Photoactivated antenna system

Abstract

An antenna system may include a radiator comprising a photoconductive region. The photoconductive region may transition from a dielectric to a conductor in response being photoactivated. Light sources may be directed at the radiator. Each of the light sources activate a corresponding portion of the photoconductive region to form an array of radiator pixels. An optical control network may cause at least one of the lights sources to emit light onto the radiator an activate at least one of the pixels. An Radio Frequency (RF) feed network may cause at least one of the radiator pixels of to emit or receive electromagnetic waves.

Description

PHOTOACTIVATED ANTENNA SYSTEMCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 541 ,719 filed September 29, 2023, the entirety of which is hereby incorporated by reference.TECHNICAL FIELD

[0002] This disclosure relates to antennas and, in particular, to plasma antennas.BACKGROUND

[0003] When a semiconductor is excited by light with photon energy (hv) greater than the semiconductors bandgap, a solid-state plasma of free carriers are generated within, and the semiconductor transitions from a dielectric to a conductor within the photoactive, or exposed, region. Solid-state plasma generated by the photoconductive effect has shown promise as a microwave switching, phase shifting, tuning, and radiating technology. The advantages of solid-state plasma in microwave applications, beyond integration and reliability, include high power handling, low insertion loss, high linearity, and fast switching times.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The embodiments may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views.

[0005] FIG. 1 illustrates a first example of an antenna system.

[0006] FIG. 2 illustrates an example of a radiator for a system.

[0007] FIG. 3A-D illustrates examples of photoactivating a radiator with various numbers of lights.

[0008] FIG. 4 illustrates a second example of an antenna system.

[0009] FIG. 5A-C illustrates examples of antenna and array patterns provided by independently controlling radiators in the plasma pixel array.

[0010] FIG. 6 illustrates a cross section of an antenna system.

[0011] FIG. 7 illustrates a third example of a system with a radiator pixel array where not every radiator segment and radiator pixel is directly connected to an RF feed network.DETAILED DESCRIPTION

[0012] While having many advantages, plasma antennas typically use gas discharge inside dielectric tubes made from plastic or glass to generate the conductive region. Because of this, plasma antennas generally suffer difficulties in their integration with widely available low-cost semiconductor processes.

[0013] Solid-state plasma generated by the photoconductive effect has shown promise as a microwave switching, phase shifting, tuning, and radiating technology. The advantages of solid-state plasma in microwave applications, beyond integration and reliability, include high power handling, low insertion loss, high linearity, and fast switching times. In addition, while practical conductivity values for gas discharge tubes are in the tens of S / m, photogenerated solid-state plasma can achieve conductivities at least two orders of magnitude higher. Several antenna configurations using solid- state plasma have been shown in the literature. In general, most implementations use photoconductive switches to connect or disturb different metal elements of the antenna to provide reconfiguration of the resonance frequency or radiation profile. In one example, a monopole antenna used an optoelectronic switch located between two metal segments allowing reconfiguration of the resonance frequency by effectively changing the length of the monopole (J. L. Freeman, B. J. Lamberty, and G. S. Andrews, “Optoelectronically reconfigurable monopole antenna,” Electron. Lett., vol. 28, no. 16, pp. 1502-1503, Jul. 1992.). Similar concepts using a dipole or circular patch and ring have also been reported. Photoconductive silicon switches connected to different copper stub lengths loading a patch antenna were used to disrupt its fieldprofile and shift its resonance frequency. Slots have also been inserted on either side of a patch antenna covered by a silicon superstrate and tuned based on optical excitation, causing changes to nulls within the radiation pattern and reconfiguring its profile.

