WO2012052628A2

WO2012052628A2 - Surface-plasmon-assisted photon detection device, and method for producing the device

Info

Publication number: WO2012052628A2
Application number: PCT/FR2011/000557
Authority: WO
Inventors: Cécile DELACOUR
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2010-10-20
Filing date: 2011-10-17
Publication date: 2012-04-26
Also published as: FR2966643A1; WO2012052628A3

Abstract

The invention relates to an optical detector, comprising a photon detection element (2) including a superconducting track (4) and a wave guide (1) arranged so as to be coupled to the surface-plasmon detection element (2) at a coupling area. The wave guide (1) is supported at a distance from the detection element (2). The detection element (2) comprises, at the coupling area, an electrically conductive layer (5) electrically contacting the superconducting track.

Description

Surface-plasmon-assisted photon detection device and method of producing the device

Technical field of the invention

The invention relates to a photon detection device comprising:

a photon detection element comprising a superconducting track,

a waveguide arranged to be coupled to the surface plasmon detection element at a coupling zone, said waveguide being kept at a distance from the detection element.

State of the art

In telecommunications technologies (cryptography), medical imaging, astronomy, photon detection devices are being used more and more. The miniaturization of these detection devices by the use of microelectronics and nanotechnologies makes it possible to detect the light more finely, or even to detect a single photon with increased sensitivity. FR2886762 discloses an ultrasensitive optical detector. As illustrated in FIG. 1, an optical photon detector comprises a silicon waveguide 1 coupled to a detection element 2 formed by a superconducting material track, for example NbN. The absorption of the photon by the sensing element 2 disturbs the electronic transport in the sensing element so that the absorption of a photon is detectable by a voltage or current measurement at connection terminals 3a, 3b of the detection element 2. For a superconducting material, the absorption of a photon generates a hot spot creating a local resistive barrier on a section of the track in superconducting material. It is then possible to determine whether a resistive barrier has been created by performing, for example, measurements on the two connection terminals 3a, 3b disposed at the ends of the superconducting material track. Such a detection device is characterized by a dead time corresponding to the relaxation of the detection element. The dead time is actually a time interval during which the superconducting track becomes metallic following the absorption of a photon. During this timeout, new photons coming to be coupled to the detection element can not be counted. The speed of this detection device is therefore affected by the time required for relaxation of the superconducting track.

Object of the invention

The object of the invention is to provide a photon detection device based on a detection element comprising a superconducting track whose relaxation time and efficiency are optimized. This object is particularly achieved by the appended claims and more particularly in that at the level of the coupling zone, the detection element comprises an electrically conductive layer in electrical contact with the superconducting track. The invention also relates to a method for producing a photon detection device comprising, on a substrate, the following steps: - to form a waveguide,

forming, at a distance from the waveguide, a detection element comprising an electrically conductive layer in electrical contact with a superconducting track at a coupling zone of the detection element with the waveguide

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention given as non-restrictive examples and represented in the accompanying drawings, in which: FIG. photon detection device according to the prior art.

Figures 2 and 3 illustrate a first embodiment of a photon detection device according to the invention seen respectively in three dimensions and on the side.

Figures 4 and 5 illustrate a second embodiment of a photon detection device according to the invention seen respectively in three dimensions and on the side.

Figure 6 illustrates an embodiment using a resonant cavity. FIG. 7 illustrates, seen from above, an embodiment with a detection element in the form of a U.

FIG. 8 illustrates, seen from above, an embodiment with a detection element in the form of a coil.

Figures 9 to 13 illustrate different steps of producing an optical detector. Description of preferred embodiments

The photon detection device described below differs from the devices of the prior art in that it comprises an additional layer of electrically conductive material making it possible to accelerate the relaxation of the superconducting track, and to increase the efficiency of the detection.

In a suitable configuration, when a light wave propagates in a waveguide, it can couple to the electrons of a nearby metal. A wave then propagates at the interface between an electrically conductive layer and a surrounding dielectric, it is a surface plasmon. The light can thus be confined by the detection element and its probability of being absorbed is important. Thus, the embodiments described hereinafter also make it possible to increase the efficiency of the detector because the power density and the time of passage of the light are increased at the level of the detection element thanks to the additional layer.

