WO2024184074A1

WO2024184074A1 - Method of manufacturing a photonic circuit and alignment device

Info

Publication number: WO2024184074A1
Application number: PCT/EP2024/054427
Authority: WO
Inventors: Christian SCHOERNER; Anna Butsch
Original assignee: Ams-Osram International Gmbh
Priority date: 2023-03-06
Filing date: 2024-02-21
Publication date: 2024-09-12

Abstract

A method of manufacturing a photonic circuit (10) comprises aligning a laser device (110) and an optical waveguide element (105). The laser device (110) and the optical waveguide element (105) are arranged in a spatial relationship, so that the laser device (110) is configured to emit a laser beam (15) to be incident on an input facet (107) of the optical waveguide element (105), a first horizontal direction corresponding to a direction between an output facet (114) of the laser device (110) and the input facet (107) of the optical waveguide element (105). Aligning comprises changing a relative position of the laser device (110) and the optical waveguide element (105) in the first horizontal direction while causing the laser device to emit the laser beam (15) and detecting a self-mixing interference signal and determining an extremum of the self-mixing interference signal while changing the relative position of the laser device (110) and the optical waveguide element (105) in a first plane perpendicular to the first horizontal direction. The method further comprises defining a target position in the first plane as a position at which the extremum of the self-mixing interference signal is determined.

Description

METHOD OF MANUFACTURING A PHOTONIC CIRCUIT AND ALIGNMENT DEVICE

Photonic circuits comprising e . g . a laser device and an optical waveguide element are increasingly being employed in a variety of applications . Generally, concepts are being sought by which a laser and the optical waveguide element may be aligned in an easy and reliable manner .

It is an obj ect of the present invention to provide an improved method of manufacturing a photonic circuit . It is a further obj ect to provide an improved alignment device .

According to embodiments , the above obj ects are achieved by the claimed matter according to the independent claims .

SUMMARY

According to embodiments , a method of manufacturing a photonic circuit comprises aligning a laser device and an optical waveguide element , the laser device and the optical waveguide element being arranged in a spatial relationship, so that the laser device is configured to emit a laser beam to be incident on an input facet of the optical waveguide element , a first hori zontal direction corresponding to a direction between an output facet of the laser device and the input facet of the optical waveguide element . Aligning comprises changing a relative position of the laser device and the optical waveguide element in the first hori zontal direction while causing the laser device to emit the laser beam and detecting a sel f-mixing interference signal . The method further comprises determining an extremum of the sel f-mixing interference signal while changing the relative position of the laser device and the optical waveguide element in a first plane perpendicular to the first hori zontal direction . The method further comprises defining a target position in the first plane as a position at which the extremum of the sel fmixing interference signal is determined . According to embodiments and depending on the configuration of the optical waveguide element , the extremum may be a maximum . According to further embodiments , the extremum may be a minimum .

For example , the relative movement may be performed, so that a distance between the laser device and the optical waveguide element decreases and increases . For example , this movement may by continuously performed . By way of example , an oscillating movement may be performed . For example , this movement may be periodic .

For example , changing the relative position may comprise moving the laser device and leaving a position of the optical waveguide fixed . According to further embodiments , changing the relative position may comprise moving the optical waveguide and leaving a position of the laser device fixed .

For example , detecting a sel f-mixing interference signal may comprise reading out a j unction voltage of the laser device .

The method may further comprise determining a target relative position of the laser device and the optical waveguide element in the first hori zontal direction .

The method may further comprise determining an optimum position along the first hori zontal direction using the sel fmixing interference signal after the target position in the first plane has been determined . According to embodiments , the relative position of the laser device and the optical waveguide element is changed in a periodic oscillating manner .

Further embodiments refer to an alignment device for aligning a laser device and an optical waveguide element . The laser device and the optical waveguide element are arranged in a spatial relationship, so that the laser device is configured to emit a laser beam to be incident on an input facet of the optical waveguide element , a first hori zontal direction corresponding to a direction between an output facet of the laser device and the input facet of the optical waveguide element . The alignment device comprises a control device configured to cause the laser device to emit the laser beam, a readout device configured to read out a sel f-mixing interference signal , and a movement control device configured to control an actuator configured to change a relative position of the laser device and the optical waveguide element The actuator is configured to change the relative position in the first hori zontal direction when the control device causes the laser device to emit the laser beam and the readout device reads out the sel f-mixing interference signal . The alignment device further comprises a processing device that is configured to determine an extremum of the sel f-mixing interference signal when the movement control device controls the actuator to change the relative position of the laser device and the optical waveguide element in a first plane perpendicular to the first hori zontal direction and to define a target position in the first plane as a position at which the extremum of the sel f-mixing interference signal is determined .