[0014] The examples above use fully metal antennas and are thus not suitable for low radar cross section applications. One of the first investigations into the use of photogenerated solid-state plasma as the actual radiating element of a plasma antenna was presented in (R. N. Edwards, W. C. Nunnally, W. D. Dickson, B. C. Miller, and L. K. Robinette, “Investigation of photoconductive silicon as a reconfigurable antenna,” Proc. SPIE, vol. 1918, pp. 344-353, Jul. 1993). Light from a pulsed Nd:Glass laser source was shined through a metal mask generating a bowtie antenna pattern on a 100-mm silicon wafer. The silicon plasma antenna achieved between 45% and 50% of the broadside radiated power compared to an equivalent copper bowtie antenna operating from 1 .4 to 2.1 GHz. However, the assembled structure was large, complex, and suffered diffusion problems in the feed contacts. An improvement in the optical delivery system for more uniform and efficient illumination of the bowtie pattern was reported in D. Liu et al., “Structurally embedded photoconductive silicon bowtie antenna,” IEEE Photon. Technol. Lett., vol. 10, no. 5, pp. 716-718, May 1998. However, the broadside radiated power dropped to 32% compared to copper. Similarly, as reported in C. D. Gamlath, M. A. Collett, and M. J. Cryan, “Investigation of novel architectures for tunable antennas based on optically generated plasmas,” in Proc. 45th Eur. Microw. Conf. Proc. (EuMC). Paris, France, Sep. 2015, pp. 1144— 1147, a vertical-cavity surface-emitting laser (VCSEL) was shined on a silicon wafer attached to a printed circuit board (PCB) substrate generating a photoconductive patch-shaped antenna. The device achieved a maximum measured gain of -8 d Bi and an ON / OFF ratio of 17 dB at 17.65 GHz.

[0015] The system and methods described herein provide numerous technical advantages over existing approaches. By way of example the system described herein provides a simplified, integrated, low-cost, widely tunable, high power, high linearity, and high speed implementation of a photogenerated solid-state plasma antenna on a PCB with significant radiation efficiency and realized gain. The performance objective is to maximize both the ON-state gain and ON / OFF ratio as an effective radiator in the ON-state (or photoconductive state) while making the antenna elementindistinguishable from typical substrates in the OFF-state (or dielectric state). Various experimentation was performed to achieve an ON-state broadside realized gain of -2.6 d Bi at 16.9 GHz, ON / OFF ratio greater than 17.8 dB from 14.2 to 20 GHz, while radiating between 43%-62% of the power compared to an equivalent fully copper monopole antenna. In addition, by using adjacent light sources to excite individual photoconductive regions within a single antenna element, or an array of single radiators that are each excited by individual lights and are coupled to adjacent radiators, the system can also change the shape and / or effective size of the radiator (or effective radiator made up of smaller single radiators), enabling various antenna and array shapes and / or patterns to be generated for complete custom reconfiguration of the radiation pattern, frequency, and bandwidth of an antenna or array system. Furthermore, only the necessary antenna or array pattern can be turned ON to complete a specific transmission or reception objective, and once complete, can be quickly turned OFF, significantly reducing the overall radar cross section of the system. The overall shape of the antenna can also be adjusted for optimal impedance matching to fixed RF feed locations.

[0016] FIG. 1 illustrates an example of an antenna system. The system may include a radiator 102. The radiator 102 may be an antenna. At least a portion of the antenna may transition from a conductor to a dielectric in response to exposure to photo illumination.

[0017] FIG. 2 illustrates an example of the radiator 102 that is shown in the cross section A-A’ in FIG. 1 . The radiator 102 may include a chiplet having a photoconductive region 202. The photoconductive region may include, for example, a semiconductor material capable of providing a photogenerated solid-state plasma when exposed to light. Alternatively or in addition, the photoconductive region may have other materials capable of transitioning from dielectric to conductor via photoactivation including, for example, silicon, germanium, gallium arsenide, gallium nitride, silicon germanium, silicon carbide, indium phosphide, and / or gallium phosphide. In some examples, the radiator may include a contact(s) 204, 206 for coupling the radiator to a PCB and / or for sending and receiving RF signals. The contacts 204, 206 may be copper or some other suitable conductor for microelectronics. An adhesion layer may be used between the radiator and the contacts for improved adhesion of the contact to the semicondcutor, coupling, or ohmic contact. The location of the contacts 204, 206, orwhether they are used at all, may vary depending on the implementation. In some examples, an optical anti-reflection coating 203 (i.e. silicon nitride) may be placed on the surface of the radiator between the radiator and the light source to improve the transmission of light from the light source into the radiator.

[0018] The dimensions of the radiator may also vary. FIG 2 shows an elongated radiator for a monopole antenna. In other examples, the radiator may take other shapes. The thickness T of the radiator may be selected to yield a high photoconductivity within the silicon region while minimizing the required optical power incident on the silicon to do so. It may also be chosen so that it is on the order of a skin depth at the chosen RF input / output operating frequency.

