PATENT DOCUMENT

Publication Number: US-12153233-B1
Application Number: US-202117465458-A
Country: US
Kind Code: B1

Title: Electronic device with stacked metasurface lenses

Abstract:
Optical components such as components that emit light and components that detect light may be provided. Optical components that emit light may include displays having arrays of display pixels with respective light-emitting devices such as crystalline semiconductor light-emitting diodes. Optical components that detect light may include image sensors or other components with arrays of photodetectors. The light-emitting devices and photodetectors in the optical components may be overlapped by metalenses such as multielement metalenses. A multielement metalens may have a first metalens element formed from a first layer of nanostructures arranged and an overlapping second metalens element formed from a second layer of nanostructures. Light sources may be provided on a semiconductor and metalens nanostructures may be formed on an opposing surface of the semiconductor.

Claims:
What is claimed is: 
     
       1. An optical component, comprising:
 a light source; and 
 a multielement metalens overlapping the light source that is configured to collimate light emitted by the light source, wherein the multielement metalens comprises a first metalens element having a first layer of nanostructures and a second metalens element having a second layer of nanostructures and wherein the first metalens element has a ring shape in which the first layer of nanostructures surrounds a circular region that is free of nanostructures. 
 
     
     
       2. The optical component defined in  claim 1  wherein the light source comprises a light-emitting diode. 
     
     
       3. The optical component defined in  claim 2  wherein the light-emitting diode is characterized by a coherence length of 1-3 microns and wherein the first and second layers of nanostructures comprise nanostructures with lateral dimensions of less than 0.4 microns. 
     
     
       4. The optical component defined in  claim 1  further comprising a semiconductor layer, wherein the first metalens is formed on a first surface of the semiconductor layer and wherein the light source is formed on an opposing second surface of the semiconductor layer. 
     
     
       5. The optical component defined in  claim 1  further comprising a layer of dielectric that separates the first layer of nanostructures from the second layer of nanostructures. 
     
     
       6. The optical component defined in  claim 1  wherein the light source is configured to form a display pixel. 
     
     
       7. The optical component defined in  claim 1 , wherein the first metalens element is interposed between the second metalens element and the light source. 
     
     
       8. The optical component defined in  claim 1 , wherein a portion of the light emitted by the light source is collimated exclusively by the second metalens element. 
     
     
       9. An optical component, comprising:
 a plurality of light detectors configured to form an image sensor; and 
 a multielement metalens configured to focus light onto a light detector of the plurality of light detectors, wherein the multielement metalens comprises a first metalens element having a first layer of nanostructures and a second metalens element having a second layer of nanostructures. 
 
     
     
       10. The optical component defined in  claim 9  wherein the first and second metalens elements are uninterrupted by nanostructure-free openings. 
     
     
       11. The optical component defined in  claim 10  further comprising a layer of dielectric that separates the first layer of nanostructures from the second layer of nanostructures. 
     
     
       12. The optical component defined in  claim 9  wherein the first and second layers of nanostructures comprise nanostructures with lateral dimensions of less than 0.4 microns. 
     
     
       13. A display system, comprising:
 an array of pixels each having a respective light-emitting device; and 
 an array of multielement metalenses each overlapping a respective pixel in the array of pixels, wherein at least one metalens element in the array of multielement metalenses has nanostructures of a first refractive index separated by material of a second refractive index and wherein a third material of a third refractive index overlaps the at least one metalens element. 
 
     
     
       14. The display system defined in  claim 13  wherein each multielement metalens in the array of multielement metalenses has a first metalens element with a first layer of nanostructures overlapped by a second metalens element with a second layer of nanostructures. 
     
     
       15. The display system defined in  claim 14  wherein the array of multielement metalenses comprises a semiconductor layer having opposing first and second surfaces. 
     
     
       16. The display system defined in  claim 15  wherein the light-emitting devices comprise light-emitting diodes. 
     
     
       17. The display system defined in  claim 16  wherein the light-emitting diodes are formed on the first surface and emit light that passes through the semiconductor layer and wherein the first layer of nanostructures is formed on the second surface. 
     
     
       18. The display system defined in  claim 17  further comprising a dielectric layer between the first layer of nanostructures and the second layer of nanostructures. 
     
     
       19. The display system defined in  claim 18  wherein the first and second layers of nanostructures comprise nanostructures with lateral dimensions of less than 0.4 microns. 
     
