Light emitting device using metasurface and light emitting method thereof

Abstract

A light emitting device for promoting growth of one or more plants. The device has a light emitting layer comprising one or more light emitting diodes for emitting light, and at least one light conversion layer comprising one or more light conversion units. Each light conversion unit has a metasurface for adjusting one or more parameters of light emitted from the light emitting layer. In some embodiments, the light emitting device may also have a polarization control layer sandwiched between the light emitting layer and the light conversion layer.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial Nos. 62 / 862,853, filed on June 18, 2019, and 62 / 961,317, filed on January 15, 2020, the content of each of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to methods, devices, and systems for emitting light, and particularly to methods, devices, and systems for using metasurfaces to control the emitted light. Background Art

[0004] Light-emitting diodes (LEDs) are well-known and have been widely used in many industries, mainly as low-power light indicators. In recent years, LEDs with increased power output or luminous intensity have been developed and used as lighting sources. For example, with the improvement of energy efficiency, safety, and reliability, LED lights are replacing other types of lights in the market, such as incandescent lights, compact fluorescent lamps (CFLs), etc. Since daily lighting significantly increases the burden on the power grid and greatly increases the overall demand for power generation, the energy efficiency of LEDs will play a crucial role in future energy conservation. Due to their superior energy efficiency, LEDs are likely to dominate the lighting market.

[0005] High-efficiency LEDs have replaced traditional lighting solutions in various applications, such as flashlights, portable lights, luminaires, streetlights, etc. LEDs can be powered by various types of power sources, such as batteries, conventional power grids, renewable energy systems, and energy storage systems (e.g., systems using photovoltaic (PV) panels and battery packs, etc.), thus providing great flexibility in adapting lighting solutions to specific usage scenarios.

[0006] In many lighting solutions, it is preferred to configure a light source (e.g., an LED light source) to emit directional light, such as forming a converging beam and focusing it onto a predefined area to obtain enhanced lighting intensity, forming a collimated beam to reach a distant target, forming a diverging beam to illuminate a large area, etc. In some lighting solutions, the light direction of the light source can preferably be adjustable. In the prior art, mirrors or reflective surfaces are usually used by the light source to form directional light, and mechanical devices are often used to rotate the mirrors or reflective surfaces to adjust the light direction. Such directional lighting devices are usually large in size, slow in response speed, and low in efficiency.

[0007] LEDs with increased power output and / or increased luminous intensity are also used as light sources for growing plants and the like. Such LEDs are sometimes referred to as LED grow lights and offer various advantages such as producing precise light wavelengths, high intensity, high efficiency, etc. LED grow lights are also beneficial for indoor plant growth as the plant growth process can be carried out in a controlled environment with much fewer risks and other unwanted outdoor variables.

[0008] Plant growth is the result of the process of "photosynthesis". As is known in the art, the photosynthesis process utilizes energy from light to convert carbon dioxide (CO2) into organic materials. Specifically, light energy is absorbed by special proteins containing chlorophyll pigments, which are present in the photosynthetic cell membranes called chloroplasts. Photosynthetic cells are mainly in plant leaves.

[0009] However, chlorophyll only absorbs energy from specific parts or colors of the spectrum. The effective spectrum spans the blue and red spectra. The green part of the spectrum is reflected, which is why plant leaves are usually green. When the photosynthetic cells in the leaf die and the chlorophyll degrades, other pigment molecules in the leaf control the light reflection while they are degraded to the point of only showing brown.

[0010] It can be seen that different pigments in the chloroplast absorb specific wavelengths of light to promote photosynthesis, and there is a strong correlation between photosynthetic efficiency or rate and the light spectrum.

[0011] For example, rice plants grown under blue and red light have a higher photosynthetic efficiency than plants grown under red light only. Pea leaves grown under red LED light contain more β - carotene than pea leaves grown under blue - white LED light.

[0012] Light intensity is another factor affecting photosynthesis as photosynthetic organisms respond to high light intensity to reduce stress effects. Under red LED light, wheat seedlings accumulate chlorophyll at 100 μmol m -2 s -1 but do not accumulate chlorophyll at 500 μmol m -2 s -1 .

[0013] It has been observed that plants generally absorb the blue light spectrum in the initial growth stage and then gradually absorb the red light spectrum during the mature and flowering stages. It has also been observed that some plants have highly ordered components that make them sensitive to the interaction with light polarization. For example, such plants may absorb or reflect light with a specific polarization state more effectively than light with other polarization states.

[0014] In addition, plants are able to sense the light cycle and the duration of time and change their growth rate accordingly.

[0015] Growing plants using a constant or commonly defined lighting configuration is neither energy - efficient nor suitable for photosynthesis. Since LED grow lights of the prior art typically provide light to plants without considering the above - mentioned factors, they cannot provide an optimized lighting configuration for optimizing the physiological processes of growing plants. In addition, different plants require different light characteristics (e.g., intensity, spectrum, polarization, time, etc.) to achieve optimal growth performance. However, LED grow lights of the prior art cannot adapt to the needs of plants and cannot provide appropriate light characteristics.

[0016] For example, traditional lighting systems, such as LED panels used for indoor plant growth, typically do not produce a uniform light distribution on plants. Their intensity is usually strongest at the center and gradually weakens away from the center.

[0017] Figure 1A shows a traditional light source 10 that emits a light beam 12 towards a square image plane 14 at a certain distance from the square image plane 14. Figure 1B shows the light intensity distribution 16 on the image plane 14. It can be seen that the traditional light source 10 does not produce a uniform distribution of light on the image plane 14. Instead, the light intensity distribution 16 on the image plane 14 is strongest at its center and gradually decreases away from the center. In addition, the intensity light distribution 16 is symmetric about the point of incidence of the light beam 12 on the image plane 14.

[0018] Figures 2A and 2B show the illumination pattern generated by an LED panel 10 at a 6×6 square meters (m 2 ) image plane 14 at a distance of about 3 meters (m) from the panel 10 obtained using ray tracing. The intensity distribution is significantly non - uniform.

[0019] Therefore, using a grow light with a light source 10 that provides sufficient light around the plant will result in over - illumination at the center of the plant, leading to poor plant growth. On the other hand, providing sufficient light at the center of the plant will result in low lighting efficiency around the plant, also leading to poor plant growth. Such an intensity distribution is due to the symmetry of the center of the image plane with respect to the light emitter.

[0020] Such a light source 10 may not be desirable in other applications. For example, street lights using such a light source 10 may cause glare and overall inefficient lighting.

[0021] LEDs are also used in indoor and outdoor displays, which also require careful control of various light characteristics such as intensity, polarization, time, and / or the like with a fast response.

[0022] Therefore, there is always a desire for LED devices, systems, and methods with controlled light characteristics. Summary of the Invention

[0023] According to one aspect of the present disclosure, a light-emitting device is provided. The light-emitting device includes: a light-emitting layer for emitting light; and a light conversion layer coupled to the light-emitting layer, the light conversion layer including one or more light conversion units, each light conversion unit including a metasurface for adjusting one or more parameters of the light emitted from the light-emitting layer.

[0024] In some embodiments, the light-emitting layer includes one or more light-emitting diodes (LEDs) for emitting light.

[0025] In some embodiments, the light conversion layer is printed onto the light-emitting layer.

[0026] In some embodiments, the light-emitting layer includes one or more light-emitting units; the light conversion layer includes a housing having one or more containers for receiving one or more metasurfaces; and the one or more containers are located at positions corresponding to the positions of the one or more light-emitting units for aligning the one or more metasurfaces with the one or more light-emitting units.

[0027] In some embodiments, each of the one or more containers includes an inwardly extending inner surface having an inner opening for receiving the light emitted from the light-emitting layer and an outer opening for passing the received light, and the area of the outer opening is larger than the area of the inner opening.

[0028] In some embodiments, the inner surface of each of the one or more containers is reflective.

[0029] In some embodiments, the cross-section of the inner surface of each of the one or more containers has a parabolic shape.

[0030] According to one aspect of the present disclosure, a light-emitting device is provided. The light-emitting device includes: a light-emitting layer for emitting light; and a light conversion layer including one or more light conversion units, each light conversion unit including a metasurface, and at least one metasurface is polarization-selective for selectively passing light having a predefined polarization state emitted from the light-emitting layer.

[0031] In some embodiments, each of the one or more metasurfaces includes a plurality of nanostructures arranged in an asymmetric basic geometry.

[0032] In some embodiments, the light-emitting device further includes a polarization control layer sandwiched between the light-emitting layer and the light conversion layer for polarizing the light emitted from the light-emitting layer.

[0033] In some embodiments, the light-emitting device is a growth lamp for promoting the growth of one or more plants.

