Patent Description:
Aspects described herein are generally related to the fields of optical communication and optical energy conversion. More specifically, aspects described herein provide a thin film communication and power generation device using a photovoltaic element, a retroreflector element, and an optical modulator element.

Autonomously operating systems are used in many fields of the modern economy. Their usage usually comprises the collection of environmental data, and subsequent data processing and aggregation, as well as data communication to and from a data transmitting, receiving and control system. To power autonomously operating systems, a reliable and standalone energy source is needed, such as solar power, batteries or similar. Radio frequency (RF) based systems are often used for communication to and between autonomous systems due to their simplicity of integration. However, radio frequency systems can be limited due to their short range of operation, high power requirements, signal interference, limited beam steering capabilities, and health risks. In particular, for military operations which require large standoff distances, radio frequency communication links are susceptible to detectability, spamming or spoofing. Optical communication systems, on the other hand, allow for high data rates and are less susceptible to signal interference. However, optical communication systems often require precise pointing control of both receiver and sender unit and often require large, heavy, and expensive optics. Therefore, the integration of optical communication systems can be complicated in a variety of autonomous and unmanned sensor, communication and transport systems, including but not limited to satellites, ground vehicles, unpiloted air vehicles, as well as consumer products.

<CIT>, <CIT>, <CIT> and <CIT> discloses examples of light-modulating reflectors.

The invention concerns an integrated device according to independent claim <NUM>. Further embodiments of the invention are found in the dependent claims.

The following summary presents a simplified summary of certain features. The summary is not an extensive overview and is not intended to identify key or critical elements. The invention is defined by the independent claim.

Aspects described herein provide a solution that allows both the generation of electrical energy and optical communication in one integrated device which is lightweight, mechanically flexible, and scalable for various energy generation and optical free-space (FSO) communication needs.

Aspects described herein may include a photovoltaic element, a retroreflector element, an optical modulator element, electrical contacts, and electrical conductors. An interrogating light beam can be pointed at the device, and a modulated light beam is reflected back by the device in the direction substantially parallel to the interrogating light beam with the reflected light beam containing information/data being modulated by the device onto the reflected light beam.

Described herein is an integrated optical communication and electrical energy generation device with at least one photovoltaic element, at least one light modulating element, a one or more first electrical contacts and/or conductors coupled to the at least one light modulating element, and at least one light reflecting element. The integrated optical communication and electrical energy generation device may also comprise one or more second electrical contacts and/or conductors coupled to the photovoltaic element. In some embodiments, power harvesting and storage circuitry may be connected to said second electrical contacts and/or conductors to convert and store the electrical energy generated by the photovoltaic element. A signal generating circuitry, which may be powered by the power harvesting and storage circuitry, may generate the electric signals for the light modulating element.

In some embodiments, the photovoltaic element may be adjacent to the light reflecting element. The photovoltaic element may receive a first light beam from a first direction, and may generate electrical energy from at least a portion of energy associated with the first light beam. The light modulating element may receive a second light beam from a second direction, and may modulate the second light beam in response to electric signals from the one or more first electrical contacts and/or conductors. The light reflecting element may redirect a substantial portion of the modulated second light beam in a third direction parallel to the second direction.

In some embodiments, the photovoltaic element may be adjacent to the light modulating element. The photovoltaic element may receive a first light beam from a first direction, and convert at least a portion of energy associated with the first light beam into electrical energy. The light modulating element may modulate a second light beam from a second direction in response to electric signals from the one or more first electrical contacts and/or conductors. The light reflecting element may redirect a substantial portion of the modulated second light beam in a third direction parallel to the second direction. In some embodiments, one or more first doped semiconducting elements may be disposed between the at least one modulator element and the light reflecting element, and one more second doped semiconducting elements may be disposed between the at least one light modulator element and the photovoltaic element.

In some embodiments, the integrated optical communication and electrical energy generation device may further comprise a transparent element or a display adjacent to the photovoltaic element.

Some embodiments of the integrated optical communication and electrical energy generation device may comprise a first light reflecting element and a second light reflecting element. The first light reflecting element may have a first internal surface adjacent to the photovoltaic element and a first external textured surface. The first light reflecting element may receive a first light beam from a first direction through the first external textured surface. The second light reflecting element may have a second internal surface adjacent to the light modulating element and a second external textured surface. The second light reflecting element may receive a second light beam from a second direction through the second external textured surface. The photovoltaic element may receive a third light beam from a third direction. The photovoltaic element may convert at least a portion of energy associated with the third light beam into electrical energy. The light modulating element may modulate at least one of the first light beam and the second light beam in response to electric signals from the one or more first conductors. The first light reflecting element may redirect a substantial portion of the second light beam in a fourth direction parallel to the second direction, and the second light reflecting element redirects a substantial portion of the first light beam in a fifth direction substantially parallel to the first direction.

