Method and system for 3D printing of optical elements

Abstract

A method for production of optical elements, particularly gratings and multi-component lenses. Laser-Induced Forward Transfer (LIFT) is used to produce the optical elements according to principles of additive manufacturing, in which the optical element is fabricated layer by layer from droplets deposited via LIFT. The small size of the droplets enables fabrication of elements as a sequence of layers of thickness of tens of nanometers.

Description

METHOD AND SYSTEM FOR 3D PRINTING OF OPTICAL ELEMENTSREFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Pat. Appl. No. 63 / 561,393, filed 5 March 2024; from U.S. Provisional Pat. Appl. No. 63 / 667,384, filed 3 July 2024; and from U.S. Provisional Pat. Appl. No. 63 / 724,976, filed 26 November 2024. The contents of all of these applications are incorporated by reference in their entirety.FIELD OF THE INVENTION

[0002] This application relates in general to means and methods fabrication of optical elements and coatings therefor by additive manufacture (3D printing). It relates in particular to fabrication of optical gratings, compound lenses, and coatings for optical elements by additive manufacturing methods such as Laser-Induced Forward Transfer that produce the optical element by deposition or printing of droplets of a volatile carrier containing a suspension or solution of the optical element material in which the droplets have diameters of on the order of 10 pm and thicknesses of <600 nm.BACKGROUND OF THE INVENTION

[0003] The production of optical elements such as lenses and gratings is a technology that stretches back literally millennia. Despite the long history of production of optical elements, many challenges remain.

[0004] For example, traditional methods for the fabrication of optical gratings such as photolithography, electron beam lithography, and nanoimprint lithography, while effective, often involve complicated, time-consuming, and costly procedures. These methods require highly controlled environments and specialized equipment, which can drive up production costs and limit scalability. Additionally, achieving the necessary precision and uniformity is difficult, especially for applications requiring high performance and fine resolutions. Moreover, current fabrication solutions often lack the ability to support flexible optics solutions, which are increasingly in demand for modern applications. These challenges not only affect the efficiency of production but also restrict the potential for innovation and application in advanced optical systems. There is a clear need for a more efficient, cost-effective, and precise method of fabricating optics gratings to overcome these limitations and meet the growing demands of the industry.

[0005] As mentioned above, several manufacturing solutions are currently available for fabricating optical gratings, each with its own set of advantages and disadvantages. These prior art methods often come with limitations that can hinder their effectiveness and efficiency, however.

[0006] Photolithography: Photolithography is based on transferring a pattern from a photomask to a substrate using light. While photolithography can produce high-resolution patterns, it requires expensive, specialized equipment and highly controlled environments. Additionally, the process can be time-consuming and is not easily scalable economically. Moreover, it is hard to apply it on curved and flexible substrates.

[0007] Electron Beam Lithography (EBL): EBL uses a focused beam of electrons to create fine patterns with high precision. However, the process is extremely slow and expensive, making it impractical for large-scale production. The need for a vacuum environment and complex machinery further adds to the cost and complexity.

[0008] Nanoimprint Lithography (NIL): This technique involves pressing a nano structured mold into a resist layer to create patterns. While NIL can achieve high resolution and throughput, it poses challenges in mold fabrication and alignment. The process also requires significant upfront investment in mold production, which can be costly. NIL also fails when there is a need for large areas of grating. NIL techniques known in the art also suffer from the difficulty that the yield achievable in practice is not sufficient to allow economical mass production.

[0009] Despite the advancements in current fabrication technologies, there remain several unmet needs that must be addressed to further enhance the production of optics gratings and other nano-scale patterns. Addressing these needs is crucial for improving efficiency, reducing costs, and expanding the applicability of these technologies. Examples of these issues include:

[0010] Scalability: Many existing methods are not easily scalable to large-scale production. Developing scalable solutions that maintain high quality and uniformity across large areas is essential for meeting industrial demands.

[0011] Cost Reduction: The high costs associated with traditional fabrication methods limit their widespread adoption. More cost-effective processes are needed to make high-quality optics gratings and nano-scale patterns accessible to a broader range of industries.

[0012] Flexibility: Current solutions often lack the ability to support flexible and adaptive optics, which are increasingly important for emerging technologies. Methods that can produce flexible, yet precise and durable, optical components are needed.

[0013] Simplification of Processes: Many traditional methods involve complex, multi-step procedures that require specialized equipment and environments. Simplifying these processes without compromising on quality would greatly enhance manufacturing efficiency and reduce barriers to entry.

[0014] Fast Prototyping with Scalability: There is a lack of rapid prototyping solutions that can quickly develop and test new designs before scaling up to mass production. Techniques that enable fast prototyping while allowing for a smooth transition to large-scale manufacturing are essential for accelerating innovation and reducing time-to-market.

[0015] Similar to fabrication of gratings, many challenges remain in the fabrication of multielement lenses, also known as compound lenses, are sophisticated optical devices composed of multiple individual lens elements arranged in a specific configuration. These lenses are designed to manipulate light in order to achieve desired optical outcomes, such as focusing, magnification, reflection, beam splitting, beam combining, aberration correction, and image quality enhancement. Each lens element within a multi-element lens serves a unique purpose and contributes to the overall optical performance of the system

[0016] The design of multi-element lenses typically involves careful consideration of various factors, including the curvature, thickness, refractive index, and dispersion properties of each lens element. By strategically combining different types of lens elements, such as convex and concave lenses made from different types of optical materials, lens designers can effectively control the behavior of light as it passes through the lens system.

[0017] One common configuration of multi-element lenses is the compound lens assembly, where multiple lens elements are cemented or mechanically aligned together within a single lens barrel. This arrangement allows for greater flexibility in controlling optical aberrations and improving image quality across different focal lengths and apertures.

[0018] Multi-element lenses find applications in a wide range of optical systems, including camera lenses, microscope objectives, telescopes, and eyeglasses. In photography, for example, multi-element lenses play a crucial role in achieving sharp and distortion-free images, particularly in zoom lenses where multiple focal lengths need to be covered.

[0019] Overall, the complexity and versatility of multi-element lenses make them indispensable tools in modem optics, enabling the creation of advanced imaging systems that meet the demanding requirements of various scientific, industrial, and consumer applications.

[0020] Production of multi-element lenses remains both an art and a science, requiring a delicate balance of precision and innovation. Examples of methods of fabrication of multielement lenses include:

[0021] Lens Stack assembly: One common implementation design involves assembling multielement lenses by stacking individual lens elements and spacers into a tube or lens barrel. This method typically requires precise positioning of each lens element and spacer within the barrel to achieve the desired optical performance. While this approach offers simplicity in assembly and alignment, it may pose challenges in maintaining tight tolerances and preventing optical misalignments during the manufacturing process. Additionally, variations in the dimensions of lens elements and spacers can affect the overall performance consistency of the assembled lenses.

[0022] Adhesive bonding: Another implementation design entails bonding individual lens elements onto a high-accuracy mechanical structure using specialized optical adhesives. This method allows for precise alignment and fixation of lens elements onto the substrate, ensuring optimal optical performance. However, the adhesive bonding process requires stringent control of environmental conditions, such as temperature and humidity, to prevent variations in bond strength and optical properties. Moreover, the use of adhesives introduces the risk of optical contamination or degradation over time, which can impact the long-term reliability and performance stability of the assembled lenses.

[0023] Active Alignment tools: Advanced implementation designs utilize active alignment tools and techniques to assemble and align multi-element lenses with high precision. These tools often involve computer-controlled mechanisms that adjust the position and orientation of lens elements in real-time based on feedback from optical sensors or metrology systems. By actively optimizing the alignment of lens elements during assembly, this approach can mitigate the effects of manufacturing tolerances and variations, resulting in superior optical performance and consistency. However, the complexity and cost associated with active alignment tools may pose challenges for mass production and scalability, particularly in high- volume manufacturing environments. Additionally, the setup and calibration of these toolsrequire specialized expertise and resources, which can increase the overall manufacturing overhead.

[0024] As with manufacture of optical gratings, the necessity of careful attention to detail and precision in the production of multi-element lenses demands careful presents many challenges ranging from cost constraints to environmental robustness. As manufacturers strive to balance performance with practicality, innovative solutions are crucial to overcoming these difficulties and driving progress in optical technology. Some examples of remaining challenges in production of multi-element lenses include:

[0025] Cost efficiency: Traditional manufacturing methods for multi-element lenses often entail high expenses due to complex processes and specialized equipment. Finding cost- effective alternatives is imperative to make advanced optical technology more accessible to a broader audience.

[0026] Simplicity of assembly: Simplifying the assembly process of multi-element lenses can streamline production workflows, reduce manufacturing time, and minimize the risk of errors, ultimately leading to more efficient and scalable manufacturing practices.

[0027] High tolerance requirements: Meeting stringent tolerance requirements for precise optical alignment is essential for achieving optimal performance in multi-element lenses. Innovative solutions must address this need while offering practical and feasible approaches to ensure consistent optical quality.

[0028] Robustness to environmental factors: Multi-element lenses must exhibit robustness to environmental factors such as temperature variations, humidity, and mechanical stress to maintain performance reliability under diverse operating conditions. Developing manufacturing techniques that enhance the resilience of lenses to these factors is critical for expanding their practical utility.

[0029] Additive manufacturing (3D printing) has emerged as a promising solution for these challenges due to its potential for high precision and versatility. However, until now, no 3D printing technology has been able to achieve the nano-scale layer thickness and resolution required for fabricating optics gratings or for production of compound lenses, which also require that the surfaces thereof have sub-micron scale smoothness. This limitation has prevented the adoption of 3D printing in this area, despite its many advantages. Overcoming this barrier would enable the production of high-quality optical elements with greater efficiency and lower costs. It is thus clear that an improved method for fabrication of optical elementssuch as gratings and compound lenses, in particular a method based on the principles of additive manufacturing, remains a long-felt, but as yet unmet need.SUMMARY OF THE INVENTION

[0030] The invention disclosed herein is designed to meet this long-felt need. A method of additive manufacture of optical elements, particularly gratings and multi-element lenses, and optical coatings is disclosed, in which the optical element or coating is produced in a layer-by- layer fashion in which each layer is produced from deposition of droplets optical material on a substrate in which the droplets have a typical thickness of less than 10 nm - hundreds of nm and a diameter of 0.8 - 600 pm.

[0031] It is therefore an object of this invention to disclose a printing method for additive manufacture of an optical element, an optical coating, or combination thereof, wherein said method comprises fabricating said optical element, optical coating, or combination thereof by sequential deposition by said printing process of layers of material, said layers characterized by a thickness of <600 nm.

