Mirror lens, optical resonator device and method for optical absorption measurement

Abstract

In order to provide a mirror lens which enables ultrasensitive, spectrally resolved absorption measurements in the nano range and efficient focusing of a light field in the interior of an optical cavity without adversely affecting the finesse of the optical cavity, a mirror lens (100) comprising a housing (10) with a light passage opening (11) is proposed, wherein a reflective and / or refractive lens is arranged in the housing (10), wherein it is furthermore proposed that the mirror lens comprises a dielectric back-reflector (16), or that a curved dielectric mirror (26) is arranged in the light passage opening (11).

Description

[0001] Mirror lens, optical resonator device and method for optical absorption measurement

[0002] The present invention relates to a mirror lens comprising a housing with a light passage opening, wherein a reflective and / or refractive optic is arranged in the housing.

[0003] Furthermore, the present invention relates to an optical resonator device comprising a mirror objective and a method for optical absorption measurement of samples with a small absorption cross section using an optical resonator device.

[0004] Technological background

[0005] Fluorescence spectroscopy of single quantum emitters such as molecules, color centers, or nanocrystals is a well-established field of research. The ability to study the fluorescence of individual quantum emitters has provided deep insights into the photophysics of these structures and enabled new imaging techniques in the life sciences.

[0006] However, comparable techniques for measuring the absorption spectra of nanoscale quantum structures are not known. Absorption spectra contain a wealth of information that is not accessible through fluorescence. For example, fluorescence spectra are usually dominated by a few or even a single state. Absorption spectra, on the other hand, can map the spectrum and density of states of a sample across a broad energy window. It is not uncommon for samples to have similar or even indistinguishable fluorescence spectra but exhibit significant differences in absorption. Methods for measuring absorption spectra at the microscopic level are therefore of great interest in many areas of nanotechnology and for the life sciences.

[0007] In fluorescence spectroscopy, samples are typically excited with short-wavelength light, and the subsequently emitted longer-wavelength fluorescence is detected and analyzed. The fluorescence detector can be shielded from the excitation light by optical filters or by temporally separating sample excitation and fluorescence light detection, e.g., by using pulsed lasers and time-resolved detection. In both cases, the fluorescence signal is detected against a "dark" background. In contrast, absorption spectroscopy measures the extinction of an incident light signal. The very small absorption cross sections of individual nanostructures mean that most of the incident photons pass through without interacting with the nanostructure. The resulting very weak extinction signal is consequently overlaid by a very strong background of directly transmitted light.This intense background is inevitably associated with strong photon noise, which typically overshadows the absorption features of interest. Additional noise can be caused by mechanical instabilities in the setup, intensity fluctuations of the excitation light source, and dark counts of the detector.

[0008] Some of these obstacles can be mitigated by rapidly moving the sample in and out of the probe's focused light beam. This allows for a direct and rapid comparison between the background signal and the sample's absorption characteristics. However, this technique is of limited use because it does not eliminate the strong photon noise of the directly transmitted light.

[0009] There is still a fundamental need for devices and methods that enable ultrasensitive spectrally resolved absorption measurements at the nanoscale.

[0010] A microscopy measuring system is known from US 2017 / 0261739 A1. The measuring system comprises a focused light source, a first mirror, a plurality of first lenses, a second mirror, a plurality of second lenses, and an imaging device. The first mirror is positioned on a first side of a sample and configured to receive light from the light source. The plurality of first lenses is arranged between the first mirror and the sample. The second mirror is located on a second side of the sample. The plurality of second lenses is located between the second mirror and the sample. The imaging device is arranged adjacent to the second mirror and configured to receive the light from the light source after the light has undergone a plurality of reflections between the first mirror and the second mirror and through the first lenses and second lenses.

[0011] From DE 10 2012 106 867 B4, a confocal light microscope with or without a pinhole for carrying out optical absorption measurements on a sample with a small absorption cross section is known, comprising at least one light source, wherein the light microscope has an optical resonator which is designed to receive the sample and to expose it to light.

[0012] Description of the invention: task, solution, advantages

[0013] The present invention is based on the object of providing a mirror lens that enables ultrasensitive spectrally resolved absorption measurements in the nanorange and efficient focusing of a light field inside an optical cavity with very high finesse.

[0014] To achieve the object underlying the invention, a mirror lens comprising a housing with a light passage opening is proposed, wherein a reflective and / or refractive optic is arranged in the housing, wherein it is further provided that the mirror lens comprises a dielectric back reflector, or that a curved dielectric mirror is arranged in the light passage opening.