[0034] According to one aspect of the present invention, there is provided a lighting device for promoting the growth of one or more plants. The lighting device includes: a light-emitting layer for emitting light; and at least one light conversion layer including one or more light conversion units, each light conversion unit including a metasurface for adjusting one or more parameters of the light emitted from the light-emitting layer, for optimizing the lighting configuration for one or more plants.

[0035] According to one aspect of the present disclosure, there is provided a display device. The display device includes: a light-emitting layer for emitting light; and at least one light conversion layer including one or more light conversion units, each light conversion unit including a metasurface for adjusting one or more parameters of the light emitted from the light-emitting layer, for displaying one or more images.

[0036] According to one aspect of the present disclosure, there is provided a lighting device. The lighting device includes: a light-emitting layer for emitting light; a polarization control layer coupled to the light-emitting layer for polarizing the light emitted from the light-emitting layer; and at least one light conversion layer coupled to the polarization control layer, the at least one light conversion layer including one or more light conversion units, each light conversion unit including at least one metasurface, the at least one metasurface being polarization-selective for selectively passing the polarized light from the polarization control layer, so as to switch between different lighting patterns or images.

[0037] According to one aspect of the present disclosure, there is provided a lighting device. The lighting device includes: a light-emitting layer for emitting light; a polarization control layer coupled to the light-emitting layer for polarizing the light emitted from the light-emitting layer; and at least one light conversion layer coupled to the polarization control layer, the at least one light conversion layer including one or more light conversion units, each light conversion unit including at least one metasurface, the at least one metasurface being polarization-selective for selectively passing the polarized light from the polarization control layer, so as to generate a plurality of different lighting patterns or images at different positions.

[0038] According to one aspect of the present disclosure, there is provided a lighting device. The lighting device includes: a light-emitting layer for emitting light into a source field of view (FOV); and at least one metasurface layer in front of the light-emitting layer for directing the light emitted from the light-emitting layer into a first FOV having an angular span smaller than the angular span of the source FOV.

[0039] In some embodiments, the lighting device further includes a polarization control layer sandwiched between the light-emitting layer and the at least one light conversion layer; the polarization control layer is configured to polarize the light emitted from the light-emitting layer to a first polarization state or a second polarization state in response to a control signal; and wherein the at least one light conversion layer is configured to direct the light from the polarization control layer in the first polarization state into a first FOV having an angular span smaller than the angular span of the source FOV, and direct the light from the polarization control layer in the second polarization state into a second FOV having an angular span larger than the angular span of the first FOV.

[0040] According to one aspect of the present disclosure, a light-emitting device is provided. The light-emitting device includes: a light-emitting layer for emitting light; and a light conversion layer in front of the light-emitting layer, the light conversion layer including a plurality of light conversion units, each light conversion unit including a metasurface for guiding the light emitted from the light-emitting layer to a target area to form a predefined light distribution pattern.

[0041] In some embodiments, the predefined light distribution pattern is a substantially uniform light energy distribution on the target area.

[0042] In some embodiments, the plurality of metasurfaces includes a first group of metasurfaces for guiding the light emitted from the light-emitting layer to the boundary of the target area, and a second group of metasurfaces for guiding the light emitted from the light-emitting layer to the center of the target area, for generating a substantially uniform light energy distribution on the target area.

[0043] According to one aspect of the present invention, a solar energy collection device is provided. The solar energy collection device includes: a photovoltaic layer having a plurality of photovoltaic cells; and at least one metasurface layer in front of the photovoltaic layer for guiding light to the photovoltaic layer with substantially no reflection on the photovoltaic layer.

[0044] In some embodiments, the solar energy collection device includes a plurality of metasurface layers for guiding light with a predetermined range of incident angles to be perpendicularly incident on the photovoltaic layer.

[0045] According to one aspect of the present disclosure, a light-emitting device is provided. The light-emitting device includes: a light-emitting layer for emitting light; and at least one metasurface layer in front of the light-emitting layer for guiding the light emitted from the light-emitting layer in a first polarization state to a first FOV and guiding the light emitted from the light-emitting layer in a second polarization state to a second FOV; the first and second FOVs overlap with each other and are laterally offset so that a user wearing a pair of glasses with lenses of different polarization states forms a three-dimensional (3D) perception.

[0046] According to one aspect of the present disclosure, a light-emitting device is provided. The light-emitting device includes: a light-emitting layer for emitting light; and at least one metasurface layer in front of the light-emitting layer for guiding the light from the light-emitting layer in a first polarization state to a first FOV and guiding the light from the light-emitting layer in a second polarization state to a second FOV; the first and second fields of view are laterally offset from each other such that the first FOV is only visible to the first eye of the user at a predetermined distance, and the second FOV is only visible to the second eye of the user at a predetermined distance, so that the user forms a 3D perception. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1A is a schematic diagram showing a prior art light source emitting a light beam towards a square image plane at a certain distance from the square image plane;

[0048] Figure 1B shows the light intensity distribution of light emitted from the prior art light source shown in Figure 1A on the image plane;

[0049] Figure 2A is a schematic diagram showing a prior art light-emitting diode (LED) panel that emits a light beam towards a square image plane at a certain distance from the square image plane;

[0050] Figure 2B shows the illumination pattern of light emitted from the prior art LED panel on the image plane, which is obtained using ray tracing;

[0051] Figure 3 is a schematic diagram showing the structure of a light-emitting device according to some embodiments of the present disclosure, the light-emitting device including an LED light-emitting layer and a light conversion layer having one or more metasurfaces;

[0052] Figure 4 is Figure 3 a schematic exploded view of the light-emitting device shown;

[0053] Figure 5 shows Figure 3 the light conversion units of the light conversion layer of the light-emitting device shown;

[0054] Figure 6 shows an example of the structure of the metasurface for forming Figure 5 the light conversion units shown;

[0055] Figure 7 is a schematic exploded view of a light-emitting device according to some embodiments of the present disclosure, the light-emitting device including an LED light-emitting layer, a polarization control layer, and a metasurface light conversion layer;

[0056] Figure 8A is a schematic diagram showing Figure 7 the pixels of the polarization control layer of the light device shown according to some embodiments of the present disclosure;

[0057] Figure 8B is a schematic diagram showing Figure 7 the pixels of the light conversion layer of the light device shown corresponding to Figure 8A the pixels of the polarization control layer shown;

[0058] Figure 9A is a schematic diagram showing Figure 7 the pixels of the polarization control layer of the light device shown according to still some other embodiments of the present disclosure;

[0059] Figure 9B is a schematic diagram showing Figure 7 the pixels of the light conversion layer of the light device shown corresponding to Figure 9A the pixels of the polarization control layer shown;

[0060] Figure 10A is a schematic diagram showing pixels of a polarization control layer of an optical device according to still further embodiments of the present disclosure; Figure 7 as shown;

[0061] Figure 10B is showing Figure 7 pixels of a light conversion layer of the optical device as shown corresponding to Figure 10A pixels of the polarization control layer as shown;

[0062] Figure 11A and 11B is showing according to Figure 8A and Figure 8B or Figure 9A and Figure 9B embodiments as shown of Figure 7 the optical device as shown showing two images in two directions;

[0063] Figure 12 is showing according to Figure 8A and Figure 8B 、 Figure 9A and Figure 9B or Figure 10A and Figure 10B embodiments as shown of Figure 7 the optical device as shown showing two images in two directions;

[0064] Figure 13 is a schematic exploded view of a light emitting device having a plurality of optical fiber cables according to some embodiments of the present disclosure;

[0065] Figure 14 is showing Figure 3 a printed conceptual diagram of a light conversion layer of the light emitting device as shown;

[0066] Figure 15 is a schematic diagram of a lighting system for promoting plant growth according to some embodiments of the present disclosure;

[0067] Figure 16 is a schematic diagram of a lighting system for promoting plant growth, which according to some embodiments of the present disclosure includes a sensor for monitoring plant growth;

[0068] Figure 17 is showing the structure of a solar cell layer incorporated in the light emitting device as shown in Figure 3 ;

[0069] Figure 18 is a schematic diagram showing the structure of a lighting system serving as a lighting or light source having a controlled lighting pattern according to some embodiments of the present disclosure;

[0070] Figure 19 shows an example of a cost function for forming an illumination system shown by Figure 18 to generate an illumination pattern;

[0071] Figure 20 is a flowchart showing steps of a process for using the gradient descent method to find the global (or near-global) minimum of the cost function executed by the processing structure of the illumination system shown by Figure 18 ;

[0072] Figures 21 to 25 shows Figure 20 the optimization results of a process for generating various illumination patterns;

[0073] Figure 26 is a schematic diagram showing the structure of an illumination system according to some embodiments of the present disclosure, which serves as an illumination or light source with a controlled illumination pattern;

[0074] Figure 27A is a schematic diagram showing a split metasurface for generating a boundary of an intensity distribution in an image plane;

[0075] Figure 27B shows an illumination pattern in the image plane generated by a Figure 27A vertical split metasurface, where the light energy is concentrated substantially along the vertical boundary of the target area;

