Switch based on phase change material

Abstract

Switch based on a phase change material The present description relates to a switch (C1) based on a phase change material comprising: – a region (160) made of said phase change material connecting first and second conduction electrodes (140P, 140C) of the switch; and – a waveguide (164) comprising a first end facing a face of the region (160) made of said phase change material and a second end, opposite the first end, intended to be illuminated by a laser source (LS). Figure for abstract: Fig. 6

Description

Title of the invention: Switch based on a phase change material Technical field

[0001] The present description relates generally to electronic devices and in particular to devices of the reconfigurable electromagnetic surface type. The present application relates more particularly to the field of radio antennas with a transmitting array (transmitarray antenna) and radio antennas with a reflector array (reflectarray antenna). Prior art

[0002] Among the various existing radio communication antenna technologies, radio antennas known as "transmitter array" antennas are known in particular. These antennas generally comprise several elementary cells each comprising a first antenna element irradiated by an electromagnetic field emitted by one or more sources, a second antenna element transmitting a modified signal to the outside of the antenna and a coupling and phase shift element between the first and second antenna elements.

[0003] Radio antennas known as "reflector array" antennas are also known. These antennas generally comprise several elementary cells, each comprising an antenna element irradiated by an electromagnetic field emitted by one or more sources, a reflector element, for example a ground plane, reflecting a modified signal towards the outside of the antenna and a coupling element between the antenna element and the reflector element. Unlike the elementary cells of transmitting array antennas, which transmit a radio signal in a direction opposite to the source(s) irradiating their first antenna element, the elementary cells of reflector array antennas reflect a radio signal towards the source(s) irradiating their antenna element.

[0004] For certain applications, for example such as satellite communication ("satellite communication" or "SatCom" in English), or very high speed and short or medium range communication applications, for example at frequencies above 80 GHz, it would be desirable to have reconfigurable transmitter array antennas and reflector array antennas making it possible to dynamically modify the phase of the radiated wave. Summary of the invention

[0005] There is a need to improve transmitting array antennas and existing reflector network.

[0006] An embodiment overcomes all or part of the disadvantages of known transmitting array antennas and reflecting array antennas. An object of an embodiment consists more particularly in allowing electronic phase control in a frequency range of, for example, between 80 and 350 GHz, corresponding to millimeter wavelengths, and in providing switches whose polarization results in reduced electrical consumption.

[0007] For this, one embodiment provides a switch based on a phase change material comprising: - a region of said phase change material connecting first and second conduction electrodes of the switch; and - a waveguide comprising a first end facing a face of the region made of said phase-change material and a second end, opposite the first end, intended to be illuminated by a laser source.

[0008] According to one embodiment, the waveguide comprises a central region of silicon nitride surrounded by a peripheral region of silicon dioxide.

[0009] According to one embodiment, the phase change material is a chalcogenide material.

[0010] According to one embodiment, the first and second conduction electrodes are part of an antenna element of a transmitting array cell or reflecting array cell.

[0011] According to one embodiment, the first and second conduction electrodes are on and in contact with one face of a substrate.

[0012] According to one embodiment, the first and second conduction electrodes are on and in contact with one face of an electrically insulating layer coating a substrate.

[0013] According to one embodiment, at least one end, among the first and second ends of the waveguide, makes it possible to transmit or receive radiation in a direction orthogonal to a direction of propagation of the radiation inside the waveguide.

[0014] According to one embodiment, said end of the waveguide has a tapered shape.

[0015] According to one embodiment, at least one end, among the first and second ends of the waveguide, makes it possible to transmit or receive radiation in a direction parallel to the direction of propagation of the radiation inside the waveguide.

[0016] Another embodiment provides a transmitter network or reflector network cell comprising at least one switch as defined above.

[0017] Another embodiment provides a transmitter network or reflector network including: - a plurality of cells as defined above; - one or more laser sources; and - a control circuit for the laser source(s).

[0018] According to one embodiment, each laser source is part of the same chip as each switch with which it is associated.

[0019] According to one embodiment, each laser source is part of a chip different from that of which each switch to which it is associated is part, the laser source being connected to the waveguide of said switch by an optical fiber.

