Phase-change material-based switch

Abstract

Phase-Change Material-Based Switch This description relates to a phase-change material-based switch (200) comprising: – a region (103) of said phase-change material connecting the first and second conduction electrodes (101A, 101B) of the switch; and – an optical coupler (201) for a laser signal to activate the switch, located opposite a face of the region of said phase-change material. Figure for the abbreviation: Fig. 2B

Description

Title of the invention: Phase-change material-based switch Technical field

[0001] This description relates generally to electronic devices. More particularly, this description relates to switches based on a phase-change material capable of alternating between a crystalline, electrically conductive phase and an amorphous, electrically insulating phase. Prior art

[0002] Various applications take advantage of switches, or switches, based on a phase-change material to allow or prevent the flow of an electric current in a circuit. Such switches can be implemented in radio frequency communication applications, for example, to switch an antenna between transmit and receive modes, activate a filter corresponding to a frequency band, etc.

[0003] Existing phase-change material switches, however, suffer from various disadvantages. Summary of the invention

[0004] There is a need to improve existing phase change material-based switches.

[0005] To this end, one embodiment provides a switch based on a phase-change material comprising: - a region in said phase-change material connecting the first and second conduction electrodes of the switch; and - an optical coupler of a laser signal for activating the switch, located opposite a face of the region in said phase-change material.

[0006] According to one embodiment, the optical coupler comprises first and second waveguides superimposed opposite said face, the second waveguide being interposed between the first waveguide and the region in said phase-change material.

[0007] According to one embodiment, the first and second waveguides each comprise a central region in a first material surrounded by a peripheral region in a second material with an optical index lower than that of the first material.

[0008] According to one embodiment, the central regions of the first and second waveguides are superimposed, opposite each other and have the same trace at the vertical axis of the region in said phase change material.

[0009] According to one embodiment, the central regions of the first and second waveguides do not have the same trace outside the vertical axis of the region in said phase-change material.

[0010] According to one embodiment, the central region of the first waveguide has a geometry and dimensions substantially identical to those of the central region of the second waveguide.

[0011] According to one embodiment, the optical coupler is an adiabatic coupler.

[0012] According to one embodiment, the first and second waveguides comprise respectively, the exit and inlet surfaces each having, in top view, a tapered shape.

[0013] According to one embodiment, the laser signal is confined and guided mainly by the first waveguide, at the input of the optical coupler, and mainly by the second waveguide, at the output of the optical coupler.

[0014] 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.

[0015] One embodiment provides a transmitting network cell or reflecting network cell comprising at least one switch as described.

[0016] One embodiment provides for a transmitting network or a reflecting network comprising: - a plurality of cells as described; - one or more laser sources; and - a control circuit for the laser source(s).

[0017] According to one embodiment, each laser source is part of the same chip as each switch to which it is associated.

[0018] One embodiment provides an antenna comprising a transmitting array or a reflecting array as described and at least one source configured to irradiate one face of the array. Brief description of the drawings

[0019] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0020] [Fig.1A] and [Fig.1B] are schematic and partial views, respectively from above and in section along plane BB of [Fig.1A], illustrating an example of a switch based on a phase change material;

[0021] [Fig.2A], [Fig.2B] and [Fig.2C] are schematic and partial views, respectively from above, in section along plane BB of [Fig.2A] and in section along plane CC of [Fig.2A], illustrating an example of a phase-change material-based switch according to an embodiment;

[0022] [Fig.3] is a schematic and partial side view of an example of a transmitting array antenna of the type to which, by way of example, described embodiments apply;

[0023] [Fig. 4] is an isometric, schematic and partial view of an elementary cell of the transmitting array of the antenna of [Fig. 3] according to one embodiment; and

[0024] [Fig.5] is a schematic and partial top view illustrating an example of a phase change material-based switch according to one embodiment. Description of the implementation methods

[0025] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0026] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the control circuits of switches based on a phase-change material and the applications in which such switches may be used have not been detailed, as the described embodiments and variants are compatible with conventional control circuits of switches based on a phase-change material and with conventional applications using switches based on a phase-change material.

[0027] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements coupled together, this means that these two elements can be connected or linked through one or more other elements.

[0028] In the following description, when referring to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative positional qualifiers, such as the terms "above", "below", "superior", "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.

[0029] Unless otherwise specified, the expressions "approximately", "roughly", "about", and "in the order of" mean within 10%, preferably within 5%.

[0030] Fig. 1A and Fig. 1B are schematic and partial views, respectively top and cross-sectional along plane BB of Fig. 1A, illustrating an example of a switch 100 based on a phase-change material. In the example shown, plane BB of Fig. 1A is a vertical plane parallel to a conduction direction of the switch 100.

