Patent Publication Number: US-8969778-B2

Title: Plasmonic light collectors

Description:
This application is a division of patent application Ser. No. 13/365,051, filed Feb. 2, 2012, which claims the benefit of provisional patent application No. 61/439,834, filed Feb. 4, 2011, and provisional patent application No. 61/529,584, filed Aug. 31, 2011 all of which are hereby incorporated b reference herein in their entireties. This application claims the benefit of and claims priority to patent application Ser. No. 13/365,051, filed Feb. 2, 2012, provisional patent application No. 61/439,834, tiled Feb. 4, 2011, and provisional patent application No. 61/529,584, filed Aug. 31, 2011. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and more particularly, to electronic devices having plasmonic light collectors. 
     Plasmonic effects are quantum surface field effects in which an evanescent wave of election density oscillations is generated on or near a surface of a metal or meta-material in response to incident photons. In structures designed to exhibit plasmonic effects, incoming photons incident on the plasmonic structure generate plasmons associated with high intensity electromagnetic fields within nano-scale distances from the surface of the structure. These high intensity electromagnetic, fields couple to the incoming photons and affect the path of travel of the photon near the plasmonic surface. 
     Plasmonic structures that affect visible light (i.e., light in the visible part of the electromagnetic spectrum) require lithographic patterning and material height differences on the surface of the structures with dimensions of greater than 400 nanometers. Typical semiconductor volume manufacturing facilities lack such lithography capabilities. These material height requirements have therefore restricted the use of visible light plasmonic structures in electronic devices such as imaging devices and communications devices. 
     It would therefore be desirable to be able to provide improved plasmonic structures for use in imaging and communications devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an illustrative electronic deice in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of a conventional plasmonic lens for use in plasmonic lens research. 
         FIG. 3A  is a cross-sectional side view of a portion of an illustrative imaging device having an array of plasmonic lenses in accordance with an embodiment of the present invention. 
         FIG. 3B  is a top view of an illustrative imaging device such as the imaging device of  FIG. 3A  in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of an illustrative plasmonic lens formed by implantation in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of an illustrative plasmonic lens formed by layering alternating dielectric materials in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of an illustrative plasmonic lens formed from a vertical stack of materials in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as digital cameras, computers, cellular telephones, or other electronic devices widely include imaging and communications modules. Imaging modules in these devices ma use one or more lenses to focus incoming light onto corresponding image sensors in order to capture a corresponding digital image. Communications modules in these devices may use one or more lenses to focus incoming light into transmission cables. Image sensors may include arrays of image sensor pixels. The pixels in the image sensors may include photosensitive elements such as photodiodes that convert the incoming light into digital data signals. Image sensors may have any number of pixels (e.g., hundreds or thousands or more). A typical image sensor may, for example, have millions of pixels (e.g., megapixels). In high-end equipment, image sensors with ten megapixels or more are not uncommon. Communications modules in electronic devices may include light generating transmitter elements in addition to light focusing elements (lenses) designed to direct information encoded on electromagnetic waves (light) into a communications cable. 
       FIG. 1  shows an electronic device in accordance with an embodiment of the present invention. As shown in  FIG. 1 , electronic device  10  may include a communications module such as communications module  12  for generating an transmitting communications, an imaging module such as imaging module  20  for capturing an image, and processing circuitry  26  for processing data and information captured, generated or received by communications module  12  or image module  20 . Imaging module  20  may be configured to receive incoming image light  13  from an external object. Lenses in lens array  22  may be used to focus image light  13  onto a plasmonic light collector such as plasmonic light collectors  16 . Plasmonic light collectors  16  may contain an array of image pixels that collect, filter and convert the image light into digital image data. The digital image data may be processed b processing and control circuitry  26 . 
