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-an optical coupler (201) for activating 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 used 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 phase change switches have 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] - An optical coupler for the laser signal that activates the switch, located in front of the surface of the area made of said phase change material.

[0008] According to one embodiment, the optical coupler comprises a first waveguide and a second waveguide stacked in front of the surface, the second waveguide being interposed between the first waveguide and the region made of the phase change material.

[0009] According to one embodiment, the first waveguide and the second waveguide each comprise 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.

[0010] According to one embodiment, the central areas of the first and second waveguides are stacked in front of each other and have the same pattern vertically aligned with the areas made of said phase change material.

[0011] According to one embodiment, the central areas of the first and second waveguides do not have the same pattern as the areas made of said phase change material.

[0012] According to one embodiment, the central region of the first waveguide has substantially the same geometry and dimensions as the central region of the second waveguide.

[0013] According to one embodiment, the optical coupler is an adiabatic coupler.

[0014] According to one embodiment, the first waveguide and the second waveguide comprise an output surface and an input surface, respectively, each surface having a tapered shape in a top view.

[0015] According to one embodiment, the laser signal is primarily confined and guided by the first waveguide at the input end of the optical coupler and primarily confined and guided by the second waveguide at the output end of the optical coupler.

[0016] 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.

[0017] One embodiment provides a unit of a transmit array or a reflective array comprising at least one switch as described.

[0018] One embodiment provides a transmitting array or a reflecting array, comprising:

[0019] - a plurality of units such as described;

[0020] - one or more laser sources; and

[0021] -Circuitry for controlling the laser source.

[0022] According to one embodiment, each laser source forms part of the same chip as each switch with which it is associated.

[0023] One embodiment provides an antenna comprising a transmit array or a reflect array as described and at least one source configured to illuminate a surface of the array. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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:

[0025] 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;

[0026] Figure 2A , Figure 2B and Figure 2C are simplified partial views, including top view, Figure 2A The cross-sectional view of plane BB and along Figure 2A A cross-sectional view of plane CC of FIG. 1 , showing an example of a switch based on a phase change material according to an embodiment;

[0027] Figure 3is a simplified partial side view of an example of a transmit array antenna of the type to which the embodiments described are applicable as an example;

[0028] Figure 4 According to an embodiment Figure 3 A simplified partial isometric view of a basic unit of a transmit array of an antenna; and

[0029] Figure 5 is a simplified partial top view showing an example of a phase change material based switch according to one embodiment. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] Unless otherwise specified, "about," "approximately," "substantially," and "approximately" mean plus or minus 10%, preferably plus or minus 5%.

[0035] 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 .

[0036] 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.

[0037] 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, such as 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.

[0038] although Figure 1A and Figure 1B Although this is not described in detail in order not to overload the drawing, 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)) covering a substrate. In this case, the substrate is, for example, a wafer or a piece of a wafer made of a semiconductor material (e.g. silicon).

[0039] 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.

[0040] For example, region 103 of switch 100 is made of a "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).

[0041] 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.

[0042] 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 (TM) polarization or a transverse electric (TE) polarization.

[0043] 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 material of 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.

[0044] 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 1BThe 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).

[0045] In the example shown, the central region 107 has a substantially rectangular cross-sectional profile 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 section 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.

[0046] 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.

[0047] 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 such as a diffraction grating with a Bragg structure or any other coupling structure capable of capturing the radiation emitted by the laser source and propagating it to the output surface.

[0048] 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.

[0049] 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 propagation direction of the radiation in the waveguide 105 (e.g., 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 respectively capable of receiving or transmitting radiation in a direction parallel to the propagation direction of the radiation in the waveguide 105 (in the present example, parallel to the axis Ox).

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 the present 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 lighter 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 specifically follows a decreasing exponential curve from the portion 103N to the portion 103F of the region 103.

[0054] 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.

[0055] The inventors have discovered that this phenomenon stems from 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.

[0056] Figure 2A , Figure 2B and Figure 2C are simplified partial views, including top view, Figure 2A The cross-sectional view of plane BB and along Figure 2A , a cross-sectional view of plane CC of , shows an example of a phase change material based switch 200 according to an embodiment.

[0057] Figure 2A , Figure 2B and Figure 2C 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 , Figure 2B and Figure 2C The switch 200 and Figure 1A and Figure 1BThe switch 100 differs in that the switch 200 comprises an optical coupler 201. In this example, the optical coupler 201 comprises two stacked waveguides 205-1 and 205-2 in front of the region 103 of phase change material.