[0032] It is a further object of this invention to disclose the printing method as defined in the preceding, wherein said printing process is selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, dry etching, wet etching, spin-coating, and any combination thereof.

[0033] It is a further object of this invention to disclose the printing method as defined in any of the preceding, wherein said optical element is a grating, and said method comprises:

[0034] printing a grating period in a space defined by support material, said step of printing a grating period comprising: printing grating active material as droplets characterized by a diameter of 800 nm - 800 pm and a thickness of <600 nm in said space, thereby producing a grating line; repeating said step of printing grating active material until said grating line reaches a predetermined thickness; printing additional droplets of support material as needed to maintain said support material at a height greater than that of said grating material; and, printing grating spacer material as droplets characterized by a thickness of < 600 nm on top of said grating active material; and,

[0035] repeating said step of printing a grating period until a predetermined number of grating periods have been produced, thereby producing a grating structure.

[0036] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating and said step of printing a grating period is preceded by a step of obtaining at least part of a support material, said step of obtaining at least part of a support material selected from the group consisting of: (a) printing one droplet of a support material on a substrate; printing two droplets of a support material on a substrate, said two droplets separated by a separation larger than the required grating height structure; (b) obtaining a pre-prepared support structure on a substrate, said pre -prepared support structure characterized by a structure comprising support material separated by a separation larger than the required grating height structure; and, (c) obtaining a pre-prepared support structure and printing within said pre -prepared support structure printing two droplets of a support material on a substrate, said two droplets separated by a separation larger than the required grating height structure. In some preferred embodiments of the invention, said support material is said grating active material.

[0037] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, and said step of printing a grating period is followed by: removing said substrate; rotating said grating by 90° about an axis parallel to a plane defined by said support material such that said support material is on top and on bottom of said grating structure; and, polishing at least one side of said grating structure selected from the group consisting of said top and said bottom, thereby obtaining a grating.

[0038] In some preferred embodiments of the invention in which said method comprises a step of polishing, said step of polishing comprises polishing one of said top and said bottom of said grating structure. In some especially preferred embodiments of the invention, said grating spacer material is a material that can be removed by etching, and step of polishing is followed by a step of removing said grating spacer material by etching.

[0039] In some preferred embodiments of the invention in which said method comprises a step of polishing, said step of polishing comprises polishing both said top and said bottom of said grating structure. In some especially preferred embodiments of the invention, said step of polishing comprises polishing by using CMP.

[0040] In some preferred embodiments of the invention in which said method comprises a step of polishing, said step of polishing comprises retaining sufficient support material on at least one side of said grating so as to permit mounting of said grating or integration of said grating into an existing structure.

[0041] In some preferred embodiments of the invention in which said method comprises a step of polishing, said substrate is maintained throughout said steps of printing in an orientation in which said substrate is not perpendicular to a direction of travel of material being deposited by said printing process; and, said step of polishing comprises polishing said top and said bottom of said structure in parallel to a main axis of said grating structure, thereby producing a tangent tooth wave grating.

[0042] In some preferred embodiments of the invention in which said method comprises a step of polishing, wherein said step of polishing comprises polishing at an angle not parallel to a main axis of said structure, thereby producing a tangent tooth wave grating.

[0043] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said grating active material comprises a suspension of nanoparticles in a carrier. In some preferred embodiments of the invention, said nanoparticles comprise nanoparticles of at least one substance selected from a group consisting TiC particles, SiC particles, and any mixture or combination thereof, and said carrier is selected from the group comprising l-methoxy-2-propanol (PGME), 1-methoxy- 2-propanol acetate (PGMEA), isopropyl alcohol (IPA), water, and any mixture or combination thereof. In some preferred embodiments of the invention, said nanoparticles are characterized by a mean diameter of about 20 nm. In some other preferred embodiments of the invention, said nanoparticles are characterized by a mean diameter of about 10 nm. In some preferred embodiments of the invention, said carrier is PGMEA.

[0044] In some preferred embodiments of the invention in which said grating active material comprises a suspension of nanoparticles in a carrier, said carrier comprises at least one additional component selected from the group consisting of surfactants, dispersants, and combinations and mixtures thereof. In some preferred embodiments of the invention, said at least one additional component comprises a poloxamer surfactant. In some preferred embodiments of the invention, said carrier comprises a combination or mixture of a plurality of substances characterized by different evaporation rates. In some preferred embodiments of the invention, said step of printing grating active material comprises a step of evaporating said carrier in a two-stage evaporation process in which a more rapidly evaporating carrier substance evaporates first, causing said droplet containing said grating material to shrink, followed by evaporation of a more slowly evaporating carrier substance. In some preferred embodiments of the invention, said carrier comprises a mixture of 5 - 50% (v / v) IPA and the remainder PGMEA. In some preferred embodiments of the invention, said suspensioncomprises 0.25% - 1.5% by weight of said nanoparticles. In some especially preferred embodiments of the invention, said suspension additionally comprises a UV curable polymerA

[0045] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said substrate is made from glass.

[0046] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said step of repeating said step of printing a grating period comprises printing grating periods that vary in width along a dimension of said grating structure.

[0047] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said step of printing said grating material comprises varying said grating material along an axis of said grating structure.

[0048] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein: said step of printing two droplets of a support material comprises printing two droplets of a support material on a substrate, said two droplets separated by a separation sufficient to allow printing of a plurality of droplets of said active material and said spacer material within said separation; and, said method further comprises cutting and polishing said grating structures vertically, thereby obtaining multiple grating objects.

[0049] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said method further comprises mounting said grating on eyeglass optics in order to provide augmented reality transparent optics.

[0050] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said grating is a nanoscale device suitable for use in an application selected from the group consisting of optics filters, semiconductor devices, meta-optics devices, and biological nano structured devices.

[0051] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said method is a method for producing a 2D grating, and said method comprises at least one step selected from the group consisting of: using more than one active material; and, varying a total thickness of active material in different locations in said grating.

[0052] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said step of printing said active material comprises at least one step selected from the group consisting of: printing said droplets sequentially in sparse layers, each additional layer printed prior to complete drying of the layer preceding it in said sequence; printing said droplets sequentially in layers and drying each layer prior to printing a succeeding layer in said sequence; and, printing said droplets sequentially in layers and curing each layer by exposure to UV light prior to printing a succeeding layer in said sequence.

[0053] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said step of printing said active material comprises: printing said droplets so as to obtain layers, said step of printing said droplets so as to obtain layers comprising at least one layer obtained according a sequence of steps comprising: printing a sparse layer of active material in a predetermined geometry, said layer comprising droplets characterized by a predetermined volume; and, printing a second sparse layer of active material, said layer comprising droplets characterized a volume sufficient to fill in gaps left in said sparse layer of active material.

[0054] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said printing process is LIFT. In some preferred embodiments of the invention, the method further comprises a step of vibrating a LIFT print head during at least one step of printing. In some preferred embodiments of the invention, the method further comprises a step of vibrating a LIFT receiving substrate, n some preferred embodiments of the invention, said step of vibrating comprises vibrating so as to create a standing wave of said material on said receiving substrate.

[0055] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said method additionally comprises printing a coating on top of said grating structure. In some preferred embodiments of the invention, said step of printing a coating on top of said grating structure comprises printing coating material by sequential deposition of layers of said coating material by a printing process for printing coating material, said layers characterized by a thickness of <600 nm. In some preferred embodiments of the invention, said printing process for printing coating material is selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, dry etching, wet etching, spin-coating, and any combination thereof. In some especially preferred embodiments of the invention, said printing process forprinting coating material is LIFT. In some preferred embodiments of the invention in which the printing process comprises lift, it further comprises a step of vibrating a LIFT print head during at least one step of printing. In some preferred embodiments of the invention in which the printing process comprises lift, it further comprises a step of vibrating a LIFT receiving substrate. In some especially preferred embodiments of the invention, said step of vibrating comprises vibrating so as to create a standing wave of said material on said receiving substrate. In some preferred embodiments of the invention in which the method comprises a step of printing coating material, said coating is an anti -reflection coating.

[0056] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a grating, wherein said support structure is characterized by material and dimensions that make it suitable for use as an optical element. In some preferred embodiments of the invention, said support structure is characterized by material and dimensions that make it suitable for at least one use selected from the group consisting of waveguide, diffuser, spectral filter, physical filter, polarizer, and any combination thereof.

[0057] It is a further object of this invention to disclose the method for additive manufacture of an optical element, an optical coating, or combination thereof, wherein said method comprises fabricating said optical element, optical coating, or combination thereof by sequential deposition by said printing process of layers of material, said layers characterized by a thickness of <600 nm as defined in the preceding, wherein said optical element is a compound lens comprising a plurality of subsidiary optical elements.

[0058] It is a further object of this invention to disclose the method as defined in the preceding in which said optical element is a compound lens comprising a plurality of subsidiary optical elements, wherein said printing process is selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, dry etching, wet etching, spin-coating and any combination thereof.

[0059] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a compound lens comprising a plurality of subsidiary optical elements, wherein said method comprises printing said compound lens so as to leave a gap between two successive subsidiary layers.

[0060] It is a further object of this invention to disclose the method as defined in the preceding in which said optical element is a compound lens comprising a plurality of subsidiary opticalelements, wherein said method comprises printing a coating on at least one side of at least one of said subsidiary optical elements.

[0061] It is a further object of this invention to disclose the method as defined in the preceding in which said optical element is a compound lens comprising a plurality of subsidiary optical elements, wherein at least two of said subsidiary elements are characterized by different refractive indices.

[0062] It is a further object of this invention to disclose the method as defined in the preceding in which said optical element is a compound lens comprising a plurality of subsidiary optical elements, wherein said material comprises a suspension of nanoparticles in a carrier. In some preferred embodiments of the invention, said nanoparticles comprise nanoparticles of at least one substance selected from a group consisting TiC particles, SiC particles, and any mixture or combination thereof, and said carrier is selected from the group comprising 1 -methoxylpropanol (PGME), l-methoxy-2-propanol acetate (PGMEA), isopropyl alcohol (IPA), water, and any mixture or combination thereof. In some preferred embodiments of the invention, said nanoparticles are characterized by a mean diameter of about 20 nm. In some other preferred embodiments of the invention, said nanoparticles are characterized by a mean diameter of about 10 nm. In some preferred embodiments of the invention, said carrier is PGMEA.

