DE102019115306A1 - Manufacturing method for an optical coupling element for use in a vehicle - Google Patents

Abstract

The present invention relates to a production method for an optical coupling-in element intended for use in a vehicle, the coupling-in element being designed to couple laser light from at least one fiber into at least one waveguide, the production method having the following process steps: providing at least one fiber, at least one waveguide and a carrier substrate (100); Attaching the at least one fiber and the at least one waveguide to a surface of the carrier substrate (200); Depositing a polymer spacer in the space on the surface of the carrier substrate (300); and structuring, by means of a laser, a 3D waveguide in the polymer intermediate piece (400). The present invention also relates to an optical coupling element produced by steps of the production method. The present invention also relates to a vehicle with the coupling element. The invention also relates to a laser scanner with the coupling element. Furthermore, the present invention relates to a computer program comprising instructions which, when the computer program is executed by a computer, cause the computer to execute steps of the manufacturing method. The present invention also relates to a data carrier signal which the computer program transmits. The present invention also relates to a computer-readable medium, comprising instructions which, when executed by a computer, cause the computer to carry out steps of the manufacturing method.

Description

The present invention relates to a production method for an optical coupling-in element provided for use in a vehicle, the coupling-in element being designed to couple laser light from at least one fiber into at least one waveguide. The coupling element can be used, for example, to couple light into a laser scanner, which is used in the vehicle to detect properties of the surroundings of the vehicle.

The present invention also relates to an optical coupling element produced by steps of the production method.

The present invention also relates to a vehicle with the optical coupling-in element and a laser scanner with the optical coupling-in element.

Furthermore, the present invention relates to a computer program comprising instructions which, when the computer program is executed by a computer, cause the computer to execute steps of the manufacturing method.

The present invention also relates to a data carrier signal which the computer program transmits.

The present invention also relates to a computer-readable medium, comprising instructions which, when executed by a computer, cause the computer to carry out steps of the manufacturing method.

In the DE 10 2016 118 539 A1 discloses a taper as a coupling element for coupling laser light into a waveguide as a deflection unit for a laser scanner. The coupling element is used for a system comprising a scanning unit for an optical transmission device of an optical detection device. The scanning unit comprises at least one beam influencing device for deflecting at least one light beam radiated into an inlet of the scanning unit and at least one coupler for introducing the at least one light beam into the at least one beam influencing device. The at least one coupler has or consists of at least one beam tapering device for tapering a cross section of the at least one light beam.

In the case of the taper as a coupling element of the prior art, when the taper is introduced into the overall optical system, optical components have to be aligned, which complicates the manufacturing process.

Based on the above-mentioned prior art, the invention is based on the object of providing an improved manufacturing method for an optical coupling element for use in a vehicle, an improved optical coupling element, a vehicle with such an improved coupling element, a correspondingly improved computer program, a corresponding specify improved data carrier signal and a correspondingly improved computer-readable medium. In particular, the production method for the optical coupling element for use in the vehicle should be simpler.

The object is achieved according to the invention by the features of the independent claims. Advantageous embodiments of the invention are specified in the subclaims.

According to the invention, a production method for an optical coupling-in element intended for use in a vehicle is thus specified, the coupling-in element being designed to couple laser light from at least one fiber into at least one waveguide, the production method comprising the following method steps: providing at least one fiber, at least one waveguide and a carrier substrate; Fixing the at least one fiber and the at least one waveguide on a surface of the carrier substrate with the formation of a gap between at least one fiber output of the at least one fiber and at least one waveguide input of the at least one waveguide; Applying a polymer spacer into the space on the surface of the carrier substrate such that the polymer spacer is in direct contact with the at least one fiber output and the at least one waveguide input; and structuring, by means of a laser, a 3D waveguide in the polymer intermediate piece, the 3D waveguide extending from the at least one fiber output to the at least one waveguide input and connecting the at least one fiber output to the at least one waveguide input.

According to the invention is also an optical coupling element, for. B. for a laser scanner, in a vehicle, having properties generated by manufacturing method steps described above or mentioned below as advantageous.

