SUBSTRATES

BACKGROUND

Field

The present disclosure relates to optical communication equipment and, more specifically but not exclusively, to an optoelectronic circuit having one or more double-sided substrates. Description of the Related Art

This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

An optoelectronic device can operate on both light and electrical currents (voltages) and may include one or more of: (i) an electrically driven light source, such as a laser diode; (ii) an optical amplifier; (iii) an optical-to-electrical converter, such as a photodiode; and (iv) an optoelectronic component that can control the propagation and/or certain properties of light, such as an optical modulator or a switch. The corresponding optoelectronic circuit may additionally include one or more optical elements and/or one or more electronic components that enable the use of the circuit's optoelectronic devices in a manner consistent with the circuit's intended function.

Different hybrid-integration technologies can be used to combine various (such as the above-mentioned) components of an optoelectronic circuit into a practically useful integrated circuit, package, and/or assembly. While each of these technologies may offer significant respective benefits and or advantages in certain types of applications, hybrid integration continues to evolve by providing more-narrowly tailored solutions to specific segments of the market. For example, several product-specific factors typically need to be considered before the most appropriate integration method can be selected or developed. SUMMARY OF SOME SPECIFIC EMBODIMENTS

Disclosed herein are various embodiments of an optoelectronic circuit having a substantially planar double-sided substrate, each side of which has a respective plurality of electrically conducting tracks and a respective plurality of planar optical waveguides. The substrate may also have at least one via crossing the substrate in a manner that can be used to establish an optical path across the substrate, e.g., between optical waveguides located on different sides thereof. In an example embodiment, the electrically conducting tracks and planar optical waveguides are configured to operatively connect various optoelectronic devices and auxiliary electrical circuits attached to the two sides of the substrate using hybrid integration.

In some embodiments, two or more of such double-sided substrates can be stacked and optically and electrically interconnected to create an integrated three-dimensional assembly.

The disclosed optoelectronic circuits may advantageously have a higher density of optical/electrical components and shorter optical and electrical interconnections than typical functionally comparable conventional circuits. These and other pertinent characteristics of the disclosed optoelectronic circuits can beneficially be used, e.g., to reduce optical and/or electrical losses, decrease the form factor, and improve the functionality of the corresponding products.

According to one embodiment, provided is an apparatus comprising: a planar substrate having opposing first and second surfaces; a first planar optical waveguide located at the first surface; a second planar optical waveguide located at the second surface; a first optoelectronic device located at the first surface; and a second optoelectronic device located at the second surface; and wherein the planar substrate has a via crossing said substrate and configured to optically connect the first planar optical waveguide and the second planar optical waveguide.

According to another embodiment, provided is an apparatus comprising: a stack of two or more planar substrates, each having respective opposing first and second surfaces and a respective planar optical waveguide located at one of said first and second surfaces thereof; and wherein the respective planar optical waveguides of two of the two or more planar substrates are optically connected via a respective optical path that passes through at least one via crossing a respective substrate of the two or more planar substrates of the stack.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and benefits of various disclosed embodiments will become more fully apparent, by way of example, from the following detailed description and the accompanying drawings, in which: FIG. 1 shows a schematic side view of an optoelectronic circuit according to an embodiment;

FIG. 2 shows a schematic side view of a stack of planar lightwave circuits that can be used in the optoelectronic circuit of FIG. 1 according to an embodiment;

FIG. 3 shows a schematic side view of a stack of planar lightwave circuits according to an alternative embodiment; and

FIG. 4 shows a schematic side view of a planar lightwave circuit according to an alternative embodiment. DETAILED DESCRIPTION

FIG. 1 shows a schematic side view of an optoelectronic circuit 100 according to an embodiment. Optoelectronic circuit 100 comprises an electrical circuit 110, planar lightwave circuits (PLCs) 140 ₁ and 140 ₂ , and a heat sink 190. Circuits 110, 140 ₁ , and 140 ₁ and heat sink 190 are attached to one another, e.g., as indicated in FIG. 1, to form a mechanically robust stack, package, and/or assembly. A person of ordinary skill in the art will understand that, in an alternative embodiment, optoelectronic circuit 100 may include more than one electrical circuit that is similar to electrical circuit 110 and/or a different number of PLCs, each similar to a PLC 140.