[0063] In some preferred embodiments of the method in which said optical element is a compound lens comprising a plurality of subsidiary optical elements, and said material comprises a suspension of nanoparticles in a carrier, said carrier comprises at least one additional component selected from the group consisting of surfactants, dispersants, and mixtures and combinations thereof. In some especially preferred embodiments, said at least one additional component is a poloxamer surfactant. In some preferred embodiments, carrier comprises a combination or mixture of a plurality of substances characterized by different evaporation rates.

[0064] It is a further object of this invention to disclose the method as defined in any of the preceding in which said optical element is a compound lens comprising a plurality of subsidiary optical elements and said material comprises a suspension of nanoparticles in a carrier, wherein at least one step of printing comprises a step of evaporating said carrier in a two-stage evaporation process in which a more rapidly evaporating carrier substance evaporates first, causing said droplet containing said grating material to shrink, followed by evaporation of a more slowly evaporating carrier substance. In some preferred embodiments of the invention,said carrier comprises a mixture of 5 - 50% (v / v) IPA and the remainder PGMEA. In some preferred embodiments of the invention, said suspension comprises 0.25% - 1.5% by weight of said nanoparticles.

[0065] It is a further object of this invention to disclose the method as defined in the preceding in which said optical element is a compound lens comprising a plurality of subsidiary optical elements, wherein said step of producing said compound lens comprises sequentially depositing layers of material comprising droplets characterized by a diameter of between 30 and 800 pm.

[0066] It is a further object of this invention to disclose the method as defined in the preceding in which said optical element is a compound lens comprising a plurality of subsidiary optical elements, wherein said printing process is LIFT. In some preferred embodiments of the invention in which said printing process is LIFT, the method further comprises a step of vibrating a LIFT print head during at least one step of printing. In some preferred embodiments of the invention in which said printing process is LIFT, the method further comprises a step of vibrating a LIFT receiving substrate. In some especially preferred embodiments, said step of vibrating comprises vibrating so as to create a standing wave of said material on said receiving substrate.

[0067] It is a further object of this invention to disclose the method for additive manufacture of an optical element, an optical coating, or combination thereof, wherein said method comprises fabricating said optical element, optical coating, or combination thereof by sequential deposition by said printing process of layers of material, wherein said method is a printing method for additive manufacture of an optical coating, and further wherein said method comprises fabricating said optical coating by sequentially depositing by said printing process of layers of optical coating material, said layers characterized by a thickness of <600 nm.

[0068] It is a further object of this invention to disclose the method as defined in the preceding in which said method is a method for additive manufacture of an optical coating, wherein said printing process is selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, dry etching, wet etching, spin-coating and any combination thereof.

[0069] It is a further object of this invention to disclose the method as defined in the preceding in which said method is a method for additive printing of an optical coating, wherein saidmaterial comprises a suspension of nanoparticles in a carrier. In some preferred embodiments of the invention, said nanoparticles comprise nanoparticles of at least one substance selected from a group consisting TiC particles, SiC particles, and any mixture or combination thereof, and said carrier is selected from the group comprising l-methoxy-2-propanol (PGME), 1- methoxy-2-propanol acetate (PGMEA), isopropyl alcohol (IP A), water, and any mixture or combination thereof. In some preferred embodiments of the invention, said nanoparticles are characterized by a mean diameter of about 20 nm. In some other preferred embodiments of the invention, said nanoparticles are characterized by a mean diameter of about 10 nm. In some preferred embodiments of the invention, said carrier is PGMEA.

[0070] It is a further object of this invention to disclose the method as defined in any of the preceding in which method is a method for additive printing of an optical coating and said material comprises a suspension of nanoparticles in a carrier, wherein at least one step of printing comprises a step of evaporating said carrier in a two-stage evaporation process in which a more rapidly evaporating carrier substance evaporates first, causing said droplet containing said grating material to shrink, followed by evaporation of a more slowly evaporating carrier substance. In some preferred embodiments of the invention, said carrier comprises a mixture of 5 - 50% (v / v) IPA and the remainder PGMEA. In some preferred embodiments of the invention, said suspension comprises 0.25% - 1.5% by weight of said nanoparticles.

[0071] It is a further object of this invention to disclose the method as defined in any of the preceding in which method is a method for additive printing of an optical coating, wherein said step of fabricating said optical coating by sequentially depositing layers of optical material comprises sequentially depositing droplets characterized by a diameter of between 30 and 800 pm.

[0072] It is a further object of this invention to disclose the method as defined in any of the preceding in which method is a method for additive printing of an optical coating, wherein said printing process is LIFT. In some preferred embodiments, the method additionally comprises a step of vibrating a LIFT print head during at least one step of printing. In some preferred embodiments, the method additionally comprises a step of vibrating a LIFT receiving substrate. In some especially preferred embodiments, said step of vibrating comprises vibrating so as to create a standing wave of said material on said receiving substrate.

[0073] It is a further object of this invention to disclose a system for fabricating an optical element, an optical coating, or a combination thereof by sequential deposition of layers of material characterized by a thickness of <600 nm, said system comprising substrateless and / or local donor Laser Induced Forward Transfer (LIFT), said substrateless and / or local donor Laser Induced Forward Transfer (LIFT) comprising: (a) a reservoir comprising at least one opening; (b) at least one printing head in fluid connection with said reservoir; (c) an energy source configured to deliver energy to a donor material within said reservoir and thereby initiate a LIFT process; and, (d) a receiving substrate disposed such that material exiting said reservoir will impinge on said substrate, wherein said system comprises: (i) printing means configured to print a grating structure in a space defined by a support material by a process comprising: (A) printing grating active material as droplets characterized by a diameter of 800 nm - 800 pm and a thickness of <600 nm in said space, thereby producing a grating line; (B) repeating said step of printing grating active material until said grating line reaches a predetermined thickness; (C) printing additional droplets of support material as needed to maintain said support material at a height greater than that of said grating material; and, (D) printing grating spacer material as droplets characterized by a thickness of < 600 nm on top of said grating active material; and, (ii) repeating said step of printing a grating period until a predetermined number of grating periods have been produced, thereby producing a grating structure.

[0074] It is a further object of this invention to disclose the system as defined in the preceding, wherein said system further comprises at least one vibrating means selected from the group consisting of: a first vibrating means in mechanical connection with said at least one printing head, said vibrating means configured to cause said at least one printing head to vibrate; and, a second vibrating means in mechanical connection with said receiving substrate, said second vibrating means configured to cause said receiving substrate to vibrate.

[0075] It is a further object of this invention to disclose the system as defined in the preceding, wherein said system comprises said second vibrating means, and said second vibrating means is configured to vibrate said receiving substrate so as to produce a standing wave of said material on said receiving substrate.

[0076] It is a further object of this invention to disclose the system as defined in any of the preceding, wherein said at least one printing head is disposed between said energy source and said receiving substrate, and said printing head comprises a microfluidic chip (MFC), said MFC comprising three regions: (a) an upper region; (b) a middle region comprising: at least one ink channel passing through said MFC, said at least one ink channel comprising an ink channelinlet and an ink channel outlet; at least one intermediate layer channel passing through said MFC, said at least one intermediate layer channel comprising an intermediate layer channel inlet and an intermediate layer channel outlet; and, a fluid connection within said MFC between said at least one ink channel and said at least intermediate layer channel; and, (c) a lower region, said lower region comprising an orifice in fluid connection with said ink channel, said orifice oriented such that fluid exiting said orifice will travel toward said receiving substrate; said at least one ink channel and said at least one intermediate layer channel being disposed at said fluid connection such that said ink channel lies between said intermediate layer channel and said orifice; an ink reservoir in fluid connection with said ink channel inlet; and, an intermediate layer material reservoir in fluid connection with said intermediate layer channel inlet.

[0077] It is a further object of this invention to disclose the system as defined in any of the preceding, wherein said energy source is a pulsed laser.

[0078] It is a further object of this invention to disclose the system as defined in any of the preceding, additionally comprising energy transfer means for transferring energy from said energy source to a donor material within said reservoir. In some preferred embodiments of the invention, said energy transfer means comprise a waveguide.

[0079] It is a further object of this invention to disclose the system as defined in any of the preceding, additionally comprising temperature regulating means for regulating temperature of material within said reservoir.

[0080] It is a further object of this invention to disclose the system as defined in any of the preceding, wherein said reservoir is disposed within said at least one printing head.

[0081] It is a further object of this invention to disclose the system as defined in any of the preceding, further comprising flow means for providing a continuous flow of material through said reservoir.

[0082] It is a further object of this invention to disclose the system as defined in any of the preceding, further comprising a feedback mechanism that supports at least one of calibration, synchronization, alignment, and process control of said system.

[0083] It is a further object of this invention to disclose the system as defined in any of the preceding, further comprising a sensor configured to measure at least one parameter of material printed by said system, and provides feedback to at least one system selected from the group consisting of process control, sintering, and curing.BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The invention will now be described with reference to the drawings, wherein:

[0085] FIG. 1 schematically illustrates the basic Laser-Induced Forward Transfer process known in the prior art;

[0086] FIG. 2 schematically illustrates one non-limiting embodiment of Substrateless Laser- Induced Forward Transfer as known in the prior art;

[0087] FIGs. 3A and 3B schematically illustrate one non-limiting embodiment of Local Donor Laser Indicued Forward Transfer as known in the prior art;

[0088] FIGs. 4A and 4B schematically illustrate one non-limiting embodiment of a LIFT system that incorporates a microfluidic chip as a LIFT head, with FIG. 4A showing a schematic cross-sectional view and FIG. 4B showing a schematic three-dimensional view illustrating the flow of ink through the microfluidic chip, respectively;

[0089] FIG. 5 is a graph comparing a theoretical model of the maximum material thickness that can be deposited by a Laser-Induced Forward Transfer process as a function of material viscosity with experimental measurements;

[0090] FIGs. 6A - 6C are electron microscope images of nanoparticles deposited by the method disclosed herein;

[0091] FIG. 7 is a schematic depiction of the essential steps in method of fabrication of a grating according to one non-limiting embodiment of the invention disclosed herein;

[0092] FIG. 8 is a schematic depiction of a grating structure obtained from one non-limiting embodiment of the method disclosed herein;

[0093] FIG. 9 is a schematic depiction of the grating structure of FIG. 8 after removal from the substrate and rotation by 90°;

[0094] FIG. 10 is a schematic depiction of a grating obtained after polishing of the structure depicted in FIG. 9;

[0095] FIG. 11 is a schematic depiction of fabrication of a tangent grating according to one non-limiting embodiment of the method disclosed herein;

[0096] FIG. 12 is a schematic depiction of fabrication of a tangent grating according to a second non-limiting embodiment of the method disclosed herein; and,

[0097] FIG. 13 is a schematic depiction of a 2D grating obtained by one non-limiting embodiment of the method disclosed herein.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0098] In the following description, various aspects of the invention will be described. For the purposes of explanation, specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent to one skilled in the art that there are other embodiments of the invention that differ in details without affecting the essential nature thereof. Therefore, the invention is not limited by that which is illustrated in the figures and described in the specification, but only as indicated in the accompanying claims, with the proper scope determined only by the broadest reasonable interpretation of said claims. In some cases, for clarity or conciseness, individual elements of the invention are discussed separately. Nonetheless, any combination of individual elements of the invention disclosed herein that is not self-contradictory is considered by the inventors to be within the scope of the invention.