A vehicle with the optical coupling element is also specified according to the invention. The vehicle is preferably a driver's ego vehicle.

In addition, a laser scanner with the optical coupling element is specified according to the invention.

Furthermore, according to the invention, a computer program is specified, comprising commands which, when the computer program is executed by a computer, cause the computer to carry out steps of the manufacturing method. A computer program is a collection of instructions for performing a particular task, designed to solve a particular class of problems. A program's instructions are designed to be carried out by a computer and it requires a computer to be able to run programs in order for it to function.

According to the invention, a data carrier signal is also specified, which the computer program transmits.

Furthermore, according to the invention, a computer-readable medium is specified, comprising instructions which, when executed by a computer, cause the computer to execute steps of the manufacturing method.

The basic idea of the present invention is therefore to provide a coupling element for coupling laser light into a waveguide, e.g. B. as a deflection unit for a laser scanner. In particular, laser light from a fiber is coupled into the waveguide by means of the coupling element. In the process, fibers and waveguides are arranged on a common carrier substrate. A corresponding polymer is applied to the carrier substrate between the fiber and the waveguide, the polymer being in direct contact with the fiber outlet and the waveguide inlet. The 3D waveguide is then written into the polymer using a laser.

3D waveguides are in one, e.g. B. at a wavelength in a range from 750 nm to 850 nm, transparent material introduced structures which are generated by local heating and an associated local change in the refractive index in the transparent material. For example, 3D waveguides can be introduced into a volume of the transparent materials by focusing laser radiation that is pulsed in femtoseconds. The energy of the laser radiation is absorbed by non-linear processes in a small volume within the beam focus. As a result, a volume of the transparent material limited to an order of magnitude of a few cubic micrometers is briefly heated strongly and the material is melted locally. After solidification, an area with a higher refractive index than the surrounding material can result. If the focus of the laser radiation is moved in the volume of the transparent material, three-dimensional structures with the increased refractive index are generated, which act as light guides. These light guides are 3D waveguides.

The 3D waveguide is, for example, a monomodal waveguide made of polymer, i. H. a singlemode polymer waveguide. In order to be able to produce a singlemode polymer waveguide with sufficient refractive index contrast, for example a polymer of the type described below is locally hardened by three-dimensional direct laser writing (DLW) and then a guest monomer with a lower index is diffused into an uncured photopolymer matrix. For the manufacturing concept described above, z. B. used an epoxy-based photopolymer. Its main component is an oligomer based on a bisphenol-A diglycidyl ether. In addition to a photoinitiator, the photopolymer also contains a γ-butyrolactone (GBL) solvent, which enables the formation of defect-free layers with a uniform distribution of the polymer film on the carrier substrate, e.g. B. by spin coating, made possible. The polymer film is highly transparent at 780 nm, but sensitive to 365 nm light. UV curing at 365 nm wavelength lowers the refractive index of the uncured film by 0.003. In order to obtain sufficient index contrast for optical waveguides, external diffusion of an aliphatic guest monomer is used, which leads to a drop in the refractive index of 0.016. This reduction is due to the lower index of the guest monomer (e.g. in a value range of 1.45) compared to the carrier oligomer (e.g. in a value range of 1.59). Furthermore, the index of the cured film hardly changes after the diffusion process of the guest monomer. In other words, the gaseous monomer hardly diffuses into the polymerized crosslinked film. The concept of this difference in index contrast generation in the uncured and cured film is an exemplary possibility for the production of 3D buried waveguides by means of multiple photon lithography, also known as multiphoton lithography.

Multiphoton lithography is also known as direct laser lithography or direct laser writing. Similar to standard photolithography, structuring is achieved by illuminating negative or positive photographic films with light of a precisely defined wavelength.

The invention has the advantage that no optical system is required. Furthermore is no alignment of optical components required as the positions of the fiber and waveguide, e.g. B. as part of a one-chip system (System on a Chip (SoC)), can be detected during the manufacture of the optical coupling element. The manufacturing process on a SoC is also called an in-situ process. Furthermore, the manufacturing process is easy to industrialize. The coupling structure of the optical coupling element can be designed flexibly. For example, the structure can be designed as a waveguide, a distributor, or a cone. Finally, the structure is written three-dimensionally with full free-form capability and can be adapted as required to the positioning, alignment and design of the fiber output and the waveguide input.

