INTEGRATED NANO-COMPONENT OPTICAL DEVICE
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- UNIVERSITY OF TECHNOLOGY OF TROYES
- Filing Date
- 2023-04-25
- Publication Date
- 2026-07-17
Abstract
Description
Title of the invention: INTEGRATED OPTICAL DEVICE WITH NANO-COMPONENT Technical field
[0001] The present description relates to a nano-component integrated optical device. Prior art
[0002] The design and manufacture of optical devices in the form of integrated optical circuits have numerous advantages, in particular with regard to their size, their price, the alignment of the optical components within each device which is ensured during its manufacture, etc. In addition, several technologies for manufacturing integrated optical circuits have been developed, which implement different compositions of materials as well as different steps for developing each integrated optical circuit.
[0003] Furthermore, optical devices whose function is to emit or detect photons individually, known as single-photon devices, have been designed for several years. Such devices can each implement at least one nano-component such as a nanocrystal with a colored center, to emit or absorb one or more photon(s) on demand. They are envisaged for numerous applications, including quantum optical transmission applications.
[0004] In particular, the design and development of single-photon integrated optical devices are the subject of numerous efforts. The article entitled “On-Chip Hybrid Photonic-Plasmonic Light Concentrator for Nanofocusing in an Integrated Silicon Photonics Platform”, by Ye Luo et al., Nano Letters, 2015, Vol. 15, pp. 849-856, proposes to use a metallic nano-antenna to optically couple a waveguide to a nano-component in an integrated optical circuit. Thus, it is known to realize a nano-component integrated optical device, which comprises: - an integrated optical circuit substrate, supporting a waveguide adapted to guide light which has a wavelength between 350 nm (nanometer) and 2000 nm when this light propagates in a vacuum; - a metallic nano-antenna, which is supported by the substrate, with a base portion of the nano-antenna which is optically coupled to the waveguide, and this nano-antenna being designed to concentrate in a focal area an electric field resulting from light which has reached the base portion of the nano-antenna by being guided by the waveguide; and - an optical component, called a nano-component, which has at least one dimension between 1 nm and 100 nm and which is rigidly connected to the substrate, this nano component being located against or in the focal zone of the nano-antenna and capable of absorbing a photon of light which has the wavelength in vacuum between 350 nm and 2000 nm.
[0005] Such an integrated optical device can have two operations which are inverse in their principles. For operation as a light detector, light is injected from an external source into the waveguide, and the nanocomponent acting as a photonic nano-sensor absorbs a photon of this light which has been focused on it by the nano-antenna. For operation as a single photon source, the nanocomponent acting as a nano-emitter produces a photon which is transmitted to the waveguide by the nano-antenna, then propagates in a guided manner inside the waveguide.
[0006] One challenge of this type of integrated optical devices is to increase the efficiency of the optical coupling produced by the nano-antenna between the waveguide and the nanocomponent. Technical problem
[0007] From this situation, an aim of the present invention is to increase the optical coupling that exists between the waveguide and the nano-component. Thus, for operation as a light detector, the invention aims for a photon to be absorbed by the nano-component for a reduced quantity of light that is brought by the waveguide to the nano-antenna.
[0008] Another object of the invention relates to operation as a single photon source, and consists in that for this operation, a photon which is produced by the nanocomponent is transmitted to the waveguide with a higher probability, in order to propagate there in a guided manner.
[0009] An additional aim for the operation as a single photon source is that the photon which is produced by the nano-component and transmitted to the waveguide propagates in the latter in a direction which is predetermined, with a higher probability. Summary of the invention
[0010] To achieve at least one of these aims or another, one aspect of the invention provides a novel integrated optical device which comprises the integrated optical circuit substrate, the nano-antenna and the nano-component combined in the manner indicated above, and which further comprises: - a reflector, which is rigidly connected to the substrate and located on one side of the nanocomponent opposite the nano-antenna, so as to reinforce an efficiency of concentration of the electric field in the focal zone, compared to a reference concentration which would be produced by the nano-antenna in the device in the absence of the reflector, for light with a wavelength in vacuum between 350 nm and 2000 nm which reaches the base part of the nano-antenna by being guided by the waveguide.
