On-chip absorption sensor for determining a concentration of a specimen in a sample

Abstract

An on-chip optical absorption sensor for determining a concentration of a specimen in a sample, the optical absorption sensor comprising at least one light emitting device, configured to emit light in a first direction and a second direction being opposite the first direction; at least one sample holder configured to receive the sample, wherein the at least one sample holder is at least partially transparent for the emitted light, such that at least a portion of the light emitted in the first direction can propagate through at least a portion of the sample holder; at least one first light detector being arranged to detect at least partially the intensity I of the propagated light having propagated through the sample holder in the first direction; at least one second light detector being arranged to detect at least partially the intensity I of the light emitted in the second direction.

Claims

1. An on-chip optical absorption sensor for determining a concentration of a specimen in a sample, the optical absorption sensor comprising: at least one light emitting device, configured to emit light in a first direction and a second direction being opposite the first direction when excited by means of a pump radiation; at least one sample holder configured to receive the sample, wherein the at least one sample holder is at least partially transparent for the emitted light, such that at least a portion of the light emitted in the first direction can propagate through at least a portion of the sample holder; at least one first light detector being arranged to at least partially detect the intensity I of the propagated light having propagated through the sample holder in the first direction; and at least one second light detector being arranged to at least partially detect the intensity I of the light emitted in the second direction, wherein the on-chip optical absorption sensor has at least one sandwich structure of stacked layers, the one sandwich structure comprising: the light emitting device being configured as a substantially planar light emitting layer; the sample holder being configured as a substantially planar sample chamber layer; the first light detector being configured as a first light detection layer; and the second light detector being configured as a second light detection layer; wherein the first light detection layer, the sample chamber layer, the planar light emitting layer and the second light detection layer are stacked in this order along the second direction of the emitted light.

2. An on-chip optical absorption sensor according to claim 1, wherein the at least one light emitting device comprises at least one coherent light emitting device, configured to emit a light which is a coherent light in a first direction and a second direction being opposite the first direction.

3. The on-chip optical absorption sensor of claim 1, wherein the light emitting device is configured as a substantially planar light emitting layer, wherein the normal direction of the light emitting layer is substantially parallel to the first and second directions of the emitted light.

4. The on-chip optical absorption sensor of claim 1, wherein the light emitting device comprises a vertically emitting laser comprising at least one distributed feedback laser, DFB, a distributed Bragg reflector laser, DBR, a vertical-cavity surface-emitting laser, VCSEL, a Vertical External Cavity surface-emitting laser, VECSEL, and/or a tapered laser.

5. The on-chip optical absorption sensor of claim 1, wherein the light emitting device comprises an organic second order DFB laser.

6. The on-chip optical absorption sensor of claim 1, wherein the light emitting device comprises an array of light emitting elements, wherein the light emitting elements are arranged in at least one column and are spaced apart by a distance Δ.

7. The on-chip optical absorption sensor of claim 6, wherein the array of light emitting elements comprises at least two columns of light emitting elements, wherein the at least two columns are spaced apart by a distance β.

8. The on-chip optical absorption sensor of claim 1, wherein the sample holder comprises a sample chamber including at least one chamber volume, wherein the chamber volume includes microfluidic channels for receiving and guiding a fluid sample, and/or holding elements for holding the sample or the sample chamber.

9. The on-chip optical absorption sensor of claim 8, wherein the sample chamber is configured as a substantially planar sample chamber layer, wherein the normal direction of the sample chamber layer is substantially parallel to the first and second directions of the emitted light.

10. The on-chip optical absorption sensor of claim 1, wherein at least two out of the light emitting device, the sample holder, the first light detector and the second light detector are configured as removable and/or replaceable module units.

11. The on-chip optical absorption sensor of claim 1, wherein at least two out of the light emitting device, the sample holder, the first light detector and the second light detector are formed as an integral unit.

12. The on-chip optical absorption sensor of claim 1, further comprising at least one filter element being configured to allow transmission of at least a portion of the emission wavelength range of the emitted light.

13. The on-chip optical absorption sensor of claim 1, wherein the on-chip optical sensor is configured for determining concentrations of one or more specimens in at least two samples.

14. The on-chip optical absorption sensor of claim 13 comprising at least two sandwich structures for determining in each of the sandwich structures the concentration of a specimen of one of the samples.

15. The on-chip optical absorption sensor of claim 13 comprising: a first light emitting device configured to emit light having a first wavelength; and a second light emitting device configured to emit light having a second wavelength, wherein the first wavelength differs from the second wavelength.

16. The on-chip optical absorption sensor of claim 1, further comprising at least one reference holder configured to receive a reference substance, wherein the reference holder is at least partially transparent for the emitted light, such that at least a portion of the light emitted in the second direction can propagate through at least a portion of the reference holder.

17. A system comprising the on-chip optical absorption sensor of claim 1, and at least one processing unit for determining the concentrations of the specimen in the sample according to: $c = - \ln (k_{I} \frac{I}{I_{0}}) / (d {.Math.}^{*})$ wherein I is an attenuated intensity of the propagated light detected by the first light detector, I.sub.0 is a reference intensity of the light emitted in the second direction detected by the second light detector, ε* is an extinction coefficient of the specimen at a wavelength λ of the light, c is a molar concentration of the specimen in the sample, d is a thickness of the sample in the first direction and k.sub.I is a factor taking into account a the relation between the intensities of light being emitted into the first and the second directions.

18. A method for determining a concentration of a specimen in a sample comprises the steps of: providing the on-chip optical absorption sensor according to claim 1; providing the sample in the sample holder; stimulating the light emitting device to emit light; at least partially detecting the intensity I of the propagated light emitted in the first direction and having propagated through the sample holder by means of the first light detector; and the intensity I.sub.0 of the light emitted in the second direction by means of the second light detector; and determining the concentration of the specimen in the sample according to: $c = - \ln (k_{I} \frac{I}{I_{0}}) / (d {.Math.}^{*})$ wherein I is an attenuated intensity of the propagated light detected by the first light detector, I.sub.0 is a reference intensity of the light emitted in the second direction detected by the second light detector, ε* is an extinction coefficient of the specimen at a wavelength λ of the light, c is a molar concentration of the specimen in the sample, d is a thickness of the sample in the first direction and k.sub.I is a factor taking into account a the relation between the intensities of light being emitted into the first and the second directions.

19. A sandwich-type on-chip optical absorption sensor for determining a concentration of a specimen in a sample, the optical absorption sensor comprising in a stacked configuration along the first direction a second light detector, which is configured as a second light detection layer; a light emitting device comprising an organic second-order DFB laser grating configured as a substantially planar light emitting layer and configured to emit light into a first direction and a second direction when excited by means of a pump radiation, the second direction being opposite to the first direction; a sample holder comprising at least one microfluidic channel for receiving and guiding a fluid sample configured as a substantially planar sample chamber layer, wherein the microfluidic channel is at least partially transparent for the emitted light such that at least a portion of the light emitted in the first direction can propagate through at least a portion of the microfluidic channel of the sample chamber layer as propagated light; and a first light detector which is configured as a first light detection layer; wherein an intensity I.sub.0 of the light emitted in the second direction can be at least partially detected by the second light detector as a reference intensity; and an intensity I of the propagated light can be at least partially detected by the first light detector as a probe intensity for determining the concentration of the specimen in the sample.