     Circuitry  26  may be incorporated into imaging module  20  and/or may be implemented using external processing, circuitry (e.g., a microprocessor, an application-specific integrated circuit, etc.). Processing circuitry  26  may include one or more integrated circuits (e.g., image processing circuits, microprocessors, storage devices such as random-access memory and non-volatile memory, etc.) and may be implemented using components that are separate from imaging module  20  and/or that form part or imaging module  20  (e.g., circuits that form pan of an integrated circuit that includes plasmonic light collector  16  or an integrated circuit within module  20  that is associated with plasmonic light collector  16 ). Image data that has been captured by imaging module  12  may be processed and stored using processing circuitry  26 . Processed image data may, if desired, be provided to external equipment (e.g., a computer or other device) using wired and/or wireless communications paths coupled to processing circuitry  26 . 
     To provide plasmonic light collector  16  with the ability to detect light of different colors, plasmonic light collector  16  may be provided with a color filter array. Image pixels of plasmonic light collector  16  may be associated with a pattern of color filter elements in which blue elements alternate with green elements in some rows and in which green elements alternate with red elements in other rows. This is merely illustrative. Plasmonic light collector  16  may, if desired, be a grayscale image sensor or alternatively or in addition to a color filter array, plasmonic light collector  16  may be a color-sensitive image sensor in which plasmonic image pixels may be individually configured to preferably accept a given color of light. Arrangements in which plasmonic light collector  16  is a color-sensitive image sensor are sometimes described herein as an example. 
     As shown in  FIG. 1 , communications module  12  may include a light generating transmitter module such as light generator  14  (sometimes referred to herein as light generating module, light emitting module, transmitter, transmitting module, light transmitting module, etc.). Light generator  14  may, for example, include one or more a light-emitting diodes, laser transmitters or other optical transmitter. Communications module  12  may also include a plasmonic light collector such as plasmonic light collectors  16 . Plasmonic light collector  16  of communications module  12  may be used to focus light generated using light generator  14  into a communications cable such as fiber optic cable  18 . Fiber optic cable  18  may be used couple communications module  12  to a communications network such as a local area network, a telephone network, an interconnected network of computers, cable television network, etc. Processing and control circuitry  26  may be used to control light generator  14  of communications module  12  (i.e., to pass electrical signals containing information to be converted into electromagnetic signals containing the information by light generator  14 ). 
     A conventional plasmonic lens that may be used in plasmonic lens research is shown in  FIG. 2 . As shown in  FIG. 2 , plasmonic lens  30  receives incoming light  31 . Plasmonic lens  30  helps concentrate light  31  into opening  32  in plasmonic lens  30 . Plasmons may be defined as oscillations of free electrons in a material such as a noble metal, a doped dielectric material or other material having free electrons. Surface plasmons occur at or near a surface at which a metal or other material having a negative effective dielectric constant interfaces with a vacuum or other material having a positive dielectric constant. At such an interfacing surface, evanescent waves of electrons are generated due to the presence of incoming incident photons. Surface plasmons resulting from the evanescent waves of electrons interact with the incoming photons and affect the path of travel of the incoming photons. Surface features may be designed on the surface of a metal at the interface with a vacuum or other positive dielectric constant material) that purposefully guide photons such that the surface features effectively acts as a plasmonic lens (i.e., light waves are redirected through openings in the plasmonic lens through interaction with surface plasmons). 
     As shown in  FIG. 2 , conventional plasmonic lens  30  is formed from a patterned metal such as metal layer  36  formed on a substrate such as substrate  24  (e.g., a supporting structure formed from silicon). Surface features such as surface features  38  are typically configured to form concentric rings surrounding opening  32  in plasmonic lens  36 . Electromagnetic fields associated with plasmons generated near the surface of metal layer  36  cause incoming light  31  to be redirected into opening  32 . Conventional plasmonic lenses have surface features  38  having a typical height such as height H with a magnitude of less than 10 nanometers and a width W (as shown in  FIG. 2 ) of 50-200 nanometers. Current lithographic and etch procedures for producing surface features such as surface features  38  limit the use of conventional plasmonic lenses such as lens  30  in communications and imaging modules of electronic devices. Incorporating plasmonic lenses into imaging modules such as imaging module  20  of device  10  ma include forming arrays of plasmonic lenses and corresponding, image sensors as shown in  FIG. 3A . 
