Sensor device and method for detecting a substance

Abstract

A sensor device with the following features is provided: - an optical cavity (3), - fluorescent emitters (7) configured for emitting secondary electromagnetic radiation (8), when excited by primary electromagnetic radiation (9), and - binding sites (10) configured for binding of the substance (11) to be detected, wherein - the secondary electromagnetic radiation (8) comprises a resonance wavelength of an optical bound state in continuum (4) of the optical cavity (3) and / or a resonance wavelength of an optical quasi bound state in continuum of the optical cavity (3), and - the binding sites (10) are arranged such that an optical symmetry of the optical cavity (3) is broken, when the substance (11) to be detected binds to the binding sites (10). Further, a method for detecting a substance is provided.

Description

[0001] Description

[0002] SENSOR DEVICE AND METHOD FOR DETECTING A SUBSTANCE

[0003] A sensor device and a method for detecting a substance are provided .

[0004] An improved sensor device , particularly configured for detecting low concentrations of a substance , is to be provided . Further, an improved method for detecting particularly low concentrations of a substance is to be provided .

[0005] These problems are solved by a sensor device with the features of claim 1 and a method with the steps of claim 13 .

[0006] Improved developments and embodiments of the sensor device and the method for detecting a substance are given in the respective dependent claims .

[0007] According to an embodiment , the sensor device is configured for detecting a substance . Particularly, the sensor device detects the substance during operation .

[0008] According to a further embodiment , the sensor device comprises an optical cavity . Particularly, the optical cavity is configured to locali ze a plurality of optical states during operation of the sensor device . Particularly, the plurality of optical states is partially or completely locali zed within the optical cavity during operation of the sensor device . Particularly, the plurality of optical states is partially or completely locali zed withing the optical cavity comprises a, particularly symmetry protected, optical bound state in continuum and / or an optical quasi bound state in continuum .

[0009] According to a further embodiment , the sensor device comprises fluorescent emitters configured for emitting secondary electromagnetic radiation when excited by primary electromagnetic radiation . The fluorescent emitters particularly absorb some or all of the primary electromagnetic radiation and convert the absorbed energy by electronic processes on atomic and / or molecular level in secondary electromagnetic radiation . Particularly, the absorbed primary electromagnetic radiation generates excited electronic states within the fluorescent emitters , which decay due to fluorescence under spontaneous emission of the secondary electromagnetic radiation within a fluorescent li fetime . During fluorescence only allowed transitions between two electronic states of the excited fluorescent emitter occur . Therefore , the excited electronic states decay in a short fluorescent li fetime . For example , the fluorescent li fetime lies between and including 10- 9s and 10-7s .

[0010] Particularly, the primary electromagnetic radiation has at least partially smaller wavelengths than the secondary electromagnetic radiation . In other words , the fluorescent emitters convert the primary electromagnetic radiation in the secondary electromagnetic radiation having longer wavelengths than the primary electromagnetic radiation . For example , the wavelengths of the primary electromagnetic radiation and the wavelengths of the secondary electromagnetic radiation are completely distinct or overlap partially with each other . Particularly, the wavelengths of the primary electromagnetic radiation and wavelengths of the secondary electromagnetic radiation are di f ferent from each other . According to a further embodiment , the sensor device comprises binding sites configured for binding of the substance to be detected . For example , the substance to be detected binds to the binding sites on a molecular level , for example by a chemical reaction and / or physical absorption . For example , the substance to be detected binds by ligands and / or binding molecules to the binding sites . For example , the substance to be detected binds by a key lock principle to the binding sites . For example , the substance to be detected comprises a ligand and the binding site comprises a receptor for the ligand and the ligand of the substance to be detected chemically reacts with the receptor such that the substance to be detected binds to the binding site .

[0011] According to a further embodiment of the sensor device , the secondary electromagnetic radiation comprises a resonance wavelength of an optical bound state in continuum and / or a resonance wavelength of an optical quasi bound state in continuum of the optical cavity . Particularly, the optical bound state in continuum and the optical quasi bound state in continuum are part of the plurality of optical states locali zed in the optical cavity during operation of the sensor device .