[0020] Another embodiment provides an antenna comprising a transmitting array or a reflecting array as defined above and at least one source configured to irradiate one face of the array. Brief description of the drawings

[0021] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0022] [Fig.l] is a schematic and partial side view of an example of a transmitting array antenna of the type to which, by way of example, the described embodiments apply;

[0023] [Fig.2] is a schematic and partial perspective view of an elementary cell of the transmitting network of the antenna of [Fig.l] according to one embodiment;

[0024] [Fig.3] is a schematic and partial top view of a first antenna element of the elementary cell of [Fig.2];

[0025] [Fig.4] is a schematic and partial top view of a part of the elementary cell of [Fig.2];

[0026] [Fig.5] is a schematic and partial top view of a second antenna element of the elementary cell of [Fig.2];

[0027] [Fig.6] is a schematic and partial sectional view of a switch based on a phase change material with integrated optical control according to one embodiment;

[0028] [Fig.7] is a schematic and partial sectional view of another switch based on a phase change material with integrated optical control according to one embodiment;

[0029] [Fig.8] is a perspective view of an output surface of a waveguide according to one embodiment; and

[0030] [Fig.9] is a perspective view of an output surface of a waveguide according to another embodiment. Description of the embodiments

[0031] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0032] For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been shown and are detailed. In particular, embodiments of a cell for a transmitting array antenna and embodiments of a cell for a reflecting array antenna will be described below. The structure and operation of the primary source(s) of the antenna, intended to irradiate the transmitting array or the reflecting array, will however not be detailed, the embodiments described being compatible with all or most of the known primary irradiation sources for transmitting array or reflecting array antennas. By way of example, each primary source is adapted to produce a beam of generally conical shape irradiating all or part of the transmitting array or the reflecting array in near-field or far-field conditions. Each primary source comprises, for example, a horn antenna.For example, the central axis of each primary source is substantially orthogonal to the mean plane of the array or in an offset configuration (displaced from the central axis and rotated so as to illuminate the surface of the reflector array. This illumination is typical in the case of a reflector array to reduce the blocking phenomenon.

[0033] Furthermore, the manufacturing methods of the transmitter networks and the reflector networks described will not be detailed, the production of the structures described being within the reach of the person skilled in the art from the indications of the present description.

[0034] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0035] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0036] Unless otherwise specified, the expressions “about”, “approximately”, “substantially”, and “of the order of” mean to within 10%, preferably to within 5%.

[0037] [Fig.l] is a schematic and partial side view of an example of a transmitting array antenna 100 of the type to which, by way of example, the described embodiments apply.

[0038] The antenna 100 typically comprises one or more primary sources 101 (a single source 101, in the example shown) irradiating a transmitting network 103. The source 101 may have any polarization, for example linear or circular. The network 103 comprises a plurality of elementary cells 105, for example arranged in a matrix according to rows and columns. Each cell 105 typically comprises a first antenna element 105a, located on the side of a first face of the network 103 arranged opposite the primary source 101, and a second antenna element 105b, located on the side of a second face of the network 103 opposite the first face. The second face of the network 103 is for example turned towards an emission medium of the antenna 100.

[0039] Each cell 105 is capable, in transmission, of receiving electromagnetic radiation on its first antenna element 105a and of re-emitting this radiation from its second antenna element 105b, for example by introducing a known phase shift ¢). In reception, each cell 105 is capable of receiving electromagnetic radiation on its second antenna element 105b and of re-emitting this radiation from its first antenna element 105a, in the direction of the source 101, with the same phase shift ¢. The radiation re-emitted by the first antenna element 105a is for example focused on the source 101.

[0040] The characteristics of the beam produced by the antenna 100, in particular its shape (or template) and its maximum emission direction (or pointing direction), depend on the values ​​of the phase shifts respectively introduced by the different cells 105 of the network 103.

[0041] Transmitting array antennas have the advantage, among other things, of being energy efficient and relatively simple, inexpensive and compact. This is due in particular to the fact that the transmitting arrays can be produced using planar technology, generally on a printed circuit.

[0042] We are more particularly interested here in antennas with a reconfigurable transmitter array 103. The transmitter array 103 is said to be reconfigurable when the elementary cells 105 are electronically controllable individually to modify their phase shift value ¢, which makes it possible to dynamically modify the characteristics of the beam generated by the antenna, and in particular to modify its pointing direction without mechanically moving the antenna or a part of the antenna by means of a motorized element.

