Phase-change material-based switch

Abstract

Phase-change material-based switch This description relates to a phase-change material-based switch (200) comprising: – a region (103) of said phase-change material connecting first (101A) and second (101B) conduction electrodes of the switch; – a waveguide (105) located above the region of said phase-change material and comprising a central region (107) of a first material having a first refractive index surrounded by a peripheral region (109) of a second material having a second refractive index lower than the first refractive index; and – a region (201) of a third material having a third refractive index lower than the second refractive index and located in the peripheral region of the waveguide above a first face of the central region of the waveguide opposite the region of said phase-change material.Figure for the abridged version: Fig. 2B.

Description

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

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

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

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

[0004] It would be desirable to overcome all or part of the disadvantages of existing phase-change material switches.

[0005] To this end, one embodiment provides a switch based on a phase-change material comprising: - a region in said phase-change material connecting the first and second conduction electrodes of the switch; - a waveguide located directly above the region in said phase-change material and comprising a central region in a first material having a first refractive index surrounded by a peripheral region in a second material having a second refractive index lower than the first refractive index; and - a region in a third material having a third refractive index lower than the second refractive index and located in the peripheral region of the waveguide directly above a first face of the central region of the waveguide opposite the region in said phase-change material.

[0006] According to one embodiment, the region in said third material extends from the first face of the central region of the waveguide.

[0007] According to one embodiment, the region in said third material is a cavity at least partially filled with one or more solid, liquid or gaseous substances, preferably a cavity filled with air.

[0008] According to one embodiment, the region in said third material has, in top view, a tapered shape flaring out along a propagation direction of an optical signal for controlling the switch.

[0009] According to one embodiment, the region in said phase-change material has a width on the order of one or more tens of micrometers, preferably between 10 and 100 pm, more preferably between 30 and 100 pm.

[0010] According to one embodiment, a second face of the central region of the waveguide, opposite to the first face, is separated from the region in said phase-change material by a distance between 0 and 550 nm.

[0011] According to one embodiment, the central region of the waveguide has: - a width between 200 nm and 2 pm; and - a height between 200 and 400 nm.

[0012] According to one embodiment, the first and second conduction electrodes are part of an antenna element of a transmitting array cell or reflecting array cell.

[0013] According to one embodiment, the central region of the waveguide is interposed between the first and second conduction electrodes, on the one hand, and the region in said phase-change material, on the other hand.

[0014] According to one embodiment, the region in said phase-change material is interposed between the first and second conduction electrodes, on the one hand, and the central region of the waveguide, on the other hand.

[0015] According to one embodiment, said phase change material is: - a chalcogenide material, preferably germanium telluride, antimony telluride or germanium-antimony-telluride; or - vanadium dioxide. Brief description of the drawings

[0016] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0017] [Fig.1A] and [Fig.1B] are schematic and partial views, respectively from above and in section along plane BB of [Fig.1A], illustrating an example of a switch based on a phase change material;

[0018] [Fig. 2A] and [Fig. 2B] are schematic and partial views, respectively top and cross-sectional along plane BB of [Fig. 2A], illustrating an example of a phase-change material-based switch according to one embodiment; and

[0019] [Fig.3] is a graph illustrating variations in optical power absorbed by a phase-change material region of the switch in Figures 2A and 2B along a propagation direction, in a waveguide, of an optical signal for actuation of the switch. Description of the implementation methods

[0020] The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0021] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the control circuits of switches based on a phase-change material and the applications in which such switches may be used have not been detailed, as the described embodiments and variants are compatible with conventional control circuits of switches based on a phase-change material and with conventional applications using switches based on a phase-change material.

[0022] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements coupled together, this means that these two elements can be connected or linked through one or more other elements.

[0023] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0024] Unless otherwise specified, the expressions "approximately", "about", "substantially", and "in the order of" mean to within 10% or 10°, preferably to within 5% or 5°.

[0025] In the following description, the terms "insulating" and "conducting" mean, unless otherwise specified, electrically insulating and electrically conductive respectively.

[0026] Unless otherwise specified, the expression "in contact with" means "in mechanical contact with".

[0027] Fig. 1A and Fig. 1B are schematic and partial views, respectively top and cross-sectional along plane BB of Fig. 1A, illustrating an example of a switch 100 based on a phase-change material. In the example shown, plane BB of Fig. 1A is a vertical plane parallel to a conduction direction of the switch 100.