Electrical circuit 110 and PLCs 140 ₁ and 140 ₂ are electrically interconnected as described in more detail below. Electrical circuit 110 is further electrically connected to one or more external electrical circuits and/or devices using a plurality of electrical leads (e.g., wires) 10 ₂ , only one of which is explicitly shown in FIG. 1 for illustration purposes. In an example embodiment, PLCs 140 ₁ and I40 ₂ are electrically connected to the external electrical circuits/devices through electrical circuit 110 and might not have any direct external electrical connections that bypass electrical circuit 110.

PLCs 140 ₁ and I40 ₂ are optically interconnected as described in more detail below. PLC 140 ₁ is further optically connected to one or more external optical and/or optoelectronic circuits/devices using one or more optical fibers 132, only one of which is explicitly shown in FIG. 1 for illustration purposes. In an example embodiment, PLC 140 ₂ is optically connected to the external optical and/or optoelectronic circuits/devices through PLC 140 ₁ and might not have any direct external optical connections that bypass PLC 140 ₁ . Heat sink 190 can be optional and generally operates to help maintain the temperatures of electrical circuit 110 and PLCs 140 ₁ and 140. within respective acceptable temperature ranges. In an example embodiment, heat sink 190 may be thermally coupled to electrical circuit 110 and PLCs 140 ₁ and 140 ₂ , e.g., as indicated in FIG. 1, using one or more thermally conducting couplers 188. Heat sink 190 may also include a microfluidic channel 192 and a plurality of fins 194 configured to facilitate heat dissipation and removal from optoelectronic circuit 100 as known in the pertinent art. In an alternative embodiment, an additional heat sink (not explicitly shown in FIG. 1) analogous to heat sink 190 can be placed next to electrical circuit 110.

In an example embodiment, electrical circuit 110 comprises a substantially planar substrate 106 whose lateral dimensions (e.g., length and width) are larger than its thickness do indicated in FIG. 1. The opposing surfaces of substrate 106 have patterned electrically conducting (e.g., metal) layers 104 and 108, respectively. Some conducting tracks of layers 104 and 108 are electrically connected to one another using a plurality of electrical vias 105. Layers 104 and 108 have conducting-track patterns (not explicitly shown in FIG. 1) that are configured to provide electrical connections between various portions of substrate 106 in a manner that enables proper operation of (i) various electronic integrated circuits (e.g., chips or dies) 112 directly attached and electrically connected to layer 104 and (ii) the PLCs 140 ₁ and 140 ₂ , which are electrically connected to layer 108.

For illustration purposes and without any implied limitations, substrate 106 is shown in FIG. 1 as having four electronic integrated circuits 112 ₁ -1124 attached to layer 104.

Although electronic integrated circuits 1121-112» are illustratively shown in FIG. 1 as being attached to layer 104 using ball grid arrays III1-III4, respectively, alternative surface-mount technologies can also be used in alternative embodiments. In an alternative embodiment, substrate 106 may have a different (from four) number of electronic integrated circuits 112 attached to layer 104. In various embodiments, electronic integrated circuits 112 may include, e.g., one or more of the following: (i) a digital signal processor; (ii) a memory; (iii) a microcontroller; (iv) an analog-to-digital converter; (v) a digital-to-analog converter; and (vi) a power converter. In some embodiments, substrate 106 may have additional electronic integrated circuits 112 directly attached to layer 108.

