WO2008003004A2

WO2008003004A2 - Electro-optic reflective beam-steering or focussing assembly, and solar energy conversion system

Info

Publication number: WO2008003004A2
Application number: PCT/US2007/072289
Authority: WO
Inventors: Dwight P. Duston; Daniel T. Colbert; Allan Carmichael
Original assignee: Solbeam, Inc.
Priority date: 2006-06-27
Filing date: 2007-06-27
Publication date: 2008-01-03
Also published as: WO2008003004A3

Abstract

Techniques and apparatus for steering and/or focusing light rays. A. system configurable to steer or focus or both steer and focus light rays includes an electro-optic steering assembly including a substrate (201) having an optically reflective surface (202) and an electro-optic layer in optical communication with the substrate (201). The electro-optic layer includes- a first electrode layer (205) having separately addressable electrode components, a second electrode layer (203) and an electro-optic material (206) positioned between the first and second electrode layers. Voltages applied to the separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material. The refractive index gradient can be controlled, such that light rays (209) impinging on the electro -optic steering assembly and reflecting from the optically reflective surface (202) can be σontrollably steered in a direction, focused to a point (210) in space, or steered and focused (212). An application includes focusing sunlight onto a photovoltaic device (211).

Description

ELECTRO-OPTIC REFLECTIVE ASSEMBLY

TECHNICAL FIELD [0001] This invention relates to dynamically steering and focusing light rays.

BACKGROUND

[0002] Planar and curved reflective optical components such as mirrors are used in a wide variety of optical systems to both steer and focus optical radiation and, in some cases, are preferred over refractive optical components such as prisms and lenses. Optical components that serve to reflect light have advantages over their dispersive counterparts, as both the steering angle and focal length of such components are non-dispersive, i.e., they are independent of optical wavelength. Such reflective optical components may be used in optical systems for astronomy and free-space optical communication, for example.

[0003] Some materials can interact with light to cause it to "bend" or refract as it passes through the medium. The formation of a rainbow is a classic example of refraction, where individual droplets of water refract the sun's light into its component spectrum of colors (i.e., wavelengths). In some materials, the index of refraction, that is, the extent to which light of a given wavelength will undergo a deviation in its path upon passing through the medium, can be controlled by an externally-applied electric field and are generally referred to as electro-optic materials. Such a behavior is exemplified by the Pockels effect, where birefringence can be induced in an optical medium by a constant or varying electric field.

[0004] The sun is a limitless source of terrestrial energy that, if it were able to be captured with sufficient efficiency, could provide significant relief to our dependence on fossil fuels and other less environmentally-friendly energy sources. In addition, the sun can provide a sustainable energy source for space-based, or interplanetary endeavors where, for example, it may be infeasible to burn fuels, or where battery power may not provide the required longevity or power needs. Photovoltaics, or "solar cells" are designed to capture light energy and transform it into useable electricity, either by utilizing a solar-generated electrical current directly, or by storing electrical potential via a battery or system of batteries. Photovoltaics can be constructed of materials that absorb a portion of the solar spectrum; absorption of sufficiently-energetic photons by the photovoltaic material can free electrons within the material, thereby generating an electric current. In some cases, manufacturing costs outweigh the return in savings realized by using photo vo ltaics as an energy source.

SUMMARY

[0005] The invention relates to steering and focusing light rays. In general, in one aspect, the invention features a system for the steering light. The system includes an electro-optic steering assembly including a substrate and an electro-optic layer. The substrate has an optically reflective surface. The electro-optic layer is in optical communication with the substrate and includes a first electrode layer having multiple separately addressable electrode components, a second electrode layer and an electro- optic material positioned between the first and second electrode layers. Voltages applied to the f separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material, such that light rays impinging on the electro-optic steering assembly and reflecting from the optically reflective surface are controllably steered in a direction.

[0006] Implementations of the invention can include one or more of the following features. The optically reflective surface can be a curved or a planar surface. The system can further include a second electro-optic layer positioned in optical communication with the electro-optic layer, wherein the first electrode layer included in each electro-optic layer includes rectangular electrode components arranged parallel to one another and wherein the rectangular electrode components of the electro-optic layer are arranged perpendicular to the rectangular electrode components of the second electro-optic layer. At least one of the first electrode layer or the second electrode layer can include a transparent electrode. The electrode components can be rectangular electrode components arranged adjacent and substantially parallel one another. The electrode components can be arranged in a two-dimensional array.

[0007] The light rays can be steered toward a target location and the system can further include a photovoltaic device provided at the target location. The photovoltaic device can be a solar cell including a semiconductor material that absorbs light rays. In another example, a solar thermal system can be provided at the target location. The electro-optic material can be a nematic liquid crystal. The electro-optic material can be selected from a group consisting of: cholesteric liquid crystal, smectic liquid crystal, polymer dispersed liquid crystal and polymer stabilized liquid crystal. The electro-optic material can be a solid state electro-optic material. For example, the solid state electro- optic material can be selected from a group consisting of: lithium niobate (LiNbO₃) and lithium tantalite (LiTaO₃).

[0008] In general, in another aspect, the invention features a system for focusing light including an electro-optic assembly. The electro-optic assembly includes a substrate having an optically reflective surface, and electro-optic layer in optical communication with the substrate. The electro-optic layer includes a first electrode layer having multiple separately addressable electrode components, a second electrode layer and an electro- optic material positioned between the first and second electrode layers. Voltages applied to the separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material, such that light rays impinging on the electro-optic assembly and reflecting off the optically reflective surface are controllably focused toward a point in space.

[0009] Implementations of the invention can include one or more of the following features. The optically reflective surface can be a curved or planar surface. At least one of the first or second electrode layers can include a transparent electrode. The electrode components can be arranged in a two dimensional array. In another example, the electrode components are concentric ring electrode components. A photovoltaic device and/or solar thermal system can be provided at the point in space to which the light rays are focused. Examples of the electro-optic material include a: nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, polymer dispersed liquid crystal, polymer stabilized liquid crystal and a solid state electro-optic material (e.g. , lithium niobate (LiNbO₃) or lithium tantalite (LiTaO₃)).

[0010] In general, in another aspect, the invention features an electro-optic assembly including a first substrate including an optically reflective surface, a second substrate including a substantially smooth exterior surface and an interior surface providing a surface relief optical structure. A electro-optic layer is positioned between the first and second substrates, the electro-optic layer including a first electrode, a second electrode and an electro-optic material positioned therebetween. The first electrode is positioned between the electro-optic layer and the first substrate, the second electrode is positioned between the interior surface of the second substrate between the electro-optic material, and the electro-optic material conforms to the surface relief optical structure of the second substrate.

