Switch based on phase change material

Abstract

The present specification relates to a switch (200) based on a phase change material, comprising:-a region (103) made of said phase change material coupling a first and a second conductive electrode (101A, 101B) of the switch; and-a rotator (205) for activating the polarization of the laser signal of the switch, located in front of the surface of the region made of the phase change material.

Description

Technical Field

[0001] The present disclosure relates generally to electronic devices and more particularly to switches based on phase change materials that are capable of alternating between a crystalline conductive phase and an amorphous electrically insulating phase. Background Art

[0002] Various applications utilize switches based on phase change materials to allow or prevent current from flowing in a circuit. Such switches can be implemented in particular in radio frequency communication applications, such as switching an antenna between transmit and receive modes, activating filters corresponding to frequency bands, and so on.

[0003] However, existing switches based on phase change materials suffer from various disadvantages. Summary of the invention

[0004] There is a need to improve existing switches based on phase change materials.

[0005] To this end, one embodiment provides a switch based on a phase change material, comprising:

[0006] - a region made of said phase change material, coupling the first conductive electrode and the second conductive electrode of the switch; and

[0007] - A polarization rotator of the laser signal used to activate the switch, located in front of the surface of the area made of said phase change material.

[0008] According to one embodiment, the polarization rotator comprises a central region made of a first material surrounded by a peripheral region made of a second material having a lower optical index than the first material.

[0009] According to one embodiment, the polarization rotator is adapted to induce a rotation of the polarization of the laser signal between an input surface and an output surface opposite the input surface for activating switching between the transverse electric mode and the transverse magnetic mode.

[0010] According to one embodiment, the central region has an asymmetric cross-section along the propagation direction of the laser signal in the polarization rotator.

[0011] According to one embodiment, the cross section of the central region is constant along the entire length of the polarization rotator.

[0012] According to one embodiment, a cross section of the central region has an L-shape in a plane orthogonal to the propagation direction of the laser signal.

[0013] According to one embodiment, the cross section of the central region varies along the propagation direction of the laser signal in the polarization rotator.

[0014] According to one embodiment, the first conducting electrode and the second conducting electrode form part of an antenna element of an element of a transmitting array or a reflecting array.

[0015] One embodiment provides a unit of a transmit array or a reflective array comprising at least one switch as described.

[0016] One embodiment provides a transmitting array or a reflecting array, comprising:

[0017] - a plurality of units such as described;

[0018] - one or more laser sources; and

[0019] -Circuitry for controlling the laser source.

[0020] According to one embodiment, each laser source forms part of the same chip as each switch with which it is associated.

[0021] One embodiment provides an antenna comprising a transmit array or a reflective array as described and at least one source configured to illuminate a surface of the array. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The foregoing features and advantages, as well as other features and advantages, will be described in detail in the remainder of the disclosure of specific embodiments, by way of illustration and not limitation, with reference to the accompanying drawings, in which:

[0023] Figure 1A and Figure 1B is a simplified partial view, respectively along Figure 1A A top view and a cross-sectional view of plane BB of , showing an example of a switch based on a phase change material;

[0024] Figure 2A and Figure 2B is a simplified partial view, respectively along Figure 2A A top view and a cross-sectional view of plane BB of , showing an example of a switch based on a phase change material according to an embodiment;

[0025] Figure 3 is a simplified partial isometric view showing an example of a phase change material based switch according to one embodiment;

[0026] Figure 4 is a simplified partial side view of an example of a transmit array antenna of the type to which the described embodiments are applicable as an example; and

[0027] Figure 5 According to an embodiment Figure 4 Simplified partial isometric view of the basic unit of the antenna transmit array. DETAILED DESCRIPTION

[0028] In the various drawings, the same features are designated by the same reference numerals. In particular, common structural and / or functional features in various embodiments may have the same reference numerals, and may be provided with the same structure, dimensions, and material properties.

[0029] For the sake of clarity, only the steps and elements useful for understanding the described embodiments are shown and described in detail. In particular, the circuits for controlling the switches based on phase change materials and the applications that can provide such switches have not been described in detail, and the described embodiments and variants are compatible with the common circuits for controlling the switches based on phase change materials and the common applications for implementing the switches based on phase change materials.

[0030] Unless otherwise specified, when referring to two elements being connected together, this means a direct connection without any intermediate elements except conductors, and when referring to two elements being coupled together, this means the two elements may be connected or they may be coupled via one or more other elements.

[0031] In the following description, when referring to absolute position qualifiers (such as "front", "back", "top", "bottom", "left", "right", etc.) or relative position qualifiers (such as "top", "bottom", "upper" and "lower", etc.), or direction qualifiers (such as "horizontal", "vertical", etc.), unless otherwise specified, they refer to the direction of the drawing.

