PATENT DOCUMENT

Publication Number: US-11619857-B2
Application Number: US-202117330274-A
Country: US
Kind Code: B2

Title: Electrically-tunable optical filter

Abstract:
An optical device stack includes at least one of a photodetector or an optical emitter and a metasurface. The metasurface is disposed over a light-receiving surface of the photodetector or a light emission surface of the optical emitter. The metasurface includes a first conductive layer having an electrically-tunable optical property and an array of conductive nanostructures disposed on a first side of the first conductive layer. A second conductive layer is disposed on a second side of the first conductive layer. An electrical insulator is disposed between the first conductive layer and the second conductive layer. A change in an electrical bias between the metasurface and the second conductive layer, from a first electrical bias to a second electrical bias, tunes the electrically-tunable optical property from a first state to a second state, and changes an electrically-tunable optical filtering property of the metasurface.

Claims:
What is claimed is: 
     
       1. An optical device stack, comprising:
 at least one of a photodetector or an optical emitter; 
 a metasurface disposed over at least one of a light-receiving surface of the photodetector or a light emission surface of the optical emitter and including,
 a first conductive layer having an electrically-tunable optical property; and 
 an array of conductive nanostructures disposed on a first side of the first conductive layer; 
 
 a second conductive layer disposed on a second side of the first conductive layer; and 
 an electrical insulator disposed between the first conductive layer and the second conductive layer; wherein, 
 a change in an electrical bias between the metasurface and the second conductive layer, from a first electrical bias to a second electrical bias, tunes the electrically-tunable optical property from a first state to a second state, and changes an electrically-tunable optical filtering property of the metasurface. 
 
     
     
       2. The optical device stack of  claim 1 , wherein the first conductive layer comprises indium tin oxide. 
     
     
       3. The optical device stack of  claim 1 , wherein the array of conductive nanostructures comprises an array of nanowires. 
     
     
       4. The optical device stack of  claim 3 , wherein the array of nanowires comprises gold nanowires. 
     
     
       5. The optical device stack of  claim 4 , wherein the second conductive layer comprises gold. 
     
     
       6. The optical device stack of  claim 5 , wherein the electrical insulator comprises alumina. 
     
     
       7. The optical device stack of  claim 1 , further comprising:
 a silicon nitride layer; wherein, 
 the second conductive layer is disposed on the silicon nitride layer and is between the silicon nitride layer and the electrical insulator. 
 
     
     
       8. The optical device stack of  claim 1 , wherein:
 the first electrical bias is zero volts (V); and 
 when the electrically-tunable optical property is tuned to the first state, the metasurface has an optical passband peak at a visible electromagnetic radiation wavelength. 
 
     
     
       9. The optical device stack of  claim 8 , wherein the visible electromagnetic radiation wavelength is one of a red electromagnetic radiation wavelength, a green electromagnetic radiation wavelength, or a blue electromagnetic radiation wavelength. 
     
     
       10. The optical device stack of  claim 8 , wherein:
 when the electrically-tunable optical property is tuned to the second state, the metasurface has an optical passband peak at one of,
 a different visible electromagnetic radiation wavelength than when the electrically-tunable optical property is tuned to the first state; or 
 a near-infrared electromagnetic radiation wavelength. 
 
 
     
     
       11. An optoelectronic device, comprising:
 a pixel including,
 a metasurface including an array of gold nanowires disposed on a layer of indium tin oxide (ITO); 
 a layer of gold; and 
 a layer of alumina disposed between the metasurface and the layer of gold; 
 
 a voltage source electrically connected to the metasurface and the layer of gold; and 
 a controller configured to change a voltage between the metasurface and the layer of gold by programming the voltage source. 
 
     
     
       12. The optoelectronic device of  claim 11 , further comprising:
 an array of pixels including the pixel, wherein multiple pixels in the array of pixels each include,
 a respective metasurface including a respective array of gold nanowires disposed on a respective layer of ITO; 
 a respective layer of gold; and 
 a respective layer of alumina disposed between the respective metasurface and the respective layer of gold; and 
 
 a respective voltage source electrically connected to the respective metasurface and the respective layer of gold of each pixel in the multiple pixels. 
 
     
     
       13. The optoelectronic device of  claim 12 , wherein:
 the pixel is a first pixel; 
 the multiple pixels include a second pixel; and 
 the controller is configured to program respective voltage sources that are electrically connected to the first pixel and the second pixel, to apply a same voltage to the first pixel and to the second pixel at a same time. 
 
     
     
       14. The optoelectronic device of  claim 12 , wherein:
 the pixel is a first pixel; 
 the multiple pixels include a second pixel; 
 the controller is configured to program respective voltage sources that are electrically connected to the first pixel and the second pixel, to apply a first voltage to the first pixel and a second voltage to the second pixel at a same time; and 
 the first voltage is different from the second voltage. 
 
     
     
       15. The optoelectronic device of  claim 12 , wherein each pixel of the multiple pixels comprises a respective photodetector positioned to receive electromagnetic radiation through a respective metasurface. 
     
     
       16. The optoelectronic device of  claim 12 , wherein each pixel of the multiple pixels comprises a respective optical emitter positioned to emit electromagnetic radiation through a respective metasurface. 
     
     
       17. A method of characterizing ambient light, comprising:
 receiving a first set of wavelengths of the ambient light through a metasurface while the metasurface is in a first state, the metasurface comprising an array of nanowires formed on a layer of material having an electrically-tunable optical property; 
 measuring a first intensity of the first set of wavelengths; 
 applying a voltage to the metasurface to bias the metasurface to a second state different from the first state; 
 receiving a second set of wavelengths of the ambient light through the metasurface while the metasurface is in the second state; 
 measuring a second intensity of the second set of wavelengths; and 
 characterizing the ambient light using at least the first intensity and the second intensity. 
 
