WO2025000078A1

WO2025000078A1 - Photonic chip and probe alignment

Info

Publication number: WO2025000078A1
Application number: PCT/CA2024/050593
Authority: WO
Inventors: Alexander Tavit Knickle KURKJIAN; Nicholas Robert LEE-HONE
Original assignee: Photonic Inc
Current assignee: Photonic Inc
Priority date: 2023-06-29
Filing date: 2024-05-02
Publication date: 2025-01-02
Anticipated expiration: 2025-12-29

Abstract

For photonic integrated circuits with large numbers of ports, even small rotational errors with respect to a multi-port optical probe can be problematic in alignment for device testing. Multi-port optical devices and photonic integrated circuits can be aligned by scanning to determine relative locations of their optical ports. Based on relative positions of the optical ports, a relative rotation of a multi-port optical device with respect to a photonic integrated circuit is determined and the determined rotation applied. An additional translation can be provided as well.

Description

PHOTONIC CHIP AND PROBE ALIGNMENT

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from US application No. 63/511,151 filed 29 June 2023 and entitled PHOTONIC CHIP AND PROBE ALIGNMENT which is hereby incorporated herein by reference for all purposes. For purposes of the United States of America, this application claims the benefit under 35 U.S.C. §119 of US application No. 63/511,151 filed 29 June 2023 and entitled PHOTONIC CHIP AND PROBE ALIGNMENT which is hereby incorporated herein by reference for all purposes.

FIELD

The disclosure pertains to alignment of multi-port optical devices.

BACKGROUND

Optical signal delivery to and from photonic integrated circuits (PIC) and integrated photonic optical elements such as emitters, detectors, modulators, waveguides, beam splitters, interferometers, diffraction gratings defined on wafers, in modules, or dies (referred to collectively as “chips” for simplicity) is an important part of wafer-scale testing, automated module/die testing, and automated packaging. In these systems, the optical probe that delivers and recovers the signals cannot be permanently bonded to the input and output (CO) ports of the PIC as this would preclude rapid, non-destructive testing. On-chip CO ports can be used to couple between the integrated photonic optical elements and an optical probe used to transport the optical signals off-chip. To accurately characterize on-chip optical elements, the optical probe must be precisely aligned to the FO ports, both to provide efficient coupling and to accurately measure device properties which may be insertion-angle dependent. Conventional approaches to PIC/probe positioning tend to rely on design data and are subject to rotational and translational errors, particularly for PICs with large numbers of devices situated over large substrate areas. Optical ports of multi-port optical devices can have the same optical port spacing as available multi-port optical fibre probes, but mechanical tolerances can introduce rotational and positional shifts which preclude alignment of such a probe and an optical element using precise machining alone. In addition, the size of the probe end and the necessary proximity of the probe end to an optical device under test makes visual alignment methods impractical or impossible. Improved approaches are needed.

SUMMARY

This disclosure pertains to systems and methods for aligning integrated photonic devices having multiple optical ports to a multi-port optical device such that respective optical ports are satisfactorily aligned. Relative rotations that provide desired alignment are determined and then applied based on measurements of optical port locations or multi-port optical device design data. The approaches are suitable for surface coupling or edge coupling.

In some examples, alignment methods comprise optically coupling respective optical probe ports of a first multi-port optical device to optical ports of a second multi-port optical device and obtaining a plurality of optical port locations of at least one of the first multi-port optical device and the second multi-port optical device. Based on an optical port spacing of at least one of the first multi-port optical device and the second multi-port optical device and at least one of the plurality of optical port locations, a rotation is applied to least one of the first multi-port optical device and the second multi-port optical device to reduce misalignment.

In some examples, the apparatus comprises a multi-port optical probe that includes a plurality of probe ports and a positioning stage adaptable to receive at least one of the multiport optical probe and a photonic integrated circuit, wherein the positioning stage is operable to provide translation and rotation of the multi-port optical probe and the photonic integrated circuit with respect to each other. At least one beam source is situated to provide a probe beam to a first probe port of the plurality of probe ports of the multi-port optical probe and at least one detector is situated to receive a beam responsive to the probe beam from a second probe port of the plurality of multi-port optical probe ports. A processor system is coupled to the positioning stage and the at least one detector and operable to: a) translate the multi-port optical probe and the photonic integrated circuit with respect to each other to determine photonic integrated circuit port locations, b) determine a relative rotation to be applied to the multi-port optical probe and the photonic integrated circuit to reduce misalignment, and c) based on the determined photonic integrated circuit port locations and the relative rotation, operate the positioning stage to align the multi-port optical probe and the photonic integrated circuit.

The foregoing and other features and advantages of the technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system for alignment of photonic integrated circuits with respect to a multi-port optical probe arranged for edge coupling.

FIG. 1 A illustrates surface coupling to a photonic integrated circuit.

FIG. IB illustrates edge coupling to a photonic integrated circuit.

FIG. 2A illustrates a multi-port optical probe configured to couple optical sources and detectors to ports on a photonic integrated circuit using optical circulators.

FIG. 2B illustrates coupling of a source and a detector to a multi-port optical probe using a beam splitter.

FIG. 2C illustrates a multi-port optical probe that includes at least one detector and at least one emitter.

FIG. 3 A illustrates a misalignment of optical ports of a multi-port optical probe and a photonic integrated circuit.

FIG. 3B illustrates alignment of the optical ports shown in FIG. 3 A.

FIG. 4A illustrates a multi-port optical probe configured to optically couple to a photonic integrated circuit that includes optical devices having input optical ports distributed along two axes on a major surface of a photonic integrated circuit.

FIG. 4B illustrates a multi-port optical probe situated for optical coupling to the optical devices of FIG. 4A.

FIG. 4C is an end view of the multi-port optical probe of FIG. 4A.

FIGS 5A-5B illustrate a representative multi-port optical probe.

FIG. 6A illustrates a representative alignment method. FIG. 6B-6C illustrate the orientation of a multi-port optical probe and input optical ports of a photonic integrated circuit having four optical ports prior to alignment and after application of a relative rotation.

FIG. 7 illustrates a representative processor system operable to control the disclosed apparatus and implement the disclosed methods.

FIG. 8-9 illustrate additional representative alignment methods.

