinitiator).

[0045] Various photoinitiators may be used in practical embodiments of the present invention, and there are many examples of suitable photoinitiators in the art. One such suitable example of a photoinitiator is 4,4'-bis(diethylamino)benzophenone (also abbreviated as DEAB) (available from various commercial manufacturers / suppliers), which is an organic compound belonging to the category of aromatic ketones. Its empirical molecular formula is C 21 H 28It has N2O and a molecular weight of 324.5 g / mol. Like other photoinitiators, DEAB has the ability to initiate (i.e., cause) chemical reactions using light. When exposed to ultraviolet (UV) light, electrons in the DEAB molecule are excited, thereby causing the molecule to decompose and form reactive radicals. These radicals can then react with other molecules, causing various reactions, such as polymerization of photopolymer precursor materials or formation of polymer backbones.

[0046] DEAB is useful as a photoinitiator in a variety of applications, including not only two-photon lithography but also photoreactive printing and the manufacture of copolymers and other materials. It is also known to be used in some photocatalytic systems and as part of other chemical reactions that oxidize organic compounds. It should be noted that DEAB is considered a highly toxic substance and can be harmful to human health if handled improperly. Therefore, it is important to take safety precautions and follow appropriate safety measures when handling this substance.

[0047] In some cases, the photoinitiator may be selected according to requirements of the completed 2PP writing structure (e.g., biocompatibility, among other possible final properties of the desired final structure).

[0048] Various other known photoinitiator substances or compounds may be used instead of DEAB, and there are many such examples of other such photoinitiators in the art that may be suitable for use in practical embodiments of the present invention.

[0049] The monomer or polymer precursor base component can essentially be any of the wide range of photopolymerizable (i.e., 2PP) monomers or polymer precursors, many suitable examples of which are known in the art. One such range of suitable polymer precursor materials is the organic-inorganic hybrid photopolymers belonging to the Ormocers (organically modified ceramics) category, available from Micro Resist Technology GmbH under the trademark Ormocomp®. These reagents are photosensitive polyimides and polyimide precursors, suitable for various microlithography and microstructure fabrication systems.

[0050] Ormocomp® polymers are photosensitive and, with proper initiation, react with ultraviolet light to form rigid and solid layers. These polymers are designed to be low viscosity at low temperatures, allowing for easy and precise application to carriers where the 2PP reaction occurs. Once initiated and exposed to ultraviolet light, these polymers polymerize by crosslinking to form high-strength solid materials that can be used in various microlithography and microsystem applications. Therefore, Ormocomp® polymers can be particularly useful as precursors for producing final polymer structures for use in microfluidic devices, microoptical elements, microsystems for biomedical applications, microelectronic devices, and many other types of microsystems. These polymers may also be suitable for the production of thin films and high-resolution microstructural features.

[0051] In practical embodiments of the present invention, various other polymer precursors, bases, or monomers may be used instead of the Ormocomp® polymer precursor, and many examples of such use are known in the art. Polymer materials may change properties after exposure to light. Therefore, depending on the specific type of photopolymer formed, a particular polymer precursor, base, or monomer may be selected for use.

[0052] Some of the more common photopolymer-based materials whose precursors or monomers can be polymerized by 2PP appropriately initiated according to embodiments of the present invention include the following: - Acrylate-based: These photopolymer materials are made from acrylate monomers that are polymerized using light. Acrylates are very reactive to UV light and have a wide range of end applications, making them very popular as photopolymer layers. - Epoxy-based: Epoxy photopolymers are made from epoxy monomers that polymerize with light. Epoxy photopolymers are often used to fabricate high-precision structures such as microelectronic components. - Cyclopentenone-based: These photopolymer materials are made from cyclopentenone and polymerize with light. Cyclopentenone photopolymers are commonly used to create optical elements such as lenses and optical fibers. - Silicone-based: Silicone photopolymers are made from silicone monomers and polymerize with light. Silicone photopolymers are commonly used to create flexible materials and elastomers such as sealants and silicone patches. - Styrene-based: These photopolymer materials are made from styrene monomers and polymerize with light. Styrene photopolymers are often used to create structures with high hardness and resistance, such as plastic parts.

[0053] For use in embodiments of the present invention, relevant / applicable polymer precursors or bases or monomers and photoinitiators may be mixed in any suitable relative ratio to obtain a final prepared substrate medium on which the 2PP reaction is carried out. Such suitable relative ratios will be readily apparent or can be calculated by those skilled in the art based on particularly known or supplied reagent data, and the usual art and knowledge of 2PP technology.

[0054] However, as an example, in one practical embodiment of the present invention using DEAB and Ormocomp® reagents, a mixed weight ratio of 1% DEAB to Ormocomp® may be commonly used. The DEAB photoinitiator may be appropriately pre-dissolved in a suitable solvent, such as methyl isobutyl ketone, in a weight ratio of, for example, 1:2 initiator to solvent.

[0055] In essence, in the practical implementation of embodiments of the present invention, any polymer material that can be produced by 2PP having desirable properties, such as flatness, adhesion to recording medium support material, resistance to laser beams, and insolubility to any developer used, may be designed to be produced by a 2PP method within the scope of embodiments of the present invention. If desired or necessary, by making appropriate adjustments to various parameters of the system of any given embodiment, such as adjusting the focusing technique, or by selecting the most suitable recording material (i.e., the substrate medium on which 2PP occurs), it may theoretically be possible to produce substantially any two-dimensional or three-dimensional structure using embodiments of the apparatus and method of the present invention.

[0056] In some practical implementations of embodiments of the present invention, it may be important or desirable to implement a precise and stable setting of the irradiation dose for polymerization of the material so that a structure can be successfully written into such a substrate medium / material. In our system, the magnitude of the irradiation dose may be controlled by very fast switching of a femtosecond (fs) laser beam by at least one of one or more acousto-optic modulators. The angular deflection of the recording beam may be ensured by a pair of acousto-optic deflectors, and in many practical embodiments of the present invention, it may be desirable to use multiple acousto-optic deflectors. In some embodiments, at least one further acousto-optic deflector may be present in the optical beam control system, whose function is to compensate for the temporal and spatial dispersion of the recording laser beam so that minimal dispersion occurs after the fs laser beam has passed through the entire optical beam control system. After being deformed by the optical beam control system, the laser beam may then be focused into the photopolymerizable monomer of the substrate medium by a microscope lens.

