Photonic chip having guiding and non-guiding structures, and method of modifying same

Abstract

There is described a method of modifying a photonic chip having a guiding structure and a cladding matrix surrounding the guiding structure, the guiding structure and the cladding matrix configured for guiding an optical mode within the photonic chip. The method generally having: directing a corrective laser beam within a non-guiding structure of the photonic chip, the non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the non-guiding structure having a material different from a material of the cladding matrix, said directing creating a permanent structural change within the non-guiding structure, the permanent structural change spatially extending into the cladding matrix between the non-guiding structure and the guiding structure, the permanent structural change permanently modifying an effective refractive index of the guiding structure.

Description

PHOTONIC CHIP HAVING GUIDING AND NON-GUIDING STRUCTURES, AND METHOD OF MODIFYING SAMEFIELD

[0001] The improvements generally relate to photonic chips and more particularly to the manufacturing and testing of such photonic chips.BACKGROUND

[0002] In a manner analogous to electronic chips processing electronic signals, photonic chips process optical signals. Photonic chips are typically manufactured using foundry processes used for microelectronics manufacturing. Microelectronics foundry processes can reach tolerances of about 1.5 nm at the most which while satisfactory for state-of-the-art microelectronics may be insufficient for photonic chip manufacturing. As such, each photonic chip manufactured using known foundry processes is rigorously inspected and tested to make sure it is conform to design specifications. Once a photonic chip has been identified as defective, it may be discarded which can lead to significant losses in terms of materials and time. Although existing techniques for manufacturing photonic chips are satisfactory to a certain degree, there always remains room for improvement.SUMMARY

[0003] There is described methods and systems for modifying photonic chips and especially photonic chips that have been identified as defective for failing to meet design tolerance(s) and / or performances parameter(s) according to individual inspection and testing. The methods and systems involve a testing routine in which parameter(s) indicative of a performance of the photonic chip’s guiding structure(s), such as semiconductor waveguide(s), is measured and in some cases even monitored over time. Examples of such parameters can include, but are not limited to, wavelength, phase, amplitude, polarization, dispersion, gain and / or loss, to name a few examples. When a defective photonic chip is identified, a corrective laser beam is used, e.g., before, during or after the monitoring of the parameter(s), to perform permanent structural changes into one or more non-guiding structures that are located proximate to the guiding structures which actually propagate optical modes during use of the photonic chip. The non-guiding structures are spaced apart, but relatively proximate to, thecorresponding guiding structures. Moreover, the non-guiding structures are made of a material such as a semiconductor material or a metallic material that is different from a material of a cladding matrix surrounding the guiding structures. In this way, the permanent structural changes that are laser-induced within the non-guiding structures can mechanically propagate beyond the non-guiding structures into a portion of the cladding matrix extending between corresponding ones of the non-guiding structures and the guiding structures. These mechanically propagating permanent structural changes can in turn cause changes in effective refractive indexes of the proximate guiding structures. In some embodiments, the laser-induced permanent structural changes are provided in the form of cracks running around and away from the non-guiding structures. Such permanent structural changes and testing routine can be performed iteratively until the monitored parameters match corresponding reference parameters of a reference photonic chip. In at least some instances, the laser- induced permanent structural changes can result in the tuning of the performance of a defective photonic chip up to a level where the photonic chip can become effectively defectless.

[0004] It is understood that, in some embodiments, the photonic chips are intently designed to incorporate customized non-guiding structures into the photonic chips for tuning purposes. In these embodiments, it is encompassed that as the permanent structural changes are laser- induced in non-guiding structures that are morphologically different from the surrounding cladding matrix, the resulting mechanical stress can be controlled, or at least influenced, by characteristics, including a geometry, a shape, a positioning, a material and the like, of the corresponding non-guiding structures. However, in some other embodiments, conventional photonic chips that may not have been designed to incorporate such customized non-guiding structures. However, most of these conventional photonic chips can still be modified as they may already incorporate at least some non-guiding structures which can be targeted for the laser-inducing of permanent structural changes.

[0005] In accordance with a first aspect of the present disclosure, there is provided a method of modifying a photonic chip having a guiding structure and a cladding matrix surrounding the guiding structure, the guiding structure and the cladding matrix configured for guiding an optical mode within the photonic chip, the method comprising: directing a correctivelaser beam within a non-guiding structure of the photonic chip, the non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the nonguiding structure having a material different from a material of the cladding matrix, said directing creating a permanent structural change within the non-guiding structure, the permanent structural change spatially extending into the cladding matrix between the nonguiding structure and the guiding structure, the permanent structural change permanently modifying an effective refractive index of the guiding structure; performing a testing routine on the photonic chip including determining a parameter indicative of a performance of the guiding structure; and upon determining that the parameter mismatches a reference parameter associated with a reference photonic chip, repeating said directing and said testing routine until the parameter matches the reference parameter within a given tolerance.