PLC 140 ₁ comprises a substantially planar (e.g., semiconductor) substrate 126 ₁ whose lateral dimensions (e.g., length and width) are larger than its thickness d ₁ indicated in FIG. 1. The opposing surfaces of substrate 126 ₁ have patterned electrically conducting (e.g., metal) layers 124 ₁ and 128 ₁ , respectively. Some conducting tracks of layers 124 ₁ and 128 ₁ are electrically connected to one another using a plurality of electrical vias 125. Layer 124 ₁ is further electrically connected to layer 108 of electrical circuit 110 using a plurality of solder balls 116. Layer 128 ₁ is further electrically connected to an electrically conducting layer 1242 of PLC 140 ₂ using a plurality of solder balls 156.

Substrate 126 ₁ also has planar waveguide layers 134 ₁ and 138 ₁ that are adjacent to the surfaces having electrically conducting layers 124 ₁ and 128 ₁ , respectively. Each of waveguide layers 134 ₁ and 138 ₁ is patterned to create a respective plurality of (e.g., ridge) waveguides configured to provide optical paths/connections between different portions of substrate 126 ₁ in a manner that enables proper operation of various optoelectronic devices 144 attached to that substrate. In various embodiments, optoelectronic devices 144 may include, e.g., one or more of the following: (i) a photodiode; (ii) an optical amplifier; (iii) an optical modulator; (iv) an optical switch; and (v) a laser diode. Each of optoelectronic devices 144 is electrically connected to one or both of electrically conducting layers 124 ₁ and 128 ₁ to receive and/or output the corresponding electrical signals used or generated by that optoelectronic device during its operation.

In an example embodiment, proper operation of optoelectronic devices 144 of PLC 140 ₁ is supported by auxiliary electrical circuits 148 that are fixedly attached and electrically connected to electrically conducting layers 124 ₁ and/or 128 ₁ . Each auxiliary electrical circuit 148 can be implemented using a conventional packaged electronic IC, a die, or a set of discrete electrical elements. For illustration purposes, PLC 140 ₁ is shown in FIG. 1 as having five auxiliary electrical circuits 148 (labeled 148 ₁ -148s). A person of ordinary skill in the art will understand that the number and type of optoelectronic devices 144 and the number and type of auxiliary electrical circuits 148 used in PLC 140 ₁ depend on the intended function and/or application of that PLC and may vary from embodiment to embodiment.

For example, optoelectronic device 144 ₁ may be a photodiode. Photodiode 144 ₁ is electrically connected to layer 124 ₁ by way of solder bumps 145. Photodiode 144 ₁ is optically coupled to a corresponding optical waveguide of layer 134 ₁ by way of a corresponding turning mirror 146. Mirror 146 has a slanted reflective surface that changes the propagation direction of the light received from the corresponding optical waveguide to cause the reflected light to impinge onto a photosensitive area of photodiode 144 ₁ . The electrical signal generated by photodiode 144. in response to the received light is then transferred, e.g., as indicated in FIG. 1, to a transimpedance amplifier 148 ₁ that is fixedly attached and electrically connected to electrically conducting layer 128 ₁ .

As another example, optoelectronic device 1442 may be an optical modulator.

Optical modulator 1442 modulates light in response to one or more electrical signals applied to it, e.g., as indicated in FIG. 1, by a driver circuit 1482 that is fixedly attached and electrically connected to electrically conducting layer 128 ₁ . Optical modulator 1442 is optically coupled to the corresponding optical waveguides of layer 134 ₁ using the corresponding ball lenses 150. More specifically, a first pair of ball lenses 150 is configured to couple light from a first optical waveguide of layer 134 ₁ into optical modulator 1442, where the received light may be phase- and/or amplitude-modulated. A second pair of ball lenses 150 then operates to couple the resulting modulated light into a second optical waveguide of layer 134 ₁ .