20. The sandwich-type on-chip optical absorption sensor of claim 19, wherein the first and the second directions are substantially parallel to the normal directions of the first light detection layer, the second light detection layer, the light emitting layer and the sample chamber layer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a front exploded view of an on-chip optical absorption sensor according to an aspect;

(2) FIG. 2 is a perspective exploded view of an on-chip optical absorption sensor according to another aspect;

(3) FIG. 3 is a perspective view of an on-chip optical absorption sensor according to another aspect, wherein the second light detector is not displayed;

(4) FIG. 4a is a front view of a light emitting element of a light emitting device according to an aspect;

(5) FIG. 4b is a front exploded view of a detail of the light emitting element of FIG. 4a;

(6) FIG. 5 is a front exploded view of a detail of a light emitting device comprising the light emitting element of FIG. 4a;

(7) FIG. 6 is a front exploded view of an on-chip optical absorption sensor according to another aspect;

(8) FIG. 7 is a front exploded view of an on-chip optical absorption sensor according to another aspect;

(9) FIG. 8 is a front exploded view of an on-chip optical absorption sensor according to another aspect;

(10) FIG. 9 is a schematic view of a system according to an aspect comprising an on-chip optical absorption sensor; and

(11) FIG. 10 is a front exploded view of an on-chip optical absorption sensor according to another aspect.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(12) FIG. 1 is a front exploded view of an on-chip optical absorption sensor 100. Particularly, an example of a sandwich structure S1 is shown in FIG. 1 and will be described in the following.

(13) Between two light detectors, a first light detector 4 and a second light detector 5, a light emitting device 2 is positioned or arranged. A light detector 4, 5 may also be considered a light sensor and/or a photodetector.

(14) The light emitting device 2 emits light L.sub.D, L.sub.U at least partially into a first direction D and a second direction U. The first and second directions D, U are substantially opposite to each other, i.e., having an angle of substantially 180° between each other. In the schematic view of FIG. 1 the first direction D points “downward” with substantially 90° from the horizontal plane xy, whereas the second direction U points substantially “upward” with 90° from the horizontal plane xy, both being parallel to a vertical axis z.

(15) Between the first light detector 4 and the light emitting device 2, a sample holder 3 is located. The sample holder 3 may be considered a free space which is limited or confined substantially in the first and second directions D, U, i.e., in the vertical z-direction, by the surfaces of the first light detector 4 and the light emitting device 2, respectively. The sample holder 3 may in addition provide holding elements 33 for holding a sample 1 or a sample chamber 31, as indicated in the FIG. 1. The sample 1 may be substantially fluid, particularly liquid. The fluid may be filled into the chamber volume 34 of the sample chamber 31, as indicated in FIG. 1. The sample 1 is configured and/or layered in such a way that it has a certain layer thickness d in the first direction D.

(16) A fluid may be a material in a state having a fluidic behavior, such as a liquid, a gas or a powder. A fluid may also be a combination of materials in states showing a fluidic behavior such as a liquid in which particles are suspended. Other examples for mixed materials with different states which may show fluid behavior are aerosols, foams, suspensions, emulsions and mixes of powders. Alternatively, the sample 1 may also be substantially solid and/or soft but not fluidic. For example, the sample 1 may be a thin cut of a material, particularly a biological dissection. The sample holder 3 may have holding elements 33 for receiving, holding, fixing and/or arranging a non-fluidic sample 1. In addition or alternatively, the sample holder 3, particularly the holding elements 33 may be configured to receive, hold, fix and/or arrange the sample chamber 31 including a chamber volume 34 for receiving, guiding and/or hosting a fluid sample, particularly a liquid sample.

(17) In a measurement configuration, i.e., when a concentration of a specimen in a sample 1 is to be determined, a sample 1 is placed, arranged and/or positioned into the sample holder 3. The arrangement is such that the light L.sub.D emitted by the light emitting device 2 in the first direction D can propagate at least partially through a portion of the volume of the sample 1. The portion of light which leaves the sample holder 3 towards the first direction D, for example after having passed or propagated through the sample and the sample chamber 31 is referred to as propagated light L.sub.p. The intensity I of the propagated light L.sub.p (or at least of a portion thereof) can then be detected by the first light detector 4. The intensity of the propagated light L.sub.p may be substantially equal to the intensity of the light L.sub.D emitted by the light emitting device 2 in the first direction D in the case when there is no sample 1 or sample chamber 33 or any other element placed between the light emitting device 2 and the first light detector 4.

(18) The light being detected at the first light detector 4 may be considered as incoming light L.sub.14 at the first light detector 4. The propagated light L.sub.p may be attenuated light, wherein attenuation maybe caused at least partly by the interaction with the specimen in the sample 1. The interaction between the light L.sub.D passing the sample and the specimen in the sample 1 may comprise energy transfer in molecular vibration and scatter events. After having passed the sample 1, the propagated light L.sub.p might not have properties any longer. For example, scatter events may destroy the property of the light L.sub.D such that the propagated light L.sub.p may not be coherent. The intensity of light might also be referred to as the amount of light.

(19) The light emitting device 2 emits light L.sub.U at least partially in the second direction U. The intensity I.sub.0 of incoming light L.sub.15 which is detected at the second light detector 5 may be substantially identical to the intensity of light L.sub.U being emitted from the light emitting device 2 in the second direction U. This is particularly the case, when no element is positioned between the light emitting device 2 and the second light detector 5.

(20) The light emitting device 2 emits lights L.sub.D and L.sub.U into a first direction D and a second direction U, respectively, wherein the intensity I.sub.D of the light L.sub.D emitted in the first direction D may be substantially identical to the intensity I.sub.U of the light L.sub.U emitted in the second direction U, at least fora period of time, particularly fora period of time required for one measurement:
I.sub.D≅I.sub.U

(21) Alternatively, the intensity I.sub.D of the light emitted in the first direction D may substantially equal the intensity I.sub.U of the light emitted in the second direction U multiplied by a factor k.sub.I which is substantially constant over at least a short period of time, i.e. over at least approximately 5 s, particularly over at least approximately 15 s, more particularly over at least approximately 30 s. In general, a short period of time may be for example approximately 2 s to 10 minutes.

(22) In other words, the relation or ratio between the intensity I.sub.D of the light emitted in the first direction D and the intensity I.sub.U of the light emitted in the second direction U is substantially constant over at least a short period of time:

(23) $\frac{I_{D}}{I_{U}} = k_{I} ≅ const .$
k.sub.I may for example be 1 in a case, in which the intensity I.sub.0 of light L.sub.D being emitted into the first direction D equals the intensity I.sub.U of light L.sub.U being emitted into the second direction U. Alternatively, k.sub.I may for example equal 0.5 in a case, in which the intensity I.sub.D of light L.sub.D being emitted into the first direction D equals half the intensity I.sub.U of light L.sub.U being emitted into the second direction U.