[0099] In all cases in which an embodiment is described as "comprising" a set of components or method steps, i.e. the invention may include components or method steps in addition to those explicitly listed, the scope of invention is to be understood to include embodiments in which the invention "consists of" the listed components or method steps, i.e. embodiments that include the listed components or method steps and no others, and to include as well embodiments in which the invention "consists essentially of" the listed components or method steps, i.e. embodiments that do not include any components or method steps not listed that would materially affect the basic and novel characteristics of the invention. In the instant disclosure and claims, the terms “comprising”, “including”, and “having” are used interchangeably.

[0100] Unless specifically stated otherwise, any range disclosed herein is understood to include within its scope the endpoints of the range as well as any subrange. As non-limiting examples, if a range is stated to be "1 - 10%, " unless stated otherwise, values of 1% and 10% and ranges of 1 - 5%, 2 - 9%, etc., are all considered by the inventors to be within the scope of the invention. Similarly, as a non-limiting example, if a range is stated to be "less than 50%, " ranges of less than 40%, less than 25%, less than 10%, etc., are considered by the inventors to be within the scope of the invention.

[0101] As used herein, unless defined otherwise, with reference to numerical quantities, the term "about" refers to a range of ±25% about the nominal value.

[0102] As used herein, the acronym "LIFT" is used to stand for "Laser-Induced ForwardTransfer."

[0103] As used herein, the acronym “LD-LIFT” is used to represent “local donor laser-induced forward transfer”.

[0104] As used herein, the acronym “SL-LIFT” is used to represent “substrateless laser- induced forward transfer.”

[0105] As used herein, with reference to LIFT printing, the term "ink" refers to any substance that is expelled from a LIFT printing device toward a receiving substrate.

[0106] As used herein, with reference to LIFT printing, the term "inkjet" refers to ink expelled from a LIFT device to be deposited on a substrate. The "jet" may comprise a continuous stream of ink or one or more droplets. With reference to deposition of droplets of material via LIFT, the terms "deposition" and "printing" are used interchangeably.

[0107] As used herein, the acronym "MFC" is used to represent "Microfluidic Chip."

[0108] As used herein, the acronym "PGME" is used to represent "propylene glycol methyl ether" (l-methoxy-2-propanol).

[0109] As used herein, the acronym "PGMEA" is used to represent "propylene glycol methyl ether acetate" (l-methoxy-2-propanol acetate).

[0110] As used herein, the acronym "CMP" is used to represent "Chemical-Mechanical Polishing."

[0111] As used herein, the acronym "IPA" is used to represent "isopropyl alcohol."

[0112] As used herein, the acronym “PW” is used to represent "pulse width."

[0113] As used herein, the acronym “PRR” is used to represent "pulse repetition rate."

[0114] As used herein, the acronym “PRF” is used to represent "pulse repetition frequency."

[0115] As used herein, the term "sparse" is used to describe a layer of droplets in which the spacing between the centers of nearest neighbor droplets is greater than the droplet diameter.

[0116] The term “calibration” is used herein to refer to the accuracy and orientation of the head in the system; and to the calibration of head parameters such as laser power, laser PW, laser PRF, heating and cooling temperatures, speed of movement of the waveguide, etc.

[0117] The invention disclosed herein provides a novel method for fabrication of optical elements, particularly gratings and multi-element lenses, and coatings for optical components such as lenses by additive manufacture. In preferred embodiments of the invention, the additive manufacturing process is performed using one or more printing methods selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, inkjet, screen printing, exposure -based patterning systems, dry etching, wet etching, and spincoating.

[0118] While the following disclosure presents detailed descriptions of some non-limiting embodiments of the inventive method in which printing or deposition of droplets is performed by LIFT, a person of ordinary skill in the art will readily understand that the principles of the method can easily be adapted for use in any other technology such as those listed above that is capable of deposition or printing of droplets of the appropriate size. The LIFT process consists of material to be transferred (the "donor material"), which is facing a receiver substrate (the "acceptor"). A laser pulse locally induces a thermal excitation that finally results in material transfer towards the acceptor. The donor may be located on a thin substrate from which it evaporates, or within a reservoir or MFC, from which it is expelled through a small orifice. In some cases in which the donor material is located within a reservoir or MFC, it is renewed by flow of new material.

[0119] The basic principles of the LIFT technique are well-known, and have been described in detail in, for example, U.S. Pat. Nos. 9446618, 9751371, and 10668762, the disclosures of which are incorporated in their entirety. While any LIFT method known in the art may be used as the basic method of fabricating the optical elements and coatings described herein, in order to assist a person of ordinary skill in the art to make and use the invention disclosed herein, a brief summary is now presented of some non-limiting exemplary embodiments of the LIFT technique that can be used, with the modifications disclosed herein, to produce the optical elements and coatings of the instant invention.

[0120] Reference is now made to FIG. 1, which schematically illustrates the basic LIFT process as it is known in the prior art. a transparent substrate (1) is coated with a thin film of the transferred material (3, the “donor”). A layer of donor material 3 faces the receiver substrate (7, the “acceptor”). There may be an intermediate layer between the substrate and donor layers. A laser pulse (4) induces a local thermal excitation that results in rapid heat transfer to the donor material, generating a gas bubble (5) at the predefined focus point. The gas bubblerapidly travels to the surface and injects a droplet (6) from the boundary between the donor material and the ambient environment to the surface of the acceptor.

[0121] In some non-limiting embodiments of the invention disclosed herein, substrateless LIFT (SL-LIFT) is used to deposit the droplets. In SL-LIFT, the donor material itself is used as the donor substrate. Reference is now made to FIG. 2, which illustrates schematically (not to scale) one embodiment an SL-LIFT system knowin in the prior art. A reservoir (9) contains the donor material (10). An energy source or means for transferring energy from an energy source is disposed so as to be able to transfer energy to the donor material within the reservoir. In the embodiment shown in FIG. 2, the energy source is a laser external to the reservoir, the light from which is transferred to the donor material via a waveguide (8). Any other appropriate energy source known in the art can be used, however. Non-limiting examples of energy sources used in embodiments of the invention not illustrated in FIG. 2 include an electric arc or electronic resistance mechanism. The reservoir comprises at least one opening 9b that enables material to exit. While the size of the opening is not critical to the operation of the system, in typical embodiments, it much larger than nozzles in typical inkjet printing heads. The increased size of the opening relative to those typically found in inkjet printing heads enables flow of large particles and of viscous materials without clogging the system. In preferred embodiments, the opening's largest dimension D4 (or diameter in embodiments in which it is circular) is at least 100 pm, and may range up to several mm. In order to enable refilling of the reservoir without loss of material during the refilling, in preferred embodiments, the reservoir is provided with a stopper 9a. A person of ordinary skill in the art would readily understand how to adapt other embodiments of SL-LIFT that are well-known in the art for use in the invention disclosed herein.

[0122] In some embodiments of the invention disclosed herein, "Local Donor" LIFT (LD- LIFT) is used. In the LD-LIFT process, the substrate is effectively reduced in size to the point where only that part of the substrate and donor material heated by the laser remained (-20 microns surrounding the laser spot). Reference is now made to FIG. 3A, which illustrates this case schematically (not to scale). In such a case, the standard LIFT process would continue to operate since the interaction between the energy source and the material 206 that is plated or coated on the donor substrate 205, and the consequent LIFT process, will be the same as in the standard prior art LIFT setup shown in FIG. 1.

[0123] Reference is now made to FIG. 3B, which illustrates schematically one embodiment of LD-LIFT, in which donor material 215 is embedded in or is part of the reservoir or flowsthrough it. The fundamental physical interaction between the energy source and the donor material will thus be the same as that shown in FIG. 3A and hence the same as in the standard LIFT shown in FIG. 1, demonstrating that a LIFT process will occur under conditions in which the material resides in or flows through the reservoir, even lacking a donor substrate. The invention herein disclosed incorporates introduction of the local donor or donors into a reservoir (215), which continues to support a standard LIFT mechanism, thus deriving a “local donor LIFT” method and systems thereof. Reservoir (215) may incorporate a flow of material, thereby refreshing the local donor (205) and enabling high frequency and continuous printing.

[0124] As was mentioned above, in some non-limiting preferred embodiments of the invention, the optical element or coating is produced by a LIFT process in which the printing head is, or is incorporated into, an MFC. Such systems are well-known in the art. Reference is now made to FIG. 4, which presents a schematic diagram (not to scale) of a typical embodiment 30 of a LIFT system of the present invention. A cross sectional view of the system is shown in FIG. 4A, while FIG. 4B is a three-dimensional view that illustrates the direction of flow of ink through the MFC. In the embodiment illustrated in FIG. 4, the system comprises an MFC 300 which serves as the LIFT head, and a receiving substrate 350. The MFC comprises three regions: a relatively thick upper region 320, which is typically a few mm thick; a relatively thin middle region 330 that comprises at least one ink channel 3300, each ink channel having an inlet 3301 for introducing a flow of ink into the ink channel and an outlet 3302 from which the flow of ink exits the ink channel; and a relatively thin bottom region 340 that includes an orifice 365 facing the receiving substrate; in some other embodiments of the invention, not shown in the figure, the orifice is placed at the side of the MFC rather than at the bottom. The terms "upper," "middle," and "lower" are used for convenience and do not necessarily define the absolute positions of the three regions.

[0125] The upper region is substantially transparent at the wavelength of the laser output. That is, enough light passes through the upper region such that the light impinging on the ink retains enough energy such that absorption of the energy by the ink is sufficient to produce an ink jet that exits the orifice. In some embodiments of the invention, the MFC is constructed such that sufficient energy will impinge on the ink to sufficient evaporate enough ink to produce a vapor bubble that will, upon collapse, provide a pressure transient sufficiently great to force ink out of the orifice in the direction of the receiving substrate. In other embodiments of the invention, the MFC is constructed such that absorption of the energy is sufficient to create a pressure wave that propagates through the ink, thereby resulting in a deformation of the ink-air interfaceat the orifice and subsequent expulsion of ink from the orifice, creating an inkjet. In yet other embodiments of the invention, sufficient energy passes through the upper region to cause ablation of the ink, thereby expelling ink from the orifice and creating an inkjet.