As yet another example, optoelectronic device 1443 may be a laser diode. Laser diode 1443 generates light in response to one or more electrical signals applied to it, e.g., as indicated in FIG. 1 , by a driver circuit 1484 that is fixedly attached and electrically connected to electrically conducting layer 128 ₁ . Laser diode 1443 is optically coupled to the corresponding optical waveguide of layer 134 ₁ using a corresponding pair of ball lenses 150. In the shown example, laser diode 1443 and the corresponding pair of ball lenses 150 are locally encapsulated using a suitable (e.g., polymeric) filler 162 and a retaining bracket or cap 164. In an alternative embodiment, local encapsulation can be implemented by bonding a window onto a seal ring over the circuit components that are being encapsulated.

PLC I40 ₂ is similar to PLC 140 ₁ , and the generally analogous elements of the two PLCs are labeled in FIG. 1 using the same numerical labels (with the exception of the subscripts). In an example embodiment, PLC 140 ₂ comprises a substantially planar substrate I262, patterned electrically conducting layers 1242 and I282, patterned planar waveguide layers 1342 and 1382, a respective plurality of electrical vias 125, a respective plurality of ball lenses 150, optoelectronic devices 1444-1447, and auxiliary electrical circuits 148 ₆ -148 ₁₁ . Substrate I262 has lateral dimensions that are larger than its thickness Ai indicated in FIG. 1. Optoelectronic devices 1444-1447 may include, e.g., one or more of the following: (i) a photodiode; (ii) an optical modulator; (iii) an optical amplifier; (iv) an optical switch; and (v) a laser diode. Auxiliary electrical circuits 148 ₆ -148 ₁₁ may include, e.g., one or more of the following: (i) an amplifier; (ii) a driver circuit; and (iii) a control circuit. Λ person of ordinary skill in the art will understand that the number and type of optoelectronic devices 144 and the number and type of auxiliary electrical circuits 148 used in PLC 140 ₂ depend on the intended function and/or application of that PLC and may vary from embodiment to embodiment.

As indicated in FIG. 1, PLCs 140 ₁ and 140 ₂ are arranged in a stack in which optical signals can be transferred between various waveguides of planar waveguide layers 134 ₁ , 1342, 138 ₁ , and 1382 by way of through-substrate vias 170. For illustration purposes and without any implied limitations, only three such vias (labeled 170 ₁ -1703) are shown in FIG. 1. More specifically, PLC 140 ₁ is shown as having the via 170 ₁ . PLC 140 ₂ is shown as having the vias 170 ₁ and 1703. In general, any desired number (that is feasible from the engineering viewpoint) of vias 170 can be incorporated into PLCs 140 ₁ and 140 ₂ to provide optical paths for optical-signal transfer between various waveguides of planar waveguide layers 134 ₁ , 1342, 138 ₁ , and 1382.

For example, the vias 170 ₁ and 170. are aligned with one another to create an optical path between an optical waveguide of planar waveguide layer 134 ₁ and an optical waveguide of planar waveguide layer 1382. Two slanted mirrors 146 inserted at the opposing ends of the vias 170 ₁ and 170. as indicated in FIG. 1 appropriately change the propagation direction of light from being substantially orthogonal to the main planes of PLCs 140 ₁ and I40 ₂ to being parallel to those planes, or vice versa. As a result, an optical signal can cross substrates 126 ₁ and 1262 by way of the optical path created by the vias 170 ₁ and 17(k and be coupled in and out of the corresponding optical waveguides of the planar waveguide layers 134 ₁ and 1382. In some embodiments, slanted mirror 146 can be augmented by an appropriate lens (see, e.g., FIG. 2).

