Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
  • G01Q20/00—Monitoring the movement or position of the probe
  • G01Q20/02—Monitoring the movement or position of the probe by optical means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
  • G01Q20/00—Monitoring the movement or position of the probe
  • G01Q20/04—Self-detecting probes, i.e. wherein the probe itself generates a signal representative of its position, e.g. piezoelectric gauge
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
  • G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
  • G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
  • G01Q60/38—Probes, their manufacture, or their related instrumentation, e.g. holders
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B2006/12133—Functions
  • G02B2006/12138—Sensor
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
  • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
  • G02B6/29331—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by evanescent wave coupling
  • G02B6/29335—Evanescent coupling to a resonator cavity, i.e. between a waveguide mode and a resonant mode of the cavity
  • G02B6/29338—Loop resonators

Definitions

• the present description generally concerns integrated circuits, and, more particularly, photonic integrated circuits.
• Known photonic circuits include an optical or opto-mechanical resonator comprising, for example, a disk, a circular ring or a closed loop in the shape of an athletics track ("racetrack” in English), and having a part which extends beyond an edge of the substrate on which the circuit is formed.
• the part of the resonator which projects beyond the edge of the substrate is configured to interact with a surface, for example a surface to be imaged, which modifies the resonance wavelength of the optical resonator, for example following a modification of the effective optical index of the optical resonator resulting from the material placed opposite the protruding part of the resonator and the distance between this material and the protruding part of the resonator, and/or for example following a deformation of the resonator resulting from a force exerted on the opto-mechanical resonator by the surface.
• Such photonic circuits serve, for example, as force probes for atomic force microscopes (AFM).
• Figure 1 illustrates, through a schematic top view, a theoretical, or ideal, example of such a photonic circuit 1
• Figure 2 being a schematic sectional view of this circuit 1 taken in the plane AA of the figure 1.
• Circuit 1 comprises a substrate 100, for example made of silicon, only part of which is shown in Figures 1 and 2.
• An optical or opto-mechanical resonator 102 for example made of silicon, is fixed to the substrate 100 by an anchoring pad 104, for example made of silicon nitride, silicon oxide or polycrystalline silicon, so that the resonator is suspended above the substrate 100 and a part of the resonator 102 extends beyond an edge or flank 110 of the substrate, or, more generally, an edge 110 of circuit 1.
• the resonator 102 comprises a disk 106 and a tip 108 fixed to the periphery of the disk 106. The tip 108 is oriented in a direction parallel to the face of the substrate 100, called the front face of the substrate 100, to which the pad is fixed.
• the edge 110 is orthogonal to the front face of the substrate 100.
• Figures 1 and 2 are ideal in that the intersection of the side 110 with the front surface of the substrate 100 beyond which a part of the resonator 102 protrudes is arranged between the pad 104 and the part of the resonator 102 which extends beyond the substrate 100, for example between the pad 104 and the tip 108.
• Figure 3 is a schematic sectional view taken in a section plane similar to plane AA of Figure 1, illustrating circuit 1 at a manufacturing stage.
• the resonator 102 and the pad 104 are embedded in a material 300 which can be selectively etched with respect to the resonator 102 and the substrate 100.
• the material 300 can also be selectively etched with respect to the material of the pad 104.
• the material 300, the resonator 102 and the pad 104 forms a layer resting on and in contact with the front face of the substrate 100.
• the entire resonator 102 is, in a direction orthogonal to the front face of the substrate 100, facing the substrate 100, or, put differently, the substrate 100 still extends under the entire resonator 102 and at -of the.
• an etching for example a deep reactive ion etching (DRIE) is carried out from the rear face of the substrate 100 to the front face of the substrate 100. , to remove a part of the substrate 100 not coated with an etching mask 301 and form the sidewall 110 of the substrate 100 ( Figures 1 and 2).
• the desired position of the sidewall 110 is represented by a dotted line 302.
• the mask 301 covers the part of the substrate 100 which must be left in place (to the left of the line 302 in Figure 3) and does not cover the part of the substrate 100 which we wish to remove by etching (at right of line 302 in figure 3).
• the material 300 is removed by selective etching with respect to the material(s) of the substrate 100, the resonator 102 and, for example, the pad 104 when the material 300 is selectively engravable with respect to the material of the pad 104.
• the time of selective etching of the material 300 with respect to the(x ) material (x) of the substrate 100 and the resonator 102 is limited so as to leave the pad 104 in place.
