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 (107) of said phase-change material connecting the first (101A) and second (101B) conduction electrodes of the switch; and – a coupling array (201) for a laser signal to activate the switch, located opposite a face of the region (107) of said phase-change material. Figure for the abbreviation: Fig. 2A

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; and - a coupling network for a laser signal to activate the switch, located opposite a face of the region in said phase-change material.

[0006] According to one embodiment, the coupling network comprises, directly above the region in said phase-change material, an alternation of first regions in a first material having a first optical index and second regions in a second material having a second optical index strictly lower than the first optical index.

[0007] According to one embodiment, the coupling network is configured to irradiate a constant optical power along a propagation direction of the switch activation laser signal.

[0008] According to one embodiment, the first regions are distributed at a constant step and have a decreasing width along the direction of propagation of the laser signal for activating the switch.

[0009] According to one embodiment, the coupling network is configured to irradiate a decreasing optical power along a propagation direction of the switch activation laser signal, the first regions being distributed at a constant pitch and having a constant width.

[0010] According to one embodiment, the coupling network is located in the extension of a waveguide, the waveguide comprising a central region in said first material surrounded by a peripheral region in said second material.

[0011] According to one embodiment, the first material is silicon nitride and the second material is silicon oxide.

[0012] According to one embodiment, a portion of the central region of the waveguide has: - a tapered shape narrowing in the vicinity of the region made of said phase-change material; or - a flared shape widening in the vicinity of the region in said phase-change material.

[0013] According to one embodiment, the switch further comprises a support substrate, the coupling network being interposed between the support substrate and the region in said phase-change material.

[0014] According to one embodiment, the switch further comprises a reflective layer interposed between the support substrate and the coupling network.

[0015] According to one embodiment, the reflective layer is made of silicon or silicon nitride.

[0016] According to one embodiment, the coupling network is separated from the layer in said phase change material by a distance greater than 100 nm.

[0017] According to one embodiment, the region in said phase-change material has a width in a range from 1 to 100 pm, preferably from 10 to 100 pm, more preferably from 30 to 100 pm.

[0018] 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.

[0019] 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

[0020] 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:

[0021] [Fig.1A], [Fig.1B] and [Fig.1C] are schematic and partial views, respectively from above, in section along plane BB of [Fig.1A] and in section along plane CC of [Fig.1A], of an example of a switch based on a phase change material;

[0022] [Fig.2A] and [Fig.2B] are schematic and partial views, respectively from above and in section along plane BB of [Fig.2A], of a phase change material switch according to an embodiment;

[0023] [Fig.3] is a schematic and partial top view of a variant of the switch in [Fig.2A];

[0024] [Fig.4A] and [Fig.4B] are schematic and partial views, respectively from above and in section along plane BB of [Fig.4A], of a phase change material switch according to an embodiment;

[0025] [Fig. 5] is a schematic and partial cross-sectional view of a coupling network according to one embodiment; and

[0026] [Fig.6] is a schematic and partial cross-sectional view of a coupling network according to one embodiment. Description of the implementation methods

[0027] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0028] 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 for switches based on a phase-change material and with conventional applications using switches based on a phase-change material.

[0029] Unless otherwise specified, when referring to two interconnected elements, this means directly connected without any intermediate elements other than conductors, and when referring to two coupled elements " between them, this means that these two elements can be connected or linked via one or more other elements.

[0030] In the following description, when reference is made to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative positional qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientational qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0031] 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°.

[0032] In the following description, the terms "insulating" and "conducting" mean, unless otherwise specified, electrically insulating and electrically conductive respectively.

[0033] Unless otherwise specified, the expression "in contact with" means "in mechanical contact with".

[0034] Fig. 1A, Fig. 1B, and Fig. 1C are schematic partial views, respectively top, cross-sectional along plane BB of Fig. 1A, and cross-sectional along plane CC of Fig. 1A, of an example of a phase-change material switch 100. In the example shown, plane BB is a vertical plane orthogonal to a conduction direction of the switch 100, and plane CC is a vertical plane parallel to the conduction direction of the switch 100.

[0035] In figures IA to IC, the conduction direction of switch 100 is parallel to an axis Oy, plane BB is parallel to a vertical plane Oxz, orthogonal to the axis Oy, and plane CC is parallel to a vertical plane Oyz, orthogonal to an axis Ox.