As illustrated in FIGS. 2 to 8, the photon detection device comprises a waveguide 1, for example formed by a guide made of silicon, or glass, which may be in the form of a ribbon. Such a waveguide 1 may be a type III or IV material, or an alloy of these types of materials such as InP, GaS, InGaS. Advantageously, the waveguide 1 is transparent to the wave considered. A wave considered is the electromagnetic or optical wave propagating in the waveguide 1. The detection range of the device is preferably between the visible and the near infrared. In general, the waveguide 1 may be a partially engraved (guide stops) or totally etched (photonic crystals) and / or locally structured planar guide for containing, for example, networks for the coupling of the waveguide 1 an optical fiber (not shown) upstream of the detection element 2 according to the direction of movement of the wave considered. In FIGS. 2 to 8, the meaning of displacement of the wave considered is indicated by the arrows F1 and F2, this direction of movement of the wave may be substantially parallel to the longitudinal axis A1 of the waveguide 1. The optical fiber, or another light source , may be coupled to the waveguide 1, upstream of the detection element 2 by a tap (coupling on the wafer) or networks (quasi-vertical coupling) structured on the waveguide 1. Preferably, the structure for coupling an optical fiber, or other light source, to the waveguide 1 will be placed at least 1 mm upstream of the detection element 2, in a direction defined along the longitudinal axis A1 of the waveguide 1 and in the direction of movement of the wave considered, so that only the light from the waveguide 1 can be coupled to the detection element 2.

The detection device further comprises a photon detection element 2 comprising a superconducting track 4. This detection element can just as well detect a single photon as a plurality of photons. By superconducting track 4 is meant a track of superconducting material such as, for example, Nb, NbN. Preferably, to obtain a better coupling, the detection element 2 comprises a longitudinal axis A2 parallel to the longitudinal axis A1 of the waveguide 1, and situated in a plane perpendicular to the plane of the waveguide 1, said perpendicular plane passing, preferably, by the median of the waveguide 1, said median being parallel to the longitudinal axis A1 of the waveguide 1, the waveguide 1 is intended to guide a photon and transmit it to the detection element 2. This transmission is performed by optical coupling of the waveguide 1 with the detection element 2 by plasmon surface at a coupling zone. The waveguide 1 is then maintained at an appropriate distance from the detection element 2 to allow the evanescent fields of the waveguide 1 and the detection element 2 to interact so as to couple the wave in question. The waveguide 1 will see therefore a photonic mode and the detection element 2 will see a plasmonic mode.

In other words, the detection element 2 and the waveguide 1 are not in direct contact, and are separated by an interval of preferably between 10 nm and 500 nm at the coupling zone. In general, the maximum distance of the interval may be the value of the wavelength considered. In fact, when a wave propagates in a waveguide 1, a part of this wave penetrates into the surrounding medium, it is the so-called evanescent part of the wave. This length of penetration is proportional to the ratio of refractive index of the guide and its surrounding environment. Thanks to the coupling of the waveguide 1 with the detection element 2, the evanescent field of the waveguide 1 can be progressively accumulated by the detection element 2 when the latter two are close to each other . This process is also reciprocal.

An index can be defined as the ratio of the wavelength in the vacuum to the wavelength in the medium to be crossed.

By coupling zone is meant a partial overlap area of the waveguide 1 by the detection element 2 at which optical coupling is performed. In other words, at the level of the coupling zone, the waveguide 1 is opposite the detection element 2. In FIGS. 3 and 5, the partial overlap zone is formed over a distance Lr of overlap oriented according to FIG. longitudinal axis A1 of the waveguide 1.