The via 170s is configured to create an optical path between an optical waveguide of planar waveguide layer 1342 and an optical waveguide of planar waveguide layer 1382. Two slanted mirrors 146 inserted at the opposing ends of the via 1703 as indicated in FIG. 1 appropriately change the propagation direction of light from being substantially orthogonal to the main plane of PLCs 140 ₂ to being parallel to that plane, or vice versa. As a result, an optical signal can cross substrate H62 by way of the optical path created by the via I7O3 and be coupled in and out of the corresponding optical waveguides of the planar waveguide layers 1342 and 1382. As used herein, the term "via" refers to an opening (e.g., a hole or channel) that passes completely through the corresponding substrate (such as a wafer or die). The cross- sectional shape of the opening may or may not be uniform along the length of the via. The via can be filled, partially of completely, with one or more filler materials. A via can be designed and configured for providing an optical connection, an electrical connection, or both. For example, a via configured to provide an electrical connection is typically filled with metal, which is not optically transparent. In contrast, a via configured to provide an optical connection is typically unfilled or only partially filled and, as such, is optically transparent. In some embodiments, such a via may be filled with an optically transparent material, such as glass or silicon oxide.

In some embodiments, one or both of substrates 126 ₁ and 1202 may have embedded therein one or more passive electrical components, such as resistors, capacitors, and inductors, that are electrically connected to conducting tracks of one or both of the corresponding electrically conducting layers 124 and 128 using the corresponding electrical vias 125.

In some embodiments, one or both of substrates 126 ₁ and 1262 may have therein one or more microfluidic channels 182 for improved heat removal from PLCs 140 ₁ and 140 ₂ . For illustration purposes, substrate 1202 is shown in FIG. 1 as having four microfluidic channels 182 located in proximity to optoelectronic device 144«. A person of ordinary skill in the art will understand that, in an alternative embodiment, a different configuration of microfluidic channels 182 can similarly be used.

FIG. 2 shows a schematic side view of a stack 200 of PLCs that can be used in optoelectronic circuit 100 (FIG. 1) according to an embodiment. For illustration purposes, stack 200 is shown in FIG. 2 as including PLCs 140 ₁ -1403. For clarity of depiction, some of the constituent layers of PLCs 14O ₁ -1403 are not explicitly shown in FIG. 2. In an a alternative embodiment, stack 200 may have a different (from three) number of PLCs.

PLC 140 ₁ comprises an optical waveguide 238 ₁ that is a part of planar waveguide layer 138 ₁ (also see FIG. 1). PLC 140 ₂ comprises an optical waveguide 2382 that is a part of planar waveguide layer 1382 (also see FIG. 1). PLCs 140.-1403 have vias 270 ₁ -2703, respectively, that create an optical path that enables an optical signal 202 to be transferred, e.g., as indicated in FIG. 2, from optical waveguide 2382 of PLC 140 ₂ to optical waveguide 238 ₁ of PLC 140 ₁ . Each of the vias 270 ₁ -2703 provides an opening in the respective one of substrates I261-I263. The longitudinal axes of the vias 270 ₁ -2703 can be aligned (made collinear) with one another, e.g., as indicated in FIG. 2, using alignment grooves 204 and alignment balls 206. The via 270 ₂ has an optical prism 210. positioned therein in a manner that causes a facet 2122 of that optical prism to function as a turning mirror for the light that exits optical waveguide 2382. A lens 2142 attached to another facet of optical prism 2I0 ₂ is then used to collimate the light of optical signal 202 and direct a resulting collimated optical beam 220 through the via 270 ₂ of substrate I262 toward PLCs 1403 and 140 ₁ .

Optical beam 220 first passes through the via 2703, thereby crossing substrate 126a of PLCs I4O3 as indicated in FIG. 2. Optical beam 220 then impinges onto an optical prism 210 ₁ positioned in the via 270 ₁ of substrate 126 ₁ . A facet 212 ₁ of optical prism 210 ₁ operates as a turning mirror that causes the light of optical beam 220 to be directed toward optical waveguide 238 ₁ . A lens 214 ₁ attached to another facet of optical prism 210 ₁ is used to compress optical beam 220 for better coupling the light thereof into optical waveguide 238 ₁ . As a result, optical signal 202 can be transferred from optical waveguide 2382 of PLC 140. to optical waveguide 238 ₁ of PLC 140 ₁ with relatively low optical losses.