[0036] 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 a 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.

[0037] In the illustrated example, the conduction electrodes 101A and 101B of the switch 100 are located in an insulating layer 103, for example of silicon oxide, coating a support substrate 105. By way of example, the support substrate 105 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 make for example part of an antenna element of a transmit array cell or reflect array cell.

[0038] In the example shown, the switch 100 further comprises a region 107 made of a phase-change material connecting the conduction electrodes 101A and 101B. In the illustrated example, the phase-change material region 107 covers the upper surface of a portion of the insulating layer 103 extending laterally between the electrodes 101A and 101B. In the example shown, the phase-change material region 107 extends onto and is in contact with a portion of the upper surface of each conduction electrode 101A, 101B. In the illustrated example, the phase-change material region 107 has, in top view, a substantially rectangular shape of width wP. The width wP corresponds, in this example, to the lateral dimension of the region 107 measured along the Ox axis.The width wP of region 107 in phase change material is, for example, within a range from 1 to 100 pm, for example from 10 to 100 pm, for example from 30 to 100 pm. As an example, region 107 in phase change material has a thickness hP, measured along the vertical axis Oz, of the order of 100 nm.

[0039] By way of example, the phase-change material region 107 of the switch 100 is made of a so-called "chalcogenide" material, that is to say, a material or alloy comprising at least one chalcogen element, for example a material from the germanium telluride (GeTe), antimony telluride (SbTe) or germanium-antimony-telluride (GeSbTe, commonly referred to by the acronym "GST") family. As an alternative, region 107 is made of vanadium dioxide (VO2).

[0040] 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 107 located between the conduction electrodes 101A and 101B 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 107 is in the crystalline phase.

[0041] In the example shown, the switch 100 further comprises a waveguide 109, for example an optical waveguide, located opposite the region 107 made of phase-change material and extending laterally along a principal direction substantially orthogonal to the conduction direction of the switch 100 (along the Ox direction, in the example shown). The waveguide 109 For example, it comprises a first end located opposite an upper face of the phase-change material region 107 and a second end, opposite the first end, intended to be illuminated by a laser source LS, for example, a laser diode or a pulsed laser. The laser source LS is intended, for example, to emit radiation constituting an optical control signal for the switch 100. The laser radiation LS emitted by the source propagates in the waveguide 109 as an optical wave. For example, the radiation emitted by the laser source LS has magnetic transverse polarization (TM) or electric transverse polarization (TE). Furthermore, the radiation emitted by the laser source LS has, for example, a central wavelength Xo of approximately 915 nm. The central wavelength Xo of the laser source LS is equivalent to the wavelength at which the optical power emitted by the laser source LS is maximum.As an example, the central wavelength Xo of the LS laser source is chosen so that it is compatible with integrated photonics and the phase-change material in the 107 region is absorbing at this wavelength.

[0042] In the illustrated example, the waveguide 109 comprises a central region 111, or core, surrounded by an insulating peripheral region, or sheath, formed, in this example, by a portion of the insulating layer 103. In the illustrated example, the central region 111 of the waveguide 109 extends parallel to the Ox axis. The central region 111 and the peripheral region of the waveguide 109 are made of materials chosen to obtain a refractive index contrast that allows for the confinement and guiding of an optical mode of interest emitted by the laser source LS. The material of the central region 111 of the waveguide 109 has, for example, a refractive index nE, or optical index, strictly greater than a refractive index n0 of the peripheral region. In the case where the peripheral region is made of silicon dioxide, the central region 111 of the waveguide 109 is, for example, made of silicon nitride.

[0043] The CC plane of [Fig. 1A] is substantially orthogonal to a direction of laser radiation propagation in the waveguide 109. The direction of laser radiation propagation in the waveguide 109 is, in the illustrated example, parallel to the Ox axis. In the example shown, the peripheral region of the waveguide 109 covers the faces of the central region 111 parallel to the direction of laser radiation propagation (the lateral, lower, and upper faces of the central region 111 of the waveguide 109 parallel to the Ox axis, in Figures IA to IC). More precisely, the peripheral region is in contact with the lateral, lower, and upper faces of the central region 111. In this example, a portion of the peripheral region of the waveguide 109 extends vertically along the vertical Oz axis orthogonal to the horizontal Ox and Oy axes from a face of the region central 111 located opposite the phase change material region 107 (the upper face of the central region 111 of the waveguide 109, in the orientation of Figures IB and IC) to a face of the phase change material region 107 located on the side of the conduction electrodes 101A and 101B (the lower face of the phase change material region 107, in the orientation of Figures IB and IC).

