Optical interconnect having alignment depression

An optical interconnect includes a waveguide holder having a first side and a second side. The first side has a first depression and the second side has a second depression. The waveguide holder has an opening in which a plurality of waveguides are disposed.

FIELD OF THE INVENTION

The present invention relates generally to optical connectors, and particularly to an optical integrated circuit (OIC) that is connected to another OIC or to an optical fiber array.

BACKGROUND OF THE INVENTION

Optical integrated circuits include devices such as 1×N splitters, switches, wavelength division multiplexers and other like devices which may be deposited on a planar substrate, often referred to as a chip. The devices in the optical integrated circuit are often connected by waveguides. These waveguides are usefully planar waveguides that are fabricated on the surface of the chip. These planar waveguides are fabricated by a variety of techniques using various materials well known to one having ordinary skill in the art. The OIC is achieving more widespread use because it enables a more integrated and reliable structure for optical components. Moreover, the OIC is readily manufacturable with known manufacturing techniques.

The OIC is often connected to an optical fiber array for either short-haul or long-haul transmission via existing infrastructure. As such, it is useful to have an accurate interconnection between the OIC and the optical fiber array.

The accuracy of the interconnection depends greatly upon the alignment between the OIC and the optical fiber array at the interconnection point. As such, accurate optical connectors are used. Moreover, industry standards have resulted in the use of a variety of connectors.

There are basically two alignment techniques used to align the optical waveguides of the OIC to the optical fibers of a fiber array. One alignment technique is via active alignment, where the optical fibers are aligned to the planar waveguides while monitoring the optical transmission of the connection visually or by other active monitoring techniques. While active alignment enables a great deal of accuracy in the optical interconnection, it is a time consuming and labor intensive method. As such, it is not well suited for large-scale manufacturing.

Another alignment technique used to achieve alignment between waveguides of an OIC and an optical fiber array is passive alignment. Passive alignment comprises positioning the optical waveguides of the OIC relative to the optical fiber array without the labor intensive monitoring of the optical transmission of the connection. Passive alignment techniques have gained a great deal of popularity within the optical community because they afford a large-scale and low-cost technique for achieving the desired interconnection. Unfortunately, even though passive alignment techniques have the advantage of low-cost and large-scale manufacturing, the accuracy of the alignment may be less than acceptable.

Accordingly, what is needed is an interconnection structure for connecting waveguides in a passive manner which overcomes the drawbacks of the prior art described above.

SUMMARY OF THE INVENTION

According to an illustrative embodiment of the present invention, an optical interconnect includes a waveguide holder having a first side and a second side. The first side has a first depression and the second side has a second depression. The waveguide holding member further includes an opening in which a plurality of waveguides are disposed.

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation and not limitation, exemplary embodiments disclosing specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one having ordinary skill in the art having had the benefit of the present disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as to not obscure the description of the present invention.

Briefly, the present invention relates to an optical interconnect having a waveguide holder with a first side and a second side. The first side of the waveguide holder has a first depression and the second side of the waveguide holder has a second depression. A first guide pin is disposed in the first depression and a second guide pin is disposed in the second depression. The waveguide holder may be a single piece, or may comprise multiple pieces. The waveguide holder may be formed from materials conducive for use in optical applications.

The optical interconnection of the present invention enables accurate coupling of optical waveguides to other optical waveguides. To this end, the optical interconnect of the present invention enables accurate coupling of optical waveguides such as those typically used in OIC's to other optical waveguides such as those disposed in another OIC or in an optical fiber array. The optical interconnect of the present invention may be incorporated into standard optical connectors114, such as the MT, mini-MT, MAC or other optical connectors well known to one having ordinary skill in the art.

FIG. 1shows an optical interconnect100according to an illustrative embodiment of the present invention. The optical interconnect100further includes a substrate101and a lid102. Collectively, the substrate101and lid102may comprise an optical waveguide holder. An opening103in the lid102illustratively includes an optical waveguide structure104, which is disposed over the substrate. The optical waveguide104illustratively includes planar waveguides113, which may be part of an integrated optic chip. The substrate101has a first side105and a second side106. Similarly, the lid102has a first side107and a second side108. When the lid102is disposed over the substrate101, a first depression109and a second depression110are defined. A first guide pin111is disposed in the first depression and a second guide pin112is disposed in the second depression110. Illustratively, the lid102is adhered to the substrate101. This adhesion may be carried out by well-known techniques including by use of a suitable adhesive, such as epoxy or glass or by other techniques (e.g. wafer-wafer bonding) that are well known to one having ordinary skill in the art.