     
       20. The display system defined in  claim 13  wherein each multielement metalens has a first metalens element with a first layer of nanostructures surrounding a nanostructure-free central region and has a second metalens element with a second layer of nanostructures that are uninterrupted by any nanostructure-free central region. 
     
     
       21. The display system defined in  claim 20  wherein the light-emitting devices comprise crystalline semiconductor light-emitting diodes. 
     
     
       22. The display system defined in  claim 13  wherein the nanostructures of the at least one metalens element have lateral dimensions of less than λ/n, where λ is the operating wavelength of the light-emitting device and where n is the greater of the first and second refractive indices. 
     
     
       23. The display system defined in  claim 13  wherein the nanostructures of the second at least one metalens element have lateral dimensions of less than λ/n, where λ is the operating wavelength of the light-emitting device and where n is the third refractive index. 
     
     
       24. The display system defined in  claim 13  wherein the nanostructures of the at least one metalens element have lateral dimensions of less than 1.5*λ/n, where λ is the operating wavelength of the light-emitting device and where n is the greater of the first and second refractive indices. 
     
     
       25. The display system defined in  claim 13  wherein the nanostructures of the at least one metalens element have lateral dimensions of less than 1.5*λ/n, where λ is the operating wavelength of the light-emitting device and where n is the third refractive index.