For example , the movement control device may be configured to control the actuator to move the laser device and to leave a position of the optical waveguide fixed . According to further embodiments , the movement control device is configured to move the optical waveguide and to leave a position of the laser device fixed .

For example , the readout device is configured to read out a j unction voltage of the laser device .

According to embodiments , the processing device is further configured to determine a target relative position of the laser device and the optical waveguide element in the first hori zontal direction .

According to embodiments , the movement control device may be further configured to control the actuator so that the relative position in the first hori zontal direction is changed . The processing device may be further configured to determine an optimum position along the first hori zontal direction using the sel f-mixing interference signal after defining the target position .

According to embodiments , the movement control device may be configured to control the actuator so that the relative position of the laser device and the optical waveguide element is changed in a periodic oscillating manner .

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this speci fication . The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles . Other embodiments of the invention and many of the intended advantages will be readily appreciated, as they become better understood by reference to the following detailed description . The elements of the drawings are not necessarily to scale relative to each other . Like reference numbers designate corresponding similar parts .

Fig . 1 illustrates elements of a photonic circuit for explaining an alignment method according to embodiments .

Fig . 2A shows a cross-sectional view of an optical waveguide element .

Fig . 2B shows a cross-sectional view of an optical waveguide element in a first hori zontal or longitudinal direction .

Fig . 2C illustrates an example of a sel f-mixing interference signal .

Fig . 3A illustrates an alignment process using an alignment device according to embodiments .

Fig . 3B illustrates an alignment process using an alignment device according to further embodiments .

Fig . 4A illustrates an alignment process using an alignment device according to further embodiments .

Fig . 4B illustrates an alignment process using an alignment device according to further embodiments .

Fig . 5 summari zes a method according to embodiments .

DETAILED DESCRIPTION In the following detailed description reference is made to the accompanying drawings , which form a part hereof and in which are illustrated by way of illustration speci fic embodiments in which the invention may be practiced . In this regard, directional terminology such as " top" , "bottom" , " front" , "back" , "over" , "on" , " above" , " leading" , " trailing" etc . is used with reference to the orientation of the Figures being described . Since components of embodiments of the invention can be positioned in a number of di f ferent orientations , the directional terminology is used for purposes of illustration and is in no way limiting . It is to be understood that other embodiments may be utili zed and structural or logical changes may be made without departing from the scope defined by the claims .

The description of the embodiments is not limiting . In particular, elements of the embodiments described hereinafter may be combined with elements of di f ferent embodiments .

As employed in thi s speci fication, the terms "coupled" and/or "electrically coupled" are not meant to mean that the elements must be directly coupled together - intervening elements may be provided between the "coupled" or "electrically coupled" elements . The term "electrically connected" may describe a low-ohmic electric connection between the elements electrically connected together .

According to further embodiments and where appropriate , the term "electrically connected" may mean that the respective elements are "directly connected" or are "directly and permanently connected" .

As will be described in the following, a method of manufacturing a photonic circuit comprises aligning a laser device and an optical waveguide element that is based on a sel f-mixing interference ef fect which is caused by a finite reflection of emitted laser radiation by an input facet of the optical waveguide element . During such an alignment , the laser device is caused to emit electromagnetic radiation which is detected e . g . by the laser device itsel f or by a photodetector mounted to the laser device . Accordingly, there is no need to additionally align a further photodetector which detects the electromagnetic radiation emitted to the optical waveguide element and transmitted by the optical waveguide element . Hence , active alignment may be performed in an easy manner .

Fig . 1 illustrates an example of a photonic circuit 10 comprising a laser device 110 and an optical waveguide element 105 . For example , the laser device 110 may be mounted on a submount 111 which may be attached to a carrier 112 , for example . The optical waveguide element 105 may be mounted over a waveguide substrate 100 . According to implementations , the waveguide substrate 100 may be mounted on the carrier 112 . According to further examples , the carrier 112 may form part of a general substrate , e . g . the waveguide substrate 100 . The laser device 110 and the optical waveguide element 105 are placed in a spatial relationship, so that the laser device 110 is configured to emit a laser beam to be incident on an input facet 107 of the optical waveguide element 105 .