[0044] In the example shown, the central region 111, in cross-section along the CC plane orthogonal to the direction of laser radiation propagation in the waveguide 109, has a substantially rectangular shape. For example, the central region 111, in cross-section along the CC plane, has a width wG (along the Oy axis) of approximately 2 pm and a height hG (along the Oz axis) of approximately 315 nm. Furthermore, the central region 111 of the waveguide 109 is separated from the phase-change material region 107 by a distance dp_G. In this example, the distance dP_G is equivalent to the thickness of the portion of the peripheral region interposed between the central region 111 of the waveguide 109 and the phase-change material region 107. As an example, the distance dP G is less than or equal to 100 nm.In the illustrated example, the central region 111 of the waveguide 109 is further separated from the upper face of the support substrate 105 by a distance dG_s. In this example, the distance dG_s is equivalent to a thickness of the part of the peripheral region interposed between the lower face of the central region 111 of the waveguide 109 and the upper face of the support substrate 105. As an example, the distance dG_s is between one or more hundred nanometers and one or more micrometers, for example equal to about 1.5 pm.

[0045] The waveguide 109 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 109 is adapted to confine and guide a single optical mode chosen from a zero-order electrical transverse mode (TE0), parallel to the Oy axis, and a zero-order magnetic transverse mode (TM0), parallel to the Oz axis. Because the TE0 and TM0 modes are orthogonal, they cannot couple to each other in the waveguide 109. The choice of the mode confined and guided by the waveguide 109, between the TE0 mode and the TM0 mode, is determined by the polarization of the laser source LS. Thus, in a case where the laser source LS emits radiation exhibiting an electrical transverse polarization TE, the waveguide 109 is suitable for confining and guiding the zero-order electrical transverse mode TE0 only.

[0046] On the side of its end intended to be illuminated by the laser source LS, the waveguide 109 includes, for example, an input coupling element, also called waveguide input surface 109. On the side of its end located opposite the phase change material region 107, the waveguide 109 may further include an output coupling element, also called the output surface of the waveguide 109. 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.

[0047] Furthermore, the output surface of the waveguide 109 may have a structure that allows the radiation propagated from the input surface to be re-emitted towards the phase-change material region 107. In the example shown, the output coupling element is the portion of the waveguide 109 located directly above the phase-change material region 107.

[0048] Generally, the inlet and outlet surfaces of the waveguide 109 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 109, 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 109, for example the inlet surface, 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 109 (parallel to the Ox axis, in this example).

[0049] To switch the switch 100 from the blocked state to the conducting state, the region 107 is heated by means of the laser source LS, by evanescent coupling of the wave propagated by the waveguide 109, 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 the region 107 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 100 ns and 5 ps.

[0050] Conversely, to switch the switch 100 from the conducting state to the blocking state, the region 107 is heated by means of the laser source LS, by evanescent coupling of the wave propagated by the waveguide 109, 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 107 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 within a range from 10 ns to 500 ns.

[0051] One drawback of the switch 100 is that the optical wave propagating in the waveguide 109 is not absorbed homogeneously in the phase-change material region 107 along the direction of optical wave propagation in the waveguide 109 (along the Ox axis, in this example). In the example of the switch 100, the optical wave is predominantly absorbed by a first portion 107N of the phase-change material region 107. This portion 107N is closest to the laser source LS. The absorption of the optical wave is weaker in a second portion 107F of the phase-change material region 107, opposite the first portion 107N, which is farther from the laser source LS than the first portion 107N. The optical absorption of the wave by the 107 region in phase change material more precisely follows a decreasing exponential from the 107N part of the 107 region to the 107F part.

[0052] Thus, during an activation phase of the switch 100, the optical power absorbed by the second part 107F of the region 107 may prove insufficient to cause a phase change of the material in the part 107F. In the case of a switching from the on-state to the off-state, this may prevent the second part 107F of the region 107 from changing phase from the crystalline phase to the amorphous phase, thus undesirably allowing the passage of a leakage current between the conduction electrodes lOlA and lOlB of the switch 100. This phenomenon is all the more likely to occur as the width wP of the region 107 is large.

