Multi-channel interferometric module, interferometry system and miniaturized chemical laboratory based on a single multi-mode interference coupler

Abstract

A multi-channel interferometric module, comprising a plurality of input waveguides in conjunction with a single multi-mode interference coupler, wherein a fan-in and a fan-out section are provided for input fields to enter and leave said multi-mode interference coupler and wherein the plurality of input waveguides is three or more waveguides.

Description

[0001] Multi-channel interferometric module , interferometry system and miniaturized chemical laboratory based on a single multimode interference coupler

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention relates to a multi-channel interferometric module , in particular comprising a plurality of input waveguides . Furthermore , the invention relates to an interferometry system and a miniaturi zed chemical laboratory .

[0005] BACKGROUND

[0006] Optical structures comprising optical fibers are widely used in technics and science to detect phase shi fts between two or more fields using interferometric working principles .

[0007] In a fiber Mach-Zehnder- Interf erometer, light is firstly split in two by a beam splitter, one copy then travels through a reference and another down a sensor fiber . They are then recombined by a beam combiner . For this , two 2x2 couplers are used . A mechanical excitation acting on the sensor fiber causes an extension or compression of the fiber, which in turn causes a change in the time the light needs to travel through the sensor fiber . Finally, the di f ferences in said time cause a change in the brightness of the interference signal .

[0008] However, a Mach-Zehnder- Interf erometer is not able to retrieve the phase di f ference between the arms beyond the +- pi / 2 range . Moreover, only monotonic variations in time of the phase can be monitored .

[0009] Phase-shi fting interferometers can solve this problem . They deploy more complex beam combiners and thus accomplish phaseshi ft interferometry . ABCD modules or ABCD combiners are phase-shi fting interferometers and achieve the phase-shi ft interferometric ef fect by using a cascade of 1X2 and 2x2 couplers and a pi / 2 phase retarder . Thus , the phase over the full 0-2pi range can be determined . This comes , however, at the expense of a much more complex PIC ( Photonic Integrated Circuit ) component having a large footprint .

[0010] In the pending patent application DE 10 2023 102 842 . 1 a multi-channel interferometric module is disclosed . This module has a plurality of input waveguides in conj unction with multiple evanescently coupled waveguides which form a coupling region for the multiple input fields of the input waveguides . In this coupling region, the use of narrow waveguides , which signi ficantly extend the mode field into the surroundings , matched with a small waveguide-to-waveguide separation, allows for a signi ficant NNN (next-nearest neighbor ) coupling . This is suf ficient to establish a robust phase retrieval across the 0-2pi range . This arrangement does not need the complex structural arrangement of a cascade of 1X2 and 2x2 couplers and a pi / 2 phase retarder . Yet , this arrangement is still complex in its layout and in its production, as it , for example , requires the manufacturing of arrays of waveguides .

[0011] SUMMARY

[0012] The obj ective of the invention is therefore to provide an improved and modular multi-channel interferometric module , which allows reliable phase shi ft measurements in the full 0- 2pi range , which is less complex in its layout and its production and therefore also less prone to manufacturing defects .

[0013] Another obj ect is to provide an interferometry system . With respect to the muti-channel interferometric module , the obj ective is solved by a multi-channel interferometric module which comprises a plurality of input waveguides in conj unction with a single multi-mode interference coupler, wherein a fan-in and a fan-out section are provided for input fields to enter and leave said multi-mode interference coupler, and wherein the plurality of input waveguides is three or more waveguides .

[0014] With " input waveguides" the input waveguides of the multimode interference coupler are denoted .

[0015] Preferred embodiments are subj ect of the dependent claims .

[0016] The invention is based on the consideration that it would be desirable to provide a versatile and compact interferometry module , especially a PIC ( Photonic Integrated Circuit ) block, which allows phase shi fts in the full 0-2pi range , and which is less complex in its layout and its production .

[0017] It was found that a multi-channel interferometer can be realized by means of a single multi-mode interference coupler . This setting signi ficantly simpli fies the layout of previous solutions to the problem of building a PIC multi-channel interferometer . For this , the requirement is that the multimode interference coupler must support at least NxN transverse modes .