[0076] Figure 27C shows an illumination pattern in the image plane generated by a Figure 27A horizontal split metasurface, where the light energy is concentrated substantially along the horizontal boundary of the target area;

[0077] Figure 28 shows a conceptual representation of a light distribution substantially concentrated along the horizontal and vertical boundaries of a target area using Figure 27A the horizontal and vertical split metasurfaces shown;

[0078] Figure 29A is a schematic diagram showing a converging metasurface for generating a light distribution substantially concentrated at the center of an image plane;

[0079] Figure 29B shows an illumination pattern in the image plane generated by a Figure 29A converging metasurface shown;

[0080] Figure 30 shows a conceptual representation of a substantially uniform light distribution on an image plane generated by Figure 27A and 29A the split and converging metasurfaces shown;

[0081] Figure 31 shows a substantially uniform light distribution on an image plane at different distances;

[0082] Figure 32 Shows an exemplary implementation of a topological vector control panel (TVCP) using a metasurface array according to some embodiments of the present disclosure. The TVCP includes a metasurface housing coupled to a light-emitting layer. The metasurface housing includes a plurality of containers for receiving a plurality of metasurface units therein;

[0083] Figure 33 Is a photograph showing a metasurface housing coupled to Figure 32 the light-emitting layer of the TVCP shown;

[0084] Figure 34 Shows the nanoscale structure of a metasurface having an asymmetric basic geometry for illuminating plants in a specific polarization state;

[0085] FIG. 35 is a schematic diagram showing light reflection occurring on the surface of a prior art photovoltaic cell;

[0086] Figure 36 Is a schematic diagram showing a solar panel device having a metasurface-based topocentric vector control panel (TVCP) in front of a photovoltaic panel for reducing light reflection at the surface of the photovoltaic panel;

[0087] Figure 37 Is a schematic diagram showing a solar panel device having a metasurface-based TVCP in front of a photovoltaic panel for reducing the size of the photovoltaic panel;

[0088] FIG. 38 is a schematic diagram showing a prior art solar panel device having a photovoltaic panel without a TVCP for comparison with Figure 37 the solar panel device shown;

[0089] FIG. 39 is a schematic diagram showing a prior art display having a field of view (FOV) with a wide angular span;

[0090] Figure 40 Is a schematic diagram showing a superdirective screen or display using a metasurface according to some embodiments of the present disclosure;

[0091] Figure 41 Is a schematic diagram showing a variable field of view (VFOV) screen or display according to some embodiments of the present disclosure;

[0092] Figure 42 Is a schematic diagram showing a VFOV screen or display according to some other embodiments of the present disclosure;

[0093] Figures 43A to 43G Shows the use of Figure 42An example of a VFOV screen showing two images simultaneously, where the first image is shown in a first FOV with a wide angular span and the second image is shown in a second FOV with a narrow angular span, such that the second image is invisible to a user located only in the first FOV;

[0094] Figure 44 is a schematic diagram showing a three-dimensional (3D) display of a metasurface viewable using glasses with polarization lenses according to some embodiments of the present disclosure;

[0095] Figure 45 is a schematic diagram showing a 3D display of a metasurface viewable without any glasses with polarization lenses according to some embodiments of the present disclosure;

[0096] Figures 46 and 47 are schematic diagrams showing prior art solar panels with light reflection problems; and

[0097] Figure 48 and 49 is a schematic diagram showing a solar panel using a metasurface for reducing or eliminating light reflection problems according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0098] Light - emitting device having a light - emitting layer and a light - conversion layer

[0099] Now turning to Figure 3 and 4 , according to some embodiments of the present disclosure, a light-emitting device (also referred to as "lighting device" or "light device") is shown and is generally identified using reference numeral 100. Here, the light-emitting device can be a device for illumination, a device for promoting plant growth, or a device for displaying images or videos thereon.

[0100] In these embodiments, the light-emitting device 100 includes a light-emitting layer 104 sandwiched between a substrate 102 and a light-converting layer 106 for emitting light 108 from the light-emitting layer 104 through the light-converting layer 106. When the emitted light 108 passes through the light-converting layer 106, the light-converting layer 106 adjusts one or more parameters of the light 108, such as amplitude or intensity, phase, polarization, pattern, direction, etc.

[0101] The light-emitting layer 104 can be any suitable lighting device. In these embodiments, the light-emitting layer 104 is printed, coated, or otherwise coupled to the substrate 102 and includes a plurality of light-emitting diodes (LEDs) 110 arranged in a matrix form, although other arrangements of the LEDs 110 are also readily available. Here, the LEDs 110 can be any suitable LEDs, such as conventional LEDs, quantum dot (QD) LEDs, organic LEDs (OLEDs), and / or the like.

[0102] The light conversion layer 106 is printed, coated, or otherwise coupled to the light-emitting layer 104 for adjusting or otherwise transforming the parameters of the light emitted from the light-emitting layer 104 (which will be described in more detail later).

[0103] The light conversion layer 106 includes one or more light conversion units 122 arranged in a predefined pattern, where each light conversion unit 122 includes a metasurface. Here, a metasurface is a two-dimensional array of nanostructures with subwavelength spacing and can be used to modulate electromagnetic waves. The details of the metasurface are described in the academic paper titled "Light Propagation and Phase Discontinuities: Generalized Laws of Reflection and Refraction" by Nouthfang Yu, Patrice Genevet, Mikhail A. Kats, Francesco Aieta, Jean-Philippe Tetienne, Federico Capasso, and Zeno Gaburro, Science, Vol. 334, No. 6054, pp. 333 - 337 (2011).

[0104] As Figure 5 and Figure 6 shown, each metasurface unit 122 includes a metasurface having a subwavelength thickness (i.e., its thickness is less than the wavelength of the light emitted from the light-emitting layer 104), and includes a plurality of nanoscale structures 124 arranged periodically in a specific order for precisely adjusting or transforming the characteristics or parameters of the incident light (e.g., amplitude or intensity, phase, polarization, pattern, direction, etc.), thereby allowing precise control over the nature of the light output from it.

[0105] In some embodiments, the nanoscale structures 124 (also denoted as "nanostructures") can be subwavelength structures made of a suitable metal or dielectric material, one or more of whose dimensions are less than the wavelength of the light emitted from the light-emitting layer 104. In some embodiments, the nanoscale structures 124 can include a plurality of nanorods (also denoted as "antennas"; see Figure 6 ). In some embodiments, the nanoscale structures 124 can include a plurality of V-shaped nanorods. As described above, the nanoscale structures 124 form a periodic or repeating pattern, and each pattern can include a plurality of nanoscale structures 124 having different shapes and sizes.

[0106] Depending on the geometry and distribution of the nanostructures 124, the light conversion layer 106 can be configured to adjust or transform one or more parameters of the incident light.

[0107] For example, as Figure 4As shown, the metasurface unit 122A of the light conversion layer 106 can be configured to perform phase transformation on the incident light 108A and modify its converging direction, so as to form a converging light beam focused at a desired point spaced apart from the light conversion layer 106.

[0108] As another example, the metasurface unit 122B of the light conversion layer 106 can be configured to perform phase transformation on the incident light 108B and modify its collimating direction, so as to form a collimated light beam for reaching a distant target.

[0109] As a further example, the metasurface unit 122C of the light conversion layer 106 can be configured to perform phase transformation on the incident light 108C and modify its diverging direction, so as to form a diverging light beam for illuminating a large area.

[0110] In traditional grow light applications, one or more lighting devices (also referred to as grow light devices) are used to emit light towards plants to promote their growth. In these applications, due to the diverging nature of the light beam, a part of the light emitted from the grow light device (such as the light emitted from the peripheral area of the grow light device) may only partially illuminate the plants, thus wasting light energy. Such a problem may be more important if the plants are spaced apart from each other.

[0111] In some embodiments, the light emitting device 100 can be used as a grow light device without or at least mitigating the above problems. In these embodiments, the light conversion layer 106 or at least some of its metasurface units 122 can be designed to modify the direction of the incident light 108 towards the plants. For example, the light conversion layer 106 can be designed to adjust the light emitted from the peripheral area of the light emitting layer 104 towards the plants, while making the light emitted from the central area of the light emitting layer 104 more divergent to cover a larger area of the plants, thereby resulting in significantly more efficient illumination.

[0112] In some embodiments, the light conversion layer 106 or at least some of its metasurface units 122 can be designed to adjust the parameters of the light emitted from the light emitting layer 104 to optimize the lighting configuration of the plants and adapt to their growth needs.

[0113] In some embodiments, the light conversion layer 106 or at least some of its metasurface units 122 can be designed to adjust the light emitted from the light emitting layer 104 towards a desired direction to form regions with high or low light concentration, thereby creating hot spots or cold spots at the target illumination area. Such hot spots or cold spots can be used to treat damaged areas of the plants or to illuminate their vulnerable parts.