[0011] The reflector that is added by the invention to the device is therefore part of the integrated optical circuit in the same way as its other components, in particular in the same way as the nano-antenna. This reflector reinforces the concentration of the electric field that results from the light brought by the waveguide to the nano-antenna, such that this concentration is effective at the level of the nano-component, so that a photon absorption by the nano-component occurs for a lower power of the light that is brought by the waveguide. Indeed, a part of the light that is brought by the waveguide and that passes through the focal zone without having been absorbed by the nano-component is reflected by the reflector and passes through the focal zone again, so that the probability that a photon of this light is absorbed by the nano-component is increased by the additional possibility of absorption offered by this second crossing of the focal zone.The device of the invention thus constitutes a light detector which has increased detection efficiency.
[0012] The efficiency of concentration of the electric field in the focal zone can be quantified using the Purcell factor relative to the nano-component: the addition according to the invention of the reflector in the integrated optical device produces an increase in the Purcell factor, compared to the same device without a reflector.
[0013] For use of the device of the invention as a single photon source, the addition of the reflector has the effect that a photon that is produced by the nano-component in a direction that is opposite to the nano-antenna is reflected towards the latter to be transmitted by it to the waveguide. Furthermore, the reflector can be designed, with respect to the nano-antenna, so that each photon that is produced by the nano-component is transmitted to the waveguide to propagate inside it most often in a direction that is oriented from the side of the reflector towards the side of the nano-antenna.
[0014] In various embodiments of the invention, the reflector may have various levels of optical coupling to the waveguide, including no optical coupling or minimal optical coupling between the reflector and the waveguide. In particular, the reflector may have optical coupling to the waveguide that is weaker than that of the nano-antenna to the waveguide. The reflector may further have plasmonic oscillation modes whose characteristics are variable, in particular with respect to other characteristics of plasmonic oscillation modes that are relative to the nano-antenna.
[0015] An advantage of the invention is that the addition of the reflector to the integrated optical circuit does not lengthen or does not significantly lengthen a manufacturing process of this integrated optical circuit. Indeed, the reflector can be produced during the same steps of development than the nano-antenna.
[0016] In preferred embodiments of the invention, at least one of the following additional features may be optionally reproduced, alone or in combination of several of them: - the nano-antenna, the nano-component and the reflector can be aligned parallel to a longitudinal direction of the waveguide; - the nano-antenna, the nano-component and the reflector can form an arrangement which is symmetrical with respect to a plane which is parallel to the longitudinal direction of the waveguide and perpendicular to a surface of the integrated optical circuit substrate, this surface supporting the waveguide; - the reflector may be metallic, in particular based on aluminum (Al), gold (Au) or silver (Ag), or based on an alloy which includes aluminum, gold or silver; - the nano-antenna and the reflector may be two portions of the same metal layer which is supported by the substrate, the two portions of the metal layer being located on one side of the waveguide which is opposite the substrate. In this case, a thickness of the metal layer may be between 10 nm and 50 nm, preferably between 25 nm and 35 nm; - the reflector may have a boundary which is oriented towards the nano-antenna, this boundary having one of the following forms: . a tip shape which is directed towards the focal area, with a radius of curvature which is less than 500 nm, preferably between 5 nm and 500 nm, at this tip; and . a concave shape that is turned towards the focus area; - the reflector may be of the Bragg reflector type; and - the device may further comprise a portion of coupling layer which is intermediate between the waveguide and the nano-antenna, this portion of coupling layer being adapted to increase a transfer of light power between the waveguide and the nano-antenna compared to a reference transfer which would exist in the device between the same waveguide and the same nano-antenna but in the absence of a portion of coupling layer, for light which has the wavelength in vacuum between 350 nm and 2000 nm when this light is brought by the waveguide to the base part of the nano-antenna.
[0017] Preferably, no portion of layer for the purpose of increasing light power transfer may be provided between the waveguide and the reflector, or a portion of layer may be provided between the waveguide and the reflector, which is adapted to reduce a light power transfer which would be likely to occur between this waveguide and this reflector, compared to another transfer of reference which would exist in the device between the same waveguide and the same reflector but in the absence of a portion of coupling reduction layer, again for light which has the wavelength in vacuum between 350 nm and 2000 nm when this light is brought by the waveguide to the base part of the nano-antenna.