[0053] The inventors observed that the phenomenon arises from the fact that the electrical transverse mode TE of the laser signal activating the switch 100, confined and guided by the waveguide 109, is strongly absorbed by the phase-change material of the region 107, thus leading to heating of the 107N portion much greater than that observed in the 107F portion. To overcome this problem, the geometry of the waveguide 109 could be modified to confine and guide only the magnetic transverse mode TM. However, the magnetic transverse mode TM is more strongly absorbed by the phase-change material of the region 107 than the electrical transverse mode TE, which would amplify the phenomenon. As an example, the magnetic transverse mode TM exhibits losses, linked to absorption by the phase-change material of region 107, of the order of 2,500 dB.cm ', compared to about 500 dB.cm 1 for the electrical transverse mode TE.

[0054] More generally, in both the electric transverse mode (TE) and the magnetic transverse mode (TM), the absorbed optical power follows a decreasing exponential law for this waveguide configuration, while the optical absorption law is constant. However, it would be preferable for the absorbed power to follow a law constant, which could be ensured for example by a law of increasing linear optical absorption, to allow modification of the state of the phase change material of region 107. This would in particular make it possible to compensate for the fact that less and less optical power remains in the guide as the optical power is absorbed.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Fig. 2A and Fig. 2B are schematic and partial views, respectively top and cross-section along plane BB of Fig. 2A, of a 200 switch based on a phase-change material according to an embodiment.

[0059] The switch 200 of Figures 2A and 2B includes elements common to the switch 100 of Figures IA to IC. These common elements will not be detailed again below. The switch 200 of Figures 2A and 2B differs from the switch 100 of Figures IA to IC in that the output surface of the waveguide 109 of the switch 200 includes a coupling network 201, for example a Bragg coupling network.

[0060] In the example shown, the coupling grating 201 is formed directly above the phase-change material region 107. The coupling grating 201 comprises a plurality of regions 203 made of a material having a refractive index nE strictly greater than a refractive index n0 of the insulating layer 103. The regions 203 are separated laterally from each other by portions of the insulating layer 103. The optical control signal from the laser source LS thus passes, along its direction of propagation, through an alternation of media with different optical indices. By way of example, each region 203 of the coupling grating 201 is made of the same material as the central region 111 of the waveguide 109. This facilitates the implementation of the switch 200, the regions 111 and 203 being, for example, formed by etching the same layer.

[0061] Each region 203, for example, in cross-sectional view along a plane orthogonal to the direction of laser radiation propagation in the waveguide 109, has a substantially rectangular shape, for example, a section identical, apart from manufacturing variations, to that of the central region 111 of the waveguide 109. In the example shown, each region 203 has a width LE. The width LE corresponds, in this example, to the lateral dimension of the region 203 measured along the horizontal axis Ox. Furthermore, in the example shown, each portion of the insulating layer 103 interposed laterally between two adjacent regions 203 has a width Lo. The width Lo corresponds, in this example, to the lateral dimension of the portion of the insulating layer 103 measured along the horizontal axis Ox.

[0062] In the illustrated example, the regions 203 of the coupling network 201 are distributed substantially uniformly, at a constant pitch, along the horizontal Ox direction. Furthermore, the regions 203 have identical dimensions, up to manufacturing variations, and the portions of the insulating layer 103 interposed laterally between the regions 203 have identical dimensions, up to manufacturing variations. In this example, the regions 203 and the portions of the insulating layer 103 interposed laterally between the regions 203 form a periodic structure of period A. In the illustrated example, the period A of the coupling network 201 corresponds to the sum of the widths LE and Lo.

[0063] The period A is chosen, as a function of the central wavelength Xo of the radiation propagated by the waveguide 109 and of an effective optical index neff resulting from the alternation of optical indices nE and n0 along the direction of propagation, so as to satisfy the first-order Bragg condition defined by the following relation:

[0064] [Math.l] A = è

[0065] In the case where the central wavelength Xo is equal to about 915 nm, the period A of the coupling grating 201 is for example between 600 and 760 nm, for example equal to about 680 nm.