A person of ordinary skill in the art will understand that arrangements of turning mirrors and lenses similar to that shown in FIG. 2 can be used to create one or more additional optical paths for transferring optical signals between optical waveguides located in any pair of planar waveguide layers of PLCs 140 ₁ -14O3. For example, some of such optical paths can be used to transfer optical signals between the optical waveguides located in planar waveguide layers 134 and 138, respectively, of the same PLC 140 (see, e.g., the via 170a shown in FIG. 1). Some of such optical paths can be used to transfer optical signals between the optical waveguides located in respective planar waveguide layers of different PLCs 140 (see, e.g., the vias 170 ₁ and 170z shown in FIG. 1). In particular, vias, turning mirrors, and lenses can be arranged to create optical paths for transferring optical signals as follows: (i) between an optical waveguide located in planar waveguide layer 134 of one PLC 140 and an optical waveguide located in planar waveguide layer 134 of another PLC 140; (ii) between an optical waveguide located in planar waveguide layer 134 of one PLC 140 and an optical waveguide located in planar waveguide layer 138 of another PLC 140; and (iii) between an optical waveguide located in planar waveguide layer 138 of one PLC 140 and an optical waveguide located in planar waveguide layer 138 of another PLC 140. In some alternative embodiments, stack 200 may have more than three PLCs 140. In such embodiments, some of the optical paths for transferring optical signals between different PLCs 140 of stack 200 may cross more than one PLC 140 in a manner similar to that indicated in FIG. 2 for PLC 1403.

In some embodiments, some of the vias that provide optical connections can also be configured to additionally provide electrical connections. The via 2703 shown in FIG. 2 is an example of such a dual-function (optical/electrical) via. More specifically, side walls of the via 270 are coated with a film 272 of an electrically conducting material (e.g., a metal) in a manner that causes the film to connect electrically conducting layers 1243 and 1283 of PLC I4O3. At the same time, film 272 is relatively thin, which causes it to leave a sufficient unfilled opening in the middle portion of the via 2703 for optical beam 220 to pass through unimpeded, e.g., as indicated in FIG. 2.

FIG. 3 shows a schematic side view of a stack 300 of two PLCs 140 according to an alternative embodiment. For illustration purposes, stack 300 is shown in FIG. 3 as including PLCs 140 ₁ and 140 ₂ . For clarity of depiction, some of the constituent layers of PLCs 140 ₁ - I40 ₂ are not explicitly shown in FIG. 3.

Stack 300 is generally analogous to stack 200 shown in FIG. 2 and is constructed using many of the same structural and functional elements as stack 200. These elements are labeled in FIG. 3 using the same labels as in FIG. 2. The description of these elements is already provided above in reference to FIG. 2 and is not repeated here. However, stack 300 differs from stack 200 in that PLC 1403 is not present in stack 300. As a result, optical beam 220 in stack 300 crosses only one substrate, i.e., I262, by passing through the via 270 ₂ as indicated in FIG. 3.

FIG. 4 shows a schematic side view of PLC 140 ₂ according to an alternative embodiment. In the shown embodiment, PLC 140 ₂ is a stand-alone piece of equipment. For example, this particular embodiment can be made by one party (e.g., a part supplier) and then sold to another party (e.g., an assembly maker). The latter party can then use the supplied PLC I40 ₂ along with other pertinent parts to assemble an embodiment of optoelectronic circuit 100 (see FIG. 1).

According to an example embodiment disclosed above in reference to FIGs. 1-4, provided is an apparatus (e.g., 100, FIG. 1, or 140., FIG. 4) comprising: a substantially planar substrate (e.g., 1262, FIG. 1) having opposing first and second surfaces; a first planar optical waveguide (e.g., part of 1342, FIGs. 1 , 4) located at the first surface; a second planar optical waveguide (e.g., part of 1382, FIGs. 1, 4) located at the second surface; a first optoelectronic device (e.g., 144s, FIGs. 1, 4) located at the first surface; and a second optoelectronic device (e.g., 144*, FIGs. 1, 4) located at the second surface; and wherein the substantially planar substrate has a via (e.g., 1703, FIG. 1) crossing said substrate and configured to optically connect the first planar optical waveguide and the second planar optical waveguide.

