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    • 专利摘要:
    Procedure, waveguide (1) and system (100) to generate modes close to the cut-off condition (MRL), the waveguide (1) being provided with a substrate (2) with at least one face (3a, 3b) flat with at least one film (4a, 4b) of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and being the absolute value of the part real of the film permittivity greater than the absolute values of the real part of the permittivity of the substrate and of the real part of the permittivity of a respective external element, so that by injecting electromagnetic radiation (6) polarized vertically or horizontally in The substrate generates resonances in TE and/or TM modes corresponding to modes close to the cut condition. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2765026A1
    申请号:ES201831185
    申请日:2018-12-05
    公开日:2020-06-05
    发明作者:Villar Fernandez Ignacio Del；Sanz Jesús María Corres；Lorenzo Omar Fuentes；San Martin Francisco Javier Arregui
    申请人:Universidad Publica de Navarra；
    IPC主号:
    专利说明:

    [0002] Procedure, waveguide and system to generate modes close to the cut condition
    [0004] Technical field of the invention
    [0005] The following invention refers to a method, waveguide and system for generating modes close to the cut-off condition as a sensor or filter, based on the deposit or coating with a thin film on at least one of the faces with the largest surface area. of a flat waveguide, with geometry such as that of a microscope slide, sheet or substrate, and incident polarized light through one of the lateral faces of the waveguide to excite modes close to the cut condition.
    [0007] Background of the Invention
    [0008] The deposition of thin films on a waveguide determines the generation of two fundamental types of resonances: those based on surface plasmons, in English surface plasmon resonance - SPR, (Kretschmann and Raether, Z. Naturforsch. Teil A 23: 2315-2136 , 1968) and resonances based on modes with losses near the cut-off condition, in English lossy mode resonance - LMR, (M. Marciniak, J. Grzegorzewski and M. Szustakowski, IEE Proceedings J., 140: 247-251, 1993). Both resonances have been visualized in the same setup based on Kretschmann configuration (I. Del Villar, V. Torres, M. Beruete, Opt. Lett. 40: 4739-4742, 2015), and also in fiber optics (I Del Villar et al. J. Lightwave Technol. 28: 110: 117, 2010; RC Jorgenson and SS Yee, Sens. & Actuators. B 12: 213, 1993).
    [0010] According to (Yang and Sambles, J. Mod. Opt., 44: 1155-1163, 1997), to excite a surface plasmon and obtain an SPR resonance, the real part of the permittivity of the thin film material must be negative and its absolute value is greater than the absolute value of its imaginary part and greater than the absolute value of the real part of the permittivity of the waveguide and the dielectric surrounding the thin film. On the other hand, in order to excite a mode close to the cut-off condition and generate an LMR resonance, the real part of the permittivity of the thin film material needs to be positive and its absolute value greater than that of its imaginary part and also greater than the absolute value of the real part of the permittivity of the waveguide and the dielectric surrounding the thin film.
    [0011] In addition to the two important differences already mentioned (that in one case a surface plasmon is excited and in the other a guided mode close to the cutting condition, and that the permittivities of the thin film and the substrate necessary for the phenomenon to be triggered are completely different), with the modes close to the cut-off condition, two types of resonances can be generated, those of TE mode, by incidence on the horizontal polarized light guides, and resonances in TM mode, by incidence of vertical polarized light , while the SPR can only observe resonances of one type, those of TM polarization. So, unlike with SPRs, the present invention allows monitoring, by varying the polarization of the incident light, both resonances located at different wavelengths of the spectrum being monitored.
    [0013] Another important difference is that, in contrast to SPR, in MRLs the position of the resonance in the electromagnetic spectrum can be tuned as a function of the thickness of the thin film (I. Del Villar et al. Appl. Opt., 51: 4298: 4307, 2012). Also, each pair of TE and TM resonances can be obtained multiple times for discrete thickness values, and each of these resonances will have a different sensitivity and bandwidth (I. Del Villar et al. Opt. Laser Technol., 763762 , 2015), which is not possible with SPRs. Finally, when the media that surround the thin film (the substrate that acts as a waveguide and the external medium) present a similar index, the sensitivity can be increased in an extraordinary way, reaching up to a million nanometers per refractive index unit in the case of optical fiber as waveguide (A. Ozcariz, CR Zamarreño, P. Zubiate & FJ Arregui, Sci. Rep., 7: 10280, 2017).
    [0015] To date, the phenomenon that has given rise to the greatest number of applications and that has focused the interest of the scientific community is SPR-based devices (J. Homola, SS. Yee, G. Gauglitz. Sens. Actuators B, 54, 3-15, 1999). Regarding the practical implementation of SPR sensors, there are simple schemes in which a flat waveguide is used (US2006147147 and US5991048A), but its commercial development has not been successful, because to excite surface plasmons, the platform is more sensitive and robust. based on Kretschmann configuration (Kretschmann and Raether, Z. Naturforsch. Teil A 23: 2315-2136, 1968). In this configuration, a thin layer of highly reflective metal (eg, gold or silver) is deposited on the base of a prism (US Pat. No. 7015471; US Pat. No. 6738141).
    [0016] The Kretschmann configuration has had great commercial success, but it has drawbacks derived from its geometric configuration, which has greatly restricted its application. All this is due to the need to include a prism that allows the light to be coupled to the metallic film and a controller for the polarization of the incident light. This means that commercial SPR-based devices, while offering high performance, have low portability and a very high price, not achievable for any research center or company.
    [0018] To avoid this problem and achieve a more portable and economical device, the phenomenon has been transferred to the optical fiber, measuring the intensity of light for each wavelength at the output of the fiber after having passed through the sensitive area (US Pat . No.
    [0019] 5327225; Esp. Pat. No. 2114175).
    [0021] However, the optimal angle to generate SPRs is between 40 and 70 ° (C. Rhodes et al., J. Appl. Phys., 100: 54905, 2006), which is not exactly the predominant angle in the signal that it spreads in the optical fiber. In fact, in the optical fiber the light is guided in the longitudinal axis of the fiber, that is, predominantly at 90 °, hence the optical fiber, although it has been used for SPRs (ES2381087A1), is much less suitable than the configuration Kretschmann for the SPR. This explains why the flat waveguides mentioned above, where the light is also guided at an angle close to 90 ° with respect to the normal surface of the metallic film, have not had commercial success either. Hence, commercial SPR-based devices are based on Krestschmann configuration.
    [0023] In contrast, the optimal angle for generating the MRLs is between 85 and 90 °. For these angles, the Kretschmann configuration is very difficult to obtain. It has been achieved in (I. Del Villar, V. Torres, M. Beruete, Opt. Lett. 40: 4739-4742, 2015), but with great difficulty and obtaining a much less clear resonance than in the case of the SPR.
    [0025] On the other hand, in optical fiber the results have been better and numerous publications have been obtained with applications in the field of humidity sensors (CR Zamarreño et al., Sens. & Actuators. B, 146: 414: 417, 2010), pH ( CR Zamarreño et al., Sens. & Actuators. B, 150: 290-297, 2011), chemists (SP Usha, Sens. & Actuators. B, 218: 196: 204, 2015), biosensors (SP Usha Biosensors and Bioelectronics 87, 178-186, 2017), immunosensors (Socorro et al. Sens. & Actuators. B 2014) and even excitation by applying voltage (Corres et al. Opt. Express, 21: 31668-31677, 2013; M. Smietana J. Lightwave Technol.
