DE102009023071A1 - Micro-optical coupling element for orthogonal or diagonal micro-optical coupling of optical radiation, has base body formed from layer of thin glasses and exhibiting additional layers with electrical and/or fluid function - Google Patents

Abstract

The element has optical wave guides (5) for guiding of optical radiation (3) that enters via inlet surfaces in a base body, where the wave guides are integrated into the base body. A deflection element (4) is integrated in the base body for deflecting the optical radiation. The base body is formed from a layer of thin glasses and exhibits additional layers that exhibit an electrical and/or fluid function. A set of optical lenses i.e. focusing lenses (6), are integrated in the base body at outlet surfaces for the optical radiation and/or at the inlet surfaces.

Description

Technical application

The The present invention relates to a micro-optical coupling element, especially for an orthogonal or oblique Microoptical coupling of optical radiation from a on or multi-line optical transmitter array in a single or multi-line optical receiver array. In the optical transmitter array For example, it may be a VCSEL array (VCSEL: Vertical Cavity Surface Emitting Laser) or a waveguide array of a connector (eg fiber connector) act. The optical receiver array can, for example, by waveguides of an optical single or multi-layer substrate be formed, wherein the coupling over the end face or via coupling structures, for example via a grating formed on the surface of the waveguides. Applications for this so-called "out of plane coupling ", for example, to electro-optical modules and passive optical Connectors are in the field of silicon photonics, the CCD chip coupling of waveguides in the housing on Wafer level, in the area of the use of electro-optical boards or PCBs, nanophotonics and optical sensors. Essential is that the light path in principle also reversed or bidirectional can be.

State of the art

For the oblique coupling and decoupling of optical radiation into optical waveguides, which may extend, for example, on the surface of semiconductor substrates, techniques such as prism coupling or lattice coupling are currently known. An overview of these techniques give, for example. GT Reed et al., Silicon Photonics, Wiley, 2004, pp. 76-91 ,

For the coupling of an optical fiber or an optical fiber array is due to the increasing miniaturization of the structures of the semiconductor chips as well as the electro-optical circuit boards a high accuracy required in order to be able to couple with low coupling losses. This accuracy is not with the previously known techniques satisfactorily achieved or requires very complex adjustments. For photonic chips and PLC (Planar Lightguide Circuits) so-called single-mode waveguide with optical core diameters used from sub-micron to a few microns at Electro-optic printed circuit boards Multimode waveguides with core diameters in the range of a few tens of μm. Also the increasingly smaller Pitch distance down to 25 microns on the semiconductor chips or of currently at least 62.5 microns in electro-optical circuit boards requires a high accuracy of coupling, as it deals with do not reach the currently known coupling techniques leaves.

The US 7366380 B1 describes a micro-optical coupling element with a thin body made of a transparent material, in which one or more optical waveguides for the guidance of optical radiation and at least one deflection element for the deflection of the optical radiation are integrated. With this coupling element, optical fibers can be coupled to optoelectronic circuits.

The The object of the present invention is to provide a multifunctional Specify micro-optical coupling element, which provides high precision the coupling between a single or multi-line optical transmitter array and a single or multi-line optical receiver array allows and can be produced inexpensively.

Presentation of the invention

The Task is with the micro-optical coupling element according to claim 1 solved. Advantageous embodiments of this coupling element are Subject of the dependent claims or can be the following description and the embodiments remove.

The micro-optical coupling element is formed from a basic body, in the one or more optical waveguides for the guide the optical radiation and at least one deflecting element for the deflection of the optical radiation are integrated. The above one or more entry surfaces in the body occurred optical radiation is through the or the optical Waveguide and the at least one deflecting element from the entry surfaces to one or more exit surfaces of the body guided. The basic body here is at least a layer of thin glass formed in which the or optical waveguide and the deflecting element are integrated, and includes one or more additional layers that have an electrical and / or fluidic function.

The use of thin glass allows the integrated optical waveguides and, optionally, other optical elements which can be generated by local refractive index change to be fabricated with microstructure techniques, as are known from semiconductor technology, with high precision. Due to this high precision, the coupling element can be adapted exactly to the transmitter and receiver array, so that high coupling efficiencies are achieved. The individual structures can be produced here with photolithographic accuracy. In the case of semiconductor structures as a transmitter or receiver array, it is possible here to apply the coupling element to the semiconductor structures already at the wafer level (WLP). This can be successful, for example, by means of direct bonding The thin glass simultaneously serves as a substrate for further layers which have an electrical and / or fluidic function. In this way, a platform is created with the coupling element, which can produce not only optical but also fluidic and / or electrical connections.