The first and second guide pins111and112, respectively, may be used to accurately couple the waveguides113to other optical waveguides such as optical fibers in an optical fiber array other optical waveguides such as waveguides of another integrated optic chip. To achieve efficient optical coupling between waveguides113and other waveguides such as optical fibers, the optical waveguides113must be accurately positioned relative to the first and second guide pins111and112, respectively. The present invention enables this accurate placement of the optical waveguides113relative to the guide pins111and112through passive alignment. To this end, first and second depressions109and110, respectively, are accurately located and oriented relative to the waveguides113. The accuracy of the passive alignment of the guide pins111and112relative to the optical waveguides113fosters accurate passive alignment of the optical interconnect100to other optical waveguides, such as an optical fiber array.

Illustratively, the substrate101and the lid102are monocrystalline material, such as monocrystalline silicon. The first and second depressions109and110, respectively, as well as opening103, may be fabricated anisotropic etching of the monocrystalline material. This anisotropic etching is typically a wet-etching which reveals the principle planes of the monocrystalline material. Anisotropic etching techniques are well known to one having ordinary skill in the art. Further details of such an illustrative etching technique may be found in U.S. Pat. No. 4,210,923 to North, et al., the disclosure of which is specifically incorporated by reference herein. Through the illustrative anisotropic etching, the dimensions and orientations of the etch may be precisely determined. This, of course, fosters the accuracy of the location and orientation of the first and second depressions109and110, and therefore, of the locations of the guide pins111and112, respectively.

FIG. 2shows an optical interconnect200according to another illustrative embodiment of the present invention. A substrate201has a lid202disposed thereover. Again, collectively, the substrate201and lid202may be referred to as a waveguide holder. An optical waveguide structure212includes optical waveguides203. The substrate201has a first side204and a second side205. The top silicon chip202has overhangs206and207. A first depression208is formed with the edge209of the first side of the substrate204and the overhang206of the lid202. A second depression210is created with edge211of the second side205of substrate204and the overhang207of the lid202.

The optical interconnect200is similar to the optical interconnect100shown in the illustrative embodiment of FIG.1. However, as can be seen inFIG. 2, the lid202is not etched, and accordingly there is not an opening for the optical waveguides203. As such, the lid202may rest on the waveguide structure212. Moreover, first and second depressions208and210are not substantially v-shaped as are those in the illustrative embodiment of FIG.1. Nonetheless, accurate location and orientation of edges209and211through anisotropic etching enables the accurate location and orientation of first and second depressions208and210. Accordingly, first and second depressions208and210enable accurate positioning of first and second guide pins213and214, respectively.

Thus, the accuracy of location of guide pins213and214fosters accurate passive alignment of the optical interconnect200to other waveguides, such as an optical fiber array or other optical waveguides. Again, the structure shown in the illustrative embodiment inFIG. 2may be incorporated for use into a standard optical connector215such as MT, mini MT or MAC connectors.

A particular advantage of the illustrative embodiment ofFIG. 2is that the lid202does not need to be accurately located on the substrate201. The lid can be a flat piece of material (without greeoves or sloped edges). The lid202can be made of materials such as silicon, glass, ceramic or quartz. The lid202can be adhered to the substrate with glue (e.g. epoxy), glass or other materials or techniques.

FIG. 3shows an optical interconnect300according to another illustrative embodiment of the present invention. The optical interconnect300illustratively includes a substrate301and a lid302disposed thereover. The substrate301and lid302collectively form a waveguide holder. The optical interconnect300is similar to the optical interconnect100of the illustrative embodiment of FIG.1. To this end, the optical interconnect300has an opening303and first and second depressions304and305, respectively. A first guide pin306is disposed in first depression304and a second guide pin307is dispose in second depression305. The first and second depressions304and305and openings303are features which are formed by substantially the same techniques described in connection with the illustrative embodiment of FIG.1. The optical interconnect300of the illustrative embodiment ofFIG. 3, includes alignment recesses308formed in the lid302and alignment recesses309formed in the substrate301.