     
     
       18. The method of  claim 17 , wherein the layer of material having the electrically tunable optical property comprises indium tin oxide. 
     
     
       19. The method of  claim 17 , further comprising:
 applying at least one additional voltage to the metasurface to bias the metasurface to at least one respective additional state. 
 
     
     
       20. The method of  claim 17 , further comprising:
 adjusting a setting of a display responsive to the characterization of the ambient light.

Description:
FIELD 
     The described embodiments relate generally to optical filters, such as color filters. More particularly, the described embodiments relate to optical filters for optical sensors (e.g., ambient light sensors or proximity sensors) or optical emitters (e.g., flood or spot illuminators). 
     BACKGROUND 
     When sensing electromagnetic radiation, it may be necessary or useful to sense the intensity of different electromagnetic radiation wavelengths, or different ranges of electromagnetic radiation wavelengths. Typically, different electromagnetic radiation wavelengths or ranges are sensed by different optical sensors, with the electromagnetic radiation received by different optical sensors being filtered by different optical filters (e.g., different color filters) positioned in the optical reception paths of different optical sensors. 
     It may also be necessary or useful to emit different electromagnetic radiation wavelengths, or different ranges of electromagnetic radiation wavelengths, at different times. Typically, the different electromagnetic radiation wavelengths or ranges are emitted by different optical emitters, with different optical emitters being filtered by different optical filters (e.g., different color filters) positioned in the optical emission paths of the different optical emitters. 
     SUMMARY 
     Embodiments of the systems, devices, methods, and apparatus described in the present disclosure are directed to optical sensors including electrically-tunable optical filters in their optical reception paths, and optical emitters including electrically-tunable optical filters in their optical emission paths. 
     In a first aspect, the present disclosure describes an optical device stack. The optical stack may include at least one of a photodetector or an optical emitter. A metasurface may be disposed over at least one of a light-receiving surface of the photodetector or a light emission surface of the optical emitter. The metasurface may include a first conductive layer having an electrically-tunable optical property and an array of conductive nanostructures disposed on a first side of the first conductive layer. The optical stack may further include a second conductive layer on a second side of the first conductive layer and an electrical insulator disposed between the first conductive layer and the second conductive layer. A change in an electrical bias between the metasurface and the second conductive layer, from a first electrical bias to a second electrical bias, may tune the electrically-tunable optical property from a first state to a second state and change an electrically-tunable optical filtering property of the metasurface. 
     In another aspect, the present disclosure describes an optoelectronic device. The optoelectronic device may include a pixel, which in turn includes a metasurface. The metasurface may include an array of gold nanowires disposed on a layer of indium tin oxide (ITO). The pixel may also include a layer of gold and a layer of alumina disposed between the metasurface and the layer of gold. A voltage source may be electrically connected to the metasurface and the layer of gold. A controller may be configured to change a voltage between the metasurface and the layer of gold by programming the voltage source. 
     In still another aspect of the disclosure, the present disclosure describes a method of characterizing ambient light. The method may include receiving a first set of wavelengths of the ambient light through a metasurface while the metasurface is in a first state. The metasurface may include an array of nanowires formed on a layer of material having an electrically-tunable optical property. The method may also include measuring a first intensity of the first set of wavelengths; applying a voltage to the metasurface to bias the metasurface to a second state different from the first state; receiving a second set of wavelengths of the ambient light through the metasurface while the metasurface is in the second state; measuring a second intensity of the second set of wavelengths; and characterizing the ambient light using at least the first intensity and the second intensity. 
     In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG.  1    shows an isometric view of a first example optoelectronic device; 
         FIG.  2    shows an isometric view of a second example optoelectronic device; 
         FIG.  3 A  shows an elevation of an example pixel of an optoelectronic device; 
         FIG.  3 B  shows a plan view of an example array of conductive nanostructures included in the pixel described with reference to  FIG.  3 A ; 
         FIG.  3 C  shows an isometric view of an example conductive nanostructure included in the array of conductive nanostructures described with reference to  FIG.  3 A or  3 B ; 
         FIG.  3 D  shows an alternative view of the layers circumscribed by the bubble IIID in 
         FIG.  3 A ; 
         FIG.  4    shows a graph of the different optical responses that may be provided by a metasurface tuned to different representative states; 
         FIGS.  5 A and  5 B  show a first example of an electronic device; 
         FIGS.  6 A and  6 B  show a second example of an electronic device; 
         FIG.  7    shows an example block diagram of an electronic device; and 
         FIG.  8    shows an example method of characterizing ambient light. 
     
    
    
