Optical addressable light valve based on monolithic semiconductor

Abstract

A monolithic transmissive or reflective light valve system capable of withstanding high light fluence and high average power laser operation is described. The light valve includes a liquid crystal layer on an alignment layer, a first epitaxially doped semiconductor transparent electrode on a light guide layer made of a first wide band gap or ultra wide band gap semi-insulating semiconductor layer (or wafer). A second epitaxial semiconductor transparent electrode layer sandwiches the light valve and includes a second wide-band-gap or ultra-wide-band-gap semi-insulating or conductive semiconductor layer (or wafer). In some embodiments, the doped epitaxial or ion implanted transparent electrode and the light guide layer have matched coefficient of thermal expansion (CTE), and are also matched to the CTE of the second wide band gap material that clamps the light valve. In some embodiments, the transparent electrode and the light guide layer have matched refractive indices and matched light excitation levels.

Description

[0001] Related Applications

[0002] This disclosure is part of a non - provisional patent application claiming the priority benefit of U.S. Patent Application No. 63 / 422,571, filed Nov. 4, 2022, which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to a system and method for high - throughput laser manufacturing. In one embodiment, laser manufacturing is enabled by using a spatial light modulator that includes a semiconductor - based high - power transmissive or reflective light valve.

[0004] Background

[0005] A spatial light modulator imposes some form of spatially varying modulation on a light beam. An SLM typically modulates the intensity of the light beam. However, devices can also be fabricated that modulate the polarization or phase of the light beam or both intensity and phase simultaneously.

[0006] The images established by an electrically - addressed spatial light modulator can be created and changed electronically, just as in most electronic displays. The light modulator can be used to completely or partially block, redirect, or modulate a laser. For example, a spatial light modulator (SLM) (also known as a light valve (LV)) is a type of light modulator that can be used to uniformly transmit information across an entire light beam (1D modulation), provide variations across the light beam to form parallelized optical channels (2D modulation), or provide variations across the volume of a pixel / voxel channel (3D modulation). The information applied can be in the form of amplitude, phase, polarization, wavelength, coherence, or quantum entanglement.

[0007] Industrial applications may require the LV to withstand high - fluence and high - energy laser sources for long periods of time. This enables production with multiple build or processing cycles using typical shot counts in the tens of millions to billions (where printing a 2D area is equivalent to one frame from the LV to the print bed). In a typical industrial system, the requirement for LV lifetime is > 10E6 exposures, and ideally > 10E9 exposures. The light source intensity required to print a material within a reasonable time can exceed 8 J / cm at the print plane 2 , including average optical powers in the kW range. Although various methods can be used to reduce the fluence at the LV, commercially viable industrial processing requires an energy density at the LV of no less than 2 J / cm 2Existing LVs fail well below this energy density and power level, making the use of existing LVs in metal AM systems impractical.

[0008] Typically, the components that fail (or cause failure) within a typical light valve are the transparent conductive electrode (TCE), the alignment layer, the liquid crystal layer (linear electro-optic or LEO material), and the light guide layer. To prevent material failure, the light valve needs to be improved and the light valve materials need to be able to withstand the conditions required for high-speed industrial manufacturing.

[0009] Overview

[0010] In some embodiments, a transmissive light valve system includes a liquid crystal layer, a first transparent electrode layer on a light guide semi-insulating semiconductor layer or on a light guide in the form of a wafer substrate. A second transparent electrode layer including a second widebandgap or ultra-widebandgap semiconductor layer and a second semiconductor transparent conductive electrode is positioned to sandwich or enclose the liquid crystal layer and the alignment layer. In some embodiments, one or more of the light guide layer or wafer and the electrode layers are selected to match the CTE.

[0011] In some embodiments, first and second widebandgap (bandgap greater than 3 eV) or ultra-widebandgap (bandgap greater than 4 eV) semiconductor layers can be used.

[0012] In some embodiments, the first and second widebandgap or ultra-widebandgap semiconductor layers include at least one of the following: 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 doped-compensated or intrinsic semi-insulating layer or wafer.

[0013] In some embodiments, the first transparent conductive electrode and the second transparent conductive electrode include at least one of the following: n-type or p-type epitaxial (epi)-doped - epi GaN, epi SiC, epi Ga2O3, epi diamond, epi aluminum nitride (AlN), or other epitaxially grown widebandgap or ultra-widebandgap semiconductors, or alternatively, a semi-insulating semiconductor with ion-implanted dopants forming a conductive transparent layer, or simply using a doped conductive semiconductor wafer that serves as both the transparent conductive electrode and the substrate supporting the LV device.

[0014] In some embodiments, the first alignment layer can be located between the first transparent conductive electrode and the liquid crystal; and the second alignment layer is located between the second transparent conductive electrodes sandwiching the liquid crystal.