[0011] Implementations of the invention can include one or more of the following features. The surface relief optical structure can provide an optically refractive pattern providing a degree of optical steering of light rays impinging on the exterior surface of the second substrate. An index of refraction of the electro-optic material can be adjustably controllable by applying a voltage to at least one of the first or second electrodes. The surface relief optical structure can include a series of prisms. [0012] In general, in another aspect, the invention features an electro-optic system. The system includes a substrate having an optically reflective surface. A first electro-optic layer is in optical communication with the substrate. The electro-optic layer includes a first electrode layer including multiple separately addressable electrode components, a second electrode layer and an electro-optic material positioned between the first and second electrode layers. Voltages applied to the multiple separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material such that light rays impinging on the electro- optic steering assembly and reflecting from the optically reflective surface can be selectively: (a) steered in a direction; (b) focused to a point in space; or (c) both steered in a direction and focused to a point in space.

[0013] Implementations of the invention can include one or more of the following features. The optically reflective surface can be a curved or a planar surface. The multiple electrode components can be arranged in a two-dimensional array. In one example the components are square shaped electrode components. In another example, the components are triangular shaped electrode components.

[0014] The system can further include a second electro-optic layer in optical communication with the first electro-optic layer. The second electro-optic layer includes a third electrode layer having multiple separately addressable electrode components, a fourth electrode layer and an electro-optic material positioned between the third and fourth electrode layers. The refractive index gradient of the first electro-optic layer is controlled to provide controllable steering of light rays impinging on the electro-optic system and reflecting from the optically reflective surface, and a refractive index gradient in the second electro-optic layer is controlled to provide controllable focusing of the light rays to a point in space.

[0015] In another implementation, the second electro-optic layer includes a second substrate including a substantially smooth exterior surface and an interior surface providing a surface relief optical structure. A third electrode layer is positioned on the interior surface of the second substrate. A fourth electrode layer is included and an electro-optic material is positioned between the third and fourth electrode layers and conforms to the surface relief optical structure of the second substrate. One of the electro-optic layers is configured to provide steering of light rays impinging on the electro-optic system and the other electro-optic layer is configured to provide focusing of light rays impinging on the electro-optic system. In one example, the second electro- optic layer is configured to provide steering of light rays, and an index of refraction of the electro-optic material is adjustably controllable by applying a voltage to at least one of the third or fourth electrodes, such that a total amount of optical wave steering is provided by a cumulative effect of light rays propagating through the surface relief optical structure and the electro-optic material. The surface relief optical structure can form a series of refractive prisms.

[0016] In general, in another aspect, the invention features a solar energy collection system. The system includes a substrate including an optically reflective surface, an electro-optic assembly and a photovoltaic device. The substrate includes an optically reflective surface. The electro-optic assembly is in optical communication with the substrate and includes a first electrode layer having separately addressable electrode components, a second electrode layer and an electro-optic material positioned between the first and second electrode layers. Voltages applied to the separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material, such that light rays impinging on the electro-optic layer and reflecting off the optically reflective surface are controllably focused toward a target location. The photovoltaic device is positioned at the target location. [0017] Implementations of the invention can include one or more of the following features. The optically reflective surface can be a curved or a planar surface. The electrode components can be configured as concentric ring electrode components. In another example, the electrode components are arranged in a two-dimensional array. [0018] In general, in another aspect, the invention features a method including receiving light rays onto a surface of an electro-optic reflective assembly including a substrate and an electro-optic layer. The substrate has an optically reflective surface. The electro-optic assembly is in optical communication with the substrate and includes a first electrode layer having separately addressable electrode components, a second electrode layer, and an electro-optic material positioned between the first and second electrode layers. The method further includes selectively applying a voltages to the electrode components to selectively adjust a refractive index of the electro-optic material, such that after the light rays exit the electro-optic layer and reflect off of the optically reflective surface, the light rays are directed towards a target location in space. [0019] In one implementation, the light rays are solar rays and the method further includes providing a photovoltaic device at the target location. Adjusting the refractive index can include adjusting the refractive index as the sun tracks across the sky, such that the solar rays are directed toward the photovoltaic device when the sun is at various positions in the sky throughout a day.

[0020] Implementations of the invention can realize one or more of the following advantages. The systems disclosed can provide a low-cost reflective optic assembly having the ability to dynamically steer, focus and correct for wavefront aberrations of incident optical radiation, by integrating an electro-optic layer (which can be dynamic and substantially transparent, in some implementations) with the reflective surface of an optic. The ability to change the refractive index of the electro-optic material included in the electro-optic layer allows the electro-optic material to impose phase changes on incident optical radiation. After the optical radiation is reflected from the reflective surface, a desired optical effect can be achieved that would be difficult, expensive or perhaps not possible to achieve with a conventional static reflective optic. Additionally, optical radiation impinging on the optic at variable incidence angles can be focused to a target location by controlling the index of refraction of the electro-optic material, rather than repositioning the optic assembly itself, or components therein. Light ray steering and/or focusing can be achieved in an apparatus that does not require moving parts. Eliminating moving parts can reduce maintenance costs, reduce the failure rate and not require the same bulk and weight of a system including.

[0021] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

[0022] FIGS. IA-D illustrate light being focused by a reflective surface.

[0023] FIG. 2A is an exploded cross-sectional view of a dynamic electro-optic reflective optic (DERO), according to one embodiment.

[0024] FIG. 2B is a cross-sectional view of an example electro-optic reflective assembly. [0025] FIG. 2C is a schematic representation of wave propagation through an example electro-optic reflective assembly.

[0026] FIG. 3 illustrates another embodiment of a DERO.

[0027] FIG. 4 is one embodiment of a DERO including electrodes patterned in concentric rings.

[0028] FIG. 5 A is one embodiment of a DERO including electrodes patterned in concentric rings.

[0029] FIG. 5B is a side-view of the DERO illustrated in FIG. 5 A.

[0030] FIG. 6 is one embodiment of a DERO including electrodes patterned in linear strips.

[0031] FIG. 7 is one embodiment of a DERO including electrodes patterned in squares.

[0032] FIG. 8 is one embodiment of a DERO including electrodes patterned in a honeycomb arrangement.

[0033] FIG. 9 is one embodiment of a DERO including patterned triangular shaped electrodes.

[0034] FIG. 10 is another embodiment of a DERO.

[0035] FIG. 11 is another embodiment of a DERO.

[0036] FIG. 12 is another embodiment of a DERO.

[0037] FIGS. 13A-13B show cross-sectional view of other embodiments of

DEROs.

[0038] FIG. 14 is a solar energy collection system including a DERO, according to one embodiment.

[0039] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0040] Optical elements that focus light rays find utility in many applications.

