WO2015071317A1

WO2015071317A1 - Optical coupling device and method for operation thereof

Info

Publication number: WO2015071317A1
Application number: PCT/EP2014/074385
Authority: WO
Inventors: Marcel Kroh; Matthias Jäger; Danny Volkmann
Original assignee: Ihp Gmbh - Innovations For High Performance Microelectronics / Leibniz-Institut Für Innovative Mikroelektronik
Priority date: 2013-11-12
Filing date: 2014-11-12
Publication date: 2015-05-21
Also published as: DE102013223034A1; DE102013223034B4

Abstract

The invention relates to a method for operating a self-adjusting optical coupling device for automatically determining a distance value belonging to a set distance control variable between an optical source transmitting a light beam and an optical sink into which the light beam is to be coupled, comprising: providing reference beam width data which represent values of a beam width as a function of different distance values between a coupling-out plane of the source and a coupling-in plane of the sink; setting a plurality of lateral relative positions of source and sink in the case of one and the same distance control variable determining the coupling-in plane, and in each case detecting an intensity signal which is a measure of the light intensity coupled out by a coupling-out surface in the source in the coupling-out plane and coupled into the coupling-in surface of the sink; calculating a value of a variable representing the beam width of the light beam coupled out by the source in the coupling-in plane on the basis of the detected light intensities in plurality of lateral relative positions; and determining the perpendicular distance value which is assigned to the set distance control variable on the basis of the detected value of the beam width and on the basis of the reference beam width data.

Description

Optical coupling device and method of operation therefor

The invention relates to an optical coupling device for coupling a light beam, which can be coupled out of a decoupling plane defining an outcoupling surface of an optical source, in an optical sink, which has a coupling surface, which defines a Einkoppelebene. The invention further relates to an operating method of an optical coupling device.

Increasing integration of optical components, especially in the field of nanophotonics, has made the need for automated couplings such as waveguides and fibers, as well as fibers and fibers or waveguides and waveguides increasingly important.

One of the major difficulties in coupling waveguides and fibers was the difference in size between fiber and waveguide. However, this problem has been largely eliminated by the availability of grating couplers. Known methods, after coarse adjustment, which must bring the fiber close enough to the grating coupler to detect transmission of coupled light, allow only the automatic finding of a lateral position of optimal transmission in an xy plane (also referred to herein as lateral or tangential) is parallel to an input or Auskoppelebene defined by a surface of the grating coupler. An automatic adjustment of the (vertical) distance between source and sink is much more difficult, because there is often no or no clear maximum here. However, in order to allow reproducible measurements, for example in an on-wafer test method, it is important to always set the same distance between source and sink. This is done in the example of the coupling of fiber and waveguide on a chip currently usually manually by one of the following two methods:

1. The fiber is carefully guided with a micrometer screw in the direction of the chip until it touches it and then removed from this position by the desired distance. 2. The fiber is brought near the chip. Then the tip of the fiber as well as its shadow or mirror image is viewed by means of a microscope. The fiber is then adjusted so that only a narrow edge next to the fiber tip remains visible from the shadow or mirror image. If you repeatedly create the same edge, you are always at the same distance. Both methods have the disadvantage that they require an experienced operator and an accuracy of less than 10 μιτι can not achieve. The former method has the additional disadvantage that the risk of damage to the chip and fiber, while the second-mentioned method requires a high expenditure on equipment in the form of a good microscope optics. Errors in the adjustment of the microscope optics also lead directly to errors in the distance adjustment achieved.

The present invention is based on the recognition that for an on-wafer test in the field of integrated optics, as is usual for comparison in the field of electronics, a fully automated adjustment of the coupling of source and drain is required. The invention further recognizes that, as an essential prerequisite for an automatic distance adjustment between source and sink required in this context, firstly a precise automatic determination of the current distance is required, in order then to be able to automatically set a predetermined distance value in a further step.

In a first aspect, the invention initially provides an operating method of an optical coupling device for automatically determining a distance value belonging to a set value of a distance manipulated variable, for example an actuator position, such as a distance servomotor position a light beam emitting optical source and an optical well into which the light beam is to be coupled, comprising:

Providing reference beamwidth data representing values of a beamwidth as a function of different distance values between a source coupling-out plane and a sinking plane of the sink;

- Setting a plurality of lateral relative positions of the source and sink at one and the same Einkoppelebene determining value of the distance control variable, and each detecting an intensity signal, which is a measure of a decoupled from the output surface of the source coupled in the decoupling plane and in the coupling surface of the sink coupled light intensity is;

Calculating a value of a quantity representing the beam width of the light beam coupled out from the source in the coupling-in plane on the basis of the detected light intensities in the multiplicity of lateral relative positions; and

Determining the distance value which is assigned to the set value of the distance control variable, based on the determined value of the beam width and on the basis of

Reference beam width data.