Some embodiments of the integrated optical communication and electrical energy generation device may comprise a plurality of light modulating elements separated by one or more insulating layers and coupled to the one or more first conductors. The plurality of light modulating elements may comprise a first light modulating element adjacent to the photovoltaic element and a second light modulating element adjacent to the light reflecting element. The photovoltaic element receives a first light beam from a first direction, and converts at least a portion of energy associated with the first light beam into electrical energy. Each of the light modulating elements, from the plurality of light modulating elements, may modulate one or more second light beams within a light wavelength range specific to said light modulating element in response to electric signals from the one or more first conductors. The light reflecting element redirects a substantial portion of the modulated one or more second light beams in one or more third directions substantially parallel to the one or more second directions.

Some embodiments of the integrated optical communication and electrical energy generation device may comprise a plurality of photovoltaic elements and a plurality of light modulating elements disposed over the light reflecting element. An element from the plurality of photovoltaic elements and the plurality of light modulating elements receives a first light beam from a first direction. Each light modulating element from the plurality of light modulating elements, modulates the first light beam, within a light wavelength range specific to said light modulating element in response to electric signals from the one or more first conductors. Each photovoltaic element from the plurality of photovoltaic elements, converts at least a portion of energy associated with a second light beam from a second direction into electrical energy. The light reflecting element redirects a substantial portion of the modulated first light beam in a third direction parallel to the first direction.

Some embodiments of the integrated optical communication and electrical energy generation device may comprise a light reflecting substrate, a plurality of light modulating elements disposed over the light reflecting substrate, one or more first conductors coupled to the plurality of light modulating elements, a plurality of photovoltaic elements disposed over the plurality of light modulating elements, and one or more second conductors coupled to the plurality of photovoltaic elements.

Some embodiments of the integrated optical communication and electrical energy generation device may comprise temperature stabilizing circuitry, which may be powered by the power harvesting and storage circuitry, wherein the temperature stabilizing circuitry maintains an operating temperature of the integrated device.

Applications include but are not limited to systems which require an autonomous electrical energy supply as well as a data communication interface and link, such as satellites, unmanned airplanes, ground, marine and underwater vehicles, friend-or-foe detection devices, identification tags for consumer products and shipping containers; handheld mobile devices capable of optical communication; as well as road traffic signs.

Some advantages of the integrated optical communication and electrical energy generation device include: (a) self-powered, autonomous operation using ambient light including but not limited to the sun, or directed light sources such as lasers, (b) high data rates for optical communication, (c) suitability for short-range, medium-range and long-range communication links ranging from less than <NUM> to more than <NUM>, (d) suitability for multi-user/link operation, (e) lightweight and mechanically flexible/bendable structure with a thickness of less than <NUM>, and (f) scalability of the surface area of the device over several orders of magnitude from less than <NUM> square mm to more than <NUM> square m.

Other advantages comprise a design of the integrated optical communication and electrical energy generation device that is transparent at wavelengths visible to the human eye.

Some aspects, e.g., may be used to create an identification tag that cannot be spammed by radio frequency based systems. Some embodiments are particularly useful for space applications. For example, satellite attitude control requirements can be largely reduced, which complicated the integration of FSO links into smaller satellites in the past. The combined optical communication and power generation device can be integrated into existing satellite solar arrays at virtually no additional weight and no additional surface area requirements. The combined optical communication and power generation device can replace and/or complement otherwise power consuming and heavy RF communication equipment and overcome already challenging RF bandwidth limitations, in particular for large CubeSat constellations. The combined optical communication and power generation device can also enable FSO communications between Earth and a lunar lander or a deep space platform.

Furthermore, the "Internet of Things" movement has produced an increasing number of autonomously operating sensor and data transmission systems which leads to an increasing number of autonomously operating sensor and data transmission systems for which energy efficient operation, secure communication, and high data transmission rates are crucial. This trend is supported by autonomously operated vehicles and their increasing need for secure, high-speed data exchange for which optical data links can be attractive in dense traffic conditions. The combined optical communication and power generation device can add a power and data exchange capability to such an autonomously operating sensor and data transmission systems.

These and other features and advantages are described in greater detail below.

Some features are shown by way of example, and not by limitation, in the accompanying drawings. In the drawings, like numerals reference similar elements.

Example and illustrative methods and systems are described herein. Any illustrative embodiment or feature described herein is not necessarily to be construed as preferred or advantageous over other embodiments or features. The illustrative embodiments and aspects described herein are not meant to be limiting. It will be readily understood that certain aspects of the disclosed systems and methods can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

Furthermore, the particular arrangements shown in the Figures should not be viewed as limiting. It should be understood that other embodiments and/or aspects may include more or less of each element shown in a given Figure. Further, some of the illustrated elements may be combined, split into multiple components/steps, or omitted. Yet further, one or more illustrative embodiments may include elements that are not explicitly illustrated in the Figures.