[0015] In some embodiments, at least one of the first alignment layer and the second alignment layer includes an inorganic layer grown or deposited on a substrate.

[0016] In some embodiments, the liquid crystal layer, the first transparent electrode and the photoconductive layer, the second transparent electrode and the photoconductive layer, the first alignment layer, and the second alignment layer together form a monolithic stack of the same matrix material or an epitaxial layer of another crystallographically matched material.

[0017] In some embodiments, at least one antireflection (AR) coating is positioned in contact with at least one of the first transparent electrode photoconductive layer and the second transparent electrode photoconductive layer, and the first alignment layer and the second alignment layer, and together form a monolithic stack when including a high refractive index layer and a low refractive index layer, and the high refractive index layer and the low refractive index layer are formed by adjusting the dopant distribution in each individual layer of the multilayer forming the antireflection coating design.

[0018] In some embodiments, the light valve operates at an energy fluence greater than 2 joules / cm 2 and / or a kW-level average power.

[0019] In some embodiments, a monolithic transmissive light valve system includes a liquid crystal layer. The liquid crystal layer is located between a first transparent electrode and a photoconductive layer, the photoconductive 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, a plurality of alignment layers and antireflection layers can be formed monolithically on at least one of the first transparent electrode and the photoconductive layer, the first transparent conductive electrode, the second transparent electrode photoconductive layer, and the second transparent conductive electrode.

[0020] In some embodiments, a method for manufacturing a transmissive light valve system includes the steps of: providing a liquid crystal layer, and positioning a first transparent electrode and a first photoconductive layer in contact with the liquid crystal layer, the first photoconductive layer including a first wide bandgap or ultra-wide bandgap semiconductor layer. A second transparent electrode layer on a second wide bandgap or ultra-wide bandgap semiconductor layer is also positioned in contact with an alignment layer supporting the liquid crystal layer. Alternatively, a second transparent conductive electrode that also serves as a substrate is in contact with the alignment layer supporting the liquid crystal.

[0021] In some embodiments, a reflective light valve system includes a transparent electrode on a photoconductive layer or a photoconductive wafer, the photoconductive layer or photoconductive wafer including a first wide bandgap or ultra-wide bandgap semi-insulating semiconductor, and a light reflecting layer in contact with the photoconductive. The system also includes a transparent conductive electrode and a liquid crystal layer, wherein an alignment layer is located between the reflective layer and the transparent conductive electrode, or between the reflective layer and another transparent electrode on the photoconductive layer or photoconductive wafer, the photoconductive layer or photoconductive wafer including a second wide or ultra-wide bandgap semi-insulating semiconductor substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Non-limiting and non-exhaustive embodiments of the present disclosure are described with reference to the following figures, in which like reference numerals refer to like parts throughout the figures unless otherwise specified.

[0024] Figure 1A A single-chip transmissive light valve that can be used in an additive manufacturing system is shown;

[0025] Figure 1B A single-chip reflective light valve that can be used in an additive manufacturing system is shown;

[0026] Figure 2A An embodiment of a single-chip transmissive light valve is shown;

[0027] Figure 2B An embodiment of a single-chip transmissive light valve including an iron-doped Fe-GaN semi-insulating wafer is shown;

[0028] Figure 3 An additive manufacturing system capable of providing a one-dimensional or two-dimensional light beam to a cartridge is shown; and

[0029] Figure 4 A method of operating a cartridge-based additive manufacturing system capable of providing a one-dimensional or two-dimensional light beam to a cartridge is shown; and

[0030] Figure 5 is an embodiment of an additive manufacturing system that includes a light valve based on phase change addressing and / or modulation layers and a switchyard system capable of reusing patterned two-dimensional energy.

[0031] Detailed description

[0032] In the following description, reference is made to the figures, which form a part of the description 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, and it should be understood that various disclosed embodiments may be modified and other embodiments may be utilized without departing from the scope of the present disclosure. Accordingly, the following detailed description should not be construed as limiting.