[0015] The mirror lens comprises a housing. The housing can be substantially rotationally symmetrical, with the rotational axis or axis of symmetry of the housing essentially corresponding to the optical axis of the mirror lens.

[0016] The light passage opening is designed to allow light to both exit and enter the housing. The mirror objective is preferably suitable for use in a resonator-enhanced microscopy method or in a method for optical absorption measurement.

[0017] According to the invention, the mirror lens has a dielectric back reflector. Alternatively or additionally, a curved dielectric mirror can also be arranged in the light passage opening.

[0018] Resonator-enhanced microscopy techniques, as well as methods for optical absorption measurement, are based on optical cavities that combine high finesse with a tight focusing of the trapped light. The finesse of an optical cavity is a measure of how close the optical resonances are in relation to their frequency separation. The finesse of an optical cavity is given by F / TI = =1 / (1-R) ​​for R close to 1, where R is the reflectivity of the mirrors of the optical

[0019] Cavity. Dielectric mirrors have a high reflectivity of preferably over 99%, more preferably over 99.9%. Due to the dielectric back reflector or the curved dielectric mirror arranged in the light passage opening, a mirror lens can be provided that can be used in optical cavities with very high finesse.

[0020] Preferably, the optics comprise a primary concave mirror and a secondary convex mirror, the primary mirror having a central aperture, the primary mirror and the secondary mirror being dielectric mirrors.

[0021] The primary mirror has a central aperture, which means in particular that the primary mirror has a hole or opening in the center through which light can pass.

[0022] Furthermore, the optics can comprise at least one lens, in particular a converging lens. In resonator-enhanced microscopy methods based on optical cavities and in methods for optical absorption measurement, small focal spot diameters are desirable to achieve maximum interaction between a sample and the light field. Focal spot diameters are a function of the wavelength λ of the incident light and the numerical aperture (NA) of the focusing optics. High numerical apertures enable focusing on focal points with smaller diameters. High numerical apertures therefore also enable better resolution, particularly in the lateral xy plane of an image. The full width at half maximum (FWHM) of the point spread function in a confocal microscope can be estimated as FWHM = 0.51A / NA. Focusing optics can be used to achieve high numerical apertures.However, additional focusing optics can cause additional losses due to scattering, reflection, and absorption. This can adversely affect the overall finesse of an optical cavity.

[0023] By designing the mirror lens with a primary concave mirror and a secondary convex mirror, as well as a dielectric back reflector or a dielectric mirror arranged in the light passage opening, achromatic focusing over a wide spectral range is possible. The mirror lens can be equipped with dielectric mirrors that can be used for light in the far-infrared to far-UV range. The dielectric mirrors can reflect in narrowband or broadband wavelength ranges.

[0024] When the mirror objective is used in an optical resonator device, the dielectric back reflector, as explained below, can form an optical cavity together with another resonator mirror. The mirror objective is then arranged, so to speak, between the back reflector forming the optical cavity and the resonator mirror. Thus, the advantages of the mirror objective, namely achromatic focusing and low light losses over a wide spectral range, can also be advantageously achieved in an optical resonator device and in processes performed therewith, such as resonator-enhanced microscopy methods or methods for optical absorption measurement.If a curved dielectric mirror is located in the light passage opening of the mirror lens, then when the mirror lens is used in an optical resonator device, the optical cavity can be formed between the curved dielectric mirror arranged in the light passage opening and the resonator mirror. In this case, the mirror lens with the reflective and / or refractive optics is located outside the optical cavity, so that the mirror lens has no influence on the finesse of the optical cavity. In this case, the optics can therefore be a refractive optic and, in particular, comprise a lens, furthermore, in particular a converging lens. However, it is also possible in this case for the optics to comprise a primary concave mirror and a secondary convex mirror.

[0025] The mirror lens has extremely low light losses and is therefore suitable for integration into optical cavities with very high finesse.

[0026] Preferably, the secondary mirror is arranged and configured to reflect light entering through the aperture onto the primary mirror and / or to reflect light reflected by the primary mirror out through the aperture.

[0027] Furthermore, it can be provided that the back reflector is arranged and configured to reflect light exiting through the aperture back through the aperture.