[0057] When carrying out practical embodiments of the present invention, the electromagnetic radiation generated by a source, such as a laser, and used to produce 2PP may be electromagnetic radiation within any desired region or subregion of the electromagnetic spectrum. In some practical embodiments, light in the visible region (e.g., wavelengths within the approximate overall range of about 380 nm to about 750 nm, particularly wavelengths within a relatively narrow band thereof (e.g., in the range of about 10 to about 40 or about 50 nm)) may be used. Alternatively, in other embodiments, electromagnetic radiation in the ultraviolet (UV) region (e.g., about 100 to 380 nm) or infrared (IR) region (e.g., about 750 nm to 500 μm) of the spectrum may be used instead. In practice, the most suitable wavelength of radiation suitable for use in any practical exemplary system may depend on the identification of the polymerizable monomer and its chemical properties in the substrate medium undergoing the 2PP SLW writing operation. Whatever wavelength of electromagnetic radiation is appropriate for use in any practical, exemplary system, a suitable source, such as a laser, may be used, and many such examples are readily available commercially in the art.

[0058] Within the scope of this specification, it is assumed that the various aspects, embodiments, examples, features, and alternative forms, in particular individual structural, constituent, or operational features described in the preceding paragraphs, claims, and / or the following description and accompanying drawings may be interpreted independently or in any number of such combinations. For example, individual features described in relation to a particular embodiment, or described alone or in combination with other features of one or more embodiments, are applicable in themselves or in combination with one or more other features to all embodiments, unless expressly otherwise specified or unless such features are incompatible, and may be found and used in combination with any other features of any embodiment.

[0059] Embodiments of the present invention and various features thereof will now be described in detail with reference to the accompanying drawings, all of which are non-limiting examples only. [Brief explanation of the drawing]

[0060] [Figure 1] This is an explanatory diagram illustrating the basic principles of one-photon excitation and two-photon excitation, the latter of which is used in the implementation of the embodiment of the present invention. [Figure 2] This is a schematic diagram of the general arrangement of the main components of a first general embodiment of the SLW apparatus according to the present invention. [Figure 3] Figure 2 is a perspective view of a physical prototype example of a two-beam SLW apparatus, schematically shown, illustrating its optical-mechanical structure. [Figure 4] These are front, left, and top plan views of the device shown in Figure 3. [Figure 5] This is a schematic diagram of the general arrangement of the main components of a second embodiment of the SLW apparatus according to the present invention, which is designed and operable as a two-beam SLW system. [Figure 6] This is a schematic diagram of the general arrangement of the main components of a third embodiment of the SLW apparatus according to the present invention, designed and operable as a 4-beam SLW system. [Figure 7(a)]This is an explanatory diagram illustrating some of the basic principles related to the synthesis and use of electrical control signals for controlling the operation of the AOD device used in the SLW apparatus according to the above embodiment of the present invention. [Figure 7(b)] This is an explanatory diagram illustrating some of the basic principles related to the synthesis and use of electrical control signals for controlling the operation of the AOD device used in the SLW apparatus according to the above embodiment of the present invention. [Figure 7(c)] This is an explanatory diagram illustrating some of the basic principles related to the synthesis and use of electrical control signals for controlling the operation of the AOD device used in the SLW apparatus according to the above embodiment of the present invention. [Figure 8] This is an explanatory diagram illustrating the basic principles related to the use of dynamically changing electrical control signals when controlling the operation of the AOD device used in the SLW device according to the above embodiment of the present invention. [Modes for carrying out the invention]

[0061] Referring first to Figures 1(a) and 1(b), these figures illustrate the basic principles of one-photon excitation and two-photon excitation, with the latter being used when performing 2PP using the new SLW apparatus according to embodiments of the present invention. Figure 1(a) shows a comparison of the absorption energy of a single photon by UV light (left-hand diagram) with the absorption energy of two photons by near-infrared light (right-hand diagram). Figure 1(b) schematically shows a comparison of the excitation volumes of one-photon excitation (i) and two-photon excitation (ii). In 2PP, the region outside the laser focus is less likely to exceed the polymerization threshold of the polymerizable substrate (e.g., photoresist). The proximity effect in 2PP is significantly lower than the proximity effect in 1PP (single-photon polymerization), which enables the fabrication of complex three-dimensional structures.

[0062] In embodiments of the 2PP SLW systems of the present invention, a major difference between these systems and any known 1PP (single-photon polymerization) systems is the achievable SLW writing resolution of the new systems. Two-photon excitation requires two photons at the same time and in the same location, but this probability is actually somewhat limited to a small spatial volume close to the beam's focal point, which in the context of 2PP technology is commonly referred to as a "voxel." Thus, the height and / or width of the voxel is typically in the range of about 1 micron to several (e.g., about 5, 10, or 20) microns in many practical embodiments of the systems of the present invention.

[0063] Moving to Figure 2, which schematically shows the general setup of the main components of the first embodiment of the SLW apparatus 1 according to the present invention. The SLW apparatus 1 comprises a multi-stage sequential arrangement of various optical components M1, M2, M3, WP1, AOM1, WP2, AOM2, M4, M5, WP3, AOD1, AOD2, M6, AL1, S, M7, AL2, M8, M9, and OBJ1, the identification and function of which will be described in more detail below. Together, they define the optical propagation path of beam B of electromagnetic radiation, i.e., photons, emitted from the laser source 10 to the substrate sample medium 100 on which the 2PP writing process is performed. Most of the optical propagation path components, from immediately downstream of the laser source 10 to immediately upstream of the last magnifying lens AL2, are mounted on a table or platform 20 made of granite (or other suitable ceramic material or a material that preferably provides high density and stability).