[0018] Compared to the multi-channel interferometers based on arrays of waveguides , the interferometric function is now accomplished by a single multi-mode interference coupler slab waveguide and does not require the manufacturing of arrays of waveguides , thus reducing further the degrees of freedom of the device .

[0019] Summari zed, the invention replaces the array of strongly coupled waveguides with a multi-mode interference coupler, which can be seen as the upper limit for strongly coupled waveguide arrays . Thus , the proposed invention requires j ust a multi-mode interference coupler and a fan-out section to measure the relative phase and amplitude of N>2 input waveguides . Therefore , the cascades of couplers and phase shi fters required by a conventional multi-channel PIC interferometer are not required any more , thus reducing the complexity of the interferometer signi ficantly . This results in a small footprint , which also reduces the ef fect of thermal gradients across the device . Said thermal gradients pose a real stability problem for interferometers , often requiring expensive thermal conditioning systems .

[0020] Existing couplers enabling phase-shi fting interferometry and thus removing the phase ambiguity of 2x2 couplers are designed for j ust two input channels . Before , the unambiguous phase retrieval of many channels was possible only with discrete beam combiners .

[0021] In a preferred embodiment , the fan-out section comprises a photonic lantern .

[0022] In particular, the multi-mode interference coupler and the photonic lantern combination accomplishes the function which is usually performed by a cascade of PIC couplers and phase shi fters , thus requiring a much smaller area of the PIC .

[0023] The photonic lantern comprises preferably a number of waveguides which is equal to or larger than the squared number of input waveguides , as for a N-channel interferometer (with N being the number of input waveguides ) , as the requirement is that the multi-mode interference coupler must support at least NxN transverse modes .

[0024] Advantageously, the waveguides of said photonic lantern are arranged with increasing inter-waveguide separation . At a certain separation, the waveguides can be considered as being in complete isolation .

[0025] In a preferred embodiment of the invention, the photonic lantern is designed as follows : the photonic lantern is formed by NxN=9 slot waveguides of 341 nm width and 200 nm height with N being the number of input waveguides .

[0026] At the matching interface of the photonic lantern with the multi-mode interference coupler, the waveguides form preferably a continuum .

[0027] As the distance Z from the matching interface increases , the waveguides traj ectories in the transverse dimension X are given by the expression :

[0028] Xn(Z) = ndQ

[0029] A

[0030] Wherein in one preferred embodiment of the invention n e [—4, -3, —2, -1, 0, +1 + 2, +3, +4] and Zohas been chosen to be 18 . 2 pm . Zocan be related to the length of the photonic lantern Lo, the input period d0and the output period d according to :

[0031] In this preferred embodiment , the reference length Lohas been chosen to be 50 pm, such that the photonic lantern fulfills an adiabatic transition condition .

[0032] In a preferred embodiment , an input period d0of a waveguide array of the photonic lantern is 0 , 341 pm and / or an output period d±of the waveguide array of the photonic lantern is 1 , 175 pm . With this separation, the waveguides can be considered as isolated .

[0033] The choice of the position of the N input waveguides and the length of the multi-mode interference coupler and the fan-out section ( e . g . , photonic lantern) uniquely determine a calibration matrix that allows one to retrieve the relative phase of the light guided by the input waveguides from a measurement of the optical power carried by the NxN output waveguides . Di f ferently from standard 2x2 couplers , the above-described component and the associated phase retrieval algorithm is able to determine the phase in the 0-2pi range .

[0034] Preferably, the cores of said input waveguides are and / or the core of a slab waveguide of the multi-mode interference coupler is , at least partially, embedded in an embedding body .

[0035] Such an embedding provides protection for the waveguides and / or the slab waveguide .

[0036] Advantageously, said embedding body is made of SiO2.

[0037] SiO2provides a highly confined optical mode adequate for butt coupling .

[0038] In a preferred embodiment , the cores of said input waveguides are and / or the core of the slab waveguide of the multi-mode interference coupler is made , at least partially, of SiN .

[0039] By using SiN, a high nonlinear refractive index and a low- loss property can be achieved .