[0028] The back reflector is preferably arranged on a side of the housing opposite the light passage opening. The back reflector can be arranged and / or attached directly to the housing of the mirror objective, but it is also possible for the back reflector to be arranged at a distance from the housing. A spaced arrangement is particularly advantageous when the mirror objective is integrated into a microscopy setup.

[0029] Preferably, the primary mirror is a spherical or aspherical mirror, and / or the secondary mirror is a spherical or aspherical mirror. In principle, the primary mirror and the secondary mirror can be spherical mirrors. Furthermore, the primary mirror and the secondary mirror can be aspherical mirrors. Combinations are also possible, such that, for example, the primary mirror is a spherical mirror and the secondary mirror is an aspherical mirror. The primary mirror and / or the secondary mirror can, in particular, also be hyperbolic mirrors or parabolic mirrors.

[0030] It is preferably provided that the primary mirror and the secondary mirror have a common center of curvature.

[0031] In this case, it is particularly advantageous if the primary and secondary mirrors are spherical. The mirror lens can then be designed similarly to a Schwarzschild lens.

[0032] In addition, it can be provided that the mirror lens is an infinity corrected mirror lens.

[0033] However, it is also possible that the mirror lens is a finitely corrected mirror lens.

[0034] It is further advantageous that the primary mirror and the secondary mirror and / or the rear reflector and / or the light passage opening and / or the curved mirror are arranged concentrically.

[0035] It can further preferably be provided that the secondary mirror is arranged between the primary mirror and the light passage opening, wherein in particular preferably the primary mirror is arranged between the secondary mirror and the rear reflector.

[0036] The relative arrangement of the first and secondary mirrors, or the rear reflector, is to be understood with respect to the axis of symmetry or optical axis of the mirror lens. Thus, starting from a first end of the mirror lens, the rear reflector can be provided first. This is followed by the primary mirror, then the secondary mirror, and finally the light passage opening. However, it is also fundamentally possible for the rear reflector to be arranged at a first end of the housing, followed by the secondary mirror and then the primary mirror. The light passage opening of the housing is then located behind the primary mirror.

[0037] In addition, it can be provided that the lens and / or the rear reflector and / or the light passage opening and / or the curved mirror are arranged concentrically.

[0038] With further advantage, it can be provided that the rear reflector is a curved, in particular concave, mirror.

[0039] Furthermore, it can be provided that the mirror lens further comprises actuators, wherein a position of the rear reflector or the curved mirror can be varied by means of the actuators.

[0040] If the mirror lens includes a back reflector, the optical cavity of an optical resonator device equipped with the mirror lens can be stabilized to a specific resonance wavelength by operating the actuators by precisely adjusting and actively controlling the position of the back reflector and thus the length of the optical cavity.

[0041] If the mirror lens has a curved mirror in the light passage opening, its position can be varied by operating the actuators, thus precisely adjusting the length of the optical cavity and stabilizing the resonance frequency of the optical cavity.

[0042] Particularly in applications such as resonator-enhanced microscopy or optical absorption measurement, varying the position of the back reflector and / or the curved mirror in the light passage aperture also makes it possible to scan samples at least two-dimensionally in the xy plane, but possibly also three-dimensionally in the xyz direction. In particular, the focal point of the mirror objective can be scanned in the xyz direction by varying the position of the back reflector and / or the curved mirror.

[0043] Preferably, the actuators are piezo actuators.

[0044] A further solution to the problem underlying the invention consists in an optical resonator device, in particular suitable for carrying out optical absorption measurements, wherein the optical resonator device comprises a mirror objective as described above.

[0045] It can preferably be provided that the optical resonator device comprises a, preferably planar, resonator mirror, and that the optical resonator device comprises an optical cavity, wherein the optical cavity is formed between the resonator mirror and the back reflector or between the resonator mirror and the curved mirror.

[0046] In the case where the optical cavity is formed between the resonator mirror and the curved mirror, the reflective and / or refractive optics of the mirror lens are located outside the optical cavity and thus have no influence on the finesse of the optical cavity.

[0047] Furthermore, it can be provided that the optical resonator device comprises a substrate, wherein the substrate contains the resonator mirror and at least one

[0048] Spacer layer, wherein the at least one spacer layer is arranged on the resonator mirror, in particular on an upper side of the resonator mirror, wherein a sample can be arranged on the spacer layer.

[0049] Preferably, the substrate has two spacer layers.