[0114] Figure 7 is a schematic exploded view of a light emitting device 200 according to some embodiments of the present disclosure. In these embodiments, the light emitting device 200 is similar to Figure 3 and Figure 4The light-emitting device 100 in the illustrated embodiment is different in that the light-emitting device 200 further includes a polarization control layer 202 sandwiched between the light-emitting layer 104 and the light conversion layer 106.

[0115] In addition, in these embodiments, the light conversion layer 106 can be polarization-selective. In particular, each metasurface unit 122 can select a specific polarization, that is, only allow light with a specific polarization state to pass through it and block light with other polarization states. According to an embodiment, different metasurface units 122 of the light conversion layer 106 can have the same or different polarization-selective settings.

[0116] The polarization control layer 202 is made of a suitable material that polarizes the incident light when the incident light passes through the material (represented by the circular arrows 204 and 206 in Figure 7 ). In some embodiments, the polarization control layer 202 can form a single polarization control unit and polarize the incident light to a predetermined polarization state.

[0117] In some other embodiments, the polarization control layer 202 can form a single polarization control unit and include liquid crystals with voltage-controlled delay. Therefore, the polarization of the polarization control layer 202 can be controlled by adjusting the voltage applied to the polarization control layer 202.

[0118] In some additional embodiments, the polarization control layer 202 can include a plurality of polarization control units (not shown) corresponding to the plurality of metasurface units 122 of the light conversion layer 106. At least some of the polarization control units can be made of liquid crystals, and their polarization is controlled by adjusting the voltage applied to them.

[0119] Therefore, the light conversion layer 106 exhibits a selective response to light of different polarization states. In some embodiments, the light-emitting device 200 can be used as a display that can quickly switch between displaying different images without adjusting the light source (e.g., the light-emitting layer 102). The switching of the display or illumination pattern can be encoded as the polarization pattern and / or its voltage pattern of the light conversion layer 106 for automatic pattern switching.

[0120] For example, in some embodiments, the light-emitting device 200 can be used as a display, and its polarization control layer 202 and light conversion layer 106 can each include a plurality of units that respectively form corresponding pixels 232 and 234, and each pixel includes one or more sub-pixels (see Figures 8A to 10B ).

[0121] In Figure 8A and Figure 8BIn one illustrated embodiment, each pixel 232 of the polarization control layer 202 includes a plurality of sub-pixels (e.g., two sub-pixels 242A and 242B). Thus, the polarization control layer 202 includes a plurality of sub-pixel groups (also identified using reference numerals 242A and 242B), each group including the corresponding sub-pixel 242A or 242B of each pixel 232. Each sub-pixel group is configured for a specific polarization setting (see Figure 8A ).

[0122] As Figure 8B shown, each pixel 234 of the light transformation layer 106 has a metasurface sub-pixel (also denoted by the reference numeral 234), which is controlled to switch between two polarization-selective and phase transformation settings (denoted by the symbol 246).

[0123] During operation, the light-emitting layer 104 emits light (not shown). With appropriate polarization settings, each sub-pixel group of the polarization control layer 202 adjusts the light emitted from the light-emitting layer 104 and forms two light beams (not shown) having different polarization states. These two light beams overlap and are incident on the light transformation layer 106.

[0124] The metasurface sub-pixel 234 of the light transformation layer 106 is controlled to switch between two polarization-selective and phase transformation settings 246, the first polarization-selective setting being suitable for allowing the light beam from the first sub-pixel group 242A to pass therethrough, and the second polarization-selective setting being suitable for allowing the light beam from the second sub-pixel group 242B to pass therethrough. Thus, the light-emitting device 200 alternately displays two images 222 and 224 in two directions (see Figure 11A and 11B ). Depending on the phase transformation setting, these two directions can be two different directions as shown in Figure 11A and 11B , or can be the same direction.

[0125] The switching of the polarization-selective and phase transformation settings of the light transformation layer 106 (also denoted as the refresh rate) can alternately display the two images 222 and 224 in a touchable manner at a slow rate or frequency, e.g., displaying the first image 222 at a first position for a few seconds and then displaying the second image 224 at a second position for another few seconds ( Figure 11A and 11B ). Alternatively, the refresh rate of the light transformation layer 106 can be a high frequency (e.g., greater than or equal to 60 frames per second) such that the two images 222 and 224 are effectively displayed simultaneously at two positions of the human eye (see Figure 12 ).

[0126] In Figure 9A and 9BIn one embodiment shown, each pixel 232 of the polarization control layer 202 has a metasurface sub-pixel (also denoted by the reference numeral 232), and the metasurface sub-pixel is controlled to switch between two polarization settings (see Figure 9A , denoted by the symbol 248).

[0127] As Figure 9B shown, each pixel 234 of the light conversion layer 106 includes a plurality of sub-pixels (e.g., two sub-pixels 244A and 244B). Thus, the light conversion layer 106 includes a plurality of sub-pixel groups (also identified by the reference numerals 244A and 244B), and each group includes the corresponding sub-pixel 244A or 244B of each pixel 234. Each sub-pixel group is configured with a specific polarization selectivity and phase transformation setting.

[0128] During operation, the light-emitting layer 104 emits light (not shown). The polarization control layer 202 adjusts the light emitted from the light-emitting layer 104 and forms a light beam (not shown) with a switched polarization state so as to pass through the first sub-pixel group 244A or the second sub-pixel group 244B of the light conversion layer 106. According to the refresh rate of the light conversion layer 106, the light-emitting device 200 can alternately display two images 222 and 224 to the human eye in a touchable manner or effectively simultaneously at two positions (see Figure 11A , 11B and 12).

[0129] In Figure 10A and 10B shown in one embodiment, each pixel 232 of the polarization control layer 202 includes a plurality of sub-pixels (e.g., two sub-pixels 242A and 242B). Thus, the polarization control layer 202 includes a plurality of sub-pixel groups (also identified by the reference numerals 242A and 242B), and each group includes the corresponding sub-pixel 242A or 242B of each pixel 232. Each sub-pixel group is configured with a specific polarization setting (see Figure 10A ).

[0130] Correspondingly, as Figure 10B shown, each pixel 234 of the light conversion layer 106 includes a plurality of sub-pixels (e.g., two sub-pixels 244A and 244B). Thus, the light conversion layer 106 includes a plurality of sub-pixel groups (also identified by the reference numerals 244A and 244B), and each group includes the corresponding sub-pixel 244A or 244B of each pixel 234. Each sub-pixel group is configured with a specific polarization selectivity and phase transformation setting. The polarization selectivity setting of each sub-pixel group 244A or 244B matches the polarization setting of each sub-pixel group 242A or 242B (i.e., allows the light from the corresponding sub-pixel 242A or 242B to pass through it).

[0131] During operation, the light-emitting layer 104 emits light (not shown). Each sub-pixel group 242A or 242B of the polarization control layer 202 adjusts the light emitted from the light-emitting layer 104 and forms two light beams (not shown) having different polarization states. These two light beams overlap and are incident on the light conversion layer 106. Each light beam from the polarization control layer 202 passes through the corresponding sub-pixel group 244A or 244B of the light conversion layer 106, thereby simultaneously forming two images 222 and 224 in two directions (see Figure 12 ).

[0132] In some embodiments, the light-emitting device 200 can be used as a lighting device that can quickly switch between different lighting patterns. In addition, the light-emitting device 200 can be used as a grow light device having a custom polarization pattern that is suitable for plants having highly ordered components that are sensitive to the polarization of light. For example, some plants may absorb or reflect light having a specific polarization state more effectively than light having other polarization states. Thus, the light-emitting device 200 can be used as a grow light device having a custom polarization pattern that is suitable for the needs of the plants to optimize their photosynthesis process. The structure of the lighting device 200 in various embodiments can be similar to Figures 8A to 10B the structure shown.

[0133] By using a metasurface in the light conversion layer 106, the lighting devices disclosed herein can effectively couple light energy into an optical fiber cable. For example, Figure 13 is a schematic exploded view of a light-emitting device 300 according to some embodiments of the present disclosure. In these embodiments, the light-emitting device 300 is similar to Figure 3 and 4 the light-emitting device 100 in the embodiments shown, and further includes a plurality of optical fiber cables 302 adjacent to each metasurface unit 122. Each metasurface unit 122 is configured to form a converging light beam incident on the corresponding optical fiber cable 302. Such a lighting device 300 can be used in various applications, such as efficient indoor lighting, local optimized lighting of plants, and efficient distribution of light energy over a target area.

[0134] Although in Figure 13 the embodiments shown, the light-emitting device 300 is similar to the light-emitting device 100 (i.e., having three layers 102, 104, and 106), in some embodiments, the light-emitting device 300 can be similar to the light-emitting device 200 (i.e., having four layers 102, 104, 202, and 106).