[0043] [Fig.2] is a schematic and partial perspective view of one of the elementary cells 105 of the transmitter network 103 of the antenna 100 of [Fig.l] according to a embodiment.

[0044] According to this embodiment, the first antenna element 105a of the elementary cell 105 comprises a patch antenna 110 adapted to capture the electromagnetic radiation emitted by the source 101 and the second antenna element 105b comprises another patch antenna 112 adapted to emit, towards the outside of the antenna 100, a phase-shifted signal. In the example shown, the elementary cell 105 further comprises a ground plane 114 interposed between the patch antennas 110 and 112.

[0045] The antenna 110, the ground plane 114 and the antenna 112 are for example respectively formed in three successive metallization levels, superimposed and separated from each other by dielectric layers, for example made of quartz. By way of example, the ground plane 114 is separated from each of the antennas 110 and 112 by a thickness of dielectric material of the order of 200 μm.

[0046] In the example shown, a central conductive via 116 connects the antenna 110 to the antenna 112. More specifically, in the orientation of [Fig. 2], the via 116 has a lower end in contact with an upper face of the antenna 110 and an upper end in contact with a lower face of the antenna 112. The central conductive via 116 is electrically isolated from the ground plane 114. In the example shown, the ground plane 114 has a circular orifice having a diameter greater than that of the via 116, thus allowing the via 116 to pass through the ground plane 114 without the via 116 being in contact with the ground plane 114. For example, the central conductive via 116 has a diameter equal to approximately 80 μm.

[0047] Furthermore, in this example, lateral conductive vias 118, located on either side of the central conductive via 116, connect the antenna 110 to the ground plane 114. More precisely, in the orientation of [Fig. 2], each via 118 has a lower end in contact with the upper face of the antenna 110 and an upper end in contact with a lower face of the ground plane 114. As a variant, in the case of optical control, these vias can be omitted since there is then no voltage to control.

[0048] [Fig. 3] is a schematic and partial top view of the first antenna element 105a of the elementary cell 105 of [Fig. 2]. [Fig. 3] illustrates more precisely the patch antenna 110 of the elementary cell 105.

[0049] In the example shown, the patch antenna 110 comprises a conductive plane 120 of substantially square shape inside which is formed a U-shaped slot 122, or groove. The slot 122 is for example substantially centered relative to the conductive plane 120. In this example, the central conductive via 116 is in contact with a zone of the conductive plane 120 located between the two branches of the U formed by the slot 122. The via 116 is for example substantially centered relative to the plane driver 120.

[0050] Furthermore, in the example illustrated in [Fig. 3], the lateral conductive vias 118 are located on either side of the slot 122. More precisely, each via 118 is for example connected to a zone of the conductive plane 120 located outside the U formed by the slot 122 and along one of the vertical branches of the U. In other words, in this example, the zone of the conductive plane 120 where each lateral via 118 is connected is separated from the zone of the conductive plane 120 where the central via 116 is connected by one of the vertical branches of the U formed by the slot 122. Here again, as a variant, in the case of optical control, these vias can be omitted since there is then no voltage to control.

[0051] By way of example, the square formed by the conductive plane 120 has a side of the order of 0.44 mm, the vertical branches and the horizontal branch of the U formed by the slot 122 each have a length of the order of 0.32 mm, and the slot 122 has a width equal to approximately 50 μm.

[0052] [Fig. 4] is a schematic and partial top view of a portion of the elementary cell 105 of [Fig. 2]. [Fig. 4] illustrates more precisely the ground plane 114 located between the first and second antenna elements 105a, 105b.

[0053] In the example shown, the ground plane 114 comprises a conductive plane 130 of substantially square shape. In this example, the central conductive via 116 passes through the ground plane 114 approximately at its center. The via 116 is isolated from the conductive plane 130 by an annular, or crown-shaped, opening 132 formed in the conductive plane 130 around the via 116. By way of example, the square formed by the conductive plane 130 has a side of the order of 1 mm.

[0054] In this example, the side of the square formed by the conductive plane 130 substantially defines the external dimensions of the elementary cell 105 of the transmitter network 103.

[0055] The ground plane 114 fulfills an electromagnetic shielding function between the antenna 110 and the antenna 112 of the cell 105.