[0050] The at least one spacer layer is preferably located within the optical cavity formed by the resonator mirror and the back reflector or the curved mirror. The spacer layer ensures that a sample to be tested is positioned at an antinode of the light field reflected by the resonator mirror at an optical distance of λ / 4 from the surface of the resonator mirror.

[0051] It can be further advantageously provided that the optical resonator device comprises actuators, wherein a position of the resonator mirror can be varied by means of the actuators, wherein the actuators are preferably piezo actuators.

[0052] Analogous to the actuators of the mirror lens, the actuators, in particular the piezo actuators, of the optical resonator device can be used to position the resonator mirror and thus adjust the length of the optical cavity.

[0053] Actuators can be provided exclusively on the resonator mirror. However, it is also conceivable for both the mirror lens and the resonator mirror to have actuators.

[0054] Furthermore, it can be provided that the substrate comprises, preferably plasmonic or dielectric, nanostructures and / or biofunctionalization structures, wherein the nanostructures and / or biofunctionalization structures are preferably provided in or on the at least one spacer layer.

[0055] By designing the substrate with plasmonic or dielectric nanostructures, additional signal amplification can be achieved through additional light confinement and / or through a surface-enhanced Raman scattering effect. This additional signal amplification can be useful for biosensing applications for the detection of DNA, viruses, bacteria, cells, antibodies, or other substances. The substrate can be indented, protruded, or flat at the locations where the plasmonic or dielectric nanostructures are located.

[0056] A further solution to the problem underlying the invention lies in the provision of a method for optical absorption measurement on samples with a small absorption cross section, wherein a sample is arranged in a previously described optical resonator device. Particularly preferably, the sample is arranged on a substrate within an optical cavity of the optical resonator device.

[0057] With further advantage, it can be provided that the sample is exposed to light.

[0058] Short description of the characters

[0059] The invention is explained in more detail below with reference to the accompanying figures. They show:

[0060] Fig. 1 shows a first variant of a first embodiment of a mirror lens,

[0061] Fig. 2 shows a second variant of the first embodiment of a mirror lens,

[0062] Fig. 3 shows a third variant of the first embodiment of a mirror lens,

[0063] Fig. 4 shows a fourth variant of the first embodiment of a mirror lens,

[0064] Fig. 5 shows a first variant of a second embodiment of a mirror lens,

[0065] Fig. 6 shows a second variant of the second embodiment of a mirror lens,

[0066] Fig. 7 shows a third variant of the second embodiment of a mirror lens,

[0067] Fig. 8 shows a fourth variant of the second embodiment of a mirror lens,

[0068] Fig. 9 a third embodiment of a mirror lens,

[0069] Fig. 10a is a sectional view of a substrate, and

[0070] Fig. lOb a top view of the substrate.

[0071] Detailed description of the characters

[0072] Figs. 1 to 9 show, in schematic representation, different embodiments of a mirror objective 100 in an optical resonator device 200, which is suitable for carrying out methods for optical absorption measurement or resonator-enhanced microscopy methods.

[0073] 1 to 4 relate to variants of a first embodiment of the mirror lens 100 or of the optical resonator device 200, and FIGS. 5 to 8 relate to variants of a second embodiment of the mirror lens 100. In all variants of the first and second embodiments, the mirror lens 100 comprises a housing 10 with a light passage opening 11, wherein a primary concave mirror 12 and a secondary convex mirror 13 are arranged in the housing 10. The primary mirror 12 has a central aperture 14. The secondary mirror 13 is arranged such that light 15 entering through the aperture 14 is reflected onto the primary mirror 12, or light 15 reflected by the primary mirror 12 is reflected out through the aperture 14. Both the primary mirror 12 and the secondary mirror 13 are dielectric mirrors.

[0074] In the variants of the embodiments according to Figs. 1 to 4, the mirror lens 100 further comprises a dielectric back reflector 16, wherein the primary mirror 12 is arranged between the back reflector 16 and the secondary mirror 13. The secondary mirror 13 is also arranged between the first mirror 12 and the light passage opening 11. In the arrangement in the optical resonator device 200 according to Figs. 1 to 4, an optical cavity 17 is formed between the back reflector 16 and a resonator mirror 18. In the variant according to Fig. 1, light 15 can be coupled into the optical cavity 17 by the back reflector 16.Due to the high reflectivity of the dielectric mirrors, in particular the back reflector 16, the resonator mirror 18, the primary mirror 12, and the secondary mirror 13, the light 15 passes through the optical cavity 17 very frequently, with each reflection at the back reflector 16 coupling out a small amount of light 15, which is evaluated for further processing. The optical resonator device 200 comprises a substrate 19 into which the resonator mirror 18 is embedded. A spacer layer 21 is arranged on a top side 20 of the resonator mirror 18, on which a sample 22 is arranged. In the variant according to Fig. 1, the optical resonator device 200 has piezo actuators 23, by means of which a position of the substrate 19 and thus also of the resonator mirror 18 can be adjusted. The variant according to Fig. 2 differs from the variant according to Fig. 1 in that the piezo actuators 23 are part of the mirror lens 100.The position of the rear reflector 16 can be varied using the piezo actuators 23 of the mirror lens 100.