[0032] Unless otherwise specified, "about," "approximately," "substantially," and "approximately" mean plus or minus 10%, preferably plus or minus 5%.

[0033] Figure 1A and Figure 1B are simplified partial views, including top view and along Figure 1A BB, showing an example of a switch 100 based on a phase change material. In the example shown, Figure 1A Plane BB is a vertical plane parallel to the conduction direction of the switch 100 .

[0034] exist Figure 1A and Figure 1B In FIG. 1 , the conduction direction of the switch 100 is parallel to the horizontal axis Oy, and the plane BB is parallel to a vertical plane Oyz orthogonal to the axis Ox.

[0035] In the example shown, the switch 100 includes conductive electrodes 101A and 101B. The conductive electrodes 101A and 101B of the switch 100 are intended to be connected to a radio frequency communication circuit, for example, which is not described in detail in the drawings. The conductive electrodes 101A and 101B are made of a conductive material, for example a metal such as copper or aluminum, or a metal alloy. In addition, the conductive electrodes 101A and 101B can have a single-layer or multi-layer structure.

[0036] although Figure 1A and Figure 1B This is not described in detail in order not to overload the drawing, but the conductive electrodes 101A and 101B of the switch 100 are, for example, located on top of and in contact with the upper surface of an electrically insulating layer (e.g. made of silicon dioxide (SiO2)), which covers the substrate. In this case, the substrate is, for example, a wafer or a piece of wafer made of a semiconductor material (e.g. silicon).

[0037] In the example shown, the switch 100 further comprises a region 103 made of a phase change material coupling the conductive electrodes 101A and 101B. Although this is not illustrated in detail in the figures, the region 103 of phase change material covers, for example, the upper surface of another electrically insulating layer, for example made of silicon dioxide, extending laterally between the electrodes 101A and 101B, for example flush with the upper surfaces of the electrodes 101A and 101B. In the example shown, the region 103 of phase change material extends on top of the upper surface of each conductive electrode 101A, 101B and contacts a portion of the upper surface of each conductive electrode 101A, 101B. For example, the region 103 of phase change material has a thickness of about 100 nm.

[0038] For example, region 103 of switch 100 is made of a so-called "chalcogenide" material, i.e. a material or alloy comprising at least one chalcogenide element, such as a material from the family of germanium telluride (GeTe), antimony telluride (SbTe) or germanium antimony telluride (GeSbTe, usually indicated by the acronym "GST"). As a variant, region 103 is made of vanadium dioxide (VO2).

[0039] In general, a phase change material is a material that is able to alternate between a crystalline phase and an amorphous phase under the influence of temperature changes, the amorphous phase having a higher resistance than the crystalline phase. In the case of the switch 100, this phenomenon is utilized, and when the material of the region 103 located between the conductive electrodes is in the amorphous phase, a blocking state is obtained that prevents the flow of current between the conductive electrodes 101A and 101B, and when the material of the region 103 is in the crystalline phase, a conductive state is obtained that allows the flow of current between the conductive electrodes 101A and 101B.

[0040] In the example shown, the switch 100 further comprises a waveguide 105 located in front of the region 103 of phase change material and extending laterally along a main direction substantially orthogonal to the conduction direction of the switch 100. Figure 1A and Figure 1B, the waveguide 105 of the switch 100 extends parallel to the axis Ox. For example, the waveguide 105 has a first end located in front of the upper surface of the region 103 of phase change material and a second end opposite the first end, which is intended to be irradiated by the laser source LS. For example, the radiation emitted by the laser source LS has a transverse magnetic polarization (TM) or a transverse electric polarization (TE).

[0041] In the example shown, the waveguide 105 comprises a central region 107 or core surrounded by an electrically insulating peripheral region 109. In the example shown, the central region 107 of the waveguide 105 extends parallel to the axis Ox. The central region 107 and the peripheral region 109 of the waveguide 105 are made of materials selected to obtain an optical index contrast, thereby being able to confine and guide the optical mode of interest emitted by the laser source LS. For example, the material of the central region 107 of the waveguide 105 has a higher optical index than the peripheral region 109. For example, the central region 107 of the waveguide 105 is made of silicon nitride and the peripheral region 109 is made of silicon dioxide.