[0126] The sizes of the channels are optimized for the particular material being used. In typical embodiments of the invention, the height of the channel is between 20 pm and 1 mm, and the width is between 50 pm and 3 mm. As a general rule, a smaller channel height will result in smaller droplets being ejected as the inkjet, and will require less energy per pulse than a taller channel would need. On the other hand, if the ink is highly viscous, a channel having smaller dimensions will result in a larger pressure drop across the channel, especially in the cases of highly viscous inks flowing through the MFC at a high velocity, which can lead to clogging of the ink in the channel.

[0127] In typical embodiments of the invention, connections between channel inlets and outlets and external tubes are made by standard microfluidic connectors. Embodiments in which the inlet and outlet are configured to connect to different types of connectors are considered by the inventor to be within the scope of the invention. The external tubes provide a fluid connection between the MFC and at least one pump that creates the flow of ink through the channel. Nonlimiting examples of the types of pumps that can be used with the MFC head disclosed herein include peristaltic, pressure, and syringe pumps. The required flow rate of the ink will depend on the required refresh rate, which depends inter alia on the droplet sizes in the ink jet and the desired printing rate. In typical embodiments of the invention, the flow rate through the channel is between 0.1 mm s'1and 1 m s'1.

[0128] Non-limiting examples of additional optional components that can be included in the EIFT system disclosed herein include an air trap, pressure sensors, pressure regulators, valves, and temperature control apparatus.

[0129] In a typical EIFT process using this system, laser output 310 is focused on the ink channel opposite the orifice and directed to the ink channel via the upper region. The laser light is at least partially absorbed by ink in the channel, which then evaporates, forming a bubble of vapor that, upon collapse, causes the transient pressure increase that creates ink jet 345 that passes through orifice 365 toward the receiving substrate, where it is deposited (355). In contrast to normal LIFT processes, however, in the instant invention, fresh sample is brought before the laser by the aforementioned flow of ink through the ink channel rather than by movement of the LIFT head or laser.

[0130] As shown in FIG. 4, the MFC LIFT head does not incorporate an intermediate layer as is found in standard LIFT. Rather, the energy used to produce the vapor bubble is focused on the material within the ink channel. Thus, in preferred embodiments of the invention, in which the energy source is a pulsed laser, the ink comprises a material that absorbs light at the output wavelength of the laser. The wavelength, polarization, and mode distribution of the laser light are restricted only by the requirement that the absorption coefficient for absorption of the laser output by the ink must be sufficiently high that a single laser pulse is sufficient to at least partially evaporate the ink that absorbs the light in order to create the vapor bubble and eventually the ink jet that exits the MFC via the orifice. In preferred embodiments of the invention, the absorption coefficient of the ink at the laser wavelength is at least 1000 cm’1.

[0131] A person of ordinary skill in the art will well understand how to adapt other embodiments of MFC-based LIFT known in the art for use with the invention disclosed herein.

[0132] In some non-limiting preferred embodiments of the method disclosed herein, a novel modification of LIFT is used to produce droplets that are typically 0.8 - 800 pm in diameter and have a controllable thickness of <600 nm that in typical embodiments is on the order of tens of nm. The method disclosed herein meets the challenge of obtaining submicron lateral resolution with droplets that have typical diameters of on the scale of 10 pm. The method has several advantages compared to inkjet and other printing and deposition technologies. LIFT technology supports printing and deposition of significantly broader range of materials and is widely more flexible in terms of material viscosity, surface tension, particle size and sensitivity to shear forces.

[0133] Achieving droplets of this size of active material with 3D printing, particularly by LIFT, is possible with the present technology by means of engineering the process parameters. The present technology enables flexibility in setting process parameters. Non-limiting examples of process parameters that can be varied according to need include, but are not necessarily limited to, volume of the printed droplets, concentration of the active material within the ink solvent, solvent type, the dynamic behavior of the droplet on its way to the substrate, the behavior of the droplet on the substrate and the drying of the droplet on the substrate, temperature of the substrate and environment, vapor pressure in the LIFT system, and degree of drying or curing prior to deposition of successive steps.

[0134] Further non-limiting examples of process parameters that can be varied according to need include controlling droplet behavior on the substrate, and the drying behavior. Non-limiting examples of control of the drying behavior include example, by plasma activation of the surface before printing, control of substrate and ambient temperature, and control of ambient vapor pressure. To create nanometric thickness droplets on a substrate using the present technology, one should create a process that will result with uniform active material on the substrate. In typical embodiments of the invention, LIFT is used to deposit droplets of a suspension of an active material in a carrier. As non-limiting example, the suspension may contain commercially available TiCL nanoparticles with an average diameter of 20 nm in PGMEA solvent ink. In some non-limiting embodiments, the receiving substrate on which the optical element is printed is made from glass. In other embodiments, other solvents or carriers can be used; a non-limiting example is PGME. Other active materials, and nanoparticles of other sizes, can be used as well in other non-limiting embodiments. Other non-limiting examples of nanoscale droplets that can be printed by the LIFT process disclosed herein include for example, water-based NBE (Nano bead emitters) ink and glycol-Ag ink.

[0135] LIFT behavior in general is described by eq (1):(a?; + )Th= EeffAb(1) where / is the viscosity of the material, a is the effective viscosity content, b is the effective kinetic energy constant, Th is the thickness of the material in the channel and orifice for delivering the material, Eeff is the laser energy in the effective footprint, and Ab is the absorption coefficient of the material being deposited.

[0136] From eq (1), it follows that the maximum thickness of material that can be deposited in a LIFT process is given by eq (2):

[0137] Reference is now made to FIG. 5, which presents a graph of the maximum thickness of material that can be deposited by a LIFT process as a function of the material's viscosity. The solid line shows the model according to eq (2), and the circles show experimental results for a variety of materials of different viscosities.

[0138] The inventors have found that, as expected from the model and shown graphically in FIG. 5, printing proceeds most easily with carriers characterized by low viscosities (typically < 1 cP), low surface tension, and high evaporation rate. Reference is now made to FIGs. 6A - 6C, which show particles of TiO2 deposited using PGMEA as the carrier, NBE deposited using water as the carrier, and Ag deposited using glycol as the carrier, respectively. FIGs. 6A and 6C were obtained from nanometric interferometry, while FIG. 6B was obtained from opticalmicroscopy. As can be seen from the pictures, the resulting particles on the substrate have diameters typically on the scale of tens of nm. Droplets printed by LIFT using carriers having these characteristics are thus thin, cover a relatively large area on the surface, and dry quickly, thereby preventing degradation of the quality of the layer due to instabilities. Moreover, as shown in FIGs. 6A - 6C, high surface tension carriers such as water and high viscosity carriers such as glycol (viscosity ~18 cP) can be used successfully in LIFT -based additive manufacture of optical components and optical coatings.

[0139] It is well known in the prior art that laser power, laser spot diameter and orifice diameter can be manipulated and optimized in order to control volume of the printed droplets. The inventors have found, surprisingly, that the height of the material above the orifice in the printing head is also a parameter that can be used to control the drop volume. Moreover, moving to a lower material height above the orifice enables printing of materials with lower absorbance at the laser output wavelength. An additional benefit of working with thin channels is that a system containing them is much more stable and robust, as it reduces the likelihood of ink breakthrough through the orifice and reduces the ability of air bubbles to enter the channel during printing. As non-limiting examples, optical devices were fabricated by LIFT processes that had 40 pm or 25 pm material heights. The inventors found, surprisingly, that when the height of the material was 25 pm, it was possible to print material through a single orifice at a repetition rate of 900 Hz.

[0140] In some non-limiting embodiments of the invention, the height of the print layer and the width and height of the orifice are optimized as part of the MFC design, as the amount of material released in each laser pulse is a function of the laser energy and the absorption of the printing material at the laser output wavelength; if the absorbance is weaker, a thinner MFC is needed.

[0141] In some non-limiting embodiments of the invention, the material for deposition by LIFT may also include a surfactant or dispersant in order to limit aggregation of the particles in the droplet. In some preferred non-limiting embodiments, a poloxamer surfactant is used. Such surfactants are commercially available under trade names such as PLURONIC. As a nonlimiting example, TiCL particles were deposited successfully using PGMEA as the carrier with the addition of 1% PLURONIC F-127 surfactant. As another non-limiting example, in one embodiment, graphene particles were deposited successfully from a carrier comprising water and PLURONIC F-127 surfactant.

[0142] In some embodiments of the invention, the droplets comprise a mixture of solvents or carriers with different evaporation rates. In these embodiments, the droplets undergo a two- stage evaporation process, in which the more rapidly evaporating solvent or carrier evaporates, causing the droplet to shrink, followed by evaporation of the lower evaporation rate solvent or carrier evaporates. The use of a mixture or combination of solvents or carriers can also aid the LIFT process in cases in which one of the components of the mixture absorbs light at the laser output wavelength much more strongly than the other. In some non-limiting embodiments, the LIFT process is used in which the ink comprises a carrier or solvent comprising a mixture of isopropyl alcohol (IPA) and PGMEA; at room temperature, IPA evaporates roughly 5 times faster than PGMEA. This carrier mixture has been found to be particularly effective for deposition of particles of refractory materials such as nanoparticles of TiO2. In some preferred non-limiting embodiments of the invention, the nanoparticles of TiO2 have an average diameter of about 20 nm. In some other preferred non-limiting embodiments of the invention, the nanoparticles of TiO2 have an average diameter of about 10 nm. In some non-limiting embodiments, the carrier comprises 5 - 50% (v / v) IPA. In some preferred non-limiting embodiments, the carrier comprises 20 - 35% (v / v) IPA.

[0143] Relevant room-temperature physical properties of the solvents are summarized in Table 1. The low viscosity and low surface tension enable the material to spread widely on the surface before the carrier evaporates. The high evaporation rate helps to stabilize the drying process and to ensure good droplet-to-droplet repeatability.Solvent Viscosity Surface Tension Evaporation Rate(mPa s) (mN / m) (Butyl Acetate = 1)Water 089 72X)IPA 2.1 21.7 -2.0PGMEA 0.95 25 - 28 -0.4

[0144] These materials cannot be printed with any other technology.