[0019] Referring back to FIG. 1 , the system 100 may further include an RF feed network 104. By way of example, the radiator 102 may couple with the RF feed network 104. The RF feed network may include conductors, lead lines, circuitry, and other components which provide / receive RF signals to / from the radiator 102. Signals may be sent or received to the radiator 102 depending on information being transmitted or received. Thus, the radiator 102 is capable of sending, receiving, and / or transceiving.

[0020] The system 100 may further include a light source 106. The light source 106 may include, for example, one or more light. The light(s) may be a light emitting diode (LED), micro-LED, optical fiber, vertical-cavity surface-emitting laser (VCSEL), laser diode, or any other suitable light emitting component. The light source 106 may be directed at the photoconductive region 202 (see FIG. 2) of the radiator. Exciting the light may cause at least a portion of the radiator 102 to transition from a dielectric to a conductor.

[0021] The light source 106 may have multiple lights, as illustrated in FIG 1. Each of the lights may be independently controlled. Exciting the lights may cause corresponding portions of the radiator 102 to transition from a dielectric to a conductor. The RF feed network 104 may cause the photoconductive region that is photoactivated to emit electromagnetic waves. Alternatively or in addition, the photoconductive region may become excited under electromagnetic exposure and provide the RF feed network 104 with signals received via the radiator 102.

[0022] The RF feed network 104 and radiator 102 may be attached to a substrate 108, such as a PCB. The substrate 108 may include a gap or hole which receives thelight source. In other words, the light source may be embedded in, extend through, and / or shine through a hole in the substrate 106. Alternatively, the substrate may be transparent at the wavelength of the light source, allowing the light to transmit through the substrate without a hole or opening in the substrate. The radiator 102 may be positioned over the light source such that the light source illuminates the photoconductive region of the radiator 102 when the light source is excited.

[0023] FIG. 3A-D illustrates examples of photoactivating a radiator with various numbers of lights. The light source may include multiple lights aligned sequentially, or in other patterns as described further below. In the sequential examples shown in FIGs 3A-D, the lights may be sequentially excited to vary the operating length of the radiator (and thereby change the wavelength of the electromagnetic waves sent and / or received).

[0024] Referring to FIG. 3A, a first light is excited causing a first portion of the radiator to transition from a dielectric to a conductor. The first portion of the radiator may be in affected by the RF feed network. For example, the first portion may contact the RF feed network or be electromagnetically influenced by the RF feed network. In FIG. 3B, a second light is excited causing a second portion of the radiator to transition to a conductor. In FIG. 3C, a third light is excited causing a third portion of the radiator to transition to a conductor. And in FIG. 3D, a fourth light is excited causing a fourth portion of the radiator to transition to a conductor. In other examples, additional or alternative numbers of lights and arrangements of lights are possible.

[0025] The system shown in FIG. 1 can be implemented in many ways. In one example, the layout of the radiator may include a photogenerated silicon (Si) plasma monopole antenna. A monopole antenna was chosen in various experimentation for its simple analysis and design, compact size, and many applications. The A / 4 radiating element of the monopole is formed by a radiator chiplet mounted onto a copper feed network patterned on a PCB substrate. The radiator chiplet is placed across a large gap between the antenna feed and a copper mounting pad on the substrate. When Si is excited by light with photon energy (hv) greater than its bandgap (Eg = 1.12 eV), a solid-state plasma of free carriers are generated within, and the chiplet transitions from a dielectric to a conductor within the photoactive, or exposed, region. An opening in the substrate beneath the radiator allows four optical fibers to excite Si and generate photoconductivity. The optical fibers themselves are essentially transparent to the EMenergy around the antenna, a clear advantage over PIN diode-based implementations. Thus, when the radiator is exposed to light, the monopole is conductive, and the antenna is in its radiating, or ON-state, and when the light is turned OFF, the monopole is a dielectric, and the antenna is in its nonradiating, or OFF-state.

[0026] The radiator may be formed by a piece of undoped high-resistivity silicon (HRS). Copper pads are deposited and patterned on its backside to aid in its attachment to the PCB using solder paste. The antenna feed network may be designed on a 20-mil thick Rogers DiClad 880 substrate with £r= 2.17, tan 5 = 9 x 10-4, and 35-pm-thick copper. An RF connector (not shown) may be connected to the PCB to allow for the input / output of RF signals with the antenna. Four optical fibers (made from quartz glass with £r = 3.8, tan 5 = 7.5x10~4) may be inserted underneath the radiator. An optical anti-reflection coating, for example a thin film made of silicon nitride, may be placed on the surface of the radiator between the radiator and the optical fibers, so as to improve the transmission of light from the optical fibers into the radiator.