[0056] In the example illustrated in [Fig.4], the lateral conductive vias 118 contact the lower face of the conductive plane 130 in areas diametrically opposite relative to the central conductive via 116. In this example, the vias 116 and 118 are located on the same straight line parallel to one of the sides of the conductive plane 130. Furthermore, the vias 118 are equidistant from the via 116. Here again, as a variant, in the case of optical control, these vias can be omitted since there is then no voltage to control.

[0057] [Fig. 5] is a schematic and partial top view of the second antenna element 105b of the elementary cell 105 of [Fig. 2]. [Fig. 5] illustrates more precisely the patch antenna 112 of the elementary cell 105.

[0058] In the example shown, the antenna 112 comprises a four-sided conductive plane 140. The conductive plane 140 is, for example, more precisely rectangular in shape or, as in the example illustrated in [Fig.5], substantially square in shape.

[0059] In the illustrated example, the conductive plane 140 comprises an opening 142 separating a central region 140C of the conductive plane 140 from a peripheral region 140P of the conductive plane 140. In this example, the opening 142 has a substantially annular shape, for example a rectangular or square annular shape.

[0060] In the example shown, the central conductive via 116 is in contact with the central region 140C of the conductive plane 140. More precisely, in this example, the upper end of the via 116 is connected substantially to the center of a lower face of the region 140C. The central region 140C of the conductive plane 140, delimited laterally by the annular opening 142, constitutes for example an input terminal of the antenna 112.

[0061] The antenna 112 further comprises a first switching element C1 and a second switching element C2, each connecting the central region 140C to the peripheral region 140P of the conductive plane 140. More precisely, in the example illustrated in [Fig. 5], the first and second switching elements C1 and C2 contact the peripheral region 140P in areas diametrically opposite with respect to the central conductive via 116. In this example, the switching elements C1 and C2 and the conductive via 116 are located on the same straight line parallel to one of the sides of the conductive plane 140. In this example, the switch C1 is located substantially vertically to the horizontal branch of the U formed by the slot 122.

[0062] The switching elements C1 and C2 are controlled in opposition, that is to say so that, if one of the switches C1, C2 is on, the other switch C2, C1 is blocked. This allows the second antenna element 105b of the elementary cell 105 to switch between two phase states ¢, substantially equal to 0° and 180° in this example. The phase states 0° and 180° correspond respectively to the case where the switch C1 is blocked while the switch C2 is on, and to the case where the switch C1 is on while the switch C2 is blocked.

[0063] By way of example, the square formed by the conductive plane 140 has a side of the order of 0.44 mm, the sides of the square annular opening 142 each have a length of the order of 0.32 mm, and the opening 142 has a width equal to approximately 50 μm.

[0064] [Fig.6] is a schematic and partial sectional view of the switching element C1 of the second antenna element 105b of [Fig.5].

[0065] According to one embodiment, the switching element C1, or switch, is based on a phase change material. Phase change materials are materials which can alternate, under the effect of heat, between a crystalline phase and an amorphous phase, the amorphous phase having an electrical resistance greater than that of the crystalline phase. This phenomenon can in particular be taken advantage of to produce, as in the case of the second antenna element 105b, switches having blocked (amorphous phase) and passing (crystalline phase) states differentiated by a resistance across the phase change material.

[0066] In the example illustrated in [Fig. 6], a continuous region 160 made of a phase-change material is located on and in contact with the upper faces of the central 140C and peripheral 140P regions of the conductive plane 140. In this example, the regions 140C and 140P are disjoint and separated from each other by a distance DI of approximately 1 μm. The regions 140C and 140P are, for example, on and in contact with a face of a substrate 150 (the upper face of the substrate 150, in the orientation of [Fig. 6]). By way of example, the substrate 150 is a wafer or a piece of wafer made of a transparent material, for example glass, or of a semiconductor material, for example standard or highly resistive, for example silicon.

[0067] In the example shown, an electrically insulating region 162, for example made of silicon dioxide, laterally separates the central region 140C from the peripheral region 140P of the conductive plane 140. The region 162 has, for example, a thickness substantially equal to that of the conductive plane 140, for example equal to approximately 0.6 μm, and extends laterally between the regions 140C and 140P on and in contact with the upper face of the substrate 150. Although this has not been detailed in [Fig. 6], other electrically insulating regions coplanar with the region 162 may further extend laterally between the regions 140C and 140P as well as outside the region 140P. For example, the regions 140C and 140P may in practice be formed in the same electrically conductive layer.