A first hori zontal direction ( e . g . the x-direction) may correspond to a direction between an output facet 114 of the laser device and the input facet 107 of the optical waveguide element 105 . According to further interpretations , the first direction may correspond to the direction of a light beam emitted by the laser device 110 or to an optical acces s of the laser device 110 . According to still further implementations , the first direction may correspond to a shortest distance between the output facet of the laser device 110 and the input facet 107 of the optical waveguide element 105 . For example , the first hori zontal direction may correspond to a longitudinal direction of the optical waveguide element 105 .

For obtaining a sel f-mixing interference signal , a relative position of the laser device 110 and the optical waveguide element 105 in the first hori zontal direction is changed . At the same time , the laser device is caused to emit the laser beam . Further, a sel f-mixing interference signal is detected . The sel f-mixing interference signal is generated due to interference of the emitted laser beam 15 and a beam 16 that is reflected by the input facet 107 of the optical waveguide element 105 . An intensity of the sel f-mixing interference signal depends on the reflectivity of the input facet 107 of the optical waveguide element 105 . For example , the relative position of the laser device and the optical waveguide element may be changed by moving the laser device or the optical waveguide element in the first hori zontal direction . The movement may be performed so that the distance between the laser device 110 and the optical waveguide element 105 decreases and, thereafter increases , or vice versa . For example , this movement may be performed in an oscillating manner, e . g . in a periodic manner . An amplitude or maximum distance of movement in the first direction may be approximately /2 , wherein X denotes the wavelength of the emitted laser radiation . For example , the amplitude of the oscillation may be approximately 100 nm .

As will be explained in more detail with reference to Figs . 2A and 2B, the reflectivity at the input facet 107 of the optical waveguide element 105 achieves an extremum value when the emitted laser beam hits the center of the input facet 107 of the optical waveguide element 105 . Accordingly, by changing the relative position of the laser device 110 and the optical waveguide element 105 in a first plane perpendicular to the first direction, e.g. the y-z plane, and evaluating a selfmixing interference signal, a target position in the first plane may be determined. In particular, the target position corresponds to a position at which the self-mixing interference signal has an extremum of its amplitude. The target position corresponds to a position of perfect alignment of the relative lateral position within the first plane perpendicular to the first horizontal direction between the laser device 110 and the optical waveguide element 105.

Fig. 2A shows a cross-sectional view of an optical waveguide element 105 in a plane intersecting the first direction, e.g. the y-z plane. For example, the optical waveguide element 105 may be implemented as a rib waveguide. Fig. 2A shows the input facet 107 of the optical waveguide. For example, a material of the optical waveguide 101 may comprise SiN. According to the configuration of the rib waveguide, in a central portion 108, a height of the optical waveguide material 101 in the z- direction is larger than in an edge portion of the optical waveguide. A cladding material 102 having a refractive index smaller than that of the waveguide material 101 is arranged adjacent to the waveguide material 101. For example, a material of the cladding material may comprise silicon oxide. As is to be clearly understood, the optical waveguide element 105 may as well be implemented in a different manner and/or with different materials. For example, the optical waveguide element may be implemented as a suspended waveguide, a polymer waveguide, a step-index optical fiber, a graded-index optical fiber, a structured or photonic crystal fiber, and others.

According to further implementations, an anti-reflection coating 109 may be arranged over the input facet of the optical waveguide element 105. Fig. 2B shows a cross-sectional view of the optical waveguide element 105 in e.g. the x-z plane. As is shown, an anti-reflection coating 109 may be arranged adjacent to the input facet 107. When laser radiation is reflected by the facet 107, at positions of the waveguide material 101, the reflectivity of the laser radiation will be larger than at positions of the cladding material 102. Accordingly, when the laser radiation is reflected by the waveguide material 101, the reflectivity is higher.

An anti-reflection coating 109 may be implemented by or comprise X/4 layers, e.g. of a material having a lower refractive index than that of the waveguide material 101. For example, a material of the anti-reflection coating 109 may be similar or identical with a cladding material. At positions of the waveguide material 101, the anti-reflection coating 109 reduces the reflectivity of light to a large amount. At positions of the cladding material 102, the reflectivity is not considerably reduced. Accordingly, in case of the presence of an anti-reflection coating 109, the reflectivity is lower at positions of the waveguide material 101 compared to positions of the cladding material 102. Accordingly, an extremum, i.e. a minimum, of reflectivity is located at the input facet 107 of the waveguide material 101. Accordingly, a spatially inhomogeneous reflectivity along a direction perpendicular to the first horizontal direction may be used for determining an optimum position of the laser with respect to the input facet 107 based on the detection of self-mixing interference .