[0028] In figures IA and IB, the direction of conduction of the switch 100 is parallel to a horizontal axis Oy, and the plane BB is parallel to a vertical plane Oyz orthogonal to an axis Ox.

[0029] In the example shown, the switch 100 comprises conduction electrodes 101A and 101B. The conduction electrodes 101A and 101B of the switch 100 are intended, for example, to be connected to a radio frequency communication circuit, not detailed in the figures. The conduction electrodes 101A and 101B are made of an electrically conductive material, for example a metal, such as copper or aluminum, or a metal alloy. Furthermore, the conduction electrodes 101A and 101B may have a single-layer or multi-layer structure.

[0030] Although not detailed in Figures IA and IB to avoid cluttering the drawing, the conduction electrodes 101A and 101B of the switch 100 are, for example, located on and in contact with the upper surface of an electrically insulating layer, for example, of silicon dioxide (SiO2), coating a substrate. For example, the substrate in this case is a wafer or a piece of wafer made of a semiconductor material, for example, silicon. The conduction electrodes 101A and 101B of the switch 100 are, for example, part of an antenna element of a transmit array or reflect array cell.

[0031] In the illustrated example, the switch 100 further comprises a region 103 made of a phase-change material connecting the conduction electrodes 101A and 101B. Although not detailed in the figures, the region 103 made of phase-change material has, for example, an upper surface covered with another electrically insulating layer, for example, silicon dioxide, extending laterally between the electrodes 101A and 101B, the electrically insulating layer being flush with, for example, the upper surfaces of the electrodes 101A and 101B. In the example shown, the region 103 made of phase-change material extends onto and is in contact with a portion of the upper surface of each conduction electrode 101A, 101B. In the illustrated example, the region 103 made of phase-change material has a width L. The width L of the region 103 corresponds more precisely to The lateral dimension of region 103 is measured along the Ox axis. The width L of region 103 in phase-change material is, for example, on the order of a few tens of micrometers, e.g., between 10 and 100 pm, e.g., between 30 and 100 pm. As an example, region 103 in phase-change material has a thickness e on the order of 100 nm.

[0032] By way of example, region 103 of switch 100 is made of a so-called "chalcogenide" material, that is to say, a material or alloy comprising at least one chalcogen element, for example a material from the germanium telluride (GeTe), antimony telluride (SbTe) or germanium-antimony-telluride (GeSbTe, commonly referred to by the acronym "GST") family. By way of alternative, region 103 is made of vanadium dioxide (VO2).

[0033] Generally speaking, phase-change materials are materials capable of alternating, under the effect of a temperature variation, between a crystalline phase and an amorphous phase, the amorphous phase having a higher electrical resistance than the crystalline phase. In the case of the switch 100, this phenomenon is exploited to obtain a blocked state, preventing the flow of current between the conduction electrodes 101A and 101B, when the material in the region 103 located between the conduction electrodes is in the amorphous phase, and a conducting state, allowing the flow of current between the conduction electrodes 101A and 101B, when the material in the region 103 is in the crystalline phase.

[0034] In the example shown, the switch 100 further comprises a waveguide 105 located opposite the phase-change material region 103 and extending laterally along a principal direction substantially orthogonal to the conduction direction of the switch 100. In Figures IA and IB, the waveguide 105 of the switch 100 extends parallel to the Ox axis. The waveguide 105 has, for example, a first end located opposite an upper face of the phase-change material region 103 and a second end, opposite the first end, intended to be illuminated by a laser source LS. The laser source LS emits, for example, radiation constituting an optical control signal for the switch 100. The laser radiation LS emitted by the source propagates, for example, in the waveguide 105 in the form of an optical wave.For example, the radiation emitted by the LS laser source exhibits either magnetic transverse polarization (TM) or electric transverse polarization (TE).

[0035] In the illustrated example, the waveguide 105 comprises a central region 107, or core, surrounded by an electrically insulating peripheral region 109. In the illustrated example, the central region 107 of the waveguide 105 extends parallel to the Ox axis. The central region 107 and the peripheral region 109 of the waveguide 105 are made of materials chosen to obtain a contrast in refractive indices allowing to confine and guide an optical mode of interest emitted by the laser source LS. The material of the central region 107 of the waveguide 105 has, for example, a refractive index strictly greater than that of the peripheral region 109. As an example, the central region 107 of the waveguide 105 is made of silicon nitride and the peripheral region 109 is made of silicon dioxide.