[0135] In the above embodiments, the lighting devices 100, 200, or 300 include only one light conversion layer 106. In some embodiments, the lighting device may include a plurality of light conversion layers 106. In some embodiments, at least some of the plurality of light conversion layers 106 may be polarization selective, and different light conversion layers 106 may have the same or different polarization selective settings, depending on the implementation.

[0136] As described above, any suitable printing technique can be used to print the various layers of the lighting device 100, such as the light conversion layer 106, onto the substrate 102 or onto each other.

[0137] For example, Figure 14 is a conceptual diagram showing the printing of some layers, such as the light conversion layer 106 and the light emitting layer 104, in some embodiments.

[0138] As shown in the figure, the substrate 102 (on which the light emitting layer 104 is printed or otherwise coupled) is disposed on the flat surface of the platform 342. A printing device (not shown) having a slot die head 344 is used to print the sub-layers / layers. The slot die head 344 includes a corresponding ink cartridge 346 filled and moves (as indicated by the arrow 348) over the substrate 102 (or specifically the printed light emitting layer 104) to deposit the metasurface material from the ink cartridge 346 thereon to form one or more metasurface light conversion units 122.

[0139] Here, "ink" refers to a suitable form of sub-layer / layer material, such as a solution, gel, or powder, which is used as a precursor for manufacturing the layer. During the slot die manufacturing process of each layer, heat treatment is typically used to evaporate the solvent or melt the powder to cure the manufactured layer.

[0140] Figure 15 is a schematic diagram of a lighting system 400 for promoting the growth of one or more plants 410 according to some embodiments of the present disclosure. As shown, the system 400 includes a power supply 402 that powers a control circuit 404 and a light emitting device 406, which can be any one of the above-described light emitting devices 100, 200, or 300. The control circuit 404 controls the light emitting device 406 to emit light 408 having customized parameters for illuminating the plant 410 to promote its growth.

[0141] Figure 16 is a schematic diagram of a lighting system 500 for promoting plant growth according to some embodiments of the present disclosure. The lighting system 500 in these embodiments is similar to Figure 14The lighting system 400 shown, and further includes a sensor 412 for monitoring the growth of the plant 410, such as a light sensor for monitoring the light 414 reflected from the plant 410, and provides feedback to the control circuit 404 for adjusting the light parameters as described above to optimize the lighting configuration to better promote the growth of the plant 410.

[0142] In some embodiments, the light-emitting layer 104 can be a transparent LED layer, and the light-emitting device 100, 200, or 300 can further include a solar cell layer “behind” the light-emitting layer 104 (i.e., between the substrate 102 and the light-emitting layer 104), the solar cell layer having one or more photovoltaic cells (also referred to as “solar cells”) for converting light energy into electrical energy, and an electronic power converter layer behind the solar cell layer. Details of the solar cell layer and the electronic power converter layer are described in the applicant's co-pending U.S. Provisional Patent Application No. 62 / 831,828, titled “Hybrid Energy Devices, Systems, and Methods Thereof”, the content of which is incorporated herein by reference in its entirety.

[0143] For example, Figure 17 An example of a solar cell layer 540 including a plurality of sub-layers is shown. As shown, the solar cell layer 500 in this example includes an anode sub-layer 542 made of a suitable material such as indium tin oxide (ITO), a sub-layer of zinc oxide (ZnO) 544, poly(ethylenimine) and poly(ethylenimine) ethoxylated (i.e., PEIE) 546, an organic solar cell sub-layer 548 such as a polymer solar cell sub-layer, a sub-layer such as a bulk heterojunction (BHJ), an organic solar cell sub-layer of molybdenum trioxide (MoO3) 550, and a cathode sub-layer 552 made of a suitable material such as silver (Ag) or aluminum (Al). The anode 542 and the cathode 552 are electrically connected to other layers such as an electronic power converter layer.

[0144] Illumination system having a controllable illumination pattern

[0145] Figure 18 A light-emitting device 600 is shown that is used as a lighting or light source with a controlled lighting pattern by precisely controlling the light deflection angle using a metasurface or other light control structure in some embodiments. The illumination from the lighting system 600 is distributed onto an image plane 612 according to a specific pattern, where one or more objects such as one or more plants are located in the image plane 612.

[0146] For ease of annotation, the axes x and y represent the orthogonal axes defining the image plane 612, the z-axis is the axis along the controllable lighting structure 100 and the image plane 612, and is orthogonal to the x and y axes (i.e., orthogonal to the image plane 612), the y deflection angle θ is the angle between the y-axis and the projection of the light beam 610 onto the image plane 612, and the z deflection angle is the angle between the z-axis and the projection of the light beam 610 onto the x-z plane.

[0147] The light-emitting device 600 is similar to Figure 4 the light-emitting device 100 shown, and includes a light-emitting layer 104 having one or more LEDs (not shown) and a light conversion layer 106 in front of the light-emitting layer 104, such as a Topological Center Vector Control Panel (TVCP) layer in these embodiments. Although Figure 18 not shown in Figure 4 the light-emitting device 100 shown.

[0148] The light-emitting layer 104 includes an LED array as a light source and emits a plurality of light beams 610 that pass through the TVCP 106 toward the image plane 612.

[0149] The TVCP 106 includes one or more light conversion units 122 (also referred to as "lenses" in these embodiments; Figure 18 not shown in ), arranged in a predefined pattern, where each light conversion unit 122 includes a metasurface. Each light conversion unit 122 of the TVCP 106 controls the direction of the light beam 610 passing through by controlling the deflection angle θ of the light beam 610 and

[0150] to adjust the azimuth angle, elevation angle, and angle of the light cone 610 in the image plane 612. The TVCP 106 effectively breaks the symmetry of the light distribution that would otherwise exist on the image plane 612 (see Figure 2). Additionally, small changes in the deflection angle θ and will result in significant changes in the light intensity distribution on the image plane 612. Thus, with a well-configured TVCP 106, the lighting system 600 can use a plurality of light beams emitted from the light-emitting layer 104 through the TVCP 106 to a plurality of predetermined incident points distributed on the image plane 612 to generate almost any light intensity distribution in a target illumination area on the image plane 612 as needed.

[0151] The illumination pattern (e.g., the size and shape of the target illumination area and the light intensity distribution therein) and the number of light sources (e.g., LEDs) determine the positions of the predetermined incident points, which can be calculated by using appropriate optimization methods to optimize an appropriate cost function subject to the constraint that all incident points must be within the target illumination area.

[0152] For example, to obtain a uniform (or more precisely, almost uniform) light intensity distribution, the Normalized Mean Square Error (NMSE) of the light intensity distribution

[0153]

[0154] can be used as a cost function, where μ is the average light intensity on the image plane 612, I(x i ) is the light intensity of the i-th pixel, and N is the total number of pixels in the target illumination area on the image plane 612. An appropriate optimization method can be used to calculate the deflection angle θ of each light beam 610 that minimizes the NMSE under the constraint that all incident points must be within the target illumination area and (which determines the position of its incident point).

[0155] Figure 19 shows the formation of the cost function in one example, where a uniform illumination pattern within the circular target illumination area 622 on the image plane 612 is generated. Those skilled in the art will understand that the cost function for other illumination patterns can be formed similarly.

[0156] In Figure 19 the example shown, the illumination system 600 can use eight (8) light beams to emit towards respective incident points 624 distributed on two concentric circles 626A and 626B (four points on each circle) within the circular area 622 of the image plane 612 at a uniform angular interval.

[0157] (1) Any suitable optimization method, such as an artificial intelligence (AI) algorithm, a machine learning algorithm, a gradient descent (GD) method, simulated annealing (SA), and / or similar methods, can be used to find the global (or near-global) minimum of the NMSE of equation (1) and the corresponding deflection angle θ of each light beam 610 and

[0158] (1) Figure 20 is a flowchart showing the steps of a process 640 for using the GD method with the following predefined parameters in the optimization to find the global (or near-global) minimum of the NMSE of equation (1):

[0159] · The number of LEDs in the light-emitting layer 104;

[0160] · The field of view (FOV) direction and angular span of each LED;

[0161] · The shape of the target illumination area on the image plane 612;

[0162] · The size of the target illumination area;

[0163] · The distance between the light source and the target illumination area;

[0164] · The GD learning rate; and

[0165] · The maximum number of iterations.

[0166] Those skilled in the art will understand that the above parameters can be customized by the user or determined by the settings of system 600 before process 640 begins.

[0167] As Figure 20 shown, after process 640 begins (step 642), the above parameters are loaded (step 644), and the initial state of each beam 610 is randomly selected (e.g., an initial value set for the state variable )(step 646).

[0168] At step 648, the gradient of the cost function in the current state with respect to the state variables of all beams 610 is calculated. Then, all the state variables of beams 610 are "moved" in the direction opposite to the product of the gradient value of the current state and the learning rate (i.e., change the values of the state variables )(step 650).