(24) A calibration measurement is regularly performed to determine the values I.sub.D and I.sub.U. When a calibration measurement is performed to obtain the values I.sub.D and I.sub.U, preferably all optical elements remain in the on-chip optical absorption sensor, as potential reflections, attenuations and/or deviations or other optical effects originating from the optical elements can be taken into account in the calibration measurement data.

(25) Alternatively, all optical elements except the light emitting device 2 and the light detectors 4, 5 may be removed, if this is possible, particularly the sample chambers 31 may be removed. If for example a light emitting device 2 is formed with a sample chamber 31 as an integral or permanently connected unit, the sample chamber remains in the on-chip optical absorption sensor, however the chamber volume Vs may remain unfilled or filled only with a liquid solution which does not contain the sample 1 and particularly not the specimen.

(26) The values I.sub.D and I.sub.U may be considered the intensities I and I.sub.0 measured at the first and second light detectors 4, 5 in a calibration configuration, i.e. a configuration used for a calibration measurement, as described above in the preferred or the alternative configuration. Particularly a calibration measurement is performed in the absence of a sample 1, particularly a specimen, i.e., without placing a sample 1 with a specimen into the sample holder 3 and/or the sample chamber 31.

(27) The factor k.sub.I deviates from 1 in a case, when the light emitting device 2 emits light L.sub.D, L.sub.U into the first D and second directions U, respectively having substantially different intensities I.sub.D, I.sub.U. At the same time, over a period of time the intensities I.sub.D, I.sub.U may also vary, for example fluctuate or decrease, however, the relation expressed in the factor k.sub.I is at least over a period of time, for example during a measurement, substantially stable, i.e. constant.

(28) Further, the factor k.sub.I may also vary for different light emitting devices 2 of different on-chip optical absorption sensors, for example due to variations in the preparation and production steps.

(29) Moreover, the factor k.sub.I may vary spatially along the surface of the light emitting device 2. Hence, it is preferable to perform a calibration measurement at least once, to obtain the values I.sub.D and I.sub.U in order to determine the factor k.sub.I. It may even be preferable to perform such calibration measurements before each measurement using one single on-chip optical absorption sensor.

(30) The intensity I.sub.0 of incoming light L.sub.15 which is detected at the second light detector 5 is hence used as a reference intensity for determining the concentration of the specimen in the sample 1 according to:

(31) $c = - \ln (k_{I} \frac{I}{I_{0}}) / (d {.Math.}^{*})$
wherein I is an attenuated intensity of the propagated light L.sub.P detected by the first light detector 4, I.sub.0 is a reference intensity of the light L.sub.U emitted in the second direction U detected by the second light detector 5, ε* is an extinction coefficient of the specimen at a wavelength λ of the light, c is a molar concentration of the specimen in the sample 1 and d is a thickness of the sample 1 in the first direction D.

(32) The light emitting device 2 may be excited by means of a pump laser. The pump laser emits pump radiation 11 at a certain wavelength λ.sub.11 or wavelength range (not shown in the FIG. 1) at which the laser medium, e.g. an organic laser material 23 (also not shown in the FIG. 1), absorbs and can be excited to emit light L.sub.D and L.sub.U.

(33) In order to prevent that the light detectors 4, 5 to detect the intensity of the pump radiation and/or pump light 11, filter elements 6, 7 may be positioned between the light detectors 4, 5 and the light emitting device 2. For example, a filter element 7 may be positioned between the first light detector 4 and the sample chamber 31. Alternatively or in addition, a further filter element 6 may be positioned between the second light detector 5 and the light emitting device 2. The filter elements 6, 7 preferably filters out substantially all the pump radiation 11 being emitted by the pump laser, such that the intensity of the pump radiation 11 at the wavelength or wavelength range λ.sub.11 is substantially zero after having passed the filter elements 6, 7. Preferably, the light L.sub.D and L.sub.u and the propagated light L.sub.P are not blocked or significantly attenuated by the respective filter elements 6, 7 such that the intensity of these light portions is not filtered by the filters 6, 7. In other words, the light L.sub.D and L.sub.u and the propagated light L.sub.P can pass the filters 6, 7 without substantially being attenuated or modified.

(34) The sample chamber 31 may have a port 10 for filling a fluid sample 1 into the volume 34 of the sample chamber 31, as indicated in FIG. 1. In addition, a second port may allow the air or material inside the volume 34 to escape when the sample 1 is filled into the volume 34.

(35) The light detectors 4, 5 are each provided with a cable 9 in this particular drawing of FIG. 1. Alternatively, the light detectors 4, 5 may not require a cable, for example if energy is supplied by a battery and/or data are transferred in a wireless fashion. The cables 9 may be for energy supply and/or data transfer. There may be also more than one cable 9 per detector 4, 5 for energy supply and/or data transfer. Similarly, the light emitting device 2 is in this particular drawing provided with a cable 9 for energy supply and/or for providing a voltage and/or for coupling pump radiation 11 into the lasing material, wherein the cable is in general an optional element. In the latter case, the cable may be a fiber optic for guiding light. The cable 9 on the light emitting device 2 is optional, hence it may not be required in some cases. Particularly, the pump radiation (not shown in FIG. 1) may be provided directly from irradiating the surface of the light emitting device 2 without the requirement of a cable 9, such as a fiber optic.

(36) In FIG. 1, the on-chip optical absorption sensor 100 is in a stacked configuration in which all elements are substantially configured as single pieces. The stacked configuration S1 is such that the first light detector 4, the filter 7, the sample holder 3 including the sample chamber 31, the light emitting device 2, the filter 6 and the second light detector 5 are stacked or configured to be stacked along the second direction U. The above elements are configured to be stacked and/or arranged into or onto a mount 8. The above elements may be permanently or temporarily arranged in or at the mount. Alternatively, some of the above elements may be permanently arranged in or at the mount whereas other elements may be removed, replaced, exchanged and/or added. For example, the sample chamber 31 may be a single use sample 31 which is replaced after a single use. Also, for example, the light emitting device 2 may be exchanged. Further, for example, also one or both of the filter elements 6, 7 may be replaced.

(37) The stacked configuration S1 may be such that the first light detector 4 is configured as a first light detection layer A.sub.4, the filter 7 is configured as a first filter layer A.sub.7, the sample holder 3 including the sample chamber 31 is configured as a sample chamber layer A.sub.31, the light emitting device 2 is configured as a light emitting layer A.sub.21, the filter 6 is configured as a second filter layer A.sub.6 and the second light detector 5 is configured as a second light detection layer A.sub.5, wherein all layers are stacked or configured to be stacked along the second direction U.