Alignment recesses308and309are illustratively v-shaped notches or grooves formed in the lid302and substrate301. These shapes are merely exemplary, and the alignment recesses308and309may be inverted pyramidal, inverted trapezoidal or other shapes formed by known etching techniques. When the lid302is disposed over the substrate301as shown, the alignment recesses308and309form alignment features313. As can be readily appreciate, the alignment features313are cavities which may have a variety of shapes depending on the shape of the alignment recesses308and309. Alignment features313illustratively have positioning members311, such as a spherical or cylindrical element disposed therein. These positioning members are illustratively microspheres, rod elements or optical fiber sections. The positioning members311disposed in the alignment features313formed act as alignment fiducials which are accurately located. These alignment fiducials are used to accurately and passively locate the lid302over the substrate301. The alignment fiducials are particularly effective in assuring the accurate location of the waveguides312relative to first and second guide pins306and307, respectively.

FIG. 4shows an optical interconnect400according to another illustrative embodiment of the present invention. The optical interconnect400is substantially the same as the optical interconnect300shown in FIG.3. To this end, a substrate401has a lid402disposed thereover, which collectively forms a waveguide holder. First and second depressions404and405receive first and second guide pins406and407, respectively. Again, similar to the optical interconnect shown in the illustrative embodiment ofFIG. 3, alignment recesses408and409are disposed in the substrate401and lid402, respectively. Positioning members410are disposed in the alignment features413formed by alignment recesses408and409. Illustratively, alignment features413are accurately located and oriented by standard anisotropic etching techniques. As such, the positioning members410are useful in accurately locating the lid402over the substrate401. The opening411which receives the waveguides412therein is also accurately defined and oriented by anisotropic etching techniques. As can be appreciated, the waveguide structure412is significantly thinner than that of the illustratively embodiments previously described. Moreover, a residual cladding layer mask414remains disposed over the surface of the substrate as shown. The residual cladding layer414may be useful in accurately aligning the lid402over the substrate401.

FIG. 5shows an optical interconnect500according to another illustrative embodiment of the present invention. The optical interconnect500of the illustrative embodiment shown inFIG. 5has a substrate501and a lid502, which collectively form a waveguide holder. Similar to illustrative embodiments described above, first and second depressions503and504, respectively, have first and second guide pins505and506, respectively, disposed therein. Moreover, a waveguide structure507is disposed on a top surface of the substrate501. The lid502has an opening508formed therein. Alignment recesses509are formed in the lid502. Alignment recesses509may be formed by conventional etching techniques, to include wet etching techniques as well as dry etching techniques. These techniques include, but are not limited to anisotropic wet chemical etching as well as dry chemical etching techniques such as reactive ion etching (RIE). These techniques are well known in the art and further details are omitted in the interest of clarity of discussion. The alignment recesses509in the lid502may receive an alignment pedestal510.

The alignment pedestals510are illustratively formed on the top surface of the substrate501. The alignment pedestal510may in fact be a pedestal formed directly from the substrate501, or may be an etched feature such as an etched portion of the cladding material used in the fabrication of the waveguide structure507. The alignment pedestal510cooperatively engages the alignment recess509and enables the passive alignment of the lid502to the substrate501. This fosters the accurate location and orientation of recesses503and504, and thus, the accurate location and orientation of the first and second guide pins505and506. As described previously, the accurate alignment of the first and second guide pins505and506enables accurate alignment of the waveguide structure507of the optical interconnect500to other optical waveguides such as optical fibers in an optical fiber array or an integrated optical chip.

FIG. 6shows an optical interconnect600according to yet another illustrative embodiment of the present invention. Similar to the structures described above, the optical interconnect600includes a substrate601having a lid602disposed thereover. The substrate601and lid602collectively form a waveguide holder. First and second depressions603and604, respectively, receive first and second guide pins605and606, respectively. An optical waveguide structure607is disposed in an opening608in the lid602. The lid602may be disposed over metal pads609. These metal pads609may be raised metal features disposed over the silicon substrate. The metal pads609may be re-flow soldered by well-known techniques. This solder re-flow effects the bonding and, optionally, the alignment of the lid602to the substrate601. As described previously above, first and second guide pins605and606, respectively, are used to accurately align the waveguide structure607to other waveguides such as an optical fiber array or other waveguides previously described.