[0006] Further in accordance with the first aspect of the present disclosure, the permanent structure change can for example include one or more cracks running within the cladding matrix between the non-guiding structure and the guiding structure.

[0007] Still further in accordance with the first aspect of the present disclosure, the one or more cracks can for example originate from one or more corresponding apexes or edges of the non-guiding structure.

[0008] Still further in accordance with the first aspect of the present disclosure, the nonguiding structure can for example extend within the cladding matrix at least one of: below, above and on a lateral side of the guiding structure.

[0009] Still further in accordance with the first aspect of the present disclosure, the nonguiding structure can for example have a body and one or more pointy members protruding from the body and facing the guiding structure through the cladding matrix, the permanent structure change can for example extend from one or more pointy members towards the guiding structure.

[0010] Still further in accordance with the first aspect of the present disclosure, the one or more pointy members can for example be two-dimensional pointy members, the two-dimensional pointy members can for example extend in a plane one of parallel with a plane of the photonic chip and perpendicular to the guiding structure.

[0011] Still further in accordance with the first aspect of the present disclosure, the nonguiding structure is a first non-guiding structure, the permanent structural change is a first permanent structural change, the method further comprising: directing the corrective laser beam within a second non-guiding structure of the photonic chip, the second non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the second non-guiding structure having a material different from a material of the cladding matrix, said directing creating a second permanent structural change within the nonguiding structure, the second permanent structural change spatially extending into the cladding matrix between the second non-guiding structure and the guiding structure, the permanent stress permanently further modifying the effective refractive index of the guiding structure.

[0012] Still further in accordance with the first aspect of the present disclosure, the nonguiding structure can for example have a shape closely matching a shape of the guiding structure.

[0013] Still further in accordance with the first aspect of the present disclosure, the nonguiding structure can for example include at least one of: a semiconductor material, a metallic material, a glass material, and a polymer material.

[0014] Still further in accordance with the first aspect of the present disclosure, the guiding structure can for example include a semiconductor material.

[0015] Still further in accordance with the first aspect of the present disclosure, the method can for example further comprise, using a guiding structure protector extending at least one of within the cladding matrix and on a top surface of the cladding matrix, obstructing at least a portion of the corrective laser beam and protecting at least a portion of the guiding structure from the corrective laser beam.

[0016] Still further in accordance with the first aspect of the present disclosure, the material of the non-guiding structure can for example be a semiconductor material having a bandgapwavelength, the corrective laser beam having a central wavelength below the bandgap wavelength of the semiconductor material of the non-guiding structure.

[0017] In accordance with a second aspect of the present disclosure, there is provided a photonic chip comprising: a guiding structure; a cladding matrix surrounding the guiding structure, the guiding structure and the cladding matrix configured for guiding an optical mode within the photonic chip; and a non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the non-guiding structure having a material different from a material of the cladding matrix, said non-guiding structure having a laser- induced permanent structural change within the non-guiding structure, the laser-induced permanent structural change spatially extending into the cladding matrix between the nonguiding structure and the guiding structure, the permanent structural change permanently modifying an effective refractive index of the guiding structure.

[0018] Further in accordance with the second aspect of the present disclosure, the permanent structure change can for example include one or more cracks running within the cladding matrix between the non-guiding structure and the guiding structure.

[0019] Still further in accordance with the second aspect of the present disclosure, the one or more cracks can for example originate from one or more corresponding apexes or edges of the non-guiding structure.

[0020] Still further in accordance with the second aspect of the present disclosure, the nonguiding structure can for example extend within the cladding matrix at least one of: below, above and on a lateral side of the guiding structure.

[0021] Still further in accordance with the second aspect of the present disclosure, the nonguiding structure can for example have a body and one or more pointy members protruding from the body and facing the guiding structure through the cladding matrix, the permanent structure change can for example extend from one or more pointy members towards the guiding structure.

[0022] Still further in accordance with the second aspect of the present disclosure, the nonguiding structure can for example have a shape closely matching a shape of the guiding structure.

[0023] Still further in accordance with the second aspect of the present disclosure, the nonguiding structure can for example include at least one of: a semiconductor material, a metallic material, a glass material, and a polymer material.

[0024] Still further in accordance with the second aspect of the present disclosure, the photonic chip can for example further comprise a guiding structure protector extending at least one of within the cladding matrix and on a top surface of the cladding matrix, the guiding structure protector made of a material non-transparent to a corrective laser beam.