[0075] In the embodiment according to Fig. 3, the light 15 is coupled into the optical cavity 17 by the resonator mirror 18, unlike the variants according to Figs. 1 and 2. The portion of the light 15 emerging during each pass is coupled out by the back reflector 16. A further variant is shown in Fig. 4. In contrast to the variant according to Fig. 3, a window 24 or a pane is located in the light passage opening 11. The mirror lens 100 is immersed with the window 24 in oil 25 or water. The window 24 can have an anti-reflection coating.

[0076] Variants of a second embodiment of the mirror objective 100 of the optical resonator device 200 are shown in Figs. 5 to 8. The mirror objective 100 according to Figs. 5 to 8 does not comprise a back reflector 16. Instead, a concavely curved dielectric mirror 26 is arranged in the light passage opening 11. In the optical resonator device 200, the optical cavity 17 is thus formed between the curved mirror 26 in the light passage opening 11 and the resonator mirror 18. In the variant according to Fig. 5, light 15 is coupled into and out of the mirror objective 100 via the aperture 14 of the primary mirror 12 and into the cavity 17 via the curved mirror 26. In Fig. 5, the position of the resonator mirror 18 is adjusted by means of piezo actuators 23. In a further variant according to Fig. 6, the curved mirror 26 is mounted on piezo actuators 23 in the light passage opening 11.By means of the piezo actuators 23, the curved mirror 26 can be moved at least in the xy plane, preferably also three-dimensionally, in order to adjust the length of the optical cavity 17. In the variant according to Fig. 6, light 15 is coupled into the optical cavity 17 by the resonator mirror 18. The light 15 is coupled out by the curved mirror 26 in the light passage opening 11 and leaves the mirror objective 100 through the aperture 14 of the primary mirror 12. In the embodiment according to Fig. 7, the order of the primary mirror 12 and the secondary mirror 13 is reversed compared to the embodiment according to Fig. 6. Apart from that, however, this embodiment is identical. In the embodiment according to Fig. 8, the curved mirror 26 in the light passage opening 11 is immersed in oil 25 or water.

[0077] In the third embodiment of the mirror lens according to Fig. 9, as in the variants of the second embodiment according to Figs. 5 to 8, a concavely curved dielectric mirror 26 is arranged in the light passage opening 11. In the optical resonator device 200, the optical cavity 17 is thus also formed between the curved mirror 26 in the light passage opening 11 and the resonator mirror 18. However, instead of a reflective optic consisting of a primary mirror 12 and a secondary mirror 13, a converging lens 33 is arranged in the housing in the embodiment according to Fig. 9. The converging lens 33 is located outside the optical cavity 17 and therefore has no influence on the finesse of the optical cavity 17. The curved mirror 26 in the light passage opening 11 is mounted on piezo actuators 23.

[0078] Figures 10a and 10c show a side view and a top view of the substrate 19 of the optical resonator device 100 of Figs. 1 to 9. The substrate 19 comprises the dielectric resonator mirror 18. Two spacer layers 21, TI, are arranged on a top side 20 of the resonator mirror 18. Plasmonic or dielectric nanostructures 28 are embedded in the second spacer layer TI. The nanostructures 28 are located within the second spacer layer TI, so that the substrate 19 has elevations 29 in the region of the nanostructures 28. Biofunctionalization structures 31 are also arranged on the top side 30 of the second spacer layer TI. The nanostructures 28 can, as shown in Fig. 10b, be arranged in a grid for suitable indexing. The substrate 19 may also have markers 32, which can be used to align the substrate 19 in the optical resonator device 200.