[0068] The region 160 of phase-change material completely covers the upper face of the electrically insulating region 162 and extends laterally over and in contact with parts of the upper faces of the regions 140C and 140P adjoining the region 162. The regions 140C and 140P correspond, for example, to first and second electrodes of the switch C1, connected to each other by the region 160 of phase-change material. The region 160 has, for example, when viewed from above, a substantially rectangular shape of width D2 ([Fig. 6]) equal to approximately 3 μm and length (dimension measured in a direction orthogonal to the section plane of [Fig. 6]) equal to approximately 20 μm.

[0069] By way of example, region 160 is made of a so-called “chalcogenide” material, that is to say a material or an alloy comprising at least one chalcogen element, for example a material from the germanium telluride (GeTe) or germanium-antimony-tellurium (GeSbTe, also designated by the acronym “GST”) family.

[0070] According to one embodiment, the switch C1 further comprises a guide waveguide 164 comprising a first end facing a face of the region 160 made of phase-change material and a second end, opposite the first end, intended to be illuminated by a laser source LS. More precisely, in the example shown, the waveguide 164 covers the upper face of the region 160 and extends laterally up to the vertical plane of the laser source LS. The embodiments described are however not limited to this particular configuration. More generally, an optical coupler can be provided between the waveguide 164 and the region 160, the relative arrangement of the waveguide with respect to the region 160 depends on the design of the coupler. The waveguide 164 is a so-called “optical” waveguide, adapted to transmit the radiation emitted from the laser source LS to the phase change material of the region 160. By way of example, the waveguide 164 comprises a central region, or core, made of silicon nitride.The material is chosen so as to obtain an index contrast allowing the optical mode to be confined and guided.

[0071] In the example illustrated in [Fig.6], the structure located on the side of the upper face of the substrate 150, comprising the regions 140P, 140C, 160 and 162 and the waveguide 164, is coated with an electrically insulating layer 166. In this example, the layer 166 coats the upper face and the sides of the waveguide 164, as well as a part of the lower face of the waveguide 164 which is not in contact with the region 160. The layer 166 constitutes a peripheral region surrounding the central region of the waveguide 164. The material of the layer 166 has, for example, an optical index lower than that of the central region of the waveguide 164 and does not absorb optical radiation. For example, the layer 166 is made of silicon dioxide.

[0072] The waveguide 164 and the layer 166 are for example formed in thin insulation layers used for producing the antenna element 105b of the cell 105. This advantageously makes it possible to avoid the implementation of additional manufacturing steps to produce the waveguide 164 surrounded by the layer 166.

[0073] On the side of its end intended to be illuminated by the laser source LS, the waveguide 164 comprises for example an input coupling element 164b also called the input surface or structure of the waveguide 164. On the side of its end located opposite the region 160 made of phase-change material, the waveguide 164 may further comprise an output coupling element (not detailed in the figure), also called the output surface or structure of the waveguide 164. The input coupling element 164b may have a structure, for example a diffraction grating having a Bragg structure or any other coupling structure, making it possible to capture the radiation emitted by the laser source LS and to propagate this radiation to the output surface. The laser LS may emit a light wave vertically to the surface of the substrate.In this case, a coupling network allows the wave to be directed into the guide, for example as described in the article “Enabling . VCSEL-on-Silicon nitride photonic integrated circuits with micro-transfer-printing », J. Goyvaerts et al., Optica 2021, https: / / doi.org / 10.1364 / OPTICA.441636Z / . Alternatively, the LS laser can emit a longitudinal light wave (parallel to the substrate surface). In this case, an adiabatic coupler can bring the light into the waveguide 164, for example as described in the article “Heterogeneous III-V on Silicon nitride amplifiers and lasers via microtransfer printing”, C. Op de Beeck https: / / doi.org / 10.1364 / OPTICA.382989 / / .

[0074] Furthermore, the output surface of the waveguide 164 may have a structure enabling the radiation propagated from the input surface to be re-emitted towards the region 160 made of phase-change material. Although this has not been detailed in [Fig. 6], the output surface of the waveguide 164 may have a structure identical or similar to that of the input surface of the waveguide 164.