[0033] Figure 1A An embodiment of a single-chip and high-power transmissive light valve is shown, which is suitable for an additive manufacturing system or in other applications where an energy density greater than 2 joules / cm 2 、kilowatt-level power, multi-cm 2Applications that require tens of joules of energy over a range and have a long light valve life during long-term use. In one embodiment, the monolithic transmissive light valve system 100A includes a liquid crystal layer 104A. The liquid crystal layer 104A is located between a first optically patterned layer 102A(i) and a second optically patterned layer 102A(ii). The liquid crystal layer 104A, together with the first optically patterned layer 102A(i) and the second optically patterned layer 102A(ii), can be combined to form a monolithic block that resists peeling or separation between layers and has a matched CTE and refractive index between and within the layers to hold 104A. In some embodiments, the first optically patterned layer 102A(i) and the second optically patterned layer 102A(ii) can have their respective coefficient of thermal expansion (CTE) matched to within 10%, within 5%, or within 1% of each other. Additionally, the CTE of the first optically patterned layer 102A(i) and the second optically patterned layer 102A(ii) can be matched to within 10%, within 5%, or within 1% of each other and of the liquid crystal layer 104A. When heated by a laser, the closely matched CTEs advantageously promote uniform expansion of the monolithic transmissive light valve system 100A. If the same mostly transparent material is used for each layer, balanced light absorption and heating will be achieved between the layers, such that the bottom and top layers experience the same temperature rise to minimize thermomechanical strain and stress cycling, fatigue, and damage, thereby extending the life of the device.

[0034] In some embodiments, the first optically patterned layer 102A(i) can be formed by a first transparent electrode over a first wide-bandgap or ultra-wide-bandgap semiconductor layer. Similarly, the second optically patterned layer 102A(ii) can be formed by a second transparent electrode layer that includes a second wide-bandgap semiconductor layer. In some embodiments, multiple alignment layers and antireflection layers can be formed monolithically over at least one of the first transparent electrode semiconductor and the first photoconductive semiconductor layer, the second semiconductor photoconductive layer, and the second semiconductor transparent conductive electrode.

[0035] In operation, the addressing laser 101A(i) creates a spatial pattern that, in combination with a polarizer, selectively causes the laser light passing through the laser valve system 100A to be blocked or transmitted. The high fluence, high power, and high energy input light 101A(ii) is directed through the laser valve system 100A, spatially patterned, and becomes the output light 101A(iii). This light can be directed to heat a powder bed suitable for additive manufacturing, as will be described later with reference to Figure 3 、 Figure 4 and Figure 5 as described.

[0036] Figure 1BShows an embodiment of a monolithic, high fluence, high power, and high energy reflective light valve suitable for additive manufacturing systems or other applications that require a long light valve life when in use. In one embodiment, the monolithic reflective light valve system 100B includes a liquid crystal layer 104B. The liquid crystal layer 104B is located between a first light patterning layer 102B(i) and a second light patterning layer 102B(ii). The liquid crystal layer 104B, along with the first light patterning layer 102B(i) and the second light patterning layer 102B(ii), can be combined to form a monolithic block to resist delamination or separation between layers and have a matched CTE and refractive index between and within the layers to clamp 104B. In some embodiments, the first light patterning layer 102B(i) and the second light patterning layer 102B(ii) can have their respective coefficient of thermal expansion (CTE) matched to within 10%, within 5%, or within 1% of each other. Additionally, the CTE of the first light patterning layer 102B(i) and the second light patterning layer 102B(ii) can be matched to within 10%, within 5%, or within 1% of each other and of the liquid crystal layer 104A. When heated by a laser, the closely matched CTEs advantageously facilitate uniform expansion of the monolithic transmissive light valve system 100B. If the same mostly transparent material is used for each layer, balanced light absorption and heating will be achieved between the layers, such that the bottom layer and the top layer experience the same temperature rise to minimize thermo-mechanical strain and stress cycling, fatigue, and damage, thereby extending the life. Additionally, the photo-induced semiconductor excitation levels in the light guide layers can also be balanced or closely matched to less than one percent in order to generate a more tightly bound electric field from top to bottom applied to the liquid crystal, which can improve the spatial resolution of patterning. 2 In some embodiments, the first light patterning layer 102B(i) can be formed from a first transparent electrode semiconductor layer that includes a first wide bandgap or ultra-wide bandgap light guide semiconductor and a reflective layer (e.g., a dielectric mirror or a doped semiconductor multi-layer). The second light patterning layer 102B(ii) can be formed from a second semiconductor transparent electrode layer and a wide bandgap or ultra-wide bandgap light guide semiconductor layer. In some embodiments, a plurality of alignment layers and anti-reflection layers can be formed monolithically on at least one of the first transparent electrode and light guide layer, the first transparent conductive electrode, the second transparent electrode and light guide layer, and the second transparent conductive electrode.

[0037]

[0038] ​In operation, the addressing laser 101B(i) creates a spatial pattern that selectively causes the laser reflected by the laser valve system 100B to be blocked or transmitted. The high fluence, high power, and high energy input light 101B(ii) is directed into the laser valve system 100B, spatially patterned, reflected, and becomes the output light 101B(iii). This light can be directed to heat a powder bed suitable for additive manufacturing, as described later with reference to Figure 3 、 Figure 4 and Figure 5 .