• the accesses of the etching solution to the pad 104 are configured to allow the pad 104 to be left in place while controlling the etching time.
• the etching through the substrate 100 has an angle 0 relative to the ideal cutting plane 302, and, in addition, a dispersion d0 over the value of this angle 0.
• the dispersion d0 and the thickness E of the substrate 100 which is several hundred micrometers, the engraving emerges on the side of the front face of the substrate 100 with a misalignment of more or less minus A relative to the ideal cutting plane 302.
• A is equal to 7 pm.
• the alignment of the mask 301 with the targeted cutting line 302 has an error of more or less d, with d for example equal to 500 nm, which further adds to the uncertainty as to where the engraving ends on the side of the front face of the substrate 100.
• the maximum dimensions that the suspended part of the resonator 102 can have are limited by the position of the pad 104. Due to the uncertainty as to where the etching ends on the side of the front face of the substrate 100, the part of the resonator 102 which extends beyond the substrate 100 may not extend sufficiently beyond of the substrate 100, or the substrate 100 can be etched under the pad 104, which renders circuit 1 inoperative.
• such a sloped flank 110 can be obtained with a monocrystalline silicon substrate 100 using anisotropic etching, for example anisotropic wet etching, for example by means of an etching solution comprising hydroxide.
• potassium (KOH) tetramethylamonium hydroxide (TMAH) or ethylenediamine pyrocatechol (EDP)
• TMAH tetramethylamonium hydroxide
• EDP ethylenediamine pyrocatechol
• One embodiment overcomes all or part of the drawbacks of known photonic circuits in which an optical or opto-mechanical resonator extends beyond the substrate of the circuit, for example all or part of the disadvantages linked to the manufacture of these known circuits.
• One embodiment provides a device comprising: a substrate; a first layer comprising a first part attached to a front face of the substrate and a second part suspended above a plane including the front face of the substrate; and an optical, opto-mechanical or mechanical resonator attached to the second part (202B) of the first layer and suspended under said second part of the first layer and above the plane comprising the front face of the substrate, only a first part of the resonator being, in a direction orthogonal to the front face of the substrate, facing the substrate and/or the first layer.
• the resonator comprises a second part which, in a direction orthogonal to the front face of the substrate, faces neither the first layer nor the substrate.
• the second part of the resonator in a direction parallel to the front face of the substrate, is arranged beyond an edge of the substrate and beyond an edge of the first layer.
• a dimension of the second part of the resonator is less than 50 pm.
• the device comprises a second layer; the second layer is placed between the first layer and the front face of the substrate; and the resonator is defined in the second layer.
• the device further comprises at least a third layer disposed between the front face of the substrate and the second layer, and at least one fourth layer disposed between the second layer and the first layer.
• the first part of the first layer rests on a stack of layers, the stack preferably comprising the second layer.
• the resonator comprises a circular ring, a loop in the shape of an athletics track or a disc.
• the resonator is fixed to the second part of the first layer by at least one anchoring pad.
• said at least one anchoring pad extends in height from the second layer to the second part of the first layer.
• said at least one anchoring pad is in contact with the disk; or said at least one anchoring stud is arranged inside a region delimited laterally by the ring and the device comprises holding arms each extending from an internal edge of the ring to said at least an anchoring pad; or said at least one anchoring stud is arranged inside a region delimited laterally by the closed loop, preferably in the center of this region, and the device comprises holding arms each extending from an internal edge from the closed loop to said at least one anchoring pad.
• the resonator further comprises a tip fixed to the external periphery of the disk, the ring or the closed loop.
• the second part of the resonator comprises the tip, the tip extending in length in a direction parallel to the front face of the substrate and, preferably, orthogonal to the intersection of said edge of the substrate with the front face of the substrate.
• the resonator is an optical or opto-mechanical resonator and the device further comprises a waveguide defined in the same layer as the resonator, a portion of the waveguide being optically coupled to the resonator.
• the portion of the waveguide is suspended between the second part of the first layer and a plane comprising the front face of the substrate, preferably by holding arms defined in the same layer as the optical resonator and each extending from said portion of the waveguide to an anchoring pad fixed to the substrate or to the second part of the first layer.