The operating method of the first aspect of the invention enables a three-axis automatically positionable holding device of a coupling device for coupling a light beam to determine the actual value of the vertical distance in metric units given at a current distance servomotor position. For this purpose, it relies on an automatic measurement of the beam width in the coupling plane of the sink. As Einkoppelebene that plane is called, which contains the planar coupling surface of the sink. The coupling-in plane is in some embodiments parallel or approximately parallel to the coupling-out plane of the source, which is defined by a plane coupling-out surface. In contrast, in other embodiments, it is not parallel to the output node of the source. The use of the coupling-out plane and the coupling-in plane as a measure of the distance between source and sink is not meant to limit the invention to these levels for determining the distance. Other distance measures, which allow a conclusion on the distance between source and sink, can be used.

The method first takes a variety of measurements of the coupled Light intensity at different positions of the coupling plane before. For this purpose, an automatic positioning is performed with at least one of the two lateral servo motors. The collected intensity data is used to determine how far the beam has been expanding since it left the source. Since this quantity is directly related to the distance between the light source and the sink, the distance value can be determined from the determined beam width. For this purpose, use is made of reference beam width data which are already known at the time of determining the distance value.

This principle can also be applied accordingly by swapping source and sink.

Hereinafter, embodiments and developments of the method will be described.

The meaning of the geometrical term "distance" differs in different embodiments of apparatuses and methods according to the invention, and it is possible to convert between the perpendicular distance known from the intuition and other distance definitions by calculation methods known per se.

In one embodiment, the distance is to be understood as meaning the distance along an imaginary extension of a fiber axis to a chip surface. This appears the most physically meaningful definition for the typical application. Alternative embodiments define the distance from a center of a fiber end surface to the chip surface in a direction perpendicular to the chip surface. The variants differ only if the coupling-in plane is not parallel to the coupling-out plane. The difference leads to changed model parameters, which are used in further developments of the method.

For measurement, in preferred embodiments, the light source is supplied by a laser source, for example a tunable laser source (TLS). At the light sink, a photodetector is preferably used to convert the optical signal into an electrical signal. This may be, for example, a photodiode, which is integrated in a power meter. In this case, the power meter can directly output the received light output as a digital signal, for example via a GPIB bus. The described exact calibration and conversion into absolute performances however, is irrelevant to the method, since only relative history is important.

In preferred applications of the method, either source or drain is identical to an optical fiber. The respective other side is in such exemplary embodiments particularly preferably a grating coupler, which is connected via a waveguide on the chip to a further grating coupler and via a fiber to the corresponding device. However, there are also other applications in which a photodiode as a sink or a laser source is integrated on a chip and is contacted only electrically. There is also the possibility that the source itself is a laser or an LED, or that the sink itself is a photodetector.

Preferably, the laser used always delivers the same power during the measurement. If this is not the case, the system is extended by a measurement of the power change, and the ratio of output to input power is evaluated as a measurement signal. As servomotors preferably highly accurate motors, such as stepper motors or piezo actuators are used.

The additional determination of the reference beam width data is the subject of embodiments of the present invention, which are described in more detail below. Such an embodiment additionally includes, prior to determining the offset value, a process for capturing the reference beamwidth data in an automatic calibration procedure prior to determining the distance. The calibration procedure contains the following steps:

Adjusting different pitch servomotor positions between the launch plane and the drop plane and detecting the light intensity coupled out from the source and coupled into the dip in a plurality of different lateral relative positions of source and sink at each set actuator position, and determining a respective value of the beam width at the respective distance actuator position representative size;

Determining a widening function describing the beam width as a function of the servo motor distance position between the coupling plane and the decoupling plane on the basis of the differences determined in the case of the various servo motor distance positions Beamwidths using a given mathematical beam model; and

Determining and assigning distance values to the distance actuator positions based on the determined expansion function and the determined actuator distance zero point. In one embodiment, a control motor zero distance corresponding to a vanishing vertical distance value is determined based on the determined expansion function and the beam model.