In some embodiments of the above apparatus, the apparatus further comprises: a first electrical circuit (e.g., 148 ₆ , FIG. 1) located at the first surface; and a second electrical circuit (e.g., 148 ₁ o, FIG. 1) located at the second surface; and wherein the first and second electrical circuits are electrically connected to support operation of one or both of the first and second optoelectronic devices.

In some embodiments of any of the above apparatus, the first electrical circuit comprises a first electronic controller connected to control the first optoelectronic device; and the second electrical circuit comprises a second electronic controller connected to control the second optoelectronic device.

In some embodiments of any of the above apparatus, the first electrical circuit comprises an electronic controller connected to control the second optoelectronic device; and the substantially planar substrate has at least one electrical via (e.g., 125, FIG. 1) crossing said substrate and configured to electrically connect the first electrical circuit and the second optoelectronic device.

In some embodiments of any of the above apparatus, at least one of the first and second electrical circuits comprises one or more of the following: an electrical amplifier; a driver circuit; a control circuit; and a digital circuit.

In some embodiments of any of the above apparatus, the apparatus further comprises: a first ball grid array on the first surface that electrically connects the first electrical circuit to a plurality of conducting tracks (e.g., 1242, FIG. 1) on the first surface; and a second ball grid array on the second surface that electrically connects the second electrical circuit to a plurality of conducting tracks (e.g., 1282, FIG. 1) on the second surface.

In some embodiments of any of the above apparatus, at least one of the first and second optoelectronic devices comprises one or more of the following: a photodiode; an optical amplifier; an optical modulator; an optical switch; and a coherent light source. In some embodiments of any of the above apparatus, the apparatus further comprises a first turning mirror (e.g., 146, FIG. 1) located at a first end of the via and configured to direct light received from the first planar optical waveguide through the via in a direction substantially (e.g., within ±15 degrees) orthogonal to the substantially planar substrate.

In some embodiments of any of the above apparatus, the apparatus further comprises a second turning mirror (e.g., another 146 of 1703, FIG. 1) located at an opposite second end of the via and configured to couple light received from the first turning mirror into the second planar optical waveguide by directing said light in a direction substantially (e.g., within ±15 degrees) parallel to the substantially planar substrate.

In some embodiments of any of the above apparatus, the first optoelectronic device is optically coupled to the first planar optical waveguide; the second optoelectronic device is optically coupled to the second planar optical waveguide; and light transmitted between the first optoelectronic device and the second optoelectronic device passes through the via.

In some embodiments of any of the above apparatus, the substantially planar substrate has one or more microfiuidic channels (e.g., 182, FIG. 1).

In some embodiments of any of the above apparatus, the apparatus further comprises: at least one other optoelectronic device (e.g., 1444, FIG. 1) located at the first surface; and at least one other optoelectronic device (e.g., 1447, FIG. 1) located at the second surface.

In some embodiments of any of the above apparatus, the apparatus further comprises: at least one other electrical circuit (e.g., 1487, FIG. 1) located at the first surface; and at least one other electrical circuit (e.g., 148 ₁₁ , FIG. 1) located at the second surface; and wherein said other electrical circuits are electrically connected to support operation of one or both of said other optoelectronic devices.

According to another example embodiment disclosed above in reference to FIGs. 1-4, provided is an apparatus (e.g., 100, FIG. 1; 200, FIG. 2; or 300, FIG. 3) comprising: a stack (e.g., 200, FIG. 2; 300, FIG. 3) of two or more substantially planar substrates (e.g., 126 ₁ - I262, FIG. 3, or I261-I263, FIG. 2), each having respective opposing first and second surfaces and a respective planar optical waveguide (e.g., 238, FIG. 2) located at one of said first and second surfaces thereof; and wherein the respective planar optical waveguides of two of the two or more substantially planar substrates are optically connected via a respective optical path that passes through at least one via (e.g., 270, FIGs. 2-3) crossing a respective substrate of the two or more substantially planar substrates of the stack. In some embodiments of the above apparatus, the apparatus further comprises a first mirror (e.g., 2122, FIG. 2) configured to direct light between an end of one of the respective planar optical waveguides and the at least one via.