[0040] Although the PIC component can be applied to any integrated optics platform, the preferred implementation is with the SiN-SiO2platform . Because of the relatively high refractive index contrast between core and cladding it is possible to confine light more tightly and achieve a smaller footprint for the device and its applicability to the visible wavelength range .

[0041] Furthermore , center lines of the input waveguides are preferably spaced equidistantly from each other and / or one center line of one waveguide preferably coincides with a longitudinal center line of the slab waveguide of the multi-mode interference coupler .

[0042] In a preferred embodiment , N=3 and the waveguides centers are located at the coordinates [ - 0 , 697 , 0 , + 0 , 697 ] pm, measured from the longitudinal center line of the slab waveguide .

[0043] Such a fan-in structure for the input waveguides limits the crosstalk between the input channels to a negligible level .

[0044] In a preferred embodiment , at least one input waveguide has preferably a width of 341 nm and / or a height of 200 nm .

[0045] Advantageously, the multi-mode interference coupler has a length of 1 , 76 pm .

[0046] In a preferred embodiment , the multi-mode interference coupler supports NxN=9 transverse modes and is further 3075 nm wide and 200 nm high . The speci fic length of the multi-mode interference coupler depends on the number of the input channels and the actual shape of the photonic lantern in order to achieve an optimal performance .

[0047] In a preferred embodiment , the multi-channel interferometric module comprises a light-out coupler .

[0048] The output coupling of the light from the PIC ( Photonic Integrated Circuit ) can be either in-plane or out-of-plane . The former is reali zed by terminating the output waveguides at the edge of the PIC itsel f . In this configuration an array of optical fibers or detectors may be butted up to the individual output waveguides and the power in each waveguide measured in situ ( on-chip ) or elsewhere . The out-of-plane configuration may be reali zed with a di f fraction grating coupler whose parameters determine the direction and ef ficiency of the di f fraction out of the plane . In this case , an array of pixels (photo detectors ) may sit directly above the PIC in order to measure the power in each waveguide . From a technological point of view, the in-plane option is preferred i f the light has to be coupled to an array of optical fibers . The out-of-plane option is preferred in case the detectors are to be integrated on the PIC itsel f .

[0049] Preferably, the multi-channel interferometric module comprises a detection device consisting or comprising of an array of photo detectors .

[0050] Photodetectors convert the received light into electrical signals from which information is extracted .

[0051] In a preferred embodiment , for each waveguide a photo detector is provided .

[0052] With this , a more precise extraction of the electrical signals in the waveguides can be achieved .

[0053] Advantageously, the multi-channel interferometric module is configured for an operational wavelength between 850 nm and 950 nm, especially 895 nm .

[0054] Nevertheless , the device is designed to operate with a light source at a wavelength between 850 and 950 nm, i f needed . Though, other PIC platforms and wavelengths are also possible , but require a rescaling of the dimensions .

[0055] Preferably, the multi-channel interferometric module is built as a photonic integrated chip ( PIC ) block .

[0056] Thus it can be used in more complex PICs requiring multichannel interferometric functionalities . With respect to the interferometry system, the obj ective is solved by an interferometric system comprising an interferometric module described above and a phase retrieval algorithm configured to determine a phase-shi ft . The phase retrieval algorithm is based on a digital microprocessor capable of multiplying a vector, whose elements contain the digiti zed photocurrent of the output photodetectors , by the pseudo-inverse of the N' x N calibration matrix of the interferometer and thus determines the mutual coherence function of the light present at the inputs of the input waveguides of the interferometer .

[0057] The pseudo-inverse of the calibration matrix of the proposed interferometric PIC building-block allows the retrieval of the photometric signal required for the compensation of the Mach-Zehnder- Interf erometer dri ft . The calibration matrix relates the input coherence function (phase and power of the input channels ) to the power carried by the output waveguides of the device . The preferred definition of the calibration matrix of the interferometer and its experimental evaluation are described in detail in A. Saviauk et al . Applied Optics , vol . 52 , p . 4556 ( 2013 ) .