[0066] The effective optical index neff is defined by the following relation:

[0067] [Math.2] neff = F.nE-( 1-F).no

[0068] In the above relation, the letter F denotes the filling factor of the coupling network 201. The filling factor F is defined by the following relation:

[0069] [Math.3] F = Fo - ax

[0070] In the above relationship, a denotes a leakage factor of the coupling network 201, x denotes the width of the switch 200, and Fo denotes the initial filling factor at the beginning of the coupling network. In the example shown, the width x is, for example, equal to the width wP of the region 107 in phase-change material. As an example, the width x is equal to approximately 20 pm.

[0071] The filling factor F of the coupling network 201 thus makes it possible to control the leakage factor a. As an example, the filling factor F is within a range of 0.5 to 0.9.

[0072] In the example shown, the LE width of the regions 203 is equal to the filling factor F multiplied by the period A of the coupling lattice 201 (LE = FA), and the Lo width of the portions of layer 103 interposed laterally between the regions 203 is equal to 1-F multiplied by the period A of the coupling lattice 201 (Lo = (1F)A). In a case where the filling factor F is equal to approximately 0.5 and where the period A is equal to approximately 680 nm, the LE width is equal to approximately 340 nm and the Lo width is equal to approximately 340 nm.

[0073] In the illustrated example, an optical power P is guided in the coupling grating 201. The optical power P satisfies the following relation, in which Po denotes the optical power supplied by the laser source LS, i.e. substantially the optical power present at the input of the coupling grating 201:

[0074] [Math.4] P - Poe2«x

[0075] Furthermore, the Prad power radiated by the coupling network 201 is defined by the following relation:

[0076] [Math.5] P rad = - g = 2aP (l e-2“

[0077] The distance dG s separating the support substrate 105 from the central region 111 of the waveguide 109 has, for example, in the case of the switch 200, a value substantially equal to that chosen in the case of the switch 100. As an example, the distance dG . s is, in the case of the switch 200, between one or more hundred nanometers and one or more micrometers, for example equal to about 1.5 pm.

[0078] In the example shown, the switch 200 further includes a reflective layer 205, or mirror layer, interposed between the support substrate 105 and the coupling network 201. The reflective layer 205 makes it possible to reflect, in the direction of the phase-change material region 107, the optical power radiated towards the support substrate 105. By way of example, the reflective layer 205 is made of silicon or silicon nitride.

[0079] In the illustrated example, the coupling network 201 is separated from the reflective layer 205 by a distance dG R. As an example, the distance dG R is within a range of 100 to 700 nm.

[0080] The distance dP G separating the region 107 in phase change material from the central region 111 of the waveguide 109 has, in the case of the switch 200, a value greater than that chosen in the case of the switch 100. In the case of the switch 200, the distance dP G is for example in a range from 100 to 300 nm, whereas the distance dP G is for example in a range from 0 to 100 nm in the case of the switch 100.

[0081] Unlike the switch 100, in which the optical power of the control signal from the laser source LS is transferred from the waveguide 109 to the phase-change material region 107 by evanescent coupling, the structure of the switch 200 allows the optical power to be transferred from the coupling grating 201 to the region 107 by direct irradiation. This advantageously avoids, compared to the switch 100, the strong absorption of the optical wave in the vicinity of the 107N portion of the phase-change material region 107 close to the laser source LS and allows for a better distribution of the absorption along the Ox axis. Furthermore, this allows for a larger dP G distance, which simplifies the implementation of the switch 200.

[0082] The [Fig.3] is a schematic and partial top view of a 200' variant of the 200 switch of the [Fig.2A].

[0083] In the illustrated example, the central region 111 of the waveguide 109 comprises, in the vicinity of the phase-change material region 107, a portion 111T having a flared shape. In this case, the portion 111T has an increasing width along the Ox axis and allows the light energy to be distributed under the phase-change material to be switched. This advantageously allows switching a larger area of ​​phase-change material, thus resulting in a more efficient switch with a lower off-state capacitance (Coff). The 200' variant illustrated in [Fig. 3] allows optical waves to be transmitted over a greater length of phase-change material than in the case of the 200 switch in Figures 2A and 2B. The length of phase-change material is considered along the Oy axis, between the conduction electrodes 101A and 101B. In the case of the 200' variant, the optical power is, for example, greater than that required in the case of the 200 switch for the phase-change material in region 107 to reach its melting or crystallization temperature.

