PHOTONICALLY INTEGRATED CHIP, OPTICAL COMPONENT HAVING A PHOTONICALLY INTEGRATED CHIP, AND METHOD FOR THE PRODUCTION THEREOF

Abstract

The invention relates, inter alia, to a photonically integrated chip (2) having a substrate (20), a plurality of material layers arranged on a top side (21) of the substrate (20), an optical waveguide which is integrated in one or more wave-guiding material layers of the chip (2), and a grating coupler (60) which is formed in the optical waveguide and causes beam deflection of radiation guided in the waveguide in the direction out of the layer plane of the wave-guiding material layer(s) or causes beam deflection of radiation to be coupled into the waveguide in the direction into the layer plane of the wave-guiding material layer(s).

With respect to the chip, the invention provides for an optical diffraction and refraction structure (100, 100a) to be integrated in a material layer of the chip (2) above or below the optical grating coupler (60) or in a plurality of material layers above or below the optical grating coupler (60) or on the rear side of the substrate (20), which diffraction and refraction structure carries out beam shaping of the radiation before it is coupled into the waveguide or after it has been coupled out of the waveguide.

Claims

1. A photonically integrated chip (2) having a substrate (20), a plurality of material layers arranged on a top side (21) of the substrate (20), an optical waveguide which is integrated in one or more wave-guiding material layers of the chip (2), and a grating coupler (60) which is formed in the optical waveguide and causes beam deflection of radiation guided in the waveguide in the direction out of the layer plane of the wave-guiding material layer(s) or causes beam deflection of radiation to be coupled into the waveguide in the direction into the layer plane of the wave-guiding material layer(s), characterized in that an optical diffraction and refraction structure (100, 100a) is integrated in a material layer of the chip (2) above or below the optical grating coupler (60) or in a plurality of material layers above or below the optical grating coupler (60) or on the rear side of the substrate (20) and carries out beam shaping of the radiation before it is coupled into the waveguide or after it has been coupled out of the waveguide.

2. The photonically integrated chip (2) as claimed in claim 1, characterized in that the optical diffraction and refraction structure (100, 100a) forms a lens, a beam splitter or a polarization separator.

3. The photonically integrated chip (2) as claimed in claim 1, characterized in that the optical diffraction and refraction structure (100, 100a) is formed by steps in one or more material layers of the chip (2) above or below the optical grating coupler (60) or at least also comprises such steps.

4. The photonically integrated chip (2) as claimed in claim 1, characterized in that the waveguide is a ridge waveguide (50) which comprises a ridge formed in a wave-guiding material layer of the chip (2), and the optical diffraction and refraction structure (100, 100a) is integrated in one or more layers of the chip (2) above or below the ridge.

5. The photonically integrated chip (2) as claimed in claim 4, characterized in that the ridge waveguide (50) is formed in a silicon covering layer of an SOT material, and the optical diffraction and refraction structure (100, 100a) is integrated in one or more layers of the chip (2) above the silicon covering layer.

6. The photonically integrated chip (2) as claimed in claim 1, characterized in that the diffraction and refraction structure (100) is two-dimensional and is in a plane parallel to the wave-guiding material layer(s) (40), and the diffraction and refraction structure (100) is location-dependent in two dimensions, specifically dependent on the location in a dimension along the longitudinal direction of the waveguide and dependent on the location in a dimension perpendicular thereto, i.e. in a dimension perpendicular to the longitudinal direction of the waveguide.

7. The photonically integrated chip (2) as claimed in claim 1, characterized in that the diffraction and refraction structure (100) forms a two-dimensional Fresnel lens.

8. The photonically integrated chip (2) as claimed in claim 1, characterized in that the waveguide is an SOT ridge waveguide (50) having a ridge (51) which is formed in a wave-guiding silicon layer (40) of an SOT material on a silicon dioxide layer (30) and the longitudinal direction of which extends along the direction of propagation of the radiation guided in the SOT ridge waveguide, and the diffraction and refraction structure (100) is two-dimensional and is in a plane parallel to the wave-guiding silicon layer (40), the diffraction and refraction structure (100) being location-dependent in two dimensions, specifically dependent on the location in a dimension along the longitudinal direction of the ridge of the SOI waveguide and dependent on the location in a dimension perpendicular thereto, i.e in a dimension perpendicular to the longitudinal direction of the ridge of the SOI waveguide.

9. The photonically integrated chip (2) as claimed in claim 8, characterized in that webs (52, 53) are situated beside the ridge (51), the layer height of which webs is lower than that of the ridge (51).