     The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures. 
     Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, separations, and positional relationships presented therebetween, are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     One type of optical sensor that may be improved when it is configured to sense different electromagnetic radiation wavelengths is the ambient light sensor (ALS). However, the area within a device that is allocated for implementing an ALS may be relatively small, and it may be beneficial to reduce the area allocated for implementing an ALS even further and/or provide more ALS functionality within the allotted area. When an electrically-tunable optical filter is positioned in the optical reception path of an ALS pixel, a single ALS pixel may be used to sense different electromagnetic radiation wavelengths (or different ranges of electromagnetic radiation wavelengths) at different times (e.g., the sensing of different electromagnetic radiation wavelengths may be time-modulated). The different electromagnetic radiation wavelengths (or ranges of wavelengths) may include different visible and/or non-visible electromagnetic radiation wavelengths. An ALS that includes a couple or a few pixels, one or more of which receive electromagnetic radiation through a respective electrically-tunable optical filter, may sense even more different electromagnetic radiation wavelengths (or more different ranges of electromagnetic radiation wavelengths) or may sense different electromagnetic radiation wavelengths (or ranges of wavelengths) quicker. 
     In some cases, the intensities of the different electromagnetic radiation wavelengths sensed by an ALS may be used to adjust the brightness or color (e.g., white point) of a display, so that the display may be viewed more easily in a particular ambient light. The intensities of the different electromagnetic radiation wavelengths sensed by an ALS may also be used to conserve power, such as by operating a display at no more than a needed brightness for a particular ambient light condition. 
     These and other aspects are described with reference to  FIGS.  1 - 8   . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
     Directional terminology, such as “top”, “bottom”, “upper”, “lower”, “front”, “back”, “over”, “under”, “above”, “below”, “left”, “right”, etc. is used with reference to the orientation of some of the components in some of the figures described below. Because components in various embodiments can be positioned in a number of different orientations, directional terminology is used for purposes of defining relative positions of various structures, and may not always define absolute positions. For example, a first structure described as being “above” a second structure and “below” a third structure is also “between” the second and third structures, and would be “above” the third structure and “below” the second structure if the stack of structures were to be flipped. Also, as used herein, the phrase “at least one of” preceding a series of items, with the term “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list. The phrase “at least one of” does not require selection of at least one of each item listed; rather, the phrase allows a meaning that includes one or more of any of the items, or one or more of any combination of the items, or one or more of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to one or more of only A, only B, or only C; any combination of A, B, or C; and one or more of each of A, B, and C. Similarly, it may be appreciated that an order of elements presented for a conjunctive or disjunctive list provided herein should not be construed as limiting the disclosure to only that order provided. 
     As used herein, a “layer” refers to one or more materials that are typically, but not necessarily, parallel to the top surface and/or bottom surface of a substrate or another layer. 
       FIG.  1    shows an isometric view of a first example optoelectronic device  100 . By way of example, the device  100  may be configured as an optical sensor, an optical emitter, or an optical transceiver including both an optical sensor and an optical emitter. As an optical sensor, the device  100  may be used as an ambient light sensor, a proximity sensor, and so on. As an optical emitter, the device  100  may be used as a flood or spot illuminator for example. As an optical transceiver, the device  100  may perform the functions of both a photodetector and an optical emitter. 
     When the device  100  is configured as an optical sensor, the device  100  may include a photodetector  102  (e.g., a photodiode or phototransistor) and a metasurface  104  defining part or all of an optical stack  106  (e.g., an optical sensor stack). The metasurface  104  may be disposed over a light-receiving surface  108  of the photodetector  102  and include a layer  110  having an electrically-tunable optical property (e.g., a tunable refractive index). A controller  112  may be configured to apply an electrical bias to the metasurface  104 . For example, the controller  112  may be configured to program a voltage source  114  coupled to the metasurface  104 , which voltage source  114  is configured to apply a voltage to the metasurface  104  (e.g., via interconnect  116  including one or more conductive vias, conductive traces, wires, and so on). In some cases, the controller  112  may be configured to program the voltage source  114  in different ways, to apply different voltages to the metasurface  104 . In some cases, the controller  112  may program the voltage source  114  to provide a neutral voltage to the metasurface  104 , or may cause the metasurface  104  to be grounded, or may turn the voltage source  114  off, thereby allowing the metasurface  104  to assume an unbiased state. 
     When a first electrical bias (e.g., a first voltage) is applied to the metasurface  104 , the electrically-tunable optical property of the layer  110  may be tuned to a first state, consequently changing an electrically-tunable optical filtering property of the metasurface  104  to a first state. When a second electrical bias (e.g., a second voltage) is applied to the metasurface  104 , the electrically-tunable optical property of the metasurface  104  may be tuned to a second state, different from the first state, changing the electrically-tunable optical filtering property of the metasurface  104  to a second state, and so on. In some cases, the controller  112  may be configured to apply any number of one or more different electrical biases to the metasurface  104 , with different electrical biases tuning the electrically-tunable optical property of the layer  110  to different states, and also tuning the electrically-tunable optical filtering property of the metasurface  104  to different states. 
     In some embodiments, the electrically-tunable optical filtering property of the metasurface  104  may be an optical passband peak. Thus, when the electrically-tunable optical filtering property is in the first state, the metasurface  104  may have a first optical passband peak and, when the electrically-tunable optical filtering property is in the second state, the metasurface  104  may have a second optical passband peak, different from the first optical passband peak. In some cases, the first and second states may have first and second optical passband peaks at different visible electromagnetic radiation wavelengths (e.g., green, yellow, red, blue, and so on). In other cases, the first state of the electrically-tunable optical filtering property may be associated with a first optical passband peak at a visible electromagnetic radiation wavelength, and the second state of the electrically-tunable optical filtering property may be associated with a second optical passband peak at a near-infrared electromagnetic radiation wavelength. The first and second states may alternatively have respective optical passband peaks at different non-visible electromagnetic radiation wavelengths (e.g., infrared (IR), near-IR, or ultraviolet (UV) wavelengths) or, more generally, at any two different electromagnetic radiation wavelengths. In this manner, the metasurface  104  may function as an electrically-tunable optical filter (i.e., an electrically-tunable electromagnetic radiation filter), such as a tunable color filter. Alternatively, the electrically-tunable optical filtering property may be an optical passband width (or range of electromagnetic radiation wavelengths) or another property. 