       FIG. 3A  is a cross-sectional side view of an imaging module such as imaging module  20  of electronic device  10  of  FIG. 1 . In the example of  FIG. 3A , lens array  22  may include one or more lenses  221  configured to focus light on the plasmonic light collector  16 . Plasmonic light collector  16  may include an array of plasmonic lenses such as plasmonic lenses  50 . Plasmonic lenses  50  may be configured to focus light onto corresponding image sensors such as image sensors  52 . Each plasmonic lens  50  may have an associated color filter such as color filters  54 . Plasmonic lenses  50  may be configured such that surface plasmons resulting from evanescent waves of electrons generated by incoming photons interact with the incoming photons and affect the path of travel of the incoming photons. Plasmonic lenses  50  may include a layer such as layer  51  formed on substrate  53 . Layer  51  may (as art example) include a metal layer formed on substrate  53 . In the example in which layer  51  includes a metal layer formed on substrate  53 , layer  51  may include surface features the surface of the layer  51  con figured to generate plasmons on the surface of layer  51  in response to light. Surface features may include one or more concentric rings on the surface of layer  51  surrounding openings such as openings  56  in layer  51  of plasmonic lens  50 . The example in which layer  51  includes a metal layer having surface features is merely illustrative. Layer  51  may be formed from materials other than metal (e.g., silicon or other dielectric, meta-materials, etc.), may be formed from layers of materials of different dielectric constants, may be formed by implantation of a material having one dielectric constant into another material having a different dielectric constant or may be otherwise formed (e.g., implanted, layered, patterned, etc.) such that, incoming photons are redirected into openings such as openings  56  in portions of plasmonic lenses  50 . Plasmonic lenses may be configured to guide a light of a single color (e.g., red light, blue light, green light, infrared light, x-ray wavelength light, ultra-violet light, etc.), a combination of individual colors, or wide continuous range of colors of light into openings  56 . 
     In an array of numerous plasmonic lenses  50  and corresponding image sensors  52 , some of the image sensors may have red filters, some may have blue color filters, some may have green color filers, some may have patterned ed color filters (e.g., Bayer pattern filters, etc.), some may have infrared-blocking filters, some may have ultraviolet light blocking filters, some may be visible-light-blocking-and-infrared-passing filters, etc. Plasmonic lenses  50  may be associated with combinations of two or more, three or more, or four or more of these filters or may have filter of only one type. Image sensors  52  may include one or more photosensitive elements such as photodiodes. In the example of  FIG. 3A , incoming light is collected by the photodiode of image sensor  52  after passing through opening  56  in plasmonic lens  50  and, if desired, through color filter  54 . Incoming light may then be converted by the photodiode into electrical charge. 
     Image sensors  52  may include components such as reset transistors charge storage nodes (also referred to as floating diffusion FD nodes) transfer transistors (transfer gates) or other components. Charge storage nodes may be implemented using a region of doped semiconductor (e.g., a doped silicon region formed in a silicon substrate by ion implantation, impurity diffusion, or other doping techniques). The doped semiconductor region (i.e., the floating diffusion FD) exhibits a capacitance that can be used to store the charge that has been transferred from a piton:Rhode which has collected light that has passed through plasmonic lens  50 . The signal associated with the stored charge on the floating diffusion node (sometimes referred to herein as image data) may be conveyed to processing and control circuitry  26  of electronic device  10  (see  FIG. 1 ) through components such as row select transistors, source-follower transistors, or other components. 
     Image data that has been captured by imaging module  20  may be processed and stored using processing and control circuitry  26 . Processed image data may, if desired, be provided to external equipment (e.g., a computer or other device) using wired and/or wireless communications paths coupled to processing and control circuitry  26 . 
     Image pixels  55  may be formed in an array of image pixels for imaging module  20 . Each image pixel  55  may include a plasmonic lens such as plasmonic lens  50 , an image sensor  52  and, if desired, a color filter such as color filter  54 . Image pixels  55  may be separated by separating structures  57 . Separating structures  5  i may be a disruptive implant formed from dielectric material such as silicon or other acceptable materials that have been processed to form barriers between components of each pixel  55 . 