[0064] In practice, as will become clear from the following description, the entire optical system of the SLW apparatus 1 comprises two separate paths that the photon beam B, or a portion of beam B, follows as it travels throughout the apparatus 1. Firstly, there is an SLW recording path that performs 2PP writing within the substrate medium 100, and secondly, there is a detection path, which involves the use of a camera CMOS (along with associated optical equipment) to observe and monitor the 2PP writing process as it proceeds in the substrate medium 100.

[0065] The substrate sample medium 100 is mounted, for example, on a known commercially available type of mechanically movable (e.g., motorized) two-axis stage / positioning table 30, which supports the sample medium, for example, in a suitable container, via a vacuum fixture and performs the movement of the substrate sample 100 relative to the photon beam B on which the 2PP writing process is performed. The mechanically movable stage 30 may be any preferred known type capable of performing high-speed translational two-axis movement of the substrate sample medium 100, particularly in at least two orthogonal axes, to sequentially expose different target regions or parts within the medium 100 to the photon beam B and sequentially perform two-photon polymerization in those different target regions or parts within the medium 100. Component 50 represents a calibration photodiode that may be used in a system calibration procedure where it is desirable or required in practice (those skilled in the art will readily recognize and be familiar with how to do so). The movement of the stage / positioning table 30 is controlled by a voltage generated by a gate array unit. A high-speed CMOS camera is used to monitor, set up, and calibrate the apparatus. All program control and writing parameter settings for a field-programmable gate array (FPGA) may be controlled by a PC running appropriate software, as is common in known SLW writing systems.

[0066] As the laser source 10, a femtosecond laser may be used, typically operating with a wavelength of, for example, 515 nm, a laser power exceeding 2.3 W, an iteration frequency of 80 MHz, and a pulse length of 110 fs. One suitable commercially available femtosecond laser of this type and specification is the FLINT series available from Light Conversion. The photon beam B emitted from the laser 10 is first reflected from the underside to the upper surface of the granite table 20 by a mirror periscope formed by mirrors M1 and M2. As can be seen more clearly in Figure 3, a mounting plate 22 made of duralumin™ (a well-known range of alloys consisting of aluminum and copper, and usually small amounts of manganese and magnesium, which are particularly high-strength, hard, and lightweight) is stably mounted (e.g., by screws (not shown)) on this upper surface of the granite table 20. The mounting plate 22 is provided with an array of perforated screw holes 24 for mounting various components that form the majority of the optical propagation path of the photon beam B.

[0067] The main deflection and modulation components of the beam control means or system are located on this duralumin® mounting plate 22. To ensure the precise position and direction of the laser beam B as it travels along the first part of the optical propagation path and to facilitate its direction adjustment when necessary, a mirror M3 is positioned immediately downstream of the mirror periscopes M1 and M2. The mirror M3 has low group velocity dispersion (GVD) and is mounted on a motion positioning holder (not shown). The laser beam B then propagates through a first zero-order half-wavelength delay plate WP1 for high-precision polarization control and is incident on a first high-speed acousto-optic modulator AOM1, for example, made by CSRayzer. This first high-speed acousto-optic modulator AOM1 implements the precise timing of the irradiation dose of the photon beam B that the substrate sample medium 100 ultimately receives, controls the fs wave amplitude of the laser beam B, and also acts as a high-speed optical shutter to act as a fine compensator for the temporal dispersion fs of the laser beam B. A portion of the fs energy of laser beam B, which is first diffracted by the high-speed acousto-optic modulator AOM1, is used for the SLW writing operation.

[0068] Subsequently, the polarization twist angle of the propagating laser beam B is rotated in the appropriate direction by the second zero-order half-wavelength delay plate WP2, and the propagating laser beam B then enters the second acousto-optic modulator AOM2. Modulator AOM2 is, for example, an AAA Opto low-speed normal / standard type and serves as the primary fs dispersion compensator for laser beam B. Laser beam B is then reflected by a pair of low-GVD mirrors M4, M5 to a third zero-order half-wavelength delay plate WP3. After passing through this WP3 delay plate, the laser beam B, now in the correct polarization state, enters the first of a pair of "low-speed" type acousto-optic deflectors AOD1 and AOD2, for example, an AAA Opto, whose respective reference planes are oriented 90 degrees (i.e., perpendicular) to each other. These acousto-optic deflectors AOD1 and AOD2 angularly deflect the laser beam B to the required precise position so that the laser beam B performs the required 2PP writing in the intended target area or region within the substrate medium 100.

[0069] The deflected laser beam B is then reflected 90 degrees by an additional low-GVD mirror M6 and then passes through the first achromatic lens AL1. Beam B then passes through a circular aperture S to remove unwanted parasitic diffraction orders generated by the AOD1 / AOD2 combination. The transmitted beam B is then re-reflected by an additional low-GVD mirror M7 housed in a Thorlabs cage system motion holder fixed to the instrument's granite table 20 via a reduction to a vertical linear slide table (not shown). Beam B then passes through a second achromatic lens AL2.

[0070] The first and second achromatic lenses AL1 and AL2 together form part of an optical lens system that prepares the photon beam B for the final portion of the propagation path to the substrate sample medium 100 and a detection system that allows observation and monitoring of the 2PP writing process as it progresses within the substrate medium 100. Within this lens system, the deflected photon beam B is magnified by the two achromatic lenses AL1 and AL2, thereby ensuring that the diameter of beam B fills the rear aperture of the microscope objective lens OBJ1 (e.g., Olympus UPLAN SAPO100X Oil) and achieving a focal size limited by the diffraction of beam B. At the same time, to minimize the axial movement of beam B within any writing surface (in the substrate sample medium 100) where the 2PP writing is performed at any point in the entire 2PP writing procedure, the distance, relative position and focal length of the two achromatic lenses AL1 and AL2 are selected so that the first and second acousto-optic deflectors AOD1 and AOD2 are located in conjugate planes with the rear focal plane of the microscope objective lens OBJ1. This configuration enables very high-speed writing by using two acousto-optic deflectors AOD1 and AOD2 to deflect the laser beam B into the substrate sample medium 100 over a deflection range of at least 30 micrometers (for a 100X microscope objective lens OBJ1). For lower magnification microscope objective lenses, the increase in the deflection range may be proportional to the magnification of the microscope objective lens used and the magnification of the microscope objective lens having a magnification of 100X.