According to an advantageous embodiment of the invention it is provided that the at least one fiber is part of a fiber laser, at least one light exit surface of the fiber laser being arranged on the surface of the carrier substrate forming the space between the fiber laser and at least one waveguide entrance. A fiber laser is a solid-state laser. The fiber laser includes, for example, a doped core of a glass fiber as the active medium. Fiber lasers are z. B. optically pumped by radiation from diode lasers being coupled into the fiber cladding or into the fiber core parallel to the fiber core. For example, erbium, ytterbium and neodymium are used for doping the laser-active fiber core. Fiber lasers have electrical-optical efficiencies of up to 30%, a beam quality with M ² <1.1 for the single-mode fiber laser structure or M ² <1.2 for double-clad fibers, long lifetimes that can be longer than 20,000 h and a compact, maintenance-free and insensitive construction. Fiber lasers can be operated in pulse mode down to the femtosecond range.

According to an advantageous embodiment of the invention it is provided that the waveguide is part of a one-chip system (SoC), the SoC on the surface of the carrier substrate forming the space between the at least one fiber exit of the at least one fiber and at least one light entry surface of the SoC is arranged. A one-chip system is a system in which all or some of the functions of a programmable electronic system are integrated on one chip. The aforementioned advantageous embodiment enables a compact design and also facilitates assembly.

According to an advantageous embodiment of the invention, it is provided that the following steps are carried out to apply the polymer spacer to the carrier substrate: applying a monolithic polymer film to the carrier substrate; uniform distribution of the polymer film on the carrier substrate; and solidifying the polymer film, in particular for at least one hour, when the carrier substrate is placed on a heating plate. In the steps described above, customary fabrication systems for applying and solidifying polymer films can be used, which thus enables inexpensive production.

According to an advantageous embodiment of the invention, it is provided that the following steps are carried out for structuring the 3D waveguide: structuring of a core trajectory in the polymer intermediate piece using 3D laser lithography with multiphoton absorption; for at least partially curing the polymer spacer, baking at 60 ° C for 10 minutes; Treating the polymer spacer in a chamber such that external diffusion of a gaseous monomer occurs in an uncured portion of the polymer spacer; UV exposure of the polymer spacer to radiation having a wavelength of 365 nm; and hard baking such that an assembly of the polymer spacer and the carrier substrate is stabilized. In other words, the manufacturing steps described above are part of a rapid prototyping process, in which the manufacturing steps can be programmed by a computer and thus reproduced.

According to an advantageous embodiment of the invention it is provided that the coupling element is designed as a deflection unit for a laser scanner. According to an advantageous embodiment of the invention it is provided that the laser scanner is a LiDAR scanner. LiDAR (light detection and ranging), also Ladar (laser detection and ranging), is a radar-related method for optical distance and speed measurement as well as for remote measurement of atmospheric parameters. LiDAR systems send out laser pulses and detect the backscattered light. The distance to the point of scattering is calculated from the light transit time of the signals.

According to an advantageous embodiment of the invention it is provided that the 3D waveguide is designed as a splitter and / or as a taper. A splitter, also called a beam splitter, is an optical component that separates a single light beam into two partial beams. A taper is an optical component that connects two optical fibers with different radii. The power transmission of a taper between waveguides of the same numerical aperture (NA) in the direction of the smaller radius takes place in such a way that light of a waveguide with a large core cross-section is released from the waveguide with a smaller cross-section is removed, which does not find space in the waveguide of smaller cross section. This also applies to conical tapers. On the other hand, all light from a thinner waveguide can pass into a thicker waveguide of the same NA.

According to an advantageous embodiment of the invention, it is provided that the 3D waveguide is formed at least as one of the following elements and / or comprises the following elements: a waveguide array; a fan coupling and decoupling, which is designed in particular with three or four channels; and / or an optical router. In other words, any adaptation of the 3D waveguide to the optical connections of the fiber and the waveguide is possible.