[0075] Generally speaking, the input and output surfaces respectively allow, in the example shown, to receive and transmit radiation in a direction orthogonal to the direction of propagation of the radiation inside the waveguide 164. As a variant, at least one surface, among the input and output surfaces of the waveguide 164, may have a structure allowing respectively to receive or transmit radiation in a direction parallel to the direction of propagation of the radiation inside the waveguide 164.

[0076] In the example shown, the laser source LS comprises an active region 170, or emissive region, intended to emit laser radiation. In this example, an interface layer 172 located on and in contact with the layer 166 is interposed between the layer 166 and the region 170. For example, the active region 170 of the laser source LS is based on krypton fluoride (KrF). As a variant, the region 170 may be made of a III-V semiconductor material.

[0077] The laser source LS is for example transferred onto the layer 166 by a technique called flip chip, for example by means of metal-metal bonding, for example by implementing a method of the type described in the publication by Y. Wang et al. entitled “Vertical-cavity surface-emitting laser flip-chip bonding to Silicon photonics chip”. As a variant, the laser source LS can be produced by a method called transfer printing, for example such as that described in the publication by C. Op de Beeck et al. entitled “Heterogeneous IILV on Silicon nitride amplifiers and lasers via microtransfer printing”, or by a method called direct bonding, for example such as that described in the publication by JM Rarmrez et al. entitled “Low-Threshold, High-Power On-Chip Tunable III-V / Si Lasers with Integrated Semiconductor Optical Amplifiers”.

[0078] The LS laser source can alternatively be produced on another support independent of this substrate. In this case the emitted optical mode will be focused in the waveguide by coupling onto the surface of the wafer using a coupling grating or onto the edge of the wafer ('butt coupling').

[0079] To switch the switch C1 from the off state to the on state, the region 160 is heated, for example, using the laser source LS, via the waveguide 164, to a temperature T1 and for a duration d1. The temperature T1 and the duration d1 are chosen so as to cause a phase change of the material of the region 160 from the amorphous phase to the crystalline phase. For example, the temperature T1 is higher than a crystallization temperature and lower than a melting temperature of the phase change material and the duration d1 is between 10 and 100 ns.

[0080] Conversely, to switch the switch C1 from the on state to the off state, the region 160 is heated, for example, using the laser source LS, via the waveguide 164, to a temperature T2, higher than the temperature T1, and for a duration d2, lower than the duration d1. The temperature T2 and the duration d2 are chosen so as to cause a phase change of the material of the region 160 from the crystalline phase to the amorphous phase. For example, the temperature T2 is higher than the melting temperature of the phase change material and the duration d2 is of the order of 10 ns.

[0081] By way of example, in a case where the laser source LS is based on krypton fluoride, radiation having a wavelength equal to approximately 248 nm is emitted by the laser source LS, for example in the form of pulses, to cause transitions of the material of the region 160 between the amorphous and crystalline phases. A pulse having a fluence of the order of 85 mJ.cm2 is for example used to obtain a transition of the material of the region 160 from the amorphous phase to the crystalline phase. Furthermore, another pulse having a fluence of the order of 185 mJ.cm2 is for example used to obtain a transition of the material of the region 160 from the crystalline phase to the amorphous phase.

[0082] The switch C2 has, for example, a structure, dimensions and operation similar to what has been described previously in relation to the switch CL.

[0083] Using the laser source LS associated with the waveguide 164 to control the switches C1 and C2 of the antenna element 105b has the advantage of reducing the number of electrically conductive control lines. Compared to switches made of phase-change material controlled for example by direct heating, for example by circulating a current through the phase-change material, or by indirect heating, for example by circulating a current through a electrically insulated heating element of the phase change material, for which two control lines are used, one to apply the control potential, the other to apply the reference potential, a single waveguide 164 is used to control the switching of each switch C1, C2.

[0084] Another advantage of the switches C1 and C2 is that they have a lower capacitance Coff in the off state than conventional indirect heating switches, which typically comprise a heating element made of an electrically conductive material, for example a metal, electrically insulated from the phase change material.

[0085] In the transmitter network 103, it is possible, for example, to use a different laser source LS to control each switch C1, C2 of each second antenna element 105b, the emission of the laser sources LS of the transmitter network 103 being controlled by a control circuit (not shown). As a variant, it is possible to use the same laser source LS to control several switches C1, C2 of the second antenna elements 105b of the transmitter network 103. In this case, each second antenna element 105b can, for example, be associated with an optical switch for controlling the switches C1 and C2 in phase opposition or with a multiplexer of the “1 to N” type, with N being an integer strictly greater than two, adapted to control several switches C1, C2 of several second antenna elements 105b.