     Plasmonic lenses such as plasmonic, lenses  50  of plasmonic light collector  16  have the advantage over conventional lenses that plasmonic structures used to firm one plasmonic lens  50  may overlap plasmonic structures used to form another plasmonic lens  50  without interference.  FIG. 3B  is a top-view of a plasmonic light collector such as plasmonic light collector  16  of  FIG. 3A . As shown in  FIG. 3 , plasmonic lenses  50  may be formed from one or more concentric rings  60  surrounding opening  56  in plasmonic lens  50 . Concentric rings  60  may be formed from lithographed or etched metal or other material, may be formed from implanted material having one dielectric constant in another material having a different dielectric constant, or may be formed using other suitable methods. Light having chosen frequencies (colors) may be allowed to pass through opening  56  in plasmonic lens  50  by adding more or fewer rings having ring widths and ring diameters tuned to interact with light of the chosen frequency. The example of  FIG. 3B  in which plasmonic lenses  50  of plasmonic light collector  16  have concentric rinses of material is merely illustrative. Other structures such as structures formed from layered materials in which alternating materials have different dielectric constants may be used to form plasmonic lenses  50 . 
     As shown in  FIG. 3B , plasmonic lenses  50  may be formed separately as in the example of plasmonic lenses  50 A and  50 B or may be overlapping as in the example of plasmonic lenses  50 C and  50 D. 
       FIG. 4  shows a cross-sectional side view of an illustrative plasmonic lens of the type that may be used in imaging module  20  of electronic device  10  of  FIG. 1 . In the example of  FIG. 4 , plasmonic lens  50  is formed using an implantation process (i.e., a process in which ions, noble metal atoms, other charged particles, or other suitable materials are implanted in a layer of dielectric material having a positive dielectric constant in order to form regions having negative effective dielectric constant in dielectric layer). As shown in  FIG. 4 , plasmonic lenses  50  may include a substrate support structure such as substrate support structure  70 . Substrate  70  may be formed from silicon, silicon dioxide, sapphire, aluminum oxide, of other suitable materials. Plasmonic lens  50  may include a dielectric layer such as dielectric layer  72 . Dielectric laser  72  may be formed from ally suitable dielectric (e.g., nitride, polyimide or other suitable materials). Plasmonic structures such as plasmonic structures  74  may be formed within dielectric layer  72  using implantation methods in which a noble metal (e.g., gold) or other material is implanted in dielectric layer  72  in order to form regions of dielectric layer  72  having a negative effective dielectric constant (i.e., regions with metallic properties). As an example, dielectric layer  72  may be coated with a photo-resistive material and patterned using electron beam lithography before being implanted with a suitable material (e.g., gold, titanium oxide, or other material) to form plasmonic structures  74  having a negative effective dielectric constant. 
     Plasmons that interact with incoming light ma be formed at the interface between any positive dielectric material and any negative effective dielectric material. For this reason, changes in the local dielectric function produced by plasmonic structures  74  in plasmonic lens  50  may produce the same plasmonic lens properties of the lithographed plasmonic lens of  FIG. 2 . Plasmonic lens  50  may therefore be used in any application for which plasmonic lens  30  of  FIG. 2  may be used. Plasmonic lens  50 , however, has the advantage that at least one process step (i.e., lithography of a metal layer to form nano-scale surface features) is not required. Replacing metal lithography with an implant process in the formation of plasmonic lens  50  (as described in connection with  FIG. 4 ) may provide a variety of performance control options in constructing plasmonic structures  74  (e.g., control over shape, size, depth, etc. of plasmonic structures  74 ). Plasmonic structures  74  may be formed surrounding opening  56  in plasmonic lens  50 . As an example, plasmonic structures  74  may be configured to form concentric rings surrounding opening  56  in plasmonic lens  56  such that incoming light is guided (or focused) into opening  56 . Light that has been focused into opening  56  may pass through substrate  70  and be collected by image sensor  52 . As described in connection with  FIG. 3A , image sensor  52  may include a photosensitive element such as photodiode that converts incoming light into electrical charge. An electrical signal associated with the electrical charge produced by the photodiode may be conveyed to processing and control circuitry  26  of electronic device  10  (see  FIG. 1 ) through components such as row select transistors, source-follower transistors, or other components. Plasmonic lens  50  and image sensor  52  may be combined to form a plasmonic image pixel such as plasmonic image pixel  55 . If desired, one or more plasmonic pixels  55  may be combined to form a plasmonic light collector such as plasmonic light collector  16  of imaging module  20  of device  10 . Two or more image pixels such as image pixel  55  may be combined to form an array of image pixels for plasmonic light collector  16 . Image pixels  55  may be separated from neighboring image pixels using separating structures  57 . Separating structures  57  may be formed from dielectric material such as silicon or other acceptable materials that have been processed to firm electrical barriers between components of each pixel  55 . 