[0012] Particularly, the optical bound state in continuum is an eigenstate of the optical cavity and / or has an infinite Q- factor, particularly in the absence of absorption . Further, a momentum of the optical bound state in continuum lies , particularly, within a cone of propagating modes of electromagnetic radiation of a space or ambient media surrounding the optical cavity . Further, the optical bound state in continuum does not interact with any other of the optical states of the continuum . Particularly, the optical bound state in continuum does not emit in and cannot be excited by any electromagnetic radiation that come from the infinity . Particularly, the optical bound state in continuum has a real energy eigenvalue in the absence of absorption and / or is symmetry protected . By the term " symmetry protected" , it is meant that the eigenfield profile of the optical bound state in continuum have a symmetry that disallows it to couple to propagating modes in the continuum that would have been eligible momentum wise . The optical bound state in continuum does not interact with the optical states of the continuous spectrum and cannot radiatively decay, in particular .

[0013] Optical quasi bound states in continuum are resonant optical states of the optical cavity with a resonance wavelength and long li fetimes . The optical quasi bound states in continuum can be excited by the secondary electromagnetic radiation comprising or consisting of electromagnetic radiation with the resonance wavelength of the optical quasi bound state . In contrast to optical bound states in the continuum, optical quasi bound states in continuum have finite Q- factors even in the absence of absorption due to coupling to radiative channels .

[0014] For example , the secondary electromagnetic radiation comprises or consists of a resonant wavelength of the optical bound state in continuum and / or of the optical quasi bound state in continuum . Particularly, the secondary electromagnetic radiation is configured to couple the optical bound state in continuum and / or to the optical quasi bound state in continuum . According to a further embodiment of the sensor device , the binding sites are arranged such that an optical symmetry of the optical cavity is broken when the substance to be detected binds to the binding sites . Particularly, the optical cavity comprises optical active structures arranged in a symmetric pattern . Particularly, the optical active structures are configured to locali ze optical states such as the optical bound state in continuum and / or the optical quasi bound state in continuum within the optical cavity . Particularly, the binding sites are asymmetrically arranged with respect to the optical cavity, and, particularly with respect to the active structures of the optical cavity . For example , the optical structures are nanoantennas or elements of a photonic crystal .

[0015] According to an embodiment , the sensor device configured to detect a substance comprises :

[0016] - the optical cavity,

[0017] - the fluorescent emitters configured for emitting the secondary electromagnetic radiation when excited by the primary electromagnetic radiation,

[0018] - the binding sites configured for binding of the substance to be detected, wherein

[0019] - the secondary electromagnetic radiation comprises the resonance wavelength of the optical bound state in continuum and / or the resonance wavelength of the optical quasi bound state in continuum of the optical cavity, and

[0020] - the binding sites are arranged such that the optical symmetry of the optical cavity is broken, when the substance to be detected binds to the binding sites . According to a further embodiment of the sensor device , secondary electromagnetic radiation is coupled out of the optical cavity, when the optical symmetry of the optical cavity is broken . Particularly, the substance to be detected breaks the optical symmetry of the cavity when it binds to the binding sites which are arranged asymmetrically with respect to the symmetry of the optical cavity .

[0021] The sensor device is based on the idea that a symmetry of the optical cavity is broken, when some or all binding sites are occupied by the substance to be detected . When the substance to be detected binds to the binding sites within the optical cavity, they act as scattering centers . Particularly, the substance to be detected bound to the binding cites scatters secondary electromagnetic radiation during operation of the sensor device . By breaking the symmetry of the optical cavity by the substance to be detected bound to the binding sites , the optical bound state in continuum is converted to an optical quasi bound state in continuum with a resonance wavelength di f ferent from the resonance wavelength of the optical bound state in continuum . The secondary electromagnetic radiation couples to the quasi-bound state in continuum and is coupled out from the optical cavity . In other words , secondary electromagnetic radiation is coupled out from the optical cavity when the substance to be detected binds to the binding sides , since the optical symmetry of the optical cavity is broken . I f there is no substance to be detected bound to the binding sites , no electromagnetic radiation escapes from the optical cavity .

[0022] According to a further embodiment , the sensor device comprises a detector configured for detecting the secondary electromagnetic radiation coupled out of the optical cavity in a time-resolved manner . Particularly, the detector detects the secondary electromagnetic radiation coupled out of the optical cavity in a time-resolved manner when the optical symmetry of the optical cavity is broken due to the substance to be detected bound to the binding sites . Particularly, the secondary electromagnetic radiation coupled out of the optical cavity due to the broken optical symmetry of the optical cavity generates a detectable optical signal in a far field of the optical cavity which is detected by the detector during operation . For example , the detector comprises or consists of a photodiode . With the help of time-resolved detection of the optical signal even small amounts of the substance to be detected can be detected .

