Monolithic semiconductor-based optically addressable light valves.

Abstract

A monolithic transmissive or reflective light valve system capable of withstanding operation with high optical flux and high average power lasers is described. The light valve includes a liquid crystal layer in contact with an alignment layer, which is a first epitaxially doped semiconducting transparent electrode in contact with a photoconductor layer made of a first wide bandgap or ultra-wide bandgap semi-insulating semiconductor layer (or wafer). A second epitaxial semiconducting transparent electrode layer brackets the light valve and includes a second wide bandgap or ultra-wide bandgap semi-insulating or conducting semiconductor layer (wafer). In some embodiments, the doped epitaxial or ion-implanted transparent electrode and photoconductor layer have matching coefficients of thermal expansion (CTE) and a further matching CTE to the second wide bandgap material that brackets the light valve. In some embodiments, the transparent electrode and photoconductor layer have matching refractive indices along with matching optical excitation levels.

Description

[Technical Field]

[0001] [Related Applications] This disclosure is part of a non-provisional patent application claiming the benefit of priority to U.S. Patent Application No. 63 / 422,571, filed November 4, 2022, which is incorporated herein by reference in its entirety.

[0002] [Technical field] FIELD OF THE DISCLOSURE The present disclosure relates generally to systems and methods for high throughput laser manufacturing. In one embodiment, laser manufacturing is enabled by the use of spatial light modulators that include semiconductor-based high power transmission or reflection light valves. [Background technology]

[0003] A spatial light modulator applies some form of spatially varying modulation to a beam of light. SLMs typically modulate the intensity of the light beam, but it is also possible to fabricate devices that modulate the polarization or phase of the beam, or both the intensity and phase simultaneously.

[0004] The images produced by electrically addressed spatial light modulators can be created and modified electronically, as in most electronic displays. Light modulators can be used to fully or partially intercept, redirect, or modulate laser light. For example, spatial light modulators (SLMs), also known as light valves (LVs), are a type of light modulator that can be used to impart information uniformly across a beam (1D modulation), to impart variation across a beam to form parallelized light channels (2D modulation), or to impart variation across a volume of pixel / voxel channels (3D modulation). The information imparted can be in the form of amplitude, phase, polarization, wavelength, coherence, or quantum entanglement.

[0005] Industrial applications of LV may require that the LV be able to withstand high fluence and high energy laser sources for extended periods of time. This allows for manufacturing complex assembly or processing cycles with typical shot counts ranging from tens of millions to billions (where printing a 2D area is equivalent to one frame removed from the LV to the print bed). LV lifetime requirements for typical industrial systems are greater than 10E6 shots, and ideally greater than 10E9 shots. The required light source intensity to print materials in a reasonable time is 8 J / cm at the print surface, including kW levels of average optical power. 2 While various methods can be used to reduce the fluence at the LV, in commercially viable industrial processes, the energy density at the LV can exceed 2 J / cm. 2 Existing LVs fail well below this fluence and power level, making their use in metal AM systems impractical.

[0006] Typically, the elements that fail (or contribute to failure) in a typical LV are the transparent conductive electrode (TCE), alignment layer, liquid crystal layer (linear electro-optic (LEO) material), and photoconductor layer. To avoid material failure, improved light valves and light valve materials are needed that can meet the requirements for high-speed industrial manufacturing. Summary of the Invention

[0007] In some embodiments, the transmissive light valve system includes a liquid crystal layer and a first transparent electrode layer in contact with a photoconductor semi-insulating semiconductor layer or in contact with a photoconductor in the form of a wafer substrate. A second wide bandgap or ultra-wide bandgap semiconductor layer and a second transparent electrode layer comprising a second semiconducting transparent conductive electrode are positioned to bracket or sandwich the liquid crystal and alignment layer. In some embodiments, one or more of the photoconductor layer or wafer and electrode layers are selected to be matched in CTE.

[0008] In some embodiments, first and second wide bandgap (having a bandgap greater than 3 eV) or ultra-wide bandgap semiconductor layers (having a bandgap greater than 4 eV) may be used.

[0009] In some embodiments, the first or second wide bandgap or ultra-wide bandgap semiconductor layer comprises at least one of a gallium nitride (GaN) intrinsic semi-insulating layer, an iron (Fe) doped GaN semi-insulating layer, a carbon (C) doped GaN semi-insulating layer, a manganese (Mg) doped semi-insulating layer, and a vanadium (V) doped silicon carbide (SiC) semi-insulating layer or any other type of doping compensated or intrinsic semi-insulating layer or wafer.

[0010] In some embodiments, the first and second transparent conductive electrodes comprise at least one of n- or p-epitaxially (epi-) doped epi GaN, epi SiC, epi GaO, epi diamond, epi aluminum nitride (AlN), or other epitaxially grown wide or ultra-wide bandgap semiconductors, or alternatively, a semi-insulating semiconductor with ion-implanted dopants to form a conductive transparent layer, or by simply using a doped conductive semiconductor wafer that functions as both the transparent conductive electrodes and the substrate supporting the LV device.