[0027] It is noted that the entire length of the radiator may not be photoconductive. While the copper mounting pad provides approximately one-third of the monopole, its primary function is to help attach the radiator chiplet to the PCB and hold it in place in some examples.

[0028] FIG. 4 illustrates a second example of an antenna system 100. The system may include multiple radiators arranged in a pixel array. As described herein, a photoconductive region of a radiator that is activated by a single light source may be referred to as a pixel, or radiator pixel. In some examples, the system may be arranged such that each radiator is one pixel. Alternatively, a radiator may include multiple pixels (in other words each radiator may have multiple portions that are photoconductive and activated by corresponding light sources).

[0029] In some examples, a radiator may be physically segmented from an adjacent radiator. In some examples, a gap 402 may be positioned between adjacent radiators and each adjacent radiator may electromagnetically influence the other when it is photoactivated. Alternatively, adjacent radiators segmented by a gap may be directly coupled with each other using a metal contact or photoconductive region between each adjacent pixel. Alternatively, adjacent radiators may be segmented by a groove or slotted region between pixels to provide some segmentation but also somedirect connection. Alternatively, each radiator may not be physically segmented from an adjacent radiator pixel, and the radiator may be a sheet of photoconductive region in which smaller individual pixel regions are each excited by an individual light source. As described herein, a radiator segment refers to a radiator which has been segmented from other radiators by a gap, groove, or some form of coupling.

[0030] The radiators may have a photosensitive region which may be optically activated to transition the radiators from a dielectric to a conductor. Thus, the each of the radiators may be independently controlled via a light source to establish desired radiation patterns, frequency, and polarization.

[0031] With the light source of a pixel off, the pixel is a dielectric, and the pixel is in its non-radiative OFF-state. When the light source is turned on, the pixel becomes photoconductive, and the pixel switches to its radiative ON-state. This enables complete customization of the entire array based on individual pixels switching ON or OFF.

[0032] FIG. 5A-C illustrates examples of antenna system with various antenna and array patterns provided by independently controlling pixels in the plasma pixel array. Various antenna and array patterns are chosen such as to realize different radiation patterns for transmission or reception of EM signals. The dark squares represent radiator pixels in the ON-state (radiative state or photoconductive state), and light squares representing radiator pixels in the OFF-state (non-radiative state or dielectric state). Referring to FIG. 5A, a group of adjacent radiator pixels may be activated to form an antenna 502, which is essentially a larger radiator. Multiple antennas are included in the array to form an antenna array pattern. As illustrated in FIG. 5A, the antenna array pattern includes groups for 4x4 radiators in the ON state separated by groups of 4x4 radiators in the OFF state.

[0033] Referring to FIG. 5B, the antennas may have various shapes, depending on the radiator pixels that are activated. The purpose of the radiator pixels is to allow the formation of different antenna and array shapes or patterns, basically whatever patterns are desirable, which can then be turned off and the conductivity disappears.

[0034] Referring to FIG. 5C, the antennas in this array consist of single radiator pixels in the on state, separated by pixels in the off state. The radiator pixels can be physically be made smaller or larger. Smaller pixel size gives more shape and pattern resolution control, larger pixel size less so.

[0035] FIG. 6 illustrates a side view of an antenna system 100. The side view shows the A-A’ cross section for one radiator and underlying layers shown in FIG. 4.

[0036] The radiator 102 may be substantially planer, having a top surface and a bottom surface. The radiator 102 may include a photoconductive region 202 configured to transition from a dialectic to a conductor in response being photoactivated. In addition, the radiator 102 may include a conductive lead 204. In the example illustrated in FIG. 6, the conductive lead 204 includes a copper plate centrally positioned on a bottom surface of the radiator. The photoconductive region 202 of the radiator may be in the area(s) adjacent to and / or surrounding the conductive lead 204.