Aspects described herein contribute to an apparatus, method of manufacturing, and system for an integrated optical communication and electrical energy generation device. The apparatus or system may be used in diverse commercial, consumer, defense, aerospace, environmental, road safety, transportation, and telecommunication related applications. Aspects and features described in the following combine the electrical energy generation capability of a photovoltaic device with the optical data communication capability of an electrically modulated retroreflector in one device.

<FIG> shows an illustrative embodiment of the integrated optical communication and electrical energy generation device <NUM> of the invention. The device includes a photovoltaic element <NUM> for light to electrical energy conversion, an electrically controlled light modulator element <NUM> which is able to change its transparency for light of a defined wavelength range as a function of an externally applied electrical signal, a retroreflector element <NUM>, such as a cat-eye reflector or a corner cube reflector, which is able to reflect the modulated light <NUM> back in the direction of the incoming light beam <NUM>.

The photovoltaic element <NUM> absorbs incoming light <NUM>, such as light from the sun <NUM>, ambient room light or otherwise suited light sources and convert the incoming light to electrical energy which can be made available to a power harvesting and storage circuitry <NUM> through electrical contacts and/or conductors <NUM> and <NUM>. The photovoltaic element may consist of a planar semiconductor p-n diode made of Silicon, GaAs, InGaAs or other semiconductors, such as III-V semiconductors like GaInP, InP, AlGaAs or similar, or other materials suited for photovoltaic energy conversion, like CdTe, CIGS, or similar. The photovoltaic element <NUM> absorbs a portion of the incoming light within a certain wavelength range as defined by the photovoltaic element's bandgap energy or light absorption characteristics. The photovoltaic element <NUM> is transparent in a certain wavelength range or semi-transparent in a certain wavelength range, such that incoming light of a certain wavelength range reaches the optical modulator <NUM>. For example, the photovoltaic element may not include any metal backing, and may be constructed on a transparent wafer or handling substrate which may be polished on one or both sides.

The optical modulator <NUM> is configured to change its transparency for light of a certain wavelength range as a function of an electrical signal which can be applied through electrical contacts and/or conductors <NUM> and <NUM> by the signal generating circuitry <NUM>. The signal generating circuitry <NUM> may be powered by the power harvesting and storage circuitry <NUM>. Incoming light <NUM> of a certain wavelength range and incident angle can pass through the photovoltaic element <NUM> towards the optical modulator <NUM> where depending on the externally applied electrical signal, the modulator can impose a digital or analog or otherwise suited modulation onto the light, including but not limited to states of the modulator during which the modulator is transparent, semi-transparent or opaque or during which the modulator affects, changes, modulates, transmits, or absorbs light of a defined polarization. The modulation allows encoding information/data onto the incoming light <NUM>. The optical modulator may comprise one or a multitude of the following elements, including but not limited to a liquid crystal modulator, an acoustooptic modulator, a Fabry-Perot based modulator, a multi-quantum well (MQW) based modulator, a distributed Bragg-reflection modulator, an optically tunable filter modulator, a polarization modulator, or similar. Modulation frequencies may be in the range of <NUM> or less to <NUM> or more.

A retroreflector element <NUM> reflects the modulated light <NUM> back in the direction <NUM> substantially parallel to the direction of the incoming light <NUM>. The retroreflector may consist of a corner cube reflector, a spherical reflector, a phase-conjugate mirror, moth-eye like gratings, gratings, dispensed spheres, etched structures, holographic structures or otherwise suited mirror or reflector materials including but not limited to commercially available reflective tape such as <NUM> flexible prismatic reflective sheeting, or a combination thereof. A corner cube reflector may be fabricated by use of a Nickel shim from a master polymer via two-photon absorption for sharp corners and defined angles. The retroreflector element <NUM> may also be designed to reflect the modulated light <NUM> back in a desired direction which is not parallel to the direction of the incoming light <NUM>.

Once the reflected and modulated light <NUM> exits the integrated optical communication and electrical energy generation device, it contains data/information which can be detected and recorded by a communication and control system <NUM>. Control system <NUM> may comprise a telescope and/or a photodiode.

The integrated optical communication and electrical energy generation device <NUM> may have a height of less than <NUM>. Due to its relatively thin thickness, the integrated optical communication and electrical energy generation device <NUM> may be mechanically flexible and may be attached to certain objects like a regular sticker. The device and elements of the integrated optical communication and electrical energy generation device <NUM> can be manufactured by epitaxial growth, epitaxial lift-off, bonding, transfer printing, mechanical stacking, gluing, similar methods, or a combination of said methods. A device <NUM> that is manufactured using epitaxial processes may be comprised of a single or double-sided polished (DSP) wafer or a substrate made of GaAs, InP, Si, Ge or similar to achieve desired properties of optical reflection, diffraction, transmission, surface smoothness, and device flatness.