(38) At least some elements may be stacked such that their surfaces are substantially flush with the surfaces of the neighboring elements. At least some elements may be stacked such that their surfaces are spaced apart by a gap from the surfaces of the neighboring elements. For example, as indicated in the drawing, the surface of the second detector 5 facing towards the first direction D is spaced apart by distance γ.sub.5-6 from the surface of the filter element 6 facing towards the second direction U. The surface of the filter element 6 facing towards the first direction D is spaced apart by a distance γ.sub.6-2 from the surface of the light emitting device 2 facing towards the second direction U. The surface of the light emitting device 2 facing towards the first direction D is spaced apart by a distance γ.sub.2-31 from the surface of the filter element 7 facing towards the second direction U. The surface of the filter element 7 facing towards the first direction D is spaced apart by a distance γ.sub.7-4 from the surface of the first light detector 4 facing towards the second direction U. These distances may be substantially constant throughout the respective surface areas.

(39) If the surfaces do not substantially lay flush with each other, the distances may vary individually between approximately 100 μm and 1 cm, optionally between approximately 500 μm and 5 mm, more optionally between approximately 800 μm and 2 mm. When the surfaces are flush with each other, the distances may be in the range of 0 to 100 μm.

(40) The sample holder 3, particularly a sample chamber 31 and/or a microfluidic channel structure 32 provides a chamber volume 34 having a volume thickness d.sub.V in the first direction D. A sample 1 which is filled into the chamber volume 34 may hence have a thickness d≤d.sub.V depending on the volume portion that is filled with the sample 1. The thickness d.sub.V may vary between approximately 5 μm and 8 mm, optionally between approximately 100 μm and 3 mm and more optionally between approximately 300 μm and 1 mm. A liquid sample 1 may flow into the chamber volume 34. The liquid sample may flow through the chamber volume 34 from an entrance port 10 to an exit port 10 to exit the chamber volume 34.

(41) The sample volume Vs which may be received by a chamber volume 34 can range between approximately 500 ml in a large optical on-chip absorption device and 5 μl in a small optical on-chip absorption device. Optionally, the sample volume Vs may range between approximately 30 μl and 1 ml and, more particularly between approximately 100 μl and 800 μl. If the chamber volume 34 is completely filled with the sample volume Vs, the chamber volume 34 equals the sample volume Vs.

(42) The normal directions of each of the surfaces or planes, having substantially a 90° angle with the surfaces, are substantially parallel to the first and the second directions D, U. In more detail, the normal direction N.sub.5 of the second light detector 5, the normal direction N.sub.6 of the filter 6, the normal direction N.sub.2 of the light emitting device 2, the normal direction N.sub.31 of the sample chamber 31, the normal direction N.sub.7 of the filter 7, and the normal direction N.sub.4 of the first light detector 4 are the respective normal directions of the xy-planes of the respective layers and are substantially parallel to each other and substantially parallel to the first and the second directions D, U. In FIG. 1, the normals directions are parallel to the vertical axis z and perpendicular to the horizontal plane xy. The main planar surfaces of the layers are substantially parallel to the horizontal plane xy.

(43) The mount 8 may be configured to receive further optical elements, such as for example an optical waveguide for coupling the pump radiation 11 into the light emitting device 2. Moreover, a layer-like device which can emit a pump radiation 11, particularly overlapping the UV region, may be positioned near the light emitting device 2, such that the pump laser is integrated into the sandwich structure. For example, such a layer-like device may comprise a pump laser component which can be positioned above and/or below the light emitting device 2, such that pump light (not shown in FIG. 1) can excite the light emitting device 2 from above and/or below, particularly from above and/or below sides being incident from an angle.

(44) FIG. 2 is a perspective exploded view of an on-chip optical absorption sensor 110 according to another aspect.

(45) Compared to the FIG. 1, the light emitting device 2 further comprises an array 21 of light emitting elements 2a, 2b, 2c, 2d being arranged in a light emitting layer A.sub.2 which is substantially planar. The light emitting elements 2b and 2d are arranged in a column c.sub.1, wherein the light emitting elements 2b and 2d are spaced apart by a distance being the distance from the edge of the light emitting element 2d which is facing the light emitting element 2b to the edge of the light emitting element 2d which is facing the light emitting element 2b. The column c.sub.1 is parallel to and spaced apart at a constant distance from column c.sub.2 comprising the light emitting elements 2a and 2c. The distance β extends from the edge of the light emitting element 2c which is facing the light emitting element 2d to the edge of the light emitting element 2d which is facing the light emitting element 2c.

(46) The distances β and Δ may vary independently between approximately 5 μm and 5 mm, optionally between approximately 300 μm and 1 mm, and optionally between approximately 500 μm and 700 μm.

(47) The array 21 of light emitting elements 2a, 2b, 2c hence comprises a column c.sub.1 comprising two light emitting elements 2b and 2d and a column c.sub.2 comprising two light emitting elements 2a and 2c. The columns c.sub.1, c.sub.2 are arranged so as to form two rows r.sub.2, comprising two light emitting elements 2a and 2b in row r.sub.1 and two light emitting elements 2c and 2d in row r.sub.2.

(48) The light emitting elements 2a, 2b, 2c, 2d each emit light L.sub.D, L.sub.U into a first direction D and a second direction U. The light L.sub.D emitted in the first direction D passes at least partially through the volume of the sample chamber 31 which may comprise microfluidic channels 32a, 32b. The microfluidic channels 32a, 32b are arranged to form two columns being substantially parallel to the columns c.sub.1, c.sub.2 of light emitting elements 2a, 2b, 2c, 2d.

(49) The array 21 of light emitting elements 2a, 2b, 2c is substantially rectangular being formed of substantially rectangular light emitting elements 2a, 2b, 2c, 2d. However, any form of light emitting element 2a, 2b, 2c, 2d and any array pattern may be chosen. For example the light emitting elements 2a, 2b, 2c, 2d could also have a circular shape and the pattern could for example have a circular arrangement of light emitting elements 2a, 2b, 2c, 2d placed, for example equidistant, around a center.

(50) FIG. 3 is a perspective exploded view of an on-chip optical absorption sensor according to another aspect. The on-chip optical absorption sensor 120 is configured in a sandwich structure S3, which will be described in following.

(51) The distances β and Δ between two light emitting elements 2a-2i may vary independently as described above for FIG. 2. Particularly, the light emitting elements in one row r.sub.1, r.sub.2, r.sub.3 may be positioned in a non-equidistant configuration. Similarly, the light emitting elements in one row c.sub.1, c.sub.2, c.sub.3 may also be positioned in a non-equidistant configuration. It may also be possible that all light emitting elements 2a-2i are positioned at random locations with random edge to edge distances β and Δ to the next neighbors.

(52) The second light detector 5 of the sandwich structure S3 is not shown in FIG. 3 but it is part of the structure S3. Compared to the device shown in FIG. 2, FIG. 3 describes a 3×3 array 21 of nine light emitting elements 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i. The nine light emitting elements 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i are arranged in three columns c.sub.2, c.sub.3 forming three rows r.sub.1, r.sub.2, r.sub.3, all being arranged in a light emitting layer A.sub.2.

(53) Each light emitting element 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i may emit light L.sub.D L.sub.U at an individual wavelength, i.e., for example light emitting element 2a emits light at a wavelength λ.sub.1, light emitting element 2b emits light at a wavelength λ.sub.2, light emitting element 2c emits light at a wavelength λ.sub.3 and so on, wherein λ.sub.1, λ.sub.2 and λ.sub.3 are different from each other.