[0084] As an alternative, portion 111T may have a tapered shape. In this case, portion 111T has a decreasing width along the Ox axis and allows the light energy to be concentrated under the phase-change material to be switched. This advantageously reduces the level of light intensity required for switching.

[0085] Fig. 4A and Fig. 4B are schematic and partial views, respectively top and cross-section along plane BB of Fig. 4A, of a 400 switch based on a phase-change material according to an embodiment.

[0086] The switch 400 of Figures 4A and 4B includes elements common to the switch 200 of Figures 2A and 2B. These common elements will not be detailed again below. The switch 400 of Figures 4A and 4B differs from the switch 200 of Figures 2A and 2B in that the coupling network 201 of the switch 400 is apodized.

[0087] In the example shown, the coupling network 201 of the switch 400 has a substantially constant period A and a variable fill factor F. More precisely, the fill factor F decreases along the direction of propagation of the control signal in the coupling network 201 of the switch 400, that is, along the Ox direction, in the example shown. In other words, the fill factor F is greater in the vicinity of the 107N portion of the region 107 made of phase-change material than in the vicinity of the 107F portion. In this example, the width LE of the regions 203 decreases along the Ox direction, and the width Lo of the portions of the insulating layer 103 extending laterally between the regions 203 increases along the direction of propagation of the control signal.This allows the coupling grating 201 to irradiate a lower optical power in the vicinity of the 107N part of the 107 region in phase-change material than in the vicinity of the 107F part.

[0088] An advantage of the switch 400 described above in relation to Figures 4A and 4B lies in the fact that the presence of the apodized coupling network 201 ensures that the laser control signal of the switch 400 is absorbed substantially uniformly by the phase-change material of the region 107. More specifically, in the case of the switch 400, the electrical transverse mode TE is absorbed less strongly directly above the 107N portion of the region 107 and more strongly directly above the 107F portion of the region 107. This prevents, compared to the switch 100 of Figures IA and IB, a portion of the region 107 made of phase-change material, for example the 107F portion furthest from the laser source LS, from not changing phase when the switch is controlled.

[0089] The integration of the 400 switch 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 wP, for example, on the order of a few tens of micrometers, as this reduces resistive losses in the on-state compared to switches with a smaller width wP. Furthermore, the integration of the 400 switch limits the occurrence of parasitic capacitance phenomena and allows switching of more intense electrical signals than in the [unspecified application]. However, this example is not exhaustive, and those skilled in the art can, of course, take advantage of the 400 switch in many applications other than radio frequency communication.

[0090] Figures 4A and 4B illustrate an example of an embodiment of the switch 400 in which the regions 203 of the coupling array 201 are regularly spaced, at constant pitch, directly above the region 107 made of phase-change material. This example is not, however, limiting, and those skilled in the art can foresee, as an alternative, other coupling array structures 201 designed to allow the coupling array 201 to radiate a constant optical power along the propagation direction of the control signal from the laser source LS. These structures are within the grasp of those skilled in the art upon reading this description. By way of example, those skilled in the art can foresee that the coupling array has a constant fill factor F and an increasing period A along the propagation direction of the control signal.

[0091] Figure 5 is a schematic and partial cross-sectional view of a coupling network according to one embodiment. Figure 5 illustrates, for example, an embodiment variant 201' of the coupling network 201 of the switch 200 of Figures 2A and 2B, it being understood that a person skilled in the art is able, upon reading this description, to adapt this variant to the coupling network 201 of variant 200' of Figure 3 and to that of the switch 400 of Figures 4A and 4B.

[0092] In the example shown, the regions 203 of the coupling network 201' protrude from the upper face of the central region 111 of the waveguide 109. The regions 203 have, for example, a crenellated shape.

[0093] Figure 6 is a schematic and partial cross-sectional view of a coupling network according to one embodiment. Figure 6 illustrates, for example, an embodiment variant 201" of the coupling network 201 of the switch 200 of Figures 2A and 2B, it being understood that a person skilled in the art is able, upon reading this description, to adapt this variant to the coupling network 201 of variant 200' of Figure 3 and to that of the switch 400 of Figures 4A and 4B.