Fig. 2C shows an example of a self-mixing interference signal. As is schematically illustrated in Fig. 2C, the self-mixing interference signal shows periodicity which is e.g. determined in the present case by the periodic oscillating movement between laser device and input facet . Changes in the periodic signal encode information about the relative movement between laser and input facet . Moreover, the amplitude A of the sel fmixing interference signal varies depending on a reflectivity of the illuminated area of a target , here the input facet plane 107 . Accordingly, for example , when no anti-reflection coating 109 is present over the input facet 107 of the optical waveguide element , by determining a maximum of the sel f-mixing interference signal , an optimum position in the first plane may be determined . On the other side , i f an anti-reflection coating 109 is arranged over the input facet 107 , by determining a minimum amplitude of the sel f-mixing interference signal , an optimum position of the laser device may be determined in the first plane .

Fig . 3A illustrates a photonic circuit 10 during an alignment process using an alignment device 130 according to embodiments . As is shown in Fig . 3A, a laser device 110 may be placed over a submount 111 and may be electrically connected to a current source 137 . The submount 111 including the laser device 110 is arranged over a suitable carrier 112 . As is illustrated in Fig . 3A, a variable attachment material 125 is arranged between the submount 111 and the carrier 112 . Accordingly, a position of the laser device 110 with respect to the carrier 112 is not fixed but may be changed . The laser device 110 may be an arbitrary laser device including semiconductor lasers and other solid-state lasers . The laser device 110 may for example be an edge-emitting laser device or a surface-emitting device , e . g . a VCSEL ("vertical cavity surface-emitting laser" ) . The optical waveguide element 105 is arranged over a suitable waveguide substrate 100 . The waveguide substrate 100 may be attached to the carrier 112 using a fixed attachment material 126 . For example , a pos ition of the optical waveguide element 105 may be fixed with respect to the carrier 112 .

The laser device 110 and the optical waveguide element 105 are placed in spatial relationship, so that the laser device 110 is configured to emit a laser beam 15 to be at least partially incident on an input facet 107 of the optical waveguide element 105 .

According to embodiments illustrated in Fig . 3A, the laser device 110 may be implemented as a semiconductor device including a pn j unction, for example . Accordingly, this pn j unction may at the same time detect the sel f-mixing interference signal . For example , using a voltage measurement device 136 , the sel f-mixing interference signal may be detected . Since the sel f-mixing interference signal may be directly assessed from the pn j unction, there is no need to provide an additional photodetector .

Fig . 3A further shows an actuator 134 that may move the submount 111 carrying the laser device 110 in the first direction and further in a first plane . For example , the actuator may be implemented as a piezoelectric actuator . A movement control device 133 that may form part of the alignment device 130 may control a movement of the actuator and hence a movement of the laser device 110 in the first direction for performing the oscillating movement and further in the y- z plane to find the optimum interference signal . The first hori zontal direction may correspond to a direction between an output facet 114 of the laser device and an input facet 107 of the optical waveguide element 105 . The alignment device 130 further comprises a control device 131 that is configured to cause the laser device 110 to emit the laser beam 15 . The movement control device is configured to control the actuator 134 which is configured to change a relative position of the laser device and the optical waveguide element . The actuator is configured to change the relative position in the first hori zontal direction when the control device causes the laser device to emit the laser beam 15 . The readout device 132 reads out the sel f-mixing interference signal . The alignment device further comprises a proces sing device 135 which is configured to determine an extremum of the sel f-mixing interference signal when the actuator changes the relative position of the laser device and the optical waveguide element in a first plane perpendicular to the first hori zontal direction and to define a target position in the first plane as a position at which the extremum of the sel fmixing interference signal is determined .

Fig . 3B shows components of a photonic circuit 10 during an alignment process according to a further implementation . The components of the arrangement are similar to those illustrated in Fig . 3A. Di f fering from the arrangement illustrated in Fig . 3A, the laser device 110 further comprises a photodetector element 116 , e . g . a photodiode , which is configured to detect the sel f-mixing interference signal . As is illustrated in Fig . 3B, the photodetector element 116 may be a component separate from the laser device 110 . For example , this may be the case when the laser device 110 is not implemented as a laser device including a pn j unction, e . g . in a case in which the laser device 110 is a general solid-state laser . The photodetector element 116 may be arranged in a fixed spatial relationship to the laser device . For example , the photodetector element 116 may be attached to the laser device 110 . The further components and the functionality of the alignment device and the method are similar to those explained with respect to Fig . 3A. Since , as is illustrated in Fig . 3B, the photodetector element 116 is arranged in a fixed spatial relationship to the laser device 110, there is no need to perform a separate alignment process between the photodetector element 116 and the laser device 110.