• Figure 1 represents, in a top view, an ideal example of a photonic circuit
• Figure 2 represents a schematic sectional view taken in a plane AA of Figure 1;
• Figure 3 represents a schematic sectional view illustrating a manufacturing step of the circuit of Figures 1 and 2;
• Figure 4 shows, in a schematic top view, an embodiment of a photonic circuit;
• Figure 5 represents a schematic sectional view taken in the plane AA of Figure 4;
• Figure 6 represents a schematic sectional view taken in the plane BB of Figure 4.
• Figure 7 shows a schematic sectional view taken in the plane BB of Figure 4 according to an alternative embodiment
• Figure 8 shows, in a schematic top view, another alternative embodiment of the photonic circuit of Figures 4 to 7;
• Figure 9 represents a schematic sectional view taken in the plane AA of Figure 8.
• Figure 10 shows, in a schematic top view, yet another alternative embodiment of the photonic circuit of Figures 4 to 7;
• Figure 11 shows, in a schematic top view, yet another alternative embodiment of the photonic circuit of Figures 4 to 7;
• Figure 12 represents, in a schematic top view, yet another alternative embodiment of the photonic circuit of Figures 4 to 7.
• a photonic circuit comprising a layer, called a support layer, having a part fixed to a front face of the substrate of the circuit, and a suspended part above a plane of the front face of the substrate.
• the optical or opto-resonator mechanical is fixed to the suspended part of the support layer, the resonator then being suspended under the suspended part of the support layer, that is to say under a plane comprising a lower face of the support layer which is turned towards the front face of the substrate.
• Fixing the resonator to the lower face of the suspended part of the support layer allows that, in a direction orthogonal to the front face of the substrate, only a first part of the resonator faces the front face of the substrate and/or the underside of the support layer. Thus, in a direction orthogonal to the front face of the substrate, a second part of the resonator faces neither the substrate nor the support layer, and therefore extends beyond the substrate and the support layer.
• the support layer is thinner than the substrate, its thickness being for example a maximum of 100 ⁇ m, preferably a maximum of 10 ⁇ m.
• the uncertainty about where this engraving leads to on the lower face of the support layer is much lower than that about where an engraving made from the rear face of the substrate to the front face of the substrate leads to the front face of the substrate.
• Figure 4 represents, in a schematic top view, an embodiment of a photonic circuit 2, Figure 5 being a schematic sectional view taken in the plane AA of Figure 4 and Figure 6 being a schematic sectional view taken in plane BB of Figure 4. In these figures, only part of circuit 2 and its substrate 200 is shown.
• the photonic circuit 2, or device 2 comprises a substrate 200, for example a semiconductor substrate, for example made of silicon.
• circuit 2 is formed on the substrate 200.
• the substrate 200 has a thickness of several hundred micrometers, for example a thickness of at least 200 ⁇ m.
• Circuit 2 comprises a layer 202, called support layer 202.
• the thickness of layer 202 is less than 100 pm, for example substantially equal to 10 pm although this thickness can be by example less than 10 pm, or even less than 1 pm.
• Layer 202 comprises a first part 202A fixed to the substrate 200, and more particularly to a front face 204 of the substrate 200 (upper face in Figures 4 and 5).
• the part 202A of the layer 200 is fixed to the substrate 200, for example, by a stack 203 of layers, the stack 203 having a surface connected to a lower face 206 of the layer 202 and a surface connected to the front face of the substrate 200.
• part 202A of layer 200 is fixed by a pad made of the same material as that of layer 202 and/or substrate 200, this pad replacing stack 203 and having a connected surface to layer 202 and a surface connected to the front face of substrate 200.
• Layer 202 further comprises a second part 202B suspended above substrate 200, that is to say above a plane comprising face 204 of substrate 200.
• the two portions 202A and 202B of layer 202 are connected to each other.
• part 202B of layer 200 is an extension of part 202A of layer 200, or, said another way, layer 200 is continuous at the boundary between its portions 202A and 202B.
• the limit between parts 202A and 202B of layer 200 is indicated by a double dotted line 208 in Figure 4, and by a single dotted line also referenced 208 in Figures 5 and 6.
• the suspended part 202B of the layer 202 extends at least partly beyond an edge, or flank, 210 of the substrate 200 in a direction parallel to the plane of the face 204 and orthogonal to the intersection, or junction , of the sidewall 210 with the face 204 of the substrate 200.
• the position of the sidewall 204 under the layer 202 is indicated by a double dotted line also referenced 210.
• the sidewall 210 is represented as being orthogonal to the face 204 of the substrate 200 although, in practice, this sidewall 210 can be inclined relative to the normal to the face 204, either deliberately so that the side 210 is sloping as described previously in relation to Figures 1 to 3, or due to the etching slope of the substrate 200.