       FIG. 5  shows a cross-sectional side view of another illustrative embodiment of a plasmonic lens of the type that may be used in imaging module  20  of electronic device  10  of  FIG. 1 . In the example of  FIG. 5 , plasmonic lens  50  is formed using layers of material having alternating dielectric properties e.g., a vertical stack of two or more materials or a material stack with a variation in its dielectric properties due to composition or density). As shown in  FIG. 5 , plasmonic lenses  50  may be formed from two or more layers such as layers  80  and  82 . If desired, layers  80  and  82  may be formed on the surface of substrate  70  in an alternating stack. Layers  80  and  82  may have different dielectric properties. For example, layer  80  may be a dielectric layer. Dielectric layer  80  may be formed from any suitable dielectric (e.g., nitride, polyimide or other suitable materials). Layer  82  may be formed using a noble metal (e.g., gold) or may be formed from a layer of meta-material designed to have a negative effective dielectric constant. Layers  80  and  82  may be formed into a vertical stack by sequentially applying coatings to substrate  70  (i.e., forming a coating of metal material  82  on substrate  70  followed by forming a coating of dielectric material $ 0  on top of metal layer  82  followed by forming an additional coating of metal material  82  on top of dielectric layer  80 , etc., until the desired stack has been formed). If desired, more than two layers of material having more than two corresponding effective dielectric constants may be used to control and focus incoming light in a chosen manner (e.g., to allow light of a chosen frequency to pass, to focus light on an image sensor. etc.). 
     As shown in  FIG. 5 , plasmonic lens  50  may be formed from material stack  84  (including layers  80 ,  82  and it desired, other layers) along with substrate  70 . Plasmonic lens  50  may have an opening such an opening  56 . Layers  80  and  82  may be formed such that incoming light incident on plasmonic lens  50  is focused into opening  56  due to interaction of the incoming light with plasmons formed on inner surface  86  of opening  56 . Plasmons formed at or near inner surface  86  of opening  56  (sometimes referred to as plasmonic structure  86 ) may cause incoming light to pass through substrate  70  and onto image sensor  52 . Opening  56  may be formed in plasmonic lens  50  during a layering process (i.e., layers  80 ,  82  or other layers) may be screen printed or otherwise patterned onto substrate  70 ) such that opening  56  is left uncovered. In another example, layers  80 ,  82 , or other layers may be formed onto substrate  70  and opening  56  may be opened later using a patterning method such as a lithography, dry etch, wet etch, or other suitable process to form a via or channel such as opening  56  having an (e.g., cylindrical) inner surface such as inner surface  86 . Layers  80  and  82  may, if desired, be formed from a single material having regions with differing dielectric properties due to differences in composition or density within the material. Opening  56  in a single material having regions with differing dielectric properties due to differences in composition or density within the material may be formed using a patterning method such as a lithography, dry etch, wet etch, or other suitable process to form a via or channel such as opening  56  having a cylindrical inner surface such as inner surface  86 . 