[0037] The system 100 may include one or more light source directed at the radiator. For example, the light sources may emit light toward a bottom side of the radiator, causing a portion of the photoconductive region to change from a dielectric to a conductor. In some examples, multiple lights 602 may be utilized per radiator. The lights may be arranged in any manner such that they extend away from the RF signal source sequentially. For example, a first light may be positioned near the conductive lead. A second light source may be positioned radially outward and adjacent to the first light source. Thus, illuminating both the first and second light may cause the conducive area of the radiator to increase.

[0038] The system 100 may include multiple layers to provide the RF signals and photoactivation to the radiators. While one radiator is shown in FIG, 6, the layers may span across multiple radiators in the plasma pixel array.

[0039] The system 100 may include a driver layer 604. The driver layer 604 may include RF input / output circuitry and / or optical power / control circuitry. By way of example, the driver layer may include integrated circuits, such as RF System on a Chip (RFSoC) and / or RF beamformers. The driver layer may further include integrated circuitry to cause the light source(s) to control which radiators are activated.

[0040] The system 100 may include optical lead lines 606 for optical control signals and lead lines for RF signals 608. It should be appreciated that the lead lines for optical control signals 606 and the lead lines 608 for RF signals may extend through multiple layers of the system. The lead lines, and intervening circuity, and ground plane for the RF signals may be collectively referred to an RF feed network. The lead lines, andintervening circuity, for the optical control signals may be referred to as the optical control network.

[0041] The driver layer 604 may connect to these networks to send / receive RF signals and perform optical control. In some examples, the system may include a routing layer 610. The routing layer 610 may provide the bulk of the routing for the RF feed network and / or optical control network.

[0042] The system 100 may include a light source layer 612. The light source layer 612 may include the lights that are emitted toward the radiators. Examples of various lights that may be used were previously discussed and may include without limitation, LEDs, optical fibers or the like. For example, the light source layer may include a GaAs-based LED module or some other light module.

[0043] The system 100 may include a lens layer 614. The lens layer 614 may focus light from the light source onto the radiator 102. By way of example, the lens layer 614 may include GRIN-based microlenses and / or a microlens array.

[0044] The system 100 may include a PCB layer 616. The PCB layer 616 may receive the radiator and the layers below the radiator. The PCB may provide a cavity substrate and a ground plane for the radiator. In some examples, the PCB layer may include holes or gaps in which light from light source layer passes though. Alternatively or in addition, the light sources and / or lenses may extend into the holes of the PCB layer. In other examples, PCB layer 616, other layers between the light source layer 612, may be transparent or have transparent portions, rendering an opening unnecessary. In some examples, the ground plane may include a transparent metal, such as indium tin oxide (ITO) that allows optical light to pass through but behaves as a frequency for RF signals.

[0045] It should be appreciated that the system 100 may be implemented in many ways. The system 100 may be implemented with additional, different, or fewer components than illustrated. Each component may include additional, different, or fewer components. The architectures of the antenna system shown in the figures are just two possible architecture and may be implemented in different ways with additional or fewer components.

[0046] FIG. 7 illustrates a third example of system 100 with a radiator pixel array 700 where not every radiator segment and radiator pixel is directly connected to theRF feed network. As illustrated in FIG. 7, a first radiator segment 702 may be directly connected to the RF feed network 608 and a second radiator segment 704 may not. When a first light source 706 for a first radiator segment 702 and second light source 708 for an adjacent second radiator segment 704 are activated, the adjacent conductive regions of the first and second radiator segment may become activated and the two radiator segments may become conductively coupled.

[0047] A similar affect can be described with radiator pixels. A first radiator pixel 710 may be adjacent to the RF feed network 608. A second radiator pixel 712 may be isolated from the RF feed network 608. When the first light source 710 that defines the first radiator pixel 710 is activated and the second light source 708 that defines the second radiator pixel 712 is activated, the second radiator pixel may be influenced by the RF feed network 608.

[0048] A second action may be said to be "in response to" a first action independent of whether the second action results directly or indirectly from the first action. The second action may occur at a substantially later time than the first action and still be in response to the first action. Similarly, the second action may be said to be in response to the first action even if intervening actions take place between the first action and the second action, and even if one or more of the intervening actions directly cause the second action to be performed. For example, a second action may be in response to a first action if the first action sets a flag and a third action later initiates the second action whenever the flag is set.