[0023] According to a further embodiment , the sensor device comprises a pump light source configured to irradiate the fluorescent emitters with primary electromagnetic radiation . Particularly, the pump light source irradiates the fluorescent emitters with primary electromagnetic radiation during operation . For example , the pump light source comprises or consists of a laser, such as a semiconductor laser, for example an edge emitting semiconductor laser or a VCSEL ( short for "vertical cavity surface emitting laser" ) . Particularly, the primary electromagnetic radiation emitted by the laser is coherent .

[0024] According to a further embodiment of the sensor device , the binding sites do not break the optical symmetry of the optical cavity . This ensures that no electromagnetic radiation escapes from the optical cavity when no substance to be detected is bound to the binding sites . Particularly, the binding sites are matched to a refractive index of a background material of the optical cavity . For example , the background material of the optical cavity is a material of a carrier, on which the optical structures such as nanoantennas are arranged . Preferably, the binding sites do not have a refractive index di f fering more than 5% or more than 1 % or more than 0 . 1 % from the background material of the optical cavity .

[0025] According to a further embodiment of the sensor device , the substance to be detected is at least one of a molecule , for example a disease speci fic marker molecule , at least a part of a virus and / or at least a part of a bacterium . For example , the disease speci fic marker molecule part of a cell wall of a bacterium and / or a part of a DNA and / or a part of an RNA of the virus and / or a part of a DNA and / or a part of an RNA of the bacterium to be detected .

[0026] According to a further embodiment of the sensor device , the fluorescent emitters comprise or consist of quantum dots . Quantum dots are , particularly, small fluorescent semiconductor particles having a si ze within the nanometer region . The wavelength conversion properties of the quantum dots are due to their limited dimensions , in particular . Quantum dots can comprise a core and a shell ("core shell quantum dot" ) , wherein the core and the shell comprise or consist of a semiconductor material . A bandgap of the shell is , particularly, adapted by the help of the material and the si ze in such a way that the shell absorbs the primary electromagnetic radiation . The core of the quantum dot is adapted by the help of the material and the si ze such that the core reemits energy of the absorbed primary electromagnetic radiation as secondary electromagnetic radiation . Core , or core and shell , of the quantum dot has , for example , a diameter between and including 2 nanometers and 20 nanometers . Particularly, the quantum dots are suitable as fluorescent emitters due to their small si ze .

[0027] According to a further embodiment , the fluorescent emitters experience Purcell enhancement of at least 10 times within the optical cavity . In other words , the Purcell factor of the optical cavity is at least 10 or at least 1000 . For example , the Purcell factor lies in a range up to 104.

[0028] According to the Purcell ef fect , the probability of spontaneous emission, for example of secondary electromagnetic radiation of the fluorescent emitters , is enhanced by placing the respective emitter, for example the fluorescent emitter, in a resonator, such as the optical cavity . I f a zeroth mode of the resonator is resonant with the emitter and the emitter is placed exactly in the center of the resonator, the emission rate increases by the Purcell factor .

[0029] A high Purcell enhancement of the fluorescent emitters ensures that the fluorescent li fetime is signi ficantly smaller than the li fetime of the optical bound in continuum state . Particularly, the optical cavity supporting the optical bound in continuum state preferably has minimal absorption losses in order to achieve large Purcell enhancement .

[0030] Particularly, the fluorescent li fetime of a fluorescent state of the fluorescent emitters is signi ficantly smaller than a li fetime of the optical bound state in continuum and / or a li fetime of an optical quasi bound state in continuum . Particularly preferably, the fluorescent li fetime of the fluorescent emitters is 10 times to 100 times smaller than the li fetime of the optical bound state in continuum and / or the li fetime of the optical quasi bound state in continuum .

[0031] I f the Purcell enhancement is strong and the fluorescent li fetime of the fluorescent emitter is signi ficantly smaller than the li fetime of the optical bound state in continuum and / or the optical quasi bound state in continuum, only the far field of the secondary electromagnetic radiation coupled out of the optical cavity is to be detected by the detector after the fluorescent li fetime .