• the suspended part 202B of the layer 202 comprises a region arranged opposite the substrate 200 in a direction orthogonal to the face 204, although, in other examples not illustrated, part 202B of layer 200 does not include any region placed opposite the substrate in a direction orthogonal to face 204.
• Circuit 2 comprises an optical or opto-mechanical resonator 212.
• Resonator 212 is formed in, or defined in, a layer 214.
• Layer 214 is made of a material adapted to guide light at operating wavelengths. of circuit 2.
• layer 214 is made of silicon, silicon nitride, arsenic gallium or germanium.
• Layer 214 is placed between substrate 200 and layer 202.
• stack 203 of layers includes a portion of layer 214.
• the resonator 212 comprises a disk 212A.
• the resonator 212 includes a tip 212B fixed to the periphery of the disk 212A.
• the tip 212B extends in length in a direction parallel to the face 204 and orthogonal to the intersection of the flank 210 with the face 204 of the substrate 200.
• the resonator 212 and more particularly the disk 212A of the resonator 212 in the example of Figures 4 to 6, is fixed to the suspended part 202B of the support layer 202.
• the resonator 212 is suspended under the layer 202, and more precisely, under the suspended part 202B of this layer 202.
• the resonator 212 is also suspended above a plane comprising the face 204 of the substrate.
• the resonator 212 is fixed to the suspended part 202B of the layer 202 by at least one anchoring pad 216.
• Each pad 216 extends in height from the layer 214 to the layer 202, and , more particularly, up to face 206 of layer 202.
• each pad 216 extends between the disk 212A and the layer 202 and is placed sufficiently far from the edge of the disk 212A, for example more than 1 pm from the edge of the disk 212A, so as not to disturb the optical modes which are propagated in the disk 212A and are deported towards the periphery of the disk 212A. Fixing each pad 216 directly to the disk 212A but sufficiently far from the edge of the disk 212A makes it possible to limit the optical losses due to the fact that the optical modes propagated in the disk 212A are offset towards the periphery of the disk 212A, and therefore to increase the optical quality factor.
• a single pad 216 fixes the resonator 212 to the layer 202, this pad 216 then preferably being placed in the center of the disk 212A to limit as much as possible the optical losses resulting from the pad 216.
• the pad 216 is indicated by a cross.
• a first part of the resonator 212 (the part delimited by a dotted line in Figure 4) is, in a direction orthogonal to the face 204, placed opposite the substrate 200 and/or the suspended part 202B of the layer 200.
• the resonator 212 comprises a second part which, in a direction orthogonal to the face 204, is not arranged opposite the substrate 200 or the layer 202.
• This second part of the resonator 212 therefore extends beyond of the flank 210 of the substrate 200 and also beyond the layer 202, for example in a direction parallel to the face 204 and orthogonal to the intersection of the flank 210 with the face 204 of the substrate 200.
• the resonator 212 comprises the tip 212B
• the latter is part of the second part of the resonator 212, that is to say that no portion of the tip 212B is facing the substrate 200 or the layer 202 in a direction orthogonal to the face 204 of the substrate 200.
• the second part of the resonator 212 has, in a direction parallel to the face 204 and orthogonal to the intersection of the flank 210 with the face 204 of the substrate 200, a dimension or length less than 50 ⁇ m .
• layer 214 initially rests on a layer 218, itself resting on substrate 200. Then different elements, including resonator 212, are defined by etching in layer 214. At this step of etching layer 214, a portion of layer 214 can be left in place at the location of stack 203, so that stack 203 includes this portion of layer 214. Then, at least one layer 220 is formed on the whole and then layer 202 is formed, by deposition or transfer, on layer 220.
• the anchoring pad 216 can be made of the same material as the layer 202 by providing an opening in the layer 220 up to the resonator 212 which will be filled by the material of the layer 202 when it is deposited, or even made of another material by filling the opening in layer 220 with this material before forming layer 202.
• Layers 218 and 220 are made of materials that can be selectively etched relative to the materials of layers 214 and 202 and of substrate 200. Portions of layer 202 and of the substrate 200 are then removed during two respective etching steps, then portions of the layers 218 and 220 are removed by selective sacrificial etching with respect to the layers 202 and 214 and the substrate 200 to obtain the circuit 2.
• the engraving(s) of layers 218 and 220 are selective with respect to the material of pad 216.