The for the production of the coupling element usable methods the microstructuring continue to allow a high Miniaturization and integration density, so that also a coupling on transmitter or receiver arrays with a small pitch (≤ 250 μm up to 25 microns) can be readily realized. Also a coupling of arrays with different pitch leaves can be realized with the coupling element readily. To do this the optical waveguides so in the layer of thin glass creates a bigger one at one end of the layer have mutual distance as at the other end to a suitable Fanning, a so-called fan-out to achieve. One particular advantage is that the coupling element in shape the one or more layers of thin glass directly on the transmitter or receiver array can be applied. With this coupling element is on the one hand a single or multi-line orthogonal or oblique interconnection between transmitter and receiver array possible. On the other leaves through the largely free structurability of the optical Waveguide and possibly other optical elements of the coupling element the micro-optical geometric transmission or reception behavior of Transmitter arrays or receiver arrays on a larger scale transform to technologically induced coupling losses in mutual Positioning the transmitter and receiver array with tolerances, as they are z. B. in the PCB assembly technology or connector technology are found to be kept to a minimum. The on pages required by the transmitter and receiver arrays optical Field distributions can be achieved through targeted influencing the properties of the respective ends of the waveguides in the coupling element, in particular via the refractive index distribution and the waveguide geometry, targeted to adjust. The proposed coupling element can be also realize very flat on the transmitter array, since it is in planar technology can be produced.

In a preferred embodiment of the micro-optical coupling element is at the exit surface (s) and / or at the or the entrance surfaces in each case an optical lens, in particular a focusing lens, integrated into the body. this makes possible the targeted collimation of divergent optical rays of a single or multi-line optical transmitter arrays and / or focusing on the entry surfaces of a single or multi-line receiver array.

In a preferred embodiment, the one or more optical waveguides are produced by ion exchange from the molten glass in the thin glass. In the same way, other optical elements, such as. Focusing lenses on the generation of suitable refractive index gradients can be integrated with this technique in the thin glass. Thin glass in the present patent application is understood to mean thin glass substrates, as used, for example, for flat screens. Such thin glasses are commercially available and have a thickness of ≤ 2 mm. Thus, for example, thin glass substrates from Schott can be used under the name D263T ^™ with a thickness between 0.03 and 1.1 mm for the proposed coupling element. The integration of the waveguides can be done with the technique of silver ion exchange, in which after the application of a mask layer of a suitable alloy on the thin glass and subsequent photolithographic patterning of this mask layer, the thin glass substrate is introduced at a temperature of 350 ° C in molten salt. As a result of the diffusion process, a change in the refractive index is achieved at the regions predetermined by the mask structure, through which the waveguide structures are produced in the thin glass. In the same way, it is also possible to produce optical lenses in thin glass. Furthermore, this technique also allows lithography on both sides to produce, for example, two superimposed waveguide structures or layers of waveguides in a single layer of thin glass.

The Deflection element is preferably by an obliquely cut and polished end surface of the thin glass layer educated. This sloping end surface can also be added be mirrored. Of course, besides oblique Endflächenpoluren, if necessary with Verspiegelung, also other kinds Of deflectors possible, such as. Grid, photonic Bandgaps (PBG) or other types of reflectors. The integrated waveguides can be side by side in a single thin glass layer or on top of each other in several superimposed layers of these thin glass layers be realized. It can be both multimode and to trade singlemode waveguides.

The Waveguides preferably each have at least two waveguide sections on, between which the deflecting element is formed. The first Waveguide section guides the incoming optical radiation in a first direction to the deflecting element, this radiation in a second direction, in which they then through the second Waveguide section led to the exit surface becomes.

