Au—Ag nanorods in nonpolar solvents
1. A method of preparing coated nanorods comprising:
- coating gold nanorods with silver to obtain Au@Ag nanorods;
thenfurther applying an overcoat of SiO2 to obtain Au@Ag@SiO2 nanorods; and
thenfunctionalizing the Au@Ag@SiO2 nanorods with a material to make them more hydrophobic.
Coating gold nanorods with silver and then SiO2 enables tuning of the plasmon resonance wavelength and renders them amenable to functionalization for stability in nonpolar solvents.
|OPTICAL DISPLAY DEVICE AND METHOD THEREOF|
Patent #US 20110299001A1
Current AssigneeYissum Research Development Company of the Hebrew University of Jerusalem Ltd., Merck Patent GmbH
Sponsoring EntityYissum Research Development Company of the Hebrew University of Jerusalem Ltd., Merck Patent GmbH
|PLASMONIC ENHANCEMENT OF MATERIAL PROPERTIES|
Patent #US 20130201544A1
Current AssigneeUniversity of Maryland College Park
Sponsoring EntityUniversity of Maryland College Park
|THREE DIMENSIONAL DISPLAY SYSTEM|
Patent #US 20150346522A1
Current AssigneeMerck Patent GmbH
Sponsoring EntityQlight Nanotech Ltd., Yissum Research Development Company of the Hebrew University of Jerusalem Ltd., Merck Patent GmbH
|SUPERFICIALLY POROUS MATERIALS COMPRISING A COATED CORE HAVING NARROW PARTICLE SIZE DISTRIBUTION; PROCESS FOR THE PREPARATION THEREOF; AND USE THEREOF FOR CHROMATOGRAPHIC SEPARATIONS|
Patent #US 20190015815A1
Current AssigneeWaters Technologies Corporation
Sponsoring EntityWaters Technologies Corporation
- 1. A method of preparing coated nanorods comprising:
coating gold nanorods with silver to obtain Au@Ag nanorods;
further applying an overcoat of SiO2 to obtain Au@Ag@SiO2 nanorods; and
functionalizing the Au@Ag@SiO2 nanorods with a material to make them more hydrophobic.
- View Dependent Claims (2, 3)
This Application claims the benefit of U.S. Provisional Application 62/573,718 filed on Oct. 18, 2017, and further claims the benefit as a continuation-in-part of U.S. patent application Ser. No. 16/163,399 filed on Oct. 17, 2018, the entirety of each of which is incorporated herein by reference.
Light incident on subwavelength metallic structures can set up collective oscillations of the materials'"'"' conduction electrons, termed localized surface plasmon resonances. The attributes of such resonances depend on a number of factors, including the material, size, shape, and orientation of the plasmonic structure. The strong interaction and localization of light in plasmonic structures make them attractive candidates for controlling the properties of light, including intensity, phase, polarization, direction, and spectral power distribution. In the visible spectrum, these effects can be employed for the generation and modification of color (see ref. 1). However, a large portion of prior demonstrations of plasmonic structures have shown properties that are static in time, limiting their application for real-time light modulation. Therefore, a need exists for mechanisms by which plasmonic structures can modulate light in a dynamic and controllable manner, and preferably with a fast switching time.
Application of an external electric field offers a potential means to modulate the optical properties of matter, including by imparting alignment to anisotropic materials. In general, the permanent or induced dipole moment and resulting polarizability of a molecule is too small to couple to external electric fields to overcome disordering thermal forces, preventing alignment. If anisotropic molecules are condensed into a liquid crystal phase, then the additional van der Waals forces from the near-neighbor interactions increase the polarizability to enable alignment of the molecules and control the optical properties. The electric-field-induced alignment of anisotropic molecules in liquid crystal phases has enabled disruptive technologies such as smart phones and flat screen displays.
The switching time of these materials depends on the sum of their on- and off-times. The on-time needed to align the molecules into the direction of the applied electric field is predominately set by the magnitude of the field applied, τon≈γ/εE2, where γ is the viscosity, ε is the dielectric permittivity and E is the electric field. The off-time is related to the thermal rotational diffusion of the liquid crystal molecules and typically is the limiting factor to determine the overall switching time. In the case of liquid crystals, the near-neighbor interactions create strong electrohydrodynamic coupling, leading to a slow characteristic off-time, τoff≈γd2/K≈ms, where d is the cell thickness and K is the elastic constant of the liquid crystal. This well-known limitation has constrained potential electro-optic applications for decades. A need exists for improved switching times.