[0058] A possible application of the proposed multi-channel interferometric module is within a miniaturi zed lab-on chip / miniaturi zed chemical laboratory comprising the interferometric module described above and comprising a light source . The lab-on-chip consists or comprises of 1 ) a light source , 2 ) a PIC ( Photonic Integrated Circuit ) , 3 ) a detector array and 4 ) a microfluidic layer . The light source is a laser diode emitting light at the design wavelength of the PIC .

[0059] BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In the following, the invention will be described in further detail with reference to the accompanying drawings , wherein there is shown : FIG. 1 A plan view of a multi-channel interferometric module

[0061] FIG. 2 A plan view of input waveguides and a multi-mode interference coupler

[0062] FIG. 3 A cross section of FIG. 2 along line A-A

[0063] FIG. 4 A cross section of FIG. 2 along line B-B

[0064] FIG. 5 A plan view of a photonic lantern

[0065] FIG. 6 A plan view of an application example (here: a miniaturized chemical lab)

[0066] Identical parts are labelled by the same reference signs.

[0067] DETAILED DESCRIPTION

[0068] In FIG. 1 an interferometry module 2 is shown which is built as a Photonic Integrated Circuit (PIC) building block 4 and comprises a multi-channel interferometric module 6 and a module in which a phase retrieval algorithm 60 is implemented.

[0069] As illustrated in FIG. 1, the interferometric module 6 comprises 6 a number of functional blocks: a plurality of input waveguides (in this case three) 10, a MMI coupler (multi-mode interference coupler) 20, a fan-out section 30, which is realized in this embodiment as a photonic lantern, output couplers 40, a detection system 50 comprising an array of light detectors 52 and a phase retrieval algorithm 60 implemented in a suitable module.

[0070] In the preferred embodiment shown in FIG. 1, three input waveguides 10 are used and these input waveguides are connected to the MMI coupler 20.

[0071] The fan-out section 30 is built as a photonic lantern, which in the direction of light passage is arranged behind the MMI coupler 20 . In the photonic lantern 30 , in said direction of the light passage , the separation between neighboring waveguides 12 increases so that the light in each waveguide 12 no longer interact with each other and the waveguides can be treated as individual isolated waveguides .

[0072] The function of the photonic lantern 30 is to allow a lossless transition from the MMI coupler 20 to the bundle of isolated single-mode waveguides , which are required in order to measure the output power .

[0073] The interferometric module 6 furthermore comprises a light out-coupler 40 . In the direction of light passage , after the light out-coupler 40 , the detection system 50 is arranged . The detection system 50 comprises an array of photo detectors 52 ( of which only a few are labelled by the corresponding reference numerals ) , wherein for each of the waveguides 12 a separate photo detector 52 is arranged .

[0074] The function of the light-out coupler 40 is to allow the light in each waveguide 12 to be measured . Several options are available :

[0075] For in-plane measurement of the light , the out-coupler is removed, the waveguides are extended to the edge of the PIC 4 and, as the array of light detectors 52 of the detection system 50 , a linear array of photodiodes 52 is placed at the termination of the waveguides 12 . Each pixel measures the light in each waveguide individually . Out-of-plane measurement requires an out-coupler, and a standard solution to this is to use an in-plane grating to redirect the light in the individual waveguides out of the chip plane and in a particular direction relative to the said plane . The ef ficiency of this solution is dependent on the grating design .

[0076] The preferred output configuration consists of a series of grating couplers , so that the array of photodiodes 52 can be manufactured on top of a PIC 4 , in case C-MOS compatible PIC fabrication technology ( e . g . , Silicon Nitride-Silica platform) is employed . In the direction of light passage , the light-out coupler 40 is arranged behind the photonic lantern 30 .

[0077] The interferometry module 2 is further built as a PIC building block 38 .

[0078] A fan-in section 14 is indicated in FIG . 1 , which is required for the input waveguides 10 in order to limit the crosstalk between the input channels to a negligible level .

[0079] Also shown in FIG . 1 is a module hosting a phase retrieval algorithm 60 . The phase retrieval algorithm 60 receives signals from the detection system, i . e . , from the light detectors 52 . With the phase retrieval algorithm 60 , phase-shi fts between light travelling along di f ferent waveguides are detected .