The degree to which an optical element, such as a lens or a curved mirror, can focus light to a point source without chromatic and/or spatial aberration can be a function of manufacturing ability, material choice, and production cost. The surfaces of high-quality optical focusing elements are typically polished to as smooth a surface as possible so that the light rays impinging on the element experience a substantially homogeneous surface, thus reducing the chance of developing aberrations in the focused far- field. It can become increasingly difficult to control focusing aberrations and the focus direction when a light source moves away from a principal axis of a focusing optic. [0041] FIG. IA illustrates a cross-sectional view of light being focused by a reflective surface onto a target. In this example, a reflective optic 102 includes a spherical reflective surface that is rotationally symmetric about an axis 109 and which acts to focus incident optical radiation toward a target 103. Light rays 104 propagating parallel and near to the optical axis 107 are brought to a focal point 104a on the target 103, while light rays 105 more distant from the optical axis 109 focus away from the target 103, e.g., at focal point 105a. This effect can be caused by spherical aberration in the surface characteristics of the reflective optic 102, but can be remedied by using an aspheric optic 106 having a reflective surface as shown in FIG. IB. Aspheric reflective optics can reflect parallel light rays both near to the optical axis 104 as well as light rays distant from the optical axis 109 to focus on the target 103.

[0042] The aspheric optic 106 shown in FIG. IB may not perform ideally in all situations with respect to focusing light to a target from a distance. FIG. 1C illustrates a situation where light rays 106b are incident at an angle θ away from normal incidence. In this example, normal incidence is considered to be ninety degrees from the plane 106a perpendicular to the optical axis 109 of the aspheric optic 106. In this case all light rays 106b are focused to a single point 103 a, but not on the target 103. To bring the light rays 106b to focus on the target 103, the aspheric optic 106 and the target 103 would require a rotation of the aspheric optic 106 in the direction indicated by the arrows 103b by an angle θ, which, operationally, can add both expense and complexity if that is the result so desired. Furthermore, referring to FIG. ID, if the optical wavefront 107 approaching the aspheric optic 106 is aberrated (in this example, shown as deviations from a perfect plane wave 108) the associated light rays 107a may not be as tightly focused on the target 103, which can be a deleterious effect depending on the application.

[0043] FIG. 2A shows an exploded cross-sectional view of an example dynamic electro-optic reflective optic (DERO) 200. The DERO 200 includes a mirror substrate 201 having a substantially concave reflective optical layer 202. The mirror substrate 201 can be formed of a material suitable for the deposition of a reflective coating forming the reflective optical layer 202, including fused silica, glass, and the like. The reflective optical layer 202 can be formed from a material chosen for its light reflecting characteristics with regard to the intended application of the DERO 200. For example, if the DERO 200 will be used in an application where broad-band visible light will be focused, a suitable reflective optical layer 202 may include a layer of aluminum, since this material is relatively efficient at reflecting light in the 300-1000 nanometer wavelength range. Alternatively, if the goal of the DERO 200 system is to focus infra-red radiation, a material such as gold may be used as its reflectance is efficient in the 600 nanometer to 10 micron wavelength range. So-called plano-concave mirrors in a variety of shapes, sizes, reflective coatings, and surfaces are readily available commercially. [0044] The DERO 200 further includes an electro-optic layer 207 positioned above the mirror substrate 201. In the implementation shown, the electro-optic layer 207 includes a transparent reference electrode 203, an electro-optic material 206, a patterned electrode 205, and a transparent substrate 204. Voltages applied to the electrodes 203 and

205 can be adjusted to modify certain optical properties of the electro-optic material 206 sandwiched therebetween, and thus control light propagation through the electro-optic material 206.

[0045] The transparent reference electrode 203 is shown on the surface of the reflective optical layer 202 in FIG. 2A; however, the reference electrode 203 can be omitted if the reflective optical layer 202 includes a material that is both reflective and conductive, such as aluminum. The optically transparent substrate 204 is shaped with a curvature that is substantially matched to the curvature of the mirror substrate 201. The second transparent electrode 205 is applied to the surface 204a of substrate 204 that faces the reflective optical layer 202 of mirror substrate 201.

[0046] The electrode 205 as illustrated is patterned, and the nature of the patterning can affect the functionality of the DERO 200, as discussed below. As illustrated in FIG. 2A, the transparent electrode 203 exists on the reflective optical layer 202 of the mirror substrate 201, and the patterned transparent electrode 205 is shown on the surface of the optically transparent substrate 204. However, an opposite configuration can yield the same functionality, wherein the positions of the transparent electrode 203 and the patterned transparent electrode 205 are switched.

[0047] The electro-optic material 206 is deposited between the transparent electrode 203 and the patterned transparent electrode 205. The electro-optic material 206 can be formed from, for example, nematic liquid crystal, and the thickness of said layer

206 can be controlled by maintaining a spacing element (not shown) between the surface of the substrate 204 and the mirror substrate 201. Such spacing elements are well known in the liquid crystal display industry and include, for example, glass spacer beads and patterned photoresist stand-offs.

[0048] Nematic liquid crystalline fluids can be preferred materials for the electro- optic material 206, as they are commercially available and typically require low operating voltages (less than 5 V), although other electro-optic materials may be used, including cholesteric liquid crystals, smectic liquid crystals, polymer dispersed liquid crystals, polymer stabilized liquid crystals and solid state electro-optic materials such as lithium niobate (LiNbO₃) or lithium tantalite (LiTaO₃). The use of some liquid crystalline electro-optic materials (e.g., nematic liquid crystals) may require the presence of alignment layers; these are typically thin layers of a polyimide processed from solution and deposited onto surfaces that will be directly adjacent to the liquid crystal, and which are mechanically brushed in a linear direction to establish a single alignment domain for the liquid crystal.

[0049] Many electro-optic materials (including nematic liquid crystals) exhibit an anisotropy of their optical properties, the most important of which is an anisotropy in refractive index (commonly referred to as birefringence). The effects of birefringence impact both the static and dynamic refractive indices of the electro-optic material and in the case of nematic liquid crystalline materials, only optical radiation linearly polarized along the brushing direction of the alignment layer experiences an electro-optic change in the refractive index. If unpolarized light rays are impingement on the DERO, a second electro-optic layer can be placed in series with the first electro-optic layer, where the brushing directions for the two layers of liquid crystal included therein are orthogonal. [0050] Referring again to FIG. 2A, the DERO 200 can include multiple, individual electrodes 205 on a first substrate 204 and a reference electrode (e.g., a ground electrode) 203 on a second substrate 202. Applying voltages to the electrodes 205 generates an electric field in the electro-optic material 206, causing polar molecules therein to rotate in the direction of the applied electric field. In some implementations, the reference electrode 203 is electrical ground. By controlling the voltages to the individual electrodes 205, a gradient in the refractive index ("index gradient") of the electro-optic material 206 can be created. The index gradient is controlled in accordance with the angle of incident of light rays. In one implementation, the light rays are solar rays and the angle of incidence changes throughout the day with the position of the sun relative to the surface of substrate 204. As the sun moves, i.e., the incidence angle changes, the index gradient can be controllably modified, such that the incident solar rays are steered from their angle of incidence so as to focus to a selected target location after being reflected from the reflective surface 202.