DETAILED DESCRIPTION Introduction and General Terminology

The disclosure pertains to methods and apparatus for coupling optical beams to and from multi-port optical devices such as photonic integrated circuits for evaluation and testing. As used herein, “port” or “optical port” refers to an input or output portion of an optical waveguide or optical device such as a source, detector, modulator, or other device. Multi-port optical devices can be defined on wafer-like substrates that include edge surfaces corresponding to substrate thickness and major surfaces that correspond to the larger nominally flat surfaces that are parallel to propagation directions of optical waveguides defined in the substrate. Optical ports can be arranged to couple optical beams into or out of these waveguides at substrate edges or at major surfaces of the substrates. For example, coupling via a major surface can be provided with a diffraction grating defined at the substrate or a prism situated at a major surface. Optical coupling at substrate edges can be provided by directing beams to or from polished, cleaved, or other optical transmissive edge surfaces. In some examples, to facilitate efficient coupling, a portion of a waveguide proximate to and terminating at a substrate edge is tapered from a larger cross-sectional area to a smaller cross- sectional area or vice versa to match waveguide mode size. Diffraction gratings and tapered waveguide portions are typical examples of optical ports but in some cases, coupling to untapered waveguides at substrate edges is sufficient. In other examples, multi-port optical devices comprise arrays of optical waveguides such as optical fibres that are fixed with respect to each other. Examples are described generally with reference to coupling of photonic integrated circuits and multi-port optical probes. However, the disclosed methods and apparatus are suitable for coupling optical beams to, from, and between arbitrary multi-port optical devices.

Photonic integrated circuits (PICs) generally include one or more optical waveguides defined in a plane at or near a major surface of a substrate. PICs can be fabricated using a wide variety of materials such as silicon-on-insulator (SOI), gallium-arsenide (GaAs), and indium phosphide (InP), and others. As an example, a PIC can be formed using a SOI approach that typically consists of a thin (about 100-500 nm) device layer of silicon on a thick (1-5 pm) buried oxide (BOX) layer of silicon dioxide which is in turn on a thick (50- 1,000 pm) layer (handle layer) of silicon. One or more optical sources, detectors, modulators, switches, splitters, and/or waveguides are provided by a PIC, and a PIC can be situated to be optically coupled to external optical sources, detectors, modulators, and/or waveguides as well. Optical devices that are part of a PIC are referred to as “integrated”.

As noted above, optical ports can be based on optical coupling via a major surface or an edge surface of a multi-port optical device. Integrated grating couplers redirect optical beams propagating out of a multi-port optical device plane into the device plane while edge couplers optically couple optical beams propagating in a device plane into the device. Efficient edge coupling can require alignment of propagation directions with respect to a device within 1, 2, 5, 10, or 20 degrees of the device plane. As used herein, efficient coupling refers to coupling with power losses of less than 0.5, 1.0, 1.5, or 2.0 dB. While optical ports based on edge coupling must be situated in the limited area provided by a substrate edges, grating couplers can be situated on the much larger areas provided by the major surfaces of PIC substrates. Such optical ports can be situated in regular arrays in a line or a two- dimensional array with a fixed or variable spacing between the optical ports. In addition, grating couplers can reduce the need for long optical waveguides and free up substrate areas for additional devices. In some examples, optical ports based on grating couplers have a total on-chip footprint on the order of 10-100 m x 10- 100 m. Grating couplers are described in greater detail in Marchetti et al., “High-efficiency grating-couplers: demonstration of a new design strategy,” Scientific Reports, doi.org/10.1038/s41598-017-16505-z (2017) which is incorporated herein by reference. Multi-port optical probes comprise a series of optical waveguides such as optical fibres that are fixed with respect to each other at one end to provide optical ports for optical communication with a device to be tested at first waveguide ends such as at cleaved or polished fibre ends. Second waveguide ends can be coupled to external detectors, sources, or modulators. The optical ports of a multi-port optical probe are typically arranged in a uniformly spaced linear array, but two-dimensional arrays and non-uniform spacings can be used. Such multi-port probes generally do not (but may) include active optical elements such as sources, detectors, modulator, switches but instead serve to couple optical beams to and from a photonic integrated circuit or other multi-port optical device. Such multi-port optical probes are commercially available through vendors such as Fibre Tech Optica (https://fibertech-optica.com/fiber-optic-probes/). These multi-port probes provide precise placement of the fibre ends relative to each other and may be secured by a ferrule that protects the fibres and allows optical ports to be near a major surface or an edge surface of a multi-port optical device, typically within 50 m. In most practical examples, optical port spacings of photonic integrated circuits and multi-port optical probes are selected to be the same and can include a few optical ports or many such as thousands of optical ports.

As used herein, “beam” or “optical beam” refers to propagating electromagnetic radiation at wavelengths between 200 nm and 10 pm. Beams can be guided or unguided and propagate in a bulk medium or in a waveguide. In some examples, such beams are collimated and have angular diameters of less than 1, 2, 5, 10, or 20 degrees. Typically, such beams are provided as laser beams for convenient, efficient coupling but either coherent, partially coherent, or incoherent beams can be used.

As used herein, positioning devices for one or both of rotational and translation motion are referred to as “positioning stages” or “stages.” Such stages can be based on combinations of positioning hardware that can be secured together. The examples are generally described with a positioning stage operable to adjust one of a photonic integrated circuit or a multi-port optical probe, but a stage or stages can be provided for translation and rotation of both.

As used in this application and in the claims, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly dictates otherwise. Additionally, the term “includes” means “comprises.” Further, the term “coupled” does not exclude the presence of intermediate elements between the coupled items unless otherwise indicated or required.

As used herein, “obtaining optical port locations” may include receiving, via an interface, spatial coordinates of the optical ports in a predefined coordinate system and determining the optical port locations based on said coordinates. In some embodiments, obtaining optical port locations may include scanning a multi-port optical device along one or more predefined axis to determine the optical port locations. In other embodiments, obtaining optical port locations may include obtaining an image of optical ports of a multi-port optical device and processing the image to determine the optical port locations.

The systems, apparatus, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and non- obvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The disclosed systems, methods, and apparatus are not limited to any specific aspect or feature or combinations thereof, nor do the disclosed systems, methods, and apparatus require that any one or more specific advantages be present or problems be solved. Any theories of operation are to facilitate explanation, but the disclosed systems, methods, and apparatus are not limited to such theories of operation.

Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed systems, methods, and apparatus can be used in conjunction with other systems, methods, and apparatus. Additionally, the description sometimes uses terms like “produce” and “provide” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms will vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art.