     As plasmons that interact with incoming light may be formed at the interface between any positive dielectric material and any negative effective dielectric material, the changes in the local dielectric function produced by plasmonic structure  86  opening  56  of plasmonic lens  50  may produce plasmonic lensing properties. Plasmonic lens  50 , when formed by layering (and, if desired, patterning one or more openings) of materials such as materials  80  and  82 , has the advantage that a process step (i.e., lithography of a metal layer to form nano-scale surface features) is not required. Replacing metal lithography with vertical stacking process in the formation of plasmonic lens  50  (as described in connection with  FIG. 5 ) may provide a variety of performance control options in constructing plasmonic structures  86  (e.g., control over shape, size, depth, etc. of plasmonic structures  86 ). Inner surface  86  may, for example, be substantially vertical (i.e., perpendicular to the surface of substrate  70 ) as in  86 - 1 , may be angled with respect to the surface of substrate  70  as in  86 - 3 , or may have curved surfaces having changing angles with respect to the surface of substrate  70  that change as a function of distance from the surface of substrate  70  as in  86 - 2 . Light that has been focused into opening  56  may pass through substrate  70  and be collected by image sensor  52 . 
     As described in connection with  FIG. 3A , image sensor  52  may include a photosensitive element such as photodiode that converts incoming light into electrical charge. An electrical signal associated with the electrical charge produced by the photodiode may be conveyed to processing and control circuitry  26  of electronic device  10  (see  FIG. 1 ) through components such as row select transistors, source-follower transistors, or other components. Plasmonic lens  50  and image sensor  52  may be combined to form a plasmonic image pixel such as plasmonic image pixel  55 . If desired, one or more plasmonic pixels  55  may be combined to form a plasmonic light collector such as plasmonic light collector  46  of imaging module  20  of device  10 . Two or more image pixels such as image pixel  55  may be combined to form an array of image pixels for plasmonic light collector  16 . Image pixels  55  may be separated from neighboring image pixels using separating structures  57 . Separating structures  57  may be formed from dielectric material such as silicon or other acceptable materials that have been processed to form electrical harriers between components of each pixel  55 . 
     Plasmons formed on inner surface  86  of opening  56  may interact with light that has entered opening  56  such that inner surface  86  functions as a light pipe that redirects incoming light along opening  56  without penetration of the electromagnetic fields of the light entering into layers  80  or  82 . This lack of penetration of electromagnetic fields into the materials that form the inner surface of the light pipe may enhance the efficiency with which light may be passed through opening  56  (i.e., light will not be absorbed by materials  80  and  82  as the light never contacts materials  80  and  82 ). 
       FIG. 6  shows a cross-sectional side-view of an illustrative communications module such as communications module  12  of  FIG. 1 . As shown in  FIG. 6 , communications module  12  may include a light generating transmitter module such as light generator  14  (sometimes referred to herein as light generating module, light emitting module, transmitter, transmitting module, light transmitting module. etc.), a plasmonic light collector such as plasmonic light collector  1 . 6  and a transmission cable such as fiber optic cable  18  in a housing such as housing  98 . Transmitter  14  may, for example, include one or more a light-emitting diodes, laser transmitters or other optical transmitters for generated light  90 . Communications module  12  may also include a plasmonic light collector such as plasmonic light collector  16 . Plasmonic light collector  16  of communications module  12  may be used to focus light  90  generated using optical transmitter  14  into a communications cable such as fiber optic cable  18 . Fiber optic cable  18  may be used couple communications module  12  to a communications network such as a local area network, a telephone network, an interconnected network of computers, cable television network, etc. 
     Cable  18  may be formed from a core such as core  92 . Core  92  may be formed from a transparent material such as silicon dioxide or other suitable material. Core  92  of cable  18  may be surrounded by one or more wrapping layers such as layer  94 . Layer  94  may include a dielectric layer having an index of refraction lower than the index of refraction of core  94  so that light within cable  18  reflects within cable  18  due to the principle of total internal reflection. Layer  94  may include other layers such as a plastic jacket (for example) to be used as a protective housing for cable  18 . Cable  18  may be couple to plasmonic light collector  16  using an adhesive such as adhesive  96 . Light  90  that has been generated by transmitter  14  may be focused by plasmonic structure  86  of plasmonic light collector  16  into cable  18  for transmission. Circuitry such as processing and control circuitry  26  of  FIG. 1  may be used to encode information onto electromagnetic waves (light) for transmission using transmitter  14 , plasmonic light collector  16  and cable  18  of communications module  12  of device  10 . 