[0018] In some embodiments of the invention for which the waveguide to which the nano-antenna is coupled is called an intermediate waveguide, the device further comprises, in addition to this intermediate waveguide, a primary waveguide which is also adapted to guide light having the wavelength in vacuum between 350 nm and 2000 nm, the intermediate waveguide and the primary waveguide having light guiding directions which are parallel and being optically coupled to each other, so that the light, when injected into the primary waveguide, is at least partially transferred to the intermediate waveguide, and then brought by the intermediate waveguide to the base part of the nano-antenna. Possibly, the intermediate waveguide and the primary waveguide may be superimposed in a direction which is perpendicular to a surface of the substrate.For example, the primary waveguide may be buried in the substrate below its surface, and the intermediate waveguide may be located at or above that substrate surface. Alternatively, the intermediate waveguide and the primary waveguide may be juxtaposed next to each other parallel to the substrate surface.
[0019] When the primary waveguide and the intermediate waveguide are superimposed, the device may further comprise a coupling layer between the primary waveguide and the intermediate waveguide, and which is adapted to produce between them a coupling by evanescent fields.
[0020] Generally for the invention, the nano-component may be a photonic nano-sensor which is adapted to absorb a photon of light with a wavelength in a vacuum between 350 nm and 2000 nm when this light is brought by the waveguide to the base part of the nano-antenna. The device of the invention then has a light detector operation. In this light detector operation, the photon can be absorbed by the nano-component with a higher probability when the light is brought by the waveguide to the base part of the nano-antenna with a propagation direction which goes from one side of the nano-antenna to one side of the reflector.
[0021] Alternatively, the nano-component may be a photonic nano-emitter which is adapted to produce a photon having a wavelength in vacuum between 350 nm and 2000 nm, and also included in a transmission spectral band of the waveguide. The device of the invention then has a source operation of single photon. In this operation as a single photon source, the photon which is produced by the nano-component can be transmitted to the waveguide by passing through the nano-antenna in plasmonic form, with a probability relative to a direction of propagation going from the side of the reflector to the side of the nano-antenna, for the photon in the waveguide, which is higher than another probability relative to another direction of propagation going from the side of the nano-antenna to the side of the reflector, also for the photon in the waveguide.
[0022] Finally, generally for the invention, the nano-antenna may comprise a plurality of disjointed metal segments which are offset between the base part of this nano-antenna and the focal zone. Such a constitution makes it possible to reduce energy and / or light losses which would be likely to occur in the nano-antenna. Brief description of the figures
[0023] The characteristics and advantages of the present invention will appear more clearly in the detailed description below of non-limiting exemplary embodiments, with reference to the appended figures among which:
[0024] [Fig. 1] is a perspective view of a first embodiment of the invention;
[0025] [Fig.2] corresponds to [Fig.l] for a second embodiment of the invention;
[0026] [Fig.3a] is a plan view which corresponds to the embodiments of [Fig.l] and [Fig.2] ;
[0027] [Fig.3b] corresponds to [Fig.3a] for a first possible variant compared to the embodiments of [Fig.l] and [Fig.2];
[0028] [Fig.3c] also corresponds to [Fig.3a] but for a second possible variant compared to the embodiments of [Fig.l] and [Fig.2]; and
[0029] [Fig.4] is a plan view of another alternative embodiment of the invention. Detailed description of the invention
[0030] For the sake of clarity, the dimensions of the elements shown in these figures do not correspond to actual dimensions or to actual dimensional ratios. Furthermore, identical references indicated in different figures designate identical elements or elements which have identical functions.
[0031] With reference to [Fig.l], an integrated optical circuit substrate 10 has an upper surface S on which a waveguide 2 has been formed. For example, the substrate 10 may be made of silica (SiO2) or a glass-like material, and the waveguide 2 is made of a material that is transparent to radiation that has a nominal wavelength value in vacuum of between 350 nm and 2000 nm. For this radiation, the material of the waveguide 2 has a refractive index value that is greater than that of the material of the substrate 10. For example, the waveguide 2 may be made of silicon nitride (Si3N4), titanium oxide (TiO2), zinc oxide (ZnO), zinc sulfide (ZnS) or indium-doped tin oxide (ITO). In this way, the waveguide 2 may have a refractive index value that is greater than or equal to 2.0, while the substrate 10 has a refractive index value less than 1.7. The waveguide 2 may be made of a strip of the material with a high refractive index value, which is parallel to a longitudinal direction D2 on the surface S. The waveguide 2 that is thus made may be of the single-mode type for radiation that has the nominal wavelength value, for example with a width 12 of its material strip that may be about 400 nm, and a thickness e2 of this material strip that may be about 85 nm.