[0051] FIG. 2B illustrates the operation of a DERO 200 according to one embodiment. The light rays 209 are shown incident at an angle θ to the principle axis 220 of the optic. A conventional curved mirror (i.e., without an electro-optic layer 207) will focus the incident light rays to a point off-axis from the principle axis 220 of the optic, indicated at point 210. The same may be true if the electro-optic layer 207 is present, but without voltages applied to the patterned transparent electrode 205. Light rays 209 are focused to a point 212 (which, in FIG. 2B is the location of a target 211, such as a photovoltaic device) indicated by the dashed lines 209b when the DERO is operational. In the operational state, voltages applied to the patterned transparent electrode 205 create a refractive index gradient within the electro-optic layer 206 that bends the incident light an angle p (i.e., between light rays 209a and 209b) such that the light rays 209 impinge on the selected target location 211. The magnitude of angle p can be predetermined by controlling the refractive index gradient, which is controlled by controlling the voltage gradient applied to the transparent patterned electrode 205. [0052] FIG. 2C illustrates the operation of the example DERO 200 in terms of a plane wave propagating through the layers of electro-optic layer 207, which, for simplicity, have been schematically concatenated into layer 255, and the mirror substrate 201 and reflective surface 202 have been schematically concatenated into element 260. In FIG. 2C, a refractive index gradient along the lateral direction (denoted by arrow 265) has been created in the electro-optic material that varies from a low value on the left to a high value on the right, as indicated. An incident plane wave 1 is shown traveling in the direction indicated by arrow 250. In free space the wave 1 propagates as a plane wave to a second position 2. Once the wave enters the electro-optic layer 206, the left side of the wave moves at a higher velocity than the right side, due to the refractive index gradient. The longer the wave stays in the material (wavefronts 3, 4, 5) the more the right side of the propagating wave is retarded with respect to the left. The wavefront is reflected off the mirror (wavefront 6 and 7) and continues to travel through the electro-optic material 206 (wavefronts 7 and 8). The wavefront exits the electro-optic material (wavefronts 9, 10, 11) and propagates in free space, but at an angle with respect to the original, incident plane wave 1, as denoted by arrow 260. [0053] FIGS. 2B and 2C illustrate how controlling the refractive index of the electro-optic layer included in a DERO allows for steering of impingent light rays, such that exiting light rays can be selectively focused to a target location. [0054] FIG. 3 illustrates an implementation of a DERO 300 that includes multiple electro-optic layers 307a, 307b, i.e., an additional transparent substrate 304, electrode layers 303 and 305, and a second electro-optic material 306 are included as compared to the DERO 200 shown in FIG. 2A. This implementation of the DERO 300 can be particularly useful for steering linearly polarized light, as each layer 307a and 307b can be configured to control one of two orthogonal polarization components of the propagating light. The electrode layers 205 and 305 can be of different configurations so as to make the optic functional in this regard. Double-layered DEROs 300 can also be used to steer unpolarized light in one direction, where the electro-optic material (e.g., a liquid crystal layer) alignment is orthogonal between the two layers. [0055] The configuration of the patterned electrodes either alone, as in FIG 2

(patterned electrode 205), or in tandem, as in FIG. 3 (patterned electrodes 205 and 305), determines the electro-optic functionality of the DERO.

[0056] FIG. 4 is a top-view illustration of one implementation of the DERO 200 shown in FIG. 2. In this implementation, the patterned electrode 205 is patterned in concentric rings to alter the light focusing properties of the DERO 200. Each ring can be an independently addressable electrode, i.e., the voltage can be controlled to each ring independent of the voltage applied to neighboring rings. The concentric ring-patterned electrode 205 can be patterned such that the width of the rings varies as the square root of the ring's radius to generate a quadratic phase profile (similar to that of an aspheric lens) in the layer of electro-optic material 206.

[0057] Light impinging upon the DERO 400 can be substantially focused and defocused by creating the proper phase profile in the electro-optic material 206. For example, referring to FIG. 5 A, a top view illustration of another example of patterning of the patterned electrode 205 is shown. If an arbitrary, but rotationally symmetric phase profile is desired, then the concentric ring-patterned electrode 205 can include rings of substantially equal width as shown in FIG. 5A. Again, each ring can be an independently addressable electrode, i.e., the voltage can be controlled to each ring independent of the voltage applied to neighboring rings. In either case, the electrodes are patterned on a component of the DERO 200 that may include either the curved mirror substrate 202 or the transparent substrate 204 (as in this example). [0058] Referring to FIG. 5B, such an electrode structure may be used to alter the focusing characteristics of the DERO 200, or to correct for rotationally symmetric optical aberrations. FIG. 5B is a cross-sectional side-view of the DERO embodiment of FIG. 5A, and, for clarity only shows a mirror substrate 202 (to provide a general form of a curved mirror) and the electro-optic layer 206 disposed thereon. FIG. 5A illustrates regions in the electro-optic layer 206a-e that indicate phase boundaries created by the concentric ring electrodes 205 (not shown), and impinging light rays 501. The DERO 200 can alter the focus of the light rays 501 by controlling the refractive index grating of the regions 206a-e. For example, the solid light reflected light rays 501 focus to a point 505 because the refractive index of the regions within the electro-optic layer in this example increase in the order 206e, 206d, 206c, 206b, 206a. The light rays 501 are bent at a greater angle at region 206a than for the region 206e by virtue of the electric potential applied to the outer electrode compared with the inner electrode.

[0059] The DERO may shift the focal point of the focused light rays 501 to a different point 510, which, in this example, is further from the DERO device itself. The refractive index of the regions 206a-e still increase in the same order as that for the previous example where the light rays 501 focus to point 505, but in this case the magnitude of the refractive index gradient may be less. In other words, as shown by the dashed reflected light rays 501, the angle α at which light rays are bent at region 206a is less than its neighbor region 206b, and, for a Gaussian beam profile absent of distortion, this progression of smaller and smaller angles continues toward the center of the DERO reflective surface.

[0060] In situations where it is desirable to de focus the light rays 501, the refractive index gradient profile of the electro-optic layer 206 can be reversed, such that the refractive index increases in the order 206a, 206b, 206c, 206d, 206e, as an example. [0061] Referring to FIG. 6, in one the DERO 200 includes a patterned electrode

205 that is patterned as elongated rectangles as illustrated. This implementation may be desirable to steer optical radiation. In such a configuration of the patterned electrode 205, the rectangular portions of the electrode 205 generate a phase profile in the electro-optic layer, similar to that of a prism that acts to bend or steer incident light rays. Each rectangular portion of the electrode 205 is uniquely addressable and able to provide a voltage independent of a neighboring rectangular portion. A voltage gradient can therefore be created across the DERO 200 in, for example, the direction indicated by the arrow 603. For example, the voltages applied to rectangular electrode portions 601a-e may decrease in the order: 2.5V, 2.0V, 1.5V, 1.0V, 0.5V respectively (each portion of the electrode can have an applied voltage that increases (or decreases) in the direction of the voltage gradient).