[0032] Preferably, a signal to noise ratio of the sensor device is only limited by a fundamental noise of the detector . Therefore , the sensor device provides , advantageously, an ultra-high signal to noise ratio . Particularly, the optical signal detected by the detector increases monotonously with increasing power of the pump source , while the noise power of the detector remains low and constant .

[0033] According to a further embodiment of the sensor device , the optical cavity is generated by a plurality of nanoantennas arranged in a symmetrical pattern . The nanoantennas are particularly configured to interact and / or receive the secondary electromagnetic radiation . Particularly, the optical cavity supports the , particularly symmetry protected, bound states in the continuum . Further, the nanoantennas are configured to emit secondary electromagnetic radiation when they are excited by the secondary electromagnetic radiation .

[0034] The symmetrical pattern of the nanoantennas has , preferably, at least a threefold symmetry . For example , the symmetrical pattern of the nanoantennas is a hexagonal grid or a cubic grid . Particularly, a lattice constant of the symmetrical pattern of the nanoantennas lies within a wavelength of the secondary electromagnetic radiation . For example , the lattice constants lie between and including Xef / 5 and Xef , wherein Xef is an ef fective wavelength X / n of an ambient medium with refractive index n .

[0035] Particularly, the optical bound state in continuum and / or the optical quasi bound in continuum state is locali zed and / or supported by the nanoantenna array . Particularly, the nanoantennas form or are part of a metasurface .

[0036] For example , the nanoantennas comprise or consist of a, particularly high index, dielectric material such as an oxide , for example TiCy . Further, it is possible that the nanoantennas comprise or consist of a semiconductor material , for example silicon . Particularly, the nanoantennas can comprise or consist of a metal , such as Au, Ag and / or Al .

[0037] For example , the nanoantennas are arranged on a carrier as well as the binding sites . For example , the carrier comprises or consists of the background material of the optical cavity, which is particularly preferably index-matched to the binding sites . For example , the carrier comprises or consists of a dielectric material , such as a silicon dioxide .

[0038] According to a further embodiment of the sensor device , the binding sites are arranged of f-axis to the nanoantennas . In such a way symmetry is broken when the substance to be detected binds to the binding sites . For example , the binding sites are also arranged in a regular pattern within the optical cavity, the regular pattern being arranged asymmetrical with respect to the symmetrical pattern of the nanoantennas .

[0039] According to a further embodiment , the sensor device further comprises compensation structures arranged within the optical cavity . The compensation structures are particularly configured to compensate an optical impact of the binding sites to the optical cavity, particularly in the case that the binding sites are not index-matched with the background material of the optical cavity . For example , the compensation structures and the binding sites form a symmetrical arrangement being arranged symmetrically with respect to the optical structures supporting the optical cavity, such as the nanoantennas .

[0040] According to a further embodiment of the sensor device , the optical cavity is generated by a multilayer slab waveguide structure . For example , a one or two-dimensional photonic crystal is incorporated in the multilayer slab waveguide structure ) . A photonic crystal in one dimension comprises or consists of structures which are periodically in one direction . A photonic crystal in two dimensions comprises or consists of structures which are periodically in two directions . Particularly, the patterned multilayer slab waveguide can be used as an alternative to the nanoantennas in order to form an optical cavity which support the optical bound state in continuum and / or the optical quasi-bound state in continuum .

[0041] For example , the sensor device can be used in medical applications , for example for vital sign monitoring, or for environmental monitoring, for example in horticulture or aquaculture . In the following a method for detecting a substance is described . For example , the method can be carried out with the sensor device configured for detecting a substance as disclosed herein . Therefore , embodiments and features disclosed in connection with the sensor device can also be embodied within the method for detecting a substance and vice versa .

[0042] According to an embodiment of the method, an optical cavity configured to support an optical bound state in continuum and / or an optical quasi bound state in continuum is provided .

[0043] According to an embodiment of the method, fluorescent emitters are excited with primary electromagnetic radiation such that the fluorescent emitters emit secondary electromagnetic radiation . Particularly, the secondary electromagnetic radiation has a resonant wavelength of the optical bound state in continuum and / or of the optical quasi bound state in continuum .