[0071] Next, the laser beam B is reflected by a further pair of low-GVD mirrors M8 and M9, each mounted on a motion mount, thereby reflecting the beam B 90 degrees each time, and the beam B then enters the entrance pupil of the microscope objective lens OBJ1. The beam B is then focused on the substrate sample medium 100 to the working distance of the microscope objective lens OBJ1. Both mirrors M8 and M9 are mounted via duralumin™ adapters to a vertical linear positioning table (e.g., Zolix) (not shown for clarity), which is mounted to the granite table 20 of the apparatus 1. The substrate sample medium 100 is, for example, silicon or glass with a photomonomer layer on its surface, and is fixed by vacuum spacers (not shown) mounted on a high-speed two-axis scanning table (e.g., Aerotech ANT95-L) that constitutes the movable stage 30 shown in Figures 2, 3, and 4.

[0072] The Zolix vertical positioning table is used for vertical adjustment of the possible writing surface (within the substrate sample medium 100) for substrate samples of different thicknesses, and for increasing the distance between the microscope objective lens OBJ1 and the vacuum spacer (through which the sample 100 is fixed to the scanning table / stage 30) for convenient substrate placement.

[0073] The SLW apparatus 1 is capable of writing on or within the surface of a substrate medium with a thickness ranging from a few micrometers (e.g., about 1, 5, 10, or 20 μm) to a few centimeters (e.g., about 1, 2, 3, 4, 5, 8, or 10 cm). To minimize thermal fluctuations in the apparatus frame structure, which houses various optical components defining optical propagation paths, the granite table or platform 20 may be mounted on an air-damped optical table 70, as shown in Figures 3 and 4. It is also highly desirable that the entire assembly of the operating components of apparatus 1 be enclosed in a light-shielding box (not shown) to prevent premature or unwanted light illumination of photomonomers in the substrate sample medium 100 throughout the entire SLW procedure, to meet health and safety requirements to protect workers from laser radiation, and to minimize temperature fluctuations experienced by the various optical components of apparatus 1.

[0074] As already mentioned above, the SLW apparatus 1 not only has a main SLW recording path that the laser beam B follows as it travels through the apparatus 1, but also a detection path that the reflected portion of beam B follows to observe and monitor the 2PP writing process as it progresses through the substrate sample medium 100. For such detection and monitoring, a CMOS (or alternatively, CCD) camera (e.g., Basler model acA2000-50gc) is used to display the focal position and shape of the reflected portion of the laser beam B re-emitted from the substrate sample medium 100. This reflected beam portion is focused through the objective lens OBJ1 and sent back to the mirror M9. Some of this reflected light is not reflected by the mirror M9, passes through the mirror M9, and enters the camera CMOS through the third achromatic lens AL3. Vertical positioning of the microscope objective lens OBJ1 may be performed by mounting the microscope objective lens OBJ1 on its own nanopositioning table (e.g., MC Labs) (not shown), if desired or required. As an alternative or addition, as already mentioned, the apparatus 1 houses a vertical linear table (e.g., made by Zolix), which is primarily for allowing vertical adjustment of the writing surface for substrate samples of different thicknesses and for increasing the distance between the microscope objective lens OBJ1 and the vacuum spacer (through which the sample 100 is fixed to the scanning table / stage 30) for convenient substrate placement, but the vertical linear table may also be used to position the microscope objective lens OBJ1 itself with micrometer-scale precision.

[0075] Therefore, as is clear from the above explanation, the optical propagation path of the device 1 consists of two paths: a recording path and a detection path. The recording path includes a writing laser beam source 10, a periscope consisting of mirrors M1 and M2, a reflective mirror M3, a zero-order half-wavelength delay plate WP1, a first acousto-optic modulator AOM1, a second zero-order half-wavelength delay plate WP2, a second acousto-optic modulator AOM2, mirrors M4 and M5, a third zero-order half-wavelength delay plate WP3, two mutually perpendicular first and second acousto-optic deflectors AOD1 and AOD2, a reflective mirror M6, a first achromatic lens AL1, an aperture S, a reflective mirror M7, a second achromatic lens AL2, reflective mirrors M8 and M9, and finally a microscope objective lens OBJ1. On the other hand, the detection path includes a microscope objective lens OBJ1, a third achromatic lens AL3, and a camera CMOS. Mirror M9 has no optical function in the detection path. In fact, the advantage here is that only a portion of the transmitted light from the substrate sample medium 100 that passes through the mirror M9 is sufficient for detection by the camera CMOS.

[0076] The overall control system of apparatus 1, in which various optical components can be controlled to perform the entire required SLW procedure, may include, for example, a high-speed FPGA card (e.g., Xilinx Zynq-5000) that runs software capable of making changes to various recording parameters such as irradiation dose, the number of simultaneous beam focuses, the position of the laser focus, and the positioning of the 2-axis scanning table / stage 30. This software may also be used to process the relevant input datasets.

[0077] For clarity, one aspect of the above description of the function and operation of the main optical components of Apparatus 1 may require a little further explanation: the problem of dispersion compensation for the femtosecond laser beam. Such dispersion compensation can be important for an optical system configuration that can operate without problems. This will be discussed in the following paragraphs.