In order to improve the relaxation time of the detection element 2 and to promote the coupling, the latter comprises an electrically conductive layer 5 in electrical contact with the superconducting track 4 of the coupling zone, preferably at least over the entire coupling zone. Typically, this electrically conductive layer is a metal layer, for example copper or noble metal (Au, Pt). More generally, a superconductor, here track 4, comprises a superconducting state and a metallic state, the electric electrical resistivity of the electrically conductive layer 5 will preferably be less than the resistivity of the superconducting track 4 in its metallic state . The thickness of the electrically conductive layer 5 is preferably between 10 and 200 nm. This thickness is chosen so that the effective index of the plasmonic mode propagating in the detection element 2 is substantially equal to the effective index of the photonic mode propagating in the waveguide 1. This makes it possible to optimize the power transfer from the waveguide 1 to the detection element 2. A mode corresponds to a spatial configuration of the electromagnetic field induced by the propagation of an electromagnetic or optical wave in the detection element 2. According to the distribution of the electromagnetic field, a given mode sees a different index of the materials constituting the guide, and the index seen by each mode defines an effective index. An effective index can be defined as the ratio of the wavelength in vacuum to the wavelength of the mode in the medium to be crossed.

Thus, the sensing element 2 may be formed by a bilayer comprising the electrically conductive layer 5 in electrical contact with the superconducting track 4. This assembly forming the detection element 2 can then have a total thickness at the coupling zone of between 11 nm and 210 nm. The track 4 can be defined by a thickness, in a direction d1 perpendicular to the plane of the track 4, and by a width in a direction d2 perpendicular to the longitudinal axis A2 of the track 4 and the direction d1. The thickness of the superconducting material forming the track 4 is preferably sufficiently low, for example between 1 nm and 10nm, so that a resistive barrier can be formed over the entire thickness of the track 4. The track 4 has, preferably, a constant section to maintain a homogeneous critical current. Track 4 is also, preferably, large enough to have a good probability of capturing a photon, and not too wide so that a resistive barrier can form over its entire width when a photon is absorbed. The width of the superconducting track 4 can be between 10 nm and 250 nm, this width of course depends on the energy of the incident photons and the thickness of the track 4. In a configuration where the width of the superconducting track 4 is equal at the width of the electrically conductive layer 5, the overall width of the detection element 2 can also be optimized to improve the coupling to the waveguide 1. Thus, it is preferable to choose a width allowing the effective index of the guide wave 1 to equal the effective index of the detection element 2.

In operation of the device, the superconducting track 4 of the detection element 2 is biased in current at a current below a critical current for a temperature below the critical temperature of the superconducting material (temperature and current below which the material is superconducting ). By critical current is meant the current below which the track 4 of the detection element 2 is superconducting, that is to say having a zero resistance, and above which the track 4 becomes of metallic type. Preferably, the bias current will be substantially equal to 0.9 times the critical current. Thus, when a photon is absorbed by the detection element 2, it is possible to measure a voltage peak at the connection terminals of the detection element 2. This peak then corresponds to the effective detection of a photon by generating a hot spot and a resistive barrier in the superconducting track 4 at the coupling area. In Figures 2 and 4, the connection terminals 3a, 3b are in electrical contact with the superconducting track 4 at its ends. The track 4 may comprise a rectilinear central part with a longitudinal axis A2 substantially parallel to the longitudinal axis A1 of the waveguide 1. This central part is preferably placed vertically above the median of the waveguide 1 along its longitudinal axis A1. Perpendicularly at the two ends of this central part, and in the plane of said track 4, may extend two lugs of the track 4 connected to the connection terminals 3a, 3b. Of course, this is only an exemplary embodiment, the skilled person can realize other variants for measuring a voltage peak at the superconducting track 4.

The electrically conductive layer 5 makes it possible to significantly reduce the dead time of the detector. Indeed, after absorption of the photon by the detection element 2, the resistivity of the electrically conductive layer 5 will be lower than the resistive barrier generated in the superconducting track 4. Thus, since the electrically conductive layer and the superconducting track 4 are in electrical contact, the current will be deflected in the electrically conductive layer according to the principle of paralleling resistances so as to accelerate the relaxation process of the superconducting track 4. the detection element 2.

