Patent Description:
A system is described herein and defined in claim <NUM>.

A method is described herein and defined in claim <NUM>.

Broadly, embodiments of the inventive concepts disclosed herein may be directed to a method and a system including an optical phased array and a radiofrequency (RF) phased array, wherein the optical phased array may be configured to control the RF phased array.

Some embodiments may include mixing two optical signals in a photodiode (often referred to as a photodetector). Some embodiments may include mixing a laser optical signal from a signal laser with a local oscillator (LO) optical signal from a LO laser. The following equations can be used to describe the mixing of the two optical signals. <MAT><MAT><MAT>.

Where Esig, ωsig, ϕ = signal electric field amplitude, frequency, phase, respectively.

Where ELO , ωLO = local oscillator electric field amplitude and frequency, respectively.

For example, mixing of the laser optical signal from the signal laser with the local oscillator (LO) optical signal from the LO laser may produce RF signals with frequencies equal to a sum and difference of the optical frequencies. For example, the difference term may be useful for creating microwave or millimeter-wave RF signals. For example, if the two lasers are phase locked, the phase of the optical signals may be maintained in such a created RF signal. For example, if the two optical signals include an optical signal and a local oscillator (LO) optical signal, the amplitude of the difference term may be proportional to a product of the optical signal and the LO optical signal amplitudes, which may allow for a signal gain.

In some embodiments, optical phased arrays can operate on similar principles as RF phased arrays. For example, the phases of individual optical emitters of an optical phased array may be controlled to form an optical wave front having a desired shape. For example, the phases may be evenly spaced by Δϕ (phase change) to form a planar wave front at an angle θ to the emitter plane. For example, Δϕ may be equal to <NUM>*Pi*d*sin(theta)/lamda, where: lambda = c/v = <NUM>*Pi*c/omega = optical wavelength; c = speed of light; and d = spacing between emitters.

In some embodiments, an output of an optical phased array may be mixed with an optical plane wave in a photodiode array of photodiodes. The optical frequencies of the output of the optical phased array and the optical plane wave may be selected such that a heterodyne signal may be upconverted to RF. The photodetected signal may preserve a phase of the optical phased array. The photodiodes may be connected <NUM>:<NUM> with antenna elements that emit the RF signal. For example, the output of the optical phased array may have a first angular frequency, the optical plane wave may have a second angular frequency equal to the first angular frequency plus delta, and the RF signal may have a frequency equal to delta/(<NUM>*Pi).

Some embodiments may provide benefits that reduce size, weight, and power (SWaP). Some embodiments may use optical heterodyning to allow for operation of RF phased arrays with large bandwidth.

Referring now to <FIG>, exemplary embodiments of a system <NUM> are shown.

As shown in <FIG>, the system <NUM> may include an optical phased array <NUM>, a beam splitter <NUM>, a photodiode array <NUM> of photodiodes 110A, an RF antenna element array <NUM> of RF antenna elements 112A, at least one processor <NUM>, a signal laser <NUM>, an LO laser <NUM>, and/or a collimating lens <NUM>. In some embodiments, one or more elements of the system <NUM> may be omitted.

The optical phased array <NUM> may steer an optical beam without needing any mechanical movement. The optical phased array <NUM> may include phase shifters <NUM> and an array of optical emitters <NUM>. The steering may occur by controlling the phase shifters <NUM> to manipulate the relative phase of a number of optical emitters <NUM>. The optical phased array <NUM> may be configured to receive a laser signal from the signal laser <NUM>. The optical phased array <NUM> may be configured to output an optical beam having an optical wave front <NUM>, the optical beam based at least in part on the laser signal. The optical beam may be steerable.

The processor <NUM> may be configured to control the phase shifters <NUM> of the optical phased array <NUM> to steer the optical beam of the optical phased array <NUM>. For example, the processor <NUM> may be configured to control the phase shifters <NUM> so as to steer the optical beam. In some embodiments, the processor <NUM> may be configured to cause a steering of the RF beam by controlling the phase shifters <NUM> of the optical phased array <NUM>. For example, the at least one processor <NUM> may include at least one central processing unit (CPU), at least one graphics processing unit (GPU), at least one field-programmable gate array (FPGA), at least one application specific integrated circuit (ASIC), at least one digital signal processor, at least one virtual machine (VM) running on at least one processor, and/or the like configured to perform (e.g., collectively perform if more than one processor) and/or cause (e.g., collectively cause) to be performed any of the operations disclosed throughout. The processor <NUM> may be configured to run various software applications or computer code stored (e.g., maintained) in a non-transitory computer-readable medium (e.g., memory) and configured to execute various instructions or operations. The processor <NUM> may be configured to perform any or all of the operations disclosed throughout.