[0078] The transmission or reflection of laser beam B by various optical components forming the optical path results in a temporal dispersion effect, which manifests as an extension of the laser pulse length. This physical property of fs lasers may need to be taken into consideration and appropriately compensated for in order to achieve high power density at the beam's focal point. Another factor that causes dispersion in both angle and time is the properties of the acousto-optic deflectors AOD1 and AOD2 themselves. By an appropriate combination of geometric coupling and modulation frequency, the angular and temporal dispersion of the fs pulse can be reduced. In the prototype setup of the present invention as described above, this is done as follows: The effect of each optical component is calculated, and the laser pulse length is pre-compensated by this value so that the first and second acousto-optic modulators AOM1 and AOM2 are adjusted to an angle of 45 degrees, and the wave modulation direction in the crystal is opposite to the modulation vector of the pair of deflecting acousto-optic crystals in the acousto-optic deflectors AOD1 and AOD2. The distances between AOM1 and AOM2, and between AOD1 and AOD2, are such that pre-chirp of the fs laser pulse occurs in AOM1 and AOM2, which compensates for the chirp caused by AOD1 and AOD2 (and possibly other optical components) as the laser beam passes through and enters the downstream focusing portion of the device, AL2, OBJ1, etc.

[0079] One of the key operational features of many embodiments of the present invention, and one of the key characteristics of apparatus 1 of the above embodiments, is that apparatus 1 can perform highly effective and high-speed SLW writing in the substrate sample medium 100. The first acousto-optic modulator AOM1 is of the high-speed type. Thus, the sound wave propagates through its crystal at a speed of about 4200 m / s, i.e., unlike the second acousto-optic modulator AOM2, which is of the low-speed normal / standard type and the sound wave travels at about 650 m / s. Thus, the combined use of such a first (high-speed) acousto-optic modulator AOM1 and second (low-speed / normal) acousto-optic modulator AOM2 enables both dispersion compensation and high-speed on / off switching of the laser beam B. Thus, to clarify, the high-speed on / off switching of the laser beam B is performed by the first (high-speed) acousto-optic modulator AOM1, and its control signal (i.e., its amplitude and / or frequency) is changed during the switching operation. On the other hand, the control signal for the second (low-speed / normal) acousto-optic modulator AOM2 does not change during the switching operation because its operating speed is not critical.

[0080] In addition to the above-described key features that form the basis of the apparatus 1 described above, which has a high writing speed within the substrate sample medium 100, a further novel and useful feature of embodiments of the present invention is that the system can be designed and operated with multiple writing beams, for example, to constitute a two-beam or four-beam SLW system. Figures 5 and 6 show the respective basic setups of these types of multi-beam SLW apparatuses 1' and 1'' according to second and third embodiments of the present invention, respectively. In such multi-beam embodiments, writing / recording is possible by performing 2PP in multiple different but adjacent voxels substantially simultaneously, or even simultaneously in separate voxels that are different but adjacent.

[0081] In such a multi-beam SLW system according to such embodiments within the scope of the present invention, by advantageously utilizing a novel form of beam control means, simultaneous but separate spatial control, i.e., simultaneous but separate control of beam deflection, of first and second independent photon beams propagating substantially parallel to each other along at least a portion of the optical propagation path to the substrate medium becomes possible. Thus, the practical SLW performance and usefulness of the system can be further improved compared to the single-beam embodiment version of the system.

[0082] Figure 5 schematically shows the main components of a second embodiment of the SLW apparatus according to the present invention. This is a two-beam SLW system and uses most of the same components as the system of the more general first embodiment in Figure 2, as indicated by the use of the same reference numerals throughout. In such a two-beam SLW recording, the principal photon beam B is split into two separate sub-beams B1 and B2 by a first acousto-optic deflector AOD1, and each sub-beam B1 and B2 then continues to propagate in a specified x-axis direction of the optical propagation path. In the drawing of Figure 5, the sub-beams B1 and B2 are shown to be angled with respect to each other, but it will be noticed that this is simply for clarity and illustrative purposes. In practice, the two sub-beams B1 and B2 are oriented substantially parallel (or nearly parallel; however, for practical purposes this means substantially parallel) with respect to each other, thereby both sub-beams B1 and B2 propagate substantially parallel to each other in a specified x-axis direction of the optical propagation path to the substrate medium. The partial beams B1 and B2 are then further deflected by the second acousto-optic deflector AOD2 as required in the specified y-axis direction of the optical propagation path, as shown in the enlarged left portion of Figure 5, where the directions of the partial beams B1 and B2 change from B1in and B2in to B1out and B2out. The two outgoing partial beams B1out and B2out, though substantially parallel, separate after passing through the first and second acousto-optic deflectors AOD1 and AOD2, and thus continue to propagate parallel to the substrate sample 100 along the optical propagation path through the remaining optical components of the system in the same manner as in the single-beam embodiment. Within the microscope objective lens OBJ1, both partial beams B1out and B2out are then finally focused, in the same manner as in the single-beam embodiment, to different but adjacent parts or regions within a given voxel (or adjacent voxel) of the substrate sample medium 100, as shown in the enlarged right portion of Figure 5.

[0083] Figure 6 schematically shows the main components of a third embodiment of the SLW apparatus according to the present invention, which is a four-beam SLW system. In such a four-beam system, the principal photon beam is first split into two separate partial beams B1 and B2 by the first acousto-optic deflector AOD1, and each partial beam B1 and B2 then continues to propagate in a specified x-axis direction of the optical propagation path. As in the diagram of Figure 5, the diagram of Figure 6 shows the partial beams B1 and B2 at angles to each other, but again it will be noted that this is merely for clarity and illustrative purposes. In this case as well, the two partial beams B1 and B2 are actually directed substantially parallel (or nearly parallel; however, for practical purposes this means substantially parallel) to each other, so that both partial beams B1 and B2 propagate substantially parallel to each other in a specified x-axis direction of the optical propagation path to the substrate medium. However, each of these partial beams B1 and B2 is further split by the second acousto-optic deflector AOD2 into two partial beams (forming a total of four partial beams B1out, B2out, B3out, and B4out) in a defined y-axis direction of the optical propagation path, as shown in the enlarged left portion of Figure 6 where partial beams B1in and B2in change to B1out, B2out, B3out, and B4out. Thus, the four outgoing partial beams B1out, B2out, B3out, and B4out are all substantially parallel but separate after passing through the first and second acousto-optic deflectors AOD1 and AOD2, and therefore continue to propagate parallel to the substrate sample 100 along the optical propagation path through the remaining optical components of the system in the same manner as in the single-beam embodiment. Similar to the two-beam embodiment in Figure 5, within the microscope objective lens OBJ1, the four partial beams B1out, B2out, B3out, and B4 are all ultimately focused, in the same conventional manner as in the single-beam embodiment system, onto different but adjacent parts or regions within a given voxel (or adjacent voxel) of the substrate sample medium 100, as shown in the enlarged right portion of Figure 6.