[0039] Figure 2A An embodiment of a monolithic, high fluence, high power, and high energy transmissive light valve 200A is shown. The light valve 200A includes light patterning layer stacks 202(i) and 202(ii) that sandwich or clamp a liquid crystal 204. From top to bottom, layer 206 is an anti-reflection (AR) layer, layer 208 is an n-type conductive semiconductor created, for example, by ion implantation or 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 anti-reflection layer 212 is stacked on the alignment layer 214. The alignment layer 214 is grown or deposited on a 5-micron thick liquid crystal layer 204, completing the light patterning stack 202(i). Below the liquid crystal layer 204 is a second light patterning layer stack 202(ii) that includes an alignment layer 216 stacked on an anti-reflection layer 218. The next layer in the stack is a layer 220 formed of a semi-insulating (SI) semiconductor and a layer 222 formed of an n-type transparent conductive semiconductor. The second light patterning layer stack 202(ii) is completed by an anti-reflection layer 224.

[0040] In operation, the addressing (“writing”) laser 201B(i) creates a spatial pattern that selectively causes the “read” laser passing through the light valve system 200A to be blocked or transmitted or partially transmitted (“gray scaling”). The high fluence, high power, and high energy input read light 201A(ii) is directed into the laser valve system 200A, spatially patterned, transmitted, and becomes spatially patterned output light 201A(iii). This light can be directed to heat a powder print bed 234 suitable for additive manufacturing, as described later with reference to Figure 3 、 Figure 4 and Figure 5 .

[0041] Figure 2B Another embodiment of a monolithic high fluence transmissive light valve 200B similar to that described previously with reference to Figure 2A is shown. However, contrary to the embodiment of Figure 2A showing semi-insulating (SI) semiconductor layers 210 and 220, in Figure 2BAn Fe-doped and compensated Fe-GaN semi-insulating (SI) wafer is used. Figure 2B It is shown that the epitaxially grown n-epi GaN layer provides a transparent electrode.

[0042] In reference Figure 3 In the illustrated embodiment, the additive manufacturing system can be represented by various modules that form the additive manufacturing method and system 300. As Figure 3 shown, the laser source and amplifier 312 can be configured 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 an equivalent that acts on a continuous laser source, such as a laser diode. In some embodiments, this can also be achieved by a fiber laser or a fiber-emitted laser source, which is subsequently modulated by an acousto-optic or electro-optic modulator. In some embodiments, a high repetition rate pulse source using a Pockels cell can be used to generate a pulse train of any length.

[0043] Possible laser types include, but are not limited to: gas lasers, chemical lasers, dye lasers, metal vapor lasers, solid-state lasers (such as fiber), semiconductor (such as diode) lasers, free electron lasers, gas dynamic lasers, "nickel-like" samarium lasers, Raman lasers, or nuclear pumped lasers.

[0044] Gas lasers can 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.

[0045] Chemical lasers can include lasers such as: hydrogen fluoride lasers, deuterium fluoride lasers, COIL (chemical oxygen iodine laser), or Agil (all-gas-phase iodine laser).

[0046] 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, or manganese (Mn / MnCl2) vapor lasers. Rubidium or other alkali metal vapor lasers can also be used. Solid-state lasers can include lasers such as: 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 oxyborate Nd:YCa4O(BO3)3 or simply Nd:YCOB, neodymium glass (Nd:Glass) lasers, titanium sapphire (Ti:sapphire) lasers, thulium YAG (Tm:YAG) lasers, ytterbium YAG (Yb:YAG) lasers, ytterbium:2O3 (glass or ceramic) lasers, ytterbium-doped glass lasers (rod, plate / chip and fiber), holmium YAG (Ho:YAG) lasers, chromium zinc selenide (Cr:ZnSe) lasers, cerium-doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), promethium-147 phosphate glass (147Pm+3:Glass) solid-state lasers, chromium-doped beryllium aluminum silicate (chrysoberyl) lasers, erbium and erbium-ytterbium co-doped glass lasers, uranium(III)-doped calcium fluoride (U:CaF2) solid-state lasers, samarium(II)-doped calcium fluoride (Sm:CaF2) lasers or F-center (F-Center) lasers.

[0047] Semiconductor lasers can include laser medium types such as: GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, GaInP, InGaAs, InGaAsO, GaInAsSb, lead salts, vertical cavity surface emitting lasers (VCSEL), quantum cascade lasers, hybrid silicon lasers or combinations thereof.