[0058] In the example shown, the waveguide 205-2 is interposed between the waveguide 205-1 and the phase change material region 103. In this example, the waveguide 205-1, which is farthest from the region 103 of the phase change material, is intended to receive a laser signal from the source LS for activating the switch 200, and the waveguide 205-2, which is closer to the region 103 of the phase change material than the waveguide 205-1, is intended to be optically coupled to the waveguide 205-1 by the evanescent field. For example, the waveguides 205-1 and 205-2 form a directional optical coupler 201.

[0059] refer to Figure 2B and Figure 2C In the remainder of this disclosure, waveguides 205-1 and 205-2 will sometimes be referred to by the qualifiers "upper" and "lower", respectively.

[0060] In this example, the optical coupler 201 is designed so that the signal at the input end of the optical coupler 201 (i.e., near the portion 103N of the region 103) is mainly confined and guided in the upper waveguide 205-1, and the signal at the output end of the optical coupler (i.e., near the portion 103F of the region 103) is mainly confined and guided in the lower waveguide 205-2. For example, the waveguides 205-1 and 205-2 each confine and guide the transverse magnetic mode TM of the laser signal emitted by the source LS for activating the switch 200. For example, due to the absorption of the phase change material of the region 103, the transverse magnetic mode TM exhibits a loss of about 500 dB.cm for the upper waveguide 205-1. -1 , while for the lower waveguide 205-2 it is about 2500dB.cm -1 By injecting the laser signal for controlling the switch 200 into the upper waveguide 205-1 coupled to the lower waveguide 205-2 in vertical alignment with the region 103 of phase change material, the optical power is better distributed between the portion 103N of the region 103 of 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 magnetic polarization TM.

[0061] In the example shown, for example, the structure of each waveguide 205-1, 205-2 is similar to that previously described with respect to Figure 1A and Figure 1BThe structures of the waveguides 105 described are the same or similar. In the example shown, each waveguide 205-1, 205-2 includes 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 selected materials 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 207-1, 207-2 of each waveguide 205-1, 205-2 is made of silicon nitride, and the peripheral region 209 is made of silicon dioxide.

[0062] In the example shown, the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2 are stacked in front of each other and have the same pattern vertically aligned with the region 103. However, in this example, the regions 207-1, 207-2 are not located in front of each other and / or do not have the same pattern that is not aligned with the region 103 of the phase change material. This makes it possible to ensure that the optical coupling between the waveguides 205-1 and 205-2 occurs mainly in front of the region 103. This further makes it possible to limit optical reflections due to sudden or sharp changes in the optical index, which would be observed, for example, if the region 207-2 of the lower waveguide 205-2 would suddenly interrupt the vertical alignment with the region 207-1 of the upper waveguide 205-1.

[0063] Figure 2A The plane BB is substantially orthogonal to the propagation direction of the laser radiation in the waveguides 205-1 and 205-2 in front of the region 103 (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 waveguides 205-1 and 205-2 covers the surface of the central region 207-1 and 207-2 parallel to the propagation direction of the laser radiation (the side surfaces, the lower surface and the upper surface of the central region 207-1 and 207-2 of the waveguides 205-1, 205-2 parallel to the axis Ox, in the example shown). Figure 2A , Figure 2B and Figure 2C In this example, a portion of the peripheral region 209 of the waveguides 205-1 and 205-2 is formed along the axis Oz from the surface of the central region 207-1 located in front of the lower waveguide 205-2 (in the Figure 2B In the direction of the phase change material, the lower surface of the central region 207 of the upper waveguide 205-1 extends vertically to the surface of the central region 207-2 of the lower waveguide 205-2 opposite to the region 103 of the phase change material ( Figure 2BIn addition, another portion of the peripheral region 209 of the waveguides 205-1 and 205-2 extends along the axis Oz from the surface of the central region 207-2 located in front of the region 103 of the phase change material (in the direction of Figure 2B The lower surface of the central region 207-2 of the lower waveguide 205-2 extends vertically to the surface of the region 103 of the phase change material opposite to the conductive electrodes 101A and 101B (in Figure 2B direction, the upper surface of the region 103 of the phase change material).