[0084] The multi-beam writing achievable in the two-beam SLW system of the second embodiment of the present invention and the four-beam SLW system of the third embodiment may be carried out by any of three different methods of designing and controlling the first and second acousto-optic deflectors AOD1 and AOD2, respectively. (i) The properties of the synthesized control signal applied to the AOD, (ii) Dynamic modification of control signals, (iii) A combination of (i) and (ii).

[0085] (i) Regarding the synthesis of control signals: Acousto-optic deflector (AOD) devices have a crystal as their main component, which is substantially transparent to a laser photon beam B. However, when a control signal is connected to the AOD device, acoustic waves are generated within the AOD crystal. These waves form an optical grating within the crystal, and as a result of passing through it, the photon beam B is diffracted. Such diffraction is of positive and negative diffraction orders. The diffracted beam required for use is selected by blocking out the unwanted diffraction orders.

[0086] Figure 7(a) shows the case where no electrical control signal is applied to the AOD crystal. In this case, when no electrical control is applied, the laser photon beam passes straight through the crystal, i.e., in the direction of the 0th order of diffraction.

[0087] On the other hand, Figure 7(b) shows the case when the control signal f1 is applied to the crystal of the AOD. As shown here, an electrical control signal of frequency f1 is applied to the input of the AOD device. The acoustic wave travels through the crystal, creating a lattice-like area within the crystal with regular dense and sparse areas. At this time, the laser photon beam travels through the crystal as if it were a volume lattice with areas of slightly different refractive indices. Therefore, the photon beam is split in several directions according to a standard diffraction formula. Next to the AOD is a slit (aperture). Only one split beam, for example, diffraction order +1 as shown here in Figure 7(b), passes through the aperture of this slit. Other diffraction orders, such as +2, +3, ..., etc., and 0, -1, -2, -3, ..., etc., are blocked by the slit.

[0088] The diffraction angle α1 is proportional to the lattice density, i.e., GD = 1 / λ1, which is proportional to the control signal frequency f1, i.e., α1 ~ 1 / λ1 ~ f1. Here, for example, in our prototype system, you might notice that the signal control frequency can be approximately 100 MHz (time period 10 ns). The propagation speed of acoustic waves is 650 m / s. Therefore, the spatial period of the lattice is approximately 6500 nm. For example, for the green λ, the diffraction angle, i.e., arc sinλ, is 532 nm, and therefore arc sin(532 / 6500) = 4.7 degrees. An increase in the control signal frequency suggests an increase in grid density (GD), which therefore results in a larger diffraction angle. Here, you might notice that in our prototype system, for example, the range of control signal frequencies is relatively small, for example, only a few percent of the frequency value. For example, ±1% of the nominal value of 100 MHz is a frequency range of 99–101 MHz.

[0089] Figure 7(c) shows the case where a control signal mixed from fundamental signals f1 and f2 is applied to the AOD crystal. As shown here, when the control signal is combined as a mixture (i.e., a bundle) of two (or more) frequencies, the laser photon beam is split into two (or more) directions simultaneously (but still at diffraction order +1). By appropriately selecting the fundamental signals f1 and f2, two separate beams can be generated. Thus, it is possible to control the direction of each single beam separately but simultaneously. In this way, it is possible to increase and control the number of simultaneous SLW writing beams, which is utilized in the design and operation of SLW systems in 2- and 4-beam embodiments within the scope of the present invention.

[0090] (ii) Regarding dynamic changes to control signals: Figure 8 illustrates the case where the control signal applied to the AOD crystal is dynamically changed. As shown here, if the control frequency is changed faster than the timing of acoustic wave propagation in the AOD crystal, it is possible to obtain different lattice areas in different parts of the AOD crystal. As a result, the laser photon beam is diffracted from different parts of the AOD crystal in different directions.

[0091] As shown in Figure 8, at time t1 there is no deflection, and therefore the laser photon beam passes straight through the AOD crystal. However, at time t2, a portion of the laser photon beam is deflected (i.e., the left half of the AOD crystal in the figure), and a portion of the laser beam passes straight through the AOD crystal without deflection (i.e., the right half of the AOD crystal in the figure), meaning there are two beams at the crystal's output. In this example, it can be assumed that the laser beam illuminates the entire width of the AOD crystal. Next, at time t3, as a result of having different lattice-like areas on the left and right sides of the AOD crystal, there are two laser photon beams deflected in different directions from the AOD crystal. Finally, at time t4, the deflection of the laser photon beam is limited to the right side of the AOD crystal, and in addition, a portion of the laser beam passes straight through the AOD crystal without deflection on the left side.

[0092] Therefore, the dynamic modification of the combined control signals applied to one or more acousto-optic deflectors can be used not only to control one or more cross-sections of the deflected beam, but also to control the size of the voxels being recorded / written, in conjunction with controlling the position of the voxels being recorded / written. For example, if the change in the control signal involves a frequency higher than the frequency used to deflect each laser beam, e.g., at least twice or more over time during the writing of a single voxel, a diffraction grating is generated within each acousto-optic modulator, which may be specific to the individual voxel being written. The laser signal is dispersed by these photons to form a wider beam. Since the parameters of such a grating can vary over time for each voxel being written, the size of each voxel being written can vary over time in the same way. This can be advantageous because it allows for the area writing rate to vary over time according to the parameters of the currently written details of the structure being written.