[0079] List of reference symbols

[0080] 100 mirror lens

[0081] 200 Optical resonator device

[0082] 10 housings

[0083] 11 Light passage opening

[0084] 12 Primary concave mirror

[0085] 13 Secondary convex mirror

[0086] 14 aperture

[0087] 15 light

[0088] 16 Rear reflector

[0089] 17 Optical cavity

[0090] 18 resonator mirrors

[0091] 19 Substrat

[0092] 20 Top

[0093] 21 Spacer layer

[0094] 22 Sample

[0095] 23 piezo actuators

[0096] 24 windows

[0097] 25 oil

[0098] 26 Curved Mirror

[0099] 27 Spacer layer

[0100] 28 Nanostructure

[0101] 29 Survey

[0102] 30 Top

[0103] 31 Biofunctionalization structure

[0104] 32 markers

[0105] 33 Converging lens

Claims

Patent claims 1. Mirror lens (100) comprising a housing (10) with a light passage opening (11), wherein a reflective and / or refractive optic is arranged in the housing (10), characterized in that the mirror lens comprises a dielectric back reflector (16), or that in the light passage opening (11) a curved dielectric mirror (26) is arranged.

2. Mirror lens (100) according to claim 1, wherein the optics comprises a primary concave mirror (12) and a secondary convex mirror (13), wherein the primary mirror (12) has a central aperture (14), wherein the primary mirror (12) and the secondary mirror (13) are dielectric mirrors, and / or wherein the optics comprises at least one lens, in particular a converging lens (33).

3. Mirror lens (100) according to claim 2, wherein the secondary mirror (13) is arranged and configured to reflect light (15) entering through the aperture (14) onto the primary mirror (12) and / or to reflect light (15) reflected by the primary mirror (12) out through the aperture (14).

4. Mirror lens (100) according to claim 2 or 3, wherein the back reflector (16) is arranged and configured to reflect light (15) exiting through the aperture (14) back through the aperture (14).

5. Mirror lens (100) according to one of claims 2 to 4, wherein the primary mirror (12) is a spherical or an aspherical mirror, and / or wherein the secondary mirror (13) is a spherical or an aspherical mirror, and / or wherein the primary mirror (12) and the secondary mirror (13) have a common center of curvature.

6. Mirror objective (100) according to one of the preceding claims, wherein the primary mirror (12) and the secondary mirror (13) and / or the lens and / or the back reflector (16) and / or the light passage opening (11) and / or the curved mirror (26) are arranged concentrically, and / or wherein the secondary mirror (13) is arranged between the primary mirror (12) and the Light passage opening (11) is arranged, wherein preferably the primary mirror (12) is arranged between the secondary mirror (13) and the rear reflector (16).

7. Mirror lens (100) according to one of the preceding claims, wherein the back reflector (16) is a curved, in particular concave, mirror.

8. Mirror lens (100) according to one of the preceding claims, further comprising actuators, wherein a position of the back reflector (16) or of the curved mirror (26) can be varied by means of the actuators, wherein the actuators are preferably piezo actuators (23).

9. Optical resonator device (200), in particular for carrying out optical absorption measurements, comprising a mirror objective (100) according to one of the preceding claims.

10. Optical resonator device (200) according to claim 9 comprising a, preferably planar, resonator mirror (18), characterized in that the optical resonator device comprises an optical cavity (17), wherein the optical cavity (17) is formed between the resonator mirror (18) and the back reflector (16) or between the resonator mirror (18) and the curved mirror (26).

11. Optical resonator device (200) according to claim 10, characterized in that the optical resonator device (200) comprises a substrate (19), wherein the substrate (19) comprises the resonator mirror (18) and at least one spacer layer (21, 27), wherein the at least one spacer layer (21, 27) is arranged on the resonator mirror (18), in particular on a top side (20) of the resonator mirror (18), wherein a sample (22) can be arranged on the spacer layer (21, 27), wherein the substrate (19), more preferably plasmonic or dielectric, comprises nanostructures (28) and / or biofunctionalization structures (31), wherein the nanostructures (28) and / or biofunctionalization structures (31) are particularly preferably provided in or on the at least one spacer layer (21, 27).

12. Optical resonator device (200) according to claim 10 or 11, further comprising actuators, wherein a position of the resonator mirror (18) can be varied by means of the actuators, wherein the actuators are preferably piezo actuators (23).

13. A method for optical absorption measurement on samples with a small absorption cross section, characterized in that a sample (22) is arranged in an optical resonator device (200) according to one of claims 9 to 12.

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