[0042] Figure 1A The plane BB is substantially orthogonal to the propagation direction of the laser radiation in the waveguide 105. In the example shown, the propagation direction of the laser radiation in the waveguide 105 is parallel to the axis Ox. In the example shown, the peripheral region 109 of the waveguide 105 covers the surface of the central region 107 parallel to the propagation direction of the laser radiation (the side surface, the lower surface and the upper surface of the central region 107 of the waveguide 105 parallel to the axis Ox, as shown in FIG. Figure 1A and Figure 1B In this example, a portion of the peripheral region 109 of the waveguide 105 is formed along a vertical axis Oz orthogonal to the horizontal axes Ox and Oy from the surface of the central region 107 located in front of the region 103 of the phase change material (the lower surface of the central region of the waveguide 105, at Figure 1B The surface of the region 103 of the phase change material (the upper surface of the region 103 of the phase change material, in the direction of Figure 1B direction).

[0043] In the example shown, the central region 107 has a substantially rectangular cross section in a cross section along a plane BB orthogonal to the propagation direction of the laser radiation in the waveguide 105. For example, in a cross-sectional view along plane BB, the central region 107 has a width w (along the axis Ox) equal to about 300 nm and a height h (along the axis Oz) equal to about 350 nm. Furthermore, the central region 107 of the waveguide 105 is separated from the region 103 of phase change material by a distance g. In this example, the distance g is equal to the thickness of the portion of the peripheral region 109 between the central region 107 of the waveguide 105 and the region 103 of phase change material. For example, the distance g is approximately equal to 300 nm.

[0044] The waveguide 105 is, for example, of the single-mode type, that is, it is suitable for confining and guiding a single optical mode of each polarization type. For example, the waveguide 105 is more specifically suitable for confining and guiding a single optical mode selected from a zero-order transverse electric mode (TE0) parallel to the axis Oy and a zero-order transverse magnetic mode (TM0) parallel to the axis Oz. Since the modes TE0 and TM0 are orthogonal, they cannot couple with each other in the waveguide 105. The selection of the mode confined and guided between the mode TE0 and the mode TM0 by the waveguide 105 is determined by the polarization of the laser source LS. Therefore, in the case where the laser source LS emits radiation with a transverse magnetic polarization TM, the waveguide 105 is only suitable for confining and guiding the zero-order transverse magnetic mode TM0.

[0045] On the side of its end intended to be illuminated by the laser source LS, the waveguide 105 comprises, for example, an input coupling element, also referred to as the input surface of the waveguide 105. On the side of its end located in front of the region 103 of phase change material, the waveguide 105 may also comprise an output coupling element, also referred to as the output surface of the waveguide 105. The input coupling element may have a structure, for example a diffraction grating with a Bragg structure or any other coupling structure, capable of capturing the radiation emitted by the laser source LS and propagating it to the output surface.

[0046] Furthermore, the output surface of the waveguide 105 may have a structure that re-emits radiation propagating from the input surface into the region 103 of phase change material. Figure 1A and Figure 1B Although not described in detail, the output surface of the waveguide 105 can have the same or similar structure as its input surface.

[0047] Typically, in the example shown, the input surface and the output surface of the waveguide 105 are respectively capable of receiving and transmitting radiation in a direction orthogonal to the direction of propagation of radiation within the waveguide 105, for example in a direction parallel to the axis Oz. As a variant, at least one of the input surface and the output surface of the waveguide 105 may have a structure capable of receiving or transmitting radiation, respectively, in a direction parallel to the direction of propagation of radiation within the waveguide 105 (in the present example, parallel to the axis Ox).

[0048] In order to switch the switch 100 from the off state to the on state, for example, the region 103 is heated to a temperature T1 and for a time period d1 by means of a laser source LS via the waveguide 105. The temperature T1 and the time period d1 are selected to cause a phase change of the material of the region 103 from an amorphous phase to a crystalline phase. For example, the temperature T1 is higher than the crystallization temperature of the phase change material and lower than the melting temperature of the phase change material, and the time period d1 is in the range from 10 to 100 ns.

[0049] Conversely, in order to switch the switch 100 from the on state to the off state, for example, the region 103 is heated to a temperature T2 higher than the temperature T1 via the waveguide 105 by means of the laser source LS and for a time period d2 shorter than the time period d1. The temperature T2 and the time period d2 are selected to cause a phase change of the material of the region 103 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 time period d2 is about 10 ns.

[0050] For example, in the case of a laser source LS based on krypton fluoride, the laser source LS emits radiation having a wavelength approximately equal to 248 nm, for example in the form of pulses, in order to induce a transition of the material of the region 103 between an amorphous phase and a crystalline phase. -2 Pulses with a flux of about 185 mJ.cm are used, for example, to obtain a transition of the material of region 103 from an amorphous phase to a crystalline phase. -2 Another pulse of a flux of φ is used, for example, to obtain a transition of the material of region 103 from the crystalline phase to the amorphous phase.