[0169] At step 652, process 640 checks whether the number of iterations has reached the maximum number of iterations (predetermined by the system or the user). If the number of iterations has reached the maximum number of iterations, the optimization is complete, and then process 640 ends (step 654).

[0170] If at step 652, the number of iterations has not reached the maximum number of iterations, then process 640 goes to step 656 to check whether the incident point of any beam 610 is outside the target illumination area. If not, process 640 returns to step 648 to further "move" the state variables of beam 610

[0171] If at step 656, it is determined that the incident point of one or more beams 610 is outside the target illumination area, then process 640 recalculates the values of the state variables of one or more beams 610 to position its incident point at the boundary of the target illumination area in the direction opposite to the gradient value, and defines one or more beams as fixed beams (i.e., their state variables will no longer be used for optimization)(step 658). Then, process 640 randomly selects the initial state of each remaining beam 610 (e.g., an initial value set for the state variable )(step 660), and returns to step 648 for further optimization.

[0172] Process 640 can loop through the above steps one or more times, and according to the maximum number of iterations, finally stop the trial and achieve the global (or near-global) minimum of NMSE. Then, the state variables of each beam 610 The corresponding value is used to configure the optical transformation unit 122 of the TVCP 106.

[0173] In some embodiments, the optimization process may divide the light beams into multiple groups. For example, in Figure 19 the example shown, the optimization process may divide the light beams into two groups, each group including four light beams, and their incident points are in circle 626A or 626B. Then, the optimization process may form a cost function, where the control variables that minimize the NMSE are the radii and rotation degrees of circles 626A and 626B.

[0174] Figures 21 to 25 Shows the optimization results of using the GD method to generate a uniform light intensity distribution within different-shaped target illumination areas on the image plane. The target illumination areas include a triangular illumination area ( Figure 21 ), a square illumination area ( Figure 22 ), a pentagonal illumination area ( Figure 23 ), a circular illumination area ( Figure 24 ), and a doughnut-shaped or annular illumination area ( Figure 25 ).

[0175] Manufacturing technology of metasurfaces

[0176] The metasurface-based TVCP 106 can be fabricated using any suitable method such as electron beam lithography. However, this technique is costly, slow, and only suitable for fabricating small metasurfaces. The TVCP 106 described above typically requires a centimeter-scale metasurface, so traditional electron beam lithography techniques may not be fast and cost-effective.

[0177] In some embodiments, deep ultraviolet (UV) lithography techniques are used to fabricate metasurfaces such as the above-described metasurface-based TVCP 106. Although deep ultraviolet lithography techniques are mature techniques in the semiconductor field, to the applicant's knowledge, they have not been used to fabricate metasurfaces.

[0178] Using this technique, a layer of chromium is deposited on a glass wafer. Then, a resist is spin-coated on the wafer, followed by UV exposure and development. Finally, the metasurface pattern is defined by etching the chromium layer. This technique allows multiple metasurfaces to be fabricated on a large wafer through a single process, resulting in a fast and cost-effective fabrication. In addition, deep ultraviolet lithography techniques can also fabricate metasurfaces in the visible and infrared wavelength ranges using silicon dioxide, titanium dioxide, or amorphous silicon.

[0179] Illumination system having a uniform illumination pattern

[0180] As described above, conventional lighting systems such as LED panels for indoor plant growth generally do not produce a uniform light distribution on plants.

[0181] In some embodiments, similar to Figure 4 and 18 the embodiments shown, by covering the front of the light-emitting layer 104 with an angle control light conversion layer 106 such as a TVCP layer, a uniform or near-uniform illumination of an illumination system 700 such as a grow light system can be obtained. As Figure 26 shown, the light-emitting layer 104 emits a plurality of light beams 702 that pass through the TVCP 106 towards an image plane (not shown). The spatial distribution of each light beam 702 can be characterized by angles β, θ, and where the angle β determines the angular span of the light beam 702, and the angles θ and determine the direction of the light beam 702.

[0182] The TVCP 106 includes one or more light conversion units 122 arranged in a predefined pattern, where each light conversion unit 122 includes a metasurface. Each light conversion unit 122 of the TVCP 106 is configured to precisely control the angles β, θ, and of the corresponding light beam 702 to arbitrarily change the angular range, height, and latitude of the light cone in the image plane. The TVCP 106 effectively breaks the symmetry of the light distribution that would otherwise exist in the image plane (e.g., see FIG. 2). The use of the TVCP 106 is powerful because small changes in the angles β, θ, and / or can produce significant differences in the intensity distribution in the image plane. Thus, almost any intensity distribution can be produced.

[0183] The illumination system 700 can be used to generate a uniform illumination pattern at the image plane and can be used as a grow light. It is noted that, for ease of fabrication and implementation, the number of metasurfaces with different designs needs to be minimized.

[0184] In some embodiments, the TVCP 106 of the uniform illumination illumination system 700 can include only two types of metasurfaces, including a set of split metasurfaces and a set of converging metasurfaces.

[0185] The split metasurface is a polarization-sensitive metasurface that changes the angles β, θ, of the light beam by directing the light of two orthogonal polarization states in opposite directions. In these embodiments, the light-emitting layer 104 (e.g., an LED light-emitting layer) emits unpolarized light, which ensures that equal power is split into two opposite directions by the split metasurface.

[0186] As Figure 27A shown, the split metasurfaces 122A and 122B of the TVCP 106 are configured to distribute the light beams 702A and 702B at the boundaries of the expected illumination pattern on the image plane (not shown), respectively.

[0187] Figure 27B Illustrates an illumination pattern 704A on the image plane, where light energy is significantly distributed along the vertical boundaries (the guided light is hereinafter referred to as "vertically boundary-focused light"). The illumination pattern 704A is created by using a segmented metasurface to split the light from the light-emitting layer to vertically guide the light to the corresponding boundaries.

[0188] Similarly, Figure 27C Illustrates an illumination pattern 704B on the image plane, where light energy is significantly distributed along the horizontal boundaries (the guided light is hereinafter referred to as "horizontally boundary-focused light"). The illumination pattern 704B is created using a 90°-rotated segmented metasurface (similar to the segmented metasurface used in Figure 27B but with the light energy distribution rotated by 90°) to split the light from the light-emitting layer to horizontally guide the light to the corresponding boundaries.

[0189] As Figure 27B shown, the horizontal / vertical border-focused light can be guided to the same target area on the image plane to allow the light guided from it to overlap and form an illumination pattern 706 where light energy is concentrated substantially along the four boundaries of the area; see the conceptual representation in Figure 28 .

[0190] As Figure 29A and 29B shown, the converging metasurface 122C is configured to modify the angle β of the light beam 702C without changing the direction of the cone of the light beam 702C. Thus, the converging metasurface 122C distributes the light beam 702C at the center of the target area on the image plane, thereby generating an illumination pattern where light energy is substantially focused at its center.

[0191] As Figure 30 shown in the conceptual representation, by using the segmented metasurfaces 122A and 122B and the converging metasurface 122C to guide the light beam to the same target area, the illumination pattern 706 (which is a combination of the illumination patterns 704A and 704B shown in Figure 28 ) and 708 can be combined to obtain a uniform light distribution in the target area.

[0192] This uniform light distribution is substantially independent of the distance between the metasurface-based TVCP 106 and the image plane 712. As Figure 31 shown, the light distribution is only scaled at different distances without compromising the uniformity of the distribution.

[0193] Figure 32 Shows an example implementation of the TVCP 106 using an array of metasurfaces 122. For ease of illustration, only two metasurfaces 122 are shown.

[0194] In these embodiments, the TVCP 106 includes a metasurface housing 722 that covers the LEDs 110 mounted on a printed circuit board (PCB) 724 of the light-emitting layer 104. The metasurface housing 722 includes a plurality of containers 726 at positions corresponding to the LEDs 110. Each container 726 includes an inwardly extending inner surface having an inner opening for receiving light emitted from the light-emitting layer and an outer opening for passing the received light, and the area of the outer opening is larger than that of the inner opening.

[0195] In these embodiments, the inner surface of the container 726 is reflective and is used to reflect light (emitted from the LEDs 110 therein) at a high angle to contribute to overall illumination, thereby improving the efficiency of overall illumination. Maximum light flux is achieved when the cross-section of the inner surface is in a parabolic shape and the LED is located at its focal point. Figure 33 is a photograph showing the metasurface housing 722 coupled to the light-emitting layer 104.

[0196] Using suitable fastening means, such as epoxy resin, glue, and / or the like, the plurality of metasurface units 122 are fixed or otherwise coupled to the containers 726 of the metasurface housing 722, thereby ensuring the alignment of the LEDs 110 and the metasurface units 122.