[0044] According to a further embodiment of the method, a substance to be detected binds to binding sites such that an optical symmetry of the optical cavity is broken and electromagnetic radiation is coupled out of the optical cavity . Particularly, secondary electromagnetic radiation is coupled out of the optical cavity . When the symmetry of the optical cavity is broken, the optical bound state in continuum is converted to an optical quasi bound state in continuum having radiation losses , for example .

[0045] Particularly, the method comprises the following steps : - providing the optical cavity configured to support the optical bound state in continuum and / or the optical quasi bound state in continuum,

[0046] - exciting the fluorescent emitters with the primary electromagnetic radiation such that the fluorescent emitters emit the secondary electromagnetic radiation, and

[0047] - binding of the substance to be detected to the binding sites such that the optical symmetry of the optical cavity is broken and secondary electromagnetic radiation is coupled out of the optical cavity .

[0048] Particularly, the steps are carried out in the given order .

[0049] According to a further embodiment of the method, a pump light source irradiates the fluorescent emitters with the primary electromagnetic radiation such that the fluorescent emitters emit secondary electromagnetic radiation .

[0050] According to a further embodiment of the method, the secondary electromagnetic radiation is coupled out of the optical cavity and detected with a detector in a time- resolved manner . Particularly, the secondary electromagnetic radiation coupled out of the optical cavity has a resonant wavelength of an optical quasi bound state in continuum . Particularly, the secondary electromagnetic radiation coupled out from the optical cavity is detected in the far field .

[0051] With the present method, detection of the substances to be detected in situ and in real time is possible advantageously .

[0052] Further preferred embodiments and developments of the sensor device and the method for detecting a substance are described in the following in connection with the Figures . Figure 1 shows a schematical view of a sensor device according to an exemplary embodiment .

[0053] Figure 2 shows schematically a flow diagram of a method for detecting a substance according to an exemplary embodiment .

[0054] Figures 3 to 4 show schematical views of a sensor device according to a further exemplary embodiment .

[0055] Figure 5 shows a schematical view of a sensor device according to a further exemplary embodiment .

[0056] Figures 6 to 11 show schematically diagrams of an intensity I of an optical signal dependent on time t generated during a method for detecting a substance according to three embodiments .

[0057] Equal or similar elements as well as elements of equal function are designated with the same reference signs in the Figures . The Figures and the proportions of the elements shown in the Figures are not regarded as being shown to scale . Rather, single elements , in particular layers , can be shown exaggerated in magnitude for the sake of better presentation and / or better understanding .

[0058] The sensor device according to the exemplary embodiment of Figure 1 comprises a carrier 1 comprising or consisting of an oxide such as silicon oxide .

[0059] A plurality of nanoantennas 2 is arranged on a main surface of the carrier 1 in a symmetrical pattern, at present in a cubic grid . The nanoantennas 2 form an optical cavity 3 supporting a symmetry protected optical bound state in continuum ( SP-BIC ) 4 with a positive phase 5 and a negative phase 6 . Particularly, the optical bound state in continuum 4 of the optical cavity 3 of Figure 1 has an antisymmetric eigenfield profile which does not radiate to a far- field .

[0060] Further, the sensor device comprises fluorescent emitters 7 . At present , the fluorescent emitters 7 are introduced in the carrier 1 . It is also possible that the fluorescent emitters 7 are introduced in the nanoantennas 2 . For example , the fluorescent emitters 7 are quantum dots emitting secondary electromagnetic radiation 8 , when excited by primary electromagnetic radiation 9 .

[0061] Further, the sensor device of Figure 1 comprises a plurality of binding sites 10 configured for binding a substance 11 to be detected . At present , the substance 11 to be detected is , for example , a bacterium, a virus or a disease speci fic marker molecule . The binding sites 10 comprise , for example , selective chemical bonding agents .

[0062] The binding sites 10 are , as the nanoantennas 2 , arranged in a regular pattern . At present , the binding sites 10 are arranged in straight equidistant lines running parallel to each other . Further, the straight equidistant lines of binding sites 10 are arranged parallel to straight lines of the cubic lattice of the nanoantennas 2 . However, the binding sites 10 are arranged in an asymmetric manner with respect to the nanoantennas 2 . Particularly, next to each straight line of nanoantennas 2 a straight line of binding sites 10 is arranged, wherein an opposite side of the straight line of nanoantennas 2 is free of binding sites 10 . In other words , the binding sites 10 are arranged of f-axis to the nanoantennas 2 .