In some examples, values, procedures, or apparatus are referred to as “lowest”, “best”, “minimum,” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many functional alternatives can be made, and such selections need not be better, smaller, or otherwise preferable to other selections.

Examples are described with reference to directions indicated as “above,” “below,” “upper,” “lower,” and the like. These terms are used for convenient description, but do not imply any particular spatial orientation. Some examples are described with reference to particular coordinate systems for convenient illustration, but other coordinate systems can be used.

Example 1

With reference to FIG. 1, a system 100 for aligning a first multi-port optical device 102 with respect to a second multi-port optical device 104 includes a positioning stage 106 that is operable to translate and/or rotate the first multi-port optical device 102 with respect to the second multi-port optical device 104. In this example, the first multi-port optical device 102 is illustrated as a photonic integrated circuit (PIC) defined on a substrate 108 and including representative optical waveguides 110-114 that extend along major surface 116. The multi-port optical device 102 can include additional optical waveguides and other optical devices but these are omitted for convenient illustration. The waveguides 110-114 include respective end portions 120-124 that define optical ports as, for example, tapered waveguide sections and/or cleaved or polished waveguide ends.

The second multi-port optical device 104 includes a plurality of optical waveguides such as optical fibres (not shown) situated to couple optical beams to and from the first multiport optical device 102 as shown by arrows 128. The second multi-port optical device 104 receives one or more optical beams 125 from an optical circulator 130 that is coupled to an optical source such as a laser 132 that provides an optical beam 134 that is directed to the waveguide 111. The circulator 130 is also optically coupled to direct a beam from the waveguide 111 to a detector 136. Additional beams such as beams 140 can be directed to the second multi-port optical device 104 for delivery to the first multi-port optical device 102 but additional sources, detectors, and circulators are not shown.

Detectors such as the detector 136 are coupled to a processor system 141 that is operable to record detected signal magnitudes associated with signals received from the first multi-port optical device 102 in a storage device 142. The processor system 141 is also coupled to the positioning stage 106 and is operable to rotate and translate the first multi-port optical device 102 with respect to the second multi-port optical device 104 to provide satisfactory optical coupling. For a multi-port optical device that includes N optical waveguides to be coupled, the storage device 142 is coupled to the processor system 141 so that coordinates Xi, Zi and the associated detected signal magnitude li for i = 1, . . ..N are stored, wherein the coordinates are determined with respect to a coordinate system 148 in which a Z-axis is perpendicular to and into a plane of the figure. Based on the stored coordinates and detected signal magnitudes, the processor system 141 is operable to direct the positioning stage 106 to provide satisfactory coupling to the first multi-port optical device 102.

In FIG. 1, the first multi-port optical device 102 is coupled to the second multi-port optical device 104 using edge coupling as further illustrated in FIG. IB. Referring to FIG. IB, a portion of a multi-port optical device 170 includes a waveguide defined in device layer 172 that is situated on a BOX layer 174 defined on a substrate 176 such as a silicon substrate. An optical source 178 which could be associated with an additional multi-port device produces an optical beam 180 that is directed to the waveguide in the device layer 172 at an edge 182. In other examples, such as shown in FIG. 1A, a portion of a multi-port optical device 150 includes a waveguide defined in device layer 152 which is situated on a BOX layer 154 defined on a substrate 156 such as a silicon substrate. An optical source 158 produces an optical beam 160 that is directed to a grating coupler 162 defined in the device layer 152 to produce a beam in a waveguide 166. Multi-port optical devices can use either type of coupling, or a combination thereof. Optical sources can be provided as part of a multi-port device or a stand-alone device or in other ways.

Example 2

With reference to FIG. 2A, a system 200 for optically coupling a multi-port optical device 201 such as a multi-port optical probe for multi-port optical device testing includes sources 202, 204, 206, 208, 210 that produce respective optical beams 203, 205, 207, 209, 211 that are directed to respective circulators 222, 224, 226, 228, 230. The circulators are optically coupled via optical fibres 231 to the multi-port optical device 201 that includes corresponding portions 232, 234, 236, 238, 240 of the fibres 231 or other waveguides and fixed to a support 242. The multi-port optical device 201 is situated to couple beams from the sources 202, 204, 206, 208, 210 to a photonic integrated circuit or other multi-port optical device and to receive beams from the photonic integrated circuit or the other multi-port optical device as indicated by arrows 250. Corresponding received beams are directed by the multi-port device 201 to the circulators and then to a corresponding detector of a set of detectors 254.

Optical circulators such as shown in FIG. 2A or optical beamsplitters such as shown in FIG. 2B, or combinations thereof can be used for optical coupling. In FIG. 2B, a laser 280 is situated to direct an optical beam to a beamsplitter 282 which directs (in this example, reflects) a beam portion to a first multi-port optical device 284 such as a multi-port optical probe which then transmits and receives beams from a second multi-port optical device that is under test. Return beams are directed by the beamsplitter 282 (in this example, transmitted) to a detector 286. In some cases, the beamsplitter 282 directs only a portion of the beam from the laser 280 to the first multi-port optical device 284 and the remainder is transmitted to a detector 288 situated to receive the transmitted beam portion. The multi-port optical device 284 is generally situated for optical coupling of a plurality of waveguides to sources and detectors as shown in FIG. 1 and FIG. 2A, but these are not illustrated. Sources and detectors can be situated for reflection or transmission of the associated beams and dichroic or polarizing beamsplitters can be used. Other types of beamsplitters such as fibre couplers or plate beamsplitters can also be used. In this example, the multi-port optical device 284 is secured to a stage 290 for rotation and translation but in other examples, the photonic integrated circuit is secured to a stage.

In FIG. 2C, a multi-port optical device 291 includes waveguides 292-293 and 295-296 that define corresponding optical ports. In this example, the waveguides 293, 295 are coupled to an integrated laser diode 297 and an integrated detector 298, respectively. Such integrated active devices can be used along with external lasers, detectors, and beamsplitters such as the laser diode 280, the detectors 286, 288, and the beamsplitter 282 shown also in FIG. 2B. In this example, beams can be produced and detected on a multi-port optical device in addition to or instead of external devices. Multi-port optical devices (which can include photonic integrated circuits) may include integrated emitters and/or integrated detectors.