According to embodiments illustrated in Figs. 3A and 3B, the laser device 110 is moved by the actuator 134. After finding a target position of the laser device 110 with respect to the optical waveguide element, according to embodiments illustrated in Figs. 3A and 3B, the variable attachment material 125 may be fixed, e.g. using a curing process.

Fig. 4A shows an arrangement of a laser device 110 and a waveguide element 105 when performing an alignment process according to further implementations. The arrangement of Fig. 4A is similar to the arrangement of Fig. 3A. Differing from the arrangement of Fig. 3A, according to Fig. 4A, the optical waveguide element 105 is moved while the laser device 110 is fixed. Further elements of the alignment process are similar or identical with the alignment process described with reference to Fig. 3A.

Fig. 4B illustrates an alignment process according to further implementations. Elements of the arrangement of Fig. 4B are identical or similar to those described with reference to Fig. 4A. Differing from the arrangement of Fig. 4A, a separate photodetector is provided to detect the self-mixing interference signal in a similar manner as has been explained with respect to Fig. 3B.

According to embodiments illustrated in Figs. 4A and 4B, the waveguide element 105 is moved by the actuator 134. After finding a target position of the optical waveguide element 105 with respect to the laser device 110, the variable attachment material 125 may be changed to a fixed attachment material, e.g. using a curing process.

According to further embodiments, after finding the target position in the first plane, the distance between the laser device 110 and the optical waveguide element 105 may be further changed to find an optimum distance. Generally, in a case a best optical coupling of light from the laser device 100 into the optical waveguide element 105 is desired, the optimum distance is distance zero. Hence, according to Figs. 3A, 3B, the laser device 110 may be moved closer to the input facet 107 of the optical waveguide element 105. The distance zero may be detected using the self-mixing interference signal ("SMI signal") . A contact of the laser device 110 and the optical waveguide element 105 may be detected by detecting a non-periodic abrupt change in the SMI signal. For example, spacer structures may be arranged on the optical waveguide element 105 in order to avoid facet damages when aligning the laser device 110 with respect to the optical waveguide element .

Fig. 5 summarizes a method of manufacturing a photonic circuit. The method may comprise placing (S100) a laser device and an optical waveguide element in a spatial relationship, so that the laser device is configured to emit a laser beam to be incident on an input facet of the optical waveguide element, a first horizontal direction corresponding to a direction between an output facet of the laser device and the input facet of the optical waveguide element. The method further comprises aligning (Slid) the laser device and the optical waveguide element. Aligning (Slid) comprises changing (S120) a relative position of the laser device and the optical waveguide element in the first horizontal direction while causing the laser device to emit the laser beam and detecting a sel f-mixing interference signal . Aligning further comprises determining ( S 130 ) an extremum of the sel f-mixing interference signal while changing the relative position of the laser device and the optical waveguide element in a first plane perpendicular to the first hori zontal direction and defining ( S 140 ) a target position in the first plane as a position at which the extremum of the sel f-mixing interference signal is determined .

As has been explained, the concept described allows for a simpli fied active alignment of laser devices 110 and optical waveguide elements 105 . The alignment process may be performed without the need of an additional photodetector that is separate from the laser device 110 and which needs to be aligned for each di f ferent optical path along the optical waveguide element 105 . A high-precision alignment is achieved by utili zing the highly sensitive interferometric laser feedback signal which is caused by a partial reflection at the input facet 107 of the optical waveguide element 105 . Accordingly, the alignment device may be compact and may be implemented at lower cost . Further, multiple laser devices may be aligned simultaneously since no separate devices , e . g . detectors , are necessary . The complexity of the method may be signi ficantly reduced . Hence , the time needed for alignment may also be reduced .