[0062] The voltage gradient applied to the patterned electrode 205 creates a controllable gradient in the index of refraction of the electro-optic material 206. Referring again to the direction of the arrow depicting the increasing voltage gradient, a gradient in the index of refraction of the electro-optic material 206 will be created in substantially the same direction for the DERO 600. Light that is incident to the DERO 200 parallel to the direction of the arrow 603 in this example, (i.e., perpendicular to the gradient lines of the index of refraction gradient) can be steered by adjusting the voltages of each rectangular portion of the electrode 205. In effect, the refractive index grating is the analog of an optical prism that bends light according to an index of refraction that changes from the base of the prism to the apex.

[0063] In certain DERO embodiments, light can be steered in two dimensions, or focused, or both, utilizing a single layer of electrodes patterned and configured so as to allow control of the phase of impinging light waves. In these embodiments, individually- addressable (i.e., voltage-controllable) electrode components generate electric fields, or an electric field gradient, in a plane of the electro-optic material that is substantially equal to a superposition of two, orthogonally-aligned electrode layers. [0064] Such an embodiment is shown in FIG. 7, where electrodes patterned as squares make up a two-dimensional surface where each electrode is individually addressable. Because each electrode is controllable with respect to the electric potential applied thereto, the two-dimensional surface of electrodes can impart practically any configuration of phase pattern on the electro-optic layer. A two-dimensional array of electrodes (e.g., electrode 701) may also be used to correct for combinations of aberrations that may arise from sources such as other optical components, or propagation of light through a turbulent medium. While square-shaped electrodes (or pixels) are shown in FIG. 7, other shapes may be used such hexagons 801 (FIG. 8) or triangles 901 (FIG. 9). The embodiments of FIGS. 7-9 may also allow steering of light rays by controlling the voltage applied to each electrode, e.g., electrodes 701a-c, thereby generating an electric field gradient in two dimensions.

[0065] Referring to FIG. 10, one implementation of a DERO 1000 is shown that incorporates a prism structure on a transparent substrate. The DERO 1000 includes a curved mirror substrate 1001 with a reflective surface 1002 and a transparent electrode 1003 deposited thereon, similar to the DERO 200 illustrated in FIG. 2. As was mentioned previously, the transparent electrode 1003 can be omitted if the reflective surface 1002 comprises an electrically-conductive reflecting material such as aluminum or gold. The electro-optic elements 1007 of the DERO 1000 include the transparent electrode 1003 (if necessary), an electro-optic material 1006, a transparent electrode 1005, and a transparent substrate 1004.

[0066] The transparent substrate 1004 has an overall curvature that matches the curvature of the mirror substrate 1001 and is substantially smooth on the side 1004a that faces away from the mirror substrate 1001. The opposing side 1004b has a surface relief optical structure 1004c that comprises an array of prisms, onto which the transparent electrode 1005 is applied to the surface relief structure 1004c of substrate 1004. The mirror and substrate are assembled into a DERO using the aforementioned techniques and materials outlined for the patterned electrode device. In operation, the electro-optic material 1006 that fills the surface relief structure 1004c will undergo a change in refractive index upon application of a voltage by transparent electrodes 1003 and 1005, causing the angle through which the beam is steered to change. [0067] As with the patterned electrode approach, electro-optic devices (i.e., the electro-optic elements 1007) may be stacked in series to address polarization-sensitive electro-optic materials or to provide additional functionality. An example of such a DERO device 1100 is shown in FIG. 11. Similar to the DEROs described above, in this implementation the DERO 1100 includes a mirror substrate 1101 with a reflective surface 1102. The elements of the first electro-optic element layer 1107a include an un-patterned transparent electrode 1103 a, an electro-optic material 1106a, a second transparent electrode 1105 a, and a transparent substrate 1104a comprising a surface relief optical structure 1004c as described in FIG. 10.

[0068] A second layer of electro-optic elements 1107b is applied to the top of the first layer of electro-optic elements 1107a, having the same elements, and indicated by 1103b, 1106b, 1105b, and 1104b in FIG. 11. While the physical characteristics of each component in the second layer of electro-optic elements 1107b may be similar, their configuration with respect to one another may be different. For example, the orientation of electrodes 1105a and 1105b, or the prismatic dispersion direction for the substrates 1104a and 1104b may be aligned orthogonally. By configuring a DERO 1100 in this manner and controlling the properties of the electro-optic layers 1107a and 1107b distinctly, light rays impinging on the DERO 1100 can be steered in two directions because each electro-optic layer 1107a and 1107b contributes to one half of a two- dimensional steering vector.

[0069] In other embodiments, the physical characteristics of the electro-optic layers 1107a and 1107b can be different from one another. For example the electro-optic material 1106a may differ from the electro-optic material 1106b; or, the thicknesses of the two electro-optic layers 1106a and 1106b can differ. In another example, the surface relief optical structure 1004c in substrate 1104a may be different than that for 1104b, providing more or less prismatic power for steering light in one direction over the other, depending on the application and configuration.

[0070] In yet another embodiment, both the physical characteristics and the relative configuration of the electro-optic layers 1107a and 1107b are different from one another, providing further adaptability for changing light conditions or steering/focusing configurations.

[0071] The DERO embodiments of FIG. 2 and FIG. 10 each have their own innate light-steering and/or focusing characteristics and advantages. For some applications it may be beneficial or advantageous to combine the operational characteristics of these devices, which results in the example hybrid DERO device 1200 shown in FIG. 12. In this implementation, the hybrid DERO 1200 is supported by a mirror substrate 1201 having a reflective surface 1202, the characteristics of which have been previously described. The electro-optic layers of the hybrid DERO 1200 include the electro-optic layer 1007 described with respect to FIG. 10, and the electro-optic layer 207 described with respect to FIG. 2.