[0031] In figures IA and IB, the direction of conduction of the switch 100 is parallel to a horizontal axis Oy, and the plane BB is parallel to a vertical plane Oyz orthogonal to an axis Ox.

[0032] In the example shown, the switch 100 comprises conduction electrodes 101A and 101B. The conduction electrodes 101A and 101B of the switch 100 are, for example, intended to be connected to a radio frequency communication circuit, not detailed in the figures. The conduction electrodes 101A and 101B are made of an electrically conductive material, for example a metal, such as copper or aluminum, or a metal alloy. Furthermore, the conduction electrodes 101A and 101B may have a single-layer or multi-layer structure.

[0033] Although not detailed in Figures IA and IB to avoid cluttering the drawing, the conduction electrodes 101A and 101B of the switch 100 are, for example, located on and in contact with the upper surface of an electrically insulating layer, for example, of silicon dioxide (SiO2), coating a substrate. By way of example, the substrate in this case is a wafer or a piece of wafer made of a semiconductor material, for example, silicon.

[0034] In the illustrated example, the switch 100 further comprises a region 103 made of a phase-change material connecting the conduction electrodes 101A and 101B. Although not detailed in the figures, the region 103 made of phase-change material has, for example, an upper surface covered with another electrically insulating layer, for example, silicon dioxide, extending laterally between the electrodes 101A and 101B, the electrically insulating layer being flush with, for example, the upper surfaces of the electrodes 101A and 101B. In the example shown, the region 103 made of phase-change material extends onto and is in contact with a portion of the upper surface of each conduction electrode 101A, 101B. By way of example, the region 103 made of phase-change material has a thickness on the order of 100 nm.

[0035] By way of example, region 103 of switch 100 is made of a so-called "chalcogenide" material, that is to say, a material or alloy comprising at least one chalcogen element, for example a material from the germanium telluride (GeTe), antimony telluride (SbTe) or germanium-antimony-telluride (GeSbTe, commonly referred to by the acronym "GST") family. As an alternative, region 103 is made of vanadium dioxide (VO2).

[0036] Generally speaking, phase-change materials are materials capable of alternating, under the effect of a temperature variation, between a crystalline phase and an amorphous phase, the amorphous phase having a higher electrical resistance than the crystalline phase. In the case of the switch 100, this phenomenon is exploited to obtain a blocked state, preventing the flow of current between the conduction electrodes 101A and 101B, when the material in the region 103 located between the conduction electrodes is in the amorphous phase, and a conducting state, allowing the flow of current between the conduction electrodes 101A and 101B, when the material in the region 103 is in the crystalline phase.

[0037] In the example shown, the switch 100 further comprises a waveguide 105 located opposite the phase-change material region 103 and extending laterally along a principal direction substantially orthogonal to the conduction direction of the switch 100. In Figures IA and IB, the waveguide 105 of the switch 100 extends parallel to the Ox axis. The waveguide 105 has, for example, a first end located opposite an upper face of the phase-change material region 103 and a second end, opposite the first end, intended to be illuminated by a laser source LS. By way of example, the radiation emitted by the laser source LS has either magnetic transverse polarization (TM) or electrical transverse polarization (TE).

[0038] In the illustrated example, the waveguide 105 comprises a central region 107, or core, surrounded by an electrically insulating peripheral region 109. In the illustrated example, the central region 107 of the waveguide 105 extends parallel to the Ox axis. The central region 107 and the peripheral region 109 of the waveguide 105 are made of materials chosen to obtain a contrast in optical indices that allows for the confinement and guiding of an optical mode of interest emitted by the laser source LS. The material of the central region 107 of the waveguide 105, for example, has a higher optical index than that of the peripheral region 109. By way of example, the central region 107 of the waveguide 105 is made of silicon nitride and the peripheral region 109 is made of silicon dioxide.

[0039] The BB plane of [Fig. 1A] is substantially orthogonal to a direction of propagation of the laser radiation in the waveguide 105. The direction of propagation of the laser radiation in the waveguide 105 is, in the example illustrated, parallel to the Ox axis. In the example shown, the peripheral region 109 of the waveguide 105 covers the faces of the central region 107 parallel to the direction of propagation of the laser radiation (the lateral, lower and upper faces of the central region 107 of the waveguide 105 parallel to the Ox axis, in figures IA and IB). In this example, part of the peripheral region 109 of the waveguide 105 extends vertically along the vertical axis Oz orthogonal to the horizontal axes Ox and Oy, from a face of the central region 107 located opposite the region 103 in phase-change material (the lower face of the central region 107 of the waveguide 105, in the orientation of [Fig.1B]) to a face of the region 103 in phase-change material opposite the conduction electrodes 101A and 101B (the upper face of the region 103 in phase-change material, in the orientation of [Fig.1B]).