     By tuning the electrically-tunable optical property of the layer  110 , different wavelengths of electromagnetic radiation may be allowed to pass through the metasurface  104  to the photodetector  102 , such that the passed electromagnetic radiation wavelengths may be detected and/or measured. 
     When the device  100  is configured as an optical emitter, the device  100  may include a light-emitting element  102  (e.g., a light-emitting diode (LED)) and a metasurface  104  defining part or all of an optical stack  106  (e.g., an optical emitter stack). The light-emitting element  102  may emit a range of electromagnetic radiation wavelengths, and in some cases may include a set of sub-pixels, with each sub-pixel emitting the same or different ranges of electromagnetic radiation wavelengths. The metasurface  104  may be disposed over an emission surface  108  of the light-emitting element  102  and include a layer  110  having an electrically-tunable optical property (e.g., a tunable refractive index). A controller  112  may be configured to apply an electrical bias to the metasurface  104 . For example, the controller  112  may be configured to program a voltage source  114  coupled to the metasurface  104 , which voltage source  114  applies a voltage to the metasurface  104 . The metasurface  104 , controller  112 , and voltage source  114  may all be configured and operated similarly to how they are configured and operated when the device  100  is configured as an optical sensor, to allow different wavelengths of electromagnetic radiation emitted by the light-emitting element  102  to pass through the metasurface  104 . 
     When the device  100  is configured as an optical transceiver, the device  100  may both sense and emit through the metasurface  104 . 
       FIG.  2    shows an isometric view of a second example optoelectronic device  200 . The device  200  includes an array of pixels  202 . By way of example, the pixels  202  in the array of pixels  202  are shown to be arranged in m columns and n rows (i.e., in an m×n array of pixels  202 , where m and n are the same or different integers). However, the pixels  202  may alternatively be arranged in a single column or row, in concentric circles, or in other ways. 
     The device  200  may be configured as an optical sensor or an optical emitter, or may include a subset of optical sensor pixels co-located with, or interspersed with, a subset of optical emitter pixels. Each optical sensor pixel in the array of pixels  202  (or one or multiple optical sensor pixels) may be configured similarly to the optoelectronic device described with reference to  FIG.  1    when the device is configured as an optical sensor. Each optical emitter pixel in the array of pixels  202  (or one or multiple optical emitter pixels) may be configured similarly to the optoelectronic device described with reference to  FIG.  1    when the device is configured as an optical emitter. The device  200  as a whole, or those pixels  202  that are configured to operate as an optical sensor, may be used as an ambient light sensor, a proximity sensor, a light emitting element white point or health sensor, and so on. The device  200  as a whole, or those pixels  202  that are configured to operate as an optical emitter, may be used as a flood or spot illuminator, a display, and so on. 
     In some cases, a respective voltage source  114  may be electrically coupled to the metasurface  104  of each pixel  202  (e.g., in a one-to-one relationship), such that each voltage source  114  may apply a voltage to a respective metasurface  104  of a respective pixel  202 . In other embodiments, a single voltage source (e.g., a voltage source having multiple taps) may be coupled to a subset or all of the pixels  202 . In either case, a controller  204  may be configured to program the respective voltage sources  114  (or program a singular or fewer number of voltage sources having multiple taps or outputs). 
     The controller  204  may program the voltage source(s)  114  that are electrically coupled to first and second pixels  202  such that a same voltage is applied to the first and second pixels  202  at a same time or different times, or such that a first voltage is applied to the first pixel  202  and a second voltage, different from the first voltage, is applied to the second pixel  202  (at a same time or different times). 
       FIGS.  3 A- 3 C  show an example pixel  300  of an optoelectronic device.  FIG.  3 A  shows an elevation of the pixel  300 ;  FIG.  3 B  shows a plan view of an example array of conductive nanostructures included in the pixel  300 ; and  FIG.  3 C  shows an isometric view of an example conductive nanostructure included in the array of conductive nanostructures. In some embodiments, the pixel  300  may be the optoelectronic device described with reference to  FIG.  1   . In some embodiments, the pixel  300  may be a pixel of the optoelectronic device described with reference to  FIG.  2    (and in some cases, each optical sensor pixel (or multiple optical sensor pixels) in the optoelectronic device described with reference to  FIG.  2    may be configured the same as, or similarly to, the pixel  300 ). 
     As shown in  FIG.  3 A , the pixel  300  may include a photodetector  302  (e.g., a photodiode or a phototransistor). Alternatively, the photodetector  302  may be replaced with a light-emitting element, or with both a photodetector and a light-emitting element. 
     A metasurface  304  may be disposed over a light-receiving surface  306  of the photodetector  302 . The metasurface  304  may include a first conductive layer  308  having an electrically-tunable optical property (e.g., a tunable refractive index), and an array of conductive nanostructures  310  disposed on a first side of the first conductive layer  308 . In some cases, the first conductive layer  308  may include indium tin oxide (ITO). The first conductive layer  308  may also or alternatively include boron nitride (BN), silicon (Si), a two-dimensional (2D) material (e.g., hexagonal BN (h-BN), graphene, or molybdenum disulfide (MoS 2 )), a semiconductor material, and so on. In some cases, the first conductive layer  308  may be doped or treated to change its charge carrier concentration. The array of conductive nanostructures  310  may include an array of nanowires, nanocrosses, nanoprisms, or other nanostructures. The conductive nanostructures  310  may include one or more of gold (Au), silver (Ag), aluminum (Al), or other conductive materials. 
     The pixel  300  may include a second conductive layer  312  on a second side of the first conductive layer. The second conductive layer  312  may be a continuous layer of conductive material, or the second conductive layer  312  may include an array of conductive structures (e.g., a second array of conductive nanostructures). In some cases, the second conductive layer  312  may include one or more of gold, silver, aluminum, or other conductive materials. 