Description:
This application claims the benefit of provisional patent application No. 63/082,965, filed Sep. 24, 2020, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices with optical components. 
     BACKGROUND 
     Electronic devices often have optical components. Optical components such as displays are used to present images to a user. Optical components such as image sensors detect light. 
     SUMMARY 
     Optical components such as components that emit light and components that detect light may be provided for an electronic device. The optical components that emit light may include displays having arrays of display pixels with respective light-emitting devices such as crystalline semiconductor light-emitting diodes. The optical components that detect light may include image sensors or other components with arrays of photodetectors. 
     The light-emitting devices and photodetectors in the optical components may be overlapped by respective lenses. The lenses may be metalenses. In a light-emitting component such as a display, light from each display pixel may be collimated using the metalens in that pixel. In a light-detecting component such as an image sensor, light being sensed by each image sensor pixel may be focused onto the photodetector of that pixel using the metalens in the pixel. 
     The metalenses may be multielement metalenses. A multielement metalens may have a first metalens element formed from a first layer of nanostructures and a second metalens element formed from a second layer of nanostructures. The lens elements may be spaced apart in the vertical dimension and may be aligned with each other and overlap in the horizontal dimensions (e.g., the footprints of the lens elements may overlap when viewed from above). Light sources may be provided on a semiconductor surface and metalens nanostructures may be formed on an opposing surface of the semiconductor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative electronic device in accordance with an embodiment. 
         FIG.  2 A  is a top view of an illustrative metasurface having an array of nanostructures for forming a metalens in accordance with an embodiment. 
         FIG.  2 B  is a graph in which phase change has been plotted as a function of radial distance R in the lens of  FIG.  2 A  in accordance with an embodiment. 
         FIG.  2 C  is a perspective view of an illustrative cylindrical pillar nanostructure in accordance with an embodiment. 
         FIG.  2 D  is a perspective view of an illustrative rectangular pillar nanostructure in accordance with an embodiment. 
         FIG.  2 E  is perspective view of an illustrative multilayer nanostructure in accordance with an embodiment. 
         FIG.  2 F  is a top view of an illustrative metalens in accordance with an embodiment. 
         FIG.  2 G  is a diagram of an illustrative lens configuration with a ring-type phase change and phase controlled by ring width in accordance with an embodiment. 
         FIG.  2 H  is a diagram of an illustrative Fresnel lens in accordance with an embodiment. 
         FIG.  2 I  is a diagram of an illustrative metalens in accordance with an embodiment. 
         FIG.  3    is a top view of an illustrative metasurface lens without an open center region in accordance with an embodiment. 
         FIG.  4    is a top view of a view of an illustrative ring-shaped metasurface lens having an open center region that is free of nanostructures in accordance with an embodiment. 
         FIGS.  5 ,  6 ,  7 ,  8 ,  9 ,  10 , and  11    are cross-sectional side views of illustrative metasurface lenses overlapping optical components in accordance with embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with optical components. The optical components may include components that emit light such as displays and may include components that receive light such as photodetectors. 
     Displays may be used for displaying images for users. Displays may be formed from arrays of light-emitting diode pixels. The light-emitting diode pixels may be formed from thin-film organic light-emitting diodes or crystalline semiconductor light-emitting diodes. To help narrow the cone of light emitted by each pixel and thereby enhance the amount of light directed towards a viewer, the pixels may be overlapped by lenses. For example, a display may have a pixel array in which each display pixel of the array is overlapped by a respective lens. 
     Optical sensors may be formed from photodetectors in arrays (e.g., optical sensors may include image sensors and/or other optical sensors with arrays of light detectors). Optical sensors may have lenses that help gather light. As an example, an optical sensor such as an image sensor may have an array of image sensor pixels with respective photodetectors each of which is overlapped by a respective lens that focuses incoming light onto the photodetector of that image sensor pixel. 
     The lenses in an optical component may be formed using metasurfaces. Metasurface lenses, which may sometimes be referred to as metalenses, may, for example, overlap pixels in a display or light-detectors in an optical sensor. 
     A metasurface has an array of optical elements configured to control the phase, amplitude and polarization of light passing through the metasurface. The optical elements in a metasurface, which may sometimes be referred to as nanostructures, may have subwavelength dimensions and subwavelength pitch. As an example, a metasurface for a lens that is configured to operate at visible light wavelengths (e.g., wavelengths from 380 to 740 nm) may have lateral dimensions and a nanostructure element-to-element pitch (sometimes referred to as nanostructure pitch) of less than 0.3 microns, less than 0.2 microns, less than 0.15 microns, 0.05-0.3 microns, less than 0.4 microns, or other suitable subwavelength size). A metasurface lens configured to operate at blue light wavelengths may, as an example, have lateral dimensions and a nanostructure pitch of 200-250 nm. Metasurface lenses configured to operate at infrared wavelengths may have larger dimensions and nanostructure pitches (e.g., 0.5 microns). 