[0025] In accordance with a third aspect of the present disclosure, there is provided a system for modifying a photonic chip having a guiding structure and a cladding matrix surrounding the guiding structure, the guiding structure and the cladding matrix configured for guiding an optical mode within the photonic chip, the system comprising: a corrective laser apparatus configured for directing a corrective laser beam within a portion of a non-guiding structure of the photonic chip, the non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the non-guiding structure having a material different from a material of the cladding matrix, said directing creating a permanent structural change within the non-guiding structure, the permanent structural change spatially extending into the cladding matrix between the non-guiding structure and the guiding structure, the permanent structural change permanently modifying an effective refractive index of the guiding structure; a photonic chip testing apparatus performing a testing routine on the guiding structure including determining a parameter indicative of a performance of the guiding structure; and a controller communicatively coupled to the corrective laser apparatus and to the photonic chip testing apparatus, the controller having a processor and a memory having stored thereon instructions that when executed by the processor perform the steps of: comparing the parameter to a reference parameter associated with a reference photonic chip; and upon determining that the parameter mismatches the reference parameter, repeating said directing and said testing routine until the parameter matches the reference parameter within a given tolerance.

[0026] In accordance with a fourth aspect of the present disclosure, there is provided a method of modifying a photonic chip having a guiding structure and a cladding matrix surrounding the guiding structure, the guiding structure and the cladding matrix configured for guiding an optical mode within the photonic chip, the method comprising: directing a corrective laser beam within a non-guiding structure of the photonic chip, the non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the nonguiding structure having a material different from a material of the cladding matrix, said directing creating a permanent structural change within the non-guiding structure, the permanent structural change spatially extending into the cladding matrix between the nonguiding structure and the guiding structure, the permanent structural change permanently modifying an effective refractive index of the guiding structure.

[0027] Further in accordance with the fourth aspect of the present disclosure, the method can for example further comprise: performing a testing routine on the photonic chip including determining a parameter indicative of a performance of the guiding structure; and upon determining that the parameter mismatches a reference parameter associated with a reference photonic chip, repeating said directing and said testing routine until the parameter matches the reference parameter within a given tolerance.

[0028] All technical implementation details and advantages described with respect to a particular aspect of the present invention are self-evidently mutatis mutandis applicable for all other aspects of the present invention.

[0029] Many further features and combinations thereof concerning the present improvements will appearto those skilled in the art following a reading of the instant disclosure.DESCRIPTION OF THE FIGURES

[0030] In the figures,

[0031] Fig. 1 is a schematic view of an example of a system for modifying a photonic chip having guiding and non-guiding structures, showing an exemplary permanent structure change within the non-guiding structure, in accordance with one or more embodiments;

[0032] Figs. 1 A and 1 B are dark field and bright field images of a yet another example of a permanent structure change laser-induced within the non-guiding structure of Fig. 1 , in accordance with one or more embodiments;

[0033] Fig. 2A is an oblique view of the photonic chip of Fig. 1 onto which a testing routine is being performed and showing a measured parameter mismatch, in accordance with one or more embodiments;

[0034] Fig. 2B is an oblique view of the photonic chip of Fig. 1 receiving a corrective laser beam within the non-guiding structure, in accordance with one or more embodiments;

[0035] Fig. 2C is an oblique view of the photonic chip of Fig. 1 onto which a subsequent testing routine is being performed and showing a measured parameter match, in accordance with one or more embodiments;

[0036] Fig. 3 is a graph showing the spatial mode propagating into the photonic chip of Fig. 2A, in accordance with one or more embodiments;

[0037] Fig. 4 is a graph showing the spatial mode propagating into the guiding structure of the photonic chip of Fig. 2C, in accordance with one or more embodiments;

[0038] Fig. 4A is an enlarged of the non-guiding structure of the photonic chip of Fig. 2C, in accordance with one or more embodiments;

[0039] Fig. 5 is a flow chart of an example method of modifying a photonic chip having a guiding structure and a cladding matrix surrounding the guiding structure, in accordance with one or more embodiments;

[0040] Fig. 6A is a top plan view of a first example of a photonic chip incorporating a Y- combiner having an input port and output ports, shown with non-guiding structures extending alongside the output ports, in accordance with one or more embodiments;

[0041] Fig. 6B is a top plan view of a second example of a photonic chip incorporating a Y- combiner having an input port and output ports, shown with non-guiding structures extending proximate the input port, in accordance with one or more embodiments;

[0042] Fig. 7 is a top plan view of a third example of a photonic chip incorporating a directional coupler, shown with a non-guiding structure extending along a strip guiding structure, in accordance with one or more embodiments;

[0043] Fig. 8 is a top plan view of a fourth example of a photonic chip incorporating an arrayed waveguide grating extending between two star couplers, shown with non-guiding structures extending alongside waveguides of the arrayed waveguide grating, in accordance with one or more embodiments;

[0044] Fig. 9 is a cross-sectional view of a fifth example of a photonic chip incorporating a substrate, a cladding matrix covering the substrate, guiding structures within the cladding matrix, and a non-guiding structure within the cladding matrix and between the substrate and the guiding structures, in accordance with one or more embodiments;

[0045] Fig. 10 is a cross-sectional view of a sixth example of a photonic chip incorporating a substrate, a cladding matrix covering the substrate, a guiding structure within the cladding matrix, and a non-guiding structure having a permanent structural change enhancing shape, in accordance with one or more embodiments;