According to an advantageous embodiment of the invention, it is provided that the material of the polymer intermediate piece is a resin or a photopolymer. The photopolymer can be of the type described above. The aforementioned types of polymer are particularly suitable for producing a 3D waveguide.

The invention is explained in more detail below with reference to the attached drawing using preferred embodiments. The features shown can represent an aspect of the invention both individually and in combination. Features of various exemplary embodiments can be transferred from one exemplary embodiment to another.

• 1 Ein Flussdiagramm gemäß einer Ausführungsform des erfindungsgemäßen Herstellungsverfahrens,
• 2 eine schematische Draufsicht auf ein Einkoppelelement in einem ersten Stadium des Herstellungsverfahrens,
• 3 eine schematische Draufsicht auf ein Einkoppelelement in einem zweiten Stadium des Herstellungsverfahrens und
• 4 eine schematische Draufsicht auf ein Einkoppelelement in einem dritten Stadium des Herstellungsverfahrens.

It shows

• 1 A flow chart according to an embodiment of the production method according to the invention,
• 2 a schematic plan view of a coupling element in a first stage of the manufacturing process,
• 3 a schematic plan view of a coupling element in a second stage of the manufacturing process and
• 4th a schematic plan view of a coupling element in a third stage of the manufacturing process.

The 1 shows a flow chart according to an embodiment of the production method according to the invention for an optical coupling element 1 (please refer 4th for a possible embodiment of a coupling element 1 , which is shown schematically in this figure) for use in a vehicle. The coupling element 1 is designed to couple laser light from at least one fiber 2 in at least one waveguide 3 .

The manufacturing process has the following manufacturing process steps: First, in one step, " 100 “Providing at least one fiber 2 , at least one waveguide 3 and a carrier substrate 4th (see also 2 in what fiber 2 and waveguides 3 already on the carrier substrate 4th are arranged).

Then in one step " 200 “Attaching the at least one fiber 2 and the at least one waveguide 3 on a surface of the carrier substrate 4th forming a space between at least one fiber exit 2a of at least one fiber 2 and at least one waveguide input 3a of the at least one waveguide 3 .

Then in one step " 300 “The application of a polymer spacer 5 into the space on the surface of the carrier substrate 4th such that the polymer spacer 5 in direct contact with the at least one fiber exit 2a and the at least one waveguide input 3a is (see also 3 ).

Finally, in one step " 400 “The structuring, by means of a laser, of a 3D waveguide 6 in the polymer spacer 5 , wherein the 3D waveguide 6 extends from the at least one fiber output 2a up to the at least one waveguide input 3a extends and the at least one fiber output 2a with the at least one waveguide input 3a connects (see also 4th ).

In particular, it is provided in the production method that the at least one fiber 2 Part of a (not shown) fiber laser, the fiber laser on the surface of the carrier substrate 4th with the formation of the gap between the fiber laser and at least one waveguide input 3a to be arranged.

In the embodiment of the coupling element 1 the 4th is the waveguide 3 Part of a one-chip system (SoC), with the SoC 7 on the surface of the carrier substrate 4th forming the space between at least one fiber exit 2a and the SoC 7 (see 2 and 3 ). Here is in the embodiment of 2 to 4th the space between a single fiber exit 2a the fiber 2 and a single light entry surface of the SoC 7 is formed.

It is also provided that for applying the polymer spacer 5 onto the carrier substrate 4th in step " 300 "The following steps are carried out: According to a step" 310 “A monolithic polymer film is applied to the carrier substrate 4th . According to a step "320" the polymer film is evenly distributed on the carrier substrate 4th . According to one step " 330 “The polymer film solidifies for at least one hour when the carrier substrate is in place 4th on a hot plate.

To structure the 3D waveguide 6 in the step " 400 "The following steps are also carried out: According to a step" 410 “A core trajectory is structured in the intermediate polymer piece 5 using 3D laser lithography with multiphoton absorption. According to one step " 420 “Takes place to at least partially harden the polymer spacer 5 , Bake at 60 ° C for 10 minutes. According to one step " 430 “The polymer spacer is treated 5 , in a chamber such that there is external diffusion of a gaseous monomer in an uncured portion of the polymer spacer 5 he follows. According to one step " 440 “UV exposure of the polymer spacer takes place 5 with radiation with a wavelength of 365 nm. According to a step " 450 “A hard baking takes place in such a way that a stabilization of an assembly from the polymer spacer 5 and the carrier substrate 4th he follows.