     Thin transparent pillars of material or other optical elements may be used in forming a metasurface. These metasurface structures, which may sometimes be referred to as nanostructures, may be formed from dielectric material or semiconductor material that is transparent at wavelengths of interest may be formed using lithographic patterning techniques, nano-imprinting, and/or other fabrication techniques. Examples of dielectric material that may be used in forming nanostructures for metalenses include organic materials (e.g., polymer) and inorganic materials (e.g., oxides such as titanium oxide, silicon oxide, aluminum oxide, niobium oxide, etc.). Some metal oxides may have relatively high refractive index values (e.g., 2.5 for titanium oxide, 2.1 for niobium oxide, etc.). Other inorganic materials may have lower refractive index values (e.g., 2-2.2 for silicon nitride). Even lower refractive index values (e.g., 1.45-1.5) may be achieved using polymers or inorganic materials such as silicon oxide. Examples of semiconductor material that may be used in forming nanostructures for metalenses include silicon and compound semiconductors such as InAlGaP (e.g., when handling red light), InGaN (e.g., when handling blue, green, and red light), and InP (e.g., for infrared wavelengths). The refractive index for semiconductors may be, e.g., 2.4-3.5. 
     In an illustrative configuration, which is sometimes described herein as an example, each metasurface lens may have a stack of two or more metasurface lens elements. For example, each metalens may have a first metalens formed from a first layer of nanostructures and may have a second metalens formed from a second layer of nanostructures that overlaps the first layer of nanostructures. 
     Optical components with arrays of multielement metalenses may be thinner and/or may exhibit enhanced performance relative to optical components with other lens designs. For example, a display with an array of multielement metalenses may use the multielement metalenses to efficiently collimate light emitted by each pixel of the display while maintaining a desired fine pixel pitch for the display pixels. An image sensor with an array of multielement metalenses may use the multielement metalenses to help enhance image sensor pixel efficiency. 
     An illustrative electronic device of the type that may incorporate optical components with multielement metalenses is shown schematically in  FIG.  1   . Illustrative electronic device  10  of  FIG.  1    may be a cellular telephone, tablet computer, laptop computer, wristwatch device, head-mounted device, or other wearable device, a television, a stand-alone computer display or other monitor, a computer display with an embedded computer (e.g., a desktop computer), a system embedded in a vehicle, kiosk, or other embedded electronic device, a media player, or other electronic equipment. 
     Device  10  may include control circuitry  20 . Control circuitry  20  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  20  may be used to gather input from sensors and other input devices and may be used to control output devices. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors and other wireless communications circuits, power management units, audio chips, application specific integrated circuits, etc. During operation, control circuitry  20  may use a display and other output devices in providing a user with visual output and other output. 
     To support communications between device  10  and external equipment, control circuitry  20  may communicate using communications circuitry  22 . Circuitry  22  may include antennas, radio-frequency transceiver circuitry (wireless transceiver circuitry), and other wireless communications circuitry and/or wired communications circuitry. Circuitry  22 , which may sometimes be referred to as control circuitry and/or control and communications circuitry, may support bidirectional wireless communications between device  10  and external equipment over a wireless link (e.g., circuitry  22  may include radio-frequency transceiver circuitry such as wireless local area network transceiver circuitry configured to support communications over a wireless local area network link, near-field communications transceiver circuitry configured to support communications over a near-field communications link, cellular telephone transceiver circuitry configured to support communications over a cellular telephone link, or transceiver circuitry configured to support communications over any other suitable wired or wireless communications link). Wireless communications may, for example, be supported over a Bluetooth® link, a WiFi® link, a wireless link operating at a frequency between 6 GHz and 300 GHz, a 60 GHz link, or other millimeter wave link, cellular telephone link, wireless local area network link, personal area network communications link, or other wireless communications link. Device  10  may, if desired, include power circuits for transmitting and/or receiving wired and/or wireless power and may include batteries or other energy storage devices. For example, device  10  may include a coil and rectifier to receive wireless power that is provided to circuitry in device  10 . 
     Device  10  may include input-output devices such as devices  24 . Input-output devices  24  may be used in gathering user input, in gathering information on the environment surrounding the user, and/or in providing a user with output. Devices  24  may include one or more displays such as display  14 . Display  14  may be an organic light-emitting diode display, a liquid crystal display, an electrophoretic display, an electrowetting display, a plasma display, a microelectromechanical systems display, a display having a pixel array formed from crystalline semiconductor light-emitting diode dies (sometimes referred to as microLEDs) or other crystalline semiconductor light-emitting diodes, and/or other display. Configurations in which display  14  is an organic light-emitting diode display are sometimes described herein as an example. 