In alternative embodiments, the quantity representing the beamwidth of the light beam coupled out from the source in the launching plane is either the half-value width (in one dimension) or half-value area (in two dimensions) of the light beam or the 1 / e-width or area of the light intensity in at least one direction in the Einkoppelebene, and wherein the adjustment of the plurality of lateral relative positions for detecting light intensities at the same distance actuator position in a lateral direction at least until falling below the half values and the 1 / e-values of the light intensity on both sides an intensity main maximum is performed. Measuring in just one dimension simplifies the process. On the other hand, measurement in two dimensions allows for greater accuracy.

The beam model for the light coupled out of the decoupling plane corresponds in preferred applications to a Gaussian beam profile. But also deviating profiles can be used in connection with the method according to the invention. A deviation from the Gaussian profile can, for example, be taken into account with a beam quality parameter designated M ² . The beam quality parameter M ² describes the deviation from the Gaussian beam in a simple model. The Gaussian beam is the physical limit of focusability that minimizes the product of aperture angle and beam waist. The beam quality parameter M ² is equal to one for the Gauss beam. For deviant rays, it becomes greater than one. The product of opening angle and beam waist is in this case larger by a factor of M ² . An extended by M ² formula of the Gaussian beam is sufficient to even for strongly deviating from the Gaussian beam - even those with multiple maxima - to define a beam width as a function of the height. Since the beam width is defined here not by the drop to a certain value but by percentiles, a measurement is necessary to further distances. at Multimode beam distributions or beam distributions with multiple maxima require a very large lateral area to be scanned. The feasibility of such additional measurements limits the applicability of a model based on a Gaussian profile. Therefore, in this case, another preferred embodiment of the method is used. The following are some possible cases: a) Consider first the case of coupling where only the source or sink has a beam distribution with (at least at some distances) several maxima. Here it is most practical to use not only the beam width but the entire beam distribution as a function of the height as reference data. By comparing the measured data with the reference data of different heights (eg by means of cross-correlation), the distance is then determined. b) It is also possible that, in particular for small distances, several separate maxima occur (near field), but these overlap at greater distances (far field) to a maximum. In this case, all you have to do is treat the near area with more accurate data. c) Another case of application related to this in its solution is a coupling in which only the source or only the well has an intensity distribution which is composed of several modes. Using incoherent light results in a temporally stable intensity average due to the incoherence. It can be proceeded according to the previous case. d) Another situation arises when using coherent light. Consider, as in the previous case, that only the source or just the sink has an intensity distribution made up of several modes. When using coherent light, the relative phases of the modes may fluctuate, resulting in a time-varying image. Here arise so-called speckels. However, this case can be attributed to the previous case by temporal averaging, optionally associated with artificial rapid variation of the phases (achievable in multimode fibers, for example using ultrasound). e) If there is no temporal variation of the relative phases, the method can be used as in the source / sink with multiple maxima in the field distribution. f) If both source and sink are multi-mode or have multiple maxima, statistical methods can be used. Alternatively, it would be possible to measure several modes separately and to evaluate them via coupling matrices. However, a separate measurement of the modes means a relatively high technical effort.

A second aspect of the present invention is a control method of a self-aligning optical coupling device adjustable with three-dimensional servomotors for automatically setting a predetermined vertical distance between an optical source and an optical sink, comprising: driving at least one of the servomotors to set a predetermined starting distance; Servomotor position, which allows the coupling of a detectable light intensity of the coupled out of the source light beam in a coupling surface of the sink without risk of direct mechanical contact between the source and sink; Performing a method according to the first aspect of the invention or one of its embodiments for determining a distance value associated with the start actuator position;

- Determining a the predetermined distance associated distance control value, in particular distance actuator position, based on the reference beam width data; and

- Controlling at least one of the servomotors for setting the determined distance control variable, in particular distance actuator position.

With the method, a fully automated distance adjustment between an optical source and an optical sink can be made. In the application of the coupling of grating coupler to standard single-mode fiber accuracy of the distance setting of 0.5 μιτι in a range of 30 μιτι to 110 μιτι distance between the optical fiber and the grating coupler has already been achieved on prototypes of a self-adjusting optical coupling device described in more detail below. A coupling between the grating coupler and the fiber with a height error of 0.5 μιτι leads at a distance of 100 μιτι to a deviation of the transmitted power of a maximum of 0.03 dB, which corresponds to a change of 0.6% of the power. Should only always be set the same distance, the accuracy is even higher, so with deviations of less than 0.5 μιτι.