[0032] A nano-antenna 3 is arranged above the waveguide 2, for example in the form of a portion of metal layer, such as a portion of aluminum (Al) layer 30 nm thick. Parallel to the surface S, the portion of metal layer that constitutes the nano-antenna 3 may have the shape of an isosceles triangle, with two oblique edges Bi and B2 of the triangle that are of the same length and converge towards the point P3 of the isosceles triangle. An edge Bo of the portion of metal layer that constitutes the nano-antenna 3 constitutes the base of the isosceles triangle, being opposite its point P3. This edge Bo has been called the base part of the nano-antenna 3 in the general description of the present invention. The nano-antenna 3 that is thus constituted is positioned on the strip of the waveguide 2 so that the edge Bo is perpendicular to the longitudinal direction D2.For example, the edge Bo may be about 400 nm long, and each of the converging oblique edges Bi and B2 may be about 800 nm long. The apex angle of the isosceles triangle, at tip P3, is then about 23° (degree), and in practice, tip P3 may have a non-zero radius of curvature, while being less than 20 nm, for example between 5 nm and 20 nm. The tip P3 is thus superimposed, in a direction which is perpendicular to the surface S, on a median longitudinal axis of the waveguide 2. By proximity effect with the waveguide 2, the nano-antenna 3 is optically coupled by its base part Bo to the waveguide 2. For this reason, part of the power of a light which propagates in the waveguide 2 while having the nominal wavelength value in the vacuum, is transferred to the nano-antenna 3 in the form of excitations of at least one plasmonic oscillation mode of the latter.This (these) plasmonic oscillation mode(s) which are excited then create(s) an alternating electric field at the optical frequency of the light brought by the waveguide 2, which is concentrated in a zone ZF called the focus zone. The focus zone ZF is located in the immediate vicinity of the tip P3, approximately 50 nm in front of this tip parallel to the longitudinal direction D2.
[0033] Advantageously, a portion of coupling layer 23 may be intermediate between the waveguide 2 and the portion of metal layer which constitutes the nanoantenna 3. A person skilled in the art knows how to select a material and a thickness value for this portion of coupling layer 23, in order to maximize a proportion of the power which is transferred to the nanoantenna 3 in the form of excitation of plasmonic oscillation mode(s), relative to the power of the light which is guided by the waveguide 2 from an external source. For example, the portion of coupling layer 23 may have a peripheral limit which coincides with that of the portion of metal layer which constitutes the nanoantenna 3, parallel to the surface S, and have a thickness which is substantially equal to 30 nm when it is made of silica (SiO 2)-
[0034] A nano-component 4 is then fixed on the waveguide 2, so that it is in the focus zone ZF. An advantageous method for fixing the nano-component 4 precisely in the focus zone ZF may comprise depositing a photolithographic resin on the waveguide 2, possibly on the entire upper surface of the integrated optical circuit being manufactured, and crosslinking this resin selectively in the focus zone ZF using light, at the nominal wavelength value in vacuum relative to the waveguide 2, which is injected into this waveguide 2 already provided with the nano-antenna 3. This light is then concentrated in the focus zone ZF and causes crosslinking of the resin there selectively with respect to locations of the resin layer which are located outside the focus zone ZF. Alternatively, the resin can be crosslinked selectively in the focus zone ZF by electron lithography.The non-crosslinked resin is then dissolved in a suitable developing liquid, so that resin remains only within the focus zone ZF. It is then chemically functionalized to fix the nano-component 4. A multitude of nano-components is then dispersed on the integrated optical circuit, then exposed to a gas flow so that only a single nano-component remains on the integrated optical circuit, which is fixed in the focus zone ZF. Alternatively, the multitude of nano-components can be dispersed in the lithographic resin that is deposited on the integrated optical circuit, and the development of the resin is carried out to permanently leave only a resin pad at the location of the focus zone ZC, which contains a single nano-component.
[0035] The nano-component 4 may be a nanocrystal which has an optically active site for the nominal wavelength value in vacuum, commonly called a colored center. It may be a nanodiamond, for example. It may have any shape, in particular substantially spherical with a diameter which is between 1 nm and 100 nm. When it absorbs a photon coming from light which is brought by the waveguide 2 then transmitted by the nano-antenna 3, the nano-component 4 is a photonic nano-sensor. Conversely, when it produces a photon which is transmitted to the waveguide 2 by nano-antenna 3, nano-component 4 is a photonic nano-emitter.