     Sensors  16  in input-output devices  24  may include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors (e.g., a two-dimensional capacitive touch sensor integrated into display  14 , a two-dimensional capacitive touch sensor overlapping display  14 , and/or a touch sensor that forms a button, trackpad, or other input device not associated with a display), and other sensors. If desired, sensors  16  may include optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors, image sensors, fingerprint sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors, radio-frequency sensors, depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices that capture three-dimensional images), optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors that gather time-of-flight measurements, humidity sensors, moisture sensors, gaze tracking sensors, and/or other sensors. In some arrangements, device  10  may use sensors  16  and/or other input-output devices to gather user input. For example, buttons may be used to gather button press input, touch sensors overlapping displays can be used for gathering user touch screen input, touch pads may be used in gathering touch input, microphones may be used for gathering audio input, accelerometers may be used in monitoring when a finger contacts an input surface and may therefore be used to gather finger press input, etc. 
     If desired, electronic device  10  may include additional components (see, e.g., other devices  18  in input-output devices  24 ). The additional components may include haptic output devices, audio output devices such as speakers, light-emitting diodes for status indicators, light sources such as light-emitting diodes that illuminate portions of a housing and/or display structure, other optical output devices, and/or other circuitry for gathering input and/or providing output. Device  10  may also include a battery or other energy storage device, connector ports for supporting wired communication with ancillary equipment and for receiving wired power, and other circuitry. 
     Metalenses for optical components in device  10  may have multiple metalens elements each of which is formed from a respective layer of nanostructures. A top view of a portion of an illustrative nanostructure layer for forming a metalens element is shown in  FIG.  2 A . As shown in  FIG.  2 A , a layer of nanostructures  32  may be organized in an array (e.g., an array in the XY plane of  FIG.  2 A ). Nanostructures  32 , which may sometimes be referred to as optical elements or light-scattering structures may have lateral dimension (in the XY plane) of less than a wavelength of light. For example, if metalens  30  operates at a wavelength λ, the lateral dimensions of nanostructures  32  may be 10-40% of λ or less (as examples). The nanostructure pitch of nanostructures  32  (e.g., the center-to-center spacing of nanostructures  32 ) may similarly be subwavelength in size to avoid grating effects that could diffract light passing through nanostructures  32 . Configurations in which ring-shaped structures (e.g., ring-shaped structures having subwavelength widths) are used in forming lenses for optical components in device  10  may also be used. 
     Nanostructures  32  may be formed from dielectric, semiconductor, and/or other materials transparent to light at the operating wavelengths of interest for the metalens. As an example, an array of metal oxide fins (e.g. titanium dioxide fins) may be formed on a dielectric substrate and this array of metal oxide fins may be planarized by covering the fins with a layer of polymer having a lower refractive index than the metal oxide of the fins. Other nanostructures may be used in forming metalenses if desired. 
     The lens shown in  FIG.  2 A  may have a rectangular (e.g. square) outline and may be formed in an array with an associated lens pitch (sometimes referred to as pixel pitch). The array of lenses may, for example, overlap a corresponding array of display pixels or sensor pixels. Nanostructures  32  may be patterned to produce desired phase changes for light passing through the lens (e.g., phase changes that cause the nanostructures to form a lens element of a desired focal length). The graph of  FIG.  2 B  shows an illustrative phase change that may be exhibited for light traveling through the lens of  FIG.  2 A  as a function of radial distance R from the center of the lens of  FIG.  2 A . 
     Nanostructures  32  may have any suitable shape. For example, nanostructures  32  may be cylinders (e.g., posts with circular outlines as shown in  FIG.  2 C ), may be posts with rectangular outlines as shown by nanostructure  32  of  FIG.  2 D , may be rings with different profiles to form a metalens (or, if desired a Fresnel lens), etc. Each nanostructure  32  may form a separate column of height H and/or nanostructures  32  may have staircase cross-sectional profiles. For example, nanostructures  32  may each have multiple heights along the Z axis as shown by illustrative multilayer nanostructure  32  of  FIG.  2 E . This type of arrangement may be used, for example, to reduce the aspect ratio of each layer of the nanostructure. The value of height H of a given nanostructure be, as an example, 0.5-10 times the lateral dimensions of the nanostructure, more than 2 times the lateral dimensions of the nanostructure, less than 20 times the lateral dimensions of the nanostructure, etc.). Nanostructures  32  may be aligned so that their edges run parallel to the X and Y axes of  FIG.  2    and/or may be angled at non-zero angles with respect to the X and Y axes. As an example, the angular orientation of nanostructures  32  may vary as a function of position within a metalens. 
     By varying the size and shape of nanostructures  32 , the nanostructure pitch of nanostructures  32 , the angular orientation of nanostructures  32 , the material of nanostructures  32 , and/or other nanostructure characteristics as a function of position within a nanostructure layer, desired optical properties can be implemented (e.g., nanostructures  32  can be configured to alter the phase, amplitude, and/or polarization of one or more wavelengths of light passing through nanostructures  32  as desired to form a metalens element). In this way, a thin metalens with a desired focal lens, desired polarization properties, and other desired optical properties can be obtained. As an example, nanostructures  32  may, as shown in  FIG.  2 B , implement a radially varying phase change that forms a lens of a desired focal length. 