The electrical energy generated by the photovoltaic element <NUM> may be used to power and control the optical modulator <NUM> as well as the signal generating circuitry <NUM>. This makes the integrated optical communication and electrical energy generation device <NUM> suitable for applications that require (a) standalone operation without an external electrical energy source, (b) long operational lifetime, (c) a high speed optical data communication interface, (d) data readout capability from a long standoff distance, as well as resilience against radio frequency spamming or spoofing.

The wavelength range of the incoming light <NUM> to be modulated by device <NUM> may be in the range of <NUM> or less to <NUM> or more, whereas the wavelength may be chosen to be larger than the respective wavelength of the bandgap energy of the photovoltaic element <NUM> to minimize absorption losses within device <NUM>. In an exemplary embodiment of device <NUM> with a photovoltaic element <NUM> comprised of GaAs having a bandgap energy at room temperature corresponding to the absorption of photons with a wavelength of less than approximately <NUM> a suitable operating wavelength range of the modulator element <NUM> may be within <NUM> or less and <NUM> or more including wavelengths of up to approximately <NUM> to best couple to commercially available laser systems. Multi-quantum-well modulators operating in such a wavelength range can be fabricated via epitaxial growth including but not limited to the usage of III-V semiconductors such as InGaAs, InGaAsP, InP, InAsP, AlGaAs, InAlGaAs, GaAsP, or similar. The applied electrical signal to the electrical contacts of the modulator <NUM> and <NUM> may be a voltage of less than 5V or a voltage of more than 15V.

Standard solar cells often have a metalized electrically conductive rear side which absorbs light and which generally yields very low optical transmission properties. The photovoltaic element <NUM> for usage in device <NUM> may be comprised of an electrically conductive rear side which may be located at the interface between photovoltaic element <NUM> and modulator <NUM>, and which may be optically transparent in a defined wavelength range. Said electrically conductive rear side of the photovoltaic element <NUM> may contain or may be made of a highly doped semiconductor lateral conduction layer, an Indium-Tin-Oxide (ITO) layer, a fluorine doped tin oxide (FTO) layer, a carbon nanotube network layer, a graphene layer, a doped zinc oxide layer, a combination of such layers, or an otherwise suited optically transparent and electrically conductive layer. The electrically conductive rear side of photovoltaic element <NUM> may be electrically connected to the electrical contact <NUM>. The electrical contact <NUM> may serve as a common ground for both the photovoltaic element <NUM> and the modulator <NUM> such that device <NUM> may be a three-terminal device. Metal interconnects, contacting schemes and technologies, as exemplarily described in <CIT> for usage in an III-V semiconductor three-terminal device, may be used to as electrical contacts.

In another exemplary embodiment, the photovoltaic element <NUM> and the light modulating element <NUM> may have no common electrical contact or contacts. The photovoltaic element <NUM> and the light modulating element <NUM> may have individual electrical contacts and may be separated by an electrically insulating and for the modulated light optically transparent layer located between photovoltaic element <NUM> and the light modulating element <NUM> such that the device <NUM> may have four or more electrical terminals.

In another exemplary embodiment, the device <NUM> may have two electrical contacts, also referred to as a two terminal device, such that the photovoltaic element <NUM> and the light modulating element <NUM> may be electrically connected and said electrical connection may not be available as an external electrical contact.

If device <NUM> is operated in an environment in which large fluctuations of temperature occur, such as in space, the wavelength dependent absorption, transmission, polarization and modulation properties of the photovoltaic element <NUM>, the light modulating element <NUM>, and the light reflecting element <NUM> may change with temperature. This may be accounted for by a change of the emitting and/or receiving light wavelength and/or light polarization properties of the communication and control system <NUM>. That is, the wavelength range of multi-quantum-well modulators may shift with temperature. Existing laser systems allow for the changing of the emitted wavelength and thus could be used to account for the potential change of the temperature dependent characteristics of multi-quantum-well modulators or other light modulating elements. Similarly, temperature-induced changes of the polarization properties of device <NUM> may be accounted for by changing the emitting and receiving light polarization properties of the communication and control system <NUM>. The temperature of device <NUM> may also be stabilized by a heater or a cooler which may be controlled and powered fully or in part by electrical energy generated by the photovoltaic element <NUM> and stored in the power harvesting and storage circuitry <NUM>.

The angle of incidence of the incoming light <NUM> may be within <NUM> degrees from normal to about <NUM> degrees or more from normal.