The production method described above is explained again in detail below.

A multiphoton lithography technique is used to structure the 3D waveguide 6. One example of a lithography technique of the aforementioned type is two-photon lithography. This is a rapid prototyping technique that enables the production of submicron 3D structures in photographic films, e.g. B. a photopolymer, allows. In the two-photon lithography z. B. erbium-doped fiber lasers are used, which emit ultra-short pulses of 100 femtoseconds at 780 nm wavelength with a repetition rate of 80 MHz. An acousto-optic modulator (AOM) is used to control the optical power to a maximum of 70 mW. The laser beam is expanded before it is split into an objective and a detector arrangement. The former is an objective with a 63x magnification and a numerical aperture of 0.75. The latter recognizes sample interfaces and corrects its angle of inclination via the intensity of the reflected light. A piezoelectric 3D scanning table drives the sample and tracks the coordinates given by the computer.

The depth of the laser focus inside the film is calculated taking into account the aberration correction and diffraction at the air / lacquer surface, which is done by means of calculation methods known to the person skilled in the art, in particular using Snellius's law.

The manufacturing process of the 3D waveguide includes, for example, the following steps: casting, three-dimensional direct laser writing, heat treatment, external monomer diffusion and flood UV exposure with hard baking.

After spin coating on a 2 inch silicon wafer, the gel-like polymer is solidified on a hot plate for several hours. The film adheres to silicon wafers without an adhesion promoter. The time and temperature for a soft-bake step are then selected in such a way that the solvent concentration is controlled and a tack-free surface is made available. Then a two-photon lithography takes place according to a programmed trajectory and initiates the cross-linking to form the waveguide core. Baking at 60 ° C for 10 minutes after exposure accelerates crosslinking in an exposed volume of the film. The writing speed varies from 0.1 to 1 mm / s, and the intensity of the input laser is between 5 and 40 mW, resulting in different doses for the crosslinking process. This is followed by external diffusion of a gaseous low-index monomer into the uncured coating in a closed chamber at room temperature. The diffusion time varies from 96 to 168 hours for diffusion depths in the range of 40-70 micrometers. The UV flood exposure at 365 nm crosslinks the diffused monomer and host oligomer by means of single photon absorption. Finally, the hard baking of the sample at 140 ° C for 10 minutes hardens the coating completely and stabilizes the embedded waveguide. The incorporation of the guest monomer (e.g. with a refractive index of nD 1.445) into the host oligomer (with a refractive index of nD 1.59) matrix reduces the refractive index of the cladding, which results in an increased index contrast between core and cladding for light guidance.

This manufacturing process has various advantages over other waveguide manufacturing processes. Only one layer of a single material is required. Multi-layer waveguides can be labeled in a single writing step without stacking or alignment effort. After all, this rapid prototyping technique does not contain any masks, no more contact or wet chemical process steps such as wet etching.

List of reference symbols

1

Coupling element

2

fiber

2a

Fiber output

3

Waveguide

3a

Waveguide input

4th

Carrier substrate

5

Polymer spacer

6th

3D waveguide

7th

One chip system

100

Providing at least one fiber, at least one waveguide and a carrier substrate

200

Securing the at least one fiber and the at least one waveguide on a surface of the carrier substrate

300

Applying a polymer spacer in the space on the surface of the carrier substrate

310

Application of a monolithic polymer film to the carrier substrate

320

Uniform distribution of the polymer film on the carrier substrate

330

Solidifying the polymer film for at least one hour when the carrier substrate is placed on a hot plate

400

Structuring, by means of a laser, a 3D waveguide in the polymer intermediate piece

410

Structuring a core trajectory in the polymer interface using 3-D laser lithography with multiphoton absorption

420

for at least partially curing the polymer spacer, baking at 60 ° C for 10 minutes