[0011] In some embodiments, a first alignment layer may be positioned between a first transparent conductive electrode and the liquid crystal, and a second alignment layer may be positioned between a second transparent conductive electrode that holds the liquid crystal together.

[0012] In some embodiments, at least one of the first and second alignment layers comprises an inorganic layer grown or deposited on the substrate.

[0013] In some embodiments, the liquid crystal layer, the first and second transparent electrodes, the photoconductor layer, and the first and second alignment layers together form a monolithic stack of the same matrix material or crystallographically matched epitaxial layers of another material.

[0014] In some embodiments, at least one anti-reflective (AR) coating is positioned in contact with at least one of the first and second transparent electrode photoconductor layers and the first and second alignment layers, and includes a high refractive index layer and a low refractive index layer, which together form a monolithic stack when formed by tailoring the dopant profile in each individual layer in the multiple layers that form the anti-reflective coating design.

[0015] In some embodiments, the light valve has a luminous efficiency of 2 Joules / cm 2 Operates at energy fluxes exceeding the energy flux and / or average powers in the kilowatt range.

[0016] In some embodiments, the monolithic transmissive light valve system includes a liquid crystal layer positioned between a first transparent electrode and photoconductor layer including a first wide bandgap or ultra-wide bandgap semiconductor layer and a first transparent conductive electrode, and a second transparent electrode layer including a second wide bandgap or ultra-wide bandgap semiconductor layer and a second transparent conductive electrode. In some embodiments, multiple alignment layers and anti-reflective layers can be monolithically formed in contact with at least one of the first transparent electrode and photoconductor layer, the first transparent conductive electrode, the second transparent electrode photoconductor layer, and the second transparent conductive electrode.

[0017] In some embodiments, a process for fabricating a transmissive light valve system includes providing a liquid crystal layer and positioning a first transparent electrode including a first wide bandgap or ultrawide bandgap semiconductor layer and a first photoconductor layer in contact with the liquid crystal layer. A second transparent electrode layer in contact with a second wide bandgap or ultrawide bandgap semiconductor layer is also positioned in contact with an alignment layer that supports the liquid crystal layer. Alternatively, a second transparent conductive electrode that also functions as a substrate is in contact with the alignment layer that supports the liquid crystal.

[0018] In some embodiments, a reflective light valve system includes a transparent electrode in contact with a photoconductor layer or a photoconductor wafer including a first wide or ultra wide bandgap semi-insulating semiconductor and a light-reflective layer in contact with the photoconductor. The system further includes a transparent conductive electrode with an alignment layer positioned between the reflective layer and the transparent conductive electrode and a liquid crystal layer or another transparent conductive in contact with the photoconductor layer or photoconductor wafer including a second wide or ultra wide bandgap semi-insulating semiconductor substrate. [Brief explanation of the drawings]

[0019] Non-limiting and non-exhaustive embodiments of the present disclosure are described with reference to the following figures, in which like numerals refer to like parts throughout the various views unless otherwise noted: [Figure 1A] 1 illustrates a monolithic transmissive light valve that can be used in an additive manufacturing system. [Figure 1B] 1 illustrates a monolithic reflective light valve that can be used in an additive manufacturing system. [Figure 2A] 1 illustrates one embodiment of a monolithic transmissive light valve. [Figure 2B] 1 illustrates one embodiment of a monolithic transmissive light valve comprising an iron-doped Fe—GaN semi-insulating wafer. [Figure 3] 1 illustrates an additive manufacturing system capable of providing a one-dimensional or two-dimensional beam to a cartridge. [Figure 4]1 illustrates a method of operating a cartridge-based additive manufacturing system capable of providing a one-dimensional or two-dimensional beam to a cartridge. [Figure 5] 1 illustrates one embodiment of an additive manufacturing system including a light valve based on phase-change addressing and / or modulation layers and a switchyard system that enables patterned two-dimensional energy recycling. DETAILED DESCRIPTION OF THE INVENTION

[0020] In the following description, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific exemplary embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the concepts disclosed herein, it being understood that modifications may be made to the various disclosed embodiments and other embodiments may be utilized without departing from the scope of the present disclosure. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0021] Figure 1A shows the use in additive manufacturing systems, or 2 Joules / cm 2 , kilowatt-level power, large area (cm 21 illustrates one embodiment of a monolithic, high-power capable transmissive light valve suitable for use at energy densities exceeding tens of joules over a range of 100 Hz to 100 Hz, and in other applications that benefit from a long service life of the light valve. In one embodiment, the monolithic transmissive light valve system 100A includes a liquid crystal layer 104A. The liquid crystal layer 104A is positioned between first and second optical patterning layers 102A(i) and 102A(ii). The liquid crystal layer 104A and the first and second optical patterning layers 102A(i) and 102A(ii) may be combined to form a monolithic block with matched CTEs and refractive indices within and between the layers that hold the liquid crystal layer 104A together, preventing peeling or layer separation. In some embodiments, the first and second optical patterning layers 102A(i) and 102A(ii) may have their respective coefficients of thermal expansion matched to within 10%, 5%, or 1% of each other. Additionally, the first and second optical patterning layers 102A(i) and 102A(ii) may have CTEs that are matched to within 10%, 5%, or 1% of each other and of the liquid crystal layer 104A. Advantageously, a well-matched CTE promotes uniform expansion of the monolithic transmissive light valve system 100A when heated with a laser, while the use of identical, largely transparent materials for each layer results in balanced optical absorption between the layers and heating, such that the bottom and top layers experience the same temperature rise, minimizing thermomechanical strain and stress cycling, fatigue, and damage, extending the useful life of the device.