Furthermore, a need exists for a wider span of tunable operating wavelengths for nanorods.
Described herein is the modulation of light by the alignment of plasmonic nanorods within an electric field. The optical anisotropy of plasmonic nanorods is employed to impart changes in the global optical response of suspensions of nanorods in unaligned versus various aligned states. Discrete volumes of plasmonic nanorod suspensions under the control of applied electric fields constitute plasmonic pixels that are used individually and/or in collection to dynamically modulate the properties of light. A notable example is in controlling the chromaticity and/or luminance of the perceived color of the pixels. The microsecond switching times of the pixels present advantages over conventional liquid-crystal-based optical devices.
Also described herein is the digital electric-field-induced switching of plasmonic nanorods between “1” and “0” orthogonal aligned states using an electro-optic fluid fiber component. Digitally switching the nanorods circumvents their thermal rotational diffusion, demonstrating an approach to achieve submicrosecond switching times. From an initial unaligned state, the nanorods can be aligned into the applied electric field direction in 110 nanoseconds. The high-speed digital switching of plasmonic nanorods integrated into an all-fiber optical component may provide novel opportunities for remote sensing and signaling applications.
In one embodiment, an optical modulator includes at least one pixel comprising a plurality of nanorods and configured to receive illumination from an illumination source; and electrodes configured to apply an electric field to the nanorods sufficient to alter their orientation and thereby modulate at least one optical property of the illumination reaching the nanorods.
In a further embodiment, an electro-optical fluid fiber component includes an inlet and an outlet configured to receive and send light, respectively; a plurality of nanorods contained between the inlet and outlet; and electrodes configured to apply an electric field to the nanorods and thereby modulate passage of the light through the fiber component, wherein the component is operable at switching speeds of one millisecond or less.
In another embodiment, a method of modulating light includes transmitting light through an electro-optical fluid fiber component comprising a plurality of nanorods and electrodes configured to apply a voltage to the nanorods, wherein the light passes through the plurality of nanorods; passing an electric field across the electrodes, thereby modulating the light as it passes through the nanorods.
In yet another embodiment, a method of preparing coated nanorods includes coating gold nanorods with silver to obtain Au@Ag nanorods; then further applying an overcoat of SiO2 to obtain Au@Ag@SiO2 nanorods; and then functionalizing the Au@Ag@SiO2 nanorods with a material to make them more hydrophobic.
Before describing the present invention in detail, it is to be understood that the terminology used in the specification is for the purpose of describing particular embodiments, and is not necessarily intended to be limiting. Although many methods, structures and materials similar, modified, or equivalent to those described herein can be used in the practice of the present invention without undue experimentation, the preferred methods, structures and materials are described herein. In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below.
As used herein, the singular forms “a”, “an,” and “the” do not preclude plural referents, unless the context clearly dictates otherwise.
As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
As used herein, the term “about” when used in conjunction with a stated numerical value or range denotes somewhat more or somewhat less than the stated value or range, to within a range of ±10% of that stated.
As used herein, the term “nanorod” refers to an oblong nanoscale object having one or more dimensions of less than or equal to 100 nanometers and an aspect ratio of length to diameter in the range of about 1.5 to about 50. Nanorods may have various shapes including spherocylinders, ellipsoids, and the like, and may be asymmetric.
As used herein, unless the context clearly dictates otherwise, the term “light” includes both visible light and light beyond the visible spectrum.
As used herein, the term “optical modulator” refers to something that changes the properties of light passing through and/or reflecting therefrom.
Dynamic Plasmonic Pixels as Optical Modulators
Suspensions of colloidal Au nanorods are dispensed within a thin liquid cell between two transparent conducting electrodes (
where θ is the angle between the nanorod long axis and the orientation of the applied electric field and the braces denote the ensemble average.
The wavelength at which the plasmon resonances occur can be adjusted through various methods, including by tailoring the nanorod aspect ratio.