[0046] Fig. 11 is a cross-sectional view of a seventh example of a photonic chip incorporating a substrate, a cladding matrix covering the substrate, a guiding structure within the cladding matrix, and a non-guiding structure, shown with a guiding structure protector, in accordance with one or more embodiments;

[0047] Figs 12A to 12E are top plan views of exemplary photonic chip incorporating guiding structures and non-guiding structures that are shaped and sized to enhance specific laser- induced permanent structural changes, in accordance with one or more embodiments; and

[0048] Fig. 13 is a schematic view of an example of a computing device of a controller of the system of Fig. 1 , in accordance with one or more embodiments.DETAILED DESCRIPTION

[0049] Fig. 1 shows an example of a system 100 for modifying a photonic chip 10. The system 100 can be used at any testing stages of the manufacture or the life of the photonicchip 10. For instance, the system 100 can be used at a design stage where the photonic chip 10 is prototyped and corrected iteratively as desired, at a foundry stage where the photonic chip 10 is mass produced and / or at a packaging stage where the photonic chip 10 is integrated into a package, for instance. In any case, the photonic chip 10 can be modified at any time after its performance is monitored to be insufficient.

[0050] As shown, the photonic chip 10 generally has a guiding structure 12, a cladding matrix 14 wholly or partially surrounding the guiding structure 12, and a non-guiding structure 16 spaced-apart from the guiding structure 12. In some embodiments, the cladding matrix 14 can be made of any material having a refractive index lower than a refractive index of the material of the guiding structure 12 to allow proper confinement and propagation of an optical mode along the guiding structure 12. In this example, the guiding structure 12, the cladding matrix 14 and the non-guiding structure 16 are received directly on a substrate 11. However, in some other embodiments, the guiding structure 12 and the non-guiding structure 16 can be suspended over the substrate 11 . The substrate 11 can be omitted in some other embodiments.

[0051] Still referring to Fig. 1 , the system 100 is configured for directing a corrective laser beam 112, or a focal point 1 14 thereof, within the non-guiding structure 16. As such, the corrective laser beam 1 12 forms a laser-induced permanent structural change 20 within the non-guiding structure 16. As the non-guiding structure 12 has a material which is different from a material of the cladding matrix 14, the permanent structural change 20 causes internal mechanical stress within the photonic chip 10, and more specifically within a portion of the cladding matrix 14 surrounding the non-guiding structure 16. In some embodiments, the permanent structural change 20 is provided in the form of one or more cracks 20’ which originates from the non-guiding structure 16 and runs through the cladding matrix 14 and towards the guiding structure 12. Additionally or alternatively, the permanent structure change 20 can be provided in the form of a compressive stress, a tensile stress, a shear stress, a torsion stress, or a combination thereof. Figs. 1 A and 1 B show dark and bright field images of yet another example of such a permanent structure change 20”. In this example, the permanent structure change 20” forms an ear-like deformation surrounding the non-guiding structure 16. As such, the laser-induced permanent structural changes 20, 20’ and 20”spatially extend into the cladding matrix 14 between the non-guiding structure 16 and the guiding structure 12, which can in turn modify an effective refractive index of the guiding structure 12. It is thus intended that, during use of the photonic chip 10, the guiding structure 12 and the cladding matrix 14 are configured for guiding the optical mode across the photonic chip 10 along the guiding structure 12 while the non-guiding structure 16 cannot guide the optical mode due at least to the laser-induced permanent structural change 20 extending within the non-guiding structure 16.

[0052] The guiding structure 12 can include any type of semiconductor waveguide used in photonic chips. For instance, the guiding structure 12 can have a strip waveguide, a rib waveguide, a slot waveguide, a photonic crystal waveguide, a subwavelength waveguide grating (SWG) waveguide, fiber waveguide, a SWG slot waveguide, a SPP slot waveguide, a suspended waveguide, and the like. The guiding structure 12 can be part of a photonic component including, but not limited to, couplers), directional coupler(s), star coupler(s), Y combiner(s), star coupler(s), array waveguide grating(s), interferometer(s), Mach-Zehnder interferometer(s), multimode interferometer(s)), ring resonator(s), spot size converter(s), waveguide Bragg grating(s), and the like.

[0053] The guiding structure 12 and the cladding matrix 14 can include one or more materials such as semiconductor materials, glass materials and the like. Examples of semiconductor materials can include, but are not limited to, silicon, silicon nitride (SiN), silicon- on-insulator (SOI), germanium (Ge), indium phosphide (InP), silicon carbide (SiC), gallium nitride (GaN), indium gallium arsenide (InGaAs), gallium arsenide (GaAs), lithium niobate (LiNbO3), indium antimonide (InSb), mercury cadmium telluride (MCT), insidum arsenide (InAs), lead selenide (PbSe), lead sulfide (PbS), chalcogenide-based materials such as sulphide-based materials, selenide-based materials, telluride-based materials, any doped semiconductor including n-type doping, p-type doping, germanium doping, silicon doping, boron doping, arsenic doping, carbon doping, helium doping, antimony doping, and / or active laser material doping such as rare earth ion doping like erbium, ytterbium, quantum dot, gas. Examples of glass materials can include, but are not limited to, doped or undoped silica-based glasses, doped or undoped chalcogenide glasses, doped or undoped fluoride-based glass, buried oxide (BOX), and the like.