     The pixel  300  may further include an electrical insulator  314  disposed between the first conductive layer  308  and the second conductive layer  312 . The electrical insulator  314  may be a continuous layer of electrically insulating material, or may include an array of electrically insulating structures. In some cases, the electrical insulator  314  may include alumina (Al 2 O 3 ). 
     Optionally, a silicon nitride (Si 3 N 4 ) layer  316  may be positioned between the photodetector  302  and the second conductive layer  312 , with the second conductive layer  312  being disposed on the silicon nitride layer  316 . 
     The metasurface  304 , electrical insulator  314 , and second conductive layer  312  form a metal-insulator-metal junction. Applying an external voltage across the junction may cause free charge carriers to be redistributed in the first conductive layer  308 , which may alter both its electrical properties (e.g., carrier concentration) and optical properties (e.g., refractive index). While the array of conductive nanostructures  310  may be engineered to provide a default narrow-band transmission/reflection filtering peak (i.e., an optical passband peak) for the metasurface  304 , by means of the chosen geometrical properties for the array of conductive nanostructures  310 , the narrow-band transmission/reflection filtering peak may be tuned to different peaks by applying different external voltages to the metasurface  304 . 
     An external voltage may be applied by a voltage source  318  that is electrically connected to the metasurface  304  and the second conductive layer  312  and, in some cases, may be connected to the array of conductive nanostructures  310  and the second conductive layer  312 . 
     A controller  320  may be used to change the electrical bias (e.g., voltage, V g ) of the metasurface  304 . For example, the controller  320  may be coupled to the voltage source  318  and may change the voltage applied to the metasurface  304  by programming the voltage source  318 . More specifically, the controller  320  may program the voltage source  318  to tune or change a voltage between the metasurface  304  and the second conductive layer  312 , or between the array of conductive nanostructures  310  and the second conductive layer  312 , or between the first conductive layer  308  and the second conductive layer  312 . 
     Changing the electrical bias (e.g., voltage) of the metasurface  304  may tune the state of the electrically-tunable optical property of the first conductive layer  308 . In some cases, the controller  320  may cause a first voltage, a second voltage, and so on to be applied to the metasurface  304 . At each voltage, the electrically-tunable optical property of the first conductive layer  308  may assume a different state. The different states may result from different carrier concentrations of the first conductive layer  308 . In some cases, one of the voltages (or other electrical biases) may be a neutral voltage, ground, or steady-state voltage of the metasurface  304  when the voltage source  318  is disconnected from the metasurface  304  or in an off state (e.g., at zero volts (V)). 
     The state of the electrically-tunable optical property of the first conductive layer  308  may influence or determine a corresponding state of an electrically-tunable optical filtering property of the metasurface  304 . When the electrically-tunable optical filtering property of the metasurface  304  is an optical passband peak, a first state of the electrically-tunable optical filtering property may be associated with a first optical passband peak at a first electromagnetic radiation wavelength. A second state of the electrically-tunable optical filtering property may be associated with a second optical passband peak at a second electromagnetic radiation wavelength. This enables the metasurface  304  to operate as an electrically-tunable optical filter (i.e., an electrically-tunable electromagnetic radiation filter), such as a tunable color filter. In some cases, both the first and second optical passband peaks may be at different visible electromagnetic radiation wavelengths (e.g., green, yellow, red, blue, and so on), or at different non-visible electromagnetic radiation wavelengths (e.g., at one or more IR, near-IR, or UV electromagnetic radiation wavelengths), or at respective visible and non-visible electromagnetic radiation wavelengths. 
     In some embodiments of the pixel  300 , the first conductive layer  308  may be formed of or include ITO; the array of conductive nanostructures  310  may be or include an array of gold nanowires; the second conductive layer  312  may be formed of or include gold; the electrical insulator  314  may be formed of or include alumina; and the second conductive layer  312  may be disposed on a silicon nitride layer  316 . 
       FIG.  3 B  shows a plan view of an example array of conductive nanostructures  310  included in the pixel  300 . In  FIG.  3 B , each conductive nanostructure  310  is shown to be a nanowire having a width (W) and a length (L). By way of example, each conductive nanostructure  310  is shown to have a square or rectangular block-like shape, with different conductive nanostructures  310  having a periodicity of P x  in an x-direction of a Cartesian coordinate system, and a periodicity of P y  in a y-direction of the Cartesian coordinate system. The separation between conductive nanostructures is S x  in the x-direction (S x =P x −W) and S y  in the y-direction (S y =P y −L). 
       FIG.  3 C  shows a perspective view of an example conductive nanostructure  310  included in the array of conductive nanostructures  310 . As shown, the conductive nanostructure  310  may have a block-like shape, with a width (W), length (L), and height (H). 
     When constructing the pixel  300 , the parameters W, L, H, Px, Py, Sx, and Sy may all be adjusted to set a default optical passband peak for the metasurface  304 . The default optical passband peak is an optical passband peak (or state) that exists when the metasurface  304  is biased to a neutral voltage, ground, or steady-state voltage that may exist when the voltage source  318  is disconnected from the metasurface  304  or in an off state (e.g., at zero volts (V)). 
       FIG.  3 D  shows an alternative view of the layers circumscribed by the bubble IIID in  FIG.  3 A . As shown in  FIG.  3 D , the conductive nanostructures  310  may have different sizes or shapes, depending on where they are located. For example, one or more conductive nanostructures  310 - 1  near one or more peripheral portions of the pixel  300  may have larger widths or lengths (or even a larger height), and may be designed for connection (bonding) of a wire or conductive trace that connects the array of conductive nanostructures  310  to the voltage source  318 . One or more conductive nanostructures  310 - 2  positioned more interior to the pixel  300  may have smaller widths or lengths (and even smaller heights), and may be designed specifically to tune the optical characteristics of the array of conductive nanostructures  310 . 
     As also shown in  FIG.  3 D , the second conductive layer  312 , and in some cases the first conductive layer  308  and the insulator  314 , may be thinned. Thinning these layers can improve their transmissivity, reduce the height of the pixel  300 , reduce materials cost, and so on. In some embodiments, peripheral portions of the second conductive layer  312  may be made thicker than an interior portion of the second conductive layer  312 , to provide a more substantial conductive pad for connection (bonding) of a wire or conductive trace that connects the second conductive layer  312  to the voltage source  318 . 