[0022] In some embodiments, the first optically patterned layer 102A(i) may be formed from a first transparent electrode on the top surface of the first wide bandgap or ultra wide bandgap semiconductor layer. Similarly, the second optically patterned layer 102A(ii) may be formed from a second transparent electrode layer that includes a second wide bandgap semiconductor layer. In some embodiments, multiple alignment layers and anti-reflective layers may be monolithically formed on at least one of the first transparent electrode semiconductor and first photoconductor semiconductor layer, the second semiconductor photoconductor layer, and the second semiconducting transparent conductive electrode.

[0023] In operation, laser light 101A(i) creates a spatial pattern that, in combination with a polarizer, selectively blocks or transmits laser light passing through laser light valve system 100A. High fluence, high power, and high energy input light 101A(ii) is directed through laser light valve system 100A and becomes spatially patterned output light 101A(iii). This light can be directed to heat a powder bed suitable for additive manufacturing, as described below in connection with Figures 3, 4, and 5.

[0024] Figure 1B shows the additive manufacturing system used or 2 Joules / cm 2FIG. 1 illustrates one embodiment of a monolithic, high-flux, high-power, high-energy reflective light valve suitable for use in applications that benefit from a long light valve service life when used at energy densities above 102B. In one embodiment, the monolithic reflective light valve system 100B includes a liquid crystal layer 104B. The liquid crystal layer 104B is positioned between first and second optical patterning layers 102B(i) and 102B(ii). The liquid crystal layer 104B and the first and second optical patterning layers 102B(i) and 102B(ii) may be combined to form a monolithic block with matched CTEs and refractive indices within and between the layers that hold the liquid crystal layer 104B together, preventing peeling or layer separation. In some embodiments, the first and second optical patterning layers 102B(i) and 102B(ii) may have their respective coefficients of thermal expansion matched to within 10%, 5%, or 1% of each other. Furthermore, the first and second optical patterning layers 102B(i) and 102B(ii) may have their CTEs matched to within 10%, 5%, or 1% of each other and of the liquid crystal layer 104A. Advantageously, a well-matched CTE promotes uniform expansion of the monolithic transmissive light valve system 100B when heated with a laser, while the use of identical, largely transparent materials for each layer results in balanced optical absorption between layers and heating, with the bottom and top layers experiencing the same temperature rise, minimizing thermomechanical strain and stress cycling, fatigue, and damage, thereby extending service life. Furthermore, the level of photoinduced semiconductor excitation in the photoconductor layer can also be balanced or well matched to within less than 1 percent, resulting in a more tightly constrained electric field applied to the liquid crystal from top to bottom, which can increase the spatial resolution of the patterning.

[0025] In some embodiments, the first photo-patterning layer 102B(i) may be formed from a first transparent electrode semiconductor layer including a first wide bandgap or ultra-wide bandgap photoconductor semiconductor and a reflective layer (e.g., a dielectric mirror or a doped semiconductor multilayer). The second photo-patterning layer 102B(ii) may be formed from a second semiconductor transparent electrode layer and a wide bandgap or ultra-wide bandgap photoconductor semiconductor layer. In some embodiments, multiple alignment layers and anti-reflective layers may be monolithically formed on at least one of the first transparent electrode and photoconductor layer, the first transparent conductive electrode, the second transparent electrode and photoconductor layer, and the second transparent conductive electrode.

[0026] In operation, laser light 101B(i) creates a spatial pattern that selectively blocks or transmits laser light that reflects through laser light valve system 100B. High fluence, high power, and high energy input light 101B(ii) is directed to pass into laser light valve system 100B, where it is spatially patterned and reflected into output light 101B(iii). This light can be directed to heat a powder bed suitable for additive manufacturing, as described below in connection with Figures 3, 4, and 5.

[0027] FIG. 2A illustrates one embodiment of a monolithic, high-flux, high-power, high-energy transmissive light valve 200A that includes optical patterning layer stacks 202(i) and 202(ii) that bracket or sandwich a liquid crystal 204. From top to bottom, layer 206 is an antireflection (AR) layer, layer 208 is an n-type conductive semiconductor fabricated, for example, by ion implantation, physical vapor deposition, or epitaxial growth, and layer 210 is a photoconductive, semi-insulating (SI) semiconductor. The semi-insulating semiconductor can be intrinsic or non-intrinsic (doped, compensated). Another antireflection layer 212 is stacked on alignment layer 214. The alignment layer 214 is grown or deposited on the 5 μm thick liquid crystal layer 204 to complete the optical patterning stack 202(i). Below the liquid crystal layer 204 is a second optically patterned layer stack 202(ii) that includes an alignment layer 216 stacked on an anti-reflection layer 218. Following layer 210 in the stack is a layer 220 formed from a semi-insulating (SI) semiconductor and a layer 222 formed from an n-type transparent conductive semiconductor. The second optically patterned layer stack 202(ii) is completed by an anti-reflection layer 224.