[0093] (iii) Regarding the combination of dynamic changes and control signal synthesis: As will be readily apparent to those skilled in the art from the above-mentioned descriptions of how each embodiment is to be implemented separately, theoretically, it is possible to combine the synthesis of control signals with the dynamic modification of control signals.

[0094] Throughout this description and claims, the words “comprise” and “contain” and their linguistic variations (e.g., “comprising” and “comprises”) mean “including, but not limited to,” and are not intended (and will not) exclude other parts, additives, ingredients, elements, completes, or steps.

[0095] Throughout the description and claims herein, unless expressly specified otherwise or the context requires otherwise, the singular form includes the plural form. More specifically, where the indefinite article is used, unless expressly specified otherwise or the context requires otherwise, the description should be understood to intend both the singular and plural forms.

[0096] Throughout this specification, any features, components, elements, wholes, properties, characteristics, compounds, chemical components, or groups described in connection with a particular aspect, embodiment, or example of the present invention should be understood to be applicable to any other aspect, embodiment, or example described herein, unless otherwise expressly stated, or unless incompatible.

[0097] Furthermore, it is expressly assumed in this disclosure that the various aspects, embodiments, examples, features and alternative forms described in the preceding paragraphs, claims, and / or the following description and accompanying drawings, in particular individual structural, constituent, or operational features, may be interpreted independently or in any number of such combinations. For example, individual features described in relation to a particular embodiment, or described alone or in combination with other features of one or more embodiments, may be applied in themselves or in combination with one or more other features to all embodiments, unless expressly otherwise specified or unless such features are incompatible, and may be found and used in combination with any other features of any embodiment.

Claims

1. A stereolithography writing apparatus for performing two-photon polymerization in a photopolymerizable substrate medium, An electromagnetic radiation source that emits a photon beam suitable for causing two-photon polymerization in the substrate medium, Means for defining the optical propagation path of the photon beam as the photon beam travels from the electromagnetic radiation source toward the substrate medium, The beam control means in the optical propagation path, which manipulates the photon beam to focus it into a selected target region of the substrate medium in which two-photon polymerization can occur, Means for moving the substrate medium with respect to the photon beam so as to sequentially expose different target regions of the substrate medium to the photon beam and sequentially cause two-photon polymerization in those different target regions of the substrate medium, Equipped with, The beam control means, At least one acousto-optic deflector that spatially controls the direction of the photon beam as it travels along the optical propagation path, At least one acousto-optic modulator modulates the intensity and / or frequency and / or cross-sectional parameters of the photon beam as it propagates along the optical path, Equipped with, A stereolithography writing device characterized by the following features.

2. A stereolithography writing device according to claim 1, The system is constructed and operable to be a multi-beam SLW system in order to perform writing by substantially simultaneously performing 2PP in multiple regions or parts within a given voxel or within adjacent but separate voxels in the substrate medium. A stereolithography writing device characterized by the following features.

3. A stereolithography writing device according to claim 2, It is designed and operational to be a two-beam or four-beam SLW system. A stereolithography writing device characterized by the following features.

4. A stereolithography writing device according to claim 3, The system is constructed and operable to be a two-beam system, and the beam control means, or at least one of the acousto-optic deflectors, is constructed and operable to perform simultaneous but separate spatial control of the deflection of first and second independent photon partial beams propagating substantially parallel to each other along at least a portion of the optical propagation path to the substrate medium. A stereolithography writing device characterized by the following features.

5. A stereolithography writing device according to claim 4, The beam control means comprises at least two acousto-optic deflectors, at least a first and a second acousto-optic deflector, wherein the first acousto-optic deflector is configured and operable to split the original photon beam into two separate sub-beams in the x-axis direction, The second acousto-optic deflector is configured and operable to deflect the divided partial beams together in the y-axis direction, arranging them substantially parallel to each other, thereby directing them in the desired final output direction for propagation to the substrate medium. A stereolithography writing device characterized by the following features.

6. A stereolithography writing device according to claim 3, The system is constructed and operable to be a four-beam system, and the beam control means, or at least one of its acousto-optic deflectors, is constructed and operable to perform simultaneous but separate spatial control of the deflection of first, second, third, and fourth independent photon partial beams propagating substantially parallel to one another along at least a portion of the optical propagation path to the substrate medium. A stereolithography writing device characterized by the following features.

7. A stereolithography writing device according to claim 6, The beam control means comprises at least two acousto-optic deflectors, specifically at least a first and a second acousto-optic deflector. The first acousto-optic deflector is configured and operable to split the original photon beam into two separate sub-beams in the x-axis direction. The second acousto-optic deflector is configured and operable to further divide each of the two partial beams into two partial beams in the y-axis direction (i.e., to form a total of four partial beams), and to arrange them substantially parallel to each other, thereby directing them in the desired final output direction for propagation to the substrate medium. A stereolithography writing device characterized by the following features.

8. A stereolithography writing device according to any one of claims 2 to 7, Each of the divisions and / or configurations of each of the beams or partial beams is (i), (ii), or (iii), namely, (i) The properties of the combined control signal applied to one or more of the at least one acousto-optic deflectors, (ii) Dynamic modification of a synthesized control signal applied to one or more of the at least one acousto-optic deflectors, (iii)(i) and (ii) combination, It can be implemented by either of the following: A stereolithography writing device characterized by the following features.

9. A stereolithography writing device according to claim 8, The dynamic modification of the combined control signal applied to one or more of the acousto-optic deflectors results in control of the cross-section of one or more of the deflected beams, as well as control of the size of one or each of the voxels (or at least one or more of them) that are recorded / written, along with control of the position of each voxel (or at least one or more of them) that are recorded / written. A stereolithography writing device characterized by the following features.