430

Treating the polymer spacer in a chamber

440

UV exposure of the polymer spacer to radiation having a wavelength of 365 nm

450

hard baking

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102016118539 A1 [0007]

Claims (15)

Production method for an optical coupling element (1) intended for use in a vehicle, the coupling element (1) being designed to couple laser light from at least one fiber (2) into at least one waveguide (3), the production method having the following method steps having: - Providing at least one fiber (2), at least one waveguide (3) and a carrier substrate (4) (100); - Fastening the at least one fiber (2) and the at least one waveguide (3) on a surface of the carrier substrate (4) with the formation of a space between at least one fiber output (2a) of the at least one fiber (2) and at least one waveguide input ( 3a) of the at least one waveguide (3) (200); - Application of a polymer intermediate piece (5) in the space on the surface of the carrier substrate (4) such that the polymer intermediate piece (5) is in direct contact with the at least one fiber output (2a) and the at least one waveguide input (3a) ( 300); and - Structuring, by means of a laser, a 3D waveguide (6) into the polymer intermediate piece (5), the 3D waveguide (6) extending from the at least one fiber output (2a) to the at least one waveguide input (3a) and the at least one fiber output (2a) connects (400) to the at least one waveguide input (3a). Manufacturing process according to Claim 1 , wherein the at least one fiber (2) is part of a fiber laser, the fiber laser being arranged on the surface of the carrier substrate (4) forming the space between at least one light exit surface of the fiber laser and the at least one waveguide input (3a). Manufacturing process according to Claim 1 or 2 , wherein the waveguide (3) is part of a one-chip system, SoC, (7), the SoC (7) on the surface of the carrier substrate (4) forming the space between at least one fiber output (2a) and at least one Light entry surface of the SoC (7) is arranged. Manufacturing method according to at least one of the preceding claims, wherein the following steps are carried out to apply the polymer intermediate piece (5) to the carrier substrate (4) (300): - Application of a monolithic polymer film to the carrier substrate (4) (310); - Uniform distribution of the polymer film on the carrier substrate (4) (320); and - Solidification of the polymer film, in particular for at least one hour, when the carrier substrate (4) is placed on a heating plate (330). Manufacturing method according to at least one of the preceding claims, wherein the following steps are carried out for structuring the 3D waveguide (6) (400): - structuring a core trajectory in the polymer intermediate piece (5) using 3D laser lithography with multiphoton absorption (410); - for at least partial curing of the polymer intermediate piece (5), baking at 60 ° C. for 10 minutes (420); - treating the polymer intermediate piece (5) in a chamber (430) in such a way that an external diffusion of a gaseous monomer takes place in an uncured part of the polymer intermediate piece (5); - UV exposure of the polymer intermediate piece (5) to radiation with a wavelength of 365 nm (440); and - hard baking (450) in such a way that an assembly consisting of the polymer intermediate piece (5) and the carrier substrate (4) is stabilized. Manufacturing method according to at least one of the preceding claims, wherein the coupling element (1) is designed as a deflection unit for a laser scanner. Manufacturing method according to at least one of the preceding claims, wherein the 3D waveguide (6) is designed as a splitter and / or as a taper. Manufacturing method according to at least one of the preceding claims, wherein the 3D waveguide (6) is designed as at least one of the following elements and / or comprises the following elements: a waveguide array; a fan coupling and decoupling, which is designed in particular with three or four channels; and / or an optical router. Manufacturing method according to at least one of the preceding claims, wherein the material of the polymer intermediate piece (5) is a resin or a photopolymer. Optical coupling element (1) for a laser scanner in a vehicle, having properties generated by method steps according to at least one of the preceding claims. Vehicle having a laser scanner with an optical coupling element (1) according to the preceding claim. Laser scanner with the optical coupling element (1) provided for use in a vehicle Claim 10 . Computer program, comprising instructions that are used in the execution of the computer program cause a computer to execute a manufacturing method according to at least one of the preceding claims. Data carrier signal which the computer program according to the preceding claim transmits. Computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out a manufacturing method according to at least one of the preceding claims.

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