[0028] In operation, address ("write") laser light 201B(I) creates a spatial pattern that selectively blocks, transmits, or partially transmits ("grayscaling") "read" laser light passing through light valve system 200A. High fluence, high power, and high energy input read light 201A(ii) is directed through laser light valve system 200A and becomes spatially patterned and transmitted, resulting in spatially patterned output light 201A(iii). This light can be directed to heat a powder printing bed 234 suitable for additive manufacturing, as described below in connection with Figures 3, 4, and 5.

[0029] Figure 2B illustrates another embodiment of a monolithic, high-flux transmissive light valve 200B similar to that described above with respect to Figure 2A. However, in contrast to the embodiment of Figure 2A, which illustrates semi-insulating (SI) semiconductor layers 210 and 220, Figure 2B uses an iron (Fe)-doped, compensated Fe-GaN semi-insulating (SI) wafer. In Figure 2B, an epitaxially grown n-epi GaN layer provides the transparent electrode.

[0030] In the embodiment shown with respect to FIG. 3, the additive manufacturing system may be represented by various modules that form the additive manufacturing method and system 300. As seen in FIG. 3, the laser source and amplifier 312 may be fabricated as a continuous or pulsed laser. In other embodiments, the laser source includes a pulsed electrical signal source, such as an arbitrary waveform generator or equivalent that operates on a continuous laser source, such as a laser diode. In some embodiments, this may also be achieved via a fiber laser source or a fiber launched laser source that is subsequently modulated by an acousto-optic or electro-optic modulator. In some embodiments, a high repetition rate pulse source using a Pockels cell may be used to create pulse trains of any length.

[0031] Possible laser types include, but are not limited to, gas lasers, chemical lasers, dye lasers, metal vapor lasers, solid-state lasers (e.g., fiber), semiconductor (e.g., diode) lasers, free electron lasers, gas dynamic lasers, "nickel-like" samarium lasers, Raman lasers, or nuclear-pumped lasers.

[0032] Gas lasers may include lasers such as helium-neon lasers, argon lasers, krypton lasers, xenon ion lasers, nitrogen lasers, carbon dioxide lasers, carbon monoxide lasers, or excimer lasers.

[0033] Chemical lasers may include lasers such as hydrogen fluoride lasers, deuterium fluoride lasers, COIL (chemoenzymatic iodine lasers), or Agil (all vapor phase iodine lasers).

[0034] Metal vapor lasers can include lasers such as helium-cadmium (HeCd) metal vapor lasers, helium-mercury (HeHg) metal vapor lasers, helium-selenium (HeSe) metal vapor lasers, helium-silver (HeAg) metal vapor lasers, strontium vapor lasers, neon-copper (NeCu) metal vapor lasers, copper vapor lasers, gold vapor lasers, manganese (Mn / MnCl) vapor lasers, etc. Rubidium or other alkali metal vapor lasers can also be used. Solid-state lasers include ruby ​​lasers, Nd:YAG lasers, NdCrYAG lasers, Er:YAG lasers, neodymium YLF (Nd:YLF) solid-state lasers, neodymium-doped yttrium orthovanadate (Nd:YVO4) lasers, neodymium-doped yttrium calcium oxoborate Nd:YCa4O(BO3)3 or simply Nd:YCOB, neodymium-glass (Nd:glass) lasers, titanium sapphire (Ti:sapphire) lasers, thulium YAG (Tm:YAG) lasers, yttrium YAG (Yb:YAG) lasers, yttrium:2O3 (glass or ceramic) lasers, yttrium-doped glass lasers (rod, plate / The lasers may include lasers such as fluorine-doped uranium (Ce:YAG) lasers, chromium ZnSe (Cr:ZnSe) lasers, cerium-doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), promethium-147 doped phosphate glass (147Pm+3:glass) solid-state lasers, chromium-doped chrysoberyl (alexandrite) lasers, erbium-doped erbium-yttrium co-doped glass lasers, trivalent uranium-doped calcium fluoride (U:CaF2) solid-state lasers, divalent samarium-doped calcium fluoride (Sm:CaF2) lasers, or F-center lasers.

[0035] The semiconductor laser may include laser media such as GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, GaInP, InGaAs, InGaAsO, GaInAsSb, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, or combinations thereof.