[0063] Further, the sensor device according to Figure 1 comprises compensation structures 12 . The compensation structures 12 are arranged in straight lines running parallel to the straight lines of the binding sites 10 and are further arranged on the sides of the nanoantennas 2 opposite to the binding sites 10 . The compensation structures 12 compensate an optical impact of the binding sites 10 on the optical cavity 3 , when a refractive index of the binding sites 10 is not matched with a refractive index of a background material of the optical cavity 3 such as the material of the carrier 1 . In such a way, breakage of the optical symmetry of the optical cavity 3 due to the binding sites 10 alone without a substance 11 to be detected bound to the binding sites 10 is avoided .

[0064] Further, the sensor device of Figure 1 comprises a pump light source 13 emitting the primary electromagnetic radiation 9 exciting the fluorescent emitters 7 such that the fluorescent emitters 7 emit the secondary electromagnetic radiation 8 . The pump light source 13 is , for example , a semiconductor laser emitting coherent primary electromagnetic radiation .

[0065] When the substance 11 to be detected binds to some or all of the binding sites 10 , the optical symmetry of the optical cavity 3 is broken such that the optical bound state in continuum 4 supported by the optical cavity 3 is converted to an optical quasi bound state in continuum also supported by the optical cavity 3 . The secondary electromagnetic radiation 8 of the fluorescent emitters 7 couples to the optical quasi bound state in continuum and secondary electromagnetic radiation 9 is emitted from the optical cavity 3 as an optical signal 14 and detected by a detector 15 in a time- resolved manner . The detector 15 is a photodiode , for example .

[0066] According to the method for detecting a substance 11 of the exemplary embodiment of Figure 2 , am optical cavity 3 supporting an optical bound state in continuum 4 is provided in a first step S I . For example , the optical cavity 3 is generated by a plurality of symmetrically arranged nanoantennas 2 as described in connection with Figure 1 .

[0067] In a further step S2 , fluorescent emitters 7 are excited with a primary electromagnetic radiation 9 such that the fluorescent emitters 7 emit secondary electromagnetic radiation 8 . The primary electromagnetic radiation 9 is , for example , emitted by a pump light source 13 such as a semiconductor laser .

[0068] In a further step S3 , the substance 11 to be detected binds to binding sites 10 within the optical cavity 3 such that an optical symmetry of the optical cavity 3 is broken and secondary electromagnetic radiation 8 is coupled out of the optical cavity 3 . An optical signal 14 of the secondary electromagnetic radiation 8 coupled out of the optical cavity 3 is detected by a detector 15 in a time-resolved manner .

[0069] Instead of a plurality of nanoantennas 2 as described in connection with Figure 1 , the sensor device according to the exemplary embodiment of Figures 3 and 4 comprises a plurality of periodically arranged nanostructures 16 forming a photonic crystal 17 . Figure 4 shows a schematic sectional view of the sensor device according to Figure 3 . The nanostructures 16 form a cubic grid, wherein the nanostructures 16 are arranged along parallel running straight lines . The periodically arranged nanostructures 16 are arranged as separate elements on a waveguiding thin film layer 18 comprising fluorescent emitters 7 , such as quantum dots .

[0070] The fluorescent emitters 7 emit secondary electromagnetic radiation 8 when excited with primary electromagnetic radiation 9 , for example irradiated by a pump light source 13 (not shown) . The waveguiding thin film layer 18 is arranged on a carrier 1 . Particularly, an optical bound state in continuum 4 is locali zed within the waveguiding thin film layer 18 during operation of the sensor device . The optical bound in continuum state 4 is particularly supported by the periodic nanostructures 16 forming the optical cavity 1 .

[0071] Further, the sensor device according to the exemplary embodiment of Figures 3 and 4 comprises binding sites 10 , which are arranged asymmetrically with respect to the nanostructures 16 . Equivalent to Figure 1 , the binding sites 10 are arranged along straight lines running only at one side of a straight line of the cubic grid of the periodically arranged nanostructures 16 .

[0072] Figure 5 shows a schematical sectional view of a sensor device with periodic nanostructures 16 according to a further exemplary embodiment . In contrast to the exemplary embodiment of Figures 3 and 4 , the periodic nanostructures 16 are not additionally formed on the waveguide thin film layer 18 comprising the fluorescent emitters 7 but are structured within the waveguide thin film layer 18 having the fluorescent emitters 7 . Particularly, the waveguide thin film layer 18 is provided with recesses 19 between the nanostructures .