[0094] In the example shown, the regions 203 of the coupling network 201" laterally delimit trenches extending from the upper face of the central region 111 of the waveguide into the thickness of the region 111. The regions 203 have, for example, a crenellated shape.

[0095] 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, variant 200' of [Fig. 3] is combinable with the embodiment of Figures 4A and 4B, i.e., those skilled in the art can, for example, foresee that, in the switch 400, the central portion 111 of the waveguide 109 has a tapered portion 111T flaring out along the direction of propagation of the control signal of the switch 400.

[0096] Finally, the practical implementation of the described embodiments and variants is within the grasp of a person skilled in the art, based on the functional indications given above. Although Figures 2A, 2B, 3, 4A, and 4B illustrate examples of embodiments of switches 200, 200', and 400 in which the coupling network 201 is interposed vertically between the support substrate 105 and the phase-change material region 107, this example is not limiting, and the switches 200, 200', and 400 may, as a variant, have a structure in which the phase-change material region 107 is interposed vertically between the support substrate 105 and the coupling network 201. In this variant, the reflective layer 205 is, for example, formed on the side of a face of the coupling network 201 opposite the support substrate 105.

[0097] Furthermore, the embodiments described are not limited to the particular examples of materials and dimensions mentioned in this description.

Claims

Demands

1. Switch (200; 200'; 400) based on a phase-change material, comprising: - a region (107) in said phase-change material connecting first (101A) and second (101B) conduction electrodes of the switch; and - a coupling network (201; 201'; 201") for a laser signal to activate the switch, located opposite a face of the region (107) in said phase-change material.

2. Switch (200; 200'; 400) according to claim 1, wherein the coupling network (201; 201'; 201") comprises, directly above the region (107) in said phase-change material, an alternation of first regions (203) in a first material having a first optical index and second regions (103) in a second material having a second optical index strictly lower than the first optical index.

3. Switch (400) according to claim 2, wherein the coupling network (201; 201'; 201") is configured to irradiate a constant optical power along a propagation direction (Ox) of the switch activation laser signal.

4. Switch (400) according to claim 3, wherein the first regions (203) are distributed at constant pitch and have a decreasing width (LE) along the direction (Ox) of propagation of the laser signal activating the switch.

5. Switch (200; 200') according to claim 2, wherein the coupling network (201; 201'; 201") is configured to irradiate decreasing optical power along a direction (Ox) of propagation of the switch activation laser signal, the first regions (203) being spaced at constant pitch and having a constant width (LE).

6. Switch (200; 200'; 400) according to any one of claims 2 to 5, wherein the coupling network (201; 201'; 201") is located in the extension of a waveguide (109), the waveguide (109) comprising a central region (111) in said first material surrounded by a peripheral region (103) in said second material.

7. Switch (200; 200'; 400) according to claim 6, wherein the first material is silicon nitride and the second material is silicon oxide.

8. Switch (200'; 400) according to claim 6 or 7, wherein a portion (111T) of the central region (111) of the waveguide has: - a tapered shape narrowing in the vicinity of the region (107) in said phase-change material; or - a flared shape widening in the vicinity of the region (107) in said phase-change material.

9. Switch (200; 200'; 400) according to any one of claims 1 to 8, further comprising a support substrate (105), the coupling network (201; 201'; 201") being interposed between the support substrate (105) and the region (107) in said phase-change material.

10. Switch (200; 200'; 400) according to claim 9, further comprising a reflective layer (205) interposed between the support substrate (105) and the coupling network (201; 201'; 201").

11. Switch (200; 200'; 400) according to claim 10, wherein the reflective layer (205) is made of silicon or silicon nitride.

12. Switch (200; 200'; 400) according to any one of claims 1 to 11, wherein the coupling network (201; 201'; 201") is separated from the layer (107) in said phase-change material by a distance greater than 100 nm.

13. Switch (200; 200'; 400) according to any one of claims 1 to 12, wherein the region (107) in said phase-change material has a width (wP) in a range from 1 to 100 pm, preferably from 10 to 100 pm, more preferably from 30 to 100 pm.

14. Switch (200; 200'; 400) according to any one of claims 1 to 13, wherein the first (101A) and second (101B) conduction electrodes are part of an antenna element of a transmitting array cell or reflecting array cell.

15. Switch (200; 200'; 400) according to any one of claims 1 to 14, 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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