According to a first embodiment illustrated in Figures 2 and 3, the superconducting track 4 is disposed between the electrically conductive layer 5 and the waveguide 1. In the case where the thickness of the superconducting track 4 remains low (less than 10nm, and typically between 3nm and 4nm) in front of that of the electrically conductive layer (greater than 10nm), the probability of detection of a photon during the passage of the wave of the waveguide 1 towards the detection element 2 is then less than 10%. However, effective optical coupling is achieved between the layer 5 and the waveguide 1, this optical coupling increases the concentration of the optical power along runway 4, increasing the probability of detection after coupling. In other words, at the partial overlap zone of the waveguide 1 by the detection element 2, the waveguide is optically coupled with the electrically conductive layer, and then, after coupling, the wave is confined in this region. last, and the detection of a photon can take place at areas in contact with said layer 5 and the track 4 (typically the entire length of the track 4). In addition to improving the detection probabilities, the electrically conductive layer 5 makes it possible to reduce the heating of the Joule-induced track 4 during the absorption of the photon. Preferably, a coupling zone is considered between the waveguide 1 and the detection element 2 (preferably an optical coupling between the electrically conductive layer and the waveguide) and a detection zone represented by the contact. between the track 4 and the electrically conductive layer 5, the detection zone may have dimensions greater than those of the coupling zone.

According to a second embodiment illustrated in FIGS. 4 and 5, the electrically conductive layer 5 is disposed between the track 4 and the waveguide 1 so as to allow optical coupling of the waveguide 1 with the electrically conductive layer 5. of the detection element 2 in the coupling zone, this optical coupling increases the concentration of the optical power along the track 4, thereby increasing the probability of detection. This embodiment results in better photon detection. The quantum efficiency of a photon detector characterizes its ability to detect a photon or not. Therefore, the more efficient the coupling, the more likely a photon has to be detected. Thus, in this particular embodiment the probability of detection of a photon is improved because the interaction surface at the superconducting track 4 is increased by the electrically conductive layer. In other words, the addition of an electrically conductive layer 5 in electrical contact W

11

with the track 4 at the coupling zone, promotes the confinement of the electromagnetic wave at said electrically conductive layer. The concentration of the optical power along the track 4 is then about a hundred times greater compared to the prior art where the track 4 is directly opposite the waveguide 1 at the coupling zone, or relative to in the first embodiment in the case where the thickness of the track 4 is greater than 10 nm, this results in a better sensitivity when detecting a photon. In addition, as in the first embodiment, the electrically conductive layer 5 placed in contact with the track 4 makes it possible to reduce joule-induced heating of the latter during the absorption of the photon, thus promoting its relaxation. As mentioned in the first embodiment, a difference can be made between the coupling zone and the detection zone.

Preferably, the waveguide 1 and the electrically conductive layer 5 are kept at a distance from one another by a dielectric material, for example silicon oxide, which makes it possible to limit reflection, diffusion or absorption of the wave considered. This dielectric material is preferably transparent to the wavelength considered. In general, the waveguide 1 has a higher index, typically between 2 and 4, than the dielectric material, of index typically between 1 and 1.7, so as to confine the wave considered in the guide. 1 and to limit its evanescence in the dielectric material.

The detection element 2 can partially cover the waveguide 1 at the coupling zone, the partial overlap length Lr of the waveguide 1 by the detection element 2 is an odd integer multiple (2n + 1, with n positive integer) of an effective coupling length between the waveguide 1 and the detection element 2. In FIGS. 3 and 5, the overlap length Lr is oriented along the longitudinal axis A1 of the waveguide 1. The coupling length Le corresponds to a characteristic distance representative of the power fraction transmitted from the waveguide 1 to the detection element 2. In fact, it corresponds to the minimum distance for which the maximum power is transferred from the waveguide 1 to the detection element 2, preferably to the electrically conductive layer. The effective coupling length therefore depends on the effective indices of the eigen modes propagating in the waveguide 1 and in the detection element 2, and effective indices of the supermodes resulting from the coupling between these two eigenmodes in the composite superstructure. of the waveguide 1 and the detection element 2. By eigenmode is meant the mode propagating in a single guide. The effective indices of each of the eigenmodes depend on the geometry of the waveguide 1 and the detection element 2 while the effective indices of the supermodes depend in addition on the distance separating the waveguide 1 from the element for detection (2), see in this sense the publication in "Fundamentals of Optical Waveguides" K. Okamoto 2006, Elsevier pages 159 to 166.