• pad 216 is made of the same material as that of layer 220 and the person skilled in the art will then be in able to provide openings in the layer 202 and/or in the layer 214 so that by controlling the etching time of the layer 220, the pad 216 is left in place at the end of the etching.
• the layer 214 when the layer 214 is a semiconductor layer, for example made of silicon, and the layer 218 is an insulating layer, for example made of silicon oxide, the layer 214 can correspond to the semiconductor layer of a semiconductor on insulator (SOI) type structure formed on the substrate 200.
• SOI semiconductor on insulator
• the stack 203 comprises a portion left in place of layer 218, and may or may not include a portion left in place of layer 220 Indeed, it is possible that the stack 203 does not include any portion left in place of the layer 220, providing that, after the formation of the layer 220 on the layer 214, an opening is etched in the layer 220 up to the layer 214 at the location of the stack 203.
• the layer 202 is then formed by deposition on the layer 220, at the location of the stack, the material of layer 202 comes directly into contact with layer 214 due to the through opening in layer 220.
• Layer 202 can then be planarized.
• the stack is replaced by a pad made of a material identical to that of layer 202.
• a pad made of a material identical to that of layer 202.
• an opening is etched through it. the layers 220, 214 and 218 up to the substrate 200, so that, during the formation of the layer 202 by depositing the material of this layer on the layer 220, this material fills the opening and forms the pad there.
• layer 202 corresponds to a portion of a first substrate, for example semiconductor, for example silicon, layer 220 then resting on this first substrate and layer 214 then resting on layer 220.
• elements including the resonator 212, are formed in the layer 214.
• a filling material for example identical to the material of the layer 218, is deposited then planarized by stopping before or on the layer 214.
• the substrate 200 coated with layer 218 is then transferred to the structure before thinning the first substrate so as to leave only layer 202.
• the following steps to obtain circuit 2 are then similar to what has been described for the other example above.
• the layer 218 when transferring the substrate 200 onto the structure comprising the first substrate, the layer 218 can already form part of the structure and then rest on the layer 214 rather than coat the substrate 200, and the substrate 200 is then brought into contact with the layer 218 during the transfer step.
• layer 214 when layer 214 is a semiconductor layer, for example made of silicon, and layer 220 is an insulating layer, for example made of silicon oxide, layer 214 can correspond to the semiconductor layer of a semiconductor on insulator (SOI) type structure formed on the first substrate.
• SOI semiconductor on insulator
• circuit 2 is only examples, and the person skilled in the art is able, from the present description, to provide other manufacturing processes. of circuit 2 using steps each being usual in the manufacture of photonic circuits.
• the person skilled in the art will be able to adapt the examples of manufacturing processes described above to obtain a stack 203 comprising a portion of each of the layers 220, 214 and 218, or a stack 203 comprising only a portion of each of layers 220 and 214, or a stack 203 comprising only a portion of each of layers 218 and 214, or a stack 203 comprising only a portion of layer 214, or even to obtain a pad made of the material of layer 202 and /or the substrate 200 in place of the stack 203.
• circuit 2 comprises only a single layer 220 and a single layer 218.
• layer 220 may correspond to a plurality of layers stacked on top of each other and/or layer 218 may correspond to a plurality of layers stacked on top of each other.
• the two sacrificial layers 218 and 220 are made of the same material, which can be etched selectively with respect to the material(s) of the layers 214 and 202, of the substrate. 200, and, for example, pad 216.
• layers 218 and 220 can be made of different materials, each selectively etchable with respect to the material(s) of layers 214 and 202, of substrate 200 and, for example, pad 216.
• the substrate 200 is made of silicon or arsenic-gallium.
• layer 218 is a layer of silicon oxide or a photonic polymer such as for example BCB benzocyclobutene.
• layer 220 is a layer of silicon oxide or a photonic polymer such as for example BCB benzocyclobutene.
• the pad 216 is made of silicon, silicon nitride or silicon oxide.
• the thickness of layer 214 is between 40 and 1000 nm, for example between 50 and 500 nm.
• the thickness of layer 220 is greater than 500 nm, so that the portion of layer 202 placed above resonator 212 does not modify the optical properties of resonator 212.
• the thickness of the layer 218 is greater than 500 nm so that the substrate 200 is sufficiently distant from the resonator 212 so as not to modify its optical properties.