[0040] In the example shown, the central region 107, in cross-sectional view along the plane BB orthogonal to the direction of laser radiation propagation in the waveguide 105, has a substantially rectangular shape. For example, the central region 107, in cross-sectional view along the plane BB, has a width w (along the Ox axis) of approximately 300 nm and a height h (along the Oz axis) of approximately 350 nm. Furthermore, the central region 107 of the waveguide 105 is separated from the phase-change material region 103 by a distance g. In this example, the distance g is equivalent to the thickness of the portion of the peripheral region 109 interposed between the central region 107 of the waveguide 105 and the phase-change material region 103. For example, the distance g is approximately 300 nm.

[0041] The waveguide 105 is, for example, of the single-mode type, meaning that it is adapted to confine and guide a single optical mode for each type of polarization. More precisely, the waveguide 105 is adapted to confine and guide a single optical mode chosen from a zero-order transverse electric mode (TE0), parallel to the Oy axis, and a zero-order transverse magnetic mode (TM0), parallel to the Oz axis. Because the TE0 and TM0 modes are orthogonal, they cannot couple to each other in the waveguide 105. The choice of the mode confined and guided by the waveguide 105, between the TE0 mode and the TM0 mode, is determined by the polarization of the laser source LS. Thus, in a case where the laser source LS emits radiation exhibiting a magnetic transverse polarization TM, the waveguide 105 is suitable for confining and guiding the zero-order magnetic transverse mode TM0 only.

[0042] On the side of its end intended to be illuminated by the laser source LS, the waveguide 105 includes, for example, an input coupling element, also called the input surface of the waveguide 105. On the side of its end located opposite the region 103 in phase change material, the waveguide 105 may further include an output coupling element, also called the output surface of the waveguide 105. The input coupling element may have a structure, for example a diffraction grating having a Bragg structure or any other coupling structure, allowing the radiation emitted by the laser source LS to be captured and propagated to the output surface.

[0043] Furthermore, the output surface of the waveguide 105 may have a structure that allows the radiation propagated from the input surface to be re-emitted towards the phase-change material region 103. Although not detailed in Figures IA and IB, the output surface of the waveguide 105 may have a structure identical or similar to that of its input surface.

[0044] Generally, the inlet and outlet surfaces of the waveguide 105 allow, respectively, in the example shown, the reception and transmission of radiation along a direction orthogonal to the direction of radiation propagation inside the waveguide 105, for example, a direction parallel to the Oz axis. Alternatively, at least one surface among the inlet and outlet surfaces of the waveguide 105 may have a structure allowing the reception or transmission of radiation along a direction parallel to the direction of radiation propagation inside the waveguide 105 (parallel to the Ox axis, in this example).

[0045] To switch the switch 100 from the blocked state to the conducting state, the region 103 is heated, for example, using the laser source LS, via the waveguide 105, to a temperature Tl and for a duration dl. The temperature Tl and the duration dl are chosen so as to induce a phase change of the material in region 103 from the amorphous phase to the crystalline phase. By way of example, the temperature Tl is above the crystallization temperature and below the melting temperature of the material undergoing the phase change, and the duration dl is between 10 and 100 ns.

[0046] Conversely, to switch the switch 100 from the conducting state to the blocking state, the region 103 is heated, for example, using the laser source LS, via the waveguide 105, to a temperature T2, higher than the temperature T1, and for a duration d2, shorter than the duration d1. The temperature T2 and the duration d2 are chosen so as to induce a phase change of the material in region 103 from the crystalline phase to the amorphous phase. By way of example, the temperature T2 is higher than the melting temperature of the material undergoing the phase change, and the duration d2 is on the order of 10 ns.

[0047] By way of example, in a case where the LS laser source is krypton fluoride based, radiation with a wavelength of approximately 248 nm is emitted by the LS laser source, for example in the form of pulses, to induce transitions in the material of region 103 between the amorphous and crystalline phases. A pulse with a fluence of approximately 85 mJ / cm² is used, for example, to induce a transition of the material in region 103 from the amorphous to the crystalline phase. Furthermore, another pulse with a fluence of approximately 185 mJ / cm² is used, for example, to induce a transition of the material in region 103 from the crystalline to the amorphous phase.

[0048] One drawback of the switch 100 is that the laser radiation emitted by the LS source is not absorbed homogeneously in the phase-change material region 103 along the direction of radiation propagation in the waveguide 105 (along the Ox axis, in this example). In the example of the switch 100, the laser radiation is mostly absorbed by a first part 103N of the phase-change material region 103 close to the laser source LS, with the absorption of the laser radiation being lower in a second part 103F of the phase-change material region 103, opposite the first part 103N, which is further from the laser source LS than the first part 103N. The optical absorption of laser radiation by the 103 region in phase-change material more precisely follows a decreasing exponential from the 103N part of the 103 region to the 103F part.