The waveguides integrated in the thin glass layer or layers can be continuous Ka Waveguide periodically interrupted channel waveguide, lens waveguide and optical radiation with a Gaussian field distribution and aperture be waveguide. Waveguide intersections with different waveguide types are also possible.

at the proposed coupling element can in the body in addition also layers of other materials integrated be. The term body is here to be understood as that this does not have to consist purely of thin glass layers. The basic body can by a structure of several optically be formed functional layers in which the structures for Waveguide and the deflection of the optical radiation are produced. These optically functional layers can be made of thin ones Glass films, polymer films and photolithographically structurable Layers exist. In addition to the optically functional layers and structures The basic body also contains in an alternative one or more electrically functional layers, eg. For Ankontaktierung of sensor elements or system components when the coupling element serves as a substrate in the sense of a system-to-package (SoP). In a another alternative, at least one more layer is structured that it has a fluidic function, for example a fluidic connection via integrated fluid channels, can produce.

preferred Technologies for structuring the optical layers are the Ion exchange, etching, laser cutting and heat polishing with lasers, photolithographic processes, mechanical polishing processes as well as metallizing and potting of embossed, etched and photolithographically produced structures.

The Process technology for the production of the coupling element allows also a parallel production on large-format thin glass, then to provide the individual coupling elements to be isolated. This allows a cost-effective Production. Due to the possibility of photolithographic Techniques for generating the integrated waveguide structures can also be alignment marks for later Use of the coupling elements with high accuracy in the coupling element produce. This allows a highly accurate adjustment of the coupling element opposite to the transmitter and receiver array.

The Coupling element can be with the most diverse Schnittstelen provided, for example, to other laminates of glass, ceramic, polymer or silicon, to electronic or optoelectronic components or into the environment (free-beam or fluidic).

Brief description of the drawings

The proposed micro-optical coupling element is described below of embodiments in conjunction with the drawings again explained in more detail. Hereby show:

1 a first example of an embodiment and arrangement of the proposed coupling element in a schematic representation in cross section;

2 a second example of an embodiment and arrangement of the proposed coupling element in a schematic representation in cross section;

3 a further example of an embodiment of the proposed coupling element in cross section;

4 a further example of an embodiment of the proposed coupling element in cross section;

5 a further example of an embodiment of the proposed coupling element in cross section;

6 a plan view of the two-dimensional lens array for beam collimation of a coupling element, as shown in the 3 to 5 is shown, and

7 another example of an embodiment of the proposed coupling element in cross section.

Ways to carry out the invention

1 shows a schematic representation in cross section of a first embodiment of a micro-optical coupling element according to the present invention. In this example, a single layer of thin glass, such as Schott D263T, was in the form of a glass sheet 2 used in the several passive optical waveguides 5 were integrated side by side by ion exchange in the molten salt, of which, due to the cross-sectional representation of the 1 only one waveguide is recognizable. The one end of the glass sheet 2 is cut off plan and for the coupling of several optical fibers 1 polished. The opposite end of the glass sheet 2 is cut at an angle of 45 °, as shown in the illustration of 1 can be seen, and in the field of integrated optical waveguides 5 provided with a mirror coating. This polished end surface with the mirroring forms the deflecting element 4 the illustrated coupling element. The deflected optical radiation exits via a second Ab cut the waveguide 5 from the coupling element. In the area of the exit surfaces are focusing lenses 6 in the glass foil 2 integrated. Also, this integration can be generated in a known manner on the technique of ion exchange in the glass sheet.

In the 1 is still an alignment mark 8th in the glass foil 2 indicated in the integration of waveguides 5 can be produced with high precision and allows the adjustment of the coupling element with respect to a transmitter and / or receiver array with high accuracy. In the figure is another layer 9 indicated that may be a single layer or a multiple layer. This additional layer sequence, for example of a different type of glass and with electrical, fluidic or other optical structures, can be provided by means of adhesive techniques or direct glass bonding as an additional layer under another glass sheet 2 to get integrated.

The principle of having a coupling element according to 1 essentially consists in that the divergent optical beams of a single or multi-line optical transmitter array, for example. A laser diode array or a waveguide array, using the micro-optical coupling element, possibly after a collimation by an integrated single or multi-line lens array (in 1 not shown) are coupled into a first portion of a single or multi-line waveguide array. In the example of 1 is the transmitter array through a fiber array with multiple optical fibers 1 educated. The receiver array is through a waveguide array in a semiconductor substrate 13 realized, however, can also be, for example, a single or multi-line photodetector array. The coupling into the waveguides realized in SOI (Silicon On Insulator) 12 takes place with a on the surface of the waveguide 12 trained vertical grating coupler 11 like this in the 1 is indicated schematically. The optical radiation coupled into the first section of the waveguide array of the optical coupling element 3 is at the deflecting element inclined in this example by 45 ° to the optical axis 4 , which acts as an optical reflector, reflected and continued in the second section of the waveguide array, which is inclined by 90 ° to the first waveguide section. The deflected radiation is then at the output of the coupling element via the vertical grating coupler 11 into the waveguides 12 of the semiconductor substrate 13 coupled. The coupled beam 14 is indicated in the figure.