     A top view of an illustrative metalens formed from an array of nanostructures  32  is shown in  FIG.  2 F . As shown in  FIG.  2 F , the metalens may implement a ring-type phase change pattern, where the amount of phase change at each location is determined by the pillar attributes (dimensions, size, shape, etc.) at that location. The pillars may be arranged in a Cartesian array (e.g., pillars may be organized in an array having horizontal rows and vertical columns). Each pillar outline may be circular, square, or other shape that is symmetric in Cartesian coordinates to produce a non-polarized metalens or may have a rectangular outline to produce a polarizing metalens. 
     Another illustrative lens configuration is shown in  FIG.  2 G . With this type of arrangement, a ring-type phase change may be implemented in which phase is controlled by ring width. This type of lens is similar to but not identical to the Fresnel ring lens shown in  FIG.  2 H . The ring-to-ring spacing (sometimes referred to as ring pitch) between rings in the lens of  FIG.  2 G  may be subwavelength and the phase change within each period may be modulated by ring size. A first phase change from 2η to near 0 is implemented in the center of the lens using rings of a first period. A second phase change from 2π to near zero is implemented in the outer portion of the lens using rings of a second period. 
     An illustrative Fresnel lens configuration that may be used in forming a lens element for a stacked lens is shown in  FIG.  2 H . In the example of  FIG.  2 H , phase change is controlled by ring width. The phase within each period is modulated by the ring cross-sectional profile. Within the center of the lens of  FIG.  2 H , the lens exhibits a first 2π phase shift. Further 2π phase shifts may be implemented using concentric rings. 
       FIG.  2 I  is a diagram of an illustrative metalens that also exhibits a radially varying phase change. The amount of phase change achieved at each position within the lens is controlled by attributes of the nanostructures at that position (e.g., pillar size change in this example). The nanostructures may be arranged along lines that extend radially from the center of the lens (e.g., pillars may be aligned along polar coordinates). Nanostructures (e.g., pillars) may have a first period within the center of the lens, a second period in a concentric ring surrounding the center of the lens, etc. 
     Metalenses formed from nanostructures  32  may have any suitable shape. In the illustrative configuration of  FIG.  3   , metalens  30  is formed from a solid disk of nanostructures that has been truncated to form a rectangular outline (e.g., metalens  30  is formed from a solid uninterrupted square of nanostructures  32 ). In the illustrative configuration of  FIG.  4   , metalens  30  is formed from a ring of nanostructures. With this type of arrangement, the center of the ring (central region  34 ) is free of nanostructures. Ring-shaped metalenses such as metalens  30  of  FIG.  4    may have rectangular outlines (e.g., square footprints formed by truncating a radially symmetric layer of nanostructures so that the layer of nanostructures has straight orthogonal edges as shown in the solid nanostructure lens element of  FIG.  3   ) or other suitable shapes. The nanostructure-free opening in the center of the ring (region  34 ) may be circular. 
     Lenses may be stacked to form stacked multielement lenses. Each multielement lens may overlap a respective optical component (e.g., a display pixel or sensor pixel). For example, metalens elements such as metalens  30  of  FIG.  3    and/or metalens  30  of  FIG.  4    may be stacked to form multielement metalenses that overlap corresponding arrays of pixels in a display and/or that overlap corresponding arrays of optical detectors in an optical sensor. 
       FIG.  5    is a cross-sectional side view of an illustrative optical component having an array of light sources overlapped by respective multielement metalenses. As shown in  FIG.  5   , optical component  40  may have a light source such as light source  42 . Optical component  40  may be, for example, a display having an array of pixels each of which has a respective independently controlled light source such as light source  42 . 
     The pixel pitch of light sources  42  in the display may be, as an example, 10-30 microns, less than 20 microns, or other suitable pixel pitch. Light from light sources  42  may be emitted outwardly through the layers of component  40  as shown by light rays  64 . Although shown as being parallel in  FIG.  5   , rays  64  may diverge slightly (e.g., the emitted light from source  42  may initially have a relatively wide angular spread and may be collimated by lens  30  to form a narrower cone of light rays  64  at the output of layer  56 ). Light source  42  may be a light-emitting diode or other light-emitting device. 
     Component  40  has an array of multielement metalenses  30 . Each multielement metalens  30  in  FIG.  5    has a lower metalens element (metalens)  48  with a ring of nanostructures  32  and has upper metalens element  50  with a disk of nanostructure  32 . As shown by metalens element  48  of  FIG.  5   , central region  34  may be free of nanostructures  32 . 