    [0026] 36: 954: 960, 2018).
    [0028] However, the jump to a commercial application has not occurred because the fiber is a waveguide that has the disadvantage that, if light polarized by the fiber is not guided, the resonances with the highest sensitivity are very wide and difficult to monitor (F. Chiavaioli et al. Anal. Chem. Soc. Sensors, 3: 936-943, 2018). Although there is the option of guiding polarized light, it requires the use of special optical fibers (A. Ozcariz, CR Zamarreño, P. Zubiate & FJ Arregui, Sci. Rep., 7: 10280, 2017), whose cost is incomparably superior to that of, for example, microscope slides.
    [0030] There are also other disadvantages of the fiber-based system compared to the flat waveguide-based system:
    [0031] - With the fiber-based system, for each new optical fiber that is inserted, it is required to make splices using a fusion machine, while for the flat waveguide it is enough to exchange the flat waveguide, which can be a simple holder. - The fiber-based system requires an in-line polarizer and a polarization controller, whose range of wavelengths is limited to a short region of the electromagnetic spectrum, much unlike the system based on a flat waveguide, which it works across a wide spectrum and for which it is sufficient to use an inexpensive polarizing glass instead of the more expensive line polarizer and polarization controller. - The fiber-based system does not enjoy the simplicity of handling the flat waveguide-based system, since in the case of the fiber, a manual tuning of the polarization controller is required each time the device is used, since it depends on the birefringence of the fiber patch cord, while in the case of the flat waveguide a simple glass rotation system allows adjusting the horizontal or vertical polarization.
    [0033] And as proof that the fiber system is not technologically interesting, it should be noted that only one fiber-based MRL patent has been generated: Pat. No. WO / 2011/027016; Esp. Pat. No. P200930656. Thus, with all the aforementioned, the need for a system that solves the above problems is understood.
    [0035] Explanation of the invention
    [0036] The procedure for generating modes near cut-off condition (MRL) of the present invention allows generating modes near cut-off condition on a waveguide provided of a substrate with at least one flat face provided with at least one film placed between the substrate and a respective external element, the film being of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and the absolute value of the real part of the permittivity of the film being greater than the absolute values of the real part of the permittivity of the substrate and of the real part of the permittivity of the respective external element, the method comprising injecting vertical or horizontal polarized electromagnetic radiation into the substrate in a direction essentially parallel to the flat face, so that resonances in TE and / or TM modes corresponding to modes close to the cut-off condition are generated when the radiation interacts electromagnetic polarized with the film or films placed on it; and receive electromagnetic radiation after passing through the waveguide.
    [0038] Through this procedure, the limitations of known fiber optic sensors based on resonance caused by modes close to the cut-off condition (lossy mode resonance - LMR) are overcome, by replacing the sensor region, fiber optic, by a flat waveguide like that of a microscope slide, slide, or substrate. Thanks to the use of the flat waveguide, it is avoided having to connect the optical fiber cables to the sensor fiber, which are connected to the source that emits the electromagnetic radiation and to the detector that receives the electromagnetic radiation after passing through the waveguide. , with what is gained in simplicity and robustness. In addition, the waveguide substrate geometry can be such as a microscope slide, it being less brittle than an optical fiber.
    [0040] Another important difference with respect to the known fiber optic-based sensors of the LMR-based types is that the fact of using a waveguide with a substrate with at least one flat face allows to easily obtain resonances in TE mode and in mode TM, which greatly improves the sharpness of the resonance generated.
    [0042] To inject the vertical or horizontal polarized electromagnetic radiation into the substrate, you can use a horizontally or vertically oriented polarizing glass, or even a polarization controller that regulates both orientations. In this way, the resonances in TE mode and in TM mode are achieved, greatly improving the sharpness of the resonance generated, and in a much simpler way than by known systems based on in-line polarizer on fiber and the fiber polarization. Furthermore, in the case of known fiber systems, it is necessary to regulate the polarization every Once a new fiber is introduced, since the birefringence of each fiber changes, to which it should be added that the polarization control must be done manually due to the greater complexity of the fiber polarization system. And there is also the problem that the fibers required are singlemode and therefore have a defined cut-off wavelength that limits the range of wavelengths where the sensor system operates.
    [0044] In a variant embodiment, the at least one external element being an analyte to be analyzed, the method comprises receiving the electromagnetic radiation after passing it through the waveguide to characterize the analyte or analytes. In this way, once the sensor system is available to perform the procedure, to analyze other analytes it will be enough to replace the waveguide with new ones that incorporate other analytes, each of which has a much lower price than high-cost fibers which are used in fiber systems with polarization known in the state of the art. There is an option to opt for conventional fibers, but in this case the polarization cannot be controlled, which prevents the clear visualization of the first resonance and therefore the sensitivity worsens dramatically when compared to the polarized system (F. Chiavaioli et al . Anal. Chem. Soc. Sensors, 3: 936-943, 2018) and makes it unattractive for commercial use.
    [0046] The interest in affecting a lateral face of the waveguide substrate lies in the fact that the resonances originated by modes close to the cut condition are shown in a sharper way with this type of incidence. Furthermore, by controlling the polarization of the incident light, resonances can be generated in TE and TM mode. The resonances obtained with this technique can be tuned so that they appear, depending on the thickness of the film, in different positions of the electromagnetic spectrum, which allows this procedure to be used with very varied light sources and detectors. Depending on the movement of the resonances, the refractive index of the external medium, the film index over the entire spectral range analyzed, the thickness of the deposited film, or chemical or biological compounds that modify the properties may be detected, among other variables. of the deposited film.
    [0048] In a variant embodiment, the substrate being a sheet comprising two flat faces parallel to each other, each provided with a film between the substrate and the respective external element, and each external element being an analyte to be analyzed, the method comprises receiving the radiation electromagnetic after passing through the waveguide to characterize the analytes. To this we must add the possibility of even depositing more than one material in each expensive, which could still generate more resonances, making it a multi-parameter device.
    [0050] In a sensor system based on this procedure, once the sensor system is available, it will be enough to replace the sensor waveguide with a new one to analyze different analytes previously incorporated into the waveguide, each of which has a very low price. inferior to the high-cost fibers used in polarized fiber systems. There is an option to opt for conventional fibers, but in this case the polarization cannot be controlled, which prevents the clear visualization of the first resonance and therefore the sensitivity worsens dramatically when compared to the polarized system (F. Chiavaioli et al . Anal. Chem. Soc. Sensors, 3: 936-943, 2018) and makes it unattractive for commercial use.
    [0052] In a variant embodiment, the method further comprises previously preparing the waveguide, progressively depositing a film on a flat face of the substrate while detecting resonances in TE and / or TM modes generated when interacting directed vertical or horizontal polarized electromagnetic radiation towards the substrate in a direction essentially parallel to the flat face to determine the thickness of the film as a function of resonances in TE and / or target TM modes. As for the deposition of the resonance generating film, the process on a flat substrate is easier than on one with a circular geometry, as is the case with fiber optics. In addition, due to the geometry of the flat waveguide, a different material can be deposited on each of the two surfaces with the largest surface area of the substrate, so that a single substrate can be converted into a sensor with at least two different resonances. , which will become four if we control the obtaining of TE and TM resonances through polarization. On the contrary, in the case of SPRs in Kretschmann configuration, due to the fact that one face of the flat waveguide is covered with a prism, only one film can be deposited and also only resonance can be excited in TM mode , whereby one resonance is obtained for every four that are achieved with the method and system of the present invention.