Example 3

Referring to FIG. 3 A, a multi-port optical probe 314 is illustrated as positioned proximate a photonic integrated circuit 304 but with significant misalignment. The photonic integrated circuit 304 includes optical ports 306, 308 and the multi-port optical probe 314 includes optical ports 316, 318. For purposes of illustration, edge coupling is illustrated, but similar misalignments can be addressed in coupling via a major surface. A relative rotation is apparent between the photonic integrated circuit 304 and the multi-port optical probe 314. In a coordinate system 350 having a Y-axis parallel to an axis on which the optical ports 306, 308 are situated, the optical ports 316, 318 have an X-offset of AX and a Y-axis offset of AY corresponding to a relative rotation angle of arctan[AX/AY] about an axis into a plane of the drawing (a Z-axis of the coordinate system 350). After applying a corresponding relative rotation, alignment of the optical ports is as shown in FIG. 3B. In some cases, a suitably precise rotation can be applied as determined from AX/AY using a suitable positioning stage, and a single rotation can suffice. In other cases, an approximate rotation is applied, and remeasurement of optical port locations is needed to determine an additional rotation and multiple rotation steps can be necessary. As shown, the optical ports have different spacings and the optical ports are not completely aligned. Optical port spacings can vary as designed or due to manufacturing tolerances. As will be appreciated, applying each corresponding rotation reduces misalignment between the photonic integrated circuit 304 and the multi-port optical probe 314.

Relative locations of optical ports 306, 308 with respect to optical ports 316, 318 can be determined by translations of one or both of the multi-port optical probe 314 and the photonic integrated circuit 304 to produce relative coordinates (XI, Yl) and (X2, Y2), respectively, which can be used to determine AX as X1-X2 and AY as Y1-Y2. In examples with more than two ports, a rotation to be applied can be based on selected relative optical port location of two or more optical ports, or all relative port locations can be used to determine a rotation that is suitable for all optical ports but generally different from a rotation selected using two optical port locations. For optical ports having nominally the same spacing, relative port locations of two optical ports can be sufficient although it is generally preferred to use multiple optical port locations and determine an overall rotation that provides satisfactory performance for all optical ports.

Example 4

FIGS. 4A-4C illustrate coupling of a photonic integrated circuit 400 to a multi-port optical probe 440. The multi-port optical probe 440 includes optical ports 432-436 defined by cleaved or polished faces of corresponding optical fibres that are fixed to a probe substrate 438. In FIG. 4C, the optical ports 432-436 of the multi-port optical probe 440 face a Z-axis of a coordinate system 450 that defines X, Y, and Z coordinate axes. However, the optical ports 432-436 need not be aligned to be perpendicular to a probe surface 440A. For coupling of the optical ports 432-436, the multi-port optical probe 440 is rotated about an axis 441 so that optical beams delivered from the optical ports 432-436 are incident to the photonic integrated circuit 400 at a suitable angle for surface coupling to devices defined by, for example, grating couplers defined on the photonic integrated circuit 400. As shown, optical port spacing of the multi-port optical probe 440 is uniform and corresponds (at least nominally) to optical port spacing on the photonic integrated circuit 400. Non-uniform spacings can be used, and optical ports can be arranged in two dimensions on the multi-port optical probe 440 such as in a regular array.

Referring to FIG. 4A, the photonic integrated circuit 400 includes integrated optical devices 402-404 and 412-414 having optical ports 402A, 403A-403B, 404A-404B and 412A- 412B, 413A, 414A, respectively. In FIG. 4A, these optical ports are illustrated with triangles but are generally implemented as grating couplers. The optical ports 402A, 403A-403B, 404A-404B and 412A-412B, 413A, 414A are coupled to respective device regions 402C, 403D, 404D and 412D, 413C, 414C by waveguides 402B, 403 C, 403E, 404C and 412C, 413B, 414B. In this example, the optical ports 402A, 403A-403B, 404A-404B are situated along an axis 480 and the optical ports 412-A-412B, 413A, 414A are situated on an axis 481, but optical ports can be situated anywhere on a major surface 484 of the photonic integrated circuit 400. FIG. 4B is a sectional view of the photonic integrated circuit 400 and the multi-port optical probe 440 (noted as 440-1) situated for optical coupling to optical ports of the photonic integrated circuit 400 situated on the axis 480 for beam propagation between the multi-port optical probe 440 and the photonic integrated circuit 400 along an axis that is an angle 01 from the major surface 484. In addition, the multi-port optical probe 440 (noted as 440-2) is shown as situated for optical coupling to optical ports of the photonic integrated circuit 400 situated on the axis 481 for beam propagation between the multi-port optical probe 440 and the photonic integrated circuit 400 along an axis that is an angle 02 from the major surface 484. In typical examples, these angles are dependent on grating coupler design and are the same. The angles can also be dependent on optical fiber polish and cleave angles. The photonic integrated circuit 400 is defined on a substrate 486 and contacts a stage 490 that provides rotations and translations that are operable to determine relative positions of optical ports and apply rotations and translations for alignment. It can be convenient to rotate one or both of the photonic integrated circuit 400 and the multi-port optical port 440 about an axis 490 or other axis that is parallel to the Z-axis for alignment, but other axes can be used that provide a rotational component about the Z-axis. The multi-port optical probe 440 can be secured to a positioning stage to provide rotations and translations as well but such a positioning stage is not shown in FIG. 4B.

Example 5

Referring to FIG. 5A, a representative multi-port optical probe 500 that includes a support member comprising a top element 510 and a bottom element 512 that secure a plurality of optical waveguides that terminate at a probe surface 520. As shown, the multi-port optical probe 500 includes optical ports 502-505 defined by corresponding optical fibres and are secured between the top element 510 and the bottom element 512 in respective support members 514A, 514B that can be, for example, an adhesive and a grooved substrate having a plurality of grooves that align the optical fibres. FIG. 5B illustrates a representative implementation of such a probe in which the optical ports 502-505 are aligned along an axis and are separated by distances dl, d2, d3 which can be the same or different. An adhesive layer (not shown) can be used to secure the associated optical fibres to a groove 550 which is used to align the optical ports 502-505.