10. A stereolithography writing apparatus according to any one of claims 1 to 9, The beam control means, A plurality of acousto-optic deflector devices that spatially control the direction of the photon beam as it travels along the optical propagation path, A plurality of acousto-optic modulator devices that modulate the intensity and / or frequency and / or cross-sectional parameters of the photon beam as the photon beam propagates along the optical propagation path, A stereolithography writing device characterized by comprising the following:

11. A stereolithography writing apparatus according to any one of claims 1 to 10, The beam control means, including the one or more acousto-optic deflectors and the one or more acousto-optic modulators, forms part of the means for defining the optical propagation path, thereby ensuring that at least one acousto-optic deflector and at least one acousto-optic modulator are located within the optical propagation path. The photon beam interacts with both the at least one acousto-optic deflector and the at least one acousto-optic modulator as it travels along the optical propagation path. A stereolithography writing device characterized by the following features.

12. A stereolithography writing device according to any one of claims 1 to 11, The control of the photon beam by the one or more acousto-optic modulators by modulating the intensity and / or frequency of the photon beam is as follows: (i) The amplitude of the electromagnetic radiation that forms the beam, (ii) Cross-sectional shape of the beam, (iii) Timing of the radiation dose that can be propagated by the beam, (iv) The frequency (or wavelength) of the electromagnetic radiation that forms the beam, This includes controlling the photon beam by modulating any one or more of the photons by an acoustic-optical effect. A stereolithography writing device characterized by the following features.

13. A stereolithography writing apparatus according to any one of claims 1 to 12, At least one acousto-optic modulator, or at least one of a plurality of acousto-optic modulators, which form part of the beam control means, is of the "high-speed" type. A stereolithography writing device characterized by the following features.

14. A stereolithography writing apparatus according to claim 13, There are multiple acousto-optic modulators, of which at least one other acousto-optic modulator, apart from the at least one "high-speed" acousto-optic modulator, is of the "low-speed" (or "normal" / "standard") type. A stereolithography writing device characterized by the following features.

15. A stereolithography writing device according to any one of claims 1 to 14, At least one acousto-optic deflector, or at least one of a plurality of acousto-optic deflectors, which form part of the beam control means, is of the "low-speed" type. A stereolithography writing device characterized by the following features.

16. A stereolithography writing apparatus according to any one of claims 1 to 15, There are multiple acousto-optic deflectors, at least two of which are oriented, positioned, or tilted so that their respective reference planes are at a 90-degree angle, i.e., perpendicular to each other, so that these multiple acousto-optic deflectors can function to independently deflect the photon beam in each of the two orthogonal axial directions. A stereolithography writing device characterized by the following features.

17. A stereolithography writing apparatus according to any one of claims 1 to 16, The means for defining the optical propagation path, or one or more parts of the defining means other than the at least one acousto-optic deflector and the at least one acousto-optic modulator, comprises any number and any type of optical components that are either optically transparent or optically reflective, so that together they form or define the overall path of the propagation or progression of the photon beam emitted by the radiation source and traveling toward the substrate medium, The optical component, which is either optically transparent or optically reflective, includes one or more mirrors for reflecting the photon beam in a desired modified direction of propagation, and / or one or more delay plates for changing the polarization of the photon beam passing through its interior. A stereolithography writing device characterized by the following features.

18. A method for producing an object or structure by the principle of two-photon polymerization in a photopolymerizable substrate medium, (i) Providing a stereolithography writing device according to any one of claims 1 to 17, (ii) Emitting a photon beam from the electromagnetic radiation source, operating the apparatus to propagate the beam along the optical propagation path toward the substrate medium, controlling the photon beam by manipulating it to focus it on a selected target region of the substrate medium so that two-photon polymerization occurs in the substrate medium, and moving the substrate medium relative to the photon beam so that different target regions of the substrate medium are sequentially exposed to the photon beam and two-photon polymerization sequentially occurs in those different target regions of the substrate medium, Includes, Controlling the aforementioned photon beam is The action of the at least one acousto-optic deflector spatially controls the direction of the photon beam as it travels along the optical propagation path, The action of at least one acousto-optic modulator modulates the intensity and / or frequency and / or cross-sectional parameters of the photon beam as it propagates along the optical path, including, A method characterized by the following:

19. The method according to claim 18, The operation of one or more of the acousto-optic deflectors and / or acousto-optic modulators includes causing a dynamic change in the combined control signals applied to one or more of them, The dynamic modification of the control signal results in control of the cross-section of one or more beams of the deflected beam, as well as control of the size of the one or each of the voxels (or at least one or more of them) that are recorded / written, along with control of the position of the one or each of them that are recorded / written. A method characterized by the following:

20. The method according to claim 18 or claim 19, This is a method for fabricating three-dimensional objects or structures using the principle of two-photon polymerization in a voluminous, photopolymerizable substrate medium. A method characterized by the following:

21. An object or structure characterized by being formed by the principle of two-photon polymerization in a photopolymerizable substrate medium using a stereolithography writing apparatus according to any one of claims 1 to 17 or the method according to any one of claims 18 to 20.

22. The object or structure according to claim 21, characterized in that it is a three-dimensional object or structure.

23. A control system for controlling a photon beam emitted by an electromagnetic radiation source of a stereolithography writing apparatus that performs two-photon polymerization in a photopolymerizable substrate medium, wherein the control system is provided in the optical propagation path of the photon beam as it travels from the electromagnetic radiation source toward the substrate medium, and the control system is constructed and operable to manipulate the photon beam to focus it within a selected target region of the substrate medium in which the two-photon polymerization can occur. The control system, At least one acousto-optic deflector that spatially controls the direction of the photon beam as it travels along the optical propagation path, At least one acousto-optic modulator modulates the intensity and / or frequency and / or cross-sectional parameters of the photon beam as it propagates along the optical path, The beam control means includes, A control system characterized by the following:

24. A control system according to claim 23, The apparatus is a stereolithography writing apparatus having a function including the beam control means as defined in any one of claims 1 to 17. A control system characterized by the following:

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