    [0054] It is also envisaged to be able to obtain a reference or target signal by means of a flat waveguide without depositing, it may even be a non-deposited region of the same flat waveguide where the thin film or films have been deposited.
    [0055] Also disclosed is a waveguide to generate modes close to the cut condition that can be used in the procedure described above and that presents a substrate with at least one flat face provided with at least one film between the substrate and a respective external element, which is characterized in essence because the film or films are made of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and the absolute value of the real part of the permittivity of the film greater than the absolute values of the real part of the permittivity of the substrate and of the real part of the permittivity of the external element.
    [0057] In a variant embodiment, the waveguide substrate is a sheet comprising two flat faces parallel to each other, each provided with at least one film between the substrate and its respective external element, the films being of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and the absolute value of the real part of the permittivity of the film being greater than the absolute values of the real part of the permittivity of the substrate and the real part of the permittivity of the respective external element.
    [0059] In a variant embodiment, the waveguide comprises a plurality of stacked films, allowing the sensitivity of the resonance to be increased, the surface to be biofunctionalized, or to be sensitive to a certain parameter to be detected.
    [0061] In a variant embodiment, at least one waveguide film is in the form of strips parallel to each other that extend on the face of the substrate in a longitudinal or transverse direction, so as to regulate the resonances in TE mode and TM are tuned to the same wavelength, thus improving the depth of the resonance peak without the use of a polarizer, and ensuring that grating can make resonance even with materials without an imaginary part.
    [0063] In a variant embodiment, the waveguide substrate is a microscope slide or cover, allowing waveguides to be manufactured at low cost.
    [0065] In a variant embodiment, the waveguide film or films are made of a metal oxide or a polymer, preferably being a metal oxide of an element chosen from zinc, indium, gallium, tin, iridium, cadmium, yttrium, scandium , nickel, copper, or alloys, doped or binary, ternary or quaternary combinations of the oxides of the previous elements among themselves, with other elements such as fluorine, copper, gallium, magnesium, calcium, strontium or aluminum or combinations of the latter among them; or of polymers chosen from poly (vinylpyrrolidone), poly (vinyl alcohol), polyacrylamide, polyacrylic acid, polystyrene sulfate, polyaniline sulfate, poly (thiophene-3-acetic acid), polyaniline, polypyrrole, poly (3-hexyl thiophene), poly ( 3,4-ethylenedioxythiophene) and poly (dimethyl ammonium dichloride), being materials in which the real part of its permittivity is positive and its absolute value is greater than the absolute value of its imaginary part and greater than the real part of the permittivity. of the dielectric surrounding the thin film and capable of producing at least one mode close to the shear condition.
    [0067] Since the film is made of a material in which the real part of its permittivity is positive and its absolute value is greater than the absolute value of its imaginary part and greater than the real part of the permittivity of the dielectric or medium or external element surrounding the thin film and capable of producing at least one mode close to the cutting condition, the most suitable materials are polymers and metal oxides, when for SPR the suitable materials are metals. Furthermore, it has recently been shown that when the external index of refraction, for example, said medium or external element is air, is slightly higher than that of the substrate, an increase in sensitivity occurs that may allow the device to reach more than one million of nanometers per unit of refractive index (A. Ozcariz, CR Zamarreño, P. Zubiate & FJ Arregui, Sci. Rep., 7: 10280, 2017). However, the previous case works only for the region near the silica index, the material most used to make optical fibers. Being able to adapt the substrate material for suitable indices to specific applications, such as aqueous media, for example, implies a very high increase in the complexity of manufacturing the appropriate optical fiber. Instead, there are flat waveguides of much more varied materials, making it easier to tune the sensitivity of the sensing device.
    [0069] A system based on the generation of modes close to the cutting condition is also disclosed, which comprises a waveguide of the previously described and emitting means adapted to inject vertical or horizontal polarized electromagnetic radiation into the substrate of the guide- wave in a direction essentially parallel to the flat face; and receiving means adapted to receive electromagnetic radiation after passing through the waveguide. In this case, the sensor based on lateral incidence on a flat waveguide with geometry such as that of a microscope slide, sheet or substrate comprises: - a flat waveguide through which the light received by one of its faces is transmitted sides and at least one thin film located on one of the two largest surfaces of the guide - a source of broad spectrum electromagnetic radiation whose output is oriented to affect one of the lateral faces of the plane waveguide, previously passing through a polarization system that controls the generation of the TE and TM resonance.
    [0070] - A detector device for the measurement of the radiation that comes out from the opposite face of the plane waveguide, so that it can be determined, depending on the wavelength of the resonance or resonances, the parameter or parameters to be detected by the sensor.
    [0072] The electromagnetic radiation source, which may be a light source, may consist of an LED, an array of LEDS, a semiconductor laser, or a halogen lamp. The electromagnetic radiation detection system, which can be a light detection system, will be adapted to detect the wavelengths produced by the chosen source. The detector device preferably comprises a spectrometer although an interrogator can also be used.
    [0074] In a variant embodiment, the waveguide comprising at least one analyte, the receiving means are adapted to receive electromagnetic radiation after passing through the waveguide that includes the interaction of resonances in TE and / or TM modes with the analyte and characterize the analyte (s) so that analysis of the analyte (s) can be performed.
    [0076] In a variant embodiment based on direct transmission, the emitting means and the receiving means are arranged at opposite ends of the waveguide, where the radiation source is focused towards one of the lateral faces of the substrate and the radiation propagates through of the substrate until it comes out on the opposite side, next to which the detector is positioned, or based on reflection, where the opposite side of the face is covered with a mirror (preferably gold, silver, chrome, aluminum or platinum) where the light falls, so that the light is reflected and returns it causes the reflection of the light until it leaves the face where the light falls, in which the receiver is placed at the same time as the source. In both configurations (transmission and reflection), the thin film or films can be placed on one or both of the larger surfaces of the substrate
    [0078] In a reflection-based variant embodiment, the waveguide is provided with a specular layer at one end of the waveguide and the emitting and receiving means are arranged at the other opposite end of the waveguide, together with optocoupler means.
    [0079] In an embodiment variant, the system further comprises means for changing the waveguide so as to allow the waveguide to be replaced in the system, allowing serial analysis to be carried out. It is also envisaged that the system further comprises means for cleaning the waveguide, allowing serial analysis to be carried out simply by cleaning and replacing the analyte in the waveguide, which could also be carried out by means of replacing the analyte or analytes of the waveguide.
    [0081] Therefore, the system of the present invention can be used both as an optical filter, expanding and attenuating wavelengths of light or electromagnetic radiation that passes through the waveguide, and as an optical sensor, characterizing the analyte or analytes that can be placed in the waveguide.
    [0083] Although the described plane waveguide-based configuration may appear to be similar to that of the SPR sensors in Kretschmann configuration, it is worth emphasizing the differences between the LMRs and the SPRs:
    [0084] - The MRLs are based on the excitation of modes close to the cut-off wavelength and not on the excitation of superficial plasmons, so that a resonance can be generated in TE mode and another in TM mode.