     The layer of material forming the structures of  FIG.  5    may include polymer, inorganic dielectric and/or other materials with one or more refractive index values (e.g., refractive index values n1, n2, n3, n4, n5, n6, n7, n8, and n9). For example, metalens element  48  may have nanostructures  32  of refractive index n6 surrounded by material with a different refractive index n5, whereas overlapping metalens element  50 , which is aligned with metalens element  48  may have nanostructures  32  of refractive index n4 surrounded by material with a different refractive index n3. In some configurations, it may be desirable to configure nanostructures  32  so that nanostructure pitch is less than 2*λ/n, less than 1.5*λ/n, or less than λ/n, where λ is the operating wavelength of the metalens and n is the refractive index value of nanostructure  32  or the material interposed between adjacent nanostructures in a metalens (e.g., n5 or n6 in lens element  48 , whichever is higher, or n3 or n4 in lens element  50 , whichever is higher) or where n is the refractive index of the material overlapping the metalens element (e.g., index n7 for the material overlapping lens element  48  or index n8 for the material overlapping lens element  50 ). 
     Light source  42  may be, for example, a quantum well light-emitting diode or other crystalline semiconductor light-emitting diode or an organic light-emitting diode (OLED). Light source  42  may emit incoherent light that is characterized by a finite coherence length L with a finite value comparable to or less than lens pitch or lens dimensions (e.g., 1-3 microns, 2 microns, less than 2 microns, or other suitable value). To avoid creating a situation in which nanostructures  32  are closer to light source  42  than coherence length L, lower metalens may have a ring-shaped layer of nanostructures  32  (e.g., nanostructures  32  may be excluded from region  34 , which would be closer to light source  42  than L). The absence of nanostructures in region  34  helps increase the closest distance between light source  42  and nanostructures  32  (e.g., to a distance greater than the coherence length L) without overly increasing the thickness of lens  30  and helps avoid interference between the nanostructures of lens  48  and light source  42 . The metalens design of  FIG.  5    also avoids placing the nanostructure layers too far from light source  42 , which could necessitate overly enlarging the lateral size of the metalens elements and thereby necessitate enlarging the pixel pitch by an undesirable amount. 
     With the arrangement of  FIG.  5   , emitted light from light source  42  that lies within cone  62  is collected by lens  50  after passing through the nanostructure-free opening or region  34  in the center of lens  48 , whereas emitted light from light source  42  that lies in the outer portion of cone  60  passes through both lens  48  and lens  50 . 
     As light is emitted by light source  42  and passes through lens  30 , emitted light travels through the layers of material that make up the structures of  FIG.  5    such as layer  52 ,  54 , and  56 . Layers  52 ,  54 , and  56  may be, for example, polymer layers or other transparent layers. Layer  52  may serve as a support for the nanostructures of lens  48  and may space lens  48  a desired distance from light source  42 . Layer  54  may help establish a desired spacing between lenses  48  and  50  and may support the nanostructures of lens  50 . Layer  56  may help protect lens  50 . After passing through layer  56 , light  64  may be emitted into the material of layer  58  (e.g., air or other material). 
     In some optical component configurations, light sources  42  of a common color are arranged on separate substrates. For example, display  14  may include a red display formed from red pixels with red light sources  42  overlapped by metalenses  30  configured to collimate red light, may include a green display formed from green pixels with green light sources  42  overlapped by metalenses  30  configured to collimate green light, and may include a blue display formed from blue pixels with blue light sources  42  overlapped by metalenses  30  configured to collimate blue light. With this type of arrangement, an optical combiner system (e.g., prisms, etc.) may be use to merge red, green, and blue images for respective red, green, and blue pixel arrays (each covered with an array of multielement metalenses) to form a full-color image for viewing by a user. 
       FIG.  6    is a cross-sectional side view of an illustrative optical component (component  40 ) in an illustrative configuration in which light  64  is being collected and focused onto a light detector. Component  40  may be an optical sensor such as an image sensor having an array of image sensor pixels each of which has a light detector (e.g., one or more photodetectors) for detecting light. As shown in  FIG.  6   , component  40  may have an array of pixels each of which has a corresponding light detector  70  (e.g., a crystalline semiconductor photodetector) to detect light. Incoming light  64  for each light detector  70  is collected by a corresponding multielement metalens  30 , which includes upper lens  50  and lower lens  48 . In the  FIG.  6    example, central portion  34 P of lower lens  48  contains nanostructures  32 . Ring-shaped lenses may be used in forming one or more layers in lenses  30  for an image sensor, if desired. 
     In the examples of  FIGS.  5  and  6   , a single layer of material (layer  54 ) is located between lenses  48  and  50 . If desired, layer  54  and/or the other layers of  FIGS.  5  and  6    (e.g., layer  52  and/or layer  56 ) may be formed from multiple sublayers of different materials. 
     Illustrative alternative designs for lenses  30  are shown in  FIGS.  7  and  8   . In the example of  FIG.  7   , light source  42  is overlapped by a lower metalens  48  having a central portion  42 P that contains nanostructures  32 . In the example of  FIG.  8   , this central portion is free of nanostructures. 
     Whether using a ring-shaped lower lens such as lens  48  of  FIG.  5    and lens  48  of  FIG.  8    or a solid disk-shaped lens such as lens  48  of  FIG.  7   , the focal lengths of lenses  48  and  50  and the separation d between lenses  48  and  50  may be configured so that light emitted by source  42  is effectively collimated. If, as an example, the focal length of lens  48  is f1 and the focal lens of lens  50  is f2, light source  42  may be placed at a distance f from lens  48 , where f is determined by equation 1.
 