A third aspect of the invention is an optical coupling device for coupling a light beam, which can be coupled out of a decoupling surface defining an outcoupling surface of an optical source, in an optical well having a coupling surface, which defines a Einkoppelebene comprising

a holding device with controllable servomotors, which is designed to set relative positions of the source and the sink to one another in three dimensions,

a sensor unit which is arranged and designed to generate and output an intensity signal which is a measure of a light intensity coupled out from the source and coupled into the coupling surface of the sink;

- A control device which is designed to control the determination of a vertical distance value between the Auskoppelebene and determined by the set Stellmotor- distance position Einkoppelebene the holding device to set a plurality of different lateral Stellmotorpositionen the coupling surface in the Einkoppelebene and to control the sensor unit, in the set lateral Servomotor positions each to capture the coupled from the source and coupled into the sink light intensity,

an evaluation unit which is designed to calculate a value of a quantity representing a beam width of the beam coupled out from the source in the coupling-in plane for each set actuator distance position on the basis of the light intensities detected in the different lateral actuator positions and on the basis of predetermined reference beam width data Specify values of the beam width as a function of distance values between the coupling-out plane and the coupling-in plane to determine the given vertical distance value.

In the coupling device of the third aspect of the invention, the special design of the control device makes it possible to control the holding device that can be positioned automatically in three axes in such a way that with the aid of the evaluation unit an actual value of the vertical distance in metric units given at a current distance servomotor position is determined can. For this purpose, the device allows an automatic measurement of the beam width in the coupling plane of the sink. To this Way, the foundation is created for a precise self-positioning in three dimensions.

In a preferred embodiment of the coupling device, the control device is additionally designed to control the holding device, the sensor unit and the evaluation unit for carrying out an automatic calibration procedure

Determining an expansion function describing the beam width as a function of the servo-motor distance position between the coupling-in plane and the coupling-out plane on the basis of the beam widths determined at the various servo-motor distance positions on the basis of a predetermined mathematical beam model; and

Determining and assigning distance values to the distance actuator positions based on the determined expansion function and the determined actuator distance zero point.

In a preferred embodiment of the coupling device, the control device is designed for the self-adjusting setting of a predetermined vertical distance value between the optical source and the optical sink

- to control at least one of the servomotors to set a predetermined start-Stellmotorposition that allows the coupling of a detectable light intensity of the coupled out of the source light beam in a coupling surface of the sink without risk of direct mechanical contact between the source and sink;

to determine a distance value assigned to the starting servomotor position;

to determine a distance actuator position assigned to the predetermined distance value on the basis of the reference beam width data; and - To control at least one of the servomotors for setting the determined distance actuator position.

With this development, an automatic high-precision reproducible distance adjustment between source and sink, as can be advantageously used in on-wafer measuring methods for integrated electro-optical components, succeeds.

Preferably, the control device is additionally designed to control at least one of the servomotors to set a predetermined lateral relative position. For this purpose, known methods can be used with which a lateral position of maximum coupling efficiency is determined and set.

A preferred application of the coupling device is an optoelectronic device with a light source, a coupler device according to the third aspect of the invention or one of its described embodiments, a supply line for emitted from the light source electromagnetic waves to the coupler device, and a derivative of electromagnetic waves output from the coupler device.

Another application of the invention is an optical arrangement with an integrated-optical coupler device according to the invention or one of its described embodiments or an optoelectronic device described in the last paragraph, and with the coupling grid for coupling or decoupling the electromagnetic waves suitably facing optical multimode fiber.

Hereinafter, further embodiments will be explained with reference to the figures. Show it:

FIG. 1 shows a measured intensity distribution of coupled-in light as a function of the lateral position in the xy plane using the example of an approximately Gaussian beam at a distance of approximately 20 μιτι between a grating coupler as a source and a single-mode fiber as a sink;

FIG. 2 shows a measured intensity distribution of coupled-in light as a function of the lateral position in the xy plane using the example of an approximately Gaussian beam at a distance of approximately 100 μm between a grating coupler as source and a single-mode fiber as sink; 3a, b schematic representations of embodiments of an optical coupling device;

4 is a block diagram of an embodiment of an optical coupling device;

Figures 5a-c are diagrams showing examples of reference beam width data;

6 shows an exemplary embodiment of an operating method of an optical coupling device for determining a current distance value between a source and a sink;

7 shows an exemplary embodiment of an operating method of an optical coupling device for determining reference beam width data; and

8 shows an embodiment of an operating method of a self-aligning optical coupling device.