    [0085] - The possibility of obtaining resonances in TE and TM mode allows us to get an idea of the refractive index of the thin film film as a function of the separation between the central wavelengths of each resonance, since this increases as the index increases ( I. Del Villar et al. J. Opt., 12 (9), 095503, 2010)
    [0086] - The two TE and TM resonances of the MRLs can be obtained multiple times, which is not possible with SPRs. On the other hand, the multiple resonances will each present different sensitivities and bandwidths, which can be used for different purposes and for different applications.
    [0087] - LMR resonances are generated with different materials from those used to generate SPRs (to excite a surface plasmon and obtain an SPR resonance, the real part of the permittivity of the thin film material must be negative and its absolute value is greater than the absolute value of its imaginary part and greater than the absolute value of the real part of the permittivity of the waveguide and of the dielectric surrounding the thin film. Instead, to excite a mode close to the condition of cut and generate an LMR resonance, the real part of the permittivity of the thin film material is required to be positive and its absolute value greater than that of its imaginary part and also greater than the absolute value of the real part of the permittivity of the waveguide and the dielectric that surrounds the thin film). These conditions result in that the typical materials that generate SPRs are metals, while polymers and metal oxides are more suitable for obtaining MRLs.
    [0088] - The resonances in a flat waveguide are much sharper than with the SPRs, since the SPRs are oriented to work with non-grazing angles of incidence and for which an optical prism that couples the light is required. In contrast, MRLs are best excited on a flat waveguide, since the optimal angles of incidence are close to 90 °.
    [0090] In short, the set of possibilities that the present invention allows, compared to the systems known in the state of the art, is very wide, which will allow detecting more than one parameter at the same time.
    [0092] Brief description of the drawings
    [0093] To complement the description that is being made and in order to facilitate the understanding of the characteristics of the invention, a set of drawings is attached to the present descriptive memory in which, by way of illustration and not limitation, the following has been represented:
    [0095] Fig. 1a shows a side view of a waveguide according to the present invention; Fig. 1b shows a front view of the waveguide of Fig. 1a;
    [0096] Fig. 2 shows a direct transmission based system incorporating the waveguide of Figs. 1a and 1b;
    [0097] Fig. 3 shows spectra presenting attenuations for different wavelengths and polarizations in a waveguide of the present invention in the system of Fig. 2;
    [0098] Fig. 4 shows attenuation spectra (MMR in TM mode) for different refractive indices of the external medium for vertical polarization in a waveguide of the present invention in the system of Fig. 2;
    [0099] Fig. 5 shows attenuation spectra (MRLs in TE mode) for different refractive indices of the external medium for horizontal polarization in a waveguide of the present invention in the system of Fig. 2;
    [0100] Fig. 6 presents the correspondence between the wavelength of the resonance peak and the relative humidity in a waveguide of the present invention in a waveguide of the present invention in the system of Fig. 2;
    [0101] Fig. 7a shows a side view of another waveguide according to the present invention; Fig. 7b shows a front view of the waveguide of Fig. 7a;
    [0102] Fig. 8 shows a reflection based system incorporating the waveguide of Figs. 7a and 7b;
    [0103] Figs. 9a and 9b show a side and front view of another waveguide according to the present invention;
    [0104] Figs. 10a and 10b show a side and front view of another waveguide according to the present invention;
    [0105] Figs. 11a and 11b show a side and front view of another waveguide according to the present invention; and
    [0106] Figs. 12a and 12b show a side and front view of another waveguide according to the present invention.
    [0108] Detailed description of the drawings
    [0109] Figs. 1a and 1b present a waveguide 1 according to the present invention to generate modes close to the LMR cut condition. As can be seen, the waveguide 1 has a substrate 2 with at least one face 3a, 3b, in this case two flat faces 3a, 3b, each provided with a film 4a, 4b between the substrate 2 and a respective element external 5a, 5b, in which the films 4a, 4b are of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and the absolute value of the real part of the permittivity of the film greater than the absolute values of the real part of the permittivity of the substrate 2 and of the real part of the permittivity of the external element 5a, 5b, so that when injecting electromagnetic radiation, as will be seen later, modes close to the cut-off condition are generated when the electromagnetic radiation interacts with waveguide 1. As can be seen, in waveguide 1 presented in Figs. 1a and 1b the first external element 5a, arranged adjacent to the first face 3a, could be an analyte, that is, a component that can be analyzed by detecting the modes close to the characteristic cut-off condition, generated by also interacting the electromagnetic radiation with the first external element 5a. In this case, the second external element 5b, adjacent to the second face 3b, could be directly the air or the medium in which the waveguide 1 was placed. The waveguide is also expected to be devoid of analytes, it is that is, the external elements 5a, 5b are the external medium of the waveguide. This configuration would be especially useful to use the waveguide as an analog frequency filter, for example as an optical filter, so that the frequencies of the electromagnetic radiation passing through them are attenuated and amplified depending on the configuration of the or waveguide 1 movies 4a, 4b.
    [0110] Naturally, when waveguide 1 is provided with an analyte it can also be used as a filter.
    [0112] In the embodiment presented in Figs. 1a and 1b, it can be seen that the substrate 2 is a sheet, preferably thin, such as a microscope slide or cover, comprising two flat faces 3a, 3b parallel to each other, each provided with at least one film 4a, 4b, in this case a first film 4a on the first face 3a and a second film 4b on the second face 3b, between the substrate 2 and its respective external element 5a, 5b, these films 5a, 5b being of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and the absolute value of the real part of the permittivity of the film 4a, 4b being greater than the absolute values of the real part of the permittivity of the substrate 2 and of the real part of the permittivity of the respective external element 5a, 5b. Therefore, the materials of the films 4a, 4b must be chosen appropriately based on the external elements 5a, 5b, whether these are analytes or the external medium in which the waveguide 1 will be placed. It will therefore be necessary to generate the modes close to the cut condition in waveguide 1, that the films 4a, 4b are of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and the absolute value of the real part of the permittivity of the film 4a, 4b being greater than the absolute values of the real part of the permittivity of the substrate 2 and of the real part of the permittivity of the external element 5a, 5b. Typically, the materials in films 4a and 4b will be a metal oxide or a polymer, for example being a metal oxide of an element chosen from zinc, indium, gallium, tin, iridium, cadmium, yttrium, scandium, nickel, copper , or binary, ternary or quaternary alloys, dopeds or combinations of the oxides of the previous elements among themselves, with other elements such as fluorine, copper, gallium, magnesium, calcium, strontium or aluminum or combinations of the latter among them; or a polymer chosen from poly (vinylpyrrolidone), poly (vinyl alcohol), polyacrylamide, polyacrylic acid, polystyrene sulfate, polyaniline sulfate, poly (thiophene-3-acetic acid), polyaniline, polypyrrole, poly (3-hexyl thiophene), poly ( 3,4-ethylenedioxythiophene) and poly (dimethyl ammonium dichloride).
    [0114] As a waveguide 1, all commercial microscope slides, usually borosilicate, and also those of other materials whose real part of their refractive index does not exceed that of thin film 4a, 4b, are contemplated. On the other hand, the thickness of the substrate 2 of the waveguide 1 may be as the standard of the microscope slides, 1 mm, or other, since the resonance can be obtained with substrates 2 of different thickness, this being more deep as substrate 2 is narrower. Waveguide 1 will be more sensitive if the refractive index of the external medium in which the experiments are carried out is slightly lower than that of substrate 2 of waveguide 1. In addition, in order to avoid interference in the resonance, they will preferably be placed a series of opaque pieces 9 surrounding the entrance and exit of the light in waveguide 1.