[0064] In the example shown, the central regions 207-1 and 207-2 each have a substantially rectangular cross section in a cross section along plane BB. For example, the central region 207-1 of the upper waveguide 205-1 has a cross section having the same shape and size as the cross section of the central region 207-2 of the lower waveguide 205-2 within a manufacturing error range. More specifically, Figure 2B In the direction of the center region 207-1, 207-2 of each waveguide 205-1, 205-2 has the same width w1 along the axis Ox, and has the same height h1 along the axis Oz. However, this example is not restrictive, and as a variation, the cross section of the center region 207-2 of the lower waveguide 205-2 may have a different shape and size from the cross section of the center region 207-1 of the upper waveguide 205-1.

[0065] In addition, 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 g1. In this example, the distance g1 is equal to the thickness of the portion of the peripheral region 209 between the central region 207-1 of the waveguide 205-1 and the central region 207-2 of the waveguide 205-2. In addition, the central region 207-2 of the waveguide 205-2 is separated from the region 103 of the phase change material by a distance g2. In this example, the distance g2 is equal to the thickness of the portion of the peripheral region 209 between the central region 207-2 of the waveguide 205-2 and the region 103 of the phase change material.

[0066] The following table [Table 1] provides examples of values ​​of height h1, width w1, and distances g1 and g2 according to the width L of the phase change material region 103 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 optical coupler 201). The width L of the region 103 of phase change material is considered to be parallel to the propagation direction of the laser signal used to control the switch 200 in the optical coupler 201 that is vertically aligned with the region 103 (in the example shown, parallel to the axis Ox).

[0067] [Table 1]

[0068] L(μm) g1(nm) g2(nm) h1(nm) w1(nm) 100 600 300 300 1,000 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

[0069] As an example, the following table [Table 2] provides the minimum and maximum values ​​of each dimension h1, w1 and distances g1 and g2 of the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2, as a non-limiting example, the width L of the region 103 of phase change material is in the range of 30 to 100 μm.

[0070] [Table 2]

[0071]

[0072]

[0073] 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 and w1 of the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2 and the values ​​of the distances g1 and g2 as a function of the width L of the region 103 of the phase change material. Digital simulation tools can be used for this purpose. For example, the distances g1 and g2 and the height h1 may be limited due to the thickness of the material layers deposited during the manufacturing steps of the switch 200.

[0074] Combination of the above Figure 2A , Figure 2B and Figure 2C An advantage of the switch 200 discussed is that the presence of the optical coupler 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 magnetic mode TM in the upper waveguide 205-1 appears near the input end of the optical coupler 201 (vertically aligned with the portion 103N of the region 103), while only the strongly absorbed transverse magnetic mode TM in the lower waveguide 205-2 appears near the output end of the optical coupler 201 (vertically aligned with the portion 103F of the region 103). Figure 1A and Figure 1B Compared to the switch 100 of FIG. 1 , this can prevent a portion of the region 103 of the phase change material, such as the portion 103F farthest from the laser source LS, from changing phase during switching control.

[0075] Figure 3 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.

[0076] 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.

[0077] 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.

[0078] 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 introduced respectively by the individual elements 405 of the array 403 .

[0079] 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.

[0080] 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.

[0081] Figure 4 According to an embodiment Figure 3 A simplified partial isometric view of one of the base units 405 of the transmit array 403 of the antenna 400.

[0082] 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.

[0083] 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.

[0084] In the example shown, center conductive via 416 connects antenna 410 to antenna 412. More specifically, in Figure 4 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.

[0085] In the example shown, the antenna 412 includes a four-sided conductive plane 440. For example, the conductive plane 440 has a rectangular shape more precisely, or, as shown in FIG. Figure 4 In the example shown, it is substantially square in shape.

[0086] 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.

[0087] In the example shown, the central conductive via 416 is in contact with the central region 440C of the conductive plane 440. More specifically, 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 bounded by the annular opening 442, forms, for example, an input terminal of the antenna 412.

[0088] 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 4In 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.

[0089] 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 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.

[0090] Each switching element C1, C2 of the basic unit 405 is formed, for example, by the previously described switch 200. 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. In contrast to switches made of phase-change material controlled by direct heating (e.g. by a current flowing through the phase-change material) or by indirect heating (e.g. by a current flowing through a heating element electrically insulated from the phase-change material), which use two control lines, one applying a control potential and the other applying a reference potential, a single optical control line, for example the upper waveguide 205-1 of the optical coupler of each switch C1, C2, is used to control the switching of each switch C1, C2.