The effective index of the modes supported by the waveguide 1 and the detection element can be calculated numerically by a mode solver, in which case the index also depends on the geometry of the guide and not only on the properties of the material. . Thus, in order to optimize the coupling, the geometries of the waveguide 1 and of the detection element 2 will be fixed for a given wave so that the ratio of their effective indices tends towards 1.

After fixing the geometry of the waveguide 1 and the detection element 2, the distance separating the waveguide 1 from the detection element 2 at the level of the coupling zone is also optimized as a function of the wave considered. This separation interval influences the coupling length and the power fraction thus transmitted on the compactness and efficiency of the detection device. The appropriate separation distance can be calculated by numerical computations in FDTD, for example by using software of the RSÔFT © type. In general, the difference in the effective indices of supermodes is maximal for a small spacing, and the greater the difference of the indices, the more the coupling is optimal. By optimal, it is considered that the coupling length Le is weak and a large power fraction is coupled. In fact, it is preferable to avoid reflection at the level of the electrically conductive layer 5.

The detection element 2 can also form a resonant cavity, for example of the Fabry-Perrot type, arranged to trap an incident photon that would not have been absorbed by the track 4 during its first passage through the detection element.

In a first example of a resonant cavity embodiment illustrated in FIG. 6, the waveguide 1 is interrupted while the detection element 2, preferably still in the form of a bilayer (track 4 / layer 5), continued. In other words, the partial overlap length Lr of the detection element with respect to the waveguide 1, at the level of the coupling zone, is equal to an odd multiple of the effective coupling length Le between the guide of wave 1 and the detection element 2, while the total length Ltot of the detection element 2 is equal to the recovery length plus one

To _.

cavity length Lcav equal to * ", with A the incident wavelength

(ie from the source), and the effective index of the mode propagating in the detection element 2. The cavity length Lcav is defined by a length, in the extension of the recovery length Lr , where no overlap between the detection element 2 and the waveguide 1 is achieved.

In a second exemplary embodiment of the resonant cavity, the detection element 2 may be opposite the waveguide 1 over its entire length. Therefore, it is possible to structure the waveguide 1 by at least one mirror, for example Bragg, located downstream of the detection element 2 according to the direction of the wave considered in the waveguide 1. This mirror makes it possible to reflect an unabsorbed photon of the wave considered and to send it back to the detection element 2. The use of such a mirror enables then at least a second passage of the photon in the detection element 2, increasing its probability of being absorbed and detected.

The photon detection device, according to its embodiment, may be polarization sensitive. Indeed, the modes using a detection element 2 of substantially rectilinear shape at the level of the coupling zone (FIGS. 2 to 5) are sensitive to the TM polarization. In fact, when an electromagnetic wave, also called in this optical wave area (for a range of wavelength included from visible to near and mid-infrared), propagates along a longitudinal axis A1 of the waveguide 1, this wave breaks down into two states of polarization. A first state forms a transverse electric component (TE "Transverse Electric" in English) and a second state forms a transverse magnetic component (TM for "Transverse Magnetic" in English). The TM component comprises an electric field perpendicular to the plane of the waveguide 1 and a magnetic field parallel to the plane of the guide. The TE component comprises a magnetic field perpendicular to the plane of the waveguide 1 and an electric field parallel to the plane of the waveguide 1.

According to an embodiment illustrated in FIG. 7, the detection element 2 has the shape of a U formed in a plane substantially parallel to the plane of the waveguide 1. Thus, the detection element may comprise at least two branches 2a, 2b, preferably with a longitudinal axis parallel to the longitudinal axis A1 of the waveguide 1, partially covering the waveguide 1. The two branches 2a, 2b are interconnected at one of their ends proximal by a connecting element 2c forming the base of the U. At the branches 2a, 2b and the connecting element, the track 4 is in contact with the layer 5. Preferably, the distance separating the two branches 2a, 2b of U, also called slit, is constant, for example between 10 nm to 200 nm and typically set at 50 nm. The distance between the two branches can be adjusted for a thickness of the electrically conductive layer 5 so that the effective eigenmode indices propagating in the waveguide 1 and the electrically conductive layer 5 are substantially equal. Preferably, the slot is located in a plane perpendicular to the plane of the waveguide 1 and passing through the median of the waveguide 1, said median being parallel to the longitudinal axis A1 of the waveguide 1. On the 7, the base of the U defined by the connecting element 2c is proximal to the output of the waveguide 1 arrow F2) to allow a more efficient coupling and limit the reflection during the coupling.