[0197] Polarization - selective illumination

[0198] Plants are typically composed of components arranged in an organized manner. Therefore, the light absorption by plants is often polarization-sensitive. In other words, plants may absorb more light in one particular polarization state than in another. Therefore, the use of light of a specific polarization state can optimize photosynthesis.

[0199] In some embodiments, the metasurface-based light conversion layer 106 of the growth lamp disclosed herein can be polarization-selective, which can be achieved by arranging the nanoscale structures 124 of the metasurface to have an asymmetric basic geometry 732, as Figure 34 shown. Thus, a growth lamp having such a metasurface-based light conversion layer 106 can be used to illuminate plants with light of a specific polarization state to optimize the light for photosynthesis. Generally, the metasurface of the light conversion layer 106 can be designed to illuminate plants in various polarization states (including linear polarization states, circular polarization states, and generally elliptical polarization states). Linear polarization illumination can be used to optimize the photosynthesis of plants composed of fibers oriented in a specific direction, and circular polarization illumination can be used to optimize the photosynthesis of plants composed of components having helicity.

[0200] Metasurface - based photovoltaic cell TVCP

[0201] In a solar cell, although always desirable, due to the mismatch between the spectrum of the incident light and the spectral response of the photovoltaic cell, it is difficult to achieve perfect light absorption by the photovoltaic cell. As shown in FIG. 35, the light reflection 842 occurring on the surface of the photovoltaic cell 844 also results in solar energy loss that otherwise could be absorbed by the photovoltaic cell 844.

[0202] In some embodiments, the metasurface-based TVCP can be incorporated into a photovoltaic panel having, for example, one or more silicon-based and / or one or more quantum dot photovoltaic cells, wherein the metasurface-based TVCP can be configured to effectively transmit light of a specific wavelength to the photovoltaic cell. Additionally, the metasurface-based TVCP allows for a significant reduction in the size of the photovoltaic panel.

[0203] As will be understood by those skilled in the art, a metasurface includes nanostructures. The geometry and distribution of its nanostructures can be designed or otherwise configured to meet the requirements of a particular application. For example, a metasurface can be designed to transmit a portion of the incident light of a target spectrum or otherwise pass through it, and to completely reflect another portion of the incident light out of the target spectrum.

[0204] In some embodiments as Figure 36 shown, the metasurface-based TVCP 106 can be disposed in front of a photovoltaic panel 852 having, for example, one or more silicon-based and / or quantum dot photovoltaic cells. The metasurface-based TVCP 106 includes a plurality of metasurface units (not shown) having a spectral response that matches the spectral response of the photovoltaic cell. Thus, the combination of the metasurface-based TVCP 106 and the photovoltaic panel 852 is significantly more efficient compared to using the photovoltaic panel 852 alone, because when using the photovoltaic panel 852 alone, the spectrum that is not fully absorbed may turn into heat and other undesirable effects, thereby reducing its performance. Such an arrangement or combination is particularly important for indoor photovoltaic cells that obtain light energy from artificial light sources such as LEDs, where the metasurface units can be designed to match the specific illumination spectrum of the light source and reject other light that cannot be effectively absorbed by the photovoltaic cell.

[0205] Another important application of the metasurface lies in its ability to redirect light to different directions as described above. As Figure 37 shown, the front metasurface-based TVCP 106 can be the photovoltaic panel 852, wherein the metasurface-based TVCP 106 is configured to converge the incident light rays 854 into a small area of the photovoltaic panel 852. Thus, the size of the photovoltaic panel 852 can be significantly reduced. FIG. 38 shows a prior art photovoltaic panel 844 without the metasurface-based TVCP 106 for comparison.

[0206] Hyper - directive screen using metasurfaces

[0207] Traditional screens or displays typically have a relatively wide field of view (FOV) angular span. However, in some applications, it may be desirable to limit the FOV of the display.

[0208] Here, the term FOV refers to the angular range of illumination (e.g., conical or other shapes) emitted from a component (e.g., an LED layer, a metasurface layer, etc.), where in various embodiments, the light can be used for illumination or for displaying one or more images. The FOV can be characterized by the direction of the light emitted from the component and the three-dimensional (3D) angular span.

[0209] For example, displays in vehicles or aircraft are typically only viewed by an individual. However, as shown in FIG. 39, a display 862 in a vehicle or aircraft (not shown) having a wide FOV 868 (i.e., an FOV 868 with a wide angular span) will unnecessarily emit light into the surrounding area, which may result in reduced brightness for the user 864 in front of it, wasted light energy, and interference with the person 866 adjacent to it.

[0210] Similarly, a wide FOV display used in a home or theater will illuminate the surrounding areas, such as walls and ceilings, resulting in reduced brightness for the user in front and wasted light energy.

[0211] In addition, in some applications where enhanced security or privacy is required, such as displays in ATMs, displays in banks, and laptop computer displays for users engaged in sensitive work, a highly directional display may be needed because a wide FOV display in these applications may pose security or privacy risks in addition to the problems of reduced brightness, wasted light energy, and / or interference with people adjacent to it described above.

[0212] According to some embodiments of the present disclosure, Figure 40 a super-directional screen or display 870 using a metasurface is shown. The super-directional screen 870 includes a display or display layer 872 and a metasurface panel or layer 874 in front of it.

[0213] Similar to the light transformation layer 106 described above, the metasurface panel 874 includes a plurality of metasurface units configured in an array of nanoscale structures that direct light to a desired direction so as to confine the light emitted from the display 872 within a predefined FOV 878 that is less than the FOV 876 of the display 872, thereby creating a virtual visual barrier such that only the intended person 864 can see the content shown on the display 872.

[0214] This super-directional screen 870 has several advantages, including:

[0215] · Higher brightness due to the concentrated distribution of light energy in a smaller area;

[0216] · By avoiding illumination of unintended areas and evenly distributing light energy to intended areas, the

[0217] power efficiency is improved; and

[0218] · Safety and privacy are enhanced because visual information can only be viewed by intended persons in front of it.

[0219] As described above, the metasurface can be designed to interact differently with light of different polarization states, which is achieved by fabricating nanostructures of the metasurface with an asymmetric geometry.

[0220] Figure 41 A variable field of view (VFOV) screen or display 880 in some embodiments is shown. The MFOV display 880 includes a display 872, a polarization control panel 884 in front of the display 872, and a polarization-sensitive metasurface panel 886 in front of the polarization control panel 884.

[0221] In these embodiments, the polarization control panel 884 can be implemented using a liquid crystal polarization rotator and is controlled by an adjustable control signal V for controlling the polarization of light emitted from the display 872 to either of two orthogonal polarization states.

[0222] While the MFOV display 880 is similar to Figure 11A and 11B the light-emitting device or display 200 shown, the MFOV display 880 in these embodiments does not direct light of different polarization states to different directions of the FOV like Figure 11A and 11B the light-emitting device or display 200 shown. Instead, the polarization-sensitive metasurface panel 886 in these embodiments interacts with polarized light for directing light in a first polarization state to a first FOV having a first angular span 888 and directing light in a second polarization state to form a second FOV having a second angular span 890. For example, the first angular span 888 can be a wide angular span suitable for multiple users 864 and 866 around the MFOV display 880 to view the displayed content, and the second angular span 890 can be a narrow angular span less than the first angular span 888 to allow only the user 864 to view the displayed content.

[0223] In the above embodiments, when the control signal is at the first voltage, the polarization control panel 884 polarizes all the light passing through it to the first polarization state, and when the control signal is at the second voltage, it polarizes all the light passing through it to the second polarization state. In this way, the user 864 can switch the FOV of the MFOV display 880 between the first and second angular spans for sharing the displayed content with the people adjacent to it respectively and for creating a virtual visual barrier to prevent others from viewing the displayed content.

[0224] In Figure 42 another embodiment shown, the MFOV display 880 is similar to Figure 10A and 10B the display shown. Specifically, the display 872 includes two sets of units (pixels or sub-pixels, depending on the design), where each set of units can be used to display an image.

[0225] Accordingly, each of the polarization control panel 884 and the polarization-sensitive metasurface panel 886 also includes two sets of units corresponding to the two sets of units of the display 872. Each set of units of the polarization control panel 884 is controlled by a separate control signal V1 or V2, and each set of units of the polarization-sensitive metasurface panel 886 matches a specific polarization state and guides the light with the polarization state to a specific FOV.

[0226] Thus, the display 872 can use these two sets of pixels / units to simultaneously display two images, and the polarization control panel 884 polarizes the light of the first and second images to the first and second polarization states. Then, the polarization-sensitive metasurface panel 886 guides the light in the first polarization state (i.e., the first image) to the first FOV with a wide angular span for sharing the first image with multiple people 864 and 866, and guides the light in the second polarization state (i.e., the second image) to the second FOV with a narrow angular span for preventing people 866 from viewing the second image.