[0049] Thus, during an activation phase of the switch 100, the optical power absorbed by the second part 103F of the region 103 may prove insufficient to cause a phase change of the material in the part 103F. In the case where it is desired to switch the switch 100 from the conducting state to the blocking state, this may prevent the second part 103F of the region 103 from changing phase from the crystalline phase to the amorphous phase, thus undesirably allowing the passage of a leakage current between the conduction electrodes 101A and 101B of the switch 100.

[0050] The inventor observed that the phenomenon arises from the fact that the magnetic transverse mode TM of the laser signal activating the switch 100, confined and guided by the waveguide 105, is strongly absorbed by the phase-change material of region 103, thus leading to a heating of part 103N much greater than that observed in part 103F. To overcome this problem, one could have considered modifying the geometry of the waveguide 105 to confine and guide only the electrical transverse mode TE, which is absorbed less strongly by the phase-change material of region 103 than the magnetic transverse mode TM. As an example, the magnetic transverse mode TM exhibits losses, due to absorption by the phase-change material of region 103, on the order of 2,500 dB.cm*. compared to approximately 500 dB·cm⁻¹ for the electric transverse mode (TE). However, for equivalent laser power values, this would not generate sufficient heating of region 103 to induce a phase change. More generally, in both electric transverse mode (TE) and magnetic transverse mode (TM), optical absorption follows a decreasing exponential law for this waveguide configuration. However, it would be preferable for the absorption to follow a linear law to allow for a phase change in the material state of region 103.

[0051] Fig. 2A, Fig. 2B and Fig. 2C are schematic and partial views, respectively from above, in section along plane BB of Fig. 2A and in section along plane CC of Fig. 2A, illustrating an example of a 200 switch based on a phase change material according to an embodiment.

[0052] The switch 200 of Figures 2A, 2B, and 2C includes elements common to the switch 100 of Figures 1A and 1B. These common elements will not be detailed again below. The switch 200 of Figures 2A, 2B, and 2C differs from the switch 100 of Figures 1A and 1B in that the switch 200 includes an optical coupler 201. In this example, the optical coupler 201 has two waveguides 205-1 and 205-2 superimposed opposite the region 103 made of phase-change material.

[0053] In the illustrated example, waveguide 205-2 is interposed between waveguide 205-1 and the phase-change material region 103. In this example, waveguide 205-1, being furthest from the phase-change material region 103, is intended to receive the laser activation signal for switch 200 from the LS source, and waveguide 205-2, being closer to the phase-change material region 103 than waveguide 205-1, is intended to be optically coupled, by an evanescent field, to waveguide 205-1. By way of example, waveguides 205-1 and 205-2 form a directional optical coupler 201.

[0054] With reference to the orientation of figures 2B and 2C, the waveguides 205-1 and 205-2 will sometimes, in the following description, be referred to respectively as "upper" and "lower".

[0055] In this example, the optical coupler 201 is designed so that the signal, at the input of the optical coupler 201, i.e., in the vicinity of part 103N of region 103, is confined and guided mainly in the upper waveguide 205-1 and, at the output of the optical coupler 201, i.e., in the vicinity of part 103F of region 103, is confined and guided mainly in the lower waveguide 205-2. The waveguides 205-1 and 205-2 each allow, for example, the confinement and guidance of the magnetic transverse mode TM of the laser signal for activating the switch 200 emitted by the LS source. By way of example, the magnetic transverse mode TM The upper waveguide 205-1 exhibits losses, due to absorption by the phase-change material in region 103, of approximately 500 dB·cm², compared to about 2,500 dB·cm² for the lower waveguide 205-2. By injecting the laser control signal from switch 200 into the upper waveguide 205-1, coupled to the lower waveguide 205-2 directly above the phase-change material region 103, the optical power is better distributed between the 103N portion of the phase-change material region 103, closest to the laser source LS, and the 103F portion of the region 103, furthest from the laser source LS. In this example, the radiation emitted by the laser source LS has a magnetic transverse polarization TM.

[0056] In the example shown, each waveguide 205-1, 205-2 has, for example, a structure identical or analogous to that of the waveguide 105 previously described in relation to Figures IA and IB. In the illustrated example, each waveguide 205-1, 205-2 comprises a central region 207-1, 207-2, or core, surrounded by an electrically insulating peripheral region 209. The central region 207-1, 207-2 and the peripheral region 209 of each waveguide 205-1, 205-2 are made of materials chosen to obtain a contrast in optical indices that confines and guides the optical mode of interest emitted by the laser source LS. The material of the central region 207-1, 207-2 of each waveguide 205-1, 205-2 has, for example, a higher optical index than that of the peripheral region 209. As an example, the central region 207-1, 207-2 of each waveguide 205-1, 205-2 is made of silicon nitride and the peripheral region 209 is made of silicon dioxide..