In some embodiments of any of the above apparatus, the apparatus further comprises a second mirror (e.g., 212 ₁ , FIG. 2) configured to direct light between the at least one via and an end of another one of the respective planar optical waveguides.

In some embodiments of any of the above apparatus, the at least one via has a metal film (e.g., 272, FIG. 2) on a wall thereof, the metal film electrically connecting the respective opposing first and second surfaces.

In some embodiments of any of the above apparatus, the stack includes: a first substantially planar substrate (e.g., 1262, FIG. 2) having a first planar optical waveguide (e.g., 2382, FIG. 2) located at a surface thereof and a first via (e.g., 270 ₂ , FIG. 2) crossing the first substantially planar substrate; and a second substantially planar substrate (e.g., 126 ₁ , FIG. 2) having a second planar optical waveguide (e.g., 238 ₁ , FIG. 2) located at a surface thereof; and wherein the first and second planar optical waveguides are optically connected via an optical path (e.g., for 220, FIG. 2) that passes through the first via.

In some embodiments of any of the above apparatus, the stack further includes a third substantially planar substrate (e.g., 1263, FIG. 2) having a second via (e.g., 2703, FIG. 2) crossing the third substantially planar substrate; and wherein the optical path further passes through the second via.

In some embodiments of any of the above apparatus, the stack includes: a first substantially planar substrate (e.g., 1262, FIG. 2) having a first planar optical waveguide (e.g., 2382, FIG. 2) located at a surface thereof; a second substantially planar substrate (e.g., 126 ₁ , FIG. 2) having a second planar optical waveguide (e.g., 238 ₁ , FIG. 2) located at a surface thereof; and a third substantially planar substrate (e.g., 1263, FIG. 2) located between the first and second substantially planar substrates in the stack, the third substantially planar substrate having an via (e.g., 2703, FIG. 2) crossing said third substantially planar substrate; and wherein the first and second planar optical waveguides are optically connected via an optical path (e.g., for 220, FIG. 2) that passes through the via.

While this disclosure includes references to illustrative embodiments, this specification is not intended to be construed in a limiting sense. Various modifications of the described embodiments, as well as other embodiments within the scope of the disclosure, which are apparent to persons skilled in the art to which the disclosure pertains are deemed to lie within the principle and scope of the disclosure, e.g., as expressed in the following claims.

Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word "about" or "approximately" preceded the value or range.

It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this disclosure may be made by those skilled in the art without departing from the scope of the disclosure, e.g., as expressed in the following claims.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the disclosure. Hie appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term "implementation."

Throughout the detailed description, the drawings, which are not to scale, are illustrative only and are used in order to explain, rather than limit the disclosure. The use of terms such as height, length, width, top, bottom, is strictly to facilitate the description of the embodiments and is not intended to limit the embodiments to a specific orientation. For example, height does not imply only a vertical rise limitation, but is used to identify one of the three dimensions of a three dimensional structure as shown in the figures. Such "height" would be vertical where the substrates are horizontal but would be horizontal where the substrates are vertical, and so on. Similarly, while all figures show the different layers as horizontal layers such orientation is for descriptive purpose only and not to be construed as a limitation.

Also for purposes of this description, the terms "couple," "coupling," "coupled," "connect," "connecting," or "connected" refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interposition of one or more additional elements is contemplated, although not required. Conversely, the terms "directly coupled," "directly connected," etc., imply the absence of such additional elements. The description and drawings merely illustrate the principles of the disclosure. It will thus be appreciated that those of ordinary skill in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass equivalents thereof.