[0048] As Figure 3As shown, the additive manufacturing system 300 uses a laser that can provide one-dimensional or two-dimensional controlled directional energy as part of the energy patterning system 310. In some embodiments, one-dimensional patterning can be directed as linear or curved strips, grating lines, helices, or any other suitable form. Two-dimensional patterning can include discrete or overlapping tiles, or an image with varying laser intensity. Two-dimensional image patterns with non-square boundaries can be used, overlapping or interpenetrating images can be used, and the images can be provided by two or more energy patterning systems. The energy patterning system 310 uses a laser source and amplifier 312 to direct one or more continuous or intermittent energy beams toward the beam shaping optics 314. After shaping, if desired, the beam is patterned by the energy patterning unit 316, and typically some energy is directed to the rejected energy handling unit 318. The patterned energy is relayed by the image repeater 320 to the article processing unit 340, and in one embodiment, as a two-dimensional image 322 focused near the bed 346. The article processing unit 340 can include a cartridge as previously discussed. The article processing unit 340 has a plate or bed 346 (with walls 348) that together form a sealed cartridge chamber containing the material 344 (such as metal powder) dispensed by the powder hopper or other material dispenser 342. The dispensed powder can be generated or recycled as discussed in this disclosure. The patterned energy directed by the image repeater 320 can melt, fuse, sinter, amalgamate, change the crystal structure, affect the stress pattern, or otherwise chemically or physically alter the dispensed and distributed material 344 to form a structure with desired properties. The control processor 350 can be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate the operation of the laser source and amplifier 312, the beam shaping optics 314, the laser patterning unit 316, and the image repeater 320, as well as any other components of the system 300. As will be understood, the connections can be wired or wireless, continuous or intermittent, and include the ability for feedback (e.g., heating can be adjusted in response to sensed temperature).

[0049] In some embodiments, the beam shaping optical device 314 may include a variety of imaging optical devices to combine, focus, diverge, reflect, refract, homogenize one or more laser beams received from the laser source and amplifier 312, adjust the intensity of one or more laser beams received from the laser source and amplifier 312, adjust the frequency of one or more laser beams received from the laser source and amplifier 312, or otherwise shape and direct one or more laser beams received from the laser source and amplifier 312 towards the laser patterning unit 316. In one embodiment, a wavelength selective mirror (e.g., a dichroic mirror) or a diffractive element may be used to combine multiple beams, each beam having a different optical wavelength. In other embodiments, a multi-faceted mirror, a microlens, and refractive or diffractive optical elements may be used to homogenize or combine multiple beams.

[0050] The laser patterning unit 316 may include a monolithic light valve as described in reference Figure 1A , Figure 1B . The laser patterning unit 316 may also include static or dynamic energy patterning elements. For example, the laser beam may be blocked by a mask having fixed or movable elements. To increase the flexibility and simplicity of image patterning, pixel-addressable masking, image generation, or transmission may be used. In some embodiments, the laser patterning unit includes an addressable light valve as described in reference Figure 1A and Figure 1B that provides patterning either alone or in combination with other patterning mechanisms. The light valve may be transmissive, reflective, or use a combination of transmissive and reflective elements. Electrical addressing or optical addressing may be used to dynamically modify the pattern. In one embodiment, a transmissive optically addressed light valve is used to rotate the polarization of light passing through the valve, where the optically addressed pixels form a pattern defined by a light projection source. In another embodiment, a reflective optically addressed light valve includes a write beam for changing the polarization of a read beam. In certain embodiments, non-optically addressed light valves may be used. These may include, but are not limited to, electrically addressable pixel elements, movable mirrors or micromirror systems, piezoelectric or microactuated optical systems, fixed or movable masks or shields, or any other conventional system capable of providing high-intensity light patterning.

[0051] The waste energy handling unit 318 is used to disperse, redirect, or utilize the energy that is not patterned and passes through the image repeater 320. In one embodiment, the waste energy handling unit 318 may include passive or active cooling elements that remove heat from both the laser source and amplifier 312 and the laser patterning unit 316. In other embodiments, the waste energy handling unit may include a "beam dump" to absorb any beam energy not used in defining the laser pattern and convert it to heat. In still other embodiments, beam shaping optics 314 may be used to recover the waste laser beam energy. Alternatively or additionally, the waste beam energy may be directed to the article handling unit 340 for heating or further patterning. In certain embodiments, the waste beam energy may be directed to an additional energy patterning system or article handling unit.

[0052] In one embodiment, a "switchyard" type optical system may be used. The switchyard system is adapted to reduce the light waste in an additive manufacturing system due to the unwanted light discarded due to the pattern to be printed. The switchyard involves the redirection of a complex pattern from where it is generated (in this case, the plane where the spatial pattern is imparted to a structured or unstructured beam) to where it is delivered 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 used in, for example but not limited to, laser-based additive manufacturing techniques where a mask is applied to the light. Advantageously, in various embodiments in accordance with the present disclosure, the discarded energy may be recovered in a homogenized form or as patterned light for maintaining high power efficiency or high productivity. Additionally, the discarded energy may be recovered and reused to increase the intensity for printing more difficult-to-process materials.