[0091] 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) that is electrically insulated from a phase change material.

[0092] For example, in the emission array 403, it may be provided that each switch C1, C2 using a different laser source LS is controlled for 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.

[0093] 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.

[0094] 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 those typically used in base units of reconfigurable transmit arrays or reflect array antennas, while providing better linearity. In addition, switches C1 and C2 provide excellent stability over a frequency range of the order of one terahertz.

[0095] 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.

[0096] Figure 5 is a simplified partial top view of an example of a phase change material based switch 500 according to one embodiment.

[0097] Figure 5 The switch 500 includes Figure 2A , Figure 2B and Figure 2C The same elements as the switch 200 are shown in FIG. 1 . These common elements will not be described in detail below. Figure 5 The switch 500 with Figure 2A , Figure 2B and Figure 2C The switch 500 is different in that the optocoupler 201 of the switch 500 is of the "adiabatic" type.

[0098] In the example shown, the output surface of the upper waveguide 205-1 and the input surface of the waveguide 205-2 are both tapered in top view. More specifically, in this example, the central region 207-1 of the upper waveguide 205-1 is wider in vertical alignment with the portion 103N of the region 103 than in vertical alignment with the portion 103F, and the central region 207-2 of the lower waveguide 205-2 is wider in vertical alignment with the portion 103F of the region 103 than in vertical alignment with the portion 103N. This enables adiabatic coupling to be formed between the upper waveguide 205-1 and the lower waveguide 205-2.

[0099] In the example shown, the propagation axes of radiation within the waveguides 205-1 and 205-2 are substantially parallel to each other and to the axis Ox, and the waveguides 205-1 and 205-2 are each, for example, substantially rectilinear.

[0100] 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 dimensions of the central regions 207-1 and 207-2 of the waveguides 205-1 and 205-2 may be adjusted by those skilled in the art based on the teachings of the present disclosure, for example as a function of the target application. For example, the central region 207-2 of the lower waveguide 205-2 may begin vertically aligned with the portion 103N of the region 103 of phase change material and / or end vertically aligned with the portion 103F of the region 103.

[0101] Furthermore, although an example of a basic unit 405 comprising two switches of phase change material 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 material. 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 material may be provided.

[0102] In addition, although the above only describes an example applied to a transmitting array antenna, Figure 2A , Figure 2B and Figure 2C The described optically controlled switch made of phase change material may have other applications. More generally, such a switch may be used in any application where a reduction in the number of electrical connection tracks can be used to control a switch. For example, such a switch may be integrated into reflective array antennas, filters, phase shifter circuits, etc., and more generally, into any type of application that uses a switch.

[0103] 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.

[0104] In addition, based on the teachings of this disclosure, those skilled in the art can set each of the phase change switches C1 and C2 of the basic unit 405 to be Figure 5 The switch 500 is the same or similar.

[0105] 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 4 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; 500) 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 - an optical coupler (201) for the laser signal activating the switch, located in front of the surface of the area made of the phase change material, The optical coupler (201) comprises a first waveguide and a second waveguide (205-1, 205-2) stacked in front of the surface, and the second waveguide (205-2) is between the first waveguide (205-1) and the region (103) made of the phase change material.

2. The switch (200; 500) according to claim 1, wherein: The first and second waveguides (205-1, 205-2) each include a central region (207-1, 207-2) made of a first material, the central region being surrounded by a peripheral region (209) made of a second material having an optical index lower than that of the first material.

3. The 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 stacked in front of each other and have the same pattern vertically aligned with the region (103) made of the phase change material.

4. The 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 have the same pattern as the region (103) made of the phase change material.

5. The switch (200) according to any one of claims 2 to 4, wherein: The central region (207-1) of the first waveguide (205-1) has substantially the same geometry and dimensions as the central region (207-2) of the second waveguide (205-2).

6. The switch (500) according to claim 1 or 2, wherein: The optical coupler (201) is an adiabatic coupler.

7. The switch (500) according to claim 6, wherein: The first and second waveguides (205-1, 205-2) include an output surface and an input surface, respectively, each surface having a tapered shape in a top view.

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

9. The switch (200; 500) according to any one of claims 1 to 8, 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.

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

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

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

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

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