By This arrangement arise in the region of the deflection waveguide crossings, the from the optical radiation on the way to the receiver Need to become. The optical paths are in this arrangement the same length, so that the signal propagation time in all channels is equal to.

to Achieving a high coupling efficiency must be the optical field distribution of the respective incident optical beam on the geometric be adjusted optical reception behavior of the receiver. This adaptation of the optical field distribution to the receiver takes place via the targeted influencing of the properties, in particular the refractive index distribution and the waveguide geometry, the first and second sections of the waveguide array of the coupling element in the manufacturing process. A crosstalk to the neighboring ones Channels is determined by the proper sizing of the refractive index distribution and the waveguide geometry of the first and second sections of the waveguide array prevented.

Possible variants or types of these sections of the waveguide array are continuous channel waveguides, periodically interrupted channel waveguides, lens waveguides and, for optical radiation with a Gaussian field distribution, also aperture waveguides. The 3 to 5 show different types of waveguides and waveguide intersections, as they can be used, for example, in the proposed coupling element. In these examples, the coupling element is in each case made up of four superimposed layers of thin glass or of superimposed glass foils 2 formed, in each case several waveguides 5 are integrated next to each other. This will be done via a transmitter array 19 several parallel optical beams 3 coupled into the coupling element.

3 shows an example of an embodiment in which the first and second waveguide sections of the coupling element are formed via waveguide intersections with continuous channel waveguides. 4 shows the same situation of orthogonal optical coupling over waveguide intersections with periodically discontinuous channel waveguides. 5 shows the orthogonal optical coupling via waveguide intersections with lens waveguides. A plan view of such a coupling element according to the 3 to 5 with the two-dimensional lens array 20 on the input surface of the coupling element, in the uppermost glass sheet 2 is integrated in the 6 to recognize. This two-dimensional lens array 20 The beam collimation is used by the transmitter array 19 emerging divergent light rays.

The coupling of the fibers 1 the transmitter array of the 1 can be done in a known manner by butt coupling. Of course, other coupling techniques are possible. Another possibility for the design of the coupling in the use of single or multi-line fiber arrays is in the DE 10 204 012 A described. In this case, the fibers ge via a fiber-joining process with a CO ₂ laser on the input surface or output surface of the coupling element welded. This process works like a wire-bond process, using instead of the wire the optical fibers, which can be made of glass or a polymer.

A tolerant coupling between the transmitter array and the coupling element is due to the collimation of the incident optical radiation reached. Sending and receiving characteristics must be identical be in order to achieve an optimal coupling. The optically collimated Beam must be in the transfer area of the transmitter array in the Coupling element the largest possible diameter have to allow a tolerant coupling. The collimation characteristic can be generated by diffractive and refractive optics, the are integrated in the coupling element.

2 shows another example of an embodiment and use of the proposed coupling element. In this example, the coupling elements are used to convert optical radiation into an electrical-optical circuit board fifteen or backplane at one point and decoupled at another point again. The case required support elements for the coupling elements are not shown in the figure. The coupling element can here in each case from one or more superposed glass sheets 2 are formed, are integrated in the respective waveguide structures. The other functional layers on the thin glass layer are not shown here. Furthermore, in this example in the transition region to the electrical-optical circuit board fifteen each focusing lenses 6 in one of the glass foils 2 integrated. The same reference numerals designate here the same components of the coupling element, as already in connection with 1 are described.

With this configuration, different optical beams can be 3 in different levels of the electrical-optical circuit board fifteen einkoppeln, or decouple from these levels, in each of which optical waveguides 16 , in this case multi-mode waveguide, are formed. This only requires the creation of corresponding insertion holes 18 in the surface of the electric-optical circuit board fifteen , This circuit board also has at least one layer in a known manner 17 for electrical circuits on, as in the 2 is indicated.