• the layer 218 is, for example, arranged between the face 204 of the substrate 200 and the layer 214
• the layer 220 is, for example , arranged between layer 214 and face 206 of layer 202.
• circuit 2 does not comprise any layer other than layer 218 between face 204 of substrate 200 and layer 214, and does not does not include any layer other than layer 220 between layer 214 and face 206 of layer 202.
• the person skilled in the art is able to adapt the materials of the layers 202, 214, 218 and 220, of the substrate 200 and, for example, of the pad 216 while retaining the etching selectivities indicated previously between the substrate 200 and layer 218, layers 218 and 220 relative to layers 214 and 202 and substrate 200, for example when layer 214 is made of a material other than silicon.
• the circuit 2 comprises a waveguide 222 formed in, or defined in, the layer 214.
• This waveguide 222 comprises a portion 224 optically coupled to the resonator 212.
• the portion 224 of the waveguide 222 is, like the resonator 212, suspended under a plane comprising the face 206 of the layer 202 and above a plane comprising the face 204 of the substrate 200.
• the portion 224 of the waveguide 222 is suspended above the substrate 200 and under the layer 202.
• the portion 224 of the waveguide 222 is fixed to the substrate 200, and more particularly to the face 204 of the substrate 200.
• the circuit 2 comprises holding arms 226 each having a end connected to the portion 224 of the waveguide 222, and an opposite end connected to an anchoring pad 228, itself connected to the face 204 of the substrate 200.
• the pads 228 are each marked by a cross.
• Each pad 228 is, for example, made of a material allowing the etching of the sacrificial layers 218 and 220 to be selective with respect to this material.
• each pad 228 is made of the same material as that of layer 220 and/or 218, the removal of layers 218 and 220 by selective etching with respect to the material(s) of layer 214 , of the layer 220 and the substrate 200 then being implemented by controlling the etching time so as to leave the pads 228 in place at the end of this etching.
• the accesses of the etching solution to the pads 228 are configured to allow the pads 228 to be left in place while controlling the etching time.
• each holding arm 226 corresponds to a beam or to several beams placed end to end to form at least one meander.
• the portion 224 of the waveguide 222 is arranged between the resonator 212 and the stack 203 of layers 218, 214, 220 on which rests the part 202A of the layer 202 .
• Figure 7 represents a schematic sectional view taken in the plane BB of Figure 4 according to an alternative embodiment of circuit 2.
• Circuit 2 of Figure 7 differs from that of Figures 4 to 6 only in that the portion 224 of the waveguide 222 is, in the alternative embodiment of Figure 7, fixed to the suspended part 202B of the layer 202 rather than the substrate 200.
• the anchoring pads 228 are no longer connected to the substrate 200 but to the part 202B of the layer 202, and, more particularly, to the face 206 of the layer 202
• the pads 228 are then similar or identical to the pads 216 ( Figures 4 and 5).
• connection of the pad 216 to the suspended part 202B of the layer 202 rather than to the substrate 200 makes it possible to release the constraints on the positioning of the pad 216 which result from the etching of the substrate 200 from its rear face to its front face to define the sidewall 210
• connecting the pads 228 to the suspended part 202B of the layer 202 rather than to the substrate 200 makes it possible to relax the constraints on the positioning of the pads 228.
• Figure 8 represents, in a schematic top view, another alternative embodiment of the photonic circuit 2 of Figures 4 to 6, Figure 9 being a schematic sectional view taken in the plane AA of Figure 8.
• circuit 2 differs from what has been described in relation to Figure 7 in that the resonator 212 does not include any part which, in a direction orthogonal to the face 204 of the substrate 200, is opposite of the substrate 200.
• the resonator 212 comprises a first part which, in a direction orthogonal to the face 204, is opposite the suspended part 202B of the layer 202, and a second part which, in this direction, is not facing neither the substrate 200 nor the layer 202.
• the portion 224 of the waveguide 222 is fixed to the suspended part 202B of the layer 202.
• this portion 224 of the guide wave 222 may also not include any part which, in a direction orthogonal to the face 204, is placed opposite the substrate 200.
• the portion 224 of the waveguide 222 is, in a direction orthogonal to the face 204, arranged at least partly opposite the substrate 200, the pads 228 can then be connected either to the substrate 200, or to the suspended part 202B of layer 202.
• Figure 10 represents, in a schematic top view, yet another alternative embodiment of the photonic circuit 2 of Figures 4 to 9.