Example 6

Referring to FIG. 6A, a representative method 600 includes determining if relative positions of probe ports and photonic integrated circuit ports are available at 602. For example, the relative positions may be made available via an interface. If not available, at 604, one or both of a multi-port optical probe and a photonic integrated circuit are scanned to determine relative optical port locations based on, for example, centers of optical ports. In scanning, beams are injected into one or more optical ports and received from one or more ports of a multi-port optical probe and a photonic integrated circuit so that location determination is based on optical properties and not design or fabrication geometries. With relative positions of optical ports available, a rotation correction is estimated at 606 and applied at 608 by rotating one or both of the multi-port optical probe or the photonic integrated circuit. At 610, translation corrections are determined for application at 612. In some situations, particularly when application of a precise rotational correction is difficult, the desirability of additional corrections is determined at 614. For example, an applied correction may be approximate and one or more additional corrections may be necessary to complete alignment. If additional corrections are to be determined, scanning is implemented again at 604. Otherwise, alignment is complete.

FIGS. 6B-6C illustrate determination of a relative rotation to be applied to align optical ports of a photonic integrated circuit 620 with optical ports of a multi-port optical probe 630 and application of the relative rotation. In this example, one or both of the photonic integrated circuit 620 and the multi-port optical probe are scanned to determine relative displacements of probe ports 622, 632 and 625, 635 to produce relative coordinates (XI, Yl) and (X2, Y2), respectively. A relative rotation angle is then given by 0 = arctan[AX/AY] and a corresponding opposite rotation can be applied for alignment. One or both the photonic integrated circuit 620 and the multi-port optical probe 630 can be rotated. After rotation, the ports can remain offset, and translation such as illustrated at 640 can be applied based on previously determined relative coordinates compensated based on the applied rotation, or the optical ports can be scanned again, and updated coordinates obtained to use to determine translation. As noted above, in some cases, two or more rotations are required for alignment and rotations can be applied based on updated coordinates. For fixed port spacings, rotations may be satisfactorily obtained based on displacement values AY from probe or photonic integrated circuit design values.

Additional optical ports of the probe 630 such as ports 633, 634 and the photonic integrated circuit 620 such as ports 623, 624 can be scanned and used for both rotational and translational alignment.

Example 7

FIG. 7 and the following discussion are intended to provide a brief, general description of an exemplary computing environment in which the disclosed technology may be implemented. Although not required, the disclosed technology is described in the general context of computer-executable instructions, such as program modules, being executed by a personal computer (PC). Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Moreover, the disclosed technology may be implemented with other computer system configurations, including hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, and the like as well as with FPGAs, ASICs, Complex Programmable Logic Devices (CPLDs), or other dedicated processors. The disclosed technology may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. As used herein, storage and storage devices refer to physical devices and not transitory storage or signals.

With reference to FIG. 7, an exemplary system for implementing the disclosed technology includes a general-purpose computing device in the form of an exemplary conventional PC 700, including one or more processing units 702, a system memory 704, and a system bus 706 that couples various system components including the system memory 704 to the one or more processing units 702. The system bus 706 may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The exemplary system memory 704 can include read only memory (ROM) and random-access memory (RAM) and a basic input/output system (BIOS) containing the basic routines that help with the transfer of information between elements within the PC 700, can be stored in ROM. The memory 704 also contains portions 771-773 that include computer-executable instructions and data for multi-port optical probe/photonic integrated circuit scanning, translational offset calculations, and rotational offset calculations, respectively, as well as a portion 777 that stores port locations and relative coordinates.

The exemplary PC 700 further includes one or more storage devices 730 such as a hard disk drive for reading from and writing to a hard disk, a magnetic disk drive for reading from or writing to a removable magnetic disk, and an optical disk drive for reading from or writing to a removable optical disk (such as a CD-ROM or other optical media). Such storage devices can be connected to the system bus 706 by a hard disk drive interface, a magnetic disk drive interface, and an optical drive interface, respectively. The drives and their associated computer-readable media provide nonvolatile storage of computer-readable instructions, data structures, program modules, and other data for the PC 700. Other types of computer-readable media which can store data that is accessible by a PC, such as magnetic cassettes, flash memory cards, digital video disks, CDs, DVDs, RAMs, ROMs, and the like, may also be used in the exemplary operating environment.

A number of program modules may be stored in the storage devices 730 including an operating system, one or more application programs, other program modules, and program data. For example, port location data can be stored in a storage device. A user may enter commands and information into the PC 700 through one or more input devices 740 such as a keyboard and a pointing device such as a mouse. Other input devices may include a digital camera, microphonejoystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the one or more processing units 702 through a serial port interface that is coupled to the system bus 706 but may be connected by other interfaces such as a parallel port, game port, or universal serial bus (USB). A monitor 746 or other type of display device is also connected to the system bus 706 via an interface, such as a video adapter. Other output devices 748 such as speakers and printers, may be included.

The PC 700 may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer 760. In some examples, one or more network or communication connections 750 are included for wired or wireless communication as well as data acquisition and control such as digital-to-analog convertors and analog-to- digital convertors. The remote computer 760 may be another PC, a server, a router, a network PC, or a peer device or other common network node, and typically includes many or all of the elements described above relative to the PC 700, although only a memory storage device 762 has been illustrated in FIG. 7. The personal computer 700 and/or the remote computer 760 can be connected to a local area network (LAN) and a wide area network (WAN). Such networking environments are commonplace in offices, enterprise- wide computer networks, intranets, and the Internet.

When used in a LAN networking environment, the PC 700 is connected to the LAN through a network interface. When used in a WAN networking environment, the PC 700 typically includes a modem or other means for establishing communications over the WAN, such as the Internet. In a networked environment, program modules depicted relative to the personal computer 700, or portions thereof, may be stored in the remote memory storage device or other locations on the LAN or WAN. The network connections shown are exemplary, and other means of establishing a communications link between the computers may be used.

Example 8

With reference to FIG. 8, a representative method 800 includes securing a photonic integrated circuit and a multi-port optical probe with respect to each other at 802 for relative scanning using one or more positional stages that can provide translations and rotations. Nominal spacings of photonic integrated circuit optical ports and multi-port optical probe ports can be provided at 804, and at 806 a particular waveguide device and corresponding probe port are selected for measurement. At 808, one or both of the photonic integrated circuit and the multi-port optical probe are scanned to establish relative optical port position and at 810, it is determined if other optical probe ports are to be scanned. If so, a particular port combination is selected at 806 and scanning is repeated. If no additional scanning is requested, at 812 rotation correction is calculated and applied and at 814, a translation is applied to further align optical ports. In FIG. 8, optical ports are scanned serially, but in some examples, beams associated with two or more (or all ports) are provided, and relative locations can be determined in a single scanning operation.