By the embodiment of the proposed coupling element with or several optical layers with integrated optically functional elements is a precise optical coupling between transmitter and Receiver array allows. The otherwise elaborate free adjustment of the coupling optics is achieved by their integration into the one or more optical layers of the coupling element and the Use of waveguides detached. Here are the Advantages of structuring techniques known from semiconductor technology used to the necessary for the optical coupling high To achieve precision. Furthermore, by the structure several optical layers also an optical interconnection of the individual integrated optically functional elements in three dimensions possible, which leads to an increase in the density of integration.

7 shows a further example of an embodiment of the proposed coupling element in cross section. In this example, two layers of thin glass were used 2 used one above the other to create a laser beam 3 via two lenses integrated in the upper layer 6 to focus and via a deflecting element 4 in the lower layer and a waveguide integrated therein 5 respectively. In addition, another layer is called metallization 21 applied to the top glass layer, which is the contacting of the laser chip 23 containing VCSELs and photodiodes, and a transceiver chip 24 about appropriate stud bumps 25 serves. The metallization 21 is structured suitable for this purpose. Furthermore, through in the upper glass layer 2 introduced via holes 26 , which are filled with electrically conductive material, such as gold, an electrical connection to the solder bumps 22 on the bottom. About these solder bumps 22 For example, an electrical connection can be produced between the semiconductor chips applied to the top side and the substrate, for example an electrical-optical circuit board, onto which the coupling element is placed. The via holes 26 For example, they can be introduced into the glass layer by laser drilling. The application of the metallization as well as the filling of the via holes 26 is done with techniques known in semiconductor manufacturing for the production of such electrical connections.

1

optical fiber

2

window film

3

optical beam

4

deflecting

5

optical waveguides

6

focusing lens

8th

alignment

9

Further Layer or layer sequence

11

vertical grating

12

waveguides in SOI

13

Semiconductor substrate

14

of coupled beam

15

electrical-optical circuit board

16

optical waveguides

17

location for electrical circuits

18

insertion

19

Transmitter array

20

Lens array

21

metallization

22

Solder bumps 22

23

Laser chip

24

Transmitter / receiver chip

25

Stud bumps

26

Via holes

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 7366380 B1 [0004]
• - DE 10204012 A [0034]

Cited non-patent literature

• - GT Reed et al., Silicon Photonics, Wiley, 2004, pp. 76-91 [0002]

Claims (10)

Microoptical coupling element with a main body into which one or more optical waveguides ( 5 ) for the guidance of optical radiation ( 3 ), which has entered the base body via one or more entry surfaces, and at least one deflection element ( 4 ) for the deflection of the optical radiation ( 3 ), wherein the base body is formed from at least one layer of thin glass and comprises one or more additional layers which have an electrical and / or fluidic function. Microoptical coupling element according to claim 1, wherein at one or more exit surfaces for the optical radiation ( 3 ) and / or at the entry surfaces one or more optical lenses, in particular focusing lenses ( 6 ), are integrated into the main body. Microoptical coupling element according to Claim 1 or 2, in which the optical waveguides ( 5 ) are formed by ion exchange from the molten salt in the body. Microoptical coupling element according to one of the claims 1 to 3, in which the optical lenses by means of ion exchange the molten salt are formed in the body. Microoptical coupling element according to one of Claims 1 to 4, in which the deflection element ( 4 ) is formed by an oblique and optionally mirrored end face of the layer of thin glass. Microoptical coupling element according to one of Claims 1 to 5, in which, in the thin-glass layer, several of the optical waveguides ( 5 ) are integrated side by side. Microoptical coupling element according to Claim 6, in which the optical waveguides ( 5 ) have a greater mutual distance at one end of the layer of thin glass than at another end of the layer of thin glass. Microoptical coupling element according to one of claims 1 to 7, wherein in the layer of thin glass two layers of optical waveguides ( 5 ) are integrated one above the other. Microoptical coupling element according to one of claims 1 to 8, wherein the base body is formed of a plurality of superimposed layers of thin glass, wherein in at least two of the layers, one or more of the optical waveguides ( 5 ) are integrated. Microoptical coupling element according to one of Claims 1 to 9, in which the optical waveguides ( 5 ) each having two separate waveguide sections, of which a first portion in a first direction between the entrance surface and the deflecting element ( 4 ) and a second section in a second direction between the deflecting element ( 4 ) and an exit surface of the optical radiation body.