[0057] In the illustrated example, the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2 are superimposed, opposite each other and have the same trace vertically above the region 103. On the other hand, in this example, the regions 207-1 and 207-2 are not located opposite each other and / or do not have the same trace outside the vertically above the region 103 in phase change material. This ensures that the optical coupling between the waveguides 205-1 and 205-2 occurs predominantly opposite region 103. This also helps to limit optical reflections due to a sudden, or abrupt, change in optical index, which would be observed for example in a case where region 207-2 of the lower waveguide 205-2 is abruptly interrupted above region 207-1 of the upper waveguide 205-1.

[0058] The BB plane of [Fig. 2A] is substantially orthogonal to a direction of laser radiation propagation in the waveguides 205-1 and 205-2 opposite region 103 (orthogonal to the Ox axis and parallel to the Oyz plane, in the illustrated example). In the example shown, directly above region 103 in material with phase change, the peripheral region 209 of the waveguides 205-1 and 205-2 covers the faces of the central regions 207-1 and 207-2 parallel to the direction of propagation of the laser radiation (the lateral, lower and upper faces of the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2 parallel to the Ox axis, in the orientation of figures 2A, 2B and 2C). In this example, part of the peripheral region 209 of the waveguides 205-1 and 205-2 extends vertically along the Oz axis from a face of the central region 207-1 located opposite the lower waveguide 205-2 (the lower face of the central region 207-1 of the upper waveguide 205-1, in the orientation of [Fig.2B]) to a face of the central region 207-2 of the lower waveguide 205-2 opposite the phase-change material region 103 (the upper face of the central region 207-2 of the lower waveguide 205-2, in the orientation of [Fig.2B]).In addition, another part of the peripheral region 209 of the waveguides 205-1 and 205-2 extends vertically, along the Oz axis, from a face of the central region 207-2 located opposite the phase-change material region 103 (the lower face of the central region 207-2 of the lower waveguide 205-2, in the orientation of [Fig.2B]) to a face of the phase-change material region 103 opposite the conduction electrodes 101A and 101B (the upper face of the phase-change material region 103, in the orientation of [Fig.2B]).

[0059] In the example shown, the central regions 207-1 and 207-2 each have, in cross-sectional view along plane BB, a substantially rectangular shape. By way of example, the central region 207-1 of the upper waveguide 205-1 has a cross-section of identical shape and dimensions, apart from manufacturing variations, to those of the central region 207-2 of the lower waveguide 205-2. More precisely, in the orientation of [Fig. 2B], the central regions 207-1, 207-2 of each waveguide 205-1, 205-2 have the same width wl, along the Ox axis, and the same height hl, along the Oz axis. This example is not limiting, however, the central region 207-2 of the lower waveguide 205-2 may, as an alternative, have a cross-section of different shape and dimensions than the cross-section of the central region 207-1 of the upper waveguide 205-1.

[0060] Furthermore, the central region 207-1 of the upper waveguide 205-1 is separated from the central region 207-2 of the lower waveguide 205-2 by a distance gl. In this example, the distance gl is equivalent to the thickness of the portion of the peripheral region 209 interposed between the central region 207-1 of the waveguide 205-1 and the central region 207-2 of the waveguide 205-2. Moreover, the central region 207-2 of the waveguide 205-2 is separated from the phase-change material region 103 by a distance g2. In this example, the distance g2 is equivalent to the thickness of the portion of the peripheral region 209 interposed between the central region 207-2 of the waveguide 205-2 and the region 103 in phase change material.

[0061] Table 1 below provides examples of values ​​for the height hl, the width wl, and the distances gl and g2 as a function of a width L of the region 103 in phase-change material along the Ox axis, i.e. perpendicular to the conduction Oy axis of the switch 200 and parallel to the direction of propagation of the laser signal in the optical coupler 201. The width L of the region 103 in phase-change material is considered parallel to the direction of propagation of the control laser signal of the switch 200 in the optical coupler 201 above the region 103 (parallel to the Ox axis, in the illustrated example).

[0062] [Tables 1] L (pm) gl (nm) g2 (nm) hl (nm) wl (nm) 100 600 300 300 1000 90 700 400 300 400 55 600 300 300 400 45 700 300 200 600 35 350 75 300 450 30 400 200 300 600

[0063] Table [Table 2] below provides, by way of example, minimum and maximum values ​​for each dimension hl, wl of the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2 and for the distances gl and g2, the width L of the region 103 in phase change material being, by way of non-limiting example, between 30 and 100 pm.