[0227] For example, as Figure 43A and 43B shown, the display will simultaneously display two images 892A and 892B, where the image 892A will be displayed in the first FOV with a wide angular span and the image 892B will be displayed in the second FOV with a narrow angular span.

[0228] As Figure 43C shown, the display 872 divides the pixels into a first set of pixels 894A and a second set of pixels 894B arranged side by side for simultaneously displaying the images 892A and 892B side by side.

[0229] As Figure 43DAs shown, the polarization control panel 884 includes a plurality of polarization units 894 corresponding to the pixels of the display 872, wherein a first group of polarization units 896A corresponds to a first group of pixels 894A and is configured to polarize the transmitted light to a first polarization state, and a second group of polarization units 896B corresponds to a second group of pixels 894B and is configured to polarize the transmitted light to a second polarization state.

[0230] As Figure 43E shown, the polarization-sensitive metasurface panel 886 includes a plurality of metasurface units 898 corresponding to the polarization units 894 of the polarization control panel 884, and guides the light transmitted in the first polarization state to a first FOV (with a wide angular span) and the light transmitted in the second polarization state to a second FOV (with a narrow angular span).

[0231] As a result, the first image 892A is guided to the first FOV and the second image 892B is guided to the second FOV. As Figure 43F shown, the images 892A and 892B are visible to the user 864 located in both the first and second FOVs, and the user 866 located only in the first FOV (with a wide angular span) can only see the first image 892A. In other words, the image 892B is invisible to the user 866 located only in the first FOV.

[0232] Three - dimensional (3D) display using metasurfaces

[0233] Figure 44 A 3D display 900 using a metasurface according to some embodiments of the present disclosure is shown. As shown, the 3D display 900 includes a display 872 and a polarization-sensitive metasurface panel 886 in front of it. The display 872 displays an image by emitting unpolarized light (which generally includes two polarization states). The polarization-sensitive metasurface panel 886 is configured to guide the light in the first polarization state to a first FOV 888 and the light in the second polarization state to a second FOV 890 that is slightly laterally offset from the first FOV 888. Then, the user 864 wearing glasses with lenses polarized to different polarization states sees the first image in one eye and the second image in the other eye, where the second image has a slight perspective distortion compared to the first image, thereby creating a 3D perception of the displayed image.

[0234] In some embodiments, the 3D display 900 may further include a polarization control panel 884 sandwiched between the display 872 and the polarization-sensitive metasurface panel 886. The polarization control panel 884 alternately polarizes the light from the display 872 to the first polarization state and the second polarization state during operation.

[0235] Figure 45Shows a 3D display 920 using a metasurface according to some embodiments of the present disclosure. The 3D display 920 is similar to Figure 44 the 3D display shown. However, the polarization-sensitive metasurface panel 886 is configured to direct light in a first polarization state to a first FOV 888 that only covers the first eye of the user 864, and direct light in a second polarization state to a second FOV 890 that only covers the second eye of the user 864. Thus, the user 864 can see a first image in one eye and a second image in the other eye without wearing glasses with polarization lenses, where the second image has a slight perspective distortion compared to the first image, thereby creating a 3D perception of the displayed image.

[0236] In some embodiments, the 3D display 920 may further include a polarization control panel 884 sandwiched between the display 872 and the polarization-sensitive metasurface panel 886. The polarization control panel 884 alternately polarizes the light from the display 872 to the first polarization state and the second polarization state during operation.

[0237] Solar cell angle correction

[0238] In the prior art, solar panels may encounter sunlight reflection problems.

[0239] As understood by those skilled in the art, the incident angle of sunlight may have a significant impact on the efficiency of photovoltaic cells. As shown in FIG. 46, when sunlight 944 perpendicularly irradiates the photovoltaic cells of the solar panel 942, the photovoltaic cells of the solar panel 942 have the highest efficiency.

[0240] As shown in FIG. 47, at different times when sunlight 944 is at a non-perpendicular angle to the photovoltaic cells of the solar panel 942, a part 946 of the sunlight is reflected and the efficiency of the photovoltaic cells decreases. Therefore, the photovoltaic cells of a fixed solar panel will have different efficiencies at different times of the day and different days of the year. Although solar tracking systems have been used to improve the efficiency of photovoltaic panels by rotating the solar panels to follow the sun, such systems require tracking systems and moving parts, making them expensive to manufacture and use.

[0241] Figure 48 and 49A solar collection device 970 is shown, which includes a solar panel 972 having one or more photovoltaic cells and a plurality of TVCPs 974 in front thereof. By using polarization-sensitive metasurfaces, where the response of each TVCP 974 can be varied using an embedded polarization control panel, the plurality of TVCPs 974 can change the direction of sunlight 944 such that incident sunlight 944 at an incident angle within a predetermined range becomes perpendicular to the photovoltaic cells when impinging on the solar panel 972, thereby improving efficiency without the need for a solar tracking system or moving parts.

[0242] In some of the embodiments described above, the light-emitting device and / or system is used for plant growth, such as for indoor or outdoor plant growth. However, those skilled in the art will understand that the light-emitting device and / or system disclosed herein may alternatively be used in other applications such as streetlights.

[0243] Although the embodiments have been described above with reference to the drawings, those skilled in the art will understand that changes and modifications can be made without departing from the scope defined by the appended claims.

Claims

1. A light-emitting device, comprising: a polarization control layer including a plurality of first pixels, each first pixel configured to polarize light emitted from a light-emitting layer and allow the polarized light to pass through; and at least one light conversion layer, each light conversion layer including a plurality of second pixels, each second pixel corresponding to a respective first pixel and including a polarization-selective metasurface configured to selectively allow polarized light having a predefined polarization state from the respective first pixel to pass through.

2. The light-emitting device according to claim 1, wherein each of the one or more metasurfaces includes a plurality of nanostructures arranged in an asymmetric basic geometry.

3. The light-emitting device according to claim 1 or 2, wherein the light-emitting device is a growth lamp for promoting the growth of one or more plants.

4. The light-emitting device according to claim 1 or 2, wherein the metasurface of each second pixel is configured to selectively allow polarized light from the polarization control layer to pass through to switch between different illumination patterns or images.

5. The light-emitting device according to claim 1 or 2, wherein the metasurface of each second pixel is configured to selectively allow polarized light from the polarization control layer to pass through to generate a plurality of different illumination patterns or images at different positions.

6. The light-emitting device according to claim 1 or 2, wherein the metasurface of each second pixel is configured to adjust one or more parameters of the polarized light from the polarization control layer.

7. The light-emitting device according to claim 6, wherein the metasurface of each second pixel is configured to adjust one or more parameters of the polarized light emitted by the polarization control layer to optimize an illumination configuration for promoting the growth of one or more plants.

8. The light-emitting device according to claim 6, wherein the metasurface of each second pixel is configured to adjust one or more parameters of the polarized light emitted by the polarization control layer to display one or more images.

9. The light-emitting device according to claim 6, wherein the metasurface of each second pixel is configured to adjust one or more parameters of the polarized light from the polarization control layer to direct the polarized light to a target area to form a predefined light distribution pattern.

10. The light-emitting device according to claim 9, wherein the predefined light distribution pattern is a substantially uniform light energy distribution over the target area.

11. The light-emitting device according to claim 10, wherein the plurality of metasurfaces includes a first set of metasurfaces configured to direct polarized light from the polarization control layer to a boundary of the target area; and a second set of metasurfaces configured to direct polarized light from the polarization control layer to a center of the target area to generate a substantially uniform light energy distribution over the target area.

12. The light-emitting device according to claim 11, wherein the plurality of metasurfaces includes a first set of metasurfaces configured to direct polarized light from the polarization control layer to a first set of boundaries of the target area; and a second set of metasurfaces configured to direct polarized light from the polarization control layer to a second set of boundaries of the target area to generate a substantially uniform light energy distribution over the target area.

13. The light-emitting device according to claim 1, wherein each first pixel includes a plurality of first sub-pixels for polarizing the light emitted from the light-emitting layer into different polarization states and passing the polarized light therethrough; and / or wherein each second pixel includes a plurality of second sub-pixels for selectively passing the polarized light polarized into different polarization states from the corresponding first pixel.

14. The light-emitting device according to claim 1, wherein each first pixel is switchable to polarize the light emitted from the light-emitting layer into different polarization states and pass the polarized light therethrough; and / or wherein each second pixel is switchable to selectively pass the polarized light polarized into different polarization states from the corresponding first pixel.

15. A solar energy collection device, comprising: a photovoltaic layer having a plurality of photovoltaic cells; and a plurality of metasurface layers in front of the photovoltaic layer for guiding light to the photovoltaic layer and substantially not causing reflection on the photovoltaic layer.

16. The solar energy collection device according to claim 15, wherein the plurality of metasurface layers are configured to guide light with an incident angle within a predetermined range to be perpendicularly incident on the photovoltaic layer.

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