[0036] The BB plane of [Fig. 1A] is substantially orthogonal to a direction of laser radiation propagation in the waveguide 105. In the illustrated example, the direction of laser radiation propagation in the waveguide 105 is parallel to the Ox axis. In the example shown, the peripheral region 109 of the waveguide 105 covers the faces of the central region 107 parallel to the direction of laser radiation propagation (the lateral, lower, and upper faces of the central region 107 of the waveguide 105 parallel to the Ox axis, in Figures IA and IB). More precisely, the peripheral region 109 is in contact with the lateral, lower, and upper faces of the central region 107.In this example, part of the peripheral region 109 of the waveguide 105 extends vertically, along the vertical axis Oz orthogonal to the horizontal axes Ox and Oy, from a face of the central region 107 located opposite the region 103 in phase-change material (the lower face of the central region 107 of the waveguide 105, in the orientation of [Fig.1B]) to a face of the region 103 in phase-change material opposite the conduction electrodes 101A and 101B (the upper face of the region 103 in phase-change material, in the orientation of [Fig.1B]).

[0037] In the example shown, the central region 107, in cross-sectional view along the plane BB orthogonal to the direction of laser radiation propagation in the waveguide 105, has a substantially rectangular shape. For example, the central region 107, in cross-sectional view along the plane BB, has a width w (along the Ox axis) of approximately 300 nm and a height h (along the Oz axis) of approximately 350 nm. Furthermore, the central region 107 of the waveguide 105 is separated from the phase-change material region 103 by a distance g. In this example, the distance g is equivalent to the thickness of the portion of the peripheral region 109 interposed between the central region 107 of the waveguide 105 and the phase-change material region 103. For example, the distance g is approximately 300 nm.

[0038] The waveguide 105 is, for example, of the single-mode type, meaning that it is adapted to confine and guide a single optical mode for each type of polarization. More precisely, the waveguide 105 is adapted to confine and guide a single optical mode chosen from a zero-order transverse electric mode (TE0), parallel to the Oy axis, and a zero-order transverse magnetic mode (TM0), parallel to the Oz axis. Because the TE0 and TM0 modes are orthogonal, they cannot be to be mutually coupled in the waveguide 105. The choice of the confined and guided mode by the waveguide 105, between the TEO mode and the TMO mode, is determined by the polarization of the laser source LS. Thus, in a case where the laser source LS emits radiation with a magnetic transverse polarization TM, the waveguide 105 is suitable for confining and guiding only the zero-order magnetic transverse mode TMO.

[0039] On the side of its end intended to be illuminated by the laser source LS, the waveguide 105 includes, for example, an input coupling element, also called the input surface of the waveguide 105. On the side of its end located opposite the region 103 of phase-change material, the waveguide 105 may further include an output coupling element, also called the output surface of the waveguide 105. The input coupling element may have a structure, for example a diffraction grating having a Bragg structure or any other coupling structure, allowing the radiation emitted by the laser source LS to be captured and propagated to the output surface.

[0040] Furthermore, the output surface of the waveguide 105 may have a structure that allows the radiation propagated from the input surface to be re-emitted towards the phase-change material region 103. Although not detailed in Figures IA and IB, the output surface of the waveguide 105 may have a structure identical or similar to that of its input surface.

[0041] Generally, the inlet and outlet surfaces of the waveguide 105 allow, respectively, in the example shown, the reception and transmission of radiation, or optical wave, along a direction orthogonal to the direction of propagation of the radiation, or optical wave, inside the waveguide 105, for example a direction parallel to the Oz axis. As an alternative, at least one surface, among the inlet and outlet surfaces of the waveguide 105, may have a structure allowing the reception or transmission of radiation, or optical wave, respectively, along a direction parallel to the direction of propagation of the radiation, or optical wave, inside the waveguide 105 (parallel to the Ox axis, in this example).