[0036] According to the invention, the integrated optical device further comprises a reflector 5 which is arranged above the waveguide 2, also in front of the tip P3 of the nanoantenna 3 but at a greater distance from this tip P3 than the nano-component 4. For example, the distance between the reflector 5 and the tip P3 may be approximately 100 nm when that between the tip P3 and the nano-component 4 is approximately 50 nm. The reflector 5 may be constituted by another portion of the layer of material used to constitute the nano-antenna 3. Thus, the reflector 5 may also be constituted by a portion of an aluminum layer with a thickness of 30 nm. In the embodiment shown in [Fig.l], the reflector 5 which is thus constituted has a peripheral limit, parallel to the surface S, which is also an isosceles triangle whose axis of symmetry is parallel to the longitudinal direction D2.It is centered transversely with respect to the waveguide 2, but its tip at the apex, designated by P5, is oriented towards the tip P3 of the nano-antenna 3. In other words, the tips P3 and P5 are directed towards each other, on either side of the focal zone ZF. The axis D35 which is indicated in the figure is parallel to the longitudinal direction D2 passing through the tips P3 and P5. The plane which contains this axis D35 and which is perpendicular to the surface S of the substrate 10 is then a plane of symmetry for the assembly constituted by the nano-antenna 3, the nanocomponent 4 and the reflector 5.
[0037] The reflector 5 is dimensioned to perform a function of reflecting the electromagnetic field that is produced by the nano-antenna 3 from its tip P3 when the light is brought by the waveguide 2. The concentration of the electric field in the focal zone ZF, which results from the combined effects of the nano-antenna 3 and the reflector 5, has a higher efficiency than that of the concentration that is produced by the nano-antenna 3 alone. The dimensions of the reflector 5, in particular its apex angle value, at the tip P5, and the length of its oblique isosceles triangle sides, can be optimized using numerical simulations to maximize its reflection efficiency. Such numerical simulations can result in an isosceles triangle size for the reflector 5 that is smaller than that of the nano-antenna 3.
[0038] Furthermore, it may be advantageous to simultaneously reduce the optical coupling that could exist between the waveguide 2 and the reflector 5, so that this reflector 5 has an optical function (reflector function) that is quite distinct from that of the nanoantenna 3 (function of sampling light power from the waveguide 2). For this, the reflector 5 may not be provided with any portion of coupling layer that is similar to the portion 23, between this reflector 5 and the waveguide 2. Optionally, a portion of layer may be interposed between the waveguide 2 and the re reflector 5, the material and thickness of which are optimized to reduce their optical coupling. Generally, the device of the invention produces a degeneracy lift between the two directions of propagation of the light inside the waveguide 2, parallel to its longitudinal direction D2. For the operation of the device as a light detector, a detection sensitivity which is higher is obtained when the light is injected into the waveguide 2 in a direction of propagation which goes from the side of the nano-antenna 3 towards the side of the reflector 5, as indicated by the arrow F in the figures. Part of the power of this light is transferred to the nano-antenna 3, in the form of excitation of plasmonic oscillation mode(s) of this nano-antenna, this(these) excited mode(s) producing an electric field which is concentrated in the focal zone ZF, varying at the optical frequency of the injected light.This concentration of the electric field is reinforced, thanks to the invention, by other plasmonic oscillation modes which are excited in the reflector 5 by the electric field through the focus zone ZF. The nano-antenna 3 and the reflector 5 therefore act in synergy to increase the concentration efficiency of the electric field in the focus zone ZF, consequently increasing the probability of absorption by the nano-component 4 of a photon which corresponds to this electric field. For the operation of the device as a single photon source, the nano-antenna 3 and the reflector 5 act in synergy so that a photon which is emitted by the nano-component 4 is transmitted with a higher transfer efficiency to the waveguide 2, in order to propagate inside the latter in a direction going from the side of the reflector 5 towards the side of the nano-antenna 3, that is to say in the direction which is opposite to that of the arrow F. .
[0039] In fact, the nano-antenna 3 and the reflector 5 constitute a unidirectional resonant cavity, parallel to the axis D3 5, for electromagnetic radiation which has the aforementioned nominal wavelength value in a vacuum. In a known manner, this resonant cavity increases the spontaneous emission of photons by the nanocomponent 4 by a factor which is called the Purcell factor and commonly noted FP, and which is greater than unity. The theoretical expression of this Purcell factor for a one-dimensional resonant cavity is well known to those skilled in the art. The value of this Purcell factor depends in particular on the optical coupling which is effective between the nano-antenna 3 and the waveguide 2, and on the level of optical isolation which is effective between the reflector 5 and the waveguide 2.