• Circuit 2 according to this variant embodiment differs from circuits 2 described previously in relation to Figures 4 to 9 by the shape of the suspended part 202B of layer 202.
• this suspended part 202B has a substantially rectangular shape, and therefore has a straight edge 1000 (see Figures 4 to 9) at the same time. beyond which the resonator 212 projects in a direction parallel to the face 204 of the substrate 200 and orthogonal to the intersection of the flank 210 with the front face 204 of the substrate 200.
• the suspended part 202B of the layer 202 has a different shape, an example of which is illustrated in Figure 10.
• the resonator 212 comprises a second part which, in a direction orthogonal to the face 204 of the substrate 200, is neither facing the substrate 200, nor facing the suspended part 202B of the layer 202, and which, in a direction parallel to the face 204 of the substrate 200 and orthogonal to the intersection of the sidewall 210 with the front face 204 of the substrate 200, protrudes beyond the suspended part 202B of the layer 202.
• the portion 224 of the waveguide 222 does not include any part disposed facing the substrate 200 in a direction orthogonal to the face 204 of the substrate 200 and the pads 228 are then connected to the part 202B of the layer 202, in other examples not illustrated, this portion 224 of the waveguide 222 is arranged opposite the substrate 200 in a direction orthogonal to the face 204 of the substrate 200, the pads 228 which can then be connected either to the substrate 200 or to the suspended part 202B of the layer 202.
• the resonator 212 does not include any part which is arranged opposite the substrate 200 in a direction orthogonal to the face 204 of the substrate 200.
• the resonator 212 can comprise, as in the example of Figures 4 to 6, only one part which is arranged opposite the substrate 200 in a direction orthogonal to the face 204 of the substrate 200.
• Figure 11 represents, in a schematic top view, yet another alternative embodiment of the photonic circuit 2 of Figures 4 to 10.
• circuit 2 differs from circuits 2 according to the embodiments and variant embodiments described previously in relation to Figures 4 to 10 in that it does not include a disk 212A, but a circular ring 212C.
• the ring 212C is attached to the suspended part 202B of the layer 202.
• the ring 212C is fixed to the suspended part 202B of the layer 202 by at least one anchoring stud 216 and at least one holding arm 1100, for example three arms 1100 in the example of the Figure 11 although in other examples not illustrated the circuit 2 comprises only a single arm 1100, two arms 1100 or more than three arms 1100.
• Each pad 216 extends in height from the layer 202 to a plane comprising the face of layer 214 facing layer 202.
• Each arm 1100 is similar to arms 226 and is therefore defined in layer 214 (not referenced in Figure 11).
• Each arm 1100 extends from an edge of the ring 212C to a pad 216. In other words, each arm 1100 has one end connected to the ring 212C and an opposite end connected to a pad 216.
• each pad 216 is arranged inside the ring 212C, that is to say that each pad 216 is arranged in a region delimited laterally by the internal edge of the ring 212C, and is placed sufficiently far from the internal edge of the ring, for example more than 1 pm from the edge of the ring 212C, so as not to disturb the optical modes which are propagated in the ring 212C.
• each arm 1100 extends from an internal edge of the ring 212C to a corresponding stud 216.
• each pad 216 inside the ring 212C and sufficiently far from the internal edge of the ring 212C makes it possible to limit optical losses because the optical modes propagated in the ring 212C are offset towards the external edge of the 212C ring, and therefore increase the optical quality factor.
• a single pad 216 fixes the resonator 212 to the layer 202, this pad 216 then preferably being arranged in the center of the ring 212C to limit as much as possible the optical losses resulting from the pad 216.
• a single pad 216 fixes the resonator 212 to the layer 202, this pad being arranged inside the resonator 212 but offset from the center of the ring.
• Each holding arm 1100 can then comprise a first portion going from the internal edge of the ring 212C to the center of the ring 212C and a second portion, common to all the holding arms 1100, going from the center of the ring 212C up to the single pad 216.
• the resonator 212 includes the optional tip 212B.
• Figure 12 represents, in a schematic top view, yet another alternative embodiment of the photonic circuit 2 of Figures 5 to 11.
• circuit 2 differs from circuits 2 according to the embodiments and variant embodiments described previously in relation to Figures 4 to 11 in that it does not include a disk 212A or a circular ring 212C, but a closed loop 212D for example in the shape of an athletics track ("racetrack" in English), or, said differently, for example in the shape of an oblong ring.
• the ring 212D comprises two parallel rectilinear portions connecting two portions in Semi circle.