1 shows a measured intensity distribution of coupled-in light as a function of the lateral position in the xy plane using the example of an approximately Gaussian beam at a distance of approximately 20 μιτι between a grating coupler as a source and a single-mode fiber as a sink. For comparison, Fig. 2 shows a corresponding representation of the Gaussian beam of Fig. 1 at a distance of about 100 μιτι between the grating coupler and the single-mode fiber. The comparison of the two measured intensity distributions clearly shows a widening of an initially narrow, over a range of about 10 μιτι extending maximum of the intensity distribution at a small distance to a broad maximum, the entire detected scale range of 20 μιτι in the x and y direction covered.

The lawful expansion of the beam with increasing distance between the grating coupler (as an example of a source) and the single-mode fiber (as an example of a sink) forms the basis for embodiments of methods and apparatus described with reference to the following figures.

Figures 3a and 3b are schematic illustrations for explaining terms used in the further description of embodiments of the optical coupling device. The illustration in FIGS. 3a and 3b is greatly simplified and focuses on schematic representations of essential geometric relationships. 3a shows a coupling device for coupling in a light beam, which can be coupled out of a decoupling surface of a grating coupler 14 defining a decoupling plane 16. The grating coupler thus forms an example of an optical source. As an optical sink, a fiber 10 is exemplified, which is shown here in a longitudinal section. The fiber 10 has at its lower end a coupling surface 11 which defines a Einkoppelebene 12. In the present example, the decoupling plane 16 and the Einkoppelebene 12 are parallel to each other and have a distance h to each other, which corresponds to the vertical distance between the Einkoppelebene 12 of the Auskoppelebene 16.

3b shows a slightly modified embodiment of a coupling device, which differs from the coupling device shown in FIG. 3b in that the coupling-in plane 12 is inclined relative to the coupling-out plane 16 due to an inclination of the fiber 10. The distance between the decoupling surface 16 and the coupling surface 11 is measured in the present example along an imaginary extension of a fiber axis A between the coupling plane 11 and the decoupling plane 16, ie the chip surface 15 and marked with h '.

The meaning of the geometrical term "distance" may thus be different in different embodiments of devices and methods according to the invention, but such variants of the geometric meaning of the terms as illustrated in Figures 3a and 3b are technically equivalent and require 3b, the situation shown in Fig. 3b is more frequently used in practice, but the following presentation concentrates on the case of Fig. 3a, which is less common in practice, because in this way the explanation of expensive, but conversions between different coordinate systems which are completely familiar to the person skilled in the art and the corresponding actuation of the actuators to be changed during the adjustment can be dispensed with.

From the grating coupler 14, a light beam S is coupled out during operation of the illustrated device and must be coupled into the fiber 10. For this purpose, either the fiber, or the chip 15, on which the grating coupler 14 is arranged, or to adjust both the fiber and the chip in the three spatial directions x, y and z, to a desired optimal coupling of the beam in the fiber achieve. The lateral adjustment as such is known to the person skilled in the art and will not be discussed further here become. On the other hand, the adjustment of the distance is based on the devices and process guides shown below with reference to further exemplary embodiments in FIGS. 4 to 8.

4 shows, on the basis of a block diagram of an embodiment of an optical coupling device, functional units which are used in exemplary embodiments of the coupling device according to the invention. On the concrete representation of mechanical components can be omitted, since it depends on the functional control of the adjustable components in the context of automated process management. In addition to the already known from Fig. 3a and 3b light source, which may be either the fiber 10 or the grating coupler 14 depending on the desired application (therefore the reference numerals 10/14 and 14/10 for source and sink in Fig. 4), are the following further parts of the optical coupling device shown: a holding device 18 with three actuators in the form of controllable servo motors 18.1, 18.2 and 18.3, which can change the fiber position in the present example to set relative positions of the fiber 10 and the grating coupler 14. In a variant shown by dotted lines instead of the position of the source, the position of the light sink, which may also be grating coupler 14 or fiber 10 may be adjusted. The grating coupler 14 is always adjusted together with the chip 15 carrying it. In another variant (not shown), stepping motors are provided for both optical elements, ie fiber 10 and grating coupler 14. Furthermore, a Justierlaser 20 and a photodetector 22, for example in the form of an optical power meter (power meter) or in the form of a photodiode available. The path of the light in the adjustment of the device in the present example is indicated by a dashed line. Furthermore, a control unit 24 is provided, either in the form of an integrated circuit (e.g., ASIC) or in the form of a software engine appropriately configured computer. The control unit 24 is connected to a reference data memory 26 on the one hand and to an evaluation unit 28 on the other hand.