[0064] [Tables2] Dimension or distance Minimum value Maximum value gl (nm) 400 700 g2 (nm) 75 400 hl (nm) 200 300 wl (nm) 400 1000

[0065] The examples provided above are not, however, limiting, and a person skilled in the art is able to define the values ​​of the dimensions hl and wl of the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2 and the values ​​of the distances gl and g2 as a function of the width L of the region 103 in phase-change material. Numerical simulation tools can, for example, be used for this purpose. A As an example, the distances gl and g2 and the height hl can be constrained due to the thicknesses of material layers deposited during manufacturing steps of switch 200.

[0066] An advantage of the switch 200 described above in relation to Figures 2A, 2B and 2C is that the presence of the optical coupler makes it possible for the laser control signal of the switch 200 to be absorbed substantially uniformly by the phase-change material of the region 103. More specifically, in the case of the switch 200, only the weakly absorbed magnetic transverse mode TM in the upper waveguide 205-1 is present near the input of the optical coupler 201 (above the 103N part of the region 103), while only the strongly absorbed magnetic transverse mode TM in the lower waveguide 205-2 is present near the output of the optical coupler 201 (above the 103F part of the region 103).This prevents, compared to switch 100 in figures IA and IB, a part of the region 103 made of phase-change material, for example the part 103F furthest from the laser source LS, from not changing phase when the switch is controlled.

[0067] Fig. 3 is a schematic and partial side view of an example of a 400 transmitting array antenna of the type to which, by way of example, described embodiments apply.

[0068] The antenna 400 typically comprises one or more primary sources 401 (a single source 401 in the example shown) radiating a transmitting array 403. The source 401 may have any polarization, for example, linear or circular. The array 403 comprises a plurality of elementary cells 405, for example, arranged in a matrix in rows and columns. Each cell 405 typically comprises a first antenna element 405a, located on the side of a first face of the array 403 facing the primary source 401, and a second antenna element 405b, located on the side of a second face of the array 403 opposite the first face. The second face of the array 403 is, for example, directed towards a transmission medium of the antenna 400.

[0069] Each cell 405 is capable, in transmission, of receiving electromagnetic radiation on its first antenna element 405a and of re-emitting this radiation from its second antenna element 405b, for example by introducing a known phase shift θ. In reception, each cell 405 is capable of receiving electromagnetic radiation on its second antenna element 405b and of re-emitting this radiation from its first antenna element 405a, towards the source 401, with the same phase shift θ. The radiation re-emitted by the first antenna element 405a is, for example, focused on the source 401.

[0070] The characteristics of the beam produced by the antenna 400, 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 405 of the network 403.

[0071] Transmitter array antennas have the advantages, among others, of exhibiting good energy efficiency and being relatively simple, inexpensive, and compact. This stems in particular from the fact that the transmitter arrays can be implemented using planar technology, generally on a printed circuit board.

[0072] We are particularly interested here in antennas with a reconfigurable transmitting array 403. The transmitting array 403 is said to be reconfigurable when the elementary cells 405 can be individually electronically controlled to modify their phase shift value q>, 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.

[0073] Figure 4 is an isometric, schematic, and partial view of one of the cells elementary 405 of the transmitting network 403 of the antenna 400 of the [Fig.3] according to an embodiment.

[0074] In the example shown, the first antenna element 405a of the elementary cell 405 comprises a patch antenna 410 adapted to receive the electromagnetic radiation emitted by the source 401, and the second antenna element 405b comprises another patch antenna 412 adapted to transmit a phase-shifted signal outward from the antenna 400. In the example shown, the elementary cell 405 further comprises a ground plane 414 interposed between the patch antennas 410 and 412.

[0075] The antenna 410, the ground plane 414, and the antenna 412 are, for example, formed respectively in three successive metallization layers, superimposed and separated from each other by dielectric layers, for example, of quartz. By way of example, the ground plane 414 is separated from each of the antennas 410 and 412 by a thickness of dielectric material on the order of 200 pm.

[0076] In the example shown, a central conductor via 416 connects the antenna 410 to the antenna 412. More specifically, in the orientation of [Fig. 4], the via 416 has its lower end in contact with an upper face of the antenna 410 and its upper end in contact with an lower face of the antenna 412. The central conductor via 416 is electrically isolated from the ground plane 414. In the example shown, the ground plane 414 has a circular opening with a diameter larger than that of the via 416, thus allowing the via 416 to pass through the plane. of mass 414 without the via 416 being in contact with the ground plane 414. As an example, the central conductor via 416 has a diameter equal to approximately 80 pm.