[0086] An advantage of the C1 and C2 switches based on phase change material is that they are capable of operating at power levels at least as high as the switches generally used in elementary cells of antennas with a reconfigurable transmitter or reflector array, while exhibiting better linearity. In addition, the C1 and C2 switches exhibit excellent stability in frequency ranges of the order of terahertz.

[0087] Furthermore, the transmitter network 103 comprising cells 105 integrating the switches C1 and C2 advantageously has lower energy consumption than current transmitter networks comprising, for example, components such as pin diodes or varactors.

[0088] [Fig.7] is a schematic and partial sectional view of another switch C3 based on a phase change material according to one embodiment.

[0089] The switch C3 of [Fig.7] comprises elements in common with the switch C1 of [Fig.6]. These common elements will not be detailed again below. The switch C3 of [Fig.7] differs from the switch C1 of [Fig.6] in that, in the switch C3 of [Fig.7], the structure comprising the laser source LS, the layer 166, the waveguide 164 and the regions 140P, 140C, 160 and 162 is, in comparison with the switch C1 of [Fig.6], rotated relative to the upper face of the substrate 150. The example illustrated in [Fig.7] corresponds for example to a case where the switch C3 based on phase change material is produced on a so-called “functionalized” substrate.

[0090] More precisely, in the example illustrated in [Fig.7], the regions 140P and 140C are on and in contact with the upper face of the electrically insulating layer 166, that is to say the face of the layer 166 opposite the substrate 150. The region 160 made of phase change material is under and in contact with the overlying regions 140P and 140C. Furthermore, the waveguide 164 is in contact, by a part of its upper face, with the region 160. In the example shown, the active region 170 of the laser source LS is on and in contact with an underlying electrically conductive region 180, located on and in contact with the upper face of the substrate 150. The region 180 makes it possible, for example, to polarize the active region 170 of the laser source LS to control its emission. In this example, an electrically conductive layer 182 coats the underside of the substrate 150.

[0091] Although this has not been detailed in [Fig.7], electrically conductive vias making it possible to connect the interface layer 172 and the region 180 respectively to conductive tracks located on the side of the electrodes 140P and 140C, for example formed in the conductive plane 140, can be provided in the structure of the switch C3.

[0092] The switch C3 of [Fig.7] has an operation similar to that of the switch C1 of [Fig.6], and provides similar advantages. For example, each switch C1, C2 of the second antenna element 105b can be substituted by a switch having a structure identical or similar to that of the switch C3. Furthermore, although this has not been detailed, it can be provided that each cell 105 of the transmitter network 103 comprises one or more other switches each identical or similar to the switch C1, C2 or C3.

[0093] In the examples described above in relation to Figures 6 and 7, the laser source LS is of the “integrated” type, that is to say it is part of the same chip as the switch(es) with which it is associated. As a variant, a non-integrated laser source LS could be provided, that is to say formed on a chip different from that of the switch(es) with which it is associated, the laser source LS then being for example connected to the waveguide of each switch with which it is associated by an optical link, for example an optical fiber.

[0094] [Fig.8] is a perspective view of the output surface of the waveguide 164 according to one embodiment.

[0095] In the example shown, the waveguide 164 is superimposed on the region 160 of phase change material. More precisely, in this example, one face of the waveguide 164 (the lower face of the waveguide 164, in the orientation of the [Fig.8]) is on and in contact with a face of the region 160 made of phase change material (the upper face of the region 160, in the orientation of [Fig.8]). The output surface of the waveguide 164 has, for example, a tapered shape narrowing in the vicinity of the region 160 made of phase change material. Similarly, the region 160 made of phase change material may, as in the illustrated example, have a tapered shape narrowing in the vicinity of the waveguide 164. In this example, the waveguide 164 and the region 160 made of phase change material have a so-called “adiabatic” coupling.

[0096] [Fig.9] is a perspective view of an output surface of a waveguide according to another embodiment.