[0053] The image repeater 320 can receive the patterned image (one-dimensional or two-dimensional) directly from the laser patterning unit 316 or through a switch station and direct it to the article handling unit 340. In a manner similar to the beam shaping optics 314, the image repeater 320 can include optics for combining, focusing, diverging, reflecting, refracting the patterned light, adjusting the intensity of the patterned light, adjusting the frequency of the patterned light, or otherwise shaping and directing the patterned light. Movable mirrors, prisms, diffractive optical elements, or solid-state optical systems that do not require substantial physical movement can be used to direct the patterned light. One of the plurality of lens assemblies can be configured to provide incident light with a magnification ratio, where the lens assembly has both a first set of optical lenses and a second set of optical lenses, and the second set of optical lenses can be exchanged from the lens assembly. The rotation of one or more sets of mirrors mounted on a compensation gantry and a final mirror mounted on a build platform gantry can be used to direct the incident light from a precursor mirror to a desired location. Translational movement of the compensation gantry and the build platform gantry can also ensure that the distance of the incident light from the precursor mirror to the article handling unit 340 is substantially equal to the image distance. In effect, this enables the beam delivery size and intensity for different materials to vary rapidly over the location of the build area while ensuring high availability of the system.

[0054] A material dispenser 342 (such as a powder hopper) in the article handling unit 340 (such as a cartridge) can dispense, remove, mix, provide grading or variation of material type or particle size, or adjust the layer thickness of the material. The material can include metals, ceramics, glasses, polymer powders, other fusible materials capable of undergoing a thermally induced phase change from solid to liquid and back to solid, or combinations thereof. The material can also include a composite of a fusible material and a non-fusible material, where either or both of the components can be selectively targeted by the imaging relay system to melt the fusible component while leaving the non-fusible material intact or subjecting the non-fusible material to evaporation / destruction / combustion or other destruction processes. In certain embodiments, slurries, sprays, coatings, wires, strips, or sheets of the material can be used. Unwanted material can be removed for disposal or recycling by using a blower, a vacuum system, sweeping, vibration, shaking, tilting, or inverting the bed 346.

[0055] In addition to the material handling components, the article handling unit 340 can include components for holding and supporting the 3D structure, mechanisms for heating or cooling the chamber, auxiliary optics or support optics, and sensors and control mechanisms for monitoring or regulating material or environmental conditions. The article handling unit can support a vacuum or inert gas atmosphere, in whole or in part, to reduce unwanted chemical interactions and mitigate the risk of fire or explosion (especially for reactive metals). In some embodiments, various pure gases or mixtures of other atmospheres can be used, including pure gases or mixtures containing: 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-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) can be used. An enclosure atmospheric composition with at least about 1% He by volume (or number density) and a selected percentage of inert / non-reactive gas can be used.

[0056] In certain embodiments, multiple article handling units, cartridges, or build chambers (each having a build platform that houses a powder bed) can be used in combination with multiple optomechanical assemblies arranged to receive one or more incident energy beams and direct them into the cartridges. Multiple cartridges permit printing of one or more print jobs simultaneously.

[0057] In another embodiment, one or more article handling units, cartridges, or build chambers may have a cartridge held at a fixed height while the optics are vertically movable. The distance between the final optics of the lens assembly and the top surface of the powder bed can be managed to be substantially constant by indexing the final optics upward by a distance equivalent to the powder layer thickness while holding the build platform at a fixed height. Advantageously, it may be easier to fabricate large and heavy objects compared to a vertically movable build platform, as precise micron-scale movement of the varying mass of the build platform is not required. Generally, build chambers intended for metal powders with a volume greater than about 0.1 cubic meters - 0.2 cubic meters (i.e., greater than 100 liters - 200 liters or heavier than 500 kg - 1,000 kg) will benefit most from holding the build platform at a fixed height.

[0058] In one embodiment, a portion of a layer of the powder bed in a cartridge may be selectively melted or fused to form one or more temporary walls from the molten portion of the powder bed layer to accommodate another portion of the powder bed layer on the build platform. In selected embodiments, fluid channels may be formed in one or more first walls to enable improved thermal management.

[0059] In some embodiments, an additive manufacturing system may include an article handling unit or cartridge that supports a powder bed that can be tilted, inverted, and shaken to substantially separate the powder bed from the build platform in a hopper. The powder material forming the powder bed can be collected in the hopper for reuse in a later printing operation. The powder collection process can be automated, and a vacuum system or gas injection system may also be used to assist in powder removal and evacuation.