    [0116] Fig. 2 presents a system 100 based on the generation of modes close to the cut-off condition (LMR) according to the present invention comprising a waveguide 1, of the type described above; emitting means 101 adapted to inject vertically or horizontally polarized electromagnetic radiation 6 into the substrate 2 of the waveguide 1 in a direction essentially parallel to the flat face 3a, 3b; and a receiving means 102 adapted to receive and preferably analyze the electromagnetic radiation 6 after passing through the waveguide 1. As the waveguide 1 presented in the system of Fig. 2 comprises at least one analyte 7a, the receiving means 102 are adapted to receive electromagnetic radiation after passing through waveguide 1, which includes the interaction of resonances in TE and / or TM modes with analyte 7a and characterize analyte 7a. Naturally, if the waveguide 1 were provided with two or more analytes 7a, 7b, for example adjacent to each of the different faces 3a, 3b of the substrate, or even more than one analyte adjacent to the same face 3a, 3b of the substrate 2 , the receiving means 102 could be adapted to receive the electromagnetic radiation 6 after passing through the waveguide 1 that includes the interaction of the resonances in TE and / or TM modes with the different analytes 7a, 7b and characterize the analytes 7a, 7b. Therefore, it is contemplated that multiple different analytes 7a, 7b may be available on the same waveguide 1. Analytes 7a, 7b can be gases or liquids. In the case of liquids, it could be a microfluidic sensor, with the volume of the analytes 7a, 7b being in the order of microliters.
    [0118] As can be seen, the system 100 presented in Fig. 2 is based on direct transmission, the emitting means 101 and the receiving means 102 being arranged at opposite ends of the waveguide 1. In addition, it is provided with polarizing means 104 that they allow the electromagnetic radiation 6 to be polarized vertically or horizontally before being injected into the waveguide 1. Naturally, the substrate of the waveguide 1 could alternatively or in addition incorporate polarizing means 104, such as a sheet adjacent to the portion of the substrate 2 where the electromagnetic radiation 6 is injected, so that the electromagnetic radiation 6 is properly polarized upon reaching the substrate. System 100 is also provided with collimating means 105, such as a fiber optics or a lens, arranged to collect electromagnetic radiation 6 after passing through waveguide 1, and directing electromagnetic radiation to receiving means 102 adapted to receive electromagnetic radiation 6 after passing through waveguide. In order to generate the TE resonance, the TM or any intermediate state between the two, the polarizing means 104 can be a device that allows a polarizing crystal to be rotated at will to any desired angle.
    [0120] In this way, the system 100 of Fig. 2 allows a procedure to be carried out to generate modes close to the cut-off condition (MRL) in the waveguide 1 provided with a substrate 2 with at least one flat face 3a, 3b provided with at least one film 4a, 4b placed between the substrate and a respective external element 5a, 5b, the film 4a, 4b being of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the value absolute of the imaginary part, and the absolute value of the real part of the permittivity of the film being greater than the absolute values of the real part of the permittivity of the substrate and of the real part of the permittivity of the respective external element, comprising the method injecting a vertical or horizontal polarized electromagnetic radiation 6 into the substrate 2 of the waveguide 1 in a propagation direction essentially parallel to the plane face, so that resonances are advantageously generated in TE and / or TM modes corresponding to modes close to the cut-off condition when the polarized electromagnetic radiation 6 interacts with the film or films 4a, 4b placed on it; and receiving in receiving means 102 the electromagnetic radiation 6 after passing through the waveguide 1. Thus, in the case that at least one external element 5a, 5b is an analyte 7a, 7b to be analyzed, the method will comprise receiving the electromagnetic radiation 6 after passing through the waveguide to allow characterizing the analyte or analytes 7a, 7b
    [0122] It is envisaged that the waveguide can be prepared in advance by depositing on a flat face 3a, 3b of the substrate 2 progressively a film 4a, 4b while detecting resonances in TE and / or TM modes generated by interacting vertical polarized electromagnetic radiation 6 or horizontally directed towards the substrate in a direction essentially parallel to the flat face to determine the thickness of the film as a function of resonances in TE and / or objective TM modes. In this way it would be possible to tune the waveguide 1 by controlling the deposition and thickness of one, or even more, films 4a, 4b of different materials on the flat faces 3a, 3b. It is further contemplated that films 4a, 4b may have a thickness adapted to generate multiple resonances.
    [0123] Furthermore, it is envisaged that on at least one of the two surfaces 3a, 3b with the largest surface area of the waveguide 1, preferably on the film or films 4a, 4b, various analyte-like materials 7a, 7b can be deposited, which They can be manufactured using techniques such as direct laser engraving, photolithography, etc., so that by moving waveguide 1 in a direction perpendicular to the light propagation, the resonance corresponding to each of the materials can be monitored. It is also foreseen that on one of the faces 3a, 3b with the largest surface area of the substrate 2 of the waveguide 1, a region is left without depositing as a reference signal
    [0125] Naturally, the waveguide 1 can have a single flat face 3a or two flat faces 3a, 3b or even more flat faces when, for example, substrate 2 is prism-shaped, for example, three flat faces if substrate 2 is shaped triangular prism, or even more expensive using prisms of other geometric shapes: square, pentagonal, etc. Naturally, it is envisaged that each face may have none, one or even more stacked films, which together with the external elements 5a, 5b that can be both analytes 7a, 7b and the external medium in which the waveguide 1 is placed, will determine the modes near cut-off condition (MRL) that will be generated by injecting electromagnetic radiation 6 into waveguide 1.
    [0127] Previously, the phenomenon of generation of modes near the cut-off condition (MRL) had been observed in fiber optics and in the Kretschmann configuration, but never through lateral incidence on a plane waveguide. Compared to the Kretschmann configuration, the great advantage is the elimination of the optical prism, which simplifies the system and enables the deposition of a different film on each of the two faces with the largest surface area of the waveguide, enabling more than a sensor on the same device. Likewise, not only will the platform be excited with TM mode polarized light, but a polarization system will be included that allows regulation of the excitation of both TE and TM mode resonances (Figure 3 shows experimental data on the spectra obtained with light polarization nonpolarized, vertically and horizontally polarized).
    [0129] On the other hand, compared to the optical fiber, the lateral incidence on the flat waveguide implies the elimination of the joints of the hoses to the sensor fiber section, which results in greater simplicity when implementing each experiment, since it is enough with exchanging the waveguide for a new one, and also the system is less fragile. In addition, polarization control is much easier, since it is based only on the use of a polarizing glass, whose orientation can even be adjusted automatically with a rotator. In fiber, on the contrary, either special high-cost fibers are used in which a complex manually controlled polarization system is applied, or conventional fiber is chosen where polarization is not possible and therefore the resonances are monitored worse, which results in a much lower sensitivity of the device (F. Chiavaioli et al. Anal. Chem. Soc. Sensors, 3: 936-943, 2018).