[0042] To switch the switch 100 from the blocked state to the conducting state, the region 103 is heated, using the laser source LS, via the waveguide 105, to a temperature Tl and for a duration dl. The temperature Tl and the duration dl are chosen so as to induce a phase change of the material in region 103 from the amorphous phase to the crystalline phase. By way of example, the temperature Tl is above the crystallization temperature and below the melting temperature of the material undergoing the phase change, and the duration dl is between 10 and 100 ns.

[0043] Conversely, to switch the switch 100 from the conducting state to the blocking state, the region 103 is heated, using the laser source LS, via the waveguide 105, to a temperature T2, higher than the temperature T1, and for a duration d2, shorter than the duration d1. The temperature T2 and the duration d2 are chosen so as to induce a phase change of the material in the region 103 from the crystalline phase to the amorphous phase. By way of example, the temperature T2 is higher than the melting temperature of the material undergoing the phase change, and the duration d2 is on the order of 10 ns.

[0044] One drawback of the switch 100 is that the optical wave propagating in the waveguide 107 is not absorbed homogeneously in the phase-change material region 103 along the direction of optical wave propagation in the waveguide 105 (along the Ox axis, in this example). In the example of the switch 100, the optical wave is mostly absorbed by a first part 103N of the phase-change material region 103 close to the laser source LS, the absorption of the optical wave being weaker in a second part 103F of the phase-change material region 103, opposite the first part 103N, which is further from the laser source LS than the first part 103N. The optical absorption of the wave by the 103 region in phase change material more precisely follows a decreasing exponential from the 103N part of the 103 region to the 103F part.

[0045] Thus, during an activation phase of the switch 100, the optical power absorbed by the second part 103F of the region 103 may prove insufficient to cause a phase change of the material in the part 103F. If it is desired to switch the switch 100 from the conducting state to the blocking state, this may prevent the second part 103F of the region 103 from changing phase from the crystalline phase to the amorphous phase, thereby undesirably allowing the passage of a leakage current between the conduction electrodes 101A and 101B of the switch 100. This phenomenon is all the more likely to occur as the width L of the region 103 is large.

[0046] The inventors observed that the phenomenon arises from the fact that the magnetic transverse mode TM of the laser signal activating the switch 100, confined and guided by the waveguide 105, is strongly absorbed by the phase-change material of the region 103, thus leading to a heating of the 103N portion much greater than that observed in the 103F portion. To overcome this problem, the geometry of the waveguide 105 could be modified to confine and guide only the electrical transverse mode TE, which is absorbed less strongly by the phase-change material of the region 103 than the magnetic transverse mode TM. By way of example, the magnetic transverse mode TM exhibits losses, related to absorption by The phase-change material in region 103 exhibits an absorption coefficient of approximately 2,500 dB·cm², compared to about 500 dB·cm² for the electric transverse (TE) mode. However, for equivalent laser power values, this would not generate sufficient heating in region 103 to induce a phase change. More generally, in both electric transverse (TE) and magnetic transverse (TM) modes, optical absorption follows a decreasing exponential distribution for this waveguide configuration. However, a linear absorption distribution would be preferable to allow for modification of the phase-change material in region 103.

[0047] Furthermore, switches based on a phase-change material with so-called "direct" optical actuation have been proposed. In these switches, the region made of the phase-change material is, for example, irradiated by a laser source focused on said region, the switches being, for example, without a waveguide between the laser source and the region made of the phase-change material.

[0048] Such a switch is described in the article by A. Crunteanu et al. entitled “Optical Switching of GeTe Phase Change Materials for High-Frequency Applications” and published in 2017 following the “IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP)” conference. In this article, a krypton fluoride (KrF) laser source emits radiation with a wavelength of approximately 248 nm, for example in the form of pulses, to induce transitions in a phase-change material region of a switch between the amorphous and crystalline phases. A pulse with a fluence of approximately 90 mJ.cm² is used, for example, to obtain a transition from the amorphous phase to the crystalline phase. Furthermore, another pulse with a fluence of approximately 185 mJ.cm2 is, for example, used to obtain a transition from the crystalline phase to the amorphous phase.

[0049] However, optically actuated phase-change material switches have drawbacks. In particular, these switches are incompatible with encapsulated component structures. Furthermore, each switch requires the use of a dedicated laser source. This greatly hinders or complicates the realization of integrated electronic components comprising several individually controllable switches.