[0054] It is intended that the non-guiding structure 16 can be provided in any suitable size, shape or form. For instance, the non-guiding structure 16 can be provided in the form of a strip member, a rib member, a slot member, a photonic crystal member, a fiber waveguide, and the like. Typically, the non-guiding structure 16 is sufficiently spaced apart from the guiding structure 12 to prevent the corrective laser beam 112 to laser-induce modifications within the guiding structure 12, but sufficiently close to the guiding structure 12 so that the laser-induced permanent structural change 20 extending within the non-guiding structure 16 can affect the guiding properties of the nearby guiding structure 12. For instance, in some embodiments, the guiding structure 12 and the non-guiding structure 16 are spaced-apart by 10 pm, preferably 5 pm, and most preferably below 4 pm. In some embodiments, the photonic chip 1 1 extends in a x-y plane, with a thickness extending along a z-axis. In these embodiments, the nonguiding structure 16 may be spaced apart from the guiding structure 12 along one or more of the x-, y- and z-axes, depending on the embodiment. In certain embodiments, the non-guiding structure 16 runs alongside the guiding structure 12. In these embodiments, the spacing between the guiding structure 12 and the non-guiding structure 16 can be even. In some other embodiments, this spacing can be converging, diverging, uneven, and the like. As discussed in further detail below by way of examples, the guiding structure 12 and the non-guiding structure 16 may be similar in shape or size, albeit spaced-apart from one another. However, in some other embodiments, the guiding structure 12 and the non-guiding structure 16 bear dissimilar shape or size.

[0055] It is understood that to enhance the laser-induced permanent structural change 20, the material of the non-guiding structure 16, which is targeted by the corrective laser beam 112, is different from the material of the surrounding cladding matrix 14. Accordingly, the absorption properties of the materials of the non-guiding structure 16 and of the surrounding cladding matrix 14 are different. Preferably, the material of the non-guiding structure 16 has an absorption property (i.e., the extent at which the material optically absorbs the corrective laser beam) which is greaterthan the material of the cladding matrix 14. For instance, in some embodiments where the guiding structure 12 is made of silicon, the cladding matrix 14 may be made of silicon dioxide or any other suitable material different from silicon (e.g., doped silicon). The non-guiding structure 16 can be made of any semiconductor material (especially those easily implementable in a complementary metal-oxide semiconductor (CMOS) processlike germanium, silicon nitride, etc.), metallic structures, other glass structures (doped glass) or even polymer structures, depending on the embodiment. In some embodiments, the nonguiding structure can be a hollow cavity which surfaces are modified using the corrective laser beam. In these embodiments, the hollow cavity can be filled with air or another gas. As will be discussed below, the guiding structure 12 and the non-guiding structure 16 can be separate from one another in some embodiments, whereas they can be made integral to one another in some other embodiments. In these latter embodiments, although they are made integral to one another, the non-guiding structure 16 may not be adapted for guiding an optical mode due to its size, positioning relative to the other photonic components, its laser-induced permanent structural changes, and the like.

[0056] As shown, the system 100 has a corrective laser apparatus 110 and a photonic chip testing apparatus 120. In some embodiments, the system 100 can also incorporate a computer vision apparatus 130 incorporating a camera 132 imaging the photonic chip 10 in real time. A multi-axis movement stage 140 can optionally be used for moving the photonic chip 10 within a working zone as desired. The multi-axis movement stage 140 can be a translation stage and / or a rotation stage. In some embodiments, the corrective laser apparatus 1 10 can be made integral to existing photonic testing apparatuses.

[0057] The system 100 can have a controller 150 which is communicatively coupled to the corrective laser apparatus 110, the photonic chip testing apparatus 120, the computer vision apparatus 130 and / or the multi-axis moving stage 140, for instance. The controller 150 has a processor and a memory having stored thereon instructions that when executed by the processor perform preprogrammed instructions and / or method steps. To do so, the controller 150 generally incorporates hardware components provided in the form of a computing device and software components provided in the form of programs, algorithms and the like for performing the method steps. An example of the computing device is described below.