[0077] In the example shown, the antenna 412 comprises a four-sided conducting plane 440. The conducting plane 440 is, for example, more precisely rectangular in shape or, as in the example illustrated in [Fig. 4], substantially square in shape.

[0078] In the illustrated example, the conducting plane 440 has an opening 442 separating a central region 440C of the conducting plane 440 from a peripheral region 440P of the conducting plane 440. In this example, the opening 442 has a substantially annular shape, for example a rectangular or square annular shape.

[0079] In the example shown, the central conductor via 416 is in contact with the central region 440C of the conducting plane 440. More precisely, in this example, the upper end of the via 416 is connected substantially to the center of a lower face of the region 440C. The central region 440C of the conducting plane 440, laterally delimited by the annular opening 442, constitutes, for example, an input terminal of the antenna 412.

[0080] The antenna 412 further comprises a first switching element Cl and a second switching element C2, each connecting the central region 440C to the peripheral region 440P of the conducting plane 440. More specifically, in the example illustrated in [Fig. 4], the first and second switching elements Cl and C2 contact the peripheral region 440P in diametrically opposite areas with respect to the central conducting via 416. In this example, the switching elements Cl and C2 and the conducting via 416 are located on the same straight line parallel to one side of the conducting plane 440. In this example, the switch Cl is located substantially vertically above the horizontal arm of the U formed by the slot 442.

[0081] The switching elements Cl and C2 are controlled in opposition, that is, such that if one of the switches Cl, C2 is conducting, the other switch C2, Cl is blocked. This allows the second antenna element 405b of the elementary cell 405 to switch between two phase states q>, substantially equal to 0° and 180° in this example. The phase states 0° and 180° correspond respectively to the case where switch Cl is blocked while switch C2 is conducting, and to the case where switch Cl is conducting while switch C2 is blocked.

[0082] Each switching element Cl, C2 of the elementary cell 405 is, for example, implemented by the switch 200 described previously. In this case, using the laser source LS to control the switches Cl and C2 of the antenna element 405b 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, e.g., by passing a current through the phase-change material, or by indirect heating, for example by circulating a current through a heating element electrically isolated from 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 optical control line, for example the upper waveguide 205-1 of the optical coupler of each switch Cl, C2, is used to control the switching of each switch Cl, C2.

[0083] Another advantage of the Cl and C2 switches is that they have a lower Coff capacitance in the blocked state than conventional indirect heating switches, which typically have a heating element made of an electrically conductive material, for example a metal, electrically isolated from the phase-change material.

[0084] In the transmitter network 403, it is possible, for example, to use a different laser source LS to control each switch Cl, C2 of each second antenna element 405b, the emission of the laser sources LS of the transmitter network 403 being controlled by a control circuit (not shown). The laser source LS is then, for example, of the "integrated" type, that is to say, it is part of the same chip as the switch(es) to which it is associated.

[0085] As an alternative, it is possible to use the same laser source LS to control several switches Cl, C2 of the second antenna elements 405b of the transmitting network 403. In this case, each second antenna element 405b can for example be associated with an optical control switch of the switches Cl and C2 in opposite phase or with a multiplexer of the type "1 to N", with N an integer strictly greater than two, adapted to control several switches Cl, C2 of several second antenna elements 405b.

[0086] One advantage of the phase-change material-based Cl and C2 switches is that they are capable of operating at power levels at least as high as those typically used in elementary cells of transmitting or reconfigurable reflecting array antennas, while exhibiting improved linearity. Furthermore, the Cl and C2 switches exhibit excellent stability in frequency ranges on the order of terahertz.

[0087] Moreover, the 403 transmitter network comprising cells 405 integrating switches Cl and C2 advantageously presents a lower energy consumption than current transmitter networks comprising, for example, components such as pin diodes or varactors.

[0088] Fig. 5 is a schematic and partial top view illustrating an example of a 500 phase change material switch according to one embodiment.

[0089] The switch 500 of [Fig. 5] includes elements common to the switch 200 of Figures 2A, 2B and 2C. These common elements will not be detailed again below. The switch 500 of [Fig. 5] differs from the switch of Figures 2A, 2B and 2C in that the optical coupler 201 of the switch 500 is of the "adiabatic" type.

[0090] In the example shown, the outlet surface of the upper waveguide 205-1 and the inlet surface of the waveguide 205-2 each have a tapered shape when viewed from above. More specifically, in this example, the central region 207-1 of the upper waveguide 205-1 is wider directly above part 103N of region 103 than directly above part 103F, and the central region 207-2 of the lower waveguide 205-2 is wider directly above part 103F of region 103 than directly above part 103N. This creates an adiabatic coupling between the upper waveguide 205-1 and the lower waveguide 205-2.