Multiple communication and control units <NUM> may be used simultaneously and/or sequentially from similar and/or different directions and incoming angles to read data from device <NUM>.

The incoming light <NUM> may already be modulated. Said modulation of the incoming light may be by modulation of the light intensity, the light wavelength, the modulation frequency, the light polarization, or a combination of said modulation methods. A sensor, such as a photodiode or a filtered photodiode, can be attached to or be integrated into device <NUM> to measure and record this modulation. The modulated signal may comprise instructions for device <NUM>, such as instructions on which information/data shall be modulated onto the light beam by device <NUM> prior to the light being reflected back to control unit <NUM>. Said instructions may also contain information on the desired modulation data rate, method, duty cycle, electrical energy usage, or similar.

The photovoltaic element <NUM> may be operated in reverse, e.g., as a light emitting diode, to emit light with modulated data/information into a multitude of directions.

The order in which optically relevant elements and/or electrically relevant elements, such as electrical contacts, are stacked or arranged within device <NUM> may be changed in part or as a whole, including but not limited to the placement of the light modulating element <NUM> at the or near the surface of device <NUM> and/or on top of the photovoltaic element <NUM>.

In some cases, the modulating frequency may be increased by segmenting the device <NUM> into smaller sub-devices which may be arranged in a mosaic or array pattern and which may be driven with the same or different modulation signals. A reduced area size often correlates with a reduced RC switching time and reduced power consumption. Segmentation may be achieved via localized etching, localized ion bombardment, transfer printing, cutting, or similar methods. Electrical contacts to the sub-devices may comprise wires, backside contacts, metal-wrap-through technology, or other contact technology that may be realized from the rear side of the device. Segmentation size and shape of the modulating element and the photovoltaic element may be similar or different. Only the modulating element may be segmented whereas the photovoltaic element may be unsegmented. Sub-devices may be smaller than <NUM> square mm or larger than <NUM> square mm.

Several devices <NUM> may also be arranged in pairs or in an array whereas the respective electrical contacts of each photovoltaic element <NUM> may be connected in parallel or series, individually connected or a combination thereof and whereas the electrical contacts of each optical modulator element <NUM> may be connected in parallel, series, individually or a combination thereof. In such a paired or array configuration of serval devices <NUM> the overall area suitable for light to electrical energy conversion via the photovoltaic element may be increased by the factor of the amount of paired devices <NUM> whereas the effective area determining the RC switching time of the light modulating element may remain unchanged which may be favorable for overall fast data rates and increased energy generation of device <NUM>.

<FIG> illustrates a schematic view of the integrated optical communication and electrical energy generation device <NUM> in <FIG>. The device may include a photovoltaic element <NUM>, an electrically controlled light modulator element <NUM>, a retroreflector element <NUM> and electrical contacts and conductors, such as the conductive strips 210a, 210b, 210c, <NUM>, and <NUM>. The conductive strips 210a, 210b, 210c, <NUM>, and <NUM>, may be made of polysilicon, metal or other suitable conductive material, such as a plurality metal layers made of tungsten (W), titanium nitride (TiN), tantalum nitride (TaN) or the arbitrary combinations thereof.

The retroreflector element <NUM> may be separated from the conductive strip <NUM> by a first doped semiconducting element <NUM>. Even though only one conductive strip is shown between the retroreflector element <NUM> and the first doped semiconducting element <NUM>, multiple conducting strips may be disposed on top of the first doped semiconducting element <NUM>. The electrically controlled light modulator element <NUM> is disposed on top of the first doped semiconducting element <NUM> and is electrically coupled to the conductive strip <NUM>, and any other conductive strips disposed on top of the first doped semiconducting element <NUM>. Electrical signals can be applied through the conductive strip <NUM>, and any other conductive strips disposed on top of the doped semiconducting element <NUM> to the optical modulator element <NUM>. A second doped semiconducting element <NUM> may be disposed on top of the electrically controlled light modulator element <NUM>. A second plurality of conductive strips, such as the conductive strip <NUM>, is disposed on top of the second doped semiconducting element <NUM>. The second plurality of conductive strips, such as the conductive strip <NUM>, may act as a ground contact for the integrated optical communication and electrical energy generation device <NUM>. The photovoltaic element <NUM> is disposed on top of the second doped semiconducting element <NUM> and is electrically coupled to the conductive strip <NUM>, and any other conductive strips disposed on top of the second doped semiconducting element <NUM>. A third doped semiconducting element <NUM> may be disposed on top of the photovoltaic element <NUM>. A third plurality of conductive strips, such as the conductive strips 210a, 210b, and 210c, is disposed on top of the third doped semiconducting element <NUM>. Converted electrical energy from the photovoltaic element <NUM> can be made available through the third plurality of conductive strips, such as the conductive strips 210a, 210b, and 210c. The first doped semiconducting element <NUM>, the second doped semiconducting element <NUM> and the third doped semiconducting element <NUM> may comprise high and/or low doped semiconductor layers or an otherwise suited optically transparent material such as glass or similar or a combination thereof.