10. The photonically integrated chip (2) as claimed in claim 8, characterized in that at least sections of the wave-guiding silicon layer (40) have been removed beside the ridge (51).

11. The photonically integrated chip (2) as claimed in claim 1, characterized in that the grating coupler (60) is a one-dimensional or two-dimensional grating coupler (60).

12. An element (1) having a photonically integrated chip (2) as claimed in claim 1.

13. The element (1) as claimed in claim 12, characterized in that the optical element (1) comprises a fiber, the fiber end of which is coupled to the optical diffraction and refraction structure (100, 100a) on that side of the latter which faces away from the grating coupler (60), the longitudinal direction of the fiber being oriented virtually perpendicularly to the wave-guiding layer(s) of the chip (2) in the region of the fiber end.

14. The element (1) as claimed in claim 12, characterized in that the optical element (1) comprises a radiation emitter which is coupled to the optical diffraction and refraction structure (100, 100a) on that side of the latter which faces away from the grating coupler (60), the radiation direction of the radiation emitter being oriented virtually perpendicularly to the wave-guiding layer(s) of the chip (2).

15. The element (1) as claimed in claim 12, characterized in that the optical element (1) comprises a radiation detector which is coupled to the optical diffraction and refraction structure (100, 100a) on that side of the latter which faces away from the grating coupler (60), the active reception surface of the radiation detector being oriented parallel to the wave-guiding layer(s) of the chip (2).

16. A method for producing a photonically integrated chip (2) which comprises a substrate (20) and a plurality of material layers applied to a top side (21) of the substrate (20), wherein, in the method, an optical waveguide is integrated in one or more wave-guiding material layers of the chip (2), and a grating coupler (60) is formed in the optical waveguide and causes beam deflection of radiation guided in the waveguide in the direction out of the layer plane of the wave-guiding material layer(s) or causes beam deflection of radiation to be coupled into the waveguide in the direction into the layer plane of the wave-guiding material layer(s), characterized in that an optical diffraction and refraction structure (100, 100a) is integrated in a material layer above or below the waveguide or in a plurality of material layers of the chip (2) above or below the waveguide or on the rear side of the substrate (20) and carries out beam shaping of the radiation before it is coupled into the grating coupler (60) or after it has been coupled out of the grating coupler (60).

17. The method as claimed in claim 16, characterized in that a lens, a beam splitter or a polarization separator is produced as the optical diffraction and refraction structure (100, 100a).

18. The method as claimed in claim 16, characterized in that the production of the optical diffraction and refraction structure (100, 100a) also at least comprises at least one lithography step and at least one etching step for etching steps in one or more material layers of the chip (2) above or below the optical grating coupler (60).

Description

[0040] The invention is explained in more detail below using exemplary embodiments; in this case, by way of example,

[0041] FIG. 1 shows an exemplary embodiment of an optical element which is equipped with a diffraction and refraction structure,

[0042] FIG. 2 shows an exemplary embodiment of a photonically integrated chip in which a diffraction and refraction structure forms a Fresnel lens,

[0043] FIG. 3 shows a plan view of the structure of the Fresnel lens according to FIG. 2,

[0044] FIG. 4 shows an exemplary embodiment of a photonically integrated chip in which a diffraction and refraction structure has multiple steps,

FIG. 5 shows another exemplary embodiment of a photonically integrated chip having a multi-step diffraction and refraction structure,

[0045] FIG. 6 shows an exemplary embodiment of an optical element in which a diffraction and refraction structure of a photonically integrated chip has a single step and forms a two-dimensional binary stepped lens,

[0046] FIG. 7 shows a plan view of the binary stepped lens according to FIG. 6,

[0047] FIG. 8 shows an exemplary embodiment of an SOI waveguide which is suitable for the optical elements according to FIGS. 1 and 6 and the photonically integrated chips according to FIGS. 2 and 4 to 5, specifically on the basis of the photonically integrated chip according to FIG. 2, for example, and

[0048] FIG. 9 shows another exemplary embodiment of an SOI waveguide which is suitable for the optical elements according to FIGS. 1 and 6 and the photonically integrated chips according to FIGS. 2 and 4 to 5, specifically on the basis of the photonically integrated chip according to FIG. 2, for example.

[0049] For the sake of clarity, the same reference symbols are always used for identical or comparable components in the figures.