[0036] As shown in FIG. 3 , additive manufacturing system 300 uses a laser capable of providing controlled and directed energy in one or two dimensions as part of energy patterning system 310. In some embodiments, one-dimensional patterning can be directed as straight or curved strips, as rastered lines, as spiral lines, or in other suitable configurations. Two-dimensional patterning can include separated or overlapping tiles or images with varying laser intensity. Two-dimensional image patterns with non-rectangular boundaries can be used, overlapping or interpenetrating images can be used, and images can be provided by two or more energy patterning systems. Energy patterning system 310 uses a laser source and amplifier 312 to direct one or more continuous or intermittent energy beams to beam shaping optics 314. After shaping, if necessary, the beam is patterned by energy patterning unit 316, typically with some energy directed to waste energy processing unit 318. The patterned energy is relayed by image relay 320 to article processing unit 340, in one embodiment as a two-dimensional image 322 focused near floor 346. Article processing unit 340 may include a cartridge as described above. Article processing unit 340 has a plate or floor 346 (with walls 348) that together form an enclosed cartridge chamber containing material 344 (e.g., metal powder) to be dispensed by a powder hopper or other material dispenser 342. The dispensed powder may be created or recycled as described in this disclosure. The patterned energy directed by image relay 320 may melt, melt, sinter, fuse, change crystal structure, affect stress patterns, or otherwise chemically or physically modify the dispensed, dispersed material 344 to form a structure with desired properties.Control processor 350 may be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate the operation of laser source and amplifier 312, beam shaping optics 314, laser patterning unit 316, and image relay 320, as well as any other components of system 300. As will be understood, connections may be wired or wireless, may be continuous or intermittent, and may have feedback capability (e.g., thermal heating may be adjusted in response to a sensed temperature).

[0037] In some embodiments, the beam shaping optics 314 may include a variety of imaging optics to combine, focus, diverge, reflect, refract, homogenize, intensity adjust, frequency adjust, or otherwise shape one or more laser beams received from the laser source and amplifier 312 and direct them toward the laser patterning unit 316. In one embodiment, multiple beams of light, each having a different wavelength of light, may be combined using wavelength-selective mirrors (e.g., dichroic) or diffractive elements. In other embodiments, multiple beams may be homogenized or combined using polygonal mirrors, microlenses, and refractive or diffractive optical elements.

[0038] The laser patterning unit 316 may include a monolithic light valve as described with reference to FIGS. 1A and 1B. The laser patterning unit 316 may further include static or dynamic energy patterning elements. For example, the laser beam may be interrupted by a mask with fixed or movable elements. Pixel-addressable masking, image generation, or transmission may be used for greater flexibility and ease of image patterning. In some embodiments, the laser patterning unit includes an addressable light valve as described with reference to FIGS. 1A and 1B alone or in combination with other patterning mechanisms to provide patterning. The light valve may be transmissive, reflective, or may use a combination of transmissive and reflective elements. The pattern may be dynamically changed using electrical or optical addressing. In one embodiment, a transmissive optically addressed light valve acts to rotate the polarization of light passing through the valve, with optically addressed pixels forming a pattern defined by an optical projection source. In another embodiment, a reflective optically addressed light valve includes a write beam to modify the polarization of a read beam. In some embodiments, non-optically addressed light valves may be used, which may include, but are not limited to, electrically addressable pixel elements, movable mirror or micromirror systems, piezoelectric or micro-actuated optical systems, fixed or movable masks or shielding plates, or other conventional systems capable of providing high intensity patterning.

[0039] The waste energy processing unit 318 can be used to dissipate, redirect, and utilize energy that was not patterned and passed through the image relay 320. In one embodiment, the waste energy processing unit 318 can include passive or active cooling elements to remove heat from both the laser source and amplifier 312 and the laser patterning unit 316. In other embodiments, the waste energy processing unit can include a "beam dump" to absorb and convert to heat any beam energy not used to define the laser pattern. In yet other embodiments, the wasted laser beam energy can be recycled using the beam shaping optics 314. Alternatively or additionally, the wasted beam energy can be directed to the article processing unit 340 for heating or further patterning. In some embodiments, the wasted beam energy can be directed to an additional energy patterning system or article processing unit.

[0040] In one embodiment, a "switchyard" type optical system may be used. The switchyard system is suitable for reducing light wasted in additive manufacturing systems due to unwanted light waste caused by the pattern to be printed. The switchyard involves redirecting a complex pattern from its generation (in this case, a plane where a spatial pattern is imparted to a structured or unstructured beam) to its transmission through a series of switch points. Each switch point may optionally modify the spatial profile of the incident beam. The switchyard optical system may be utilized in, for example, but not limited to, laser-based additive manufacturing techniques where a mask is applied to the light. Advantageously, in various embodiments of the present disclosure, wasted energy may be recycled in a homogenized form or as patterned light, which can be used to maintain high power efficiency or high throughput. Furthermore, wasted energy may be recycled and reused to increase intensity for printing more challenging materials.