[0060] For some embodiments, an additive manufacturing system may be configured to easily handle parts that are longer than the available build chamber or cartridge. A continuous (long) part may sequentially advance from a first region to a second region in a longitudinal direction. In the first region, selected particles of the particulate material may be consolidated. In the second region, unconsolidated particles of the particulate material may be removed. The first portion of the continuous part may advance from the second region to a third region, while the last portion of the continuous part is formed within the first region, and the first portion remains in the same position in the lateral and transverse directions as the position occupied by the first portion within the first and second regions. In effect, additive manufacturing and scavenging (e.g., separation and / or reuse of unused or unconsolidated granular material) may occur in parallel (i.e., simultaneously) at different locations or regions on a part conveyor without the need to stop for removal of the granular material and / or the part.

[0061] In another embodiment, additive manufacturing capabilities can be enhanced by using an enclosure that limits gas mass exchange between the interior and exterior of the enclosure. An airlock provides an interface between the interior and exterior; the interior having a plurality of additive manufacturing chambers, including chambers that support powder bed fusion. A gas management system maintains the gaseous oxygen within the interior at or below a limiting oxygen concentration, thereby increasing the types of powders that can be used and the flexibility of processing within the system.

[0062] In another manufacturing embodiment, capabilities can be enhanced by housing an article handling unit, a cartridge, or a build chamber within an enclosure, the build chamber being capable of creating parts having a weight greater than or equal to 2,000 kilograms. A gas management system can maintain the gaseous oxygen within the enclosure at a concentration below atmospheric levels. In some embodiments, a wheeled vehicle can transport a part from within the enclosure through the airlock, as the airlock serves to buffer between the gas environment within the enclosure and the gas environment exterior to the enclosure, and transport it to a location external to both the enclosure and the airlock.

[0063] Other manufacturing embodiments relate to the real-time collection of powder samples from a powder bed. An ingester system is used for the in-process collection and characterization of powder samples. The collection can be performed periodically, and the results of the characterization lead to the adjustment of the powder bed fusion process. The ingester system can optionally be used for one or more of auditing, process adjustment, or actions such as modifying printer parameters or verifying the proper use of licensed powder materials.

[0064] Another improvement to the additive manufacturing process is described, which can be provided by using a manipulator device such as a crane, a lifting gantry, a robotic arm, or a similar device that allows manipulation of parts that are difficult or impossible for a human to move. The manipulator device can grip various permanent or temporarily additively manufactured manipulation points on the part to enable repositioning or manipulation of the part.

[0065] The control processor 350 can be connected to control any of the components of the additive manufacturing system 300 described herein, including lasers, laser amplifiers, optics, thermal controls, build chambers, and manipulator devices. The control processor 350 can be connected to various sensors, actuators, heating or cooling systems, monitors, and controllers to coordinate operations. A wide range of sensors, including imagers, light intensity monitors, thermal sensors, pressure sensors, or gas sensors, can be used to provide information for use in control or monitoring. The control processor can be a single central controller, or alternatively, can include one or more independent control systems. The controller processor 350 is provided with an interface that allows the input of manufacturing instructions. The use of a wide range of sensors allows for various feedback control mechanisms to improve quality, manufacturing throughput, and energy efficiency.

[0066] In Figure 4 an embodiment of a manufacturing system that operates applicable to additive or subtractive manufacturing is shown. In this embodiment, flowchart 400 illustrates an embodiment of a manufacturing process supported by the described optical and mechanical components. In step 401, a material powder that is generated or recycled as discussed 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 can be a metal sheet that is laser cut using subtractive manufacturing techniques, or a powder that can be melted, fused, sintered, induced to change crystal structure, have an affected stress distribution pattern, or otherwise be chemically or physically altered to form a structure with desired properties by additive manufacturing techniques.

[0067] In step 404, unpatterned laser energy is emitted by one or more energy emitters including, but not limited to, solid-state or semiconductor lasers, and then amplified by one or more laser amplifiers. In step 406, the unpatterned laser energy is shaped and modified (e.g., intensity modulation or focusing). In step 408, the unpatterned laser energy is patterned, and in step 410, the energy of a portion that is not formed into a pattern is processed (this can include conversion to waste heat, recycling as patterned or unpatterned energy, or waste heat generated by cooling the laser amplifier in step 404). In step 412, the patterned energy that now forms a one-dimensional or two-dimensional image is relayed toward the material. In step 414, the image is applied to the material, either for subtractive processing or for additively building a portion of a 3D structure. For additive manufacturing, these steps (loop 418) can be repeated until the image (or different subsequent images) has been applied to all necessary areas of the top layer of the material. When the application of energy to the top layer of the material is complete, a new layer can be applied (loop 416) to continue building the 3D structure. These process loops continue until the 3D structure is complete, at which point the remaining excess material can be removed or recycled.