For plasmon resonances in the visible spectrum, the modulation of the absorption spectrum upon nanorod alignment is manifested as a perceptible change in color and/or brightness when the nanorod suspensions are observed under illumination (for example in transmission with backlit illumination). The color modulation achieved through nanorod alignment is quantified by mapping the absorption spectra to CIE 1931 x,y chromaticity coordinates (see ref. ). As an example for one particular nanorod type whose absorption spectrum is shown in
The chromaticity and/or luminance contrast between the “off” and “on” states can be exploited for display applications. To demonstrate,
Microsecond switching times for Au nanorod alignment (three orders of magnitude faster than switching in traditional liquid crystal materials) have been demonstrated as noted below (see also refs. [4,5]), emphasizing the favorability of plasmonic nanorods for optical applications with high performance demands. Utilizing the spectral, spatial, and temporal control of plasmonically generated color as demonstrated herein provides a platform for engineering next-generation optical technologies. An optical modulator operating according to these principles might be used in any number of applications including a display device, portable electronic devices, etc.
Sub-Microsecond Electro-Optic Fluid Fiber Switches Using Electric-Field-Aligned Plasmonic Nanoparticles
A recent approach towards switching liquid crystal molecules avoided re-alignment of the molecules altogether by rapidly electrically inducing a change in the refractive index of the molecules in a liquid crystal phase. The response time of this system was 10'"'"'s of nanoseconds, yet the change in the optical properties was small and cannot be maintained for long times before the usual electric-field-induced alignment of the molecules occurs. The electric-field-induced alignment of plasmonic nanorods is a novel paradigm to anisotropic molecules in liquid crystal phases. A key advantage of plasmonic nanorods is that the polarizability of a single nanorod in a dilute suspension is adequately large to couple to an external electric field, enabling alignment and the ability to tune the optical properties at visible and near-infrared wavelengths. A significant consequence of this electro-optic mechanism is that the off-time decreases by 1,000-fold (γL3/kbT≈μs, where L is the length of the nanorod, kb is the Boltzmann constant and T is the temperature) compared to liquid crystals, due to the absence of near-neighbor interactions. The electric-field-induced alignment of plasmonic nanorods alleviates the long-standing switching time limitation of liquid crystal based devices, potentially ushering in innovative display, filter, and spatial light modulator technologies. The switching time for the plasmonic nanorods is limited to the order of microseconds, due to the thermal rotational diffusion of the nanorods when the field is switched off. To break through this limit, consider that the on-time for the nanorods can become arbitrarily small if the applied electric field is large. Therefore, if the nanorods are digitally switched between two orthogonal fields, holding the nanorods in a continuous “1” or “0” aligned state, then thermal relaxation can be circumvented, potentially leading to submicrosecond switching times. Aspects of this technique have been described in references 4 and 5, incorporated herein by reference for the purposes of disclosing techniques for switching nanorods.
To accomplish this, gold nanorods (length/diameter=75/25 nm) were synthesized using a wet seed-mediated method, coated with ligands (thiol terminated polystyrene, Mn=5,000 (Polymer Source, Inc.)) and suspended in toluene (˜10−4 v/v %). The suspensions were placed into an electro-optic fluid fiber component,
The active fiber section includes a fiber with five holes,
The BiSn-filled holes serve as orthogonal digital pairs of electrodes (channel 0 and channel 1). The electrical contacts for the electrodes are made by side-polishing the 5-hole fiber and gluing a copper wire to each electrode with silver-based conductive glue. A small gap (˜65 μm) from the THMM fiber end allows the pressurized (˜105 Pa) nanorod suspension to flow from the input capillary and into the central hole of the 5-hole fiber, where the nanorods interact with the applied electric fields. The construction of the electro-optic fluid fiber component is symmetric after the 5-hole fiber, allowing the nanorod suspension and transmitted light to be separated and collected. The time-averaged spectral evolution of the nanorods as a function of applied electric field was measured by coupling linearly polarized white light (halogen lamp) into the component. The output light from the component was coupled into a spectrometer (OceanOptics QE65000). In order to have stable alignment, the electric field is an alternating field at 200 kHz and typically 2 kV. The AC field prevents translation of the nanorods towards the electrodes and attachment to the inner walls. There were small deviations of the distances between the electrodes for each channel due to fluctuation in the manufacturing process. If a potential of 2 kV was applied to each channel, then the electric field in the fiber core was calculated using COMSOL Mulitphysics 5.2 to be 14.8 V/μm for channel 0 and 13.5 V/μm for channel 1.