[0041] Image relay 320 may receive the patterned image (whether one-dimensional or two-dimensional) from laser patterning unit 316 directly or through a switchyard and direct it toward article processing unit 340. In a manner similar to beam shaping optics 314, image relay 320 may include optics to combine, focus, split, reflect, refract, adjust intensity, adjust frequency, or otherwise shape and direct the patterned light. The patterned light may be directed using moveable mirrors, prisms, diffractive optical elements, or solid-state optical systems that do not require substantial physical movement. One of the lens assemblies may be configured to provide incident light having the magnification at both the first set of optical lenses and the second set of optical lenses, and at the second set of optical lenses that are interchangeable from the lens assemblies. Rotation of one or more sets of mirrors mounted on a compensating gantry and a final mirror mounted on the build platform gantry can be used to direct the light from the leading mirror to the desired location. Translational movement of the compensating gantry and the build platform gantry can also ensure that the distance of the incident light from the leading mirror to the article handling unit 340 is substantially equal to the image distance. In practice, this allows for rapid change of the optical beam transmission size and intensity across the build zone location for different powder materials while still ensuring high system availability.

[0042] A material dispenser 342 (e.g., a powder hopper) within the article processing unit 340 (e.g., a cartridge) can disperse, remove, or mix materials, provide gradations or variations in material type or particle size, or adjust the thickness of a material layer. Materials can include metals, ceramics, glasses, polymer powders, other dissolvable materials capable of undergoing a heat-induced phase change from solid to liquid and vice versa, or combinations thereof. Materials can also include composites of dissolvable and non-dissolvable materials, where either or both components can be selectively targeted by an imaging relay system to dissolve the dissolvable component while leaving the non-dissolvable material intact or causing it to volatilize, destroy, burn, or undergo other destructive processes. In certain embodiments, slurries, sprays, coatings, wires, strips, or sheets of material can be used. Unwanted materials can be removed by using a blower, a vacuum system, sweeping, vibrating, shaking, tilting, or inverting the floor 346 for disposal or recycling.

[0043] In addition to material processing components, the article processing unit 340 may include components for holding and supporting the 3D structure, mechanisms for heating or cooling the chamber, alternative or auxiliary optical systems, and sensors and controls for monitoring or adjusting material or environmental conditions. The article processing unit may, in whole or in part, support a vacuum or inert gas atmosphere to reduce unwanted chemical interactions and reduce the risk of fire or explosion (especially with reactive metals). In some embodiments, the article processing unit may support an inert gas atmosphere such as Ar, He, Ne, Kr, Xe, CO2, N2, O2, SF6, CH4, CO, N2O, C2H2, C2H4, C2H6, C3H6, C3H8, i-C4H10, C4H10, 1-C4H8, cic-2, C4H7, 1,3-C4H6, 1,2-C4H6, C5H12, n-C5H12, i-C5H12, n- Various pure or mixtures of other atmospheres may be used, such as atmospheres containing C6H14, C2H3Cl, C7H16, C8H18, C10H22, C11H24, C12H26, C13H28, C14H30, C15H32, C16H34, C6H6, C6H5-CH3, C8H10, C2H5OH, CH3OH, iC4H8. In some embodiments, refrigerants or large, inert molecules (including, but not limited to, sulfur hexafluoride) may be used. An enclosure atmospheric composition that will have at least about 1% helium by volume (or number density) in addition to a selected proportion of inert / non-reactive gases may be used.

[0044] In some embodiments, multiple article processing units, cartridges, or build chambers, each having a build platform for holding a powder bed, can be used with multiple opto-mechanical assemblies arranged to receive and direct one or more incident energy beams into the cartridges, allowing for the simultaneous printing of one or more print jobs.

[0045] In another embodiment, one or more article processing units, cartridges, or build chambers can have cartridges maintained at a fixed height, with the optics vertically movable. The distance between the last optic of the lens assembly and the top surface of the powder bed can be maintained essentially constant by maintaining the build platform at a fixed height and moving the last optic upward a distance equivalent to the thickness of the powder layer. Advantageously, compared to vertically moving the build platform, large, heavy objects can be easily manufactured because the constantly changing mass of the build platform does not require micron-accurate movement. Typically, build chambers for metal powders with volumes greater than 0.1 to 0.2 square meters (i.e., greater than 100 to 200 liters or weights greater than 500 to 1000 kilograms) benefit the most from maintaining the build platform at a fixed height.

[0046] In one embodiment, a portion of the powder bed layer of the cartridge can be selectively melted or fused to form one or more temporary walls from the fused portion of the powder bed layer to contain another portion of the powder bed layer on the build platform. In selected embodiments, fluid passages can be formed in the one or more first walls to allow for improved thermal management.

[0047] In some embodiments, the additive manufacturing system can include an article handling unit or cartridge that supports a powder bed that can be tilted, inverted, and vibrated to substantially separate the powder bed from the build platform in a hopper. The powder material that forms the powder bed can be collected in the hopper for reuse in subsequent print jobs. The powder collection process can be automated, and also uses vacuum or gas injection systems to assist in powder removal or removal.