       FIG.  4    shows a graph  400  of the different optical responses that may be provided by a metasurface tuned to different representative states. As an example, the metasurface may be the metasurface described with reference to any of  FIGS.  1 - 3 C . The horizontal axis of the graph  400  shows a range of example electromagnetic radiation wavelengths. The vertical axis shows a percentage transmission (e.g., 0.7=70%) of electromagnetic radiation through a metasurface. 
     The graphed waveforms ( 402 ,  404 ,  406 , and so on) show the optical passband and optical passband peak of the metasurface when it is electrically biased to various voltages. 
       FIGS.  5 A and  5 B  show a first example of an electronic device  500 . The device&#39;s dimensions and form factor, including the ratio of the length of its long sides to the length of its short sides, suggest that the device  500  is a mobile phone (e.g., a smartphone). However, the device&#39;s dimensions and form factor are arbitrarily chosen, and the device  500  could alternatively be any portable electronic device including, for example, a mobile phone, tablet computer, portable computer, portable music player, health monitor device, portable terminal, vehicle navigation system, robot navigation system, wearable device (e.g., a head-mounted display (HMD), glasses, watch, earphone or earbud, and so on), or other portable or mobile device. The device  500  could also be a device that is semi-permanently located (or installed) at a single location.  FIG.  5 A  shows a front isometric view of the device  500 , and  FIG.  5 B  shows a rear isometric view of the device  500 . The device  500  may include a housing  502  that at least partially surrounds a display  504 . The housing  502  may include or support a front cover  506  or a rear cover  508 . The front cover  506  may be positioned over the display  504 , and may provide a window through which the display  504  may be viewed. In some embodiments, the display  504  may be attached to (or abut) the housing  502  and/or the front cover  506 . In alternative embodiments of the device  500 , the display  504  may not be included and/or the housing  502  may have an alternative configuration. 
     The display  504  may include one or more light-emitting elements and may be configured, for example, as an LED display, an organic LED (OLED) display, a liquid crystal display (LCD), an electroluminescent (EL) display, or other type of display. In some embodiments, the display  504  may include, or be associated with, one or more touch and/or force sensors that are configured to detect a touch and/or a force applied to a surface of the front cover  506 . 
     The various components of the housing  502  may be formed from the same or different materials. For example, a sidewall  518  of the housing  502  may be formed using one or more metals (e.g., stainless steel), polymers (e.g., plastics), ceramics, or composites (e.g., carbon fiber). In some cases, the sidewall  518  may be a multi-segment sidewall including a set of antennas. The antennas may form structural components of the sidewall  518 . The antennas may be structurally coupled (to one another or to other components) and electrically isolated (from each other or from other components) by one or more non-conductive segments of the sidewall  518 . The front cover  506  may be formed, for example, using one or more of glass, a crystal (e.g., sapphire), or a transparent polymer (e.g., plastic) that enables a user to view the display  504  through the front cover  506 . In some cases, a portion of the front cover  506  (e.g., a perimeter portion of the front cover  506 ) may be coated with an opaque ink to obscure components included within the housing  502 . The rear cover  508  may be formed using the same material(s) that are used to form the sidewall  518  or the front cover  506 . In some cases, the rear cover  508  may be part of a monolithic element that also forms the sidewall  518  (or in cases where the sidewall  518  is a multi-segment sidewall, those portions of the sidewall  518  that are non-conductive). In still other embodiments, all of the exterior components of the housing  502  may be formed from a transparent material, and components within the device  500  may or may not be obscured by an opaque ink or opaque structure within the housing  502 . 
     The front cover  506  may be mounted to the sidewall  518  to cover an opening defined by the sidewall  518  (i.e., an opening into an interior volume in which various electronic components of the device  500 , including the display  504 , may be positioned). The front cover  506  may be mounted to the sidewall  518  using fasteners, adhesives, seals, gaskets, or other components. 
     A display stack or device stack (hereafter referred to as a “stack”) including the display  504  may be attached (or abutted) to an interior surface of the front cover  506  and extend into the interior volume of the device  500 . In some cases, the stack may include a touch sensor (e.g., a grid of capacitive, resistive, strain-based, ultrasonic, or other type of touch sensing elements), or other layers of optical, mechanical, electrical, or other types of components. In some cases, the touch sensor (or part of a touch sensor system) may be configured to detect a touch applied to an outer surface of the front cover  506  (e.g., to a display surface of the device  500 ). 
     In some cases, a force sensor (or part of a force sensor system) may be positioned within the interior volume below and/or to the side of the display  504  (and in some cases within the device stack). The force sensor (or force sensor system) may be triggered in response to the touch sensor detecting one or more touches on the front cover  506  (or a location or locations of one or more touches on the front cover  506 ), and may determine an amount of force associated with each touch, or an amount of force associated with the collection of touches as a whole. Alternatively, the force sensor (or force sensor system) may trigger operation of the touch sensor (or touch sensor system) in response to detecting a force on the front cover  506 . In some cases, the force sensor (or force sensor system) may be used to determine the locations of touches on the front cover  506 , and may thereby function as a touch sensor (or touch sensor system). 
     As shown primarily in  FIG.  5 A , the device  500  may include various other components. For example, the front of the device  500  may include one or more front-facing cameras  510 , speakers  512 , microphones, or other components  514  (e.g., audio, imaging, sensing components, and/or light sources) that are configured to transmit or receive signals to/from the device  500 . In some cases, a front-facing camera  510 , alone or in combination with other sensors, may be configured to operate as a bio-authentication or facial recognition sensor. The device  500  may also include various input and/or output devices  516 , which may be accessible from the front surface (or display surface) of the device  500 . In some cases, the front-facing camera  510 , I/O devices  516 , and/or other sensors of the device  500  may be integrated with a display stack of the display  504  and moved under the display  504 . 