[0050] FIG. 1 shows an exemplary embodiment of an optical element 1 which comprises a photonically integrated chip 2 or may be formed solely by such a chip. In the exemplary embodiment according to FIG. 1, it is assumed, for example, that the optical element 1 has, in addition to the chip 2, a radiation-emitting component 3, for example in the form of a laser or a radiation emitter.

[0051] The photonically integrated chip 2 comprises a substrate 20, on the top side 21 of which a plurality of material layers are arranged. A silicon dioxide layer 30, inter alia, is thus situated on the top side 21 of the substrate 20, on which silicon dioxide layer a wave-guiding silicon layer 40 is in turn arranged. The substrate 20, the silicon dioxide layer 30 and the wave-guiding silicon layer 40 may be formed by a so-called SOI (silicon on insulator) material which is commercially available in prefabricated form.

[0052] A ridge waveguide 50 is provided in the wave-guiding silicon layer 40 and can be formed, for example, by etching the wave-guiding silicon layer 40. A grating coupler 60 in the form of a Bragg grating is connected to the ridge waveguide 50 and has preferably likewise been produced by etching the wave-guiding silicon layer 40.

[0053] In the exemplary embodiment according to FIG. 1, further material layers, for example in the form of an intermediate layer 70 and an upper covering layer 80, are situated on the wave-guiding silicon layer 40.

[0054] A diffraction and refraction structure 100, which is not illustrated in any more detail in FIG. 1, is integrated in the covering layer 80. The diffraction and refraction structure 100 is preferably produced by means of one or more lithography steps and by means of one or more etching steps; exemplary embodiments of this are explained in yet more detail further below.

[0055] The optical element 1 according to FIG. 1 can be operated as follows, for example:

[0056] The radiation-emitting component 3 produces a divergent light beam Pe, the curved wave front 200 of which has a divergence α. The divergent light beam Pe strikes the diffraction and refraction structure 100 which, in the exemplary embodiment according to FIG. 1, is arranged in the covering layer 80 and therefore in the so-called “backend of line” region of the photonically integrated chip 2.

[0057] The diffraction and refraction structure 100 transforms the incident wave front 200 of the divergent light beam Pe into a planar wave front 201 which then strikes the grating coupler 60 and is coupled into the ridge waveguide 50 via said coupler. The light guided in the ridge waveguide 50 is identified using the reference symbol Pa in FIG. 1.

[0058] In summary, the diffraction and refraction structure 100 in the exemplary embodiment according to FIG. 1 is used to carry out beam shaping and to transform the curved wave front 200 into a planar wave front 201, thus improving the efficiency when coupling light into the grating coupler 60 or into the ridge waveguide 50.

[0059] FIG. 2 shows an exemplary embodiment of a diffraction and refraction structure 100, which can be used in the photonically integrated chip 2 of the element 1 according to FIG. 1, in more detail. It can be seen that the diffraction and refraction structure 100 in the exemplary embodiment according to FIG. 2 is formed by a single-step stepped profile which comprises etched sections 101 and unetched sections 102. The arrangement of the etched sections 101 and unetched sections 102 is selected in such a manner that the diffraction and refraction structure 100 forms a Fresnel lens 300.

[0060] The Fresnel lens 300 formed by the etched sections 101 and unetched sections 102 of the diffraction and refraction structure 100 is shown in more detail in a plan view in FIG. 3.

[0061] FIG. 4 shows another exemplary embodiment of a diffraction and refraction structure 100 which can be used in the photonically integrated chip 2 of the optical element 1 according to FIG. 1. The diffraction and refraction structure 100 is formed by a three-step stepped profile which has been formed in the upper or uppermost covering layer 80 of the chip 2 by means of lithography and etching steps. The step height and step arrangement of the steps is selected in such a manner that the beam shaping of the divergent light beam Pe is possibly favorable with regard to a wave front 201 which is as planar as possible and with regard to an optimum coupling efficiency with respect to the grating coupler 60 and the ridge waveguide 50.

[0062] FIG. 5 shows another exemplary embodiment of a diffraction and refraction structure 100 which can be used in the photonically integrated chip 2 of the optical element 1 according to FIG. 1.

[0063] In the exemplary embodiment according to FIG. 5, a multi-step lens profile has been produced in the upper covering layer 80 of the photonically integrated chip 2 by means of a multiplicity of lithography and etching steps, which lens profile may comprise thirteen steps, for example. The stepped profile or the outer shape of the lens is selected in such a manner that the coupling efficiency is possibly optimal in the direction of the grating coupler 60 and in the direction of the ridge waveguide 50.