[0048] In some embodiments, an additive manufacturing system can be configured to easily process parts longer than the available build chamber or cartridge. A continuous (long) part can advance sequentially longitudinally from a first zone to a second zone. In the first zone, selected particles of granular material can be fused. In the second zone, unfused particles of granular material can be removed. A first portion of the continuous part can advance from the second zone to a third zone, while a final portion of the continuous part is formed in the first zone, and the first portion is maintained in the same lateral and transverse position occupied by the first portion in the first and second zones. Indeed, additive manufacturing and cleaning (e.g., separation and / or reclamation of unused or unfused granular material) can be performed in parallel (i.e., simultaneously) at different locations or zones on the part conveyor without the need to stop for removal of granular material and / or parts.

[0049] In another embodiment, additive manufacturing capabilities may be enhanced through the use of an enclosure that limits the exchange of gas between the interior of the enclosure and the exterior of the enclosure. An airtight chamber provides an interface between the interior and exterior, the interior having multiple additive manufacturing chambers, including an additive manufacturing chamber that allows for the melting of a powder bed. A gas management system maintains gaseous oxygen within the interior below a critical oxygen concentration, increasing the flexibility of the types of powders and processes that can be used within the system.

[0050] In another manufacturing embodiment, capacity can be increased by having an article processing unit, cartridge, or build chamber within the enclosure, where the build chamber can produce parts weighing over 2000 kilograms. A gas management system can maintain gaseous oxygen within the enclosure at concentrations below atmospheric levels. In some embodiments, parts can be transported by vehicle from inside the enclosure to a location outside both the enclosure and the airtight chamber, as the airtight chamber acts as a buffer between the gaseous environment within the enclosure and the gaseous environment outside the enclosure.

[0051] In another manufacturing embodiment, real-time powder sample collection from the powder bed is performed. A suction system is used for in-process collection and characterization of powder samples. The collection can be performed periodically, and the results of the characterization can result in adjustments to the powder bed fusion process. The suction system can optionally be used for one or more audits, process adjustments, or actions, such as changing printer parameters or verifying proper use of certified powder materials.

[0052] Yet another improvement to additive manufacturing processes can be provided and described by the use of manipulation devices such as cranes, lifting gantries, robotic arms, or the like that allow manipulation of parts that are difficult or impossible to move by humans. The manipulation devices can grasp various permanent or temporary additive manufacturing manipulation points on a part so that the part can be repositioned or manipulated.

[0053] The control processor 350 can be connected to control any component of the additive manufacturing system 300 described herein, including the laser, laser amplifiers, optics, heating controls, build chamber, and manipulation devices. The control processor 350 can be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate their operation. A wide range of sensors can be used to provide information used for control or monitoring, including imaging devices, light intensity monitors, heat, pressure, or gas sensors. The control processor can be a single central controller, or alternatively, can include one or more independent control systems. The control processor 350 is provided with an interface that allows for input of manufacturing instructions. The use of a wide range of sensors enables a variety of feedback control mechanisms that improve quality, manufacturing throughput, and energy efficiency.

[0054] One embodiment of the operation of a manufacturing system suitable for additive or subtractive manufacturing is illustrated in FIG. 4. In this embodiment, a flowchart 400 illustrates one embodiment of a manufacturing process enabled by desired optical and mechanical components. In step 401, a powder of material, created or recycled as described in this disclosure, is formed. In step 402, the powder material is positioned in a cartridge, bed, chamber, or other suitable support. In some embodiments, the material may be a metal plate for laser cutting using subtractive manufacturing techniques, or a powder that can be melted, fused, sintered, change crystal structure, affect stress patterns, or otherwise induced to be chemically or physically modified by additive manufacturing techniques to form a structure with desired properties.

[0055] In step 404, unpatterned laser energy is emitted by one or more energy emitters, including, but not limited to, solid-state or semiconductor laser devices, and then amplified by one or more laser amplifiers. In step 406, the unpatterned laser energy is shaped and modified (e.g., intensity modulated or focused). In step 408, the unpatterned laser energy is patterned, whereby energy that does not form part of the pattern is disposed of in step 410 (this may include conversion to waste heat, recycling as patterned or unpatterned energy, or waste heat generated in cooling the laser amplifiers in step 404). In step 412, the patterned energy, now forming a one- or two-dimensional image, is relayed toward a material. In step 414, the image is applied to the material to produce part of a 3D structure, whether by subtractive or additive manufacturing. In the case of additive manufacturing, these steps may be repeated (loop 418) until the image (or another subsequent image) has been applied to all required areas of the top layer of material. Once the application of energy to the top layer of material is complete, a new layer may be applied (loop 416) to continue fabricating the 3D structure. These processing loops continue until any remaining excess material can be removed or recycled and the 3D structure is complete.

[0056] FIG. 5 illustrates one embodiment of an additive manufacturing system including a phase-change light valve and switchyard system that enables patterned two-dimensional energy recycling. Additive manufacturing system 520 includes an energy patterning system with a laser source and amplifier 512 that directs one or more continuous or intermittent laser beams into shaping optics 514. Residual heat can be transferred into a waste energy processing unit 522, which may include an active light valve cooling system. After shaping, the beam is patterned in two dimensions by energy patterning unit 530, with some energy typically directed to waste energy processing unit 522. The patterned energy is relayed by one of multiple image relays 532 to one or more article processing units 534A, 534B, 534C, or 534D, typically as a two-dimensional image focused near a movable or fixed-height floor. The floor can be in a cartridge containing a powder hopper or similar material dispenser. The patterned laser beam directed by the image relay 532 may melt, melt, sinter, fuse, change the crystalline structure, affect stress patterns, or otherwise chemically or physically modify the dispensed material to form a structure with desired properties.