[0097] In the example shown, the waveguide 164 and the region 160 made of phase-change material are substantially coplanar. In the example illustrated, the output surface of the waveguide 164 comprises, for example, a face of the waveguide 164 located opposite a face of the region 160 made of phase-change material, said faces being substantially parallel to each other and orthogonal to a direction of propagation of the light in the waveguide 164. In this example, the waveguide 164 and the region 160 made of phase-change material have a so-called “butt coupling”.

[0098] Although Figures 8 and 9 illustrate embodiments of the output surface of the waveguide 164, a structure identical or similar to that of [Fig.8] or [Fig.9] could be provided at the input surface of the waveguide 164 to achieve optical coupling between the laser source LS and the waveguide 164.

[0099] Although examples of application to transmitting array antennas have been described above in relation to Figures 1 to 9, the described embodiments can be transposed by a person skilled in the art to applications using reflector array antennas. Such antennas typically comprise one or more primary sources irradiating a reflector array comprising a plurality of elementary cells, for example arranged in a matrix according to rows and columns, each cell typically comprising an antenna element, located on the side of a first face of the array arranged opposite the primary source and facing an emission medium of the antenna, and a reflector element, located on the side of a second face of the array opposite the first face.

[0100] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, the shape of the antenna element 105a may be adapted according to the polarization of the associated source 101.

[0101] Furthermore, although an example of an elementary cell 105 comprising two switches made of phase-change material C1 and C2 has been described, the described embodiments can be transposed by a person skilled in the art to any number of switches made of phase-change material. For example, a number of switches made of phase-change material greater than two could be provided in a case where it would be desired to produce a reconfigurable elementary cell having more than two different phase states.

[0102] Furthermore, although only one example of application to transmitting or reflecting array antennas has been described above, the optically controlled phase change material-based switches described in relation to FIGS. 6 and 7 may have other applications. More generally, such switches may be used in any application likely to benefit from a reduction in the number of electrical connection tracks for controlling a switch. For example, such switches may be integrated into filters, phase shifter circuits, etc. and, more generally, into any type of application using a switch.

[0103] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. Switch (Cl, C2; C3) based on a phase change material comprising: - a region (160) made of said phase change material connecting first and second conduction electrodes (140P, 140C) of the switch; and - a waveguide (164) comprising a first end facing a face of the region (160) made of said phase change material and a second end, opposite the first end, intended to be illuminated by a laser source (LS), in which the waveguide further comprises, on the side of its second and first ends, input and output surfaces respectively making it possible to receive and transmit radiation in a direction orthogonal to the direction of propagation of the radiation inside the waveguide.

2. Switch (Cl, C2; C3) according to claim 1, wherein the waveguide (164) comprises a central region of silicon nitride surrounded by a peripheral region (166) of silicon dioxide.

3. A switch (Cl, C2; C3) according to claim 1 or 2, wherein said phase change material is a chalcogenide material.

4. Switch (Cl, C2; C3) according to any one of claims 1 to 3, wherein the first and second conduction electrodes (140P, 140C) are part of an antenna element (105b) of a cell (105) of a transmitter array (103) or of a reflector array.

5. A switch (Cl, C2) according to any one of claims 1 to 4, wherein the first and second conduction electrodes (140P, 140C) are on and in contact with one face of a substrate (150).

6. A switch (C3) according to any one of claims 1 to 4, wherein the first and second conduction electrodes (140P, 140C) are on and in contact with one face of an electrically insulating layer (166) coating a substrate (150).

7. A switch according to any one of claims 1 to 6, wherein at least one end of the first and second ends of the waveguide (164) has a tapered shape.

8. Cell (105) of a transmitter network (103) or of a reflector network comprising at least one switch (Cl, C2; C3) according to any one of claims 1 to 7.

9. Transmitter network (103) or reflector network comprising: - a plurality of cells (105) according to claim 8; - one or more laser sources (LS); and - a control circuit for the laser source(s) (LS).

10. Network according to claim 9, in which each laser source (LS) is part of the same chip as each switch (Cl, C2; C3) with which it is associated.

11. Network according to claim 9, in which each laser source (LS) is part of a chip different from that of which each switch (Cl, C2; C3) to which it is associated is part, the laser source being connected to the waveguide (164) of said switch by an optical fiber.

12. An antenna (100) comprising a transmitting array (103) or a reflecting array according to any one of claims 9 to 11 and at least one source (101) configured to irradiate one face of the array.

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