[0073] Figures 6 to 11 show examples of an intensity I of an optical signal 14 detected by the detector 15 dependent on time t during a method for detecting a substance 11 . In each case , to denotes the time when excitation of an optical bound state in continuum 4 is carried out , for example by irradiating the fluorescent emitters 7 with primary electromagnetic radiation 9 of a pump light source 13 . Further, time ti denotes the time when unwanted emission of secondary electromagnetic radiation 8 can be neglected in the time resolved optical signal 14 .

[0074] In each case Figures 6 , 8 and 10 show the intensity I the optical signal 14 to be detected by the detector 15 of the sensor device wherein no substance 11 to be detected is bound to binding sites 10 . In other words , Figures 6 , 8 and l Oshow the optical signal 14 when a symmetry of an optical cavity 3 is not broken . Further, Figures 7 , 9 and 11 show the optical signal 14 to be detected by the detector 15 of the sensor device when the substance 11 to be detected is bound to the binding sites 10 .

[0075] Figures 6 and 7 show the intensity I of the optical signal 14 in an ideal case , wherein the optical bound in continuum state 4 supported by the optical cavity 3 is excited exclusively by secondary electromagnetic radiation 8 emitted by the fluorescent emitters 7 . In that case , no optical signal 14 is detected by the detector 15 as the secondary electromagnetic radiation 8 only couples to the optical bound in continuum state 4 which has no radiative losses ( see Figure 6 ) .

[0076] Figure 7 shows the intensity I of the optical signal 14 detected by the detector 15 in the ideal case , when a substance 11 to be detected is bound to binding sites 10 of the optical cavity 3 breaking the symmetry of the optical cavity 3 such that the symmetry protected bound state in continuum 4 becomes an optical quasi bound state in continuum with radiative emission resulting in an optical signal 14 decaying with time .

[0077] Figures 8 and 9 show an intensity I of an optical signal 14 when secondary electromagnetic radiation 8 couples not only to an optical bound state in continuum 4 , but also to other optical states with a low Q factor supported by the optical cavity 3- Further, a Purcell factor of the optical cavity 3 is large enough such that all other unwanted optical signals 14 are neglectable after time ti .

[0078] Figure 8 shows the intensity I of the optical signal 14 when no substance 11 to be detected is bound to the binding sites 10 . As can be seen in Figure 8 , during the time interval between to and ti there is a small optical signal 14 which is zero after time ti .

[0079] Figure 9 shows the optical signal 14 when the substance 11 to be detected is bound to the binding sites 10 of the sensor device . As can be seen, an optical signal 14 exists after time ti , since the substance 11 to be detected bound to some or all binding sites 10 of the optical cavity 3 scatters the optical quasi bound in continuum state . Figures 10 and 11 show the intensity I of an optical signal 14 in the case that the optical cavity 3 does not support a symmetry protected optical bound state in continuum 4 but only a quasi-bound state in continuum, for example due to a finite si ze and / or defects of the optical system .

[0080] Particularly, the quasi-bound state in continuum has a high Q factor .

[0081] Figure 10 shows the intensity I of the optical signal 14 when no substance 11 to be detected is bound to the binding sites 10 . In that case , contrary to Figures 6 and 8 , there will be an optical baseline signal after time ti which will limit a signal to noise ratio of the sensor device .

[0082] Figure 10 shows , particularly, the case where the target mode is not perfectly bounded in the continuum for example due to fabrication imperfections causing the mode to only be ( quasi- ) bounded and thus leakage of light .

[0083] Figure 11 shows the intensity I of the optical signal 14 when the substance 11 to be detected is bound to the binding sites 10 of the sensor device . As , for example , seen in Figure 11 , after time ti there is a signi ficant intensity of the optical signal 14 , and the signal to noise ratio of the sensor device will be limited by this optical background signal .

[0084] The present application claims priority of the German application DE 102023134618 . 0 , the disclosure content of which is incorporated herein by reference .

[0085] The invention is not limited to the description of the exemplary embodiments . Rather, the invention comprises each new feature as well as each combination of features , particularly each combination of features of the claims, even if the feature or the combination of features itself is not explicitly given in the claims or the exemplary embodiments.