In operation of the optical coupling device of Fig. 4, the holding device 18 in accordance with the control unit 24 by means of the three servomotors 18.1 to 18.3 in three dimensions by the control unit predetermined relative position of the source and the sink to each other. The likewise controlled by the control unit 24 Justierlaser 20 generates to measure the coupling efficiency of a light beam, the is passed through the light source and the light sink in their current relative position to each other. Depending on the adjustment of the holding device, more or less light from the light source is coupled into the light sink. The coupled amount of light is detected by means of the sensor unit 22 in the form of the photodiode. The electrical intensity signal generated by it is forwarded on the one hand to the control device 24 and on the other hand to the evaluation unit 28.

The control device is designed, in particular, to control the coupling device for calibration and after calibration for determining a distance value h or h 'between the coupling-out plane, that is, for example, the plane 16 and the coupling-in plane, ie, plane 12, for example, as described below with reference to the methods described there is explained in more detail.

The measurements to be made are based on the determination of the beam width in at a given distance. To determine the beam width, the control unit 24 controls the holding device 18 to set a multiplicity of different servomotor positions for a given distance. In order to be able to hold the plane at different lateral positions, it is therefore important to know the angle between the coupling plane and the coupling-out plane. This must be entered in advance or otherwise determined. The measurements for determining the beam width can be carried out as a one-dimensional scan or as a two-dimensional scan. A two-dimensional scan is more accurate. The accuracy of the measurement of the beam width can be further determined by the number of measuring points at a given distance.

The sensor unit 22 measures in each set actuator positions at a given distance in each case the decoupled from the grating coupler 14 and coupled into the fiber 10 light intensity. The evaluation unit calculates a value for the set distance on the basis of the light intensities detected in the different lateral actuator positions at this distance, which value represents a beam width which the beam coupled out by the grating coupler 14 has in the coupling-in plane 11. Using reference beam width data stored in the reference data memory 26 and indicating the values of the beam width as a function of distance values between the coupling-out plane and the coupling-in plane, the given distance value is determined by the evaluation unit 28.

5 a is an example diagram which shows measured values of a beam width determined by the method according to the invention as a function of the distance between coupling grating and Represents fiber. The beam width is reproduced here as a spot radius w, which corresponds to half the beam width 2w. Measuring points are reproduced in the form of crosses. The beam profile of a Gaussian beam calculated using a mathematical formula is shown as a solid line. The representation shows the reliability of the distance determination based on the beam width. Once the beamwidth as a function of the distance between the grating coupler and the fiber has been determined metrologically at several distance points, the exact distance value can be determined by means of extrapolation and interpolation. The extrapolation helps to determine the non-metrologically detectable spot radius w ₀ with vanishing distance between the grating coupler 14 and the fiber 10. With the help of interpolation, it is possible to determine a precise value of the distance between grating coupler and fiber for each value of the beamwidth experimentally determined in the further course.

The beam width in the form of the spot radius is calculated using the following formula for Gaussian beams:

where w indicates the beam radius, w ₀ indicates the beam radius with zero distance h = 0 (beam waist), (hh _0ff ) the distance between source and sink, λ the wavelength and n the refractive index. The correction factor h _0ff compensates for an offset between the positions of the actuators h and the actual distance between source and sink. With _off- focus and defocusing elements, h _off can compensate for the resulting offset as a source or sink. In this case, however, (hh _0ff ) is no longer identical to the physical distance between source and sink.

In many applications, the light beam emitted by a source is not an ideal Gaussian beam. In order to be able to carry out the method according to the invention for these applications as well, the following dependencies are used: The beam width in the form of the beam radius as a function of the distance between source and sink results from the formula for the beam expansion of Gauss beams, taking into account the beam quality parameter

in addition to the already explained symbols in this formula, the beam quality parameter M ² is used, which is based on the formula

is determinable. Furthermore, the distance can be represented as a function of the beam width as

5b shows the dependence of the beam width as a function of the distance from the beam waist, ie the narrowest beam cross section as a function of different parameter values of the beam quality. The maximum beam quality of an ideal Gaussian beam is assigned to the value M ² = 1. Here, the smallest beam expansion takes place with increasing distance from the beam waist. A stronger beam expansion can be seen on the basis of the further curves in FIG. 5b, which in the diagram, seen from the bottom up, correspond to the beam quality parameters M ² = 1, 2; 1, 5; and 2 correspond. 5c shows in a further diagram the dependence of the beam width as a function of the distance h from the beam waist w ₀ for different values of the lateral extent beam waist, ie the value of the beam width at vanishing distance from the beam waist. All curves shown in Fig. 5c were calculated for an identical value of the beam quality parameter M ² = 1. The curve shows that as the beam waist decreases, the expansion of the beam to higher distance values becomes ever greater.