    [0131] The resonances will be generated in transmission or in reflection, and their position in the spectrum can be tuned in the ultraviolet, visible or near infrared, medium and far range, or even up to the terahertz, since the MRLs are generated in a very broad spectrum (I. Del Villar et al. Appl. Opt., 51: 4298: 4307, 2012), which will allow measurements of chemical, biomedical or environmental parameters. On the other hand, the sensor of the invention can be used in the same applications as SPR sensors and fiber-based LMR sensors. The device is highly sensitive to changes in the surrounding environment, so chemical, environmental, biochemical sensors, etc. can be developed, both in the event that the thin film is sensitive to the desired parameter or by adding a or several layers that are sensitive to the parameter to detect. Sensor devices can also be developed based on the variation of the index of the external medium (refractometers), based on the variation of the properties of the film, or even optical filters.
    [0133] The ability to generate resonances with lateral incidence is due to the fact that resonances based on modes close to the cut are generated through angles of incidence close to 90 ° (I. Del Villar, V. Torres, M. Beruete, Opt. Lett. 40 : 4739-4742, 2015). Depending on the thickness of the thin film responsible for generating the resonance, its position in the spectrum can be tuned, and it may even be possible for more than one resonance to be generated, each of which is located at different wavelengths. Starting from longer wavelengths towards shorter wavelengths, the first resonance will be the one with the highest sensitivity. However, it is also the widest, hence the polarization system that allows the TE resonance to be separated from the TM, is essential to minimize the bandwidth and thus be able to fully exploit the characteristics of the sensor. On the other hand, having several resonances will allow obtaining multiple simultaneous measurements, which will improve the errors produced by interference and noise.
    [0135] The central wavelength of the resonance will undergo variations depending on the parameters that are detected, leading to large displacements such as those observed in Figures 7 and 8 for the external refractive index and humidity respectively.
    [0137] In summary, the resonance properties of near-cut modes are still maintained in fiber optic devices (ultraviolet, visible, or infrared resonance tuning by thin film thickness, eliminating the need to introduce light polarized, control of the sensitivity and the width of the resonance depending on the order of the resonance on which one works), and others such as the simplicity of using a flat waveguide are added, since a simple microscope slide, the possibility of depositing different materials on the two faces with the largest surface area and generating resonances in TE and TM mode and each one multiple times, as well as the ability to deposit diffraction gratings on different axes on a flat substrate , which will even allow to join the resonance in TE mode and in TM mode (I. Del Villar et al. Opt Express, 25: 10743-10756, 2017) or also obtain the resonance with a matte lossless rial.
    [0139] In this way, the system 100 uses two elements to couple light to the waveguide 1, that is, inject electromagnetic radiation 6 into the flat waveguide 1. The first is a multi-wavelength, "broad spectrum", light source emitting means 101, where "broad spectrum" means a minimum of two wavelengths, although a range wide enough to encompass is desirable. the resonance spectrum of the sample, such as a white light source or black body radiation. The second element incorporates collimating means 105 for collimating the light and polarizing means 104 that allow TE or TM resonances to be excited depending on the orientation of the polarizer (horizontal or vertical).
    [0141] As illustrated in Fig. 2, it is observed that the optical power injected by the emitting means 101 at one end of the waveguide 1 travels through it, while interacting with the thin film or films 4a, 4b and external elements 5a, 5b, which can be both one or more analytes 7a, 7b and the external medium that surrounds the waveguide 1, and reaches the receiving means 102 or detector device, either directly in the case of the configuration in transmission or once reflected by specular layer 8 in the case of the reflection configuration
    [0143] The optical power reaching the detector means 102 or detector device will therefore be advantageously a function of the refractive index of the external element 5a, 5b, which can be the external medium surrounding the waveguide 1, in contact with the thin film or films 4a, 4b, which absorb part of the guided light or electromagnetic radiation 6 by waveguide 1.
    [0145] In this way, by measuring the spectrum at the output of waveguide 1, the refractive index of each of the samples or analytes 7a, 7b that come into contact with the film or films 4a, 4b deposited in waveguide 1, or the deposition of any chemical, molecule or bacteria that adheres to thin film 4a, 4b can also be determined.
    [0147] In general, the waveguides 1 and systems and procedures described can be used in multiple applications: refractometers, optical filters, and in the chemical or biochemical field, for detection of species that are present in solutions in the liquid or gas state. Another very interesting application that is based on the fact of generating TE and TM resonances by controlling the polarization of the incident light is that, because the wavelength of each resonance is different, if the thickness increases of the deposited film the wavelength of the TE and TM resonance is characterized, as well as its separation, the thickness of the film can be obtained as well as the refractive index of the same in all the wavelengths that cover the light source and detector.
    [0149] In the system 100 of the present invention, any device capable of detecting the intensity of all or part of the wavelengths that come out through the waveguide 1 may be used as receiver means 102 or detectors. As an example of means receivers 102 a spectrometer capable of measuring the intensity of light as a function of wavelength can be used. Also an interrogator or intensity detector located at the resonance wavelength are good options.
    [0151] Next, an embodiment of a system 100 of the present invention using a waveguide 1 of the present invention, based on direct transmission mounted on a system as previously described in Fig. 2, is described.
    [0153] In this case, the emitting means 101 as a light source correspond to a DH-2000-H halogen light lamp (Avantes Inc.), substrate 2 of waveguide 1 is a soda lime glass microscope slide with grounded edges. He holder size is 75x26x1 mm, orienting the longest side in a transverse direction to the light propagation direction. This slide has a refractive index between 1,538 and 1,520, which corresponds to a permittivity between 2.3654 and 2.3104, in the wavelength range between 400 and 700 nm, according to (M. Rubin, "Optical properties of soda lime silica glasses, ”Sol. Energy Mater., vol. 12, pp. 275-288, 1985).
    [0155] A thin 60nm film 4a of indium tin oxide (ITO) was deposited on a first face 3a of substrate 2, resulting in the sensitive area of waveguide 1. Its index was measured on a Horiba ellipsometer ellipsometer UVISEL and resulted in a refractive index between 1.9 + 0.05i and 1.8 + 0.0003i, corresponding permittivity between 3.6075 + 0.19i and 3.24 + 0.0011i, in the range between 400 and 700 nm. No film was deposited on the second side 3b in this case.
    [0157] In this embodiment, analyte was not used, but the external element was directly the external medium. In one case, the external element used was water, which according to the reference (M. Daimon and A. Masumura. Measurement of the refractive index of distilled water from the near-infrared region to the ultraviolet region, Appl. Opt. 46 , 3811-3820 (2007)) has a refractive index between 1,343 and 1,330 (permittivity between 1.8036 and 1.7689) in the wavelength range between 400 and 700 nm. Air was also used as an external element, with refractive index 1 and permittivity 1.
    [0159] With all these values, the MRL conditions are met in the entire range between 400 and 700 nm, that is, the film is made of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the value. absolute of the imaginary part, and the absolute value of the real part of the permittivity of the film being greater than the absolute values of the real part of the permittivity of the substrate and of the real part of the permittivity of the external element.