(54) The sample chamber 31 comprises a microfluidic channel structure 32. The microfluidic channel structure 32 comprises three microfluidic channels 32a, 32b, 32c which are each substantially in line with and parallel to one of the columns c.sub.1, c.sub.2, c.sub.3 and arranged substantially in a sample chamber layer A.sub.31. Each of the microfluidic channels 32a, 32b, 32c may host a sample 1A, 1B, 1C. If the wavelength for each column differs from the wavelength of the other columns, concentrations of different specimens can be measured along each column. In addition, the microfluidic channels 32a, 32b, 32c may host different samples 1A, 1B, 1C on one on-chip optical absorption device 120.

(55) The on-chip optical absorption sensor 120 may hence be applied for multiplexed point-of-care testing.

(56) The light emitting elements 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i are excited by means of a pump radiation 11 having a wavelength λ.sub.11 or a wavelength range Δλ.sub.11. The wavelength range Δλ.sub.11 or the different wavelengths may be in a range in which the laser materials of the light emitting elements 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i absorb light and can be excited to emit light L.sub.D, L.sub.U.

(57) The light L.sub.D being emitted in the first direction propagates at least partially through the chamber volume of the microfluidic channels 32a, 32b, 32c. If one or more samples 1A, 1B, 1C are provided inside the microfluidic channels 32a, 32b, 32c, the light L.sub.D might be attenuated due to the interaction between the light L.sub.D and the specimen contained in the samples 1A, 1B, 1C. At least a portion L.sub.14 of the propagated light L.sub.p reaches the first detector 4 after having propagated through the samples 1A, 1B, 1C. The intensity I of the incoming light L.sub.14 at the first detector 4 is detected.

(58) In other words and comprising exemplary aspects, the on-chip optical absorption sensor 120 may comprise an organic laser array of light emitting elements 2a-2i with different laser wavelengths λ.sub.1, λ.sub.2, λ.sub.3 etc., wherein an organic laser array of light emitting elements 2a-2i comprises columns c.sub.1, c.sub.2, c.sub.3 which are positioned over columns 32a, 32b, 32c of a microfluidic channel structure 32. The light L.sub.D emitted by the light emitting elements 2a, 2b, 2c in the first direction D propagates at least partially through the samples 1A, 1B, 1C inside the microfluidic channels or columns c.sub.1, c.sub.2, c.sub.3, respectively. In order to determine the absorption of a particular specimen/analyte, the intensity I of the laser light L.sub.D is detected by the first detector 4 which may be a detector array.

(59) The light emitting device 2 may be an organic laser array as indicated in FIG. 3, particularly, a second order Distributed Feedback (DFB) laser architecture. The laser wavelength λ.sub.1, λ.sub.2, λ.sub.3 etc. can be tailored by the choice of a lattice periodicity A of a DFB grating 22 (not shown in FIG. 3) in the light emitting elements 2a-2i of the array 21 of light emitting elements 2a, 2b, 2c etc. Each light emitting element 2a-2i is coated with the organic laser material. Organic laser materials typically absorb pump light 11 at wavelengths λ.sub.11 in the ultraviolet spectral range (UV) and emit their luminescence as light with wavelengths λ.sub.1, λ.sub.2, λ.sub.3 in the visible spectrum. Any of the variety of organic laser materials with light emission in the entire visible spectral range may be considered. The pump laser may for example emit very short laser pulses in the nanosecond regime.

(60) In the following an exemplary light emitting element 2a is described in further detail.

(61) FIG. 4a is a front view of an exemplary light emitting element 2a for example of an array 21 of light emitting elements 2a, 2b, 2c etc. of a light emitting device 2, as shown in FIG. 3. The light emitting element 2a comprises an overlayer of an organic laser material 23 and an underlayer of a DFB grating 22 which is configured as a lattice. The DFB grating 22 has a grating constant Λ. Within this description, the grating constant may be understood as the periodic length of the grating structure, i.e. the combined width of a line and a space in the periodic sequence of lines and spaces. In other words, the granting constant may be understood as the sum of the width of single line and single space.

(62) The laser emission wavelength may be tailored by the choice of organic laser material 23 and geometric properties, particularly the grating constant Λ of the grating structure 22. It is possible to generate laser light throughout the visible spectrum by varying these parameters. The grating constant Λ may be varied between approximately 3 μm and 3 nm, optionally between approximately 1.5 μm and 150 nm and optionally approximately 300 nm to 700 nm. The method for manufacturing a light emitting device 2 with a DFB grating 22 is described in DE 10 2017 011 726 A1, the disclosure of which is incorporated herein in its entirety.

(63) Organic laser materials often absorb pump light in the ultraviolet spectral range (UV) while emitting a luminescence and a stimulated emission in the visible spectrum. There are plenty of organic laser materials covering light emission wavelengths in the entire visible spectral range.

(64) The laser emission wavelength of a grating 22 as described above may be tuned between approximately 450 nm and 700 nm, optionally between approximately 500 nm and 590 nm, for example approximately 540 nm.

(65) A light emitting element 2a may have a length 25 and a width 24, wherein the length 25 and the width 24 may independently vary between approximately 50 μm and 10 mm, optionally between approximately 500 μm and 5 mm, optionally between approximately 800 μm and 1 mm. An array 21 of light emitting element 2a-2i as displayed in FIG. 3 may comprise light emitting element 2a-2i with different sizes, i.e., wherein the length 25 and/or the width 24 of at least two or of each of the light emitting elements 2a-2i differ from another.

(66) A light emitting element 2a may also have a larger size compared to the one described above. For example, a light emitting element 2a may have a length 25 and a width 24 independently varying between approximately 1 cm and 5 cm, optionally between approximately 2 cm and 3 cm.

(67) A light emitting device 2 may for example comprise only approximately one to 9 light emitting elements 2a, 2a, 2b, etc. Optionally, a light emitting device 2 may comprise between approximately 50 and 1000 light emitting elements 2a, 2a, 2b, etc.

(68) FIG. 4b is a front exploded view of a portion of the light emitting element 2a of FIG. 4a. Particularly, the DFB grating 22 with a grating constant Λ is illustrated with an overlayer of an organic laser material 23 in an exploded view, for better understanding of the grating structure 22. The grating structure 22 may comprise rectangular projections or teeth each having a length 26 and a width 27. The length 26 of the grating structure 22 may correspond with the width 24 of a light emitting element 2a. The width 27 of the grating structure 22 may be homogeneous or varying throughout a light emitting element 2a. The width 27 of the grating structure 22 is determined by the grating constant Λ.

(69) FIG. 5 is a front exploded view of a portion 140 of an on-chip optical absorption sensor comprising the light emitting element 2a of FIG. 4a. The sandwich structure S4 shown in FIG. 5 may be a cut out of the sandwich structure S3 of the on-chip optical absorption sensor 120 of FIG. 3. The cut out may be along the cross section line VV′ of a single light emitting element 2a as indicated in FIG. 3.