[0051] A disadvantage of the switch 100 is that the laser radiation emitted by the source LS is not uniformly absorbed in the region 103 of the phase change material along the propagation direction of the radiation in the waveguide 105 (in this example, along the axis Ox). In the example of the switch 100, the laser radiation is mainly absorbed by a first portion 103N of the region 103 of the phase change material close to the laser source LS, the absorption of the laser radiation being lower in a second portion 103F of the region 103 of the phase change material, which is opposite to the first portion 103N and further away from the laser source LS than the portion 103N. The optical absorption of the laser radiation by the region 103 of the phase change material more precisely follows a decreasing exponential curve from the portion 103N to the portion 103F of the region 103.

[0052] Therefore, during the activation phase of the switch 100, the optical power absorbed by the second portion 103F of the region 103 may not be sufficient to cause a phase change of the material in the portion 103F. In the event that it is desired to switch the switch 100 from an on-state to an off-state, this may prevent the second portion 103F of the region 103 from changing phase from the crystalline phase to the amorphous phase, thereby undesirably allowing leakage current to flow between the conductive electrodes 101A and 101B of the switch 100.

[0053] The inventors have discovered that this phenomenon is due to the fact that the transverse magnetic mode TM of the laser signal used to activate the switch 100, which is confined and guided by the waveguide 105, is strongly absorbed by the phase change material of the region 103, resulting in much greater heating of the portion 103N than that observed in the portion 103F. To overcome this problem, the geometry of the waveguide 105 can be modified to confine and guide only the transverse electric mode TE, which is more lightly absorbed by the phase change material of the region 103 than the transverse magnetic mode TM. For example, the transverse magnetic mode TM exhibits approximately 2500 dB.cm due to the absorption of the phase change material of the region 103. -1 The loss of the transverse electric mode is about 500dB.cm -1 Compared. However, for equal laser power values, this will not result in sufficient heating of region 103 to induce a phase change. More generally, in the transverse electric mode TE as well as in the transverse magnetic mode TM, for this guiding configuration, the optical absorption follows a law of the exponentially decreasing type. However, it is preferred that the absorption follows a linear law in order to be able to modify the state of the phase change material of region 103.

[0054] Figure 2A and Figure 2B are simplified partial views, including top view and along Figure 2A 2 , a cross-sectional view of plane BB of FIG. 1 shows an example of a phase change material based switch 200 according to an embodiment.

[0055] Figure 2A and Figure 2B The switch 200 includes Figure 1A and Figure 1B The same elements as the switch 100 are shown in FIG. 1 . These common elements will not be described in detail below. Figure 2A and Figure 2B The switch 200 and Figure 1A and Figure 1B The switch 200 differs from the switch 100 in that the switch 200 includes a polarization rotator 205 instead of the waveguide 105 located in front of the region 103 of phase change material.

[0056] The polarization rotator 205 has the function of rotating the polarization of the laser signal used to activate the switch 200 above the region 103 of phase change material. In the example shown, the polarization rotator 205 is more particularly adapted to cause a polarization rotation equal to about 90° of the laser signal used to activate the switch 200 over a distance substantially equal to the width L of the region 103 of phase change material. The width L of the region 103 is considered to be parallel to the propagation direction of the control laser signal in the polarization rotator 205 (in the example shown, parallel to the axis Ox). In the example shown, the polarization rotator 105 is adapted to transfer from the transverse electric mode to the transverse magnetic mode over a distance substantially equal to the width L of the region 103.

[0057] In this example, the polarization rotator 205 is designed so that the signal is confined and guided only in the transverse electric mode TE at the input of the polarization rotator 205, i.e. near the portion 103N of the region 103, slightly absorbed by the region 103, and is strongly absorbed only in the transverse magnetic mode TM by the region 103 at the output of the polarization rotator, i.e. near the portion 103F of the region 103. This therefore ensures that the absorption of the laser signal used to control the switch 200 is better distributed between the portion 103N of the region 103 of the phase change material closest to the laser source LS and the portion 103F of the region 103 farthest from the laser source LS. In this example, the radiation emitted by the laser source LS has a transverse electric polarization TE.

[0058] In the example shown, the polarization rotator 205 includes a central region 207 or core surrounded by an electrically insulating peripheral region 209. The central region 207 and the peripheral region 209 of the polarization rotator 205 are made of materials selected to obtain an optical index contrast capable of confining and guiding the optical mode of interest emitted by the laser source LS. For example, the central region 207 of the polarization rotator 205 is made of silicon nitride and the peripheral region 209 is made of silicon dioxide.