Without an electric field applied to either channel,
The time-resolved switching of the nanorods is reported in
The “0” curve in
If the driving signal is toggled between channels 0 and 1, then
In summary, described is an electro-optic fluid fiber that combines light, nanorod suspensions and electric fields into a single component. This component provides the capability to digitally switch the plasmonic nanorods between two orthogonal aligned states using electric fields, demonstrating the removal of the thermal rotation diffusion constraint from the switching mechanism. The nanorods can align into the applied electric field direction in 110 ns, limited only by the experimental electronics. These results may lead to novel opportunities for the point-to-point delivery and modulation of light.
For signaling, it can be possible to arbitrarily modulate the properties of light (amplitude, polarization, and phase), beyond the fiber geometry; for example the switching element, comprised of the nanoparticle suspension and electrodes, can be formed by flat (analogous to a liquid crystal display pixel), curved, conformal or re-configurable surfaces.
An optical switch incorporating this technique might be incorporated into existing networks.
Au—Ag Nanorods in Nonpolar Solvents
A new preparation of Au—Ag nanorods was explored.
First, Au nanorod (NR) cores were prepared based on the methods of Park et al. . A seed solution was prepared by dissolving HAuCl4 (≥99.9%, Aldrich, 0.025 mL, 0.1 M) in an aqueous solution (10 mL, 0.1 M) of cetyltrimethylammonium bromide (CTAB, 98%, GFS Chemicals). A freshly prepared, ice-cold NaBH4 (99.99%, Aldrich) solution (0.6 mL, 0.01 M) was then added into the mixture under vigorous stirring (1 min). The seed solution was aged for 10 min before being added into the growth solution. Two growth solutions were prepared: Growth A: The growth solution was prepared by mixing HAuCl4 (0.150 mL, 0.1 M), AgNO3 (>99.99%, GFS Chemicals, 0.024 mL, 0.1 M), and CTAB (1.092 g, 2.99 mM) in 30 mL of water, followed by addition of an L-ascorbic acid (>99.0%, TCI) solution (0.159 mL, 0.1M) as a mild reducing agent. Finally, 3 mL of seed solution was added into the growth solution. The solution was kept at 25° C. for 15 min. Growth B: The solution was prepared by mixing CTAB (1.092 g, 2.99 mM), AgNO3 (2.4 mL, 0.1 M), HAuCl4 (15 mL, 0.1 M), and L-ascorbic acid solution (15.9 mL, 0.1 M). The solution was kept at 25° C. for 15 min. The growth solution B was added dropwise to growth solution A, and the Au NR as prepared were kept at 25° C. overnight. The Au NR had an absorption peak at ˜680 nm resulting from the longitudinal surface plasmon resonance. The as-prepared Au NR were placed in 50-mL centrifuge tubes (Thermo Scientific Nunc) and purified by centrifuging at 3000 rpm (1549×g), 30° C. for 1 h (Thermo Scientific Sorvall Lynx 4000 centrifuge with Fiberlite F14-14x50cy rotor). The supernatant was decanted with a serological pipette and discarded, and the precipitate was redispersed to the original volume with 18 MΩ DI water (EMD Millipore Milli-Q Advantage A10) at 30° C., followed by 30 s each of sonication and vortexing. The Au NR were centrifuged a second time at 3000 rpm, 30° C. for 1 hour. The supernatant was again decanted and discarded, and the precipitate was redispersed to the original volume with DI water, followed by 30 s each of sonication and vortexing.
The Au NR cores were coated with Ag, following a method based on that described by Park et al. . Typically, six 5-mL batches of the following type were prepared in parallel to provide a total of 30 mL. In a typical individual reaction, 184 μL of purified Au NR cores were added to 5 mL of DI water in a Fisherbrand 16×100 mm flint glass culture tube. The resulting suspension had an absorbance at 680 nm of ˜1.25 over a 1-cm path length. Then, 0.018 g of CTAB were added, raising the CTAB concentration of the Au NR suspension to ˜10 mM. The suspension was vortexed 30 s then placed in a 30° C. water bath for 15 min to encourage CTAB dissolution. The NR suspension was then vortexed until no undissolved CTAB could be seen. Next, 50 μL of 0.1 M AgNO3 were added, and the suspension was mixed with a pipette. The suspension was then aged at 25° C. for 30 min. During the first ˜5 min of aging, the suspension became turbid. After aging, 100 μL of 0.1 M L-ascorbic acid were added, and the suspension was mixed with a pipette. Then, 200 μL of 0.1 M sodium hydroxide (NaOH, Fisher Scientific, ACS grade) of pH 13 were added, and the suspension was mixed with a pipette. The addition of NaOH increased the pH of the Au NR suspension from ˜3.7 to ˜10.0, as measured by a pH probe inserted in the tube (Mettler Toledo InLab Micro-Pro-ISM probe with FiveEasy FE20 meter). Within ˜5 min, a color change toward green was observed. The suspension rested at 25° C. for at least 3 h to allow the Ag-coating reaction to complete. The resulting Ag-coated Au nanorods are termed “Au@Ag.”