[0058] As depicted, the corrective laser apparatus 110, the photonic chip testing apparatus 120, the computer vision apparatus 130 and the multi-axis moving stage 140 can be fixedly or removably mounted to a frame 106. In this specific embodiment, the frame 106 is provided in the form of an optical bench or table. However, it is understood that in some other embodiments the corrective laser apparatus 110, the photonic chip testing apparatus 120, thecomputer vision apparatus 130 and the multi-axis moving stage 140 can be mounted independently from one another at different locations of a photonic chip production line, for instance. In some embodiments, electronic probes and / or fiber probes of the photonic chip testing apparatus 120 can be in the path of the corrective laser beam 112 of the corrective laser apparatus 1 10. In these embodiments, the corrective laser apparatus 110, a laser source thereof or an output thereof can be moved as desired above or below the photonic chip 10. Such movement can be generated using a two-axes or three-axes galvanometer scanner, a coarse gantry mechanism for movement within a centimeter squared, a fine gantry mechanism for movement within a relatively small area (e.g., 100 pm x 100 pm, 10 x 10 pm), a piezo micropositioner (e.g., an hexapod, a spatial light modulator (SLM)), an optical fiber cable with a microlens tip, a six degrees of freedom robotic arm, any other motion apparatus with or without moving part(s) that can translate and / or deflect the corrective laser beam 112, and / or any combination thereof

[0059] It is intended that the corrective laser beam 1 12 is selected to its central wavelength is well-suited for causing the permanent structural changes 20 to the material of the nonguiding structure 16. For instance, the central wavelength of the corrective laser beam can range between about 200 nm and about 20 pm, preferably between about 500 nm and about 10 pm and most preferably about between about 1 pm and about 3.4 pm. As such, optical energy can be delivered within the photonic chip 10, i.e., and more specifically within the nonguiding structure 16. In embodiments where the non-guiding structure 16 includes silicon, it was found convenient to use an infrared laser beam having a narrow spectral bandwidth (or central wavelength, equivalently) centered at about 2.8 pm, for instance. It is noted that the mid-infrared laser beam can be generated using a fiber laser source having a fiber segment made of a low phonon energy glass and having at least one laser-active doped region extending along the fiber segment. An example of such a fiber laser source is described in U.S. Patent No. 10,084,287 B2, the contents of which are hereby incorporated by reference.

[0060] Fig. 2A shows the photonic chip 10 of Fig. 1 onto which a testing routine is being performed by the photonic chip testing apparatus 120. As shown, the photonic chip testing apparatus 120 determines a parameter P indicative of a performance of the guiding structure 12. When the measured parameter P and a reference parameter PREF of a reference photonicchip mismatch to one another within a given tolerance TOL, i.e., when P [PREF ~ TOL; PREF+ TOL], the photonic chip 10 may be identified as defective. Instead of discarding the defective photonic chip 10, the photonic chip 10 is modified using the system 100. The reference photonic chip may correspond to a reference photonic chip that is deemed to be defectless or conform to design tolerance(s), for instance. The reference parameter(s) PREF can be stored on a memory system accessible to the controller 150. In some embodiments, each photonic chip being tested has an identifier identifying the type of photonic chip and one or more reference parameters P EF associated to the type of photonic chip. When such a photonic chip is being tested, the controller 150 can fetch the photonic type and / or the associated reference parameters PREF

[0061] In some embodiments, the photonic chip testing apparatus 120 has a test optical source 122 guiding a test optical signal 124 into and along a first end 12a of the guiding structure 12 and a detector 126 detecting an output signal 128 resulting from the guiding of the test optical signal 124. The test optical signal 124 can be injected using grating coupler(s), side coupler(s), free-space injection setup(s) and the like. In some embodiments, the test optical signal can also be generated using an integrated laser on the chip. The output optical signal 128 can be detected using an integrated photodiode, a fiber probe, a free space detector, a spectrophotometer, a standard, infrared or hyperspectral camera imaging scattering outgoing from the photonic chip 10, to name a few examples. In these embodiments, the controller 150 can determine the parameter P based on the output signal 128. As shown in the specific embodiment of Fig. 2A, the detector can be a photodiode optically coupled to a second end 12b of the guiding structure 12 for detecting the output signal 128. In some embodiments, the detector is an infrared camera measuring the output signal scattering away from the guiding structure during the guiding of the test optical signal 124. The camera(s) can be part of the computer vision apparatus 130. It is intended that the testing routine needs not to be based solely on optical technologies. For instance, in some other embodiments, the testing routine involves optical modulation based on radio-frequency signals and / or electronic measurements.

[0062] As shown in Fig. 2B, the corrective laser apparatus 110 is used to direct a corrective laser beam 1 12, and more specifically a focal point 114 thereof, within a portion of the non-guiding structure 16. The corrective laser beam 1 12 can be moved along a path of the nonguiding structure 16. In some embodiments, the path can be linear or can otherwise follow s shape of the non-guiding structure 16. Due to the permanent structural changes made proximate to the guiding structure 12, an effective refractive index of the portion of the guiding structure 12 can be modified by a certain extent, including positive or negative refractive index changes. The effective refractive index modification can cause the performance of the guiding structure 12 and overall photonic chip 10 to be modified accordingly.