[0072] In certain other embodiments where a surface relief optical structure is used it may be useful to pattern one of the transparent electrodes to spatially alter the applied potentials. As shown in FIGS. 10, 11, and 12, the transparent electrodes apply a voltage across a layer of electro-optic material with variable thickness, which may result in non-uniform electric fields within the material. If one of the transparent electrodes is patterned, then the potentials may be varied such that the electric fields within the electro- optic material are more uniform. Placement of such patterned electrodes are shown in FIGS. 13A and 13B, where, for example, patterned electrode 1402 is placed onto either the reflective surface of the mirror 202 or the outer surface of transparent substrate 1004, respectively. DEROs 1300 and 1301 shown in FIGS. 13A and 13B, respectively, are also capable of being incorporated into stacked and hybrid systems as previously described for

FIG. 11 and FIG. 12, respectively. [0073] DERO devices such as those discussed above can be prepared in the following exemplary manner. A thin- film electrode is applied to a solid substrate first (if necessary), patterned (if needed), and then the substrates are assembled into a stack with suitable gaps in between to allow for filling with an electro-optic material. The electro- optic material is filled into the inter- substrate gaps as a last step. Referring to the device shown in FIG. 12, substrate 304 is coated with electrode 305, substrate 1004 is coated with electrodes 303 (top) and 1005 (bottom), and mirror 201 is coated with electrode 203. Typical techniques for coating such films include vacuum deposition techniques (evaporation, sputtering, PECVD, and the like). The coated substrates are glued together in the proper order with, for example, a physical spacer (e.g., glass beads or photoresist stand-offs) to leave enough room for the electro-optic material. As a last step, the electro- optic material is filled into the gaps using capillary action or vacuum, forming layers 306 and 1006.

[0074] The embodiments disclosed above can transform a low cost, static, spherical reflective optic into one that has the potential to dynamically steer, focus, and correct for wavefront aberrations of incident optical radiation through the integration of a mostly transparent dynamic electro-optic device with the reflective surface of the optic. Such a device incorporates at least one thin layer of material whose index of refraction may be changed upon application of an electrical potential, a plurality of mostly transparent electrode structures to apply multiple potentials, and at least one of a mostly transparent substrate which contains one or more of the transparent electrodes and which may or may not contain a surface relief structure with an optical functionality (e.g. prism, grating, lens, etc.). The ability to change the refractive index of the layer of electro-optic material allows the material to impose phase changes on incident optical radiation such that after it is reflected from the mirror, a desired optical effect is achieved that could be difficult, expensive or impossible to achieve with a conventional static reflective optic. [0075] In some embodiments of the DEROs described herein and their alternatives, it may be desirable to emphasize steering of optical radiation over other functionalities such as, for example, providing optical phase control for light impinging and reflecting off of the DERO. An example of such an embodiment is in the use of DEROs in solar energy collection applications, where it may be advantageous to use a surface relief prism structure filled with an electro-optic material (e.g., FIG. 10) to provide maximal light steering capabilities over a broader range of incidence angles. [0076] A simplified embodiment of a solar energy collection system 1400 employing a DERO is illustrated in FIG. 14. The solar energy collection system 1400 for collecting light rays from the sun (indicated for different times of the day by lines 1401 , 1402, and 1403) includes a DERO 1000 (as described for FIG. 10), and a photovoltaic device 1410. The photovoltaic device 1410 can be any type of device for absorbing solar energy and converting the energy into electric current or electric potential. Non-limiting examples of photovoltaic devices 1410 include solar cells or solar cell arrays, including single layer p-n junction diodes, silicon, thin-film semiconductors, photoelectrochemical cells, polymer solar cells, and solar cells comprising nanocrystals as the solar absorption medium. Solar thermal systems are likewise included as an exemplary photovoltaic device 1410. In one example, focused light rays heat a liquid medium to produce steam, which, when forced through an orifice generates electricity by causing a turbine to rotate. Solar thermal systems can also be utilized simply to heat liquids such as water for domestic use.

[0077] The solar energy collection system 1400 operates by focusing sunlight throughout the day via the DERO 1000 onto the photovoltaic device 1410. Advantageously, the orientation of the DERO 1000 can remain stationary with respect to a terrestrial reference point, unlike traditional solar collection assemblies which must physically move in concert with the sun's diurnal course to keep sunlight properly focused on a photovoltaic element. Operationally, this feature is enabled by applying appropriate voltages to the DERO electrodes (203, 1005), causing a local index of refraction change to occur within the electro-optic material 1006. Depending on the incidence angle of the sun, and the relative positions/configurations of the DERO 1000 and the photovoltaic device 1410, the index of refraction within the electro-optic material 1006 can be adjusted, such that the sunlight reflected out of the DERO 1000 optimally impinges on the photovoltaic device 1410.

[0078] For example, FIG. 14 shows the sun at three different positions representing mid-morning (light rays 1401), noon (light rays 1402) and mid-afternoon (light rays 1403). Light ray 1401 is shown impinging on the DERO 1000 at an incidence angle, and the arrow denoted 1401a represents the vector of the light ray 1401 if it were to simply reflect off of the surface of the DERO 1000 without steering correction, or a conventional curved mirror assembly if the mirror was not pointed substantially at the source. However, when the DERO 1000 is operational, the light ray 1401 can be steered at an angle (toward the optical axis in this example) such that it reflects off of the reflective surface 202 at the proper angle to optimally impinge on the photovoltaic device 1410. This steering is accomplished by applying the appropriate voltages to electrodes 203 and 1005 so as to cause the index of refraction within the electro-optic material 1006 to steer the light ray 1401 in the appropriate direction.

[0079] At noon, the sun's rays 1402 are impinging on the DERO 1000 normally, and, in this case, a voltage may not need to be applied to the electrodes 203, 1005 in order to focus the light rays 1402 to the photovoltaic device 1410.

[0080] When the sun reaches the mid-afternoon position, the sun's rays 1403 again would again be focused away from the photovoltaic device 1410 as indicated by the arrow 1403 a. An appropriate steering correction is therefore required and accomplished as described with respect to the sun's position at mid-morning (rays 1401). In this example, a steering correction is needed which steers the light rays 1403 at an angle away from the optical axis of the DERO 1000, but still results in light rays 1403 impinging on the photovoltaic device 1410.

[0081] It should be understood that while FIG. 14 illustrates the DERO 1000 in an exploded view, and the light rays 1401, 1402, and 1403 are shown to change direction at the air/substrate 1004 interface, the total magnitude of steering results from light propagation throughout all layers of the electro-optic elements, namely, the substrate 1004, electrode 1005, electro-optic material 1006, and electrode 203. Furthermore, operationally, the choice of applied voltages to the electrodes 203, 1005 may need to take into account that the light rays pass through the electro-optic elements twice, once upon entering, and once upon exiting the electro-optic elements of the DERO 1000, depending on the incidence angle.