[0050] Fig. 2A and Fig. 2B are schematic and partial views, respectively top and cross-section along plane BB of Fig. 2A, illustrating an example of a 200 switch based on a phase-change material according to one embodiment.

[0051] The switch 200 of Figures 2A and 2B includes elements common to the switch 100 of Figures IA and IB. These common elements will not be detailed again below. The switch 200 of Figures 2A and 2B differs from the switch 100 of Figures 1A and 1B in that the switch 200 further includes a region 201 located in the peripheral region 109 of the waveguide 105, directly above a face of the central region 107 of the waveguide 105 opposite the region 103 made of phase-change material.

[0052] Furthermore, the central region 107 of the waveguide 105 of the switch 200 is interposed vertically between the conduction electrodes 101A and 101B, on the one hand, and the phase-change material region 103, on the other. However, this example is not limiting. As an alternative, the switch 200 may have a structure analogous to that of the switch 100, in which the phase-change material region 103 is interposed vertically between the conduction electrodes 101A and 101B, on the one hand, and the central region 107 of the waveguide 105, on the other. In this alternative, the central region 107 of the waveguide 105 is then interposed vertically between the phase-change material region 103 and the region 201.

[0053] In the illustrated example, the phase-change material region 103 is connected to the conduction electrodes 101A and 101B by conductive vias 203A and 203B, respectively. In the orientation of [Fig. 2B], the vias 203A and 203B extend from the upper faces of the conduction electrodes 101A and 101B, respectively, to two opposite areas of the lower face of the phase-change material region 103. The vias 203A and 203B are for example separated by a wPCM distance corresponding for example to a width of a so-called "active" zone of the region 103 in phase change material, that is to say a zone of the region 103 in which the phase change actually occurs when the optical control signal of the switch 200 is transmitted by the waveguide 105.

[0054] In the example shown, region 201 extends into the peripheral region 109 of the waveguide 105 from the face of the central region 107 opposite region 103. In the orientation of [Fig. 2B], the central region 107 of the waveguide 105 is located on and in contact with the upper face of region 201. In the illustrated example, the peripheral region 109 of the waveguide 105 covers all faces of region 201 except its upper face. More precisely, the peripheral region 109 is in contact with all faces of region 201 except its upper face.

[0055] Furthermore, in this example, the peripheral region 109 of the waveguide 105 covers the faces of the central region 107 parallel to the direction of propagation of the optical control signal of the switch 200 (the lateral, lower and upper faces of the central region 107 of the waveguide 105 parallel to the Ox axis, in figures 2A and 2B) except for at least a part of its lower face located in contact with the region 201. In the example shown, the region 109 is more precisely in contact with said faces of the region 107.

[0056] This example is not, however, limiting, and the region 201 may, as an alternative, be separated from the central region 107 of the waveguide 105 by a portion of the peripheral region 109 extending vertically along the Oz axis from a face of the central region 107 opposite the region 201 (the lower face of the central region 107, in the orientation of [Fig. 2B]) to a face of the region 201 opposite the central region 107 (the upper face of the region 201, in the orientation of [Fig. 2B]). In this alternative, the peripheral region 109 of the waveguide 105 covers, or is more precisely in contact with, all the faces of the region 201 and the lateral, lower, and upper faces of the central region 107 of the waveguide 105 parallel to the Ox axis.

[0057] According to one embodiment, the region 201 is made of a material having a refractive index strictly lower than that of the peripheral region 109 of the waveguide 105. The region 201 is, for example, a cavity formed in the peripheral region 109 of the waveguide 105. Generally, the cavity is at least partially filled with one or more solid, liquid or gaseous substances having a refractive index lower than that of the peripheral region 109 of the waveguide 105. The cavity is, for example, at least partially filled with at least one substance chosen from: - a gas, for example carbon dioxide, or a gaseous mixture, for example air; - a liquid, for example acetone; and / or - ice.

[0058] The presence of region 201, which has a lower refractive index than the peripheral region 109 of the waveguide 105, increases the absorption of the optical control signal of the switch 200 by the phase-change material of region 103. The greater the width w2 (along the Ox axis) of region 201, the greater the absorption of the optical control signal of the switch 200 by the phase-change material of region 103. In the example shown, region 201, viewed from above, has a tapered shape that flares out, or widens, along the propagation direction of the optical control signal of the switch 200. More precisely, in this example, the width w2 of region 201 is smaller in the vicinity of part 103N of region 103 than in the vicinity of part 103F.In the illustrated example, the width w2 of region 201 increases monotonically from part 103N to part 103F.