[0059] Figure 2A The plane BB is substantially orthogonal to the propagation direction of the laser radiation in the polarization rotator 205 (in the example shown, orthogonal to the axis Ox and parallel to the plane Oyz). In the example shown, the peripheral region 209 of the polarization rotator 205 covers the surface of the central region 207 parallel to the propagation direction of the laser radiation (in the example shown). Figure 2A and Figure 2B In this example, a portion of the peripheral region 209 of the polarization rotator 205 extends along the axis Oz from the surface of the central region 207 located in front of the region 103 of phase change material (in the direction of the side surface, the lower surface and the upper surface of the central region 207 of the polarization rotator 205 parallel to the axis Ox). Figure 2B The lower surface of the central region 207 of the polarization rotator 205 extends vertically to the surface of the region 103 of the phase change material opposite to the conductive electrodes 101A and 101B. Figure 2B direction, the upper surface of the region 103 of the phase change material).

[0060] In the example shown, in a cross-sectional view along plane BB, the central region 207 of the polarization rotator 205 has an asymmetric cross-section. More specifically, in this example, the central region 207 of the polarization rotator 205 has an L-shaped cross-section. Figure 2B In the direction of:

[0061] a vertical strip of L formed by a cross section of the central zone 207 of the polarization rotator 205, parallel to the axis Oz, having a height h1 along the axis Oz and a width w1 along the axis Oy; and

[0062] A horizontal strip of L formed by a cross section of the central zone 207 of the polarization rotator 205, parallel to the axis Oy, having a height h2 along the axis Oz and a width w2 along the axis Oy.

[0063] In this example, the height h1 is greater than the height h2. In addition, the width w1 is, for example, greater than or equal to the width w2.

[0064] For example, the cross section of the central region 207 of the polarization rotator 205 has a constant shape and size along the axis Ox in front of the region 103 of phase change material. The cross section of the central region 207 of the polarization rotator 205 is constant, for example, along the entire length of the polarization rotator 205.

[0065] Furthermore, the central region 207 of the polarization rotator 205 is separated from the region 103 of phase change material by a distance g1. In this example, the distance g1 is equal to the thickness of the portion of the peripheral region 209 between the central region 207 of the polarization rotator 205 and the region 103 of phase change material.

[0066] The following table [Table 1] provides examples of values ​​of heights h1 and h2, widths w1 and w2, and distance g1 according to the width L of the region 103 of phase change material along the axis Ox (i.e., perpendicular to the conduction axis Oy of the switch 200 and parallel to the propagation direction of the laser signal in the polarization rotator 205). Two different examples are provided for the same width L of the region 103, equal to about 100 μm.

[0067] [Table 1]

[0068] L(μm) g1(nm) h1(nm) h2(nm) w1(nm) w2(nm) 100 290 450 225 400 75 100 250 250 100 150 125 80 400 250 125 210 50 65 100 1,000 500 500 500 50 100 750 300 700 150 30 250 400 200 300 125 10 45 500 250 300 225

[0069] As an example, the following table [Table 2] provides the minimum and maximum values ​​of each dimension h1, h2, w1 and w2 and the distance g1 of the central region 207 of the polarization rotator 205, as a non-limiting example, the width L of the region 103 of the phase change material is in the range of 10 to 100 μm.

[0070] [Table 2]

[0071] Size or distance Minimum Maximum g1(nm) 45 400 w1(nm) 150 700 w2(nm) 50 500 h1(nm) 250 1,000 h2(nm) 100 <h1

[0072] However, the examples given above are not limiting, and a person skilled in the art is able to define the values ​​of the dimensions h1, h2, w1 and w2 of the central region 207 of the polarization rotator 205 and the value of the distance g1 according to the width L of the region 103 of the phase change material. Digital simulation tools can be used for this purpose. For example, the distance g1 and the height h1 may be limited due to the thickness of the material layers deposited during the manufacturing steps of the switch 200.

[0073] Combination of the above Figure 2A and Figure 2B An advantage of the described switch 200 is that the presence of the polarization rotator ensures that the laser signal used to control the switch 200 is substantially uniformly absorbed by the phase change material of the region 103. More specifically, in the case of the switch 200, only the slightly absorbed transverse electric mode TE is present near the input of the polarization rotator 205 (perpendicularly aligned with the portion 103N of the region 103), while only the strongly absorbed transverse magnetic mode TM is present near the output of the polarization rotator 205 (perpendicularly aligned with the portion 103F of the region 103F). Figure 1A and Figure 1B Compared to the switch 100 of FIG. 1 , this can avoid that a portion of the region 103 of the phase change material, such as the portion 103F farthest from the laser source LS, does not change phase when the switch is operated.