[0040] In the embodiment of [Fig.l], the waveguide 2 provides the optical connection of the device of the invention with the exterior. In particular, for operation as a light detector, the light to be detected is injected into the waveguide 2. For operation as a single photon source, each photon that is produced by the nanocomponent 4 is transmitted to the exterior of the device by the waveguide 2.
[0041] [Fig.2] shows another embodiment of the invention which uses a different technology for manufacturing the integrated optical circuit. The substrate 10 is now made of lithium niobate (LiNbO3). In a known manner, it is then possible to create a waveguide within the substrate 10 by ion implantation or ion exchange through the surface S, to substitute lithium cations with hydrogen cations. In this way, a buried waveguide 1 is created within the substrate 10, being parallel to the longitudinal direction Db. The waveguide 1 is adapted to also guide light which has the same nominal wavelength value as that of the waveguide 2. The substrate 10 can be covered on its surface S by a layer 12 whose refractive index value is close to that of the substrate 10 outside the waveguide 1. This layer 12 can be made of silica.The assembly which is constituted by the waveguide 2, the nano-antenna 3, the optional coupling layer portion 23, the nano-component 4 and the reflector 5 can then be produced on the layer 12, with an arrangement, materials and dimensions similar to those which have been described and cited for the embodiment of [Fig.l]. The waveguides 1 and 2 are then superimposed perpendicular to the surface S of the substrate 10, and the directions Di and D2, as well as the axis D3 5, are parallel. The layer 12 then produces an optical coupling between the waveguides 1 and 2, of the evanescent field coupling type. The intensity of this coupling is adjusted by means of the thickness which is selected for the layer 12. For example, the layer 12 can have a thickness which is substantially between 50 nm and 2 pm (micrometer) when it is a silica layer.Then, for the light detector operating mode, the light is injected into the waveguide 1 in accordance with the direction of propagation which is indicated by the arrow F in [Fig.2], then transferred to the waveguide 2 through the layer 12, and part of its power is then transferred by the nano-antenna 3 into the focal zone FC where a photon of this light is absorbed by the nano-component 4 forming a photonic nano-sensor. The waveguide 1 is then called the primary waveguide and the waveguide 2 called the intermediate waveguide. Advantageously, the intermediate waveguide 2 may have a length L of extension upstream of the nano-antenna 3 relative to the direction of the arrow F, which is selected so that the edge Bo of the nano-antenna 3 is located substantially at the level of a maximum power of the light inside the intermediate waveguide 2.Indeed, in accordance with the well-known principle of operation of optical couplers by evanescent fields, the optical power of the light which is injected into the primary waveguide 1 is transferred periodically from this primary waveguide 1 to the intermediate waveguide 2, then in the opposite direction from this intermediate waveguide 2 to the primary waveguide 1, periodically in the longitudinal direction Di (or D2). Thus, the length L is preferably selected to be substantially equal to half the spatial period of the bottom. cularly the light power between the two waveguides 1 and 2. The intermediate waveguide 2 then produces a confinement of the light at the edge B o of the nano-antenna 3, and thus contributes to further increasing the detection sensitivity of the device. An even higher confinement is produced by the intermediate waveguide 2 at the edge B o of the nano-antenna 3 when the material of the intermediate waveguide 2 has a refractive index value which is significantly higher than that of the substrate 10 inside the primary waveguide 1.
[0042] When the device of [Fig.2] is used as a single photon source, the photon is emitted by the nano-component 4, transmitted to the intermediate waveguide 2 by the nano-antenna 3 while propagating in the intermediate waveguide 2 in the opposite direction to that of the arrow F, then retransmitted through the layer 12 to the primary waveguide 1 while propagating in the latter again in the opposite direction to that of the arrow F.
[0043] [Fig.3a]-[Fig.3c] show several possible variants for the shape of the reflector 5, which are compatible with the invention.