<FIG> shows another illustrative aspect of the integrated optical communication and electrical energy generation device, comprising two retroreflector elements <NUM> and <NUM> with textured surfaces. As described here, a textured surface is a surface that is not smooth, such as the front surface of the retroreflector element <NUM> and the back surface of the retroreflector element <NUM> with convex and/or concave shapes, lenses and/or mirrors to direct the exiting light <NUM> back in the direction of the incoming light <NUM>. Back surface of the retroreflector element <NUM> and/or front surface of the retroreflector element <NUM> may partially or fully comprise a reflective surface and/or a reflective coating functioning as an optical mirror.

The back surface of the retroreflector element <NUM> and/or front surface of the retroreflector element <NUM> may also be shaped such that an incoming light beam <NUM> towards the rear side of device <NUM> is reflected within device <NUM> and exits device <NUM> at the rear side in a direction <NUM> parallel to the incoming light beam or at a desired angle relative to the incoming light.

The photovoltaic element <NUM> of device <NUM> may absorb and convert ambient light into electricity which impinges onto the front side <NUM> and/or onto the rear side <NUM> of device <NUM>.

<FIG> shows another illustrative aspect of the integrated optical communication and electrical energy generation device (e.g., used with, on, and/or in a mobile phone), comprising a display <NUM> or a transparent element with electrical contacts <NUM>. The display or the transparent element <NUM> may be transparent or semi-transparent for incoming light <NUM> and exiting light <NUM>. The display <NUM> may emit light <NUM> in a multitude of directions.

In some illustrative embodiments, the display <NUM> may itself be transparent or semitransparent, or alternatively may be permanently transparent to light within a predefined wavelength range. In some embodiments, a transparent OLED may be used, or the display may be made of glass (e.g., a window) or other transparent or semitransparent material. In such an embodiment, ambient light <NUM> and the photovoltaic element <NUM> may power the modulator <NUM>. The modulator <NUM> provides information and/or data in accordance with aspects described herein such that the data would become available inside a room, predefined area, or within a line of sight from the display, for instance where a receiver device <NUM> can receive the modulated signal <NUM> using a photodiode. In such an embodiment, the display may remain transparent to the human eye, and infrared wavelengths may be modulated to provide information to a receiving device without significantly altering the transparency and/or legibility of the display and without the display significantly altering and/or absorbing the modulated light <NUM>. If no energy generation is required for device <NUM>, the photovoltaic element <NUM> may be omitted.

<FIG> shows another illustrative aspect of the integrated optical communication and electrical energy generation device, comprising a first optical modulator <NUM> and a second optical modulator <NUM>. The first optical modulator <NUM> may modulate incoming light <NUM> within a defined wavelength range. The second optical modulator <NUM> may modulate incoming light <NUM> within a defined wavelength range that may be different from the wavelength range of the first optical modulator <NUM>. This allows simultaneous and independent data modulation for different light sources and receivers as indicated by incoming light beams <NUM>, <NUM> and exiting light beams <NUM>, <NUM>, respectively.

At the interface between the optical modulator <NUM> and optical modulator <NUM>, an electrically isolating layer <NUM> may be located to allow for electrical isolation and independent operation of both optical modulators. An electrical signal may be applied to the first optical modulator <NUM> via electrical contacts <NUM> and <NUM>/<NUM>. An electrical signal may be applied to the second optical modulator <NUM> via electrical contacts <NUM> and <NUM>. For the synchronous operation of both optical modulators <NUM> and <NUM>, the electrically insulating layer <NUM> may be omitted, and an electrical signal may be applied to both modulators via electrical contacts <NUM> and <NUM>/<NUM>. In another embodiment, the layer <NUM> may alter the polarization of the incoming and/or modulated light. In another embodiment, device <NUM> may contain one, two, or more optical modulators. The electrically insulating layer <NUM> may be a low doped semiconductor layer, a low doped semiconductor wafer, or an otherwise suited optically transparent material such as glass or similar, or a combination thereof.