 f =( f 1* f 2)/( f 1+ f 2− d )  (1)
 
     In the examples of  FIGS.  5  and  7   , lens  50  has circular shape with a diameter that is equal to the diameter of lens  48 . If desired, the diameter of lens  50  may be different than the diameter of lens  48 . As shown in  FIG.  8   , for example, lens  50  may have a smaller diameter than that of lens  48  (e.g., a diameter that is slightly larger than the diameter of the nanostructure-free opening in central portion  34 P in lens  48  of  FIG.  8   ). With this type of arrangement, light in cone  62  passes through nanostructure  32  in lens  50  and is collimated exclusively by lens  50  of multielement metalens  30 , whereas light in cone  60  that falls outside of cone  62  is collimated by nanostructures  32  in lens  48 . 
     If desired, lenses  48  may be formed from nanostructures that are etched into the surface of a layer of semiconductor. The etched surface may, as an example, be the backside surface of a semiconductor layer whose opposing topside surface is used to support light sources  42 . Semiconductors tend to have high refractive index values (e.g., 2.2-3.5). The high refractive index of semiconductor structures enables enhanced index contrast with surrounding materials, which can help enhance metalens performance and potentially reduce fabrication complexity. The semiconductor layer(s) from which nanostructures are formed may be a semiconductor substrate or a semiconductor layer such as a semiconductor epitaxial layer on a substrate (e.g., a semiconductor epitaxial buffer layer on which light-emitting diodes are grown or another part of an epitaxial light-emitting-diode film stack). Semiconductor layers or other epitaxial layers grown on a substrate may be situated below the active region of the light-emitting diodes after epitaxial light-emitting diode stack growth. 
     Consider, as an example, the arrangements of  FIGS.  9 ,  10 , and  11   , in which component  40  is a display or other light-emitting device having an array of light sources  42  formed on surface  80  of semiconductor layer (semiconductor)  82 . The portion of surface  80  in component  40  that is adjacent to each light source  42  may be planar (see, e.g.,  FIG.  9   ) or may have an angled and planar cross-sectional profile ( FIG.  10   ) or an angled cross-sectional profile ( FIG.  11   ) formed by etching or other fabrication techniques. Semiconductor layer  82  has nanostructures  32  on semiconductor surface  84 , which is on the opposing side of layer  82  from surface  80 . 
     Surface  84 , which may sometimes be referred to as a backside surface during semiconductor processing operations, may be flipped to face outwardly following processing. In this orientation, light from light source  42  may be emitted through an array of multielement metalenses  30  as shown in  FIGS.  9 ,  10 , and  11   . 
     In each multielement metalens  30 , lens  50  may be formed from nanostructures  32  formed on the surface of layer  54  and may have a disk shape (e.g., a disk shape with a diameter equal to the diameter of lens  48  or less than lens  48  as described in connection with  FIG.  8   ) and/or a ring shape. Nanostructures  32  in lens  48  may likewise be configured to form a metalens without any central opening as shown in  FIGS.  9 ,  10 , and  11   ) or a ring shape (see, e.g.,  FIG.  5   ). Arrangements of the type shown in  FIGS.  9 ,  10 , and  11    may be used with light-emitting components  40  (e.g., components with light sources  42 ) and/or may be used with light detecting components (see, e.g., component  40  of  FIG.  6   , which has an array of light detectors  70  aligned with respective multielement metalenses  30 ). 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20210902
Publication Date: 20241126
Grant Date: 20241126
Priority Date: 20200924
Inventors: XIN, Xiaobin
SIZOV, DMITRY S.
OU, Fang
ZHANG, LEI
HE, LINA
LAWRENCE, NATHANIEL T.
DRZAIC, PAUL S.
BOSE, RANOJOY
ZHANG, YUEWEI
Assignee: APPLE INC
CPC Classifications: [{"code": "H10H29/142", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10H20/855", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F77/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10H29/142", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10H20/855", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B1/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/1809", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/1814", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/1809", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/1814", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L33/58", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L31/0232", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/156", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/1809", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/1814", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 93566872