Example 9

Referring to FIG. 9, a representative method 900 of applying a relative rotation between first and second multi-port optical devices (such as a photonic integrated circuit and a multi-port optical probe) comprises determining a rotation to be applied at 902. If this rotation is to be applied with a positioning stage that provides feedback or readout of applied rotations, the determined rotation is applied at 906, typically completing rotational alignment. For other types of positioning stages with which application of precise rotations is difficult, one or both of the multi-port optical devices are rotated by a selected amount at 908 and rotational alignment is tested at 910. If additional rotation is necessary, a rotation is again applied at 908. Upon successful completion of rotational alignment, translation alignment can be performed as discussed above.

Additional Examples

The disclosed methods and apparatus are not limited to any particular configuration of optical elements on a photonic integrated circuit (PIC); however, the configuration of optical elements may be optimised to facilitate alignment method. In particular, the geometry of the multi-port optical probe, and configuration of signal injection ports and signal collection ports on the multi-port optical probe intended for alignment of the multi-port optical probe with a PIC may be taken into account when configuring the types of optical elements and their layout on the PIC.

For example, optical elements on a PIC may be (but are not limited to) single-port optical elements, where the PIC input and output coupler for the optical elements are not unique and the optical elements are addressed simultaneously by the same port on the multiport optical probe. The signal monitored for the alignment method from such optical element may be dependent on a signal injected by a multi-port optical probe or may be provided by an emitter that is a part of the PIC. Two-port transmissive optical elements for which the input and output coupler on the PIC are unique and may be spatially separated by hundreds of microns and are addressed by different ports on the multi-port optical probe.

Multi-port transmissive optical elements can have one or more distinct input couplers and/or one or multiple distinct output couplers on the PIC that are addressable by different optical ports on the multi-port optical probe. There are multiple options to monitor signal for alignment method, including but not limited to a) one injected signal incident on one PIC input port, directed to multiple PIC output couplers by an integrated optical splitter (or combiner) a rapidly modulatable integrated optical switch, or a wavelength division multiplexing splitter; b) multiple injected signals incident on multiple PIC input ports, directed to a single PIC output port by integrated optical splitter (or combiner), a rapidly modulatable integrated optical switch, or a wavelength division multiplexing combiner; and c) combinations of these listed types of optical elements;

In an exemplary embodiment, a PIC may have a combination of optical elements devices such that the topmost two optical elements are single-port reflective optical elements comprising grating coupler-waveguide-cavity, while the third optical device is a transmissive optical element comprising a grating coupler-waveguide-grating coupler. It is important that the length of the third device does not include a cavity and that the length of the waveguide is equal to the separation between adjacent ports on the multi-port device. A benefit to using a PIC with this configuration of optical elements is that the signal characterized from these elements can be used as a baseline for evaluating the state of the measurement system and PIC fabrication by evaluating optical element performance after alignment. Configuration of the devices on a PIC may further facilitate use of some optical elements (e.g., those situated at comers or edges of the PIC) as reference location optical elements for use in PIC alignment.

In further examples, first and second PICs can be aligned without the use of emitters, detectors, beam splitters, optical circulators, or other optical elements except those situated on the first and second PICs. In some cases, one or more detectors are situated externally to the first and second PICs while the first and second PICs include one or more emitters such as laser diodes. In some cases, one or more emitters are situated externally to the first and second PICs while the first and second PICs include one or more detectors.

Additional Representative Embodiments

Embodiment la is an alignment method, including: optically coupling respective optical probe ports of a first multi-port optical device to optical ports of a second multi-port optical device; obtaining a plurality of optical port locations of at least one of the first multiport optical device and the second multi-port optical device; and applying a rotation to at least one of the first multi-port optical device and the second multi-port optical device to reduce misalignment between the first multi-port optical device and the second multi-port optical device, wherein the rotation is determined based on an optical port spacing of at least one of the first multi-port optical device and the second multi-port optical device and at least one of the determined optical port locations.

Embodiment 1 includes the subject matter of Embodiment la, and further specifies that obtaining the plurality of optical port locations includes scanning one or both of the first multi-port optical device and the second multi-port optical device to determine the plurality of optical port locations.

Embodiment 2 includes the subject matter of Embodiment 1, and further specifies that the optical ports of the first multi-port optical device are sequentially coupled to the respective optical ports of the second multi-port optical device and the optical port locations of the second multi-port optical device are sequentially determined.

Embodiment 3 includes the subject matter of any of Embodiments 1-2, and further specifies that at least two or more ports of the first multi-port optical device are simultaneously coupled to at least two or more ports of the second multi-port optical device and associated port locations of the second multi-port optical device are determined in a common scanning of one or both of the first multi-port optical device and the second multiport optical device.

Embodiment 4 includes the subject matter of any of Embodiments 1-3, and further includes: detecting an optical beam from a selected optical port of the first multi-port optical device received from a corresponding optical port of the second multi-port optical device; and based on the detected optical beam, determining the optical port locations of one or both of the first multi-port optical device and the second multi-port optical device.

Embodiment 5 includes the subject matter of any of Embodiments 1-4, and further specifies that the optical beam from the selected optical port of the first multi-port optical device is received through a major surface the first multi-port optical device.

Embodiment 6 includes the subject matter of any of Embodiments 1-5, and further specifies that the optical beam from the selected optical port of the first multi-port optical device is received through an edge surface of the first multi-port optical device.

Embodiment 7 includes the subject matter of any of Embodiments 1-6, and further specifies that the scanning of one or both of the first multi-port optical device and the second multi-port optical device determine optical port locations and the applying the rotation are performed iteratively.

Embodiment 8 includes the subject matter of any of Embodiments 1-7, and further specifies that the first multi-port optical device includes a plurality of probe ports in a linear array and the second multi-port optical device include optical ports arranged along a first axis and a second axis.

Embodiment 9 includes the subject matter of any of Embodiments 1-8, and further specifies that at least some of the optical ports of the first multi-port optical device and the second multi-port optical device are defined by gratings situated at a major surface of the first multi-port optical device or the second multi-port optical device, respectively, or are defined by tapered couplers situated at an edge of one or both of the first multi-port optical device and the second multi-port optical device.

Embodiment 10 includes the subject matter of any of Embodiments 1-9, and further specifies that the first multi-port optical device is a multi-port optical probe or a photonic integrated circuit (PIC) and the second multi-port optical device is a photonic integrated circuit (PIC) or a multi-port optical probe, respectively.