    [0161] This process was performed using a K675XD sputtering equipment from Quorum Technologies, Ltd., at a partial pressure of 8x10-2 mbar and a current intensity of 150 mA. The electromagnetic radiation 6 from the emitting media 101, which is a white light source, was connected to a 200 ^ m diameter VIS / NIR optical fiber from Ocean Optics, at the exit of which a lens was directed to direct the light beam towards one of the lateral faces of the holder, which is 26 mm long, and a polarizing glass is placed between the collimating lens of the collimating means 105 and the holder, as polarizing means 104 oriented horizontally. After the light passes through the holder, it passes through a lens that collimates the light, as collimating means 105, towards the entrance of another 200 ^ m diameter VIS / NIR fiber from Ocean Optics, which was connected by the other end to a USB4000 spectrometer, which allows monitoring a range of wavelengths between 200 and 850 nm using an SMA connection and in turn connected to a computer for the acquisition of spectra.
    [0163] Fig. 3 presents the spectral responses of system 100 when incident light without polarizing, horizontally polarized and vertically polarized, while Fig. 4 presents the spectral responses of system 100 as a function of the refractive index of different external elements, of which its permittivity is derived, when vertically polarized light influences and Fig. 5 presents the spectral responses as a function of the refractive index of different external elements, from which its permittivity is derived, when horizontally polarized light influences when mounting the waveguide 1 in a system 100 like the one previously presented in Fig. 2.
    [0165] This system 100 was introduced into an ACS CH 250 climatic chamber (from Angelantoni Industries) and subjected to humidity cycles between 30 and 90%. As the humidity increases, there is an increase in the resonance wavelength, as can be expected since the external index, due to the accumulation of water film, increases.
    [0167] In Fig. 6, the correspondence between the wavelength of the resonance peak and the relative humidity is presented. Specifically, a spectral variation of 70 nm is observed for the analyzed humidity range. This displacement is comparable to that obtained with ITO on optical fiber as a humidity sensor (M Hernáez et al 2009 J. Phys .: Conf. Ser. 178012019), which demonstrates the capacity of sensors based on lateral incidence on plane waveguide to behave like fiber optics, with all the advantages that this technology presents in terms of simplicity, robustness and the ability to have two sides to deposit sensitive materials, thereby doubling the possibilities offered by devices based on fiber optics and also Kretschmann configuration based devices, where it can also be deposited only on one side of the microscope slide.
    [0169] Figs. 7a and 7b present another embodiment of waveguide 1 of the present invention, analogous to that previously described in Figs. 1a and 1b, but which is especially suitable for use in a reflection-based system 100 such as that presented in Fig. 8, being provided with a specular layer 8 at one end of the substrate 2. In this case, the waveguide 1, in the same way as the guide- Wave 1 previously described, also comprises a substrate 2 with at least one flat face 3a, 3b provided with at least one film 4a, 4b between the substrate and a respective external element 5a, 5b, the film or films 4a, 4b being of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and the absolute value of the real part of the permittivity of the film being greater than the absolute values of the real part of the permittivity of the substrate and of the real part of the permittivity of the external element 5a, 5b.
    [0171] As can be seen in Fig. 8, the system 100 that incorporates the waveguide 1 previously described in Figs. 7a and 7b allows to form a system 100 analogous to the one previously presented in Fig. 2, although in this case system 100 is based on reflection, so that waveguide 1 is provided with a specular layer 9 at one end of the waveguide 1 and the emitting means 101 and the receiving means 102 are arranged on the other opposite end of the waveguide 1 together with optocoupler means 103, which could incorporate the polarizing means 104 of the electromagnetic radiation 6. It is also provided that the optocoupler means 103 perform the function of collimating means 105 by collecting the electromagnetic radiation 6 after passing through the waveguide 1 and directing the electromagnetic radiation 6 to the receiving means 102 adapted to receive the electromagnetic radiation after passing through the guide -wave 1.
    [0173] In this case, it is necessary that the waveguide 1 be provided with a specular layer 9 located at one of the ends of the waveguide 1, so that it reflects the electromagnetic radiation 6 or light that propagates through it in the reverse direction. Waveguide 1, which may consist of a layer of highly reflective metal, such as gold, silver, or chrome, thick enough to provide adequate reflection. It also requires a polarization control system that at the same time allows the light from the emitting means 101 or source to be bifurcated and the light that is directed to the receiving means 102 or detector.
    [0175] Since it is envisaged that the systems 100 presented above can be used to characterize different analytes, said analytes being able to be previously prepared in different waveguides 1, it is envisaged that the systems 100 may be provided with means for changing or replacing the guide wave 1, so that sequential analyzes can be performed after replacing one waveguide with another, for example using a waveguide loading 1, such as a robotic arm or a rail or ferris wheel system that loads a waveguide that has been previously prepared between the emitting means 101 and the receiving means 102 and arranged in a waveguide bank and remove the waveguides after analysis, thereby automating an analyte analysis sequence. Naturally, the system can even previously prepare each waveguide 1, depositing on its flat faces 3a, 3b of the substrate 2 progressively the film or films 4a, 4b, in the manner described above and even deposit the analyte or analytes 7a, 7b.
    [0177] Naturally, it is also envisaged to be able to replace the analyte 7a, 7b in a waveguide 1 to carry out a series of analyzes in the systems 100 described above without completely changing the waveguide. In this case, it is envisaged that the systems 100 can incorporate a waveguide 1 cleaning means that allows removing an analyte from the waveguide 1, for example by spraying the waveguide 1 with a cleaning liquid, and incorporating later on the waveguide 1 another analyte, thus also allowing to automate an analysis sequence if it is not necessary to discard the waveguide after each analysis.
    [0179] The system and procedure presented in the present invention can be used as an optical sensor for the detection of a sample or analyte and can be carried out, by placing the sample to be measured or analyte 7a, 7b on one of the thin films 5a, 5b that can be deposited on one of the two surfaces 3a, 3b with the largest surface area of the substrate 2 of the waveguide 1, in the part that is not covered by the opaque parts 9 that prevent light not guided by the Waveguide 1 interferes with measurements. Another thin film can be deposited on the other face with a larger surface area of the substrate 2 of the waveguide 1 and another sample can be placed around it or air can simply be the means of detection.
    [0181] It is further provided that waveguide 1 can comprise a plurality of stacked films 4a, 4b, as illustrated in Figs. 9a and 9b, so that the waveguide 1 can be provided with several films stacked on one or more faces, and can be used in both a transmission and reflection-based system 100, in order to fulfill various functions such as increasing the resonance sensitivity, biofunctionalize the surface, or be sensitive to a certain parameter to detect. An example is applications in biosensors or screening, where thin film 4a, 4b can be coated with one or more additional layers including immobilized compounds, specifically sensitive to the species to be detected (eg enzymes and coenzymes, antigens and antibodies , etc.). It is also anticipated that on the thin film (s) 4a, 4b of material At least one additional layer sensitive to the analyte or parameter to be detected or that serves to increase the sensitivity of the resonance can be deposited.
    [0183] In turn, the thin film (s) 4a, 4b covering the waveguide 1 can be nanostructured, i.e. create a periodic pattern both on the axis transverse to the direction of radiation propagation through the waveguide for example, at least one film 4a, 4b may be in the form of strips parallel to each other extending over the face 3a, 3b of the substrate 2 in a longitudinal direction, as illustrated in Figs. 10a and 10b, as in the axis coinciding with the waveguide propagation direction, or a transverse direction, as illustrated in Figs. 11a, 11b. In the first case, it is possible to regulate that the resonance in TE and TM mode is tuned to the same wavelength, thus improving the depth of the resonance peak (I. Del Villar et al. Opt. Express, 25 : 10743-10756, 2017), while in the second case, grating can cause resonance to be generated even with materials without an imaginary part. What is more, other geometries can be used for thin films such as meta-surfaces.