[0091] In the example shown, the propagation axes of the radiation inside the waveguides 205-1 and 205-2 are substantially parallel to each other, and parallel to the Ox axis, the waveguides 205-1 and 205-2 being, for example, each substantially straight.

[0092] 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 become apparent to those skilled in the art. In particular, the geometry and dimensions of the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2 can be adapted by those skilled in the art from the indications in this description, for example, according to the intended application. By way of example, the central region 207-2 of the lower waveguide 205-2 could begin directly above the 103N portion of the phase-change material region 103 and / or end directly above the 103F portion of the region 103.

[0093] Furthermore, although an example of an elementary cell 405 comprising two switches made of phase-change material Cl and C2 has been described, the embodiments described can be transposed by those skilled in the art to any number of switches made of phase-change material. By way of example, one could provide for a number of switches made of phase-change material greater than two in a case where it is desired to create a reconfigurable elementary cell exhibiting more than two different phase states.

[0094] Furthermore, although only one example of application to transmitting array antennas has been described above, the optically controlled phase-change material-based switch described in relation to Figures 2A, 2B, and 2C may have other applications. More generally, such a switch may be used in any application that can benefit from a reduction in the number of electrical connection traces for controlling a switch. For example, such a switch can be integrated into reflector array antennas, filters, phase-shifting circuits, etc., and, more generally, into any type of application using a switch.

[0095] In particular, the transposition of the embodiments described to the case of a reflector array antenna is within the reach of a person skilled in the art from the indications in this description.

[0096] Furthermore, a person skilled in the art is able, from the indications in this description, to foresee that each of the phase change switches Cl and C2 of the elementary cell 405 is identical or similar to the switch 500 of [Fig.5].

[0097] Finally, the practical implementation of the described embodiments and variants is within the reach of a person skilled in the art, based on the functional specifications given above. In particular, the described embodiments are not limited to the specific examples of materials and dimensions mentioned in this description. Furthermore, the embodiments are not limited to the example of the geometry of the plate antennas 410 and 412 described in relation to [Fig. 4], but apply more generally to any type of antenna geometry.

Claims

Demands

1. Switch (200; 500) based on a phase-change material comprising: - a region (103) in said phase-change material connecting first and second conduction electrodes (101A, 101B) of the switch; and - an optical coupler (201) of a laser signal for activating the switch, located opposite a face of the region in said phase-change material, in which the optical coupler (201) comprises first and second waveguides (205-1, 205-2) superimposed opposite said face, the second waveguide (205-2) being interposed between the first waveguide (205-1) and the region (103) in said phase-change material.

2. Switch (200; 500) according to claim 1, wherein the first and second waveguides (205-1, 205-2) each comprise a central region (207-1, 207-2) of a first material surrounded by a peripheral region (209) of a second material of lower optical index than that of the first material.

3. Switch (200) according to claim 2, wherein the central regions (207-1, 207-2) of the first and second waveguides (205-1, 205-2) are superimposed, facing each other and have the same trace perpendicular to the region (103) in said phase-change material.

4. Switch (200) according to claim 2 or 3, wherein the central regions (207-1, 207-2) of the first and second waveguides (205-1, 205-2) do not exhibit the same path out of the plumb of the region (103) in said phase-change material.

5. Switch (200) according to any one of claims 2 to 4, wherein the central region (207-1) of the first waveguide (205-1) has a geometry and dimensions substantially identical to those of the central region (207-2) of the second waveguide (205-2).

6. Switch (500) according to claim 1 or 2, wherein the optical coupler (201) is an adiabatic coupler.

7. Switch (500) according to claim 6, wherein the first and second waveguides (205-1, 205-2) comprise respectively, the exit and inlet surfaces each having, in top view, a tapered shape.

8. Switch (200; 500) according to any one of claims 1 to 7, wherein the laser signal is confined and guided predominantly by the first waveguide (205-1), at the input of the optical coupler (201), and predominantly by the second waveguide (205-2), at the output of the optical coupler.

9. Switch (200; 500) according to any one of claims 1 to 8, wherein the first and second conduction electrodes (101 A, 101 B) are part of an antenna element (405a) of a cell (405) of a transmitting array (403) or reflecting array.

10. Cell (405) of a transmitting network (403) or reflecting network comprising at least one switch (200; 500) according to any one of claims 1 to 9.

11. Transmitter network (403) or reflector network comprising: - a plurality of cells (405) according to claim 10; - one or more laser sources (LS); and - a control circuit for the laser source(s).

12. Network (403) according to claim 11, wherein each laser source (LS) is part of the same chip as each switch (200) to which it is associated.

13. Antenna (400) comprising a transmitting array (403) or a reflecting array according to claim 11 or 12 and at least one source (401) configured to irradiate one face of the array.