(70) Alternatively, the sandwich structure S4 shown in FIG. 5 may also be considered a complete on-chip optical absorption sensor 140, if the light emitting device does not comprise an array of light emitting elements 2a, 2b, 2c, etc. but only one single light emitting element 2a.

(71) FIG. 6 is a front exploded view of an on-chip optical absorption sensor 150 according to another aspect. The sandwich structure S5 displayed in FIG. 6 will be described the following.

(72) The difference between the sandwich structure S5 of FIG. 6 and S1 of FIG. 1 are tilted light detector layers A.sub.4, A.sub.5. In other words, the normal directions N.sub.4, N.sub.5, of the light detector layers A.sub.4, A.sub.5 are not parallel to the first direction D and second direction U and the vertical axis z. The light detector layers A.sub.4, A.sub.5 are tilted at angles α, τ for example with respect to the light emitting layer A.sub.2 and the horizontal direction y of FIG. 6. In other words, the light L.sub.D, L.sub.U being emitted from the light emitting device 2 along the directions D and U does generally not impinge on the light detector layers A.sub.4, A.sub.5 at an angle of 90°. As a result of this configuration, multiple reflections between the surfaces of the light detector layers A.sub.4, A.sub.5 and the light emitting layer A.sub.2 may be avoided. The angles π, τ may differ from each other, as optical elements and/or a sample chamber 31 and/or a sample 1 may deviate or change the direction of the light L.sub.D in the first direction D, whereas the light L.sub.U emitted in the second direction will generally not deviate or change direction or at a different angle.

(73) The angles α, τ may for example be between approximately 0.2° and 7°, optionally between approximately 0.5° and 5°, more optionally between approximately 1° and 4°.

(74) FIG. 7 is a front exploded view of an on-chip optical absorption sensor 160 according to another aspect. The difference between the sandwich structure S6 of FIG. 7 and S1 of FIG. 1 is the light emitting device 2 and the sample chamber 31 being integrally formed with each other in the present sandwich structure S6. In other words, the sample chamber 31 is connected to the light emitting device 2 in such a way that they cannot be separated from each other. In FIG. 7, the light emitting layer A.sub.2 and the sample chamber layer A.sub.31 are not spaced apart by a substantial distance from each other. However, a spacer may be included to maintain a distance between the light emitting layer A.sub.2 and the sample chamber layer A.sub.31.

(75) The light emitting device 2 may degrade after a short time period due to organic lasing material having only a short lifetime in the operation mode. Similarly, it may be required that a sample chamber 31 may only be used a single time, as for example a cleaning procedure would be too complicated and time consuming to ensure that a sample 1 is not contaminated with specimens of a previously used sample 1. If the lifetime of a light emitting device 2 and the lifetime of a sample chamber 31 are both approximately in the range of an operation time of a single use, it may be advantageous to provide the light emitting device 2 and the sample chamber 31 as integrally formed single use elements. The sandwich structure S6 of may be configured such that the light detectors 4, 5 are for permanent use, for example permanently attached to the mount 8, and the unit of the sample chamber 31 being connected to the light emitting device 2 may be replaced like a cassette before every new measurement. At least one filter 6, 7 may be included in the sandwich structure S6 for permanent and/or multiple and/or single use. At least one filter element may also be integrally formed with the light emitting device 2 and/or the sample chamber 31.

(76) Alternatively, the entire sandwich structure S6 may be configured for single use. Hence, all elements, such as at least the light detectors 4, 5, the light emitting device 2 and the sample chamber 31 may be integrally formed with each other and configured for single use.

(77) Alternatively, the entire sandwich structure S6 may be configured for permanent or at least for multiple use while at least two elements are integrally formed with each other. It may for example be practical to produce the light emitting device 2 and the sample chamber 31 as a single piece by means of producing a multilayer including 3D printing or layer-by-layer generation ((spin) coating, laminating, etc.).

(78) FIG. 8 is a front exploded view of an on-chip optical absorption sensor 170 according to another aspect. The sandwich structures S7A and S7B each refer substantially to the sandwich structure S1 of FIG. 1. Each sandwich structures S7A and S7B can be considered a sandwich structure unit. Optional filter elements 6, 7 are not illustrated in FIG. 8. The two sandwich structure units S7A and S7B are combined to form a sandwich structure S7 hence comprising two units.

(79) Similarly, as in the case of FIG. 3, where different microfluidic channels 32a, 32b, 32c are provided, a sandwich structure having more than one unit may be very efficient, as different samples 1A, 1B may be investigated at the same time. The aspects of the sandwich structures S3 of FIG. 3 and S7 of FIG. 8 may optionally be combined.

(80) The sandwich structure S7 may for example be configured to receive two samples 1A, 1B, of which the concentration of the same specimen should be determined at the same time. In that case, the light emitting devices 2A, 2B may emit light having the same wavelength λ.sub.1=λ.sub.2.

(81) Alternatively, the sandwich structure S7 may be configured to receive two identical samples 1A, 1B, wherein the concentration of different specimens should be determined at the same time. In that case, the light emitting devices 2A, 2B may emit light having a different wavelength λ.sub.1≠.sub.2, as two different specimens absorb at different wavelengths due to their different molecular structures.

(82) Alternatively, in a configuration in which aspects of the sandwich structure S3 are combined with aspects of the sandwich structure S7, at least two sandwich structures S7A, S7B including at least two light emitting devices 2A, 2B are provided, wherein each light emitting device 2A, 2B comprises light emitting elements 2a, 2b, 2c etc. as indicated in FIG. 3. These light emitting elements 2a, 2b, 2c etc. may emit light L.sub.D, L.sub.U at wavelengths λ.sub.1, λ.sub.2, λ.sub.3 which are different from each other, such that the concentration c of different specimens in one sample 1A in one sample chamber 31A of one sandwich structure S7A may be determined. At the same time, the concentration c of the same or other specimens of the same or of a different sample 1B may be determined in the other sample chamber 31B of the other sandwich structure S7B.

(83) The sandwich structures S7A, S7B have substantially the same geometry in the on-chip optical absorption sensor 170. Alternatively, other geometries and configurations, as for example described herein, may be adopted in the present case.

(84) The on-chip optical absorption sensor 170 may hence be applied for multiplexed point-of-care testing.

(85) FIG. 9 is a schematic view of a system 1000 according to an aspect comprising an exemplary on-chip optical absorption sensor 110 according to FIG. 2 and a computer 1100. The computer 1100 is configured to receive data from the on-chip optical absorption sensor 110, particularly the intensities, I and I.sub.0 to determine the concentration of one or more specimens in one or more samples.