[0080] The phase retrieval algorithm 60 allows a more accurate determination of the phase . Moreover, i f the interferometry system 2 is to be inserted in a lab-on-chip for the measurement of refractive index changes through evanescent sensing of sample windows , then the complex refractive index of the tested sample can be retrieved ( refractive index and attenuation coef ficient ) .

[0081] Also , the interferometric module 2 and the associated phase retrieval algorithm 60 allow for the measurement of the power carried by each input waveguide 10 , so that variations of the power in each interfering input channel can be removed from the estimation of the phase signal . Typically, power di f ferences in either arm of a standard interferometer will greatly af fect the visibility of the fringes of the interferogram .

[0082] The preferred operating wavelength for the interferometry system 2 shown is 895 nm . Nevertheless , the device is designed to operate with a light source at a wavelength between 850 and 950 nm, i f needed . Other PIC platforms and wavelengths are also possible but require a rescaling of the dimensions .

[0083] In FIG . 2 , a detail of FIG . 1 showing the fan-in section 14 and the MMI coupler 20 is depicted, wherein in FIG . 3 a cross section along line A-A of FIG . 2 is shown and in FIG . 4 a cross section along line B-B of FIG . 2 shown .

[0084] The input waveguides 10 are guiding the light which carries the amplitude / phase information that is to be retrieved by the interferometry system 2 . Their number is N > 2 (N is denoting the number of input waveguides 10 in the following) . The location of the input waveguides 10 is chosen by calculating an interferometric calibration matrix of the component for every possible input configuration and component length and choosing then the input configuration and component length corresponding to the minimal condition number of said interferometric calibration matrix .

[0085] In this embodiment of the invention N=3 , and the center lines 11 , 13 and 15 of the waveguides 10 are located at the coordinates [ - 0 . 697 , 0 , + 0 . 697 ] pm measured from a longitudinal center line 17 of the slab waveguide of the MMI coupler 20 . In this embodiment , a center line of one of the input waveguides 10 is aligned with a center line of the slab waveguide of the MMI coupler 20 . In the direction of light passage , the input waveguides 10 have a width 22 of 341 nm and a height 24 of 200 nm, as depicted in FIG . 3 .

[0086] In this embodiment of the invention the MMI coupler 20 supports NxN=9 transverse modes and has a width 28 of 3075 nm and a height 29 of 200 nm and a length 26 of 1 . 76 pm, in the direction of light passage , respectively, and as depicted in FIG . 2 and 4 . The speci fic length of the MMI depends on the number of input channels and the actual shape of the photonic lantern 30 .

[0087] The interferometric module 6 comprises embedding bodies 16 ,

[0088] 21 . In one of them, the embedding body 16 , the input waveguides 10 are embedded. In the other one, the embedding body 21, the MMI coupler 20 is embedded. Embedding of the waveguide 10 cores can be accomplished by means of epitaxy or sputtering layer-deposition techniques.

[0089] The embedding bodies 16, 21 are made of SiO2. The cores of the input waveguides 10 are made of SiN, as well as the slab waveguide of the MMI coupler 20.

[0090] The channel waveguides as depicted in FIG. 3 are called "bur- ied-strip waveguides." Other types of channel waveguides are possible, such as "rib waveguides", and these do not change the function of the device but depend only on the manufacturing process and the process demands of any other devices which are being made on the chip.

[0091] In FIG. 5, the photonic lantern 30 is shown in more detail.

[0092] In this embodiment of the invention, the photonic lantern 30 is formed by NxN=9 slot waveguides 35. In the direction of light passage, these waveguides 35 have a width 34 of 341 nm and a height of 200 nm. At the matching interface with the MMI coupler 20 the waveguides 35 form a continuum.

[0093] X is the transverse coordinate of the device, which extends mainly in the direction Z.

[0094] Xn ( Z ) is the trajectory of the nthwaveguide . As there are 9 waveguides 35 in total, n has one of the values n = [-4,-3,- 2,-1, 0, +1, +2, +3, +4] .