     In some cases, one or more of the camera  510 , components  514 , and/or I/O devices  516  may include one or an array of optical sensors or optical sensor pixels, some or all of which may be configured as described in the present disclosure. The optical sensors or optical sensor pixels may be used, for example, as one or more ambient light sensors, proximity sensors, touch sensors, biometric sensors, time-of-flight sensors, depth sensors, optical signal receivers, and so on. In some cases, one or more of the display  504  and/or components  514  may include one or an array of optical emitters or optical emitter pixels, some or all of which may be configured as described in the present disclosure. The optical emitters or optical emitter pixels may be used, for example, as one or more display elements (e.g., display pixels), illuminators, optical signal transmitters, and so on. Each of the optical sensors, optical sensor pixels, optical emitters, and/or optical emitter pixels may be configured to receive or emit different electromagnetic radiation wavelengths at different times, by electrically tuning an optical property of a layer of a metasurface of the respective sensor, emitter, or pixel. 
     The device  500  may also include buttons or other input devices positioned along the sidewall  518  and/or on a rear surface of the device  500 . For example, a volume button or multipurpose button  520  may be positioned along the sidewall  518 , and in some cases may extend through an aperture in the sidewall  518 . The sidewall  518  may include one or more ports  522  that allow air, but not liquids, to flow into and out of the device  500 . In some embodiments, one or more sensors may be positioned in or near the port(s)  522 . For example, an ambient light sensor or other optical sensor, ambient pressure sensor, ambient temperature sensor, internal/external differential pressure sensor, gas sensor, particulate matter sensor, or air quality sensor may be positioned in or near a port  522 . In some cases, one or more sensors positioned near a port  522  may be an optical sensor as described herein. 
     In some embodiments, the rear surface of the device  500  may include a rear-facing camera  524  or other optical sensor or optical sensor pixel(s) (see  FIG.  5 B ). A flash or light source  526  (e.g., an optical emitter or optical emitter pixel) may also be positioned along the rear of the device  500  (e.g., near the rear-facing camera). In some cases, the rear surface of the device  500  may include multiple rear-facing cameras. 
     The camera(s), microphone(s), pressure sensor(s), temperature sensor(s), biometric sensor(s), button(s), proximity sensor(s), touch sensor(s), force sensor(s), particulate matter or air quality sensor(s), optical sensor(s), and so on of the device  500  may form parts of various sensor systems. 
       FIGS.  6 A and  6 B  show a second example of an electronic device  600 . The device&#39;s dimensions and form factor, and inclusion of a band  604 , suggest that the device  600  is an electronic watch. However, the device  600  could alternatively be any wearable electronic device.  FIG.  6 A  shows a front isometric view of the device  600 , and  FIG.  6 B  shows a rear isometric view of the device  600 . The device  600  may include a body  602  (e.g., a watch body) and a band  604 . The watch body  602  may include an input or selection device, such as a crown  614  or a button  616 . The band  604  may be used to attach the body  602  to a body part (e.g., an arm, wrist, leg, ankle, or waist) of a user. The body  602  may include a housing  606  that at least partially surrounds a display  608 . The housing  606  may include or support a front cover  610  ( FIG.  6 A ) or a rear cover  612  ( FIG.  6 B ). The front cover  610  may be positioned over the display  608 , and may provide a window through which the display  608  may be viewed. In some embodiments, the display  608  may be attached to (or abut) the housing  606  and/or the front cover  610 . In alternative embodiments of the device  600 , the display  608  may not be included and/or the housing  606  may have an alternative configuration. 
     The housing  606  may in some cases be similar to the housing described with reference to  FIGS.  5 A and  5 B , and the display  608  may in some cases be similar to the display described with reference to  FIGS.  5 A- 5 B . 
     The device  600  may include various sensor systems, and in some embodiments may include some or all of the sensor systems included in the device described with reference to  FIGS.  5 A- 5 B . In some embodiments, the device  600  may have a port  618  (or set of ports) on a side of the housing  606  (or elsewhere), and an ambient light sensor or other optical sensor, ambient pressure sensor, ambient temperature sensor, internal/external differential pressure sensor, gas sensor, particulate matter sensor, or air quality sensor may be positioned in or near the port(s)  618 . In some cases, one or more sensors positioned near a port  618  may be an optical sensor as described herein. 
     In some cases, the rear surface (or skin-facing surface) of the device  600  may include a flat or raised area  620  that includes one or more skin-facing sensors. For example, the area  620  may include a heart-rate monitor, a respiration-rate monitor, or a blood pressure monitor. The area  620  may also include an off-wrist detector or other sensor. In some cases, one or more of the skin-facing sensors may be an optical sensor as described herein. 
     In some cases, one or more cameras, sensors, light sources, or I/O devices of the device  600  (including optical sensors in its body  602 , band  604 , or band attachment mechanism) may include one or more optical sensors, optical sensor pixels, optical emitters, or optical emitter pixels, some or all of which may be configured as described in the present disclosure. The optical sensors or optical sensor pixels may be used, for example, as one or more ambient light sensors, proximity sensors, touch sensors, biometric sensors, time-of-flight sensors, depth sensors, optical signal receivers, and so on. The optical emitters or optical emitter pixels may be used, for example, as one or more display elements (e.g., display pixels), illuminators, optical signal transmitters, and so on. Each of the optical sensors, optical sensor pixels, optical emitters, and/or optical emitter pixels may be configured to receive or emit different electromagnetic radiation wavelengths at different times, by electrically tuning an optical property of a layer of a metasurface of the respective sensor, emitter, or pixel. 
       FIG.  7    shows a sample electrical block diagram of an electronic device  700 , which electronic device may in some cases take the form of the device described with reference to  FIGS.  5 A- 5 B  or  FIGS.  6 A- 6 B  and/or include the optical sensor, optical emitter, pixel, or array of pixels described with reference to any of  FIGS.  1 - 3 C and  5 A- 6 B . The electronic device  700  may include a display  702  (e.g., a light-emitting display), a processor  704 , a power source  706 , a memory  708  or storage device, a sensor system  710 , or an input/output (I/O) mechanism  712  (e.g., an input/output device, input/output port, or haptic input/output interface). The processor  704  may control some or all of the operations of the electronic device  700 . The processor  704  may communicate, either directly or indirectly, with some or all of the other components of the electronic device  700 . For example, a system bus or other communication mechanism  714  can provide communication between the display  702 , the processor  704 , the power source  706 , the memory  708 , the sensor system  710 , and the I/O mechanism  712 . 
     The processor  704  may be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions, whether such data or instructions is in the form of software or firmware or otherwise encoded. For example, the processor  704  may include a microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a controller, or a combination of such devices. As described herein, the term “processor” is meant to encompass a single processor or processing unit, multiple processors, multiple processing units, or other suitably configured computing element or elements. 