[0082] It should be understood that although the system in FIG. 14 is illustrated with a DERO 1000 of the configuration shown in FIG. 10, other configurations of DERO can be used, including the DEROs shown in FIGS. 2-9 and 11-13B. [0083] Adaptive control of light steering can be accomplished through feedback mechanisms that take into account the light flux at the target 103, e.g., a photovoltaic device 1410 or a photodiode for any of the described embodiments. Such a control system can be software driven, and apply voltages to the DERO electrodes to maximize a signal indicative of light flux at the target 103. For example, if target 103 is a photovoltaic, the magnitude of the photo-generated electrical current or potential can be monitored; the feedback mechanism can then adjust the applied voltages to the DERO electrodes such that the measured current or voltage is consistently maximized. Alternatively, a photodiode place on or near the target 103 can measure incident light and turn that light into an electrical signal that is monitored by the feedback mechanism. Similarly, the DERO electrode voltages would by controlled to maximize this signal. [0084] A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the embodiments described herein. For example, the relative sizes of the electrodes and surface relief structures in the previously mentioned embodiments play a large role in the mode of operation of the devices. When the sizes of the electrodes and surface relief structures are large compared to the wavelength(s) of optical radiation in use, the mode of operation is substantially refractive, and if the sizes of the electrodes and surface relief structures are comparable to the wavelength(s) of optical radiation in use, then the mode of operation is substantially diffractive. It should be noted that both refractive and/or diffractive modes of operation are considered within the scope of the present invention.

[0085] The use of multiple layers (i.e., layers 307a and 307b in FIG. 3) of electro- optic material elements are considered embodiments of all systems and methods disclosed herein. DEROs that incorporate polarization-sensitive or polarization-dependent electro- optic materials such as liquid crystals may require multiple layers to effectively steer light in a chosen direction.

[0086] Many laser cavity designs, including oscillators, amplifiers (including regenerative amplifiers, optical parametric amplifiers, and the like) make use of a cavity design wherein laser light within the cavity is focused off-axis by a curved reflective mirror to a lasing medium, such as Titanium: sapphire. This approach can make designing a stable laser cavity difficult, because the cavity depends on an optical mode that is deformed (aberrated) as little as possible. DEROs or multiple DEROs can be used in these and other laser applications, such as by using two DEROs in the cavity surrounding a lasing medium - one to focus the light to the lasing medium, and one to reflect and refocus the light after it has passed through the lasing medium. The DEROs in this example can control and/or correct laser mode aberrations, and/or adaptively correct mode structure in the laser output to produce optimal lasing results. [0087] Embodiments of the DEROs described above that include, for example, concentric ring electrodes have largely been described in the context of focusing light from a source remote from the DERO. However, it will be understood that the DERO can operate in a mode so as to defocus, or collimate light from a point source proximate to the DERO, essentially a reverse operation with respect to the above embodiments, as follows.

[0088] Referring to FIG. 5B, an embodiment of a system that uses a DERO includes a light source and elements of a DERO device such as has been described for FIG. 5 A. The light source can be positioned in front of the DERO such that its light rays impinge upon the reflective side of the reflective surface, for example, at position 505 or 510 in FIG. 5B. The light source can emanate light in all directions, or may have a reflective coating on one side (e.g., a light bulb having a mirrored coating on one half of its surface). The collimation of the light 501 that is reflected from the DERO 200 can be controlled by virtue of the refractive index gradient provided by the electro-optic layer 206. For example, the refractive index gradient of the electro-optic layer 206 can be controlled so as to provide the angular steering at various sections 206a-e shown in FIG. 5B, which, in this example, would result in a substantially perfectly-collimated beam output. In a similar fashion, the collimation of the beam can be controlled such that the beam diverges, or converges to a point in the far-field by appropriate application of voltages to the various sections of the electro-optic layer 206, i.e., sections 206a-e. [0089] In further embodiments, an optical cavity can be created that use one or more DERO 200 devices that define the cavity, e.g., a laser cavity. For example, a light source (such as a diode, or optically-pumped fluorescence emitter, such as a Titanium: sapphire rod) may be positioned in-between two DEROs 200, acting as a point light source as previously described. The light that emanates from the point source, e.g., at position 505, can be reflected by one of multiple DEROs 200 back toward the point light source; a second DERO 200 device at the other end of the optical cavity can reflect the light rays back toward the light source yet again. In these embodiments, it may be beneficial to use an optic such as an output coupler that "leaks" a certain percentage of the light through the optic as one of the substrates 202 upon which the electro-optic elements of the above-described DEROs 200 have been discussed. The mode structure of a beam formed in a cavity that uses DEROs as described may be precisely adjusted by virtue of the focusing control the DERO device provides.

[0090] The embodiments presented herein have been illustrated as modifying concave, spherical reflective surfaces and this is not to be considered as limiting. Additional embodiments also include the modification of convex, spherical reflective surfaces, aspherical reflective surfaces (both convex and concave) and substantially planar reflective surfaces. It should be further understood that the drawings included herein are not to scale, and relative dimensions different than those illustrated are possible. Accordingly, other embodiments are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A system for the steering light, comprising: an electro-optic steering assembly including: a substrate including an optically reflective surface; an electro-optic layer in optical communication with the substrate, where the electro-optic layer comprises: a first electrode layer comprising a plurality of separately addressable electrode components; a second electrode layer; an electro-optic material positioned between the first and second electrode layers; wherein voltages applied to the plurality of separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material such that light rays impinging on the electro-optic steering assembly and reflecting from the optically reflective surface are controllably steered in a direction.

2. The system of claim 1, wherein the optically reflective surface comprises a curved surface.

3. The system of claim 1, wherein the optically reflective surface comprises a planar surface.

4. The system of claim 1, further comprising a second electro-optic layer positioned in optical communication with the electro-optic layer, wherein the first electrode layer included in each electro-optic layer comprises a plurality of rectangular electrode components arranged parallel to one another and wherein the plurality of rectangular electrode components of the electro-optic layer are arranged perpendicular to the plurality of rectangular electrode components of the second electro-optic layer.

5. The system of claim 1, wherein at least one of the first electrode layer or the second electrode layer includes a transparent electrode.

6. The system of claim 1, wherein the plurality of electrode components comprise a plurality of rectangular electrode components arranged adjacent and substantially parallel one another.

7. The system of claim 1, wherein the plurality of electrode components are arranged in a two-dimensional array.

8. The system of claim 1 , wherein the light rays are steered toward a target location, the system further comprising: a photovoltaic device provided at the target location.

9. The system of claim 8, wherein the photovoltaic device comprises a solar cell including a semiconductor material that absorbs light rays.

10. The system of claim 1, wherein the light rays are steered toward a target location, the system further comprising: a solar thermal system provided at the target location.

11. The system of claim 1 , wherein the electro-optic material comprises nematic liquid crystal.

12. The system of claim 1, wherein the electro-optic material is selected from a group consisting of: cholesteric liquid crystal, smectic liquid crystal, polymer dispersed liquid crystal and polymer stabilized liquid crystal.

13. The system of claim 1, wherein the electro-optic material comprises a solid state electro-optic material.

14. The system of claim 13, wherein the solid state electro-optic material is selected from a group consisting of: lithium niobate (LiNbO₃) and lithium tantalite (LiTaO₃).