[0044] The arrangement shown in [Fig.3a] corresponds to that presented previously with reference to [Fig.l] and [Fig.2], for which the reflector 5 has an isosceles triangle shape whose tip P5 is directed towards the focal zone ZF. In this figure, the edges of the isosceles triangle of the reflector 5 are designated by Bo', Bf and B2', Bo' being its base edge, and Bi' and B2' being its oblique edges which converge at the tip P5. A radius of curvature of the reflector 5 at its tip P5, in a plane which is parallel to the surface S, may be less than 20 nm, preferably between 5 nm and 20 nm. The nano-antenna 3 and the nano-component 4 are arranged with this reflector 5 as described above.
[0045] In the variant shown in [Fig.3b], the nano-antenna 3 is the same as previously, but the reflector 5 is now constituted by a portion of metal layer which has an edge with a concave shape C facing towards the focus zone ZF. Such a reflector 5 can still be constituted from the same metal layer as that of the nano-antenna 3, but it can now be as wide as the waveguide 2, in the transverse direction which is parallel to the surface S and perpendicular to the axis D3 5. In a plane which is parallel to the surface S, the concave-shaped edge C can be an arc of a circle whose center of the circle is substantially superimposed on the focus zone ZF.
[0046] Finally, in the variant shown in [Fig.3c], the nano-antenna 3 is still the same, but the reflector 5 is now of the Bragg reflector type. For this, it can be constituted by a succession of several separate segments 5i, 52, 53 and 54 of the same layer which is located above the waveguide 2. The widths of the segments 5r54 as well as the widths of the separation intervals between them, measured parallel to the axis D3 5, are selected to produce a Bragg reflection effect for the electromagnetic radiation which is re-emitted by the nanoantenna 3 through the focal zone ZF. Advantageously, the segments 5r54 which thus constitute the reflector 5 may be curved in the plane which is parallel to the surface S, with respective centers of curvature which are all substantially superimposed on the focal zone ZF of the nanoantenna 3. Possibly, the number of segments which constitute the Bragg reflector 5 may be other than four, for example equal to three or five. The segments 5r54 may be made from the same layer of metal, for example aluminum, with a layer thickness which is substantially equal to 30 nm.
[0047] [Fig.4] illustrates yet another alternative embodiment of the invention, in which the nano-antenna 3 has a structure different from that described so far. This new nano-antenna structure can be combined with the embodiments of [Fig.l] and [Fig.2] concerning the nature and constitution of the substrate and the way of injecting light into the waveguide 2 or transmitting a photon which is produced by the device in its operating mode as a single photon source. It can also be combined with the embodiments of the reflector 5 illustrated by [Fig.3a]-[Fig.3c]. According to this new nano-antenna structure, the nano-antenna 3 comprises a plurality of disjointed metal segments which are offset between the base part Bo of this nano-antenna and the focus zone ZF.Such a structure makes it possible to produce the electric field concentration function resulting from the light that has reached the base part Bo of the nano-antenna having been guided by the waveguide 2, while limiting the losses that could occur in the nano-antenna, in particular by the Joule effect. Thus, the nano-antenna 3 which has this new structure still effectively couples the waveguide 2 to the nano-component 4. In the example shown in [Fig. 4], the nano-antenna 3 is composed of five segments 3b 32, 33, 34 and 35 which are aligned along the axis D3 5 and centered transversely with respect to this axis. The segment 3i constitutes the base part Bo of the nano-antenna, and the segment 35 constitutes the tip P3. The segments 3r35 may have transverse extensions, perpendicular to the longitudinal direction D2, which decrease from the base part Bo towards the focal zone ZF.Finally, generally for such a constitution of the nano-antenna 3 by disjointed metallic segments, all these segments can be respective portions of the same metallic layer, for example of aluminum 30 nm thick.
[0048] It is understood that the invention can be reproduced by modifying secondary aspects of the embodiments which have been described in detail above, while retaining at least some of the advantages cited. In particular, the nano-antenna and the reflector can have different shapes and constitutions from those which have been described, while retaining their respective functions. Finally, all numerical values and materials cited have been for illustration purposes only, and may be changed depending on different applications for which the device is intended.