Embodiment 11 includes the subject matter of any of Embodiments 1-10, and further includes: directing an optical beam from at least one of the optical ports of the multi-port optical probe to a corresponding optical port of the PIC; detecting an associated optical beam from at least one optical port of the PIC; and based on the detected optical beam, determining a port location of at least one optical port of the PIC with respect to the multi-port optical probe.

Embodiment 12a includes the subject matter of any of Embodiments 1-11, and further includes: directing an optical beam from a first optical port of the multi-port optical probe to a first optical port of the PIC; detecting an optical beam from a second optical port of the PIC that is responsive to the optical beam directed to the first optical port of the PIC at a second optical port of the multi-port optical probe; and based on the detected optical beam, determining a location of the first optical port of the multi-port optical probe with respect to the first optical port of the PIC.

Embodiment 12b includes the subject matter of any of Embodiments 1-11, and further includes: directing an optical beam from a first optical port of the multi-port optical probe to a first optical port of the PIC; detecting an optical beam from a second optical port of the PIC that is responsive to the optical beam directed to the first optical port of the PIC at a second optical port of the multi-port optical probe; and based on the detected optical beam, determining co-aligned location of the first optical port of the multi-port optical probe and the second optical port of the multi-port optical probe relative to the first optical port of the PIC and the second optical port of the PIC, respectively.

Embodiment 13 is an apparatus, including: a multi-port optical probe that includes a plurality of probe ports; a positioning stage adaptable to receive at least one of the multi-port optical probe and a photonic integrated circuit, wherein the positioning stage is operable to provide translation and rotation of the multi-port optical probe and the photonic integrated circuit with respect to each other; at least one beam source couplable to the multi-port optical probe to provide a probe beam from a first probe port of the plurality of probe ports of the multi-port optical probe; and at least one detector situated to receive a beam responsive to the probe beam from a second probe port of the plurality of multi-port optical probe ports; and a processor system coupled to the positioning stage and the at least one detector and operable to: translate the multi-port optical probe and the photonic integrated circuit with respect to each other to determine photonic integrated circuit port locations, determine a relative rotation to be applied to the multi-port optical probe and the photonic integrated circuit, and based on the determined photonic integrated circuit port locations and the relative rotation, operate the positioning stage to align the multi-port optical probe and the photonic integrated circuit.

Embodiment 14 includes the subject matter of Embodiment 13, and further specifies that the probe ports of the multi-port optical probe are defined by a linear array of optical waveguides.

Embodiment 15 includes the subject matter of any of Embodiments 13-14, and further specifies that the first probe port is the same as the second probe port.

Embodiment 16 includes the subject matter of any of Embodiments 13-15, and further specifies that the at least one beam source is couplable to provide a probe beam from the first probe port of the plurality of multi-port optical probe ports; and at least one detector situated to receive a beam responsive to the probe beam from a second probe port of the plurality of multi-port optical probe ports.

Embodiment 17 includes the subject matter of any of Embodiments 13-16, and further specifies that the first probe port is different from the second probe port.

Embodiment 18 includes the subject matter of any of Embodiments 13-17, and further specifies that the processor system is operable to: translate the multi-port optical probe and the photonic integrated circuit with respect to each other to determine photonic integrated circuit port locations, determine the relative rotation of the multi-port optical probe and the photonic integrated circuit based on the determined photonic integrated circuit port locations and a spacing of the multi-port optical probe, and align the multi-port optical probe and the photonic integrated circuit based on the determined photonic integrated circuit port locations and the relative rotation with the positioning stage.

Embodiment 19 includes the subject matter of any of Embodiments 13-18, and further specifies that the multi-port optical probe includes a plurality of optical fibers defining the probe ports, wherein the probe ports are arranged in a linear array or a two-dimensional array.

Embodiment 20 includes the subject matter of any of Embodiments 13-19, and further specifies that the at least one beam source is coupled to an optical circulator that directs the probe beam to the first probe port and directs the beam responsive to the probe beam from the second probe port to the detector. Embodiment 21 includes the subject matter of any of Embodiments 13-20, and further specifies that the multi-port optical probe is situated to be coupled to the photonic integrated circuit at a major surface of the photonic integrated circuit.

Embodiment 22 includes the subject matter of any of Embodiments 13-21, and further specifies that the multi-port optical probe is situated so that the probe ports are diffractively optically coupled to the photonic integrated circuit.

Embodiment 23 is an apparatus, including: a positioning stage operable to provide translations and rotations; a multi-port optical probe that includes a plurality of probe ports situated along a probe axis and defined by corresponding optical fibres, wherein the probe ports are situated to be diffractively optically coupled to a photonic integrated circuit, wherein the positioning stage is adapted to receive one or both of the multi-port optical probe and the photonic integrated circuit and provide relative translation along axes parallel to a major surface of the photonic integrated circuit and rotation about an axis perpendicular to the major surface of the photonic integrated circuit; a beam source and a detector; an optical circulator coupled to the beam source and the detector, wherein the optical circulator is situated to direct a probe beam from the beam source to a first multi-port optical probe port and receive a return beam from the photonic integrated circuit from the first multi-port optical probe port; and a processor system coupled to the positioning stage and the detector and operable to: translate the multiport optical probe and the photonic integrated circuit with respect to each other to determine photonic integrated circuit port locations along an axis perpendicular to the probe axis, determine a relative rotation to be applied to the multi-port optical probe and the photonic integrated circuit based on the photonic integrated circuit port locations and a probe port spacing along the probe axis, and based on the determined photonic integrated circuit port locations and the rotation, operate the positioning stage to align the multi-port optical probe and the photonic integrated circuit.

Having described and illustrated the principles of the disclosed technology with reference to the illustrated embodiments, it will be recognized that the illustrated embodiments can be modified in arrangement and detail without departing from such principles. For instance, elements of the illustrated embodiment shown in software may be implemented in hardware and vice-versa. Also, the technologies from any example can be combined with the technologies described in any one or more of the other examples. In view of the many possible embodiments to which these principles may be applied, it should be recognized that the illustrated embodiments are examples and should not be taken as a limitation on the scope of the disclosure. For instance, various components of systems and tools described herein may be combined in function and use. We therefore claim as all subject matter that comes within the scope and spirit of the disclosure.