<FIG> shows another illustrative aspect of the integrated optical communication and electrical energy generation device, comprising a first photovoltaic device <NUM>, a first optical modulator <NUM>, a second photovoltaic device <NUM>, and a second optical modulator <NUM>. The second optical modulator <NUM> may modulate incoming light <NUM> within a defined wavelength range that may be different from the wavelength range of the first optical modulator <NUM>. The first optical modulator <NUM> may be designed for light modulation within a wavelength range of approximately <NUM> or less to <NUM> or more. The second optical modulator <NUM> may be designed for light modulation within a wavelength range of approximately <NUM> or less to <NUM> or more. This allows simultaneous and independent data modulation for different light sources and receivers as indicated by incoming light beams <NUM>, <NUM> and exiting light beams <NUM>, <NUM>, respectively. The second photovoltaic element <NUM> may have a lower bandgap energy than the first photovoltaic element <NUM> and may convert light within a defined wavelength range into electricity and/or may operate as an optical detector, such as a photodiode, whereas the first photovoltaic may also function as an optical filter for light with wavelengths lower than its respective bandgap energy. In some embodiments, more than two, and even six or more photovoltaic elements may be grown or stacked on top of each other, each with a different bandgap. In some embodiments, more than two optical modulators may be grown or stacked on top of each other. In some embodiments, the optical modulators may alter the light polarization.

<FIG> shows another illustrative aspect and method of the integrated optical communication and electrical energy generation device <NUM> in which the optically relevant elements and/or electrically relevant elements, such as electrical contacts, may be stacked or arranged within device <NUM> such that an incoming and interrogating light beam <NUM> may be modulated and reflected back in direction <NUM> with said light beams reaching and exiting device <NUM> on its front side and such that ambient light <NUM> may be converted to electrical energy by the photovoltaic element when reaching the device <NUM> on its rear side. Additional layers, such as glass, a semiconductor wafer, Kapton, Mylar, a polymer layer, a similarly suited layer, or a combination of said layers may be incorporated into device <NUM> for purposes of electrical insulation, mechanical stability, handling, electrical conduction, electrical contacts, or similar.

<FIG> shows another illustrative aspect and method of the integrated optical communication and electrical energy generation device for usage as an optical communication and electrical energy generation device on a satellite. The satellite <NUM> is shown with two arrays which may be fully or partly comprised of the integrated optical communication and electrical energy generation device <NUM> or arrays of the integrated optical communication and electrical energy generation devices. Electrical energy can be generated by light to electricity conversion of the photovoltaic element inside the integrated optical communication and electrical energy generation device <NUM>. A source for incoming light <NUM> for light to electricity conversion may be the sun <NUM>. A transmitter and receiver unit <NUM> may be located on the surface of the Earth <NUM> or may also be located on another satellite. The transmitter and receiver unit <NUM> may use a laser beam <NUM> directed towards the satellite <NUM> and receive modulated light <NUM> which contains information/data of the satellite <NUM>. Aspects described herein overcome current system integration limitations since both the photovoltaic element and the free space optical communication system are combined in one device. Further, the large surface area typically used for photovoltaic arrays can now be used by the integrated optical communication and electrical energy generation device as a large area optical communication interface. The energy-intensive part of sending a laser beam to the satellite relies solely upon the ground station <NUM> and saves energy on the satellite platform <NUM>.

<FIG> shows another illustrative aspect and method of the integrated optical communication and electrical energy generation device for usage in road safety and vehicle guidance and communication systems. The integrated optical communication and electrical energy generation device <NUM> may be integrated into a road sign <NUM>. A lamp <NUM> of a vehicle <NUM>, including but not limited to an incandescent bulb, an LED, a laser or a combination thereof, may be directed towards the road sign <NUM>, indicated by light beam <NUM>. Information/data contained within the road sign <NUM>, including but not limited to location, outside temperature, traffic information, or similar can be sent to a receiver contained in the vehicle <NUM> via a modulated light beam <NUM>. Further, the reflective nature of road sign <NUM> allows for measurement of the time-of-flight between vehicle <NUM> and road sign <NUM> to determine the distance and velocity of vehicle <NUM>. Since the road sign <NUM> reflects the light back in the same direction of the incoming light, one or more vehicles <NUM> can simultaneously receive information/data from the road sign <NUM>, as indicated by light beams <NUM> and <NUM> and lamp <NUM>. The integrated photovoltaic element allows for self-powered operation of the road sign. Light beams <NUM> and <NUM> may already contain modulated data which may be recorded by the road sign for retransmission to other vehicles.