(86) The computer 1100 may comprise a computer program product which when loaded and run cause the computer to perform steps to determine the concentration of one or more specimens in one or more samples. The computer 1100 may cause the measurement to be started, the pump laser to emit pump radiation 11 to excite the laser to emit light L.sub.D, L.sub.U, to cause the light detectors 4, 5 to detect the intensities I and I.sub.0 of the incident light L.sub.14, L.sub.15, to cause the light detectors 4, 5 to transmit the data related to the intensities I and I.sub.0 and to cause the computer to calculate or determine the concentration of the one or more specimens in the one or more samples 1 according to:

(87) $c = - \ln (k_{I} \frac{I}{I_{0}}) / (d {.Math.}^{*})$
wherein 1 is an attenuated intensity of the propagated light L.sub.P detected by the first light detector 4, I.sub.0 is a reference intensity of the light L.sub.U emitted in the second direction U detected by the second light detector 5, ε* is an extinction coefficient of the specimen at a wavelength λ of the light, c is a molar concentration of the specimen in the sample 1, d is a thickness of the sample 1 in the first direction D and k.sub.I is a factor taking into account a the relation between the intensities I.sub.D, I.sub.U of light L.sub.D, L.sub.U being emitted into the first D and the second directions U, respectively, according to

(88) $k_{I} = \frac{I_{D}}{I_{U}} .$

(89) The above operations may also be performed by more than one computer 1100. For example, the pump laser may be operated through an external system. The computer 1100 and the on-chip optical absorption sensor 110 may be a handheld device.

(90) The term “computer” may herein refer to any unit which is configured to perform calculations, for example particularly a microcontroller, a processor, or the like.

(91) FIG. 10 is a front exploded view of an on-chip optical absorption sensor 180 according to another aspect. In the illustrated example, a reference holder 3′ is provided between the light emitting device 2 and the second light detector 5. According to this aspect, also a reference chamber 31′ can be positioned between the light emitting device 2 and the second light detector 5. The reference chamber 31′ may be different from the sample chamber 31, however, according to a preferred aspect, the reference chamber 31′ is substantially identical to the sample chamber 31, with respect to geometry, optical and physical properties and composition. The reference chamber 31′ comprises a reference chamber volume 34′, which is also preferably substantially identical in shape, particularly in thickness along the first direction D, with the chamber volume 34 of the sample chamber 31.

(92) The reference chamber volume 34′ may be filled at least partially with a reference substance 1′, for example a solvent that is also present in the sample 1 for example for dissolving or dispersing the specimen. Hence, the reference measurement, i.e. the measurement of I.sub.0, may already take into account attenuation effects. Such attenuation effects may origin from the material from which the sample chamber 31 and the reference chamber 31′ is made of, reflections on the surfaces of the sample chamber 31 and the reference chamber 31′, the solvent absorbance and/or scatter effects of the solvent. Basically, the extinction of the solvent and/or the sample chamber 31 and potentially other optical attenuation effects arising (and not originating from the specimen), may be determined and substantially isolated from the pure extinction of the specimen.

(93) Instead of a sample chamber 31 and a reference chamber 31′, a sample 1 and a reference substance 1′ may also be supported by microscope slides.

(94) Further, filter elements, which are not shown in FIG. 10, may be added at any one or two positions between the light emitting device 2 and the first 4 and/or second light detector 5 to avoid that the first 4 and/or the second 5 detectors are exposed to the pump radiation 11. However, a sample chamber 31 and a reference chamber 31′ and/or a sample 1 and/or a reference substance 1′ may also substantially filter pump radiation 11, particularly in the UV or near-UV region.

(95) The light emitting device 2 may be formed integrally with either one or both of the sample chamber 31 and a reference chamber 31′. In general, all aspects which apply to the sample chamber 31 may also apply to the reference chamber 31′.

(96) The empty reference chamber 31′ and the empty sample chamber 31 may be positioned inside the on-chip optical absorption sensor 180 during a calibration measurement as described above. However, at least one of the reference chamber 31′ or the sample chamber 31 may also be removed from the on-chip optical absorption sensor 180 during a calibration measurement.

(97) Point-of-care testing (POCT) may provide a diagnostic test at or near the time and place a patient is admitted. POCT uses a concentration of an specimen/analyte to provide the user with information on the physiological state of the patient and/or a biological system and/or an ecosystem. An analyte, for example a marker, is a chemical or biological specimen, which is analyzed using a certain instrument such as a spectrometer or an on-chip optical absorption sensor as described herein. While point-of-care testing is the quantification of one single analyte from one in vitro (e.g. blood, plasma or urine) sample, multiplexed point-of-care testing is the simultaneous on-site quantification of various analytes from a single sample. Multiplexed point-of-care testing (xPOCT) is hence a more complex form of point-of-care testing (POCT), or bedside testing.

(98) Processing of one biological sample to yield multiple biomarker results allows for POCT testing to be done for patients who may have conditions that require the confirmation of multiple biomarkers and tests before diagnosis (e.g. many types of cancers). xPOCT has important emerging applications in resource-limited settings, (e.g. in the developing countries, in doctor's practices, or at home by non-experts) xPOCT has recently become more important for in vitro diagnostics.

(99) The term “array” affiliated with the reference numeral 21 generally refers herein to the array comprising columns and rows of light emitting elements 2a, 2b, 2c, etc.

(100) The term “grating structure” affiliated with the reference numeral 22 generally refers herein to a structure or lattice characterized by the grating constant Λ. The term “grating structure” is not to be confused with the “array”.

(101) A concentration of a specimen may be derived directly from a measured (attenuated) intensity of a native sample according to the Lambert Beer law. Alternatively, it may be required to add a marker or a reagent into the sample which substantially reacts with the at least a portion of the specimen in the sample. The result of this reaction may then be detected as an (attenuated) intensity and may hence act as an indicator for the concentration of the specimen.

(102) In the following, some definitions which are used herein are given.

(103) A specimen, i.e., analyte, may be a compound, for example a certain type of molecule. A sample may be biological and/or chemical substance which may comprise several specimens. The sample may comprise a mix of molecules, such as for example proteins, water, lipids and ions. The sample may for example be a sample of blood, a sample of waste water or a sample of foods.

(104) Particularly, a period of time required for a single measurement is between approximately 0.5 s and 20 minutes, particularly between approximately 3 s and 30 s, more particularly between approximately 5 s and 10 s.

(105) Pump lasers may be for example UV-lasers or UV near lasers, i.e. lasers which emit the pump light in a wavelength region overlapping the UV region. Ultraviolet (UV) light may in general have a wavelength between approximately 10 and 400 nm. The pump light may have a wavelength in this range, particularly the pump light also includes wavelengths near the UV region (near-UV region). Preferably, the pump radiation comprises light with wavelengths between approximately 350 nm and 490 nm. It is important to choose a wavelength range at which a certain power can be reached to achieve the stimulated emission in the organic laser. Particularly, Blue-Ray Laser-Diodes preferably emitting light at a wavelength around approximately 405 nm may be used. Pump lasers may also be pulsed lasers.

(106) Organic laser materials may comprise for example the following dyes: ADS233YE, ADS100RE, ADS133YE, ADS232GE, ADS145UV.

(107) At least some of the widths of the layers particularly range around approximately 10 mm to 300 mm. At least some of the lengths of the layers particularly range around approximately 10 mm to 300 mm. The thickness defined by the distance between the upper surface of the upper most layer to the lower surface of the lower most layer (for example from first to second light detector) in the first/second directions may range around approximately 1 mm and 30 mm. The thickness also depends on the number of layers used in the sandwich structure and/or the number of sandwich units used in a combined sandwich structure. As an example, the size of an on-chip optical absorption sensor is approximately 76 mm×26 mm×5 mm.