The Au@Ag NR were then purified with three centrifugation cycles as described here: The 5 mL of Au@Ag NR from each of the six tubes were transferred to individual 50-mL centrifuge tubes, and DI water at 30° C. was added to bring the total liquid volume in each tube to 40 mL. The sample was centrifuged at 4000 rpm (2754×g), 30° C. for 1 h; the supernatant was decanted and discarded, and the precipitate was redispersed with DI water to 5 mL. The 5 mL from each of the six tubes were then combined in a single tube, and 10 mL of DI water were added to bring the total volume to 40 mL. This tube was then centrifuged at 4000 rpm, 30° C. for 1 h; the supernatant was decanted and discarded, and the precipitate was redispersed to 40 mL with 1.1 mM CTAB at 30° C. Finally, a third centrifugation was performed at 4000 rpm, 30° C. for 1 h; the supernatant was decanted and discarded, and the precipitate was redispersed to 30 mL with 1.1 mM CTAB.
Next, Au@Ag NR were overcoated with SiO2 following a method adapted from Wu and Tracy . The pH of the NR suspension was raised to 10 with the dropwise addition of 0.1 M NaOH. 10 mL of the suspension were dispensed in a 20-mL glass scintillation vial, which was placed in a water bath at 30° C. with magnetic stirring in the vial. A solution of 20 vol % tetraethyl orthosilicate (TEOS, 99.999%, Aldrich) in anhydrous methanol (99.8%, Sigma-Aldrich) was prepared and loaded in a 5-mL syringe fitted with a 30 G needle. In a typical reaction, a total of 125 μL of the TEOS solution was added dropwise to the Au@Ag NR over a period of 5 min using a syringe pump (Fisherbrand) operating at 1.5 mL/h. The sample was stirred magnetically for 30 min and then left without stirring in the 30° C. water bath for 20 h.
The sample was removed from the water bath and vortexed for 30 s. The suspension (containing Au@Ag NRs coated with SiO2, termed Au@Ag@SiO2) was divided between two 50-mL centrifuge tubes, 5 mL of NR to each. 35 mL of methanol (ACS grade, Fisher Chemical) was added to each tube, followed by vortexing for 30 s. The sample was then centrifuged at 1500×g (2951 rpm), 30° C. for 30 min; the supernatant was decanted and discarded, and the precipitate was redispersed with methanol to 40 mL, followed by vortexing for 30 s. A second centrifugation with the same parameters was performed, redispersing the precipitate with methanol to 5 mL, followed by vortexing for 30 s.
In order to make the Au@Ag@SiO2 NR stable in nonpolar solvents, the SiO2 surface was functionalized with octadecyltrimethoxysilane (OTMOS, 90% technical grade, Acros Organics), utilizing a method adapted from the report of Pastoriza-Santos et al. . First, 5 mL of the NR suspension in methanol were dispensed into a 2-dram (7.4-mL) glass vial and placed in a 30° C. water bath, with magnetic stirring in the vial. Then, 50 μL of 28.0-30.0% ammonium hydroxide solution (ACS grade, Oakwood Chemical) were added. Finally, 500 μL of 10 vol % OTMOS in chloroform (≥99%, Sigma-Aldrich) were added, and the solution was stirred for 24 h in the 30° C. water bath. In various embodiments, functionalization with other than octadecyltrimethoxysilane could be accomplished; for example, other alkyl-silanes might be used.