This embodiment using a U-shaped detecting element as in Fig. 7 is sensitive to TE polarization.

According to a variant of the polarization-sensitive mode TE illustrated in FIG. 8, the detection element 2 may take the form of a line of slots, in other words a coil, said line being of axis A3 perpendicular to the axis longitudinal A1 of the waveguide 1 and located in the plane of the detection element 2. In the particular example illustrated in Figure 8, the detection element 2 can be subdivided into a plurality of branches 2a, 2b each having a longitudinal axis substantially parallel to the longitudinal axis A1 of the waveguide 1. The branches 2a, 2b are alternately connected by a connecting element 2c at first ends of a first and a second adjacent branch, then at second ends of the second and third branches, adjacent, so as to form a slot between two adjacent branches 2a, 2b. At the branches 2a, 2b and the connecting elements 2c, the element 2 comprises a track 4 / layer 5 bilayer. As previously specified for the U-shaped mode, the width of the slot is adjusted for a thickness of the electrically conductive layer 5 fixed so that the effective indices modes propagating in the waveguide 1 and the electrically conductive layer 5 are substantially equal. The connecting elements 2c are of longitudinal axis substantially perpendicular to the longitudinal axis of the branches 2a, 2b. The width of these connecting elements 2c may be greater than the width of the branches 2a, 2b. The superconducting track 4 of the detection element 2 is connected at its respective ends to connection terminals (not shown). Preferably, one of the slots is located in a plane perpendicular to the plane of the waveguide 1 and passing through the median of the waveguide 1, said median being parallel to the longitudinal axis A1 of the waveguide 1, 1 the connecting element associated with this slot is proximal to the output of the waveguide 1 (arrow F2) to limit the reflection phenomenon and allow better coupling.

This variant with several slots improves the probabilities of detection of the photon.

A method for producing a photon detection device is illustrated in FIGS. 9 to 13 and comprises, on a substrate 6, the following steps:

forming a waveguide 1 (FIGS. 9, 10),

forming, at a distance from the waveguide 1, a detection element 2 comprising a superconducting track 4, and an electrically conductive layer 5 in electrical contact with the superconducting track 4 at the coupling zone of the detection element 2 with the waveguide 1.

In other words, the waveguide 1 and the detection element 2 are made in planes offset so that the detection element 2 partially covers the waveguide 1 at the coupling zone. Preferably, the detection element 2 is oriented along a longitudinal axis A1 of the waveguide 1. According to a development, after formation of the waveguide 1, the latter is encapsulated or partially covered (FIG. 11), before the formation of the detection element, by a dielectric material 7 having a low refractive index with respect to the refractive index of the waveguide 1, this dielectric material 7 is preferably silicon oxide. By low index is meant a material whose refractive index is between 1 and 1.7. This encapsulation makes it possible in particular to shift the waveguide 1 of the future detection element 2 so as to keep them at a distance. Preferably, the device may advantageously be produced as illustrated in FIG. 9 from a SOI type substrate (silicon 8 on insulator 9). Thus, the step of forming the waveguide 1 is carried out by partial or total etching of the upper layer of silicon 8 (FIGS. 9 and 10). By total etching is meant the etching of the upper silicon layer 8 to the insulating layer 9 to form the silicon waveguide 1. Partial etching makes it possible, for example, to form networks or ribs for coupling to an optical fiber as described previously.

As illustrated in FIG. 12, the detection element 2 can be formed above the waveguide 1 on the dielectric 7, covering the silicon waveguide 1, by depositing and structuring an electrically conductive material intended to to form the layer 5, then by depositing and structuring a superconducting material intended to form the track 4. Of course, the other embodiment can also be made by depositing and structuring a superconducting material intended to form the track and then depositing and structuring an electrically conductive material for forming the electrically conductive layer. Ultra-thin hooked layers can also be deposited to promote the deposition of the layers intended to form the elements referenced 4 and 5. According to one variant, the detection element 2 can also be formed using the Damascene method, the dielectric 7 covering the waveguide 1 then being structured so as to form a trench (FIG. 13) in which the element will be produced. detection 2, for example by deposition of two successive layers (superconducting layer and then electrically conductive layer or vice versa) and polishing steps. The Damascene method has the advantage of forming a detection element 2 whose edges are more abrupt and less rough than those obtained by a direct etching of the materials. This method also allows the use of materials whose direct etching is not easily reproducible such as copper.