[0145] Achieving uniform active material on the substrate is achieved by setting the concentration of the nanoparticles in the ink to a value that will yield a uniform thickness layer (disk) of nanoparticles on the substrate after evaporation of the carrier. As a non-limiting example, in a case in which the droplet diameter on the substrate is 300 pm and the droplet volume is -400 pL, it would require -200 million 20 nm diameter nanoparticles to create a uniform monolayer disk characterized by a diameter of 300 pm; the concentration of the particles in the ink can easily be adjusted to obtain this number of particles in the 400 pLdroplet. The resulting concentration is less than 1% by weight and the properties of the ink are consequently very similar to those of the pure solvent. The instant invention thus provides a novel method for using LIFT printing with highly dilute materials.

[0146] As a second non-limiting example, a droplet having a diameter of 10 pm and 100 nm height has a volume of ~50 pL. In order to produce five layers of 20 nm diameter particles for a total layer height of 100 nm, the suspension needs to have a concentration of -1.5% by weight. For a single 100 nm layer, the concentration would have to be five times higher, i.e., -7.5% by weight.

[0147] In some non-limiting embodiments, the droplet diameter is between 30 and 800 pm. In some other non-limiting embodiments, the droplet diameter is between 70 and 800 pm. In some preferred non-limiting embodiments, the droplet diameter is 30, 70, 300, 500, or 800 pm. In some non-limiting embodiments, the concentration of the material to be deposited is 0.25% - 1.5% by weight for single particle layers (typical non-limiting values are 0.25%, 0.5%, and 1%), and appropriate multiples of the concentrations for multiple layers. In some non-limiting embodiments, the MFC orifice 365 is characterized by a diameter of 80 - 150 pm; typical nonlimiting values include 50, 80, 120 and 150 pm. Laser power can also be used to control the desired droplet volume. In typical non-limiting embodiments of the invention, the laser wavelength is between 0.3 andlO pm.

[0148] In some non-limiting embodiments of the invention, in cases in which the material does not inherently absorb light strongly at the laser output wavelength, vibration of the MFC is performed. The vibration alters the instantaneous shape of the meniscus, thereby increasing the laser absorption and hence the efficiency of the LIFT process where the meniscus is at its highest point.

[0149] In other non-limiting embodiments of the invention, the surface onto which the material is printed is vibrated. In printing of liquids, the primary issue of concern is the formation of flow. Vibrating the receiving substrate causes the droplet to spread out on the surface and is therefore thin and hence is less likely to flow. In addition, it is possible to create standing waves by vibration of the receiving substrate, thereby preventing flow.

[0150] The present technology provides the ability to print a highly dilute ink in a robust stable way that enables continuous stable printing of nano-scale droplets. In similar way, the working point can be adjusted or fitted for variable cases and variable materials.

[0151] A typical optical grating consists of a periodic array of lines or grooves etched or patterned onto a substrate. The structure is designed to diffract incoming light into multiple directions based on the wavelength and angle of incidence. The grating period, which is the distance between adjacent grooves, is crucial as it determines the diffraction angles and the efficiency of light separation. As is well known in the art, the grating efficiency for each diffraction order is determined inter alia by the duty cycle, geometry (blazing) of the grooves, and refraction index matching between the grading and the waveguide.

[0152] In one non-limiting embodiment, the method disclosed herein is used to produce a square wave grating. In this embodiment, a substrate is placed essentially perpendicular to the direction of travel of the material released in the LIFT process.

[0153] In the first step of this embodiment of the process, two droplets of a support material 100 are printed on a substrate 150, separated by a gap larger than the required grating height structure. In the second step, a droplet of active material 110 having a thickness of <600 nm is then printed between the support material droplets. The second step is repeated until the required thickness of the grating is obtained. If needed, additional support material droplets are printed in order to keep the support material higher than the grating active material.

[0154] In some non-limiting embodiments of the invention, rather than printing the support material, the grating can be printed using LIFT onto a pre -prepared support material. In some other non-limiting embodiments of the invention, a pre-prepared support material is used, and additional support material is printed onto the substrate as described above. In yet other nonlimiting embodiments of the invention, only one side of the grating is supported, and the other side is polished. In still other non-limiting embodiments of the invention, the grating is prepared without any support structures. In still other non-limiting embodiments of the invention, printing the grating layers is on a substrate, with no printed or pre -prepared support structures, and then cutting and / or polishing the desired grating size. In still other non-limiting embodiments of the invention, only one side is supported, on the other side the grating is polished.

[0155] It should be pointed out that, according to one embodiment, the support material printed could be the grating active material.

[0156] In the fourth step of the process, grating spacer (filling) material 120 is printed on top of the active grating material as droplets having a thickness of <600 nm. This step is repeated until the desired spacer thickness is obtained. Additional support material may be printeddropwise in order to keep the support material higher than the grating spacer material. Reference is now made to FIG. 7, which illustrates the method schematically (not to scale). For ease of viewing, successive droplets of material are shown in different shadings. It is emphasized that embodiments in which a single active material and a single spacer material are used for the grating are within the scope of the invention, as are embodiments in which more than one active material and / or more than one spacer material is used. It is also emphasized that the droplets of the different materials used in fabrication of the grating may be deposited in any sequence, not necessarily alternating.

[0157] The preceding steps are repeated until a grating structure comprising the desired number of periods (length) is obtained. Reference is now made to FIG. 8, which illustrates schematically (not to scale) one embodiment of a grating structure produced by repetition of the method steps described above and illustrated schematically in FIG. 7.

[0158] Once the desired length is obtained, the printed grating structure is removed from the printing apparatus. The substrate is then removed, and the grating structure is then rotated by 90° such that the support material will be on the bottom and top of the grating structure. Reference is now made to FIG. 9, which presents a schematic illustration of the rotated structure following removal of the substrate. Once the grating structure has been removed from the substrate, at least one of the top or bottom is polished, thereby yielding the desired grating. In preferred embodiments, both sides are polished. The polishing may be done by any technique known in the art; in preferred embodiments, CMP is used. In some preferred embodiments of the invention, as much support material is left as is necessary for mounting of the grating or integration into an existing device. In some embodiments, both support and the grating itself can be polished to the desired thickness. The support thickness at one or both sides can be reduced to zero. In some embodiments, the remaining support can have an optical functionality, for example the support is the waveguide. In other preferred embodiments of the invention, the support thickness is reduced to any desired level, up to and including to zero, that is, in these embodiments the support material can be completely removed during the polishing step. In some preferred embodiments of the invention, the remaining support can have optical functionality, and is of a size and material appropriate for use as an optical element. In some especially preferred embodiments of the invention in which the support material remaining after polishing is optically functional, the remaining support is of dimension and material suitable for use as a waveguide. Reference is now made to FIG. 10, which presents a schematic diagram of a grating produced by this method.

[0159] In some non-limiting embodiments of the invention, it is used to fabricate a tangent tooth wave grating. In some non-limiting embodiments of the invention, the substrate is held at an angle other than perpendicular to the direction of travel of the droplets produced in the LIFT process. The grating structure is then polished parallel to its main axis, yielding a tangent grating. Reference is now made to FIG. 11, which presents a schematic diagram illustrating this embodiment of the method.

[0160] In some other non-limiting embodiments of the invention, a tangent tooth wave grating is produced by producing the grating structure as illustrated in FIG. 7, in which the substrate is perpendicular to the travel of the material released in the LIFT process. The resulting grating structure is then polished at an angle relative to its main axis. In typical non-limiting embodiments, the polishing is done at an angle of about 10° relative to the main axis of the grating structure. Reference is now made to FIG. 12, which illustrates schematically this embodiment of the method.

[0161] It is also within the scope of the invention to produce a 2D grating. A 2D grating structure can be produced by changing the grating configuration along the grating structure within one surface, for example, by changing the active materials or by changing the active materials' thickness. In these cases, the maximum resolution of the 2D structure is on the order of the diameter of the droplets released in the LIFT process, i.e., on the order of pm rather than of tens of nm. Yet more, in these cases, the maximum resolution of the 2D structure is on the order of the diameter of the droplets released in the LIFT process and / or of the XY translation / motion system, i.e., on the order of pm rather than of tens of nm. Reference is now made to FIG. 13, which is a schematic illustration of one embodiment of a 2D grating produced by the method disclosed herein.

[0162] In some non-limiting embodiments of the invention, one or more of the following options is included in the method in order to provide additional flexibility in the grating optics and the applications in which the grating may be used. As one non-limiting example, the grating period may be changed along the printing. The grating active material can be changed along the grating printing, either via gradual change in composition, alternate layers of different materials, two different materials creating an interface, etc. In cases in which two different materials are used to create an interface, the optical properties of the grating can be controlled by choosing two different materials having different refractive indices.

[0163] As a specific non-limiting example, method for fabrication of a square wave 500nm period grating is now described. The procedure described above is performed with the following process parameters used to fabricate a square wave grating structure with period of 500nm, 200nm step width (300nm filler), 500nm grating height and 1mm grating length. The support material is produced from droplets characterized by a height of 1 micron and diameter of 200 microns. A gap of 1-30 pm is left between adjacent droplets of support material Grating active material(s) are deposited as droplets having a diameter of about 30 pm and 100 nm thickness. The spacing between adjacent supports is chosen to be approximately the diameter of the droplets containing grating active material so that the active material does not cover the supports. The top of the grating structure is then polished down to the required 500nm height.

[0164] In some non-limiting embodiments of the invention, the gap between the droplets of support material is sufficiently large that several droplets of active and spacer material can be printed within the gap. After the printing stage is concluded, the resulting structure is cut and polished vertically in order to obtain multiple grating objects.

[0165] In embodiments of the invention in which no support material is used, following, the conclusion of the printing stage, the structure is cut and polished vertically in order to obtain multiple grating objects.

[0166] Nanoscale devices can be fabricated by using method described above for manufacturing nanoscale devices in variable applications like optics filters, semiconductor devices, biology nano structure devices, meta optics devices, etc. The resulting grating can be mounted on eyeglass optics to implement augmented reality transparent optics.

[0167] The method disclosed herein provides several advantages over the prior art. Some of these are listed here:

[0168] Precision and Customization: 3D printing allows for highly precise control over the grating structure, enabling the creation of customized patterns with specific dimensions and shapes tailored to specific applications.

[0169] Cost-Effectiveness: 3D printing can reduce manufacturing costs by eliminating the need for expensive masks and molds used in traditional lithography methods. This is especially beneficial for low-volume or specialized production runs.

[0170] Scalability: 3D printing can be easily scaled from prototyping to full-scale production without significant changes in the manufacturing process, allowing for flexible production capabilities.