The signal laser <NUM> may be configured to provide optical power to the optical phased array <NUM>. This power may be spread among optical emitters <NUM> of the optical phased array <NUM>.

The LO laser <NUM> may have a different wavelength from the signal laser <NUM>. The wavelength difference may be tuned to provide a desired RF output from the RF antenna element array <NUM>. An optical phase of the LO laser <NUM> and the signal laser <NUM> may be phase locked via a phase lock mechanism. The LO laser <NUM> may be used to produce an optical plane wave beam. The optical plane wave beam may have a fixed phase.

The collimating lens <NUM> may be positioned at an output of the LO laser <NUM> (e.g., positioned at an output aperture of the LO laser <NUM>) such that a collimated optical plane wave beam may be formed. For example, the collimating lens <NUM> may be configured to collimate the optical plane wave beam into a collimated optical plane wave beam prior to reaching the beam splitter <NUM>.

The beam splitter <NUM> may be coated glass or other material used to spatially overlap the optical beam of the optical phased array <NUM> and the collimated beam of the LO laser <NUM>. For example, the beam splitter <NUM> may be configured to spatially overlap the optical beam and the optical plane wave beam.

Each photodiode 110A of the photodiode array <NUM> may be configured to: receive at least a portion of the optical beam from the optical phased array <NUM> and at least a portion of the optical plane wave beam, wherein the optical plane wave beam is formed based at least on the LO laser <NUM> that outputs a laser beam having a different wavelength from the signal laser <NUM>, wherein the signal laser <NUM> and the LO laser <NUM> are phase locked; and/or output an electronic signal based on the at least the portion of the optical beam and the at least a portion of the optical plane wave beam. In some embodiments, the optical phased array <NUM> and the photodiode array <NUM> may be mechanically coupled to be in proximity to each other.

Each RF antenna element 112A of the RF antenna element array <NUM> may be electrically coupled to one of the photodiodes 110A. The RF antenna element array <NUM> may be configured to output an RF beam having an RF wave front <NUM> based on received electronic signals from the photodiode array <NUM>.

In some embodiments, the optical beam and the optical plane wave beam may be in the invisible spectrum of light (e.g., in the infrared (IR) spectrum (e.g., in the short-wave infrared (SWIR) spectrum)). In some embodiments, the optical beam and the optical plane wave beam may be in the visible spectrum of light.

Referring now to <FIG>, an exemplary embodiment of a portion of the system <NUM> of <FIG> is shown. The RF antenna element array <NUM> may be electrically coupled to the photodiode array <NUM> with an interconnect <NUM>. For example, the interconnect <NUM> may include (a) an interposer having vias between each RF antenna element 112A and one of the photodiodes 110A, (b) a direct solder connection between each RF antenna element 112A and one of the photodiodes 110A. For example, the interconnect <NUM> may be a substrate, wherein the RF antenna element array <NUM> is fabricated on first side of a substrate, wherein the photodiode array <NUM> is fabricated on a second side of the substrate.

Referring now to <FIG>, an exemplary embodiment of a portion of the system <NUM> of <FIG> is shown. In some embodiments, the system <NUM> may include a lens <NUM>. The lens <NUM> may be configured to focus a size of the optical beam and the optical plane wave beam onto the photodiode array <NUM>. In some embodiments, the lens <NUM> may be configured to match the optical phased array spacing to a differently sized photodiode array <NUM>. In some embodiments, a same optical phased array <NUM> may be used for RF antenna element arrays <NUM> designed to operate at different frequencies.