[0049] To clarify the use of and to hereby provide notice to the public, the phrases "at least one of , , ... and <N>" or "at least one of , , ... <N>, or combinations thereof" or ", , ... and / or <N>" are defined by the Applicant in the broadest sense, superseding any other implied definitions hereinbefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean one or more elements selected from the group comprising A, B, ... and N. In other words, the phrases mean any combination of one or more of the elements A, B, ... or N including any one element alone or the one element in combination with one or more of the other elements which may also include, in combination, additional elements not listed.

[0050] While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementationsare possible. Accordingly, the embodiments described herein are examples, not the only possible embodiments and implementations.

Claims

CLAIMSWhat is claimed is:1 . A system, comprising: a radiator comprising a photoconductive region configured to transition from a dielectric to a conductor in response to being photoactivated; a light source directed at the photoconductive region, the light source configured to selectively activate the photoconductive region of the radiator; and a RF feed network configured to cause the photoconductive region that is photoactivated to transmit electromagnetic waves.

2. The system of claim 2, wherein the photoconductive region comprises silicon, germanium, gallium arsenide, gallium nitride, silicon germanium, silicon carbide, indium phosphide, or gallium phosphide.

3. The system of claim 1 , further comprising a substrate, wherein the radiator is coupled to the substrate and extends across a gap in the substrate, wherein the light source is configured to emit light from the gap.

4. The system of claim 1 , further comprising a substrate where at least a portion of the substrate is transparent, wherein the radiator is coupled to the substrate, wherein the light source is configured to emit light though the transparent portion of the substrate.

5. The system of claim 1 , wherein the light source comprises a light emitting diode, an optical fiber, a micro-light emitting diode, a vertical-cavity surface-emitter laser, a laser diode, or a combination thereof.

6. The system of claim 1 , wherein the light source comprises a plurality of light sources, wherein each of the light sources are directed at a different portion of the photoconductive region.

7. The system of claim 6, wherein varying the plurality of lights sources that are activated causes a wavelength of electromagnetic waves emitted from the radiator to change.

8. A system comprising: a radiator comprising a photoconductive region configured to transition from a dielectric to a conductor in response being photoactivated; a plurality of light sources directed at the radiator where each of the light sources activates a corresponding portion of the photoconductive region to form an array of radiator pixels; an optical control network configured to cause at least one of the lights sources to emit light onto the radiator and photoactivate at least one of the radiator pixels; and an RF feed network configured to cause at least one of the radiator pixels of to emit or receive electromagnetic waves.

9. The system of claim 8, wherein the photoconductive region comprises silicon, germanium, gallium arsenide, gallium nitride, silicon germanium, silicon carbide, indium phosphide, or gallium phosphide.

10. The system of claim 8, wherein the light sources comprises a light emitting diode, a micro-light emitting diode, a vertical-cavity surface-emitter laser, a laser diode, or a combination thereof.1 1 . The system of claim 8, wherein a first radiator pixel is directly connected to the RF feed network while a second radiator pixel is only connected when the first radiator pixel is photoactivated.

12. The system of claim 8, the radiator comprises a plurality of radiators segmented by a gap.

13. The system of claim 8, further comprising RF control circuitry and optical control circuitry, where in the RF control circuitry is configured to transmit RF signals to the radiator pixels via the RF feed network.

14. The system of claim 8 further comprising optical control circuitry, wherein the optical control circuitry is configured to cause a subset of adjacent radiator pixels in the array of radiator pixels to become conductive according to a pattern.

15. The system of claim 8, further comprising a lens configured to focus light from the light sources onto the photoactivate regions of the radiator pixels.

16. The system of claim 8, wherein the at least one of the radiator pixels includes an anti-reflective coating.

17. A system, comprising: a radiator comprising a photoconductive region configured to transition from a dielectric to a conductor in response being photoactivated; a light source directed at the photoconductive region, the light source configured to selectively activate the photoconductive region of the radiator; and a RF feed network configured to cause the photoconductive region that is photoactivated to receive electromagnetic waves.

18. The system of claim 17, wherein the photoconductive region comprises silicon, germanium, gallium arsenide, gallium nitride, silicon germanium, silicon carbide, indium phosphide, or gallium phosphide.

19. The system of claim 17, wherein the light source comprises a light emitting diode, an optical fiber, a micro-light emitting diode, a vertical-cavity surface-emitter laser, a laser diode, or a combination thereof.

20. The system of claim 17, wherein the light source comprises a plurality of light sources, wherein each of the light sources are directed at a different portion of the photoconductive region.

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