6 is a flowchart of one embodiment of an operating method of an optical coupling device as in FIG. 4, for determining a current distance value between a source and a sink. It should be noted that the flowcharts of FIGS. 6 to 8 show the z position as an example of the distance value assume, that is adjustable with only a single actuator value. Depending on the configuration of the coupling device (see Figures 3a and 3b), however, the distance value (h or h ') can be set in other variants by adjusting at least two, typically all three servomotors. The restriction to the example of an adjustment using only the z-position is therefore not to be understood as limiting, but merely in the context of a simple example, with the help of which the function and the steps to be performed can be explained particularly easily.

In order to determine a distance value after a z-position has been motorized in a step S10, a first value of a lateral, ie xy, position is first set (step S12) and with the alignment laser switched on or with the light source of the device to be adjusted switched on at the set xy position the injected intensity is measured (S14). Subsequently, it is checked if a new x-y position is to be set (S16). If so, the process returns to step S12 and repeats steps S12 through S16 until the test at step S16 reveals that the control unit is not setting a new XY position. In this way, therefore, a scan of the intensity distribution in the x-y plane to the set distance (here z) is performed. On the basis of the thus determined position-dependent intensity data at the given distance position, a value of the beam width for the given distance value is then determined. The determined beam width subsequently makes it possible to determine the beam width by means of previously stored reference beam width data, as shown in FIGS. 5a to 5c (step S20).

7 shows an exemplary embodiment of an operating method of an optical coupling device according to the invention for determining reference beam width data, which can also be referred to as calibration beam width data. This method may be performed prior to the method of FIG. 6 to provide the reference beamwidth data. This method can also be carried out fully automatically, which is a great advantage in particular in the industrial production of optoelectronic components or in applications in which frequently changing chips have to be coupled (eg, biosensors). In this method, a predetermined number of xy positions are set for various distance values each set in a step S30 (S32), and the intensity is measured at these xy positions (S34). From the measurement at a given distance position, the respective beam width is determined in each case (S38). This step can also be done later in the process be performed. The same measuring method is carried out by control with the aid of step S40 for all z positions predefined by the control unit, ie distance values.

In the method of FIG. 7, after taking the measured values and determining the beam width, a widening function is determined as a function of the actuating motor distance position (S42). This corresponds, for example, to the curve drawn in a solid line in the diagram in FIG. 5a. In the next step, the zero position of the distance adjusting motor can be determined either by comparing the measured data with the determined expansion function (S42), or alternatively by means of an additional measuring method. As a further alternative possibility, the distance zero point of the servomotor can be determined by means of an input, ie by definition. The reference beam width data thus determined are then stored in the form of model parameters and / or beam width data as a function of the distance (S46), in order then to be used for later distance determinations according to FIG.

Fig. 8 shows an example of an operation method of a self-aligning optical coupling device for setting a distance command value. The procedure assumes that the device has previously been calibrated according to the method of FIG. 7, for example. In a step S50, first, a distance command value is received as a control input. Subsequently, a pre-configurable coarse distance position is set (S52), which ensures that neither the source nor the sink will be damaged by setting this coarse distance value. The distance value thus set is then determined by executing a method of FIG. 6 (S54). Based on the determined distance value then the servomotor position is determined, which corresponds to the predetermined distance setpoint (S56). The pitch drive motor (s) are then driven to adjust the detected actuator position (S58) to establish the distance setpoint. Finally, a lateral adjustment (S60) takes place at the predetermined distance setpoint in order to optimize the coupling.

Claims

claims

A method of operating a self-aligning optical coupling device for automatically determining a distance value associated with a set distance manipulated variable between an optical source emitting a light beam and an optical sink into which the light beam is to be coupled, comprising:

- Setting a plurality of lateral relative positions of the source and sink at one and the same, the coupling plane determining distance control variable, and each detecting an intensity signal, which is a measure of a coupled from a coupling surface of the source in the Auskoppelebene and coupled into the coupling surface of the sink light intensity is;

- Determining the vertical distance value, which is assigned to the set distance control variable, based on the determined value of the beam width and based on the reference beam width data.

2. Operating method according to claim 1, wherein the distance control variable is an actuator position, in particular a servomotor position of one or more servo motors.