Claims

We claim:

1. An alignment method, comprising: optically coupling respective optical probe ports of a first multi-port optical device to optical ports of a second multi-port optical device; obtaining a plurality of optical port locations of at least one of the first multi-port optical device and the second multi-port optical device; and applying a rotation to at least one of the first multi-port optical device and the second multi-port optical device to reduce misalignment between the first multi-port optical device and the second multi-port optical device, wherein the rotation is determined based on an optical port spacing of at least one of the first multi-port optical device and the second multiport optical device and at least one of the determined optical port locations.

2. The alignment method of claim 1, wherein obtaining the plurality of optical port locations includes scanning one or both of the first multi-port optical device and the second multi-port optical device to determine the plurality of optical port locations.

3. The alignment method of claim 2, wherein the optical ports of the first multi-port optical device are sequentially coupled to respective optical ports of the second multi-port optical device and the optical port locations of the second multi-port optical device are sequentially determined.

4. The alignment method of claim 2, wherein at least two or more ports of the first multi-port optical device are simultaneously coupled to at least two or more ports of the second multi-port optical device and associated port locations of the second multi-port optical device are determined in a common scanning of one or both of the first multi-port optical device and the second multi-port optical device.

5. The alignment method of claim 1, further comprising: detecting, from a selected optical port of the first multi-port optical device, an optical beam received from a corresponding optical port of the second multi-port optical device; and based on the detected optical beam, determining the optical port locations of one or both of the first multi-port optical device and the second multi-port optical device.

6. The alignment method of claim 5, wherein the optical beam from the selected optical port of the first multi-port optical device is received through a major surface of the first multi-port optical device.

7. The alignment method of claim 5, wherein the optical beam from the selected optical port of the first multi-port optical device is received through an edge surface of the first multi-port optical device.

8. The alignment method of claim 2, wherein the scanning of one or both of the first multi-port optical device and the second multi-port optical device to determine optical port locations and the applying the rotation are performed iteratively.

9. The alignment method of claim 1, wherein the first multi-port optical device includes a plurality of probe ports in a linear array and the second multi-port optical device includes optical ports arranged along a first axis and a second axis.

10. The alignment method of claim 1, wherein at least some of the optical ports of the first multi-port optical device and the second multi-port optical device are defined by gratings situated at a major surface of the first multi-port optical device or the second multi-port optical device, respectively, or are defined by tapered couplers situated at an edge of one or both of the first multi-port optical device and the second multi-port optical device.

11. The alignment method of claim 1, wherein the first multi-port optical device is a multi-port optical probe and the second multi-port optical device is a photonic integrated circuit (PIC).

12. The alignment method of claim 11, further comprising: directing a first optical beam via a first optical port of the multi-port optical probe to a first optical port of the PIC; detecting, via a second optical port of the multi-port optical probe, a second optical beam from a second optical port of the PIC responsive to the optical beam directed to the first optical port of the PIC; and based on the second optical beam, determining a location of the first optical port of the multi-port optical probe with respect to the first optical port of the PIC.

13. An apparatus, comprising: a multi-port optical probe that includes a plurality of probe ports; a positioning stage adaptable to receive at least one of the multi-port optical probe and a photonic integrated circuit, wherein the positioning stage is operable to provide translation and rotation of the multi-port optical probe and the photonic integrated circuit with respect to each other; at least one beam source situated to provide a probe beam to a first probe port of the plurality of probe ports of the multi-port optical probe; and at least one detector situated to receive a beam responsive to the probe beam from a second probe port of the plurality of probe ports of the multi-port optical probe; and a processor system coupled to the positioning stage and the at least one detector and operable to: translate the multi-port optical probe and the photonic integrated circuit with respect to each other to determine photonic integrated circuit port locations, determine a relative rotation to be applied to the multi-port optical probe and the photonic integrated circuit, and based on the determined photonic integrated circuit port locations and the relative rotation, operate the positioning stage to align the multi-port optical probe and the photonic integrated circuit.

14. The apparatus of claim 13, wherein the probe ports of the multi-port optical probe are defined by a linear array of optical waveguides.

15. The apparatus of claim 13, wherein the first probe port is the same as the second probe port.

16. The apparatus of claim 13, wherein the processor system is operable to repetitively: translate the multi-port optical probe and the photonic integrated circuit with respect to each other to determine photonic integrated circuit port locations; determine the relative rotation of the multi-port optical probe and the photonic integrated circuit based on the determined photonic integrated circuit port locations and a spacing of the multi-port optical probe; and align the multi-port optical probe and the photonic integrated circuit based on the determined photonic integrated circuit port locations and the relative rotation with the positioning stage.

17. The apparatus of claim 13, wherein the multi-port optical probe includes a plurality of optical fibers defining the probe ports, wherein the probe ports are arranged in a linear array or a two-dimensional array.

18. The apparatus of claim 13, wherein the at least one beam source is coupled to an optical circulator that directs the probe beam to the first probe port and directs the beam responsive to the probe beam from the second probe port to the detector.

19. The apparatus of claim 13, wherein the multi-port optical probe is situated to be coupled to the photonic integrated circuit at a major surface of the photonic integrated circuit or at an edge surface of the photonic integrated circuit.

20. An apparatus, comprising: a positioning stage operable to provide translations and rotations; a multi-port optical probe that includes a plurality of probe ports situated along a probe axis and defined by corresponding optical fibres, wherein the probe ports are situated to be diffractively optically coupled to a photonic integrated circuit, wherein the positioning stage is adapted to receive one or both of the multi-port optical probe and the photonic integrated circuit and provide relative translation along axes parallel to a major surface of the photonic integrated circuit and rotation about an axis perpendicular to the major surface of the photonic integrated circuit; a beam source; a detector; an optical circulator coupled to the beam source and the detector, wherein the optical circulator is situated to direct a probe beam from the beam source to a first probe port of the plurality of probe ports and receive a return beam from the photonic integrated circuit via the first probe port; and a processor system coupled to the positioning stage and the detector and operable to: translate the multi-port optical probe and the photonic integrated circuit with respect to each other to determine photonic integrated circuit port locations along an axis perpendicular to the probe axis; determine a relative rotation to be applied to the multi-port optical probe and the photonic integrated circuit based on the photonic integrated circuit port locations and a probe port spacing along the probe axis; and based on the photonic integrated circuit port locations and the relative rotation, operate the positioning stage to align the multi-port optical probe and the photonic integrated circuit.