[0074] Figure 3 is a simplified partial isometric view of an example of a phase change material based switch 300 according to one embodiment.

[0075] Figure 3 The switch 300 includes Figure 2A and Figure 2B The same elements as the switch 200 are shown in FIG. 1 . These common elements will not be described in detail below. Figure 3 The switch 300 and Figure 2A and Figure 2B The switch 300 differs from the switch 200 in that the switch 300 comprises a polarization rotator 305 having a variable cross-section along the laser signal propagation axis (axis Ox in the example shown).

[0076] Polarization rotator 305 of switch 300 performs similar or identical functions to polarization rotator 205 of switch 200. In particular, polarization rotator 305 is adapted to induce a polarization rotation between a transverse electric mode TE and a transverse magnetic mode TM of a laser signal used to activate switch 300 between an input surface, e.g., vertically aligned with portion 103N of region 103, and an output surface, e.g., vertically aligned with portion 103F of region 103F.

[0077] In the example shown, the polarization rotator 305 comprises a central region 307, for example similar to the central region 207 of the polarization rotator 205, surrounded by an electrically insulating peripheral region, for example similar to the peripheral region 209 of the polarization rotator. In order not to overload the drawing, Figure 3 The peripheral area of ​​the polarization rotator 305 is not shown.

[0078] exist Figure 3 In the example shown, the central region 307 of the polarization rotator 305 includes three portions 307A, 307B, and 307C. In this example, portions 307A and 307C of the central region 307 of the polarization rotator 305 are located in front of portions 103N and 103F of the region 103 of phase change material, respectively. More specifically, in this example:

[0079] - the portion 307A comprises an upper region opposite the conductive electrodes 101A and 101B, the cross section of which narrows along the axis Ox towards the portion 307B of the region 307, and a lower region between the upper region of the portion 307A and the region 103, the cross section of which is substantially constant along the axis Ox;

[0080] - portion 307B comprises an upper region opposite conductive electrodes 101A and 101B, the cross section of which is substantially constant along axis Ox, and a lower region between the upper region of portion 307B and region 103, the cross section of which narrows along axis Ox towards portion 307C of region 307; and

[0081] The portion 307C has a cross section that widens along the axis Ox from the portion 307B of the region 307 towards the portion 103F of the region 103 .

[0082] However, this example is not limiting, and those skilled in the art can provide a method having a configuration different from the above configuration based on the instructions of the present disclosure. Figure 3 The central area 307 of the geometric shape in question.

[0083] The switch 300 has the same or similar advantages as the switch 200. Due to the presence of the polarization rotator 305, the switch 300 is particularly capable of being more efficient than previously described. Figure 1A and Figure 1B The described situation of switch 100 heats the phase change material of region 103 more evenly.

[0084] Figure 4 is a simplified partial side view of one example of a transmit array antenna 400 of the type for which the described embodiments are applicable.

[0085] The antenna 400 generally includes one or more primary sources 401 (in the example shown, a single source 401) that illuminate an emission array 403. The source 401 can have any polarization, such as linear or circular. The array 403 includes a plurality of basic units 405, for example arranged in a matrix of rows and columns. Each unit 405 generally includes a first antenna element 405a and a second antenna element 405b, the first antenna element 405a being located on one side of a first surface of the array 403 arranged in front of the primary source 401, and the second antenna element 405b being located on a side of the second surface of the array 403 opposite to the first surface. For example, the second surface of the array 403 faces the emission medium of the antenna 400.

[0086] In transmit mode, each unit 405 is capable 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 In receive mode, each unit 405 is capable of receiving electromagnetic radiation on its second antenna element 405b and is capable of receiving electromagnetic radiation with the same phase shift. The radiation is re-emitted from its first antenna element 405a towards the source 401. The radiation re-emitted by the first antenna element 405a is focused on the source 401, for example.

[0087] The characteristics of the beam generated by the antenna 400 , in particular its shape and its direction of maximum transmission (or pointing direction), depend on the values ​​of the phase shifts respectively introduced by the different elements 405 of the array 403 .

[0088] Transmit array antennas have the advantages of good energy efficiency, relative simplicity, low cost and small size. This is especially because the transmit array can be manufactured in planar technology, usually on a printed circuit board.

[0089] Here, more specifically, a reconfigurable transmit array antenna 403 is considered. When the base units 405 can be individually electronically controlled to modify their phase shift values The transmit array 403 is considered to be reconfigurable, 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 part of the antenna with the aid of motor drive elements.