(108) Particularly, the weight of an on-chip optical absorption sensor is between approximately 3 g and 100 g, particularly between approximately 10 g and 50 g, and more particularly between approximately 20 g and 30 g, such as for example approximately 25 g.

(109) The sample chamber 31 and/or the reference chamber 31′ may comprise at least any one of: glass, Zink Selenide, Calcium Fluoride, Sapphire, BK7 glass, Silicon (n- or p-type), a polymer and/or an organic compound, for example a UV absorption organic layer over the surface.

(110) A light emitting device, as far as it is not configured to emit coherent light, might for example be a flexible LED panel, a fiber optic or any light source that can emit light, particularly monochromatic and which can be provided as a thin layer. Even some laser systems, such as organic-based microcavity lasers, may emit light which is not considered coherent light herein (described in more detail, as follows).

(111) Particularly, coherent light is considered coherent in terms of spatial and temporal coherency, i.e. substantially monochromatic light with wave trains having substantially parallel wave fronts. Herein, coherent light is considered coherent when the coherence length of the light is exceeding a range between approximately 1 cm to approximately 10 cm, particularly when the coherence length of the light is exceeding approximately 1 m and even more particularly when the coherence length of the light is exceeding approximately 100 m.

(112) Particularly, light which has a coherence length of less than 1 cm may be considered non-coherent, i.e. not coherent, herein.

(113) For comparison, multimode helium-neon lasers typically have a coherence length of approximately 20 cm, while the coherence length of single-mode lasers can exceed approximately 100 m. Semiconductor lasers can reach approximately some 100 m, but small, inexpensive semiconductor lasers have shorter lengths, such as for example approximately 20 cm. Single mode fiber lasers with linewidths of a few kHz can have coherence lengths exceeding 100 km. For example, the spatial coherence length of an europium complex-based OLED may be in the μm range, it may range for example between approximately 1.7 μm to 1.9 μm.

(114) All examples and aspects described herein may be realized with a coherent and a non-coherent light emitting device. A coherent light emitting device emits substantially coherent light and a non-coherent light emitting device emits substantially non-coherent light.

(115) There are cases, in which lasers emit non-coherent light in the sense of the above definition. For example, some free running diode lasers may have a coherence length of less than 1 mm. Organic-based microcavity lasers may for example have a coherence length in the μm range, such as for example approximately 45 μm (Camposeo, Andrea & Persano, Luana & Del Carro, Pompilio & Papazoglou, Dimitris & Stassinopoulos, Andreas & Anglos, Demetrios & Pisignano, Dario. (2008). Longitudinal coherence of organic-based microcavity lasers. Optics express. 16. 10384-9. 10.1364/OE.16.010384.).

REFERENCE SIGNS

(116) TABLE-US-00001 1; 1A; 1B; 1C Sample 1′ Reference substance 2; 2A, 2B (Coherent) light emitting device 2a, 2b, 2c, 2d; (Coherent) light emitting elements arranged in at least a 2e, 2f, 2g, 2h, 2i column and two rows 3 Sample holder 3′ Reference holder 4 First light detector 5 Second light detector 6 (first) Filter element 7 (second) Filter element 8 Mount 9 Cable for data transfer and/or energy supply 10 Port for filling the volume of the sample chamber with a sample 11 Pump radiation of a pump laser 21 Array of (coherent) light emitting elements having at least one column and at least two rows 22 (DFB) grating or grating structure 23 Organic laser material 24 Width of a grating 25 Length of a grating 31; 31A, 31B Sample chamber 31′ Reference chamber 32 Microfluidic channel structure 32a, 32b; 32c Microfluidic channel 33 Holding elements for holding the sample or the sample chamber 34 Chamber volume in sample chamber 34′ Reference chamber volume 100; 110; 120; Embodiments of on-chip optical absorption sensors 140; 150; 160; 170; 180 1000 System comprising an on-chip optical absorption sensor and a computer 1100 Computer α Angle between second light detection layer and (parallel of) light emitting layer in one dimension A.sub.2; A.sub.2A; A.sub.2B Light emitting layer A.sub.31; A.sub.31A; A.sub.31B Sample chamber layer A.sub.31′ Reference chamber layer A.sub.4, A.sub.4A, A.sub.4B First light detection layer A.sub.5; A.sub.5A; A.sub.5B Second light detection layer A.sub.6, A.sub.7 Filter layers β Surface to surface distance between two columns of (coherent) light emitting elements c.sub.1, c.sub.2; c.sub.3 columns d; dA; dB Thickness of the sample in the first direction d.sub.v Thickness of the chamber volume in the first direction D; D.sub.1; D.sub.2 First direction (e.g. vertically downwards) Δ Surface to surface distance between two (coherent) light emitting elements in one column, i.e., distance between two rows γ.sub.5-6 Surface to surface distance between second light detector and (first) filter element γ.sub.5-2 Surface to surface distance between second light detector and (coherent) light emitting device γ.sub.2-31 Surface to surface distance between (coherent) light emitting device and sample chamber γ.sub.31-7 Surface to surface distance between sample chamber and (second) filter element γ.sub.31-4 Surface to surface distance between sample chamber and first light detector γ.sub.7-4 Surface to surface distance between (second) filter element and first light detector Λ Grating constant of the grating or DFB grating structure / Intensity of the reference light /.sub.0 Intensity of the propagated light, particularly intensity of the attenuated light L.sub.D (coherent) light emitted in the first direction with intensity I.sub.D L.sub.I4 Incoming light at the first light detector L.sub.I5 Incoming light at the second light detector L.sub.U (coherent) light emitted in the second direction with intensity I.sub.U L.sub.p Light emitted in the first direction and having propagated through the sample holder, particularly attenuated light L.sub.S Light emitted in the second direction and having propagated through a solvent in the reference holder, particularly attenuated light λ.sub.1 First wavelength of (coherent) light emitting element λ.sub.2 Second wavelength of (coherent) light emitting element λ.sub.3 Third wavelength of (coherent) light emitting element λ.sub.4 Fourth wavelength of (coherent) light emitting element λ.sub.11 Wavelength of pump radiation N.sub.2 Normal of light emitting layer N.sub.31 Normal of sample chamber N.sub.4 Normal of first light detector N.sub.5 Normal of second light detector N.sub.6 Normal of (first) Filter element N.sub.7 Normal of (second) Filter element r.sub.1, r.sub.2; r.sub.3 rows S1; S2; S3; S4; Embodiments of sandwich structures S5; S6; S7, S7A, S7B τ Angle between first light detection layer and (parallel of) light emitting layer in one dimension U; U.sub.1; U.sub.2 First direction (e.g. vertically upwards) V.sub.S Sample volume

On-chip absorption sensor for determining a concentration of a specimen in a sample

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G01N21/253

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G01N2015/0053

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Abstract

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Description