The vial was removed from the water bath and vortexed for 30 s to release any clumps of material from the sides of the vial. The solids were allowed to settle to the bottom of the vial for 15 min, after which the top 4 mL of solvent were decanted and discarded. After adding 4 mL of methanol, the sample was vortexed for 30 s and allowed to settle for 15 min. The top 4 mL of solvent were again decanted and discarded, 4 mL of methanol were added, and the sample was vortexed for 30 s then allowed to settle for 15 min. For the third time, the top 4 mL of solvent were decanted and discarded. Then, 5 mL of heptane (HPLC grade, Fisher Chemical) were added and the sample vortexed for 30 s. The sample phase-separated into two fractions: a colorless methanol phase at the bottom and a heptane phase containing the NR on top. Both phases were then extracted into a 10-mL syringe fitted with a 20 G needle and the phases allowed to separate within the syringe. The methanol phase was dispensed from the bottom of the syringe and discarded, and the heptane phase containing the NR was dispensed into a 15-mL centrifuge tube (Thermo Scientific Nunc). The sample was centrifuged at 2400×g (3453 rpm), 35° C. for 30 min (Eppendorf 5810R centrifuge). The supernatant was decanted and discarded, and the precipitate was redispersed with heptane to 1 mL. The Au@Ag@SiO2@OTMOS NRs in heptane were kept above 25° C. to avoid reversible clouding.
Materials used in these techniques can be varied. For example, nanorods of gold and/or silver are possible. In further embodiments, nanorods can be composed of another material (including metallic, semiconducting and/or partially insulating materials). Nanorods may comprise several materials and in aspects of this embodiment, the volume of the nanorod can be compositionally homogeneous or the materials can be structured in a core-shell(s) geometry with, for example, metal, semi-conductor, and/or insulator.
Nanorods can have the shape of a spherocylinder or another shape, isometric or anisometric, for example ellipsoids and asymmetric shapes. In further embodiments, a nanorod can comprise two or more sub-units that are joined together to form the overall shape of a nanorod.
A nanorod can comprise a coating, not necessarily conformal with the underlying nanorod shape. Nanorods can be coated and/or coassembled with other materials (a) intended to shift the position of their plasmon resonance and/or (b) intended to improve their function in aspects including chemical stability, reduced aggregation, and/or environmental compatibility. A coating can be optically, electrically or mechanically active, conducting, semi-conducting or insulating.
These techniques can be used with one or more populations of nanorods, each population having different attributes such as material, shape, size, and/or coatings.
Various liquids can be used singly or in combination to dissolve and/or suspend nanorods. In one embodiment, the liquid is toluene. Other liquids can be used including inorganic, organic, or aqueous liquids. In further embodiments, a gas or vacuum acts to disperse the nanorods as an aerosol. In still another embodiment, the nanorods are dispersed in a solid or gel. The solvent can be selected to have a certain refractive index in order to tailor the spectral location of the surface plasmon resonance. The solvent could include one or more additives intended to enhance the stability of the nanorod suspension and/or to modify its optical properties such as color and/or transmittance at certain wavelengths and/or bands of wavelengths. In yet further embodiments, the solvent is absent and the nanorods form a liquid crystal and/or other phase of matter.
Illumination of an optical modulator can be provided in a number of ways. The spectral characteristics of the illumination can vary considerably. In one embodiment, the light source can be a broadband, white-light source that emits over a wide wavelength range, including portions of and/or the entirety of the ultraviolet, visible, and/or infrared (near-infrared, mid-wave infrared, long-wave infrared) spectral bands. However, it is also possible to use a light source emitting in a narrow band centered around a single wavelength. The light source can consist of several sources that emit at different wavelengths or bands of wavelengths. The spectral output of the light source could be modified by passage through one or more optical filters. In various aspects, the light source is the sun and/or ambient lighting.
The geometry of the illumination may be configured as desired. In one embodiment, a device is illuminated from the back side opposite the side of intended viewing (i.e. backlit). In another, the device is illuminated from the side, with the light distributed across the back of the device. It is also possible for the device to be illuminated from the front and to contain a reflective back-plane. In a further embodiment, the device is illuminated such that the illumination is not observed by the user, and primarily scattering from the nanorods is observed (i.e. the device operates in a darkfield scattering configuration). One or more light sources might be used, possibly including individual light sources for each pixel of the device. The light source could operate continually or vary in intensity over time, including periodic variations and/or variations representing a data signal. The light source may have any polarization state, including linear, circular, and elliptical, and the polarization state may vary over time, potentially representing a signal.
A device can be configured for observation from the front, back, and/or any oblique angle.