[0057] In this embodiment, the waste energy processing unit has multiple components to enable reuse of the discarded patterned energy. Coolant from the laser source and amplifier 512 can be directed into one or more of the generator 524, the heating / cooling thermal management system 525, or the energy dump 526. Additionally, repeaters 528A, 528B, and 528C can transfer energy to the generator 524, the heating / cooling thermal management system 525, or the energy dump 526, respectively. Optionally, repeater 528C can direct the patterned energy to an image repeater 532 for further processing. In other embodiments, the patterned energy can be directed by repeater 528C to repeaters 528B and 528A for insertion into the laser beam provided by the laser source and amplifier 512. Reuse of the patterned image using the image repeater 532 is also possible. The image may be redirected, inverted, reflected, sub-patterned, or otherwise transformed for distribution to one or more article processing units 534A-D. Advantageously, recycling patterned light may improve the energy efficiency of the additive manufacturing process, and in some cases may improve the energy intensity directed to the floor or reduce manufacturing time.

[0058]

[0033] Many modifications and other embodiments of the invention will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. It is understood, therefore, that the invention is not limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims. It is also understood that other embodiments of the invention may be practiced that exclude elements / steps not specifically disclosed herein.

Claims

1. 1. A transmissive light valve system comprising: A liquid crystal layer; a first semiconducting transparent electrode layer in contact with the semiconductor layer having a bandgap greater than 3 eV; and a second semiconducting transparent electrode layer comprising a semiconductor layer with a bandgap greater than 3 eV and a second transparent conductive electrode; The transmissive light valve system comprising:

2. 2. The light valve system of claim 1, the first and second semiconductor layers have a bandgap greater than 4 eV; The light valve system.

3. 2. The light valve system of claim 1, the first and second semiconductor layers include at least one of a GaN semi-insulating layer operating as a photoconductor in the light valve, an iron-doped compensated FeGaN semi-insulating layer, a carbon- or manganese-doped compensated semi-insulating GaN, and a V-SiC semi-insulating layer; The light valve system.

4. 2. The light valve system of claim 1, the first and second transparent conductive electrodes comprise at least one of n-epi GaN, n-epi SiC, ion-implanted GaN, ion-implanted SiC, and zinc aluminate (AZO); The light valve system.

5. 2. The light valve system of claim 1, a first alignment layer positioned between the first transparent conductive electrode and the liquid crystal, and a second alignment layer positioned between the second transparent conductive electrode and the liquid crystal; The light valve system further comprising:

6. 6. A light valve system according to claim 5, at least one of the first and second alignment layers comprises an as-grown inorganic layer; The light valve system.

7. 6. A light valve system according to claim 5, the liquid crystal layer, the first and second transparent electrode and photoconductor layers, and the first and second alignment layers together form a monolithic stack; The light valve system.

8. 6. A light valve system according to claim 5, at least one anti-reflective (AR) coating positioned in contact with at least one of the first and second transparent electrode photoconductor layers and the first and second alignment layers, together forming a monolithic stack; The light valve system further comprising:

9. 6. A light valve system according to claim 5, The light valve has a power of 2 joules / cm ２ operating at energy densities exceeding The light valve system.

10. 1. A monolithic transmissive light valve system comprising: A liquid crystal layer; a first semiconducting transparent electrode in contact with the semi-insulating photoconductor layer, the first wide bandgap semiconductor layer and the first transparent conductive electrode; a second transparent electrode layer in contact with the second wide bandgap or ultra wide bandgap semi-insulating semiconductor layer and the second transparent conductive electrode; Including, a plurality of alignment layers and anti-reflection layers monolithically formed on at least one of the first transparent electrode photoconductor layer, the first transparent conductive electrode, the second transparent electrode photoconductor layer, and the second transparent conductive electrode; The monolithic transmissive light valve system further comprises:

11. 1. A process for manufacturing a transmissive light valve system, comprising: providing a liquid crystal layer; positioning a first transparent electrode in contact with a photoconductor layer comprising a first semiconductor layer having a bandgap greater than 3 eV and a first transparent conductive electrode in contact with said liquid crystal layer; positioning a second transparent electrode layer comprising a semi-insulating semiconductor layer having a bandgap greater than 3 eV and a second transparent conductive electrode in contact with the liquid crystal layer; The process includes the step of:

12. 1. A reflective light valve system comprising: a transparent electrode and a photoconductor layer comprising a semiconductor layer with a bandgap greater than 3 eV; a reflective layer in contact with the photoconductor layer having a transparent electrode; a transparent conductive electrode; and a liquid crystal layer positioned between said reflective layer and said transparent conductive electrode or photoconductor layer with a transparent electrode; The reflective light valve system comprising:

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