<FIG> shows another illustrative aspect and method of the integrated optical communication and electrical energy generation device <NUM> for usage in transport, logistics, and inventory systems. Parcels <NUM> and <NUM> may be stored in a warehouse at different locations. A transmitter and receiver unit <NUM> may use a directed light beam <NUM> and <NUM>, including but not limited to a laser beam, to direct light towards a tag <NUM> and <NUM> which are attached to the parcel <NUM> and <NUM> and which contain said device <NUM> to obtain information/data on the properties of the parcel via a modulated and reflected light beam <NUM> and <NUM> containing these information/data. Further, through the time of flight measurements, the distance between the transmitter and receiver unit and one or a multitude of parcels <NUM> and <NUM> can be measured. In addition, since a directed and narrow light beam <NUM> and <NUM> is used, the angular orientation of the parcel <NUM> and <NUM> and their attached tags <NUM> and <NUM> with respect to the transmitter and receiver unit <NUM> may be obtained via a measurement of the orientation of the light source located within the transmitter and receiver unit <NUM>. The combination of the measurement of the time-of-flight, i.e., distance, and angular orientation allows the determination of the location of the parcel within <NUM>-dimensional space. The reflected and modulated light beam may contain information on the properties of the parcel or otherwise relevant information.

<FIG> shows another illustrative aspect of the integrated optical communication and electrical energy generation device <NUM> with smaller sub-devices, such as the sub-devices <NUM>, <NUM>, <NUM>, <NUM>. The sub-devices may be arranged in a mosaic or array pattern. The sub-devices may share a common retroreflector element <NUM> and have its individual photovoltaic element <NUM> and electrically controlled light modulator element <NUM>. In some embodiments, the arrays of sub-devices may share common electrical contacts, such as the electrical contacts <NUM>, <NUM>, and <NUM>. In some embodiments, rows or columns of sub-devices in the array may share common electrical contacts. In other embodiments, each sub-device may have its own electrical contacts <NUM>, <NUM>, and <NUM>.

The photovoltaic element <NUM> of each sub-device may absorb incoming light <NUM>, such as light from the sun <NUM>, ambient room light or otherwise suited light sources and convert the incoming light to electrical energy which can be made available to an external circuit through electrical contacts <NUM> and <NUM> and stored in the power harvesting and storage circuitry <NUM>. The optical modulator <NUM> of each sub-device may change its transparency for a light of a certain wavelength range as a function of an electrical signal which can be applied through electrical contacts <NUM> and <NUM>. The common retroreflector element <NUM> reflects the modulated light <NUM> back in the direction <NUM> substantially parallel to the direction of the incoming light <NUM>.

The electrically controlled light modulator element <NUM> may change its transparency for a light of a certain wavelength range as a function of an electrical signal which can be applied through electrical contacts <NUM> and <NUM> by the signal generating circuitry <NUM>. The signal generating circuitry <NUM> can be powered by the power harvesting and storage circuitry <NUM>.

The temperature of device <NUM> may also be stabilized by a heater or a cooler which may be controlled and powered fully or in part by electrical energy generated by the photovoltaic element <NUM> and stored in the power harvesting and storage circuitry <NUM>.

<FIG> shows another illustrative aspect of the integrated optical communication and electrical energy generation device <NUM> with smaller sub-devices, such as the sub-devices <NUM> and <NUM>. The sub-devices may be arranged in a mosaic or array pattern. The sub-devices may share a common photovoltaic element <NUM> and have its individual electrically controlled light modulator element <NUM> and retroreflector element <NUM>. In some embodiments, the arrays of sub-devices may share common electrical contacts, such as the electrical contacts <NUM>, <NUM>, <NUM>, and <NUM>. In some embodiments, rows or columns of sub-devices in the array may share common electrical contacts. In other embodiments, each sub-device may have its own electrical contacts <NUM> and <NUM> with common electrical contacts <NUM> and <NUM> for the photovoltaic element <NUM>.

The photovoltaic element <NUM> of each sub-device may absorb incoming light <NUM>, <NUM><NUM>, such as light from the sun <NUM>, ambient room light or otherwise suited light sources and convert the incoming light to electrical energy which can be made available to an external circuit through electrical contacts <NUM> and <NUM> and stored in the power harvesting and storage circuitry <NUM>. The optical modulator <NUM> of each sub-device may change its transparency for a light of a certain wavelength range as a function of an electrical signal which can be applied through electrical contacts <NUM> and <NUM>. The retroreflector element <NUM> reflects the modulated light back in the direction <NUM> substantially parallel to the direction of the incoming light <NUM>.

Claim 1:
An integrated device comprising:
at least one photovoltaic element (<NUM>), wherein the at least one photovoltaic element is adapted to receive a light beam and generates power from a first portion of the received light beam (<NUM>) that are within a first wavelength range;
at least one light modulating element (<NUM>) disposed on the at least one photovoltaic element, wherein the at least one light modulating element, based on one or more input signals, is adapted to modulate a second portion of the received light beam (<NUM>) that is within a second wavelength range, and wherein wavelengths in the first wavelength range are smaller than wavelengths in the second wavelength range; and
at least one light reflecting element (<NUM>) disposed on the at least one light modulating element, wherein the at least one light reflecting element is adapted to reflect the modulated second portion of the light beam in a direction substantially parallel to the received light beam.