[0086] References

[0087] 1 carrier

[0088] 2 nanoantenna

[0089] 3 optical cavity

[0090] 4 optical bound state in continuum

[0091] 5 positive phase

[0092] 6 negative phase

[0093] 7 fluorescent emitter

[0094] 8 secondary electromagnetic radiation

[0095] 9 primary electromagnetic radiation

[0096] 10 binding site

[0097] 11 substance to be detected

[0098] 12 compensation structure

[0099] 13 pump light source

[0100] 14 optical signal

[0101] 15 detector

[0102] 16 nanostructure

[0103] 17 photonic crystal

[0104] 18 waveguiding thin film layer

[0105] 19 recess

[0106] S I , S2 , S3 method steps I intensity t time

Claims

Claims1. Sensor device configured for detecting a substance (11) , the sensor device comprises:- an optical cavity (3) ,- fluorescent emitters (7) configured for emitting secondary electromagnetic radiation (8) , when excited by primary electromagnetic radiation (9) , and- binding sites (10) configured for binding of the substance (11) to be detected, wherein- the secondary electromagnetic radiation (8) comprises a resonance wavelength of an optical bound state in continuum (4) of the optical cavity (3) and / or a resonance wavelength of an optical quasi bound state in continuum of the optical cavity ( 3 ) , and- the binding sites (10) are arranged such that an optical symmetry of the optical cavity (3) is broken, when the substance (11) to be detected binds to the binding sites (10) .

2. Sensor device according to the previous claim, wherein secondary electromagnetic radiation (8) is coupled out of the optical cavity (3) , when the optical symmetry of the optical cavity (3) is broken.

3. Sensor device according to any of the previous claims, further comprising a detector (15) configured for detecting the secondary electromagnetic radiation (8) coupled out of the optical cavity (3) in a time-resolved manner.

4. Sensor device according to any of the previous claims, further comprising a pump light source (13) configured to irradiate the fluorescent emitters (7) with the primary electromagnetic radiation ( 9 ) .

5. Sensor device according to any of the previous claims, wherein the binding sites (10) do not break the optical symmetry of the optical cavity (3) .

6. Sensor device according to any of the previous claims, wherein the substance (11) to be detected is at least one of a molecule, at least of a virus and / or at least a part of a bacterium.

7. Sensor device according to any of the previous claims, wherein the fluorescent emitters (7) comprise quantum dots.

8. Sensor device according to any of the previous claims, wherein the fluorescent emitters (7) experience Purcell enhancement of at least 10-times within the optical cavity (3) .

9. Sensor device according to any of the previous claims, wherein- the optical cavity (3) is generated by a plurality of nanoantennas (2) arranged in a symmetrical pattern, the nanoantennas (2) being configured to interact with the secondary electromagnetic radiation (8) , andthe optical cavity (3) supports the bound states in the continuum.

10. Sensor device according to the previous claim, wherein the binding sites (10) are arranged off-axis to the nanoantennas (2) .

11. Sensor device according to any of the previous claims, wherein compensation structures (12) are arranged within the optical cavity ( 3 ) .

12. Sensor device according to any of claims 1 to 8, wherein the optical cavity (3) is generated by multilayer slab waveguide structure.

13. Method for detecting a substance, comprising the steps:- providing an optical cavity (3) configured to support an optical bound state in continuum (4) and / or an optical quasi bound state in continuum,- exciting fluorescent emitters (7) with primary electromagnetic radiation (9) such that the fluorescent emitters (7) emit secondary electromagnetic radiation (8) , and- binding of the substance (11) to be detected to binding sites (10) such that an optical symmetry of the optical cavity (3) is broken and secondary electromagnetic radiation (8) is coupled out of the optical cavity (3) .

14. Method according to the previous claim, wherein a pump light source (15) irradiates the fluorescent emitters (7) with the primary electromagnetic radiation (8) .

15. Method according to any of claims 13 to 14, wherein the secondary electromagnetic radiation (8) coupled out of the optical cavity (3) is detected with a detector (15) in a time resolved manner.

16. Method according to the previous claim, wherein the secondary electromagnetic radiation (8) outcoupled from the optical cavity (3) is detected in a far field.

17. Method according to any of claims 13 to 16 carried out with a sensor device according to any of claims 1 to 12.

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