[0063] As depicted in Fig. 2C, the modified photonic chip 10 can be tested again using the testing routine to determine whether the measured parameter P now matches the reference parameter PREF within the given tolerance TOL, i.e., if P [PREF- TOL; PREF+ TOP], These steps can be repeated iteratively until a match is found, i.e., until the photonic chip 10 performs to a level where it can be deemed to be defectless. Once the modified photonic chip 10 has a pass on the testing routine, it can be put back into and along the photonic chip production line, thereby reducing the amount of photonic chips that are discarded after a failed testing routine. Considering that in some embodiments 50 % to 80 % of all photonic chips being produced using existing microelectronics foundry techniques may be defective, it is hypothesised that the system 100 can reduce such a photonic chip discard rate by at least 25 %, preferably below at least 50 % and most preferably at least 75 % using the methods and systems described herein compared to conventional manufacturing processes. It is also noted that the methods and systems described herein can correct defective photonic chips at relatively high speed.

[0064] Fig. 3 shows a visual representation of the optical mode propagating unaltered along the guiding structure 12 of the photonic chip of Fig. 2A, prior to the formation of the permanent structural change within the non-guiding structure proximate to the guiding structure 12. In contrast, Fig. 4 shows a visual representation of the optical mode propagating in an altered fashion along the guiding structure 12 of the photonic chip of Fig. 2A, after the laser-inducing of the permanent structural change 20 within the non-guiding structure proximate to the guiding structure 12. As shown, the optical mode illustrated in Fig. 4B slightly differs from the optical mode shown in Fig. 3B, as the permanent structure change 20 affects the coupling conditions of the guiding structure 12. An enlarged view of the permanent structure change 20is shown in Fig. 4A. As depicted, the permanent structure change 20 has cracks extending from the non-guiding structure 12 and away therefrom.

[0065] Fig. 5 shows a flow chart of an example method 500 of modifying a photonic chip having a guiding structure and a cladding matrix surrounding the guiding structure. As discussed above, the guiding structure and the cladding matrix are configured for guiding an optical mode within the photonic chip. It is understood that the method 500 can be performed using the system of Fig. 1 or any other suitable system for laser-modifying a photonic chip.

[0066] At step 502, a corrective laser beam is directed within a non-guiding structure of the photonic chip. As discussed above, the non-guiding structure is spaced-apart from the guiding structure and the optical mode propagating therealong. The non-guiding structure has a material different from a material of the cladding matrix. In some embodiments, the corrective laser beam may be a collimated beam, however the corrective laser beam is preferably converging so as to direct a focal point of the corrective laser beam where desired. In these latter embodiments, the step 502 of directing the corrective laser beam includes a step of directing a focal point of the corrective laser beam within the non-guiding structure. The focal point of the corrective laser beam can have a dimension ranging between about 200 nm and 100 pm, preferably between about 1 pm and 10 pm,, and most preferably of about 5 pm. The step 502 of directing includes a step of creating a permanent structural change within the nonguiding structure by way of the corrective laser beam. The permanent structural change spatially extends into the cladding matrix between the non-guiding structure and the guiding structure in a way which can permanently modifying an effective refractive index of the guiding structure.

[0067] At step 504, a testing routine is performed on the photonic chip. The step 504 includes a step of determining a parameter P indicative of a performance of the guiding structure.

[0068] At step 506, upon determining that the parameter mismatches a reference parameter associated with a reference photonic chip, the steps 502 and 504 are repeated until the parameter matches the reference parameter PREF within a given tolerance TOL. If theparameter P is deemed to match the reference parameter PREF, within a given tolerance TOL, the steps 504 and 504 are not necessarily repeated.

[0069] In some embodiments, the testing routine of step 504 can be performed before, during, and / or after the step 502 of directing the corrective laser beam within the non-guiding structure. In embodiments where the testing routine is performed before the step 502 of directing, a baseline of the performance of the photonic chip can be established before corrective actions can be performed. In some situations, the performance of a given photonic chip is satisfactory, and the rest of the steps are omitted. In some other situations, the performance of the given photonic chip is unsatisfactory, and the rest of the steps are performed (and in some cases repeated) until the parameter indicative of the performance reaches the reference parameter P EF.

[0070] It is noted that in some embodiments the photonic chip 10 can have a number of different guiding structures 12. In these embodiments, the method 50 can include a step of performing the step 502 and the step of 504 with respect to a number of non-guiding structures 16 each being associated with one or more of the guiding structures 12 until the parameters Pi pertaining to the guiding structures 12 match a respective reference parameter PREF within a given tolerance TOL i. In some embodiments, the reference parameters can be the same for each of the guiding structures 12 (i.e., PREF = PREF, 2= PREF ). However, in some other embodiments, each guiding structure 12 has a dedicated reference parameter.