[0059] The table below provides examples of minimum (min) and maximum (max) values, in nanometers (nm) of different dimensions of the switch 200, in this case: the height h and the width w of the central region 107 of the waveguide 105, the distance g separating the central region 107 of the waveguide 105 from the region 103 in phase change material, and the width w2 of the region 201. [Tables 1] Dimension Minimum value (nm) Maximum value (nm) h 200 400 w 200 2000 g 0 550 w2 0 WpCM

[0060] The value of the height h is, for example, chosen so as to allow the guidance of a single transverse magnetic mode TM, for example the TM0 mode, without producing harmonics. The value of the width w is, for example, chosen so as to allow the guidance of the optical control signal of the switch 200 without exciting higher-order modes. The value of the distance g, which separates the phase-change material region 103 from a face of the central region 107 of the waveguide 105 opposite the region 201, is, for example, chosen so as to allow adjustment of an initial absorption level, i.e., in the vicinity of the 103N portion of the region 103, in the absence of the region 201. The values ​​of the width w2 are, for example, chosen so as to allow control of the position of the optical propagation mode.

[0061] The table below provides, by way of example, values ​​of the width w2 of the region 201 as a function of the position along the Ox axis, the coordinate 0 corresponding to the position of the lateral face of the region 103 located on the side of the part 103N. In the example below, the dimensions h, w, g and L are respectively equal to approximately 300 nm, 600 nm, 330 nm and 20 pm. [Tables 2] Position (pm) w2 (pm) 0 0 5 0.2 10 0.5 > 12 1

[0062] The table below provides, by way of example, values ​​for the width w2 of region 201 as a function of its position along the Ox axis. In the example below, the dimensions h, w, g and L are respectively equal to approximately 400 nm, 200 nm, 350 nm and 30 pm. [Tables 3] Position (pm) w2 (pm) 0 0 6 0.1 9.7 0.2 13 0.5 > 14 2

[0063] The table below provides, by way of example, values ​​of the width w2 of region 201 as a function of the position along the Ox axis. In the example below, the dimensions h, w, g and L are respectively equal to approximately 200 nm, 2 pm, 550 nm and 90 pm. [Tables 4] Position (pm) w2 (pm) 0 0 11 0.1 16 0.2 20 0.3 43 1 52 1.2 >69 3

[0064] In the examples above, the thickness e of the region 103 in phase change material is equal to approximately 100 nm.

[0065] The examples provided above are not, however, limiting, and a person skilled in the art is able to define the values ​​of the dimensions h, w, g and w2 as a function, among other things, of the width L of the region 103 in phase-change material. Numerical simulation tools can, for example, be used for this purpose.

[0066] An advantage of the switch 200 described above in relation to Figures 2A and 2B lies in the fact that the presence of region 201 ensures that the laser control signal of the switch 200 is absorbed substantially uniformly by the phase-change material of region 103. More specifically, in the case of switch 200, the magnetic transverse mode TM is absorbed less strongly directly above part 103N of region 103 and more strongly directly above the 103F portion of region 103. As an example, the TM mode losses are approximately 500 dB.cm1 in the vicinity of portion 103N and approximately 2500 dB.cm1 in the vicinity of portion 103F. This prevents, compared to switch 100 in Figures IA and IB, a portion of region 103 made of phase-change material, for example, portion 103F furthest from the laser source LS, from not changing phase when the switch is activated.

[0067] The integration of the switch 200 described above proves particularly advantageous in radio frequency communication electronic devices. Indeed, for this type of application, it is very beneficial to have switches with a large width L, for example, on the order of a few tens of micrometers, as this limits the occurrence of parasitic capacitance phenomena and allows switching of more intense electrical signals than in the case of switches with a smaller width L. However, this example is not exhaustive, and those skilled in the art can, of course, take advantage of the benefits of switch 200 in many applications other than radio frequency communication.

[0068] Fig. 3 is a graph illustrating variations in optical power P (in milliwatts, mW) absorbed by the phase-change material region 103 of the switch 200 as a function of a position (in micrometers, pm) measured along the Ox direction of propagation, in the waveguide 105, of the optical signal actuation of the switch 200.