An optical modulator incorporates one or more pixels, each incorporating one or more nanorods. Multiple pixels can be stacked in a layered structure such that a single ray of light passes through more than one pixel. Multiple pixels can be arrayed in a planar manner, in one or more different configurations include periodic, aperiodic, and quasiperiodic arrays. Pixels may have the same size or a variety of sizes within the same device. Each pixel may comprise several sub-pixels, each of which is designed to interact with a different portion of the electromagnetic spectrum. The subpixels may constitute an additive and/or subtractive color mixing scheme such as red/green/blue (RGB) and/or cyan/magenta/yellow/black (CMYK). Each pixel can comprise one or more than one pair of electrodes (such as orthogonal pairs of electrodes) and/or other schemes for generating electric field beyond the use of parallel electrode pairs. The pixels can be integrated into one or more optical fibers. A pixel shape can be a rectangle and/or any other shape. For example, the pixel is shaped so as to constitute an entire image, character(s) of text, or other representation(s). The pixel can be shaped so that by combination with other pixels, an image, character(s) of text, or other representation(s) are perceived. The pixels can be arranged in 3-dimensional arrays so as to constitute “volume elements” or “voxels” of a volumetric display.
An optical modulator can operate using various contrast mechanisms. The device may utilize spatial, and/or temporal contrast in luminance, chromaticity, and/or polarization of pixels. The device may operate with pixels in an intermediate state of alignment (i.e. between isotropic and fully aligned states).
An optical modulator optionally includes a support substrate for the one or more pixels. It may be rigid or flexible, planar, curved, and/or otherwise textured. The substrate is optically configured to be conformal with another underlying object. The substrate can be reconfigurable, an optical fiber, a fabric, a biological tissue, or a combination of these.
Nanorods in an optical modulator can be aligned using electric fields or other types of fields, including electric, magnetic, optical, pressure, temperature, concentration, and/or mechanical stress/strain, or a combination thereof.
An optical modulator might be driven in various ways. In one embodiment, it is driven by alternating current (AC). The frequency of the AC driving voltage may be 60 Hz, 5 kHz and/or any other frequency. The AC driving voltage may be modulated with other waveforms, including those encoding data. The magnitude of the AC driving voltage may be any value appropriate for achieving a desired degree of nanorod alignment. The driving source may employ any manner of frequency- and/or amplitude-modulation (FM/AM) scheme.
A pixel in an optical modulator may be controlled independently or as part of an integrated control system for multiple pixels.
An optical modulator may be implemented in combination with other technologies that also modulate properties of light, including liquid-crystal-based light modulators and/or displays. In other embodiments, the modulator has a modulatory effect on light solely via action of nanorods.
A device may be used to transmit, receive, or otherwise modulate data streams encoded in the light that interacts with the pixels such as for visible light communication (VLC). These data streams may be encoded in one or more keying systems [see ref. 6], including color intensity modulation (CIM), color-shift keying (CSK), and metameric modulation (MM).
In one prophetic example, a signal can be embedded in visible light (such as visible light serving as illumination or visible light that serves as a display of a still or moving image) by modulating a property of the light (for example, brightness, hue, etc.) with an optical modulation rate higher than perceived by humans, for example faster than 60 Hz, faster than 120 Hz, faster than 500 Hz, and so forth. The signal could be interpreted by an apparatus configured to detect the modulated light and spaced some distance apart from the source thereof.
By controlling the alignment of the nanorods, a device can modulate the real and imaginary optical phase shifts through the optical element; thereby controlling the absorption, scattering, refraction, reflection, transmission, optical phase, polarization (including linear, circular, and elliptical), direction of propagation, spectral composition, and/or combinations thereof.
Individual pixels and/or the device may be encapsulated and/or otherwise packaged so as to impart improved attributes such as durability, longevity, user safety, regulatory compliance, and/or end-of-life management.
Switching elements can be simply spliced into current optical fiber networks and used to remotely sense and signal (via electric fields). For example they can used as an ultrafast (GHz) telecommunications switch or to sense large electric fields (such as for high voltage transformers).
All documents mentioned herein are hereby incorporated by reference for the purpose of disclosing and describing the particular materials and methodologies for which the document was cited.
Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the spirit and scope of the invention. Terminology used herein should not be construed as being “means-plus-function” language unless the term “means” is expressly used in association therewith.
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