While embodiments of the invention have been described above , it is obvious that further embodiments may be implemented . For example , further embodiments may comprise any subcombination of features recited in the claims or any subcombination of elements described in the examples given above . Accordingly, this spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein . LIST OF REFERENCES photonic circuit laser beam reflected beam waveguide substrate waveguide material cladding material optical waveguide element input facet center of optical waveguide element anti-reflection coating laser device laser submount carrier output facet photodetector variable attachment material fixed attachment material alignment device control device readout device movement control device actuator processing device measurement device current source

Claims

1. A method of manufacturing a photonic circuit (10) comprising : aligning a laser device (110) and an optical waveguide element (105) , the laser device (110) and the optical waveguide element (105) being arranged in a spatial relationship, so that the laser device (110) is configured to emit a laser beam (15) to be incident on an input facet (107) of the optical waveguide element (105) , a first horizontal direction corresponding to a direction between an output facet (114) of the laser device (110) and the input facet (107) of the optical waveguide element (105) , wherein aligning comprises : changing a relative position of the laser device (110) and the optical waveguide element (105) in the first horizontal direction while causing the laser device to emit the laser beam (15) and detecting a self-mixing interference signal ; determining an extremum of the self-mixing interference signal while changing the relative position of the laser device (110) and the optical waveguide element (105) in a first plane perpendicular to the first horizontal direction, and defining a target position in the first plane as a position at which the extremum of the self-mixing interference signal is determined.

2. The method according to claim 1, wherein changing the relative position comprises moving the laser device (110) and leaving a position of the optical waveguide (105) fixed.

3. The method according to claim 1, wherein changing the relative position comprises moving the optical waveguide (105) and leaving a position of the laser device (110) fixed.

4. The method according to any of the preceding claims, wherein detecting a self-mixing interference signal comprises reading out a junction voltage of the laser device (110) .

5. The method according to any of the preceding claims, further comprising determining a target relative position of the laser device (110) and the optical waveguide element (105) in the first horizontal direction.

6. The method according to any of the preceding claims, further comprising arranging the laser device (110) and the optical waveguide element (105) in the spatial relationship before performing alignment.

7. The method according to any of the preceding claims, further comprising determining an optimum position along the first horizontal direction using the self-mixing interference signal after the target position in the first plane has been determined .

8. The method according to any of the preceding claims, wherein the relative position of the laser device (110) and the optical waveguide element (105) is changed in a periodic oscillating manner.

9. An alignment device (130) for aligning a laser device

(110) and an optical waveguide element (105) , the laser device

(110) and the optical waveguide element (105) being arranged in a spatial relationship, so that the laser device (110) is configured to emit a laser beam (15) to be incident on an input facet (107) of the optical waveguide element (105) , a first horizontal direction corresponding to a direction between an output facet (114) of the laser device (110) and the input facet (107) of the optical waveguide element (105) , the alignment device (130) comprising: a control device (131) configured to cause the laser device (110) to emit the laser beam (15) ; a readout device (132) configured to read out a selfmixing interference signal; a movement control device (133) configured to control an actuator (134) configured to change a relative position of the laser device (110) and the optical waveguide element (105) , the actuator (134) being configured to change the relative position in the first horizontal direction when the control device (131) causes the laser device (110) to emit the laser beam (15) and the readout device (132) reads out the self-mixing interference signal; a processing device (135) configured to determine an extremum of the self-mixing interference signal when the movement control device (133) controls the actuator (134) to change the relative position of the laser device (110) and the optical waveguide element (105) in a first plane perpendicular to the first horizontal direction and to define a target position in the first plane as a position at which the extremum of the self-mixing interference signal is determined.

10. The alignment device (130) according to claim 9, wherein the movement control device (133) is configured to control the actuator (134) to move the laser device (110) and to leave a position of the optical waveguide (105) fixed.

The alignment device (130) according to claim 9, wherein the movement control device (133) is configured to move the optical waveguide (105) and to leave a position of the laser device (110) fixed.

12. The alignment device (130) according to any of claims 9 to 11, wherein the readout device (132) is configured to read out a junction voltage of the laser device (110) .

13. The alignment device (130) according to any of claims 9 to 12, wherein the processing device (135) is further configured to determine a target relative position of the laser device (110) and the optical waveguide element (105) in the first horizontal direction.

14. The alignment device (130) according to any of claims 9 to 13, wherein the movement control device (133) is further configured to control the actuator (134) so that the relative position in the first horizontal direction is changed, wherein the processing device (135) is further configured to determine an optimum position along the first horizontal direction using the self-mixing interference signal after defining the target position .

15. The alignment device (130) according to any of claims 9 to 14, wherein the movement control device (133) is configured to control the actuator (134) so that the relative position of the laser device (110) and the optical waveguide element (105) is changed in a periodic oscillating manner.