[0069] In the example shown, a curve 301 illustrates an ideal case in which the optical power P is absorbed linearly in the phase-change material of the region 103. This case leads to a uniform, or homogeneous, heating of the phase-change material of the region 103.

[0070] In [Fig. 3], another curve 303 illustrates a case of a switch analogous to the switch 200 but lacking the region 201. In this case, the distance g allows the phase-change material region 103 to absorb, in the first few micrometers from the part 103N, an optical power substantially equal to that which is absorbed in the ideal case illustrated by curve 301. However, in the last few micrometers located in the vicinity of the part 103F, the absorbed optical power is greater than that of the ideal case illustrated by curve 301. This is undesirable, because the phase-change material of the region 103 risks being damaged by this excess optical power.

[0071] In the example shown, another curve 305 illustrates the case of the switch 200, in which the distance g is substantially equal to that of the switch in the case of curve 303 and in which the presence of the region 201 makes it possible to obtain, in the region 103 in phase change material, an absorption profile of optical power P very close to that of the ideal case illustrated by curve 301. Curve 305 corresponds more precisely to the example described above in relation to the table [Table 3].

[0072] Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants could be combined, and other variants will become apparent to those skilled in the art. In particular, the dimensions e and L of the phase-change material region 103, the dimensions w and h of the central region 107 of the waveguide 105, the dimension w2 of the region 201, and the distance g can be adapted by those skilled in the art from the indications in this description, for example, according to the intended application.

[0073] Finally, the practical implementation of the described embodiments and variants is within the reach of a person skilled in the art, based on the functional specifications given above. In particular, the described embodiments are not limited to the specific examples of materials and dimensions mentioned in this description.

Claims

Demands

1. Switch (200) based on a phase-change material comprising: - a region (103) of said phase-change material connecting first (101A) and second (101B) conduction electrodes of the switch; - a waveguide (105) located above the region (103) of said phase-change material and comprising a central region (107) of a first material having a first refractive index surrounded by a peripheral region (109) of a second material having a second refractive index lower than the first refractive index; and - a region (201) in a third material having a third refractive index lower than the second refractive index and located in the peripheral region (109) of the waveguide (105) directly above a first face of the central region (107) of the waveguide (105) opposite the region (103) in said phase-change material.

2. Switch (200) according to claim 1, wherein the region (201) in said third material extends from the first face of the central region (107) of the waveguide (105).

3. Switch (200) according to claim 1 or 2, wherein the region (201) in said third material is a cavity at least partially filled with one or more solid, liquid or gaseous substances, preferably an air-filled cavity.

4. Switch (200) according to any one of claims 1 to 3, wherein the region (201) in said third material has, in top view, a tapered shape flaring out along a direction (Ox) of propagation of an optical signal for controlling the switch.

5. Switch (200) according to any one of claims 1 to 4, wherein the region (103) in said phase-change material has a width (L) on the order of one or more tens of micrometers, preferably between 10 and 100 pm, more preferably between 30 and 100 pm.

6. A switch (200) according to any one of claims 1 to 5, wherein a second face of the central region (107) of the guide wave (105), opposite the first face, is separated from the region (103) in said phase-change material by a distance (g) between 0 and 550 nm.

7. Switch (200) according to any one of claims 1 to 6, wherein the central region (107) of the waveguide (105) has: - a width (w) between 200 nm and 2 pm; and - a height (h) between 200 and 400 nm.

8. Switch (200) according to any one of claims 1 to 7, wherein the first (101A) and second (101B) conduction electrodes are part of an antenna element of a transmitting array cell or reflecting array cell.

9. Switch (200) according to any one of claims 1 to 8, wherein the central region (107) of the waveguide (105) is interposed between the first (101A) and second (101B) conduction electrodes, on the one hand, and the region (103) in said phase-change material, on the other hand.

10. Switch (200) according to any one of claims 1 to 8, wherein the region (103) of said phase-change material is interposed between the first (101A) and second (101B) conduction electrodes, on the one hand, and the central region (107) of the waveguide (105), on the other hand.

11. Switch (200) according to any one of claims 1 to 10, wherein said phase-change material is: - a chalcogenide material, preferably germanium telluride, antimony telluride or germanium-antimony-telluride; or - vanadium dioxide.

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