Referring now to <FIG>, an exemplary embodiment of a portion of the system <NUM> of <FIG> is shown. In some embodiments, the laser signal from the signal laser <NUM> is fed to a first set of the optical emitters <NUM> configured to output the optical beam, and the laser beam from the LO laser <NUM> is fed to a second set of the optical emitters configured to output the optical plane wave beam. The first set of the optical emitters <NUM> and the second set of the optical emitters <NUM> may be spatially interspersed. The first set of the optical emitters <NUM> may have output optical signals having a first wavelength with a steerable phase. The second set of the optical emitters <NUM> may have a second wavelength with a fixed phase. For example, such embodiments may allow for close coupling of the optical phased array <NUM> and the photodiode array <NUM>.

Referring now to <FIG>, an exemplary embodiment of a method <NUM> according to the inventive concepts disclosed herein may include one or more of the following steps. Additionally, for example, some embodiments may include performing one or more instances of the method <NUM> iteratively, concurrently, and/or sequentially. Additionally, for example, at least some of the steps of the method <NUM> may be performed in parallel and/or concurrently. Additionally, in some embodiments, at least some of the steps of the method <NUM> may be performed non-sequentially.

A step <NUM> may include receiving, by an optical phased array, a laser signal from a signal laser.

A step <NUM> may include outputting, by the optical phased array, an optical beam having an optical wave front, the optical beam based at least in part on the laser signal.

A step <NUM> may include receiving, by each photodiode of a photodiode array of photodiodes, at least a portion of the optical beam and at least a portion of an optical plane wave beam, wherein the optical plane wave beam is formed based at least on a local oscillator (LO) laser that outputs a laser beam having a different wavelength from the signal laser, wherein the signal laser and the LO laser are phase locked.

A step <NUM> may include outputting, by each photodiode of the photodiode array of the photodiodes, an electronic signal based on the at least the portion of the optical beam and the at least the portion of the optical plane wave beam.

A step <NUM> may include outputting, by a radiofrequency (RF) antenna element array of RF antenna elements, an RF beam having an RF wave front based on received electronic signals from the photodiode array, each RF antenna element electrically coupled to one of the photodiodes.

As will be appreciated from the above, embodiments of the inventive concepts disclosed herein may be directed to a method and a system including an optical phased array and a radiofrequency (RF) phased array, wherein the optical phased array may be configured to control the RF phased array.

As used throughout and as would be appreciated by those skilled in the art, "at least one non-transitory computer-readable medium" may refer to as at least one non-transitory computer-readable medium (e.g., at least one computer-readable medium implemented as hardware; e.g., at least one non-transitory processor-readable medium, at least one memory (e.g., at least one nonvolatile memory, at least one volatile memory, or a combination thereof; e.g., at least one random-access memory, at least one flash memory, at least one read-only memory (ROM) (e.g., at least one electrically erasable programmable read-only memory (EEPROM)), at least one on-processor memory (e.g., at least one on-processor cache, at least one on-processor buffer, at least one on-processor flash memory, at least one on-processor EEPROM, or a combination thereof), or a combination thereof), at least one storage device (e.g., at least one hard-disk drive, at least one tape drive, at least one solid-state drive, at least one flash drive, at least one readable and/or writable disk of at least one optical drive configured to read from and/or write to the at least one readable and/or writable disk, or a combination thereof), or a combination thereof).

Claim 1:
A system (<NUM>), comprising:
a signal laser (<NUM>), a local oscillator, LO, laser (<NUM>) and
an optical phased array (<NUM>) comprising an array of optical emitters, the optical phased array (<NUM>) configured to:
receive a laser signal from the signal laser (<NUM>); and
output an optical beam having an optical wave front (<NUM>), the optical beam based at least in part on the laser signal;
a photodiode array (<NUM>) of photodiodes (110A), each photodiode configured to:
receive at least a portion of the optical beam and at least a portion of an optical plane wave beam, wherein the optical plane wave beam is formed based at least on the LO laser that is configured to output a laser beam having a different wavelength from the signal laser, wherein the signal laser and the LO laser are phase locked; and
output an electronic signal based on the at least a portion of the optical beam and the at least a portion of the optical plane wave beam; and
a radiofrequency "RF" antenna element array (<NUM>) of RF antenna elements, each RF antenna element electrically coupled to one of the photodiodes, wherein the RF antenna element array is configured to output an RF beam having an RF wave front based on received electronic signals from the photodiode array; and characterized in that the signal laser is configured to feed its laser signal to a first set of the optical emitters configured to output the optical beam, wherein the LO laser is configured to feed its laser beam to a second set of the optical emitters configured to output the optical plane wave beam.