3. Operating method according to claim 1 or 2, additionally comprising before the determination of the distance value:

Including the reference beam width data in an automatic calibration procedure before determining the distance, comprising

- Setting different distance actuator positions between the coupling plane and the Auskoppelebene and detecting the source decoupled and coupled into the sink light intensity in a plurality of different lateral relative positions of source and sink at each set distance actuator position, and determining a respective value of the beam width at the respective distance actuator position representative size;

Determining an expansion function describing the beam width as a function of the positioning motor distance position between the coupling-in plane and the coupling-out plane on the basis of the beam widths determined at the various positioning motor pitch positions on the basis of a predetermined mathematical beam model; and

4. The method according to at least one of the preceding claims, wherein as the size which the beam width of the light beam coupled out from the source in the

Einkoppelebene represents, either the half-value of the light beam or the 1 / e-width of the light intensity is determined in at least one direction in the Einkoppelebene, and wherein the setting of the plurality of lateral relative positions for detecting light intensities at one and the same distance actuator position in a lateral direction at least until it falls below the half values or the 1 / e values of the light intensity on both sides of a main intensity maximum is performed.

5. The method according to at least one of the preceding claims, wherein the beam model for the decoupled from the decoupling light corresponds to a Gaussian beam profile.

6. Control method of an adjustable with servomotors in three dimensions, self-adjusting optical coupling device for automatically setting a predetermined distance between an optical source and an optical sink, comprising: - driving at least one of the servomotors for setting a predetermined start actuator position, the coupling of a detectable Light intensity of the coupled out of the source light beam into a coupling surface of the sink without risk of direct mechanical contact between the source and sink allows;

Carrying out a method according to at least one of claims 1 to 5 for determining a distance value assigned to the starting servomotor position;

- Determining a the predetermined distance associated distance actuator position based on the reference beam width data; and

- Controlling at least one of the servomotors for setting the determined distance actuator position.

A method according to any one of the preceding claims, wherein a nano-photonic grating coupler forms either the source or the well.

A method according to any one of the preceding claims, wherein an optical fiber forms either the well or the source.

9. Optical coupling device for coupling a light beam, which can be coupled out of a decoupling plane defining a decoupling surface of an optical source, in an optical sink having a coupling surface, which defines a Einkoppelebene comprising

a holding device with controllable servomotors, which is designed to set relative positions of the source and the sink to one another in three dimensions; a sensor unit, which is arranged and configured to generate and output an intensity signal which is a measure of one coupled out of the source and is in the coupling surface of the sink coupled light intensity;

- A control device which is adapted to control the determination of a distance value between the Auskoppelebene and determined by the adjusted servo motor distance position Einkoppelebene the holding device to set a plurality of different lateral Stellmotorpositionen the coupling surface in the Einkoppelebene and to control the sensor unit, in the set lateral Stellmotorpositionen each of the decoupled from the source and in the Sink to capture coupled light intensity,

an evaluation unit which is designed to calculate a value of a quantity representing a beam width of the beam coupled out from the source in the coupling-in plane for each set actuator distance position on the basis of the light intensities detected in the different lateral actuator positions and on the basis of predetermined reference beam width data Specify values of the beam width as a function of distance values between the coupling-out plane and the coupling-in plane to determine the given distance value.

10. Coupling device according to claim 9, wherein the control device is additionally formed, the holding device, the sensor unit and the evaluation unit for

Performing an automatic calibration procedure, comprising

Adjusting different pitch servomotor positions between the optical source and the optical well, and detecting the light intensity coupled out from the source and coupled into the well in a plurality of different lateral relative positions of source and sink at each adjusted distance servomotor position, and determining a respective value of the the beam width at the respective distance actuator position representative size;

- Determining a the beam width as a function of the Stellmotor- distance position between coupling plane and Auskoppelebene descriptive

Expander function based on the beam widths determined at the different actuator distance positions using a given mathematical beam model;

11. Coupling device according to claim 9 or 10, wherein the control device is designed for automatically setting a predetermined distance value between the optical source and the optical sink

- to control at least one of the servomotors, a predetermined start Adjusting actuator position, which allows the coupling of a detectable light intensity of the coupled out of the source light beam in a coupling surface of the sink without risk of direct mechanical contact between the source and sink; to determine a distance value assigned to the starting servomotor position;

to determine a distance actuator position assigned to the predetermined distance value on the basis of the reference beam width data; and

- To control at least one of the servomotors for setting the determined distance actuator position.

12. Coupling device according to claim 11, wherein the control device is additionally designed to control at least one of the servomotors to set a predetermined lateral relative position.