Claims
Claims
1. A nano-component integrated optical device, comprising: - an integrated optical circuit substrate (10), supporting a waveguide (2) adapted to guide light which has a wavelength between 350 nm and 2000 nm when said light propagates in a vacuum; - a metallic nano-antenna (3), which is supported by the substrate (10), with a base part (Bo) of the nano-antenna which is optically coupled to the waveguide (2), and said nano-antenna being adapted to concentrate in a focal zone (ZF) an electric field resulting from the light which has reached the base part of said nano-antenna by being guided by the waveguide (2);and - an optical component, called nano-component (4), which has at least one dimension between 1 nm and 100 nm and which is rigidly connected to the substrate (10), said nano-component being located against or in the focal zone (ZF) of the nano-antenna (3) and capable of absorbing a photon of light which has the wavelength in vacuum between 350 nm and 2000 nm; the device being characterized in that it further comprises: - a reflector (5), which is rigidly connected to the substrate (10) and located on one side of the nano-component (4) opposite the nano-antenna (3), so as to reinforce an efficiency of concentration of the electric field in the focal zone (ZF), compared to a reference concentration which would be produced by the nano-antenna in the device in the absence of the reflector, for the light of wavelength in vacuum between 350 nm and 2000 nm which reaches the base part (Bo) of the nano-antenna by being guided by the waveguide.;
2. Device according to claim 1, wherein the nano-antenna (3), the nano-component (4) and the reflector (5) are aligned parallel to a longitudinal direction (D2) of the waveguide (2).
3. Device according to claim 2, wherein the nano-antenna (3), the nano-component (4) and the reflector (5) form an arrangement which is symmetrical with respect to a plane which is parallel to the longitudinal direction (D2) of the waveguide (2) and perpendicular to a surface (S) of the integrated optical circuit substrate (10), said surface supporting said waveguide.
4. Device according to one of the preceding claims, in which the re- deflector (5) is metallic.
5. A device according to claim 4, wherein the reflector (5) is based on aluminum, gold or silver, or based on an alloy which comprises aluminum, gold or silver.
6. A device according to claim 4 or 5, wherein the nano-antenna (3) and the reflector (5) are two portions of a metal layer which is supported by the substrate (10), the two portions of the metal layer being located on one side of the waveguide (2) which is opposite the substrate.
7. Device according to claim 6, wherein a thickness of the metal layer is between 10 nm and 50 nm, preferably between 25 nm and 35 nm.
8. Device according to one of the preceding claims, in which the reflector (5) has a boundary oriented towards the nano-antenna (3), said boundary having one of the following shapes: - a tip shape (P5) directed towards the focus zone (ZF), with a radius of curvature less than 500 nm, preferably between 5 nm and 500 nm, at said tip; and - a concave shape (C) facing towards the focus zone (ZF), or in which the reflector (5) is of the Bragg reflector type.
9. Device according to one of the preceding claims, further comprising a coupling layer portion (23) which is intermediate between the waveguide (2) and the nano-antenna (3), said coupling layer portion being adapted to increase a light power transfer between said waveguide and said nano-antenna compared to a reference transfer which would exist in the device between said waveguide and said nano-antenna in the absence of a coupling layer portion, for light which has the wavelength in vacuum between 350 nm and 2000 nm when said light is brought by the waveguide to the base part (Bo) of the nano-antenna.
10. Device according to one of the preceding claims, wherein the waveguide (2) to which the nano-antenna (3) is coupled is called an intermediate waveguide, and the device further comprises a primary waveguide (1) which is also adapted to guide light having the wavelength in vacuum between 350 nm and 2000 nm, the intermediate waveguide and the primary waveguide having light guiding directions which are parallel and being optically coupled to each other, so that said light, by being injected into the primary waveguide, is at least partially transferred to the intermediate waveguide, then brought by said intermediate waveguide to the base part (Bo) of the nano-antenna.
11. Device according to claim 10, wherein the primary waveguide (1) and the intermediate waveguide (2) are superimposed in a direction which is perpendicular to a surface (S) of the substrate (10), and the device further comprises a coupling layer (12) between said primary waveguide and said intermediate waveguide, and which is adapted to produce evanescent field coupling between said primary waveguide and said intermediate waveguide.
12. Device according to one of the preceding claims, wherein the nano-component (4) is a photonic nano-sensor which is adapted to absorb a photon of light with a wavelength in vacuum between 350 nm and 2000 nm when said light is brought by the waveguide (2) to the base part (Bo) of the nano-antenna (3), or wherein the nano-component (4) is a photonic nano-emitter which is adapted to produce a photon having a wavelength in vacuum between 350 nm and 2000 nm, and also included in a transmission spectral band of the waveguide (2).
13. Device according to one of the preceding claims, wherein the nano-antenna (3) comprises a plurality of disjointed metal segments (3r35) which are offset between the base part (Bo) of said nano-antenna and the focus zone (ZF).