[0064] FIG. 6 shows another exemplary embodiment of an optical element 1 which is equipped with a photonically integrated chip 2. In addition to the photonically integrated chip 2, the optical element 1 comprises a radiation-receiving component 4 which may be a radiation detector, for example.

[0065] The photonically integrated chip 2 has a substrate 20, a buried silicon dioxide layer 30, a wave-guiding silicon layer 40, an intermediate layer 70 and an upper covering layer 80 in which a diffraction and refraction structure 100a is provided. A ridge waveguide 50 and a grating coupler 60 are integrated in the wave-guiding silicon layer 40, preferably by means of etching.

[0066] The diffraction and refraction structure 100a in the covering layer 80 is formed by a single-step stepped profile or a binary step filter which comprises etched sections 101 and unetched sections 102.

[0067] The optical element 1 according to FIG. 6 can be operated as follows, for example:

[0068] A light beam Pe which is guided in the ridge waveguide 50 reaches the grating coupler 60 which couples out the light beam Pe and deflects it in the direction of the radiation-receiving component 4. The deflected beam preferably has a planar wave front 201.

[0069] The planar wave front 201 reaches the diffraction and refraction structure 100a which carries out beam shaping and converts the previously planar wave front 201 into a convergent wave front 203 with a divergence β. The resulting convergent light beam is identified using the reference symbol Pa in FIG. 6.

[0070] An exemplary embodiment of a diffraction and refraction structure 100a which can be used in the photonically integrated chip 2 according to FIG. 6 is illustrated in more detail, for example, in FIG. 7. FIG. 7 shows a diffraction and refraction structure 100a which can be produced using only one etching step and has etched sections 101 and unetched sections 102. The diffraction and refraction structure 100a forms a binary stepped lens 400.

[0071] FIG. 8 shows a cross section of an exemplary embodiment of an SOI waveguide in the form of an SOI ridge waveguide which is suitable for the optical elements according to FIGS. 1 and 6 and the photonically integrated chips according to FIGS. 2 and 4 to 5, specifically on the basis of the photonically integrated chip according to FIG. 2, for example.

[0072] The substrate 20, on the top side 21 of which a plurality of material layers are arranged, is seen in FIG. 8. The silicon dioxide layer 30, inter alia, is situated on the top side 21 of the substrate 20, on which silicon dioxide layer the wave-guiding silicon layer 40 is in turn arranged. The substrate 20, the silicon dioxide layer 30 and the wave-guiding silicon layer 40 are formed by an SOI (silicon on insulator) material.

[0073] A ridge waveguide 50 is provided in the wave-guiding silicon layer 40; the ridge width of the ridge 51 is identified using the reference symbol B in FIG. 8. Webs 52 and 53 are situated beside the ridge 51 and their web height or layer height is lower than that of the ridge 51. The direction of propagation of the light beam Pa according to FIG. 2 is perpendicular to the image plane in FIG. 8 and may be directed out of the image plane or into the image plane; in the exemplary embodiment according to FIG. 8, it is assumed, for example, that the light beam Pa is directed into the image plane.

[0074] Further material layers, for example in the form of the intermediate layer 70 and the upper covering layer 80, are situated on the wave-guiding silicon layer 40.

[0075] The diffraction and refraction structure 100 is integrated in the covering layer 80, is two-dimensional and carries out beam shaping in two axes, namely both along the arrow direction or along the direction of propagation of the light beam Pa according to FIGS. 2 and 8—that is to say along the longitudinal direction of the ridge waveguide 50—and perpendicular thereto, that is to say along the arrow direction Y in FIG. 8. As already mentioned, the diffraction and refraction structure 100 is preferably produced by means of one or more lithography steps and by means of one or more etching steps.

[0076] FIG. 8 also reveals that the diffraction and refraction structure 100 is formed, along the arrow direction Y, by a single-step stepped profile which comprises etched sections 101 and unetched sections 102.

[0077] The arrangement of the etched sections 101 and unetched sections 102 is selected, for example, in such a manner that the diffraction and refraction structure 100 forms a two-dimensional Fresnel lens 300 or a Fresnel lens 300 which operates in two axes. The Fresnel lens 300 formed by the etched sections 101 and unetched sections 102 of the diffraction and refraction structure 100 is shown in more detail in a plan view in FIG. 3.

[0078] It goes without saying that the diffraction and refraction structure 100 may also have multiple steps along the arrow direction Y, as has been explained in connection with FIGS. 4 and 5.