Of course, the method described above can be adapted to achieve the structure of the slot-based coupling zone, rectilinear or U-shaped, the etching masks or trenches of the Damascene process adapting to the desired architecture.

Such a photon detection device notably allows single photon counting in the infrared range, the secure transmission of information.

The invention also makes it possible to be sensitive to the TE or TM polarization of the incident wave in order, for example, to decrypt information. Of course, this device can be used in any field in which an accurate count of photons is used.

The device described above makes it possible to reduce downtime. The addition of the electrically conductive layer makes it possible, among other things, to increase the power density and to slow down a photon, thus improving its probability of detection.

Claims

claims

A photon detection device comprising:

a photon detection element (2) comprising a superconducting track (4),

a waveguide (1) arranged to be coupled to the detection element (2) by surface plasmon at a coupling zone, said waveguide (1) being kept at a distance from the sensing element (2), characterized in that at the coupling region the sensing element (2) has an electrically conductive layer (5) in electrical contact with the superconducting track (4).

2. Device according to claim 1, characterized in that the superconducting track (4) comprises a superconducting state and a metallic state, the electrical resistivity of the superconducting track (4) in its metallic state being greater than the electrical resistivity of the layer. (5) electrically conductive.

3. Device according to one of claims 1 and 2, characterized in that the layer (5) electrically conductive is disposed between the superconducting track (4) and the waveguide (1).

4. Device according to one of claims 1 and 2, characterized in that the superconducting track (4) is disposed between the layer (5) electrically conductive and the waveguide (1).

5. Device according to one of claims 1 to 4 characterized in that the sensing element (2) partially overlaps the waveguide (1) at the coupling area, and in that the length of recovery (Lr) partial waveguide (1) by the detection element (2) is a multiple odd integer of an effective coupling length between the waveguide (1) and the detection element (2).

6. Device according to claim 1, characterized in that the detection element (2) forms a resonant cavity arranged to trap an incident photon.

7. Device according to claim 6, characterized in that the sensing element (2) partially overlaps the waveguide (1) at the coupling area, and in that the length of recovery (Lr) partial of the waveguide (1) by the sensing element (2) is equal to an odd multiple of the effective coupling length between the waveguide (1) and the sensing element (2), the length total of the sensing element (2) being equal to

λ

overlap length plus cavity length equal to * ", with

^ΔH eff λ the incident wavelength and "" the effective index of the mode propagating in the detection element (2).

8. Device according to claim 6, characterized in that the waveguide (1) is structured by a mirror downstream of the detection element (2) in the direction of movement of the wave in the guide of wave (1), said mirror being arranged to reflect an unabsorbed photon towards the detection element (2) and to allow a second passage of the photon in the detection element (2).

9. Device according to any one of claims 1 to 8, characterized in that the distance separating the waveguide (1) from the detection element (2) at the level of the coupling zone is between 10 nm and 500nm.

10. Device according to any one of claims 1 to 9, characterized in that the thickness of the layer (5) electrically conductive is between 10 and 200nm.

11. Device according to any one of claims 1 to 10, characterized in that the detection element (2) has a total thickness, at the coupling area, between 11 nm and 21 nm.

12. Device according to any one of claims 1 to 11 characterized in that the sensing element (2) has a U-shape in a plane parallel to the plane of the waveguide (1), the two branches ( 2a, 2b) of the U partly covering the waveguide (1).

13. A method of producing a photon detection device according to any one of claims 1 to 12, characterized in that it comprises, on a substrate, the following steps:

- forming a waveguide (1),

forming, at a distance from the waveguide (1), a detection element (2) comprising an electrically conductive layer (5) in electrical contact with a superconducting track (4) at a coupling zone of the sensing element (2) with the waveguide (1).