     Plasmonic light collector  16  may be formed from material stack  84  (including layers  80 ,  82  and, if desired, other layers). Plasmonic light collector  16  may have one or more openings such an opening  56 . Layers  80  and  82  may be formed such that incoming light incident on plasmonic light collector  16  is focused into opening  56  due to interaction of the incoming light with plasmons formed on inner surface  86  of opening  56 . Plasmons formed at or near inner surface  86  of opening  56  (sometimes referred to as plasmonic structure  86 ) may cause incoming light to pass through into cable  18 . Opening  56  may be formed in plasmonic lens  50  during a layering process (i.e., layers  80 ,  82  or other layers) may be screen printed or otherwise patterned onto a temporary or permanent substrate) such that opening  56  is left uncovered. In another example, layers  80 ,  82 , or other layers may be formed onto a temporary or permanent substrate and opening  56  may be opened later using a patterning method such as a lithography, dry etch, wet etch, or other suitable process to form a via or channel such as opening  56  having an (e.g., cylindrical) inner surface such as inner surface  86 . Layers  80  and  82  may, if desired, be formed from a single material having regions with differing dielectric properties due to differences in composition or density within the material. Opening  56  in a single material having regions with differing dielectric properties due to differences in composition or density within the material may be formed using a patterning method such as a lithography, dry etch, wet etch, or other suitable process to form a via or channel such as opening  56  having an (e.g., cylindrical) inner surface such as inner surface  86 . 
     As plasmons that interact with incoming light may be formed at the interface between any positive dielectric material and any negative effective dielectric material, changes in the local dielectric function produced by layers  80  and  82  of plasmonic structure  86  in opening  56  may produce plasmonic lensing properties. Replacing conventional lenses or light pipes with plasmonic light collectors formed using a vertical stacking process may provide a variety of performance control options in constructing plasmonic structures  86  (e.g., control over shape, size, depth, etc. of plasmonic structures  86 ). Inner surface  86  may, for example, be substantially vertical (i.e., perpendicular to the surface of substrate  70 ) as in  86 - 1 , may be angled with respect to the surface of substrate  70  as in  86 - 3 , or may have curved surfaces having changing angles with respect to the surface of substrate  70  that change as a function of distance from the surface of substrate  70  as in  86 - 2 . The properties of plasmonic structure  86  may be chosen such that interaction between plasmons on plasmonic structure  86  and incoming light  90  limits the bandwidth (i.e., the range of frequencies) of transmission accepted into cable  18 . By choosing the properties of plasmonic structure  86  to limit the bandwidth (i.e., the range of frequencies) of transmission accepted into cable  18 , plasmonic light collector  16  may be utilized as a color filter (i.e., multiple plasmonic light collectors having different arrangements or stacking thicknesses of layers  80  and  82  of plasmonic structure  86  may provide multiple color filters for transmission into cables such as cable  18 ). 
     Various embodiments have been described illustrating electronic devices with imaging modules and/or communications modules having plasmonic light collectors. Plasmonic light collectors may be configured to exploit the interaction between incoming light and plasmons generated on a surface of the plasmonic light collector to redirect the path of the incoming light. Redirecting the incoming light may include focusing the light through openings in the plasmonic light collector onto light absorbing components such as image sensors, fiber optic transmission cables or other components. Plasmonic light collectors may be used to form plasmonic lenses associated with image pixels in an imaging module or to form plasmonic light pipes or plasmonic lenses for use in injecting or transmitting optical communications generated by a transmitter into a fiber optic cable. Plasmonic lenses may be formed by lithography of metallic surfaces, by implantation of negative dielectric constant materials into a dielectric or by stacking and patterning layers of materials having different dielectric properties such as positive and negative effective dielectric constants. Plasmonic image pixels may be smaller and more efficient than conventional image pixels. Plasmonic light guides may introduce light into transmission cables with significantly less signal loss than conventional lenses and light guides. 
     The foregoing is merely illustrative of the principles of this invention which can be practiced in other embodiments.