[0095] Xn ( Z ) is given by the following formula:

[0096] In this preferred embodiment, the reference length 31 or Lohas been chosen to be 50 pm, such that the photonic lantern 30 fulfils an adiabatic transition condition. In this embodiment , Zohas been chosen to be 18 . 2 pm . Zocan be related to the length 31 of the photonic lantern 30 , which is Lo, the input period 32 , which is d0and the output period 33 , which is d according to :

[0097] In this embodiment , an input period 32 or d0of a waveguide 35 array of the photonic lantern 30 is 0 , 341 pm, and an output period 33 or d-^ of the waveguide 35 array of the photonic lantern 30 is 1 , 175 pm . With this separation, the waveguides can be considered as isolated .

[0098] The traj ectory can be extended to a distance Z > Lo, such that the period of the photonic lantern 30 is large enough to allow the insertion of output coupler 40 and light detectors 52 .

[0099] In this embodiment , the light is butt-coupled to an array of 50x50 pm InGaAs ( Indium gallium arsenide ) photodiode pixels with 100-micron period . The light out-coupler 40 is the output coupler which can be reali zed as a simple interface for butt coupling with the photodiode array 52 or an array of di f fraction grating directing the guided field onto a photodetector array placed above the top embedding of the PIC waveguides 35 .

[0100] The detection device 50 comprises a periodic array of 9 pixels of dimensions 50 x 50 pm with a center-to-center separation of 1 , 175 pm. These pixels measure the output power, producing a N' -dimensional light power vector which is multiplied by a suitable Moore-Penrose pseudo-inverse of the interferometer calibration matrix by the phase retrieval algorithm 60 in order to retrieve the relative phase and amplitude between the input fields . Other pseudo-inverse methods can be used to retrieve the phase information from the N' -dimensional output power vector . The multiplication of the detected power-vector by a pseudoinverse of the calibration matrix of the device returns the mutual coherence function of the input optical fields . The calibration matrix of the interferometric device or module relates the mutual coherence functions of the light at the input channels to the light power carried by the output waveguides . The description of the mutual coherence functions already includes the power of the light flowing in each of the input waveguides ( sel f-coherence function) . Therefore , by multiplying the vector of the measured output powers by pseudo-inverse of the calibration the complete information on the mutual coherence function of the input is obtained, inclusive the power carried by each input waveguide .

[0101] The retrieved phase shi ft does not dri ft over time because the variation of the input power in the light channels is accounted for in the phase retrieval algorithm .

[0102] As an example for the application of the interferometric module 6 , a miniaturi zed chemical laboratory 70 is shown in FIG . 6.

[0103] The miniaturi zed chemical lab 70 comprises a light source 72 which is built as a laser diode . The emitted laser light is fed into an 1x3 MMI coupler 80 from where it is fed into three feeding waveguides 84 . The lab 70 comprises windows 88 connected to a microfluidic circuit ( gas and / or liquid) . Inside these windows 88 , the feeding waveguides 84 are optically connected or built in a one-piece design with functionali zed spiral waveguides 92 which are in contact with at least one sample .

[0104] To the spiral waveguides 92 , three input waveguides 84 are optically connected or built in a one-piece design which are part of the interferometry system 2 . Spiral waveguides can be employed in the lab-on-chip which function as chemical sensors . Molecules can be attached through ligands to the waveguides and form bonds . The captured molecules lead to a change of the refractive index in the cladding of the waveguide and thus induce a variation of the propagation constant of light. This in turn leads to a phase-shift of the light which is detectable by the interferometric module. This is done without ambiguity.

[0105] By measuring phase differences, for example the concentration of the captured molecules can be determined. Viruses or tokens of DNA can be identified.

[0106] The interferometry system 2 can be integrated into a chip providing differential phase measurements of different functionalized waveguides.

[0107] The complete system can be used to characterize gases or liquids .

[0108] The complete sensor can have a footprint <0.5 cm2.

[0109] The miniaturized chemistry laboratory can be, for instance, employed in Point-of-Care biochemical diagnostics, Li-Ion battery monitoring for the car industry, and contaminant detection .