     It should be noted that the components of the electronic device  700  can be controlled by multiple processors. For example, select components of the electronic device  700  (e.g., the sensor system  710 ) may be controlled by a first processor and other components of the electronic device  700  (e.g., the display  702 ) may be controlled by a second processor, where the first and second processors may or may not be in communication with each other. 
     The power source  706  can be implemented with any device capable of providing energy to the electronic device  700 . For example, the power source  706  may include one or more batteries or rechargeable batteries. Additionally or alternatively, the power source  706  may include a power connector or power cord that connects the electronic device  700  to another power source, such as a wall outlet. 
     The memory  708  may store electronic data that can be used by the electronic device  700 . For example, the memory  708  may store electrical data or content such as, for example, audio and video files, documents and applications, device settings and user preferences, timing signals, control signals, and data structures or databases. The memory  708  may include any type of memory. By way of example only, the memory  708  may include random access memory, read-only memory, Flash memory, removable memory, other types of storage elements, or combinations of such memory types. 
     The electronic device  700  may also include one or more sensor systems  710  positioned almost anywhere on the electronic device  700 . In some cases, sensor systems  710  may be positioned as described with reference to  FIGS.  5 A- 5 B  or  FIGS.  6 A- 6 B . The sensor system(s)  710  may be configured to sense one or more type of parameters, such as, but not limited to, electromagnetic radiation (light); touch; force; heat; movement; relative motion; biometric data (e.g., biological parameters) of a user; particulate matter concentration, air quality; proximity; position; connectedness; and so on. By way of example, the sensor system(s)  710  may include a heat sensor, a position sensor, a light or optical sensor (e.g., an ambient light sensor or proximity sensor), an accelerometer, a pressure transducer, a gyroscope, a magnetometer, a health monitoring sensor, a particulate matter sensor, an air quality sensor, and so on. Additionally, the one or more sensor systems  710  may utilize any suitable sensing technology, including, but not limited to, magnetic, capacitive, ultrasonic, resistive, optical, acoustic, piezoelectric, or thermal technologies. 
     The I/O mechanism  712  may transmit or receive data from a user or another electronic device. The I/O mechanism  712  may include the display  702 , a touch sensing input surface, a crown, one or more buttons (e.g., a graphical user interface “home” button), one or more cameras (including an under-display camera), one or more microphones or speakers, one or more ports such as a microphone port, and/or a keyboard. Additionally or alternatively, the I/O mechanism  712  may transmit electronic signals via a communications interface, such as a wireless, wired, and/or optical communications interface. Examples of wireless and wired communications interfaces include, but are not limited to, cellular and Wi-Fi communications interfaces. 
       FIG.  8    shows an example method  800  of characterizing ambient light. The method  800  may be performed, for example, using the optical sensor described with reference to  FIG.  1 ,  2 ,  3 A- 3 D,  5 A- 5 B,  6 A- 6 B , or  7 . 
     At block  802 , the method  800  may include receiving a first set of wavelengths of the ambient light through a metasurface, while the metasurface is in a first state. The metasurface may include an array of nanowires formed on a layer of material having an electrically-tunable optical property (e.g., a tunable refractive index). In various embodiments, the metasurface may be configured similarly to any of the metasurfaces described herein. 
     At block  804 , the method  800  may include measuring a first intensity of the first set of wavelengths. 
     At block  806 , the method  800  may include applying a voltage (e.g., a first voltage) to the metasurface, to bias the metasurface to a second state different from the first state. 
     At block  808 , the method  800  may include receiving a second set of wavelengths of the ambient light through the metasurface, while the metasurface is in the second state. 
     At block  810 , the method  800  may include measuring a second intensity of the second set of wavelengths. 
     At block  812 , the method  800  may include characterizing the ambient light using the first intensity and the second intensity. 
     Optionally, and at block  814 , the method  800  may include applying a second voltage to the metasurface, to bias the metasurface to the first state prior to measuring the first intensity of the first set of wavelengths at block  804 . 
     Optionally, and at block  816 , the method  800  may include adjusting a setting of a display responsive to the characterization of the ambient light. 
     Optionally, the method  800  may include applying at least one additional voltage to the metasurface to bias the metasurface to at least one respective additional state. In some cases, a respective additional set of wavelengths of ambient light may be received through the metasurface while the metasurface is biased to each of the at least one additional state, and the intensity of each additional set of wavelengths may be measured. The ambient light may then be characterized using the measured intensities of any of the sets of wavelengths. 
     The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art, after reading this description, that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art, after reading this description, that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20210525
Publication Date: 20230404
Grant Date: 20230404
Priority Date: 20210525
Inventors: LI, Jiayu
LU, DAWEI
Assignee: APPLE INC
CPC Classifications: [{"code": "G01J2001/0257", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10H20/855", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F77/413", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F77/413", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F77/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F77/331", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10H20/857", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/0121", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2203/055", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L25/0753", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L25/167", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/23", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J3/2846", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J2003/1269", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0488", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/0121", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/23", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/0488", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L33/58", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/23", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L31/02327", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2203/055", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0488", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/0121", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 84195019