[0068] Figure 5is an embodiment of an additive manufacturing system that includes a phase change light valve and a switching station system that enables the reuse of patterned two-dimensional energy. The additive manufacturing system 520 has an energy patterning system that has a laser and amplifier source 512 that directs one or more continuous or intermittent laser beams toward beam shaping optics 514. Excess heat can be transferred to a waste energy processing unit 522 that can include an active light valve cooling system. After shaping, the beam is two-dimensionally patterned by an energy patterning unit 530, and generally some energy is directed to the waste energy processing unit 522. The patterned energy is relayed by one of a plurality of image relays 532 toward one or more article processing units 534A, 534B, 534C, or 534D, typically as a two-dimensional image focused near a moveable or fixed height bed. The bed is located within a cartridge that includes a powder hopper or similar material dispenser. The patterned laser beam directed by the image relay 532 can melt, fuse, sinter, combine, change crystal structure, affect stress distribution patterns, or otherwise chemically or physically alter the dispensed material to form a structure with desired properties.

[0069] In this embodiment, the waste energy processing unit has multiple components to allow the reuse of wasted patterned energy. Coolant fluid from the laser amplifier and source 512 can be directed to one or more of a generator 524, a heating / cooling thermal management system 525, or an energy dump 526. Additionally, relays 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, relay 528C can direct the patterned energy into the image relay 532 for further processing. In other embodiments, the patterned energy can be directed by relay 528C to relays 528B and 528A for insertion into the laser beam provided by the laser and amplifier source 512. Image relays 532 can also be used to reuse the patterned images. The images can be redirected, inverted, mirrored, sub-patterned, or otherwise transformed for distribution to one or more article processing units 534A - 534D. Advantageously, the reuse of patterned light can improve the energy efficiency of the additive manufacturing process and, in some cases, increase the energy intensity directed at the bed or reduce the manufacturing time.

[0070] Many modifications and other embodiments of the present invention will come to the mind of those skilled in the art who benefit from the teachings given in the foregoing description and the related drawings. Therefore, it is to be understood that the present 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 to be understood that other embodiments of the present invention may be practiced without the elements / steps not specifically disclosed herein.

Claims

1. A transmissive light valve system, comprising: A liquid crystal layer; A first semiconductor transparent electrode layer, the first semiconductor transparent electrode layer being located on a semiconductor layer having a bandgap greater than 3 eV; And A second semiconductor transparent electrode layer, the second semiconductor transparent electrode layer comprising a semiconductor layer having a bandgap greater than 3 eV and a second transparent conductive electrode.

2. The light valve system according to claim 1, wherein The first semiconductor layer and the second semiconductor layer have a bandgap greater than 4 eV.

3. The light valve system according to claim 1, wherein, The first semiconductor layer and the second semiconductor layer include at least one of the following: a GaN semi-insulating layer serving as a light guide in the light valve, an iron-doped compensated FeGaN semi-insulating layer, and a carbon- or manganese-doped compensated semi-insulating GaN, and a V-SiC semi-insulating layer.

4. The light valve system according to claim 1, wherein, The first transparent conductive electrode and the second transparent conductive electrode include at least one of the following: n-epi GaN, n-epi SiC, ion-implanted GaN, ion-implanted SiC, and aluminum zinc oxide (AZO).

5. The light valve system according to claim 1, further comprising a first alignment layer located between the first transparent conductive electrode and the liquid crystal; and a second alignment layer located between the second transparent conductive electrode and the liquid crystal.

6. The light valve system according to claim 5, wherein, At least one of the first alignment layer and the second alignment layer includes a grown inorganic layer.

7. The light valve system according to claim 5, wherein, The liquid crystal layer, the first transparent electrode and the light guide layer, the second transparent electrode and the light guide layer, the first alignment layer and the second alignment layer together form a monolithic stack.

8. The light valve system according to claim 5, further comprising at least one anti-reflection (AR) coating, the at least one anti-reflection (AR) coating being positioned to contact at least one of the first transparent electrode light guide layer, the second transparent electrode light guide layer, the first alignment layer, and the second alignment layer, and together forming a monolithic stack.

9. The light valve system according to claim 5, wherein, The light valve operates at an energy density greater than 2 joules / cm 2 .

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

11. A method for manufacturing a transmissive light valve system, comprising the steps of: Providing a liquid crystal layer; Positioning a first transparent electrode on a light guide layer, the light guide layer including a first semiconductor layer having a bandgap greater than 3 eV and a first transparent conductive electrode in contact with the liquid crystal layer; And Positioning a second transparent electrode layer, the second transparent electrode layer including 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.

12. A reflective light valve system, comprising: A transparent electrode and a light guide layer, the light guide layer including a semiconductor layer having a bandgap greater than 3 eV; A reflective layer, the reflective layer being in contact with the light guide layer having a transparent electrode; A transparent conductive electrode; And A liquid crystal layer, the liquid crystal layer being located between the reflective layer and the transparent conductive electrode or the light guide layer having a transparent electrode.

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