[0110] LIST OF REFERENCE NUMERALS Interferometry system Photonic integrated circuit ( PIC ) building clock Interferometric module Input waveguide Centre line of a waveguide Waveguide Centre line of a waveguide Fan-in section Centre line of a waveguide Embedding body Longitudinal center line of the slab waveguide Multi-mode interference (MMI ) coupler Embedding body Width of waveguide Height of waveguide Length of MMI coupler Width of MMI coupler Height of MMI coupler Fan-out section / photonic lantern Waveguides Output coupler Detection system Light detector Phase retrieval algorithm Miniaturi zed chemical laboratory Light source MMI coupler Waveguide Window Spiral waveguide

Claims

CLAIMS1. A multi-channel interferometric module (6) , comprising a plurality of input waveguides (10) in conjunction with a single multi-mode interference coupler (20) , wherein a fan-in section (14) and a fan-out section (30) are provided for input fields to enter and leave said multi-mode interference coupler (20) and wherein the plurality of input waveguides (10) is three or more waveguides.

2. Multi-channel interferometric module (6) according to claim 1, wherein the fan-out section (30) comprises a photonic lantern.

3. Multi-channel interferometric module (6) according to claim 2, wherein the photonic lantern comprises a number of waveguides (12) which is equal to or larger than the squared number of input waveguides (10) .

4. Multi-channel interferometric module (6) according to claim 2 or 3, wherein the waveguides (12) of said photonic lantern are arranged with increasing inter-waveguide separation.

5. Multi-channel interferometric module (6) according to claim 2, 3 or 4, wherein at the matching interface between the multi-mode interference coupler (20) and the photonic lantern, the waveguides (12) form a continuum.

6. Multi-channel interferometric module (6) according to claim 2, 3, 4 or 5, wherein an input period of awaveguide array of the photonic lantern is 0,341 pm and / or an output period of the waveguide array of the photonic lantern is 1,175 pm.

7. Multi-channel interferometric module (6) according to one of the preceding claims, wherein the cores of said input waveguides (10) are and / or the core of a slab waveguide of the multi-mode interference coupler (20) is, at least partially, embedded in an embedding body (21) .

8. Multi-channel interferometric module (6) according to claim 7, wherein said embedding body of the cores of the input waveguides is and / or said embedding body of the core of the slab waveguide of the multi-mode interference coupler is made of SiCy.

9. Multi-channel interferometric module (6) according to one of the preceding claims, wherein cores of said input waveguides are and / or the core of the slab waveguide of the multi-mode interference coupler (20) is made, at least partially, of SiN.

10. Multi-channel interferometric module (6) according to one of the preceding claims, wherein center lines of the input waveguides (10) are spaced equidistantly from each other and / or one center line of one waveguide coincides with a longitudinal center line of the slab waveguide of the multi-mode interference coupler (20) .

11. Multi-channel interferometric module (6) according to one of the preceding claims, wherein at least one inputwaveguide (10) has a width of 341 nm and / or a height of 200 nm .

12. Multi-channel interferometric module (6) according to one of the preceding claims, wherein the multi-mode interference coupler (20) has a length of 1,76 pm.

13. Multi-channel interferometric module (6) according to one of the preceding claims, comprising a light-out coupler .

14. Multi-channel interferometric module (6) according to one of the preceding claims, comprising a detection device consisting of an array of photo detectors.

15. Multi-channel interferometric module (6) according to claim 14, wherein for each waveguide a photo detector is provided .

16. Multi-channel interferometric module (6) according to one of the preceding claims, which is configured for an operational wavelength between 850 nm and 950 nm, especially 895 nm.

17. Multi-channel interferometric module (6) according to one of the previous claims, which is built as a photonic integrated chip (PIC) block (4) .

18. Interferometry system (2) comprising an interferometric module (6) according to claim 17 and comprising a phase retrieval algorithm (60) configured to determine a phase shift .

19. Miniaturized chemical lab (70) , comprising a multi-channel interferometric system (2) according to claim 18, further comprising a light source (72) .

Images