15. A system for the focusing light, comprising: an electro-optic assembly including: a substrate including an optically reflective surface; an electro-optic layer in optical communication with the substrate, where the electro-optic layer comprises: a first electrode layer comprising a plurality of separately addressable electrode components; a second electrode layer; an electro-optic material positioned between the first and second electrode layers; wherein voltages applied to the plurality of separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material such that light rays impinging on the electro-optic assembly and reflecting off the optically reflective surface are controllably focused toward a point in space.

16. The system of claim 15, wherein the optically reflective surface comprises a curved surface.

17. The system of claim 15, wherein the optically reflective surface comprises a planar surface.

18. The system of claim 15, wherein at least one of the first or second electrode layers includes a transparent electrode.

19. The system of claim 15, wherein the plurality of electrode components are arranged in a two dimensional array.

20. The system of claim 15, wherein the plurality of electrode components comprise a plurality of concentric ring electrode components.

21. The system of claim 15, further comprising: a photovoltaic device provided at the point in space to which the light rays are focused.

22. The system of claim 15, further comprising: a solar thermal system provided at the point in space to which the light rays are focused.

23. The system of claim 15, wherein the electro-optic material comprises a nematic liquid crystal.

24. The system of claim 15, wherein the electro-optic material is selected from a group consisting of: cholesteric liquid crystal, smectic liquid crystal, polymer dispersed liquid crystal and polymer stabilized liquid crystal.

25. The system of claim 15, wherein the electro-optic material comprises a solid state electro-optic material.

26. The system of claim 25, wherein the solid state electro-optic material is selected from a group consisting of: lithium niobate (LiNbO₃) and lithium tantalite (LiTaO₃).

27. The system comprising: an electro-optic assembly comprising: a first substrate including an optically reflective surface; a second substrate including a substantially smooth exterior surface and an interior surface comprising a surface relief optical structure; an electro-optic layer positioned between the first and second substrates, the electro-optic layer including a first electrode, a second electrode and an electro-optic material positioned therebetween; wherein: the first electrode is positioned between the electro-optic layer and the first substrate; the second electrode is positioned between the interior surface of the second substrate between the electro-optic material; and the electro-optic material conforms to the surface relief optical structure of the second substrate.

28. The system of claim 27, wherein the surface relief optical structure provides an optically refractive pattern providing a degree of optical steering of light rays impinging on the exterior surface of the second substrate.

29. The system of claim 27, wherein: an index of refraction of the electro-optic material is adjustably controllable by applying a voltage to at least one of the first or second electrodes.

30. The system of claim 27, wherein the surface relief optical structure comprises a series of prisms.

31. An electro-optic system, comprising: a substrate including an optically reflective surface; a first electro-optic layer in optical communication with the substrate, where the electro-optic layer comprises: a first electrode layer comprising a plurality of separately addressable electrode components; a second electrode layer; an electro-optic material positioned between the first and second electrode layers; wherein voltages applied to the plurality of separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material such that light rays impinging on the electro-optic steering assembly and reflecting from the optically reflective surface can be selectively:

(a) steered in a direction; (b) focused to a point in space; or

(c) both steered in a direction and focused to a point in space.

32. The system of claim 31 , wherein the optically reflective surface comprises a curved surface.

33. The system of claim 31 , wherein the optically reflective surface comprises a planar surface.

34. The system of claim 31 , wherein the plurality of electrode components are arranged in a two-dimensional array.

35. The system of claim 34, wherein the plurality of electrode components comprise a plurality of square shaped electrode components.

36. The system of claim 34, wherein the plurality of electrode components comprise a plurality of triangular shaped electrode components.

37. The system of claim 31 , further comprising: a second electro-optic layer in optical communication with the first electro-optic layer, the second electro-optic layer comprising: a third electrode layer comprising a plurality of separately addressable electrode components; a fourth electrode layer; an electro-optic material positioned between the third and fourth electrode layers; wherein the refractive index gradient of the first electro-optic layer is controlled to provide controllable steering of light rays impinging on the electro-optic system and reflecting from the optically reflective surface and a refractive index gradient in the second electro-optic layer is controlled to provide controllable focusing of the light rays to a point in space.

38. The system of claim 31 , further comprising : a second electro-optic layer in optical communication with the first electro-optic layer, the second electro-optic layer comprising: a second substrate including a substantially smooth exterior surface and an interior surface comprising a surface relief optical structure; a third electrode layer positioned on the interior surface of the second substrate; a fourth electrode layer; an electro-optic material positioned between the third and fourth electrode layers and conforming to the surface relief optical structure of the second substrate; wherein one of the electro-optic layers is configured to provide steering of light rays impinging on the electro-optic system and the other electro-optic layer is configured to provide focusing of light rays impinging on the electro-optic system.

39. The system of claim 38, wherein the second electro-optic layer is configured to provide steering of light rays, and an index of refraction of the electro-optic material is adjustably controllable by applying a voltage to at least one of the third or fourth electrodes, such that a total amount of optical wave steering is provided by a cumulative effect of light rays propagating through the surface relief optical structure and the electro- optic material.

40. The system of claim 39, wherein the surface relief optical structure comprises a series of refractive prisms.

41. A solar energy collection system, comprising: a substrate including an optically reflective surface; an electro-optic assembly including: a substrate including an optically reflective surface; an electro-optic layer in optical communication with the substrate, where the electro-optic layer comprises: a first electrode layer comprising a plurality of separately addressable electrode components; a second electrode layer; an electro-optic material positioned between the first and second electrode layers; wherein voltages applied to the plurality of separately addressable electrode components can be controlled to provide a controllable refractive index gradient in the electro-optic material such that light rays impinging on the electro-optic assembly and reflecting off the optically reflective surface are controllably focused toward a target location; and a photovoltaic device positioned at the target location.

42. The system of claim 41 , wherein the optically reflective surface comprises a curved surface.

43. The system of claim 41 , wherein the optically reflective surface comprises a planar surface.

44. The system of claim 41 , wherein the plurality of electrode components comprise a plurality of concentric ring electrode components.

45. The system of claim 41 , wherein the plurality of electrode components are arranged in a two-dimensional array.

46. A method comprising :

(a) receiving light rays onto a surface of an electro-optic reflective assembly comprising: a substrate including an optically reflective surface; and an electro-optic layer in optical communication with the substrate comprising: a first electrode layer comprising a plurality of separately addressable electrode components; a second electrode layer; and an electro-optic material positioned between the first and second electrode layers; and (b) selectively applying a voltages to the plurality of electrode components to selectively adjust a refractive index of the electro-optic material such that after the light rays exit the electro-optic layer and reflect off of the optically reflective surface, the light rays are directed towards a target location in space.

47. The method of claim 46, wherein the light rays comprises solar rays, the method further comprising : providing a photovoltaic device at the target location.

48. The method of claim 47, wherein adjusting the refractive index comprises adjusting the refractive index as the sun tracks across the sky, such that the solar rays are directed toward the photovoltaic device when the sun is at various positions in the sky throughout a day.