• the two semi-circle portions are connected to each other by two non-parallel rectilinear portions when the two semi-circle portions do not have the same radius, or, more generally, by two portions which can be straight or have meanders.
• Loop 212D is attached to suspended portion 202B of diaper 202.
• the loop 212D is fixed to the suspended part 202B of the layer 202 by at least one anchoring stud 216 and at least one holding arm 1100.
• Each stud 216 extends in height from the layer 202 up to a plane comprising the face of layer 214 facing layer 202.
• Each arm 1100 is similar to arms 226 and is therefore defined in layer 214 (not referenced in Figure 12).
• Each arm 1100 extends from an edge of the loop 212D to a pad 216. In other words, each arm 1100 has one end connected to the loop 212D and an opposite end connected to a pad 216.
• each pad 216 is arranged inside the ring 212D, that is to say that each pad 216 is arranged in a region delimited laterally by the internal edge of the loop 212D, and is placed sufficiently far from the internal edge of the loop 212D, for example more than 1 pm from the edge of the loop 212D, so as not to disturb the optical modes which are propagated in the loop 212D.
• each arm 1100 extends from an internal edge of the loop 212D to a corresponding stud 216.
• each pad 216 inside the loop 212D and sufficiently far from the internal edge of the loop 212D makes it possible to limit optical losses due to the fact that the optical modes propagated in the ring 212C are offset towards the external edge of the 212D loop, and therefore increase the optical quality factor.
• the loop 212D is fixed to the layer 202 by two studs 216 arranged inside the loop 212D and four arms 1100.
• Each arm 1100 extends from an internal edge of the loop 212D to a pad 216.
• each arm 1100 has one end connected to the internal edge of the loop 212D and an opposite end connected to a pad 216.
• each arm 1100 has one end connected to a stud 216 and an opposite end connected to another stud 216.
• a single arm 1200 connects the two studs 216.
• a single pad 216 fixes the resonator 212 to the layer 202, this pad 216 then preferably being placed in the center of the loop 212D to limit as much as possible the optical losses resulting from the pad 216
• this single pad 216 can be arranged inside the resonator 212 but offset relative to the center of the loop 212D, each holding arm 1100 can then comprise a first portion going from the internal edge of the loop 212D to the. center of the loop 212D and a second portion, common to all the holding arms 1100, going from the center of the loop 212D to the single stud 216.
• the resonator 212 includes the optional tip 212B.
• the sidewall 210 can correspond to an external lateral edge of the substrate 200 or to an edge of the substrate 200 corresponding to the edge of a through opening etched through it. the substrate 200.
• structure 212 is an optical or opto-mechanical resonator defined in layer 214
• the structure 212 comprising the disk 212A, the circular ring 212C or the closed loop 212D has no optical function and is used as a mechanical resonator 212.
• This mechanical resonator 212 is fixed to the layer 202 in the same way as this which has been described previously, for example by at least one pad 216 and at least one arm 1100.
• the pads 216 are arranged between the disc 212A and the layer 202 or inside the ring 212C or the loop 212D. Indeed, anchoring from the inside allows higher mechanical quality factors thanks to reduced mechanical coupling of the resonator 212 with the acoustic modes of the substrate 200.
• the mechanical resonator 212 is fixed to the layer 212 by a single pad 216 disposed in the center of the disk 212A or at the center of the ring 212C or the center of the loop 212D, where the amplitude of the mechanical mode used is the lowest, which makes it possible to further reduce the mechanical coupling of the resonator 212 with the acoustic modes of the substrate 200
• a single pad 216 fixes the resonator 212 to the layer 202, this pad being arranged inside the resonator 212 but offset from the center of the disc 212A, the ring 212C or. of loop 212D.
• each holding arm 1100 can then comprise a first portion going from the internal edge of the ring 212C to the center of the ring 212C and a second portion, common to all the holding arms 1100, going from the center of the ring 212C to the single stud 216.
• Reading the movement of the mechanical resonator 212 can then be done by non-optical (capacitive for example) or even optical transduction techniques using an optical resonator separated from the mechanical resonator 212 by a space varying with the movements of the mechanical resonator , and by measuring variations in resonance wavelength of the optical resonator resulting from these variations in the space between the mechanical resonator 212 and the optical resonator.

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• 2022
  • 2022-12-08 FR FR2212956A patent/FR3143140A1/fr active Pending
• 2023
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