[0171] Speed: The ability to rapidly prototype and produce grating structures with 3D printing accelerates the development cycle, allowing for quicker iteration and refinement of designs.

[0172] Material Efficiency: 3D printing minimizes material waste by using only the necessary amount of material for the fabrication process, which is both cost-effective and environmentally friendly.

[0173] Complex Geometries: 3D printing can fabricate complex and intricate geometries that are difficult or impossible to achieve with traditional manufacturing methods, expanding the possibilities for innovative optical grating designs.

[0174] Versatility in Materials: 3D printing supports a wide range of materials, enabling the creation of gratings with different optical properties and functionalities, such as flexible materials.

[0175] Reduced Production Steps: 3D printing integrates multiple fabrication steps into a single process, reducing the need for post-processing and assembly, which simplifies the production workflow.

[0176] Enhanced Performance: By precisely controlling the nano-scale layer thickness and patterning, 3D printing can enhance the optical performance of gratings, leading to higher efficiency and better device performance.

[0177] On-Demand Production: 3D printing allows for on-demand production, reducing the need for large inventories and enabling just-in-time manufacturing, which can be particularly useful for custom or short-run orders.

[0178] It is also within the scope of the invention to disclose a method for fabricating a multielement lens by LIFT -based additive manufacturing

[0179] The present invention is focused on printing of thin nm-scale optical coating layers. According to some embodiments of the present invention integration of digital printing for thin optics coating layers with existing 3D printing capabilities for optical lenses. Such integration presents a groundbreaking solution for multi-element optical device manufacturing. This innovative approach combines precision and scalability, promising to redefine traditionalconstraints in optical engineering. With this transformative capability, we anticipate significant advancements in the production of complex optical systems.

[0180] Multi element lenses assembly contains at least one optical lens with a predefined shape and material requirements. Each lens has requirements for thin optical coating on its front and back surfaces. The multi-element assembly structure defines the way the lenses should be assembled together as an optical device. Including required geometries and tolerances. The assembly structure also defines the material that should be used at the gap between the lenses. Typically, the gap material is air, but other materials can be used in the design of the device.

[0181] Thus, according to another embodiment of the present invention 3D printing of thin optics coating layers within 3D printing of multi-element lenses stack is enabled.

[0182] According to such an embodiment the following method is implemented. The first lens in the structure is printed using LIFT printing and / or a pre-fabricated not printed lens and any other printing technology. Required coating layers are then digitally printed on the lens. A scaffold or gap is then printed onto the coated lens; in typical embodiments, the gap is filled with air. The next lens is then printed next to the existing structure, and any required coating layers are printed on the lens. These steps are repeated as necessary. In all cases, the lenses and gaps are printed according to a predetermined shape. As with the fabrication of the gratings, the fabrication of the lenses involves production of layers that are typically characterized by a thickness of on the order of tens of nm.

[0183] It is also within the scope of the invention to disclose a LIFT -based process for producing optical coatings such as anti-reflection coatings. In this process, an optical device such as a lens is used as the substrate for the LIFT process. The lens may itself have been produced by the LIFT process disclosed herein, or it can be a prefabricated lens. The LIFT process disclosed herein is then used to deposit one or more layers of material, each layer characterized by a thickness of <600 nm. In typical embodiments of the invention, each layer of material is characterized by a thickness of on the order of tens of nm. The coating may comprise any material or combination of materials known in the art that is suitable for use as an optical coating and for deposition by LIFT. Non-limiting examples include TiCL, SiCF, zirconia, and hard coatings, but any suitable optical coating material known in the art may be used.

[0184] In some embodiments, the optical coating may be produced by methods similar to those described above for printing the active grating material on the substrate, e.g., by printing a suspension of nanoparticles on the substrate and drying the carrier.

[0185] The resulting coatings have excellent surface and optical properties.

Claims

CLAIMSWe claim:

1. A printing method for additive manufacture of an optical element, an optical coating, or combination thereof, wherein said method comprises fabricating said optical element, optical coating, or combination thereof by sequential deposition by said printing process of layers of material, said layers characterized by a thickness of <600 nm.

2. The method according to claim 1, wherein said printing process is selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, dry etching, wet etching, spin-coating, and any combination thereof.

3. The method according to claim 1, wherein said optical element is a grating, and said method comprises: printing a grating period in a space defined by support material, said step of printing a grating period comprising: printing grating active material as droplets characterized by a diameter of 800 nm - 800 pm and a thickness of <600 nm in said space, thereby producing a grating line; repeating said step of printing grating active material until said grating line reaches a predetermined thickness; printing additional droplets of support material as needed to maintain said support material at a height greater than that of said grating material; and, printing grating spacer material as droplets characterized by a thickness of < 600 nm on top of said grating active material; and, repeating said step of printing a grating period until a predetermined number of grating periods have been produced, thereby producing a grating structure.

4. The method according to claim 3, wherein said step of printing a grating period is preceded by a step of obtaining at least part of a support material, said step of obtaining at least part of a support material selected from the group consisting of: printing one droplet of a support material on a substrate; printing two droplets of a support material on a substrate, said two droplets separated by a separation larger than the required grating height structure;obtaining a pre-prepared support structure on a substrate, said pre -prepared support structure characterized by a structure comprising support material separated by a separation larger than the required grating height structure; and, obtaining a pre-prepared support structure and printing within said pre -prepared support structure printing two droplets of a support material on a substrate, said two droplets separated by a separation larger than the required grating height structure.

5. The method according to claim 4, wherein said support material is said grating active material.

6. The method according to claim 3, wherein said step of repeating said step of printing a grating period is followed by: removing said substrate; rotating said grating by 90° about an axis parallel to a plane defined by said support material such that said support material is on top and on bottom of said grating structure; and, polishing at least one side of said grating structure selected from the group consisting of said top and said bottom, thereby obtaining a grating.

7. The method according to claim 6, wherein said step of polishing comprises polishing one of said top and said bottom of said grating structure.

8. The method according to claim 7, wherein said grating spacer material is a material that can be removed by etching, and step of polishing is followed by a step of removing said grating spacer material by etching.

9. The method according to claim 6, wherein said step of polishing comprises polishing both said top and said bottom of said grating structure.

0. The method according to claim 6, wherein said step of polishing comprises polishing by using CMP.

1. The method according to claim 6, wherein said step of polishing comprises retaining sufficient support material on at least one side of said grating so as to permit mounting of said grating or integration of said grating into an existing structure.

12. The method according to claim 6, wherein: said substrate is maintained throughout said steps of printing in an orientation in which said substrate is not perpendicular to a direction of travel of material being deposited by said printing process; and, said step of polishing comprises polishing said top and said bottom of said structure in parallel to a main axis of said grating structure, thereby producing a tangent tooth wave grating.

13. The method according to claim 6, wherein said step of polishing comprises polishing at an angle not parallel to a main axis of said structure, thereby producing a tangent tooth wave grating.

14. The method according to claim 3, wherein said grating active material comprises a suspension of nanoparticles in a carrier.

15. The method according to claim 14, wherein said nanoparticles comprise nanoparticles of at least one substance selected from a group consisting TiCh particles, SiCh particles, and any mixture or combination thereof, and said carrier is selected from the group comprising l-methoxy-2-propanol (PGME), l-methoxy-2-propanol acetate (PGMEA), isopropyl alcohol (IPA), water, and any mixture or combination thereof.

16. The method according to claim 15, wherein said nanoparticles are characterized by a mean diameter of about 20 nm.

17. The method according to claim 15, wherein said nanoparticles are characterized by a mean diameter of about 10 nm.

18. The method according to claim 15, wherein said carrier is PGMEA.

19. The method according to claim 14, wherein said carrier comprises at least one additional component selected from the group consisting of surfactants, dispersants, and combinations and mixtures thereof.

20. The method according to claim 19, wherein said at least one additional component comprises a poloxamer surfactant.

21. The method according to claim 14, wherein said carrier comprises a combination or mixture of a plurality of substances characterized by different evaporation rates.

22. The method according to claim 21, wherein said step of printing grating active material comprises a step of evaporating said carrier in a two-stage evaporation process in which a morerapidly evaporating carrier substance evaporates first, causing said droplet containing said grating material to shrink, followed by evaporation of a more slowly evaporating carrier substance.

23. The method according to claim 21, wherein said carrier comprises a mixture of 5 - 50% (v / v) IP A and the remainder PGMEA.

24. The method according to claim 14, wherein said suspension comprises 0.25% - 1.5% by weight of said nanoparticles.

25. The method according to claim 14, wherein said suspension additionally comprises a UV curable polymer.

26. The method according to claim 3, wherein said substrate is made from glass.

27. The method according to claim 3, wherein said step of repeating said step of printing a grating period comprises printing grating periods that vary in width along a dimension of said grating structure.

28. The method according to claim 3, wherein said step of printing said grating material comprises varying said grating material along an axis of said grating structure.

29. The method according to claim 4, wherein: said step of printing two droplets of a support material comprises printing two droplets of a support material on a substrate, said two droplets separated by a separation sufficient to allow printing of a plurality of droplets of said active material and said spacer material within said separation; and, said method further comprises cutting and polishing said grating structures vertically, thereby obtaining multiple grating objects.

30. The method according to claim 3, wherein said method further comprises mounting said grating on eyeglass optics in order to provide augmented reality transparent optics.

31. The method according to claim 3, wherein said grating is a nanoscale device suitable for use in an application selected from the group consisting of optics filters, semiconductor devices, meta-optics devices, and biological nano structured devices.

32. The method according to claim 3, wherein said method is a method for producing a 2D grating, and said method comprises at least one step selected from the group consisting of: using more than one active material; and, varying a total thickness of active material in different locations in said grating.

33. The method according to claim 3, wherein said step of printing said active material comprises at least one step selected from the group consisting of: printing said droplets sequentially in sparse layers, each additional layer printed prior to complete drying of the layer preceding it in said sequence; printing said droplets sequentially in layers and drying each layer prior to printing a succeeding layer in said sequence; and, printing said droplets sequentially in layers and curing each layer by exposure to UV light prior to printing a succeeding layer in said sequence.

34. The method according to claim 3, wherein said step of printing said active material comprises: printing said droplets so as to obtain layers, said step of printing said droplets so as to obtain layers comprising at least one layer obtained according a sequence of steps comprising: printing a sparse layer of active material in a predetermined geometry, said layer comprising droplets characterized by a predetermined volume; and, printing a second sparse layer of active material, said layer comprising droplets characterized a volume sufficient to fill in gaps left in said sparse layer of active material.