[0079] FIG. 9 shows a cross section of another exemplary embodiment of an SOI waveguide which is suitable for the optical elements according to FIGS. 1 and 6 and the photonically integrated chips according to FIGS. 2 and 4 to 5, specifically on the basis of the photonically integrated chip according to FIG. 2, for example.

[0080] The substrate 20, on the top side 21 of which a plurality of material layers are arranged, is seen in FIG. 9. The silicon dioxide layer 30, inter alia, is situated on the top side 21 of the substrate 20, on which silicon dioxide layer the wave-guiding silicon layer 40 is in turn arranged. The substrate 20, the silicon dioxide layer 30 and the wave-guiding silicon layer 40 form SOI (silicon on insulator) material.

[0081] A ridge waveguide 50 is provided in the wave-guiding silicon layer 40; the ridge width of the ridge 51 is identified using the reference symbol B in FIG. 9. The silicon has been completely removed in sections, for example has been etched away, beside the ridge 51, with the result that the webs 52 and 53 shown in FIG. 8 are missing. For the rest, the explanations above, in particular those in connection with FIG. 8, accordingly apply to the exemplary embodiment according to FIG. 9.

[0082] In summary, in the above exemplary embodiments, a lithographically produced optical diffraction and refraction structure 100 is introduced onto one or more upper material layers, preferably onto the uppermost material layer (covering layer 80), of the photonically integrated chip 2, that is to say the so-called “backend of line” region of the photonically integrated chip, for the purpose of subjecting light to beam shaping. For this purpose, step-like structures are preferably etched into the uppermost material layer or one or more upper material layers. Depending on the number of etching steps used, which may be limited by the number of available exposure masks for example, structures having one or more steps of graduated depth can be achieved. These structures function, as a whole, as a refractive and diffractive beam shaping element for a particular wavelength range by spatially varying the refractive index in a targeted manner. The etched and unetched regions have different refractive indices. The times of flight and directions of propagation of light waves through these different regions are therefore different, with the result that the wave front of the incident light wave is deformed after propagation through the diffraction and refraction structure. This effect can be used, for example, to collimate or even focus the light beam before it strikes the grating coupler 60 in the wave-guiding material layer in a deeper layer of the chip 2, the so-called “frontend of line” region of the chip. With a greater number of steps in the diffraction and refraction structure 100, the diffraction and refraction behavior of a perfect lens can be approximated. The diffraction and refraction structure 100 is preferably produced by means of a photolithographic exposure and etching process, which can also be combined with a plasma etching process, or else by means of ion beam etching. This process usually takes place at the end of the complete processing of the chip.

[0083] Although the invention was described and illustrated more specifically in detail by means of preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

LITERATURE

[0084] [1] Krishnamurthy, R., http://www.chipworks.com/en/technical-competitive-analysis/resources/blog/the-luxtera-cmos-integrated-photonic-chip-in-a-molex-cable/[2] [0085] [2] Mack, Michael; Peterson, Mark; Gloeckner, Steffen; Narasimha, Adithyaram; Koumans, Roger; Dobbelaere, Peter de, Method And System For A Light Source Assembly Supporting Direct Coupling To An Integrated Circuit, U.S. Pat. No. 8,772,704 B2, filed by Luxtera on May 14, 2013. application Ser. No. 13/894,052. Publication no.: U.S. Pat. No. 8,772,704 B2 [0086] [3] Anderson, Jon; Hiramoto, Kiyo, Oclaro, PSM4 Technology & Relative Cost Analysis Update. IEEE 802.3bm Task Force, Phoenix, Jan. 22-23, 2013.

LIST OF REFERENCE SYMBOLS

[0087] 1 Element [0088] 2 Chip [0089] 3 Component [0090] 4 Component [0091] 20 Substrate [0092] 21 Top side [0093] 30 Silicon dioxide layer [0094] 40 Silicon layer [0095] 50 Ridge waveguide [0096] 51 Ridge [0097] 52 Web [0098] 53 Web [0099] 60 Grating coupler [0100] 70 Intermediate layer [0101] 80 Covering layer [0102] 100 Diffraction and refraction structure [0103] 100a Diffraction and refraction structure [0104] 101 Etched sections [0105] 102 Unetched sections [0106] 200 Curved wave front [0107] 201 Planar wave front [0108] 203 Convergent wave front [0109] 300 Fresnel lens [0110] 400 Binary stepped lens [0111] B Ridge width [0112] Pa Light beam [0113] Pe Light beam