    [0185] Naturally, many other combinations of the technical characteristics described above are also contemplated for each of the waveguides 1 presented, which can be used in the systems and procedures described above. For example, Figs. 12a and 12b present another waveguide 1 according to the present invention that on a first face 3a of the substrate 2 has a set of stacked films 4a and a first analyte 7a while the second face 3b of the substrate 2 has a single second stacked film 4b and a second analyte 7b. Naturally, it is contemplated that one of the faces was devoid of films or analytes, or even both faces, the waveguide acting only as a result of the generation of modes near cut condition (MRL) between substrate 2 and the medium external, for example as an optical filter. It is also envisaged that on one of the two faces 3a, 3b with the largest surface area of substrate 2 of waveguide 1 a very high reflective or specular material is deposited or even that substrate 2 is directly supported by a layer that act as a support for waveguide 1, so it can only be deposited on one of the faces of support 2 to produce the phenomenon of resonance
    权利要求:
    Claims (20)
    [1]
    1. - Procedure to generate modes close to the cutting condition (MRL) in a waveguide (1) provided with a substrate (2) with at least one flat face (3a, 3b) provided with at least one film (4a, 4b ) placed between the substrate and a respective external element (5a, 5b), the film being a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and the absolute value of the real part of the permittivity of the film being greater than the absolute values of the real part of the permittivity of the substrate and of the real part of the permittivity of the respective external element, the procedure comprising:
    - injecting a vertical or horizontal polarized electromagnetic radiation (6) into the substrate in a direction essentially parallel to the flat face, so that resonances in TE and / or TM modes corresponding to modes close to the cutting condition are generated when the polarized electromagnetic radiation with the film or films placed on it; and
    - receive electromagnetic radiation after passing through the waveguide.
    [2]
    2. - Method according to any one of the preceding claims, characterized in that, being at least one external element (5a, 5b) an analyte (7a, 7b) to be analyzed, the method comprises receiving electromagnetic radiation after passing through the guide- wave to characterize the analyte or analytes.
    [3]
    3. - Procedure according to the preceding claim, characterized in that, the substrate (2) being a sheet comprising two flat faces (3a, 3b) parallel to each other provided with a film (4a, 4b) between the substrate, and being each external element (5a, 5b) and an analyte (7a, 7b) to be analyzed, the method comprises receiving the electromagnetic radiation after passing through the waveguide to characterize the analytes.
    [4]
    4. - Process according to any one of the preceding claims, characterized in that it further comprises previously preparing the waveguide (1), depositing on a flat face (3a, 3b) of the substrate (2) progressively a film (4a, 4b) while resonances in TE and / or TM modes generated by interacting vertical or horizontal polarized electromagnetic radiation (6) directed towards the substrate in an essentially one direction are detected parallel to the flat face to determine the thickness of the film as a function of resonances in TE and / or target TM modes.
    [5]
    5. - Waveguide (1) to generate modes close to the cut condition (MRL) that comprises a substrate (2) with at least one flat face (3a, 3b) provided with at least one film (4a, 4b) between the substrate and a respective external element (5a, 5b), characterized in that the film or films are made of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part , and the absolute value of the real part of the permittivity of the film being greater than the absolute values of the real part of the permittivity of the substrate and of the real part of the permittivity of the external element.
    [6]
    6. - Waveguide (1) according to the preceding claim, characterized in that the substrate (2) is a sheet comprising two flat faces (3a, 3b) parallel to each other, each provided with at least one film (4a, 4b ) between the substrate and its respective external element (5a, 5b), being the films of a material with a permittivity whose real part is positive and whose absolute value of the real part is greater than the absolute value of the imaginary part, and being the absolute value of the real part of the film permittivity greater than the absolute values of the real part of the substrate permittivity and of the real part of the permittivity of the respective external element.
    [7]
    7. - Waveguide (1) according to any one of claims 5 to 6, characterized in that it comprises a plurality of stacked films (4a, 4b).
    [8]
    8. - Waveguide (1) according to any one of claims 5 to 7, characterized in that at least one film (4a, 4b) is in the form of strips parallel to each other that extend over the face (3a, 3b) of the substrate (2) in a longitudinal or transverse direction.
    [9]
    9. - Waveguide (1) according to any one of claims 5 to 8, characterized in that the substrate (2) is a microscope holder or covers.
    [10]
    10. - Waveguide (1) according to any one of claims 5 to 9, characterized in that the film (s) (4a, 4b) are made of a metal oxide or a polymer.
    [11]
    11. - Waveguide (1) according to the preceding claim, characterized in that the film (s) (4a, 4b) are made of a metal oxide of an element chosen from zinc, indium, gallium, tin, iridium, cadmium, yttrium, scandium , nickel, copper, or alloys, doped or binary, ternary or quaternary combinations of the oxides of the previous elements among themselves, with other elements such as fluorine, copper, gallium, magnesium, calcium, strontium or aluminum or combinations of the latter between they; or of polymers chosen from poly (vinylpyrrolidone), poly (vinyl alcohol), polyacrylamide, polyacrylic acid, polystyrene sulfate, polyaniline sulfate, poly (thiophene-3-acetic acid), polyaniline, polypyrrole, poly (3-hexyl thiophene), poly ( 3,4-ethylenedioxythiophene) and poly (dimethyl ammonium dichloride).
    [12]
    12. - System (100) based on the generation of modes close to the cut-off condition (LMR) comprising:
    - a waveguide (1) according to any one of claims 5 to 11;
    - emitting means (101) adapted to inject vertical or horizontal polarized electromagnetic radiation into the waveguide substrate in a direction essentially parallel to the flat face; and
    - receiver means (102) adapted to receive electromagnetic radiation after passing through the waveguide.
    [13]
    13. - System (100) according to the preceding claim, characterized in that, the waveguide (1) comprising at least one analyte (7a, 7b), the receiving means (102) are adapted to receive electromagnetic radiation after passing through the waveguide that includes the interaction of resonances in TE and / or TM modes with the analyte and characterize the analyte or analytes.
    [14]
    14. - System (100) according to any one of claims 12 to 13, characterized in that it is based on direct transmission, the emitting means (101) and the receiving means (102) being arranged at opposite ends of the waveguide (1 ).
    [15]
    15. - System (100) according to any one of claims 12 to 13, characterized in that it is based on reflection, the waveguide (1) being provided with a specular layer (9) at one end of the waveguide and being the emitting means (101) and the receiving means (102) arranged at the other opposite end of the waveguide together with optocoupler means (103).
    [16]
    16. System (100) according to any one of claims 12 to 15, characterized in that it further comprises means for changing the waveguide (1).
    [17]
    17.- System (100) according to any one of claims 12 to 16, characterized in that it further comprises means for cleaning the waveguide (1)
    [18]
    18. - System (100) according to any one of claims 12 to 17, characterized in that it further comprises means for replacing the analyte (s) (7a, 7b) of the waveguide (1).
    [19]
    19. - Use of a system (100) according to any one of claims 12 to 18 as an optical filter.
    [20]
    20. Use of a system (100) according to any one of claims 12 to 18 as an optical sensor.
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