FIG. 7shows an optical interconnect700according to yet another illustrative embodiment of the present invention. The optical interconnect700includes a substrate701having a lid702disposed thereover, which collectively forms a waveguide holder. First and second depressions703and704, respectively, receive first and second guide pins705and706, respectively. Again, alignment of an optical waveguide structure707to other optical waveguides such as an optical fiber array is facilitated by the accurately located first and second guide pins705and706, respectively. An opening708is formed in the lid702for reception of an optical waveguide structure707. The substrate701has pedestal709over which wavguide structure707may be disposed. The pedestal709may be fabricated by standard etching techniques. Moreover, a complementary overhang710is formed in the lid702during fabrication of the opening708. This complementary overhang710is adapted to cooperatively engage the pyramid709for accurate alignment of the lid702to the substrate701. This cooperative engagement of the overhang710and pyramid709forms the first and second depressions703and704, respectively, accurately in both location and orientation. Thereby, first guide pin705and second guide pin706are accurately located and orientated, facilitating accurate optical interconnection schemes described more fully above.

FIG. 8shows an optical interconnect800, according to yet another illustrative embodiment of the present invention, having a substrate801and a lid802disposed thereover. The substrate801and lid802comprise a waveguide holder. A waveguide structure803is disposed in an opening804formed in the lid802. First and second depressions805and806, respectively, receive first and second guide pins807and808, respectively. The first and second guide pins807and808usefully enable accurate alignment of the waveguide structure803to other waveguides as described in further detail above. As can be readily appreciated, the substrate801has been etched by standard etching techniques into a shape which is complementary to the shape of the opening804. For purposes of illustration, the etching of the opening804and that of the substrate801may be done by standard anisotropic wet chemical etching. Protrusions809and810in the lid802cooperatively engage side surfaces811and812of the substrate801, respectively. This cooperative engagement results in the accurate location and orientation of first and second depressions805and806, respectively; this in turn achieves the accurate location and orientation of guide pins807and808.

FIG. 9shows an optical interconnect900according to yet another illustrative embodiment of the present invention. The optical interconnect900includes a substrate901having a lid902disposed thereover, which collectively form a waveguide holder. First and second depressions903and904, respectively, receive first and second guide pins905and906, respectively, in a manner described previously. Again, the accurate location and orientation of the first and second guide pins905and906by virtue of the accurate location and orientation of first and second depressions903and904enables the accurate alignment of waveguide structure907to other waveguides, such as an optical fiber array or other waveguides described previously. According to the illustrative embodiment ofFIG. 9, complementary alignment features are formed in the substrate901and the lid902. Illustratively, pedestals908are formed in the substrate901. Alignment recesses909formed in the lid902have shape and dimension to receive the pedestals908in a complementary fashion. Similarly, alignment recesses910are illustratively formed in the substrate901to receive pedestals911formed in the lid902. The alignment recesses909,910and pedestals908,911may be of a variety of complementary shapes which result from well-known etching techniques. These are illustratively grooves with complementary pedestals. They may take on a variety of other shapes such as pyramidal pedestals and pyramids.

The complementary alignment features of the substrate901and lid902of the optical interconnect900ofFIG. 9, enables the accurate location and orientation of first and second depressions903and904which ultimately result in the accurate alignment of the waveguide structure907to other optical waveguides described previously.

In the illustrative embodiments of the present invention described above, the lids and substrates can be batch-manufactured from wafers of material. The devices of the present invention can be batch-manufactured by bonding a lid wafer (comprising many lid chips) and a substrate wafer (comprising many substrate chips). In this way, alignment between lid and substrate can be provided for many devices simultaneously. Once the wafers are bonded, they can be cut into individual devices with a dicing saw, for example. Materials used for the lid and substrate can be silicon, glass, ceramics or the like. Bonding can be provided by wafer-wafer bonding. For example, borosilicate glass can be sputtered on the lid or substrate wafer (or both) and then the wafers can be heated and pressed together until bonding occurs. Preferably, the lid and substrate have similar coefficients of thermal expansion (e.g., equal to within about 5×10−6/degree Celsius).

Wafer-level assembly of the present devices is particularly useful in the embodiment shown in FIG.8. In the device ofFIG. 8, the lid can be difficult to locate on the substrate because it can tilt slightly (in a left-right direction). This problem is avoided by assembling (i.e. aligning and bonding) the lid and substrate while they are in wafer form. At the wafer-level, the lid and substrate cannot tilt.

The invention having been described in detail in connection through a discussion of exemplary embodiments, it is clear that various modifications of the invention will be apparent to one having ordinary skill in the art having had the benefit of the present disclosure. Such modifications and variations are included within the scope of the appended claims.