[0090] Figure 5 According to an embodiment Figure 4 An isometric, simplified and partial view of a basic unit 405 of a transmit array 403 of an antenna 400.

[0091] In the example shown, the first antenna element 405a of the base unit 405 includes a patch antenna 410 adapted to capture electromagnetic radiation emitted by the source 401, and the second antenna element 405b includes another patch antenna 412 adapted to emit a phase-shifted signal to the exterior of the antenna 400. In the example shown, the base unit 405 also includes a ground plane 414 between the patch antennas 410 and 412.

[0092] Antenna 410, ground plane 414 and antenna 412 are formed in three consecutive metallization layers, stacked and separated from each other by a dielectric layer (e.g. made of quartz). For example, ground plane 414 is separated from each of antennas 410 and 412 by a dielectric material thickness of about 200 μm.

[0093] In the example shown, center conductive via 416 connects antenna 410 to antenna 412. More specifically, in Figure 5 In the direction of , the lower end of the through hole 416 contacts the upper surface of the antenna 410, and the upper end thereof contacts the lower surface of the antenna 412. The central conductive through hole 416 is electrically insulated from the ground plane 414. In the illustrated example, the ground plane 414 includes a circular hole having a diameter greater than the diameter of the through hole 416, so that the through hole 416 can pass through the ground plane 414 without the through hole 416 contacting the ground plane 414. For example, the diameter of the central conductive through hole 416 is approximately equal to 80 μm.

[0094] In the example shown, the antenna 412 includes a four-sided conductive plane 440. For example, the conductive plane 440 is more accurately rectangular, or as shown in FIG. Figure 5 In the example shown, it is substantially square.

[0095] In the example shown, the conductive plane 440 includes an opening 442 that separates a central region 440C of the conductive plane 440 from a peripheral region 440P in the conductive plane 440. In this example, the opening 442 is substantially annular, for example having a rectangular or square shape.

[0096] In the example shown, the central conductive via 416 is in contact with a central region 440C of the conductive plane 440. More precisely, in this example, the upper end of the via 416 is substantially connected to the center of the lower surface of the region 440C. The central region 440C of the conductive plane 440, which is laterally delimited by the annular opening 442, forms, for example, an input terminal of the antenna 412.

[0097] The antenna 412 further includes a first switching element C1 and a second switching element C2, each of which couples the central region 440C to the peripheral region 440P of the conductive plane 440. More specifically, Figure 5In the example shown, the first switch element C1 and the second switch element C2 contact the peripheral region 440P in diametrically opposed regions relative to the central conductive via 416. In this example, the switch elements C1 and C2 and the conductive via 416 are located on the same straight line parallel to one side of the conductive plane 440. In this example, the switch C1 is positioned substantially vertically relative to the horizontal branch of the U formed by the slot 442.

[0098] The switch elements C1 and C2 are controlled inversely, that is, if one of the switches C1, C2 is turned on, the other switch of C1, C2 is turned off. This enables the second antenna element 405b of the base unit 405 to be in two phase states The phase states of 0° and 180° respectively correspond to the case where switch C1 is off and switch C2 is on, and the case where switch C1 is on and switch C2 is off.

[0099] Each switching element C1, C2 of the basic unit 405 is formed, for example, by one of the switches 200 and 300 discussed previously. In this case, the fact that a laser source LS is used to control the switches C1 and C2 of the antenna element 405b has the advantage of reducing the number of conducting control lines. Compared to switches made of phase change material, for example controlled by direct heating (for example by a current flowing through the phase change material) or by indirect heating (for example by a current flowing through a heating element electrically insulated from the phase change material), which use two control lines, one for applying a control potential and the other for applying a reference potential, only a single optical control line, for example a waveguide having a structure similar to the waveguide 105 and arranged between the laser source and the polarization rotator 205 or 305 of each switch C1, C2, is used to control the switching of each switch C1, C2.

[0100] Another advantage of switches C1 and C2 is that their capacitance C in the off state off Compared to conventional indirect heating switches, conventional indirect heating switches typically include a heating element made of a conductive material (such as metal) electrically insulated from a phase change material.

[0101] For example, in the emission array 403, a different laser source LS may be used to control each switch C1, C2 of each second antenna element 405b, the emission of the laser source LS of the emission array 403 being controlled by a control circuit (not shown). For example, the laser source LS is of the "integrated" type, that is, it forms part of the same chip as the switch with which it is associated.