35. The method according to any one of claims 1 - 34, wherein said printing process is LIFT.

36. The method according to claim 35, further comprising a step of vibrating a LIFT print head during at least one step of printing.

37. The method according to claim 35, further comprising a step of vibrating a LIFT receiving substrate.

38. The method according to claim 37, wherein said step of vibrating comprises vibrating so as to create a standing wave of said material on said receiving substrate.

39. The method according to claim 3, wherein said method additionally comprises printing a coating on top of said grating structure.

40. The method according to claim 39, wherein said step of printing a coating on top of said grating structure comprises printing coating material by sequential deposition of layers of said coating material by a printing process for printing coating material, said layers characterized by a thickness of <600 nm.

41. The method according to claim 40, wherein said printing process for printing coating material is selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, dry etching, wet etching, spin-coating, and any combination thereof.

42. The method according to claim 40, wherein said printing process for printing coating material is LIFT.

43. The method according to claim 42, further comprising a step of vibrating a LIFT print head during at least one step of printing.

44. The method according to claim 42, further comprising a step of vibrating a LIFT receiving substrate.

45. The method according to claim 44, wherein said step of vibrating comprises vibrating so as to create a standing wave of said material on said receiving substrate.

46. The method according to claim 39, wherein said coating is an anti-reflection coating.

47. The method according to claim 3, wherein said support structure is characterized by material and dimensions that make it suitable for use as an optical element.

48. The method according to claim 47, wherein said support structure is characterized by material and dimensions that make it suitable for at least one use selected from the group consisting of waveguide, diffuser, spectral filter, physical filter, polarizer, and any combination thereof.

49. The method according to claim 1, wherein said optical element is a compound lens comprising a plurality of subsidiary optical elements.

50. The method according to claim 49, wherein said printing process is selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, dry etching, wet etching, spin-coating and any combination thereof.

51. The method according to claim 49, wherein said method comprises printing said compound lens so as to leave a gap between two successive subsidiary layers.

52. The method according to claim 49, wherein said method comprises printing a coating on at least one side of at least one of said subsidiary optical elements.

53. The method according to claim 49, wherein at least two of said subsidiary elements are characterized by different refractive indices.

54. The method according to claim 49, wherein said material comprises a suspension of nanoparticles in a carrier.

55. The method according to claim 54, wherein said nanoparticles comprise nanoparticles of at least one substance selected from a group consisting TiCh particles, SiCh particles, and any mixture or combination thereof, and said carrier is selected from the group comprising l-methoxy-2-propanol (PGME), l-methoxy-2-propanol acetate (PGMEA), isopropyl alcohol (IPA), water, and any mixture or combination thereof.

56. The method according to claim 54, wherein said nanoparticles are characterized by a mean diameter of about 20 nm.

57. The method according to claim 54, wherein said nanoparticles are characterized by a mean diameter of about 10 nm.

58. The method according to claim 54, wherein said carrier is PGMEA.

59. The method according to claim 54, wherein said carrier comprises at least one additional component selected from the group consisting of surfactants, dispersants, and mixtures and combinations thereof.

60. The method according to claim 59, wherein said at least one additional component is a poloxamer surfactant.

61. The method according to claim 54, wherein said carrier comprises a combination or mixture of a plurality of substances characterized by different evaporation rates.

62. The method according to claim 61, wherein at least one step of printing comprises a step of evaporating said carrier in a two-stage evaporation process in which a more rapidly evaporating carrier substance evaporates first, causing said droplet containing said grating material to shrink, followed by evaporation of a more slowly evaporating carrier substance.

63. The method according to claim 61, wherein said carrier comprises a mixture of 5 - 50% (v / v) IPA and the remainder PGMEA.

64. The method according to claim 54, wherein said suspension comprises 0.25% - 1.5% by weight of said nanoparticles.

65. The method according to claim 49, wherein said step of producing said compound lens comprises sequentially depositing layers of material comprising droplets characterized by a diameter of between 30 and 800 pm.

66. The method according to any one of claims 49 - 65, wherein said printing process is LIFT.

67. The method according to claim 66, further comprising a step of vibrating a LIFT print head during at least one step of printing.

68. The method according to claim 66, further comprising a step of vibrating a LIFT receiving substrate.

69. The method according to claim 68, wherein said step of vibrating comprises vibrating so as to create a standing wave of said material on said receiving substrate.

70. The method according to claim 1, wherein said method is a printing method for additive manufacture of an optical coating, and further wherein said method comprises fabricating said optical coating by sequentially depositing by said printing process of layers of optical coating material, said layers characterized by a thickness of <600 nm.

71. The method according to claim 70, wherein said printing process is selected from the group consisting of Laser-Induced Forward Transfer (LIFT), aerosol jet printing, brushing, dry etching, wet etching, spin-coating and any combination thereof.

72. The method according to claim 70, wherein said optical coating material comprises at least one material selected from the group consisting of TiCL, SiCL, zirconia, hard coating material, and any combination thereof.

73. The method according to claim 70, wherein said optical coating material comprises a suspension of nanoparticles in a carrier.

74. The method according to claim 73, wherein said nanoparticles comprise nanoparticles of at least one substance selected from a group consisting TiCL particles, SiCL particles, and any mixture or combination thereof, and said carrier is selected from the group comprising l-methoxy-2-propanol (PGME), l-methoxy-2-propanol acetate (PGMEA), isopropyl alcohol (IPA), water, and any mixture or combination thereof.

75. The method according to claim 74, wherein said nanoparticles are characterized by a mean diameter of about 20 nm.

76. The method according to claim 74, wherein said nanoparticles are characterized by a mean diameter of about 10 nm.

77. The method according to claim 74, wherein said carrier is PGMEA.

78. The method according to claim 73, wherein said carrier comprises at least one additional component selected from the group consisting of surfactants, dispersants, and combinations and mixtures thereof.

79. The method according to claim 78, wherein said at least one additional component is a poloxamer surfactant.

80. The method according to claim 73, wherein said carrier comprises a combination or mixture of a plurality of substances characterized by different evaporation rates.

81. The method according to claim 80, wherein said step of sequentially depositing said optical coating material comprises a step of evaporating said carrier in a two-stage evaporation process in which a more rapidly evaporating carrier substance evaporates first, causing said droplet containing said grating material to shrink, followed by evaporation of a more slowly evaporating carrier substance.

82. The method according to claim 74, wherein said carrier comprises a mixture of 5 - 50% IPA (v / v) and the remainder PGMEA.

83. The method according to claim 74, wherein said suspension comprises 0.25% - 1.5% by weight of said nanoparticles.

84. The method according to claim 74, wherein said step of fabricating said optical coating by sequentially depositing layers of optical material comprises sequentially depositing droplets characterized by a diameter of between 30 and 800 pm.

85. The method according to any one of claims 70 - 84, wherein said printing process is LIFT.

86. The method according to claim 85, further comprising a step of vibrating a LIFT print head during at least one step of printing.

87. The method according to claim 85, further comprising a step of vibrating a LIFT receiving substrate.

88. The method according to claim 87, wherein said step of vibrating comprises vibrating so as to create a standing wave of said material on said receiving substrate.

89. A system for fabricating an optical element, an optical coating, or a combination thereof by sequential deposition of layers of material characterized by a thickness of <600 nm, said systemcomprising substrateless and / or local donor Laser Induced Forward Transfer (LIFT), said substrateless and / or local donor Laser Induced Forward Transfer (LIFT) comprising: a reservoir comprising at least one opening; at least one printing head in fluid connection with said reservoir; an energy source configured to deliver energy to a donor material within said reservoir and thereby initiate a LIFT process; and, a receiving substrate disposed such that material exiting said reservoir will impinge on said substrate; wherein said system comprises: printing means configured to print a grating structure in a space defined by a support material by a process comprising: printing grating active material as droplets characterized by a diameter of 800 nm - 800 pm and a thickness of <600 nm in said space, thereby producing a grating line; repeating said step of printing grating active material until said grating line reaches a predetermined thickness; printing additional droplets of support material as needed to maintain said support material at a height greater than that of said grating material; and, printing grating spacer material as droplets characterized by a thickness of < 600 nm on top of said grating active material; and, repeating said step of printing a grating period until a predetermined number of grating periods have been produced, thereby producing a grating structure.

0. The system according to claim 89, wherein said system further comprises at least one vibrating means selected from the group consisting of: a first vibrating means in mechanical connection with said at least one printing head, said vibrating means configured to cause said at least one printing head to vibrate; and, a second vibrating means in mechanical connection with said receiving substrate, said second vibrating means configured to cause said receiving substrate to vibrate.

1. The system according to claim 90, wherein said system comprises said second vibrating means, and said second vibrating means is configured to vibrate said receiving substrate so as to produce a standing wave of said material on said receiving substrate.

92. The system according to claim 89, wherein said at least one printing head is disposed between said energy source and said receiving substrate, and said printing head comprises a microfluidic chip (MFC), said MFC comprising three regions: an upper region; a middle region comprising: at least one ink channel passing through said MFC, said at least one ink channel comprising an ink channel inlet and an ink channel outlet; at least one intermediate layer channel passing through said MFC, said at least one intermediate layer channel comprising an intermediate layer channel inlet and an intermediate layer channel outlet ; and, a fluid connection within said MFC between said at least one ink channel and said at least intermediate layer channel; and, a lower region, said lower region comprising an orifice in fluid connection with said ink channel, said orifice oriented such that fluid exiting said orifice will travel toward said receiving substrate; said at least one ink channel and said at least one intermediate layer channel being disposed at said fluid connection such that said ink channel lies between said intermediate layer channel and said orifice; an ink reservoir in fluid connection with said ink channel inlet; and, an intermediate layer material reservoir in fluid connection with said intermediate layer channel inlet.

93. The system according to claim 89, wherein said energy source is a pulsed laser.

94. The system according to claim 89, additionally comprising energy transfer means for transferring energy from said energy source to a donor material within said reservoir.

95. The system according to claim 94, wherein said energy transfer means comprise a waveguide.

96. The system according to claim 89, additionally comprising temperature regulating means for regulating temperature of material within said reservoir.

97. The system according to claim 89, wherein said reservoir is disposed within said at least one printing head.

98. The system according to claim 89, further comprising flow means for providing a continuous flow of material through said reservoir.

99. The system according to claim 89, further comprising a feedback mechanism that supports at least one of calibration, synchronization, alignment, and process control of said system.

100. The system according to claim 89, further comprising a sensor configured to measure at least one parameter of material printed by said system, and provides feedback to at least one system selected from the group consisting of process control, sintering, and curing.