[0102] As a variant, a plurality of switches C1, C2 may be provided that use a single laser source LS to control the second antenna elements 405b of the transmit array 403. In this case, for example, each second antenna element 405b may be associated with an optical switch for controlling the anti-phase switches C1 and C2, or with a "1 to N" type multiplexer suitable for controlling a plurality of switches C1, C2 in a plurality of second antenna elements 405b, where N is an integer greater than 2.

[0103] The advantages of switches C1 and C2 based on phase change materials are that they can operate at power levels at least as high as switches typically used in base units of antennas with reconfigurable transmit or reflect arrays, while exhibiting better linearity. In addition, switches C1 and C2 exhibit excellent stability over a frequency range of the order of one terahertz.

[0104] Furthermore, the firing array 403 including cells 405 integrating switches C1 and C2 advantageously has lower power consumption than, for example, a current firing array including components such as pin diodes or varactors.

[0105] Various embodiments and variations have been described. Those skilled in the art will appreciate that certain features of these various embodiments and variations may be combined, and that other variations will occur to those skilled in the art. In particular, the geometry and size of the central regions 207 and 307 of the polarization rotators 205 and 305 may be adjusted by those skilled in the art based on the teachings of the present disclosure, for example, depending on the target application.

[0106] Furthermore, although an example of a basic unit 405 having two switches made of phase change materials C1 and C2 has been described, a person skilled in the art may convert the described method to any number of switches made of phase change materials. For example, in the case where it is desired to form a reconfigurable basic unit with more than two different phase states, more than two switches made of phase change materials may be provided.

[0107] In addition, although only the example of application to the transmitting array antenna is described above, Figure 2A , Figure 2B and Figure 3 The described optically controlled switch based on phase change material may have other applications. More generally, such a switch may be used in any application where it is possible to control a switch by reducing the number of electrical connection tracks. For example, such a switch may be integrated in reflect array antennas, filters, phase shift circuits, etc., and more generally, may be integrated into any type of application that uses a switch.

[0108] In particular, based on the teachings of this disclosure, it is within the capabilities of a person skilled in the art to convert the described embodiments to the case of a reflectarray antenna.

[0109] Finally, based on the functional indications given above, the actual implementation of the described embodiments and variants is within the capabilities of a person skilled in the art. In particular, the described embodiments are not limited to the specific examples of materials and dimensions mentioned in the present disclosure. Furthermore, the embodiments are not limited to the combination of Figure 5 The examples described herein are not based on geometries of patch antennas 410 and 412, but are more generally applicable to any type of antenna geometry.

Claims

1. A switch (200; 300) based on a phase change material, comprising: - a region (103) made of said phase change material, coupling the first and second conducting electrodes (101A, 101B) of said switch; and - a rotator (205; 305) of the polarization of the laser signal for activating the switch, located in front of the surface of the area made of the phase-change material.

2. The switch (200; 300) according to claim 1, wherein: The polarization rotator (205; 305) comprises a central region (207; 307) made of a first material, which is surrounded by a peripheral region (209; 309) made of a second material having a lower optical index than the first material.

3. The switch (200; 300) according to claim 1 or 2, wherein: The polarization rotator (205; 305) is adapted to induce a rotation of the polarization of the laser signal between an input surface and an output surface opposite to the input surface for activating a switch between a transverse electric mode and a transverse magnetic mode.

4. The switch (200) according to claim 2 or 3, wherein: The central region (207) has an asymmetric cross section along the propagation direction of the laser signal in the polarization rotator (205).

5. The switch (200) according to claim 4, wherein: The cross-section of the central region (207) is constant along the entire length of the polarization rotator (205).

6. The switch (200) according to claim 4 or 5, wherein: The cross section of the central region (207) has an L-shape in a plane orthogonal to the propagation direction of the laser signal.

7. The switch (300) according to claim 2 or 3, wherein: The cross section of the central region (307) varies along the propagation direction of the laser signal in the polarization rotator (205).

8. The switch (200; 300) according to any one of claims 1 to 7, wherein: The first and second conductive electrodes (101A, 101B) form part of an antenna element (405a) of a cell (405) of a transmit array (403) or a reflective array.

9. A unit (405) of a transmitting array (403) or a reflecting array, comprising at least one switch (200; 300) according to any one of claims 1 to 8.

10. A transmitting array (403) or a reflecting array, comprising: - a plurality of units (405) according to claim 9; - one or more laser sources (LS); as well as - Circuitry for controlling said laser source.

11. The array (403) of claim 10, wherein: Each laser source (LS) forms part of the same chip as each switch (200; 300) with which it is associated.

12. An antenna (400) comprising a transmit array (403) or a reflective array according to claim 10 or 11, and at least one source (401) configured to illuminate a surface of the array.

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