[0071] At step 508, the step 502 of directing can include a step of moving at least one of the corrective laser beam and the photonic chip along a path overlapping with the non-guiding structure(s). In some embodiments, the path can be circumscribed by a x-y plane in which the photonic chip extends. In some other embodiments, the path can be three-dimensional and rather extend within the x, y and z space. For instance, the step 508 includes moving the focal point of the corrective laser beam relative to the guiding structure of the photonic chip. Additionally or alternatively, the step 502 includes moving the photonic chip relative to the focal point of the corrective laser beam. In these embodiments, the relative movement between the focal point of the corrective laser beam and the guiding structure can define a path. The path can be parallel to a plane of the photonic chip in some embodiments. For instance, the path can be linear, arcuate, circular and arbitrary depending on the embodiment.The path needs not to be confined to a plane as it can have a three-dimensional topography as well. It is noted that step 508 is optional as it can be omitted in some embodiments.

[0072] In some embodiments, the corrective laser beam is pulsed and the step of moving the focal point of the corrective laser beam along the path includes the delivery of one or more laser pulses at each of a number of spaced apart points distributed evenly or unevenly along the non-guiding structures overlapping with the path. The laser pulses can have a time duration ranging between about 10 fs and about 1000 ns, preferably between about 100 fs and about 500 ns and most preferably between about 250 fs and about 250 ns. The laser pulses can carry an optical fluence ranging between about 0.01 J / cm2and about 100 J / cm2. The laser pulses can carry an optical energy ranging between about 1 nJ and about 1 mJ, preferably between about 10 nJ and about 0.1 mJ and most preferably between about 100 nJ and about 10 pJ. It is intended that the focal point of the corrective laser beam can be sufficiently intense to cause nonlinear absorption into the photonic chip. Depending on the embodiment, the absorption of the corrective laser beam by the non-guiding structure can be linear absorption as well, or a combination of both nonlinear and linear absorption. Examples of such nonlinear absorption mechanisms can include, but are not limited to, multi-photon absorption, tunnel ionisation, free-carrier absorption, impact ionisation, and the like. Such nonlinear absorption mechanisms are generally achieved using fast (sub ps) melting and resolidification light-matter processes. More specifically, such non-linear absorption mechanisms can excite the electrons from the valence band to the conduction band, thus generating free-carriers. The material modification, causing the refractive index change, can depend on the density of carriers, their excited energy level (electron temperature) and / or the temporal dynamics of the energy transfers between the photon, electron and phonons. The material modification can include, but is not limited to, crack or defect formation, ablation, melting and solidification, refractive index change, to name a few examples. Generally, to maximize the possible bandwidth of the refractive index change, carrier density and electron temperature can be maximized. In some embodiments, the corrective laser beam causes an explosion (or implosion) of a portion (or a totality) of the non-guiding structure, which then causes the permanent structural change causing the effective refractive index change of the guiding structure nearby. Generally, in the fast (sub ps) temporal regime when the modification threshold is reached, fast melting and resolidification can occur. In some applications, a laserwavelength below, equal or above the semiconductor bandgap wavelength of the non-guiding structure is employed. In these applications, strong surfacic one-photon photoionization can drive the absorption process causing limited tuning bandwidth due to weak and shallow material modification. In addition, photoionization driven semiconductor modification can lead to limited excited electron temperature and enhanced plasma shielding. Whereas employing laser pulses with a wavelength above the semiconductor bandgap wavelength can allow to get rid of direct photoionization and take advantage of deeper in-volume nonlinear absorption processes. Equally, it is known that higher electron temperature can be reached by increasing the laser wavelength of because the increased electron temperature effect of tunnel ionization, free-carrier absorption and impact ionization all scale with the square of the laser wavelength. Although nonlinear absorption can be convenient in some embodiments, the methods and systems describe herein can include linear absorption of the corrective laser beam as well. T

[0073] It is understood that the photonic chip described above can be provided in a plethora of different, and yet advantageous, embodiments. The following paragraphs are meant to present only a few examples of how the non-guiding structures disclosed therein can be declined.

[0074] For instance, Figs. 6A and 6B show photonic chips 10 incorporating a guiding structure 12 provided in the form of a Y-combiner, in accordance with two different embodiments. More specifically, Fig. 6A shows a photonic chip 10 having a guiding structure 12, a cladding matrix 14 surrounding the guiding structure 12, and a non-guiding structure 16 spaced-apart from the guiding structure 12. In this example, the guiding structure 12 includes an input port, a coupling region optically coupled to the input port, and output ports optically coupled to the coupling region. During use of this photonic chip 10, it is intended that an optical mode propagating along the input port can be propagated into corresponding ones of the output ports, thereby spatially, power and / or polarization splitting the initial optical mode in two portions. In this embodiment, the non-guiding structure 16 is provided in the form of elongated structures 16’ and 16” that are spaced apart from the output ports and running alongside the output ports. More specifically, each output port has first and second elongated structures 16’ and 16” that are located on different lateral sides of the corresponding output port. In some embodiments, the elongated structures 16’ of the first output port can be laser-induceddifferently from the elongated structures 16” of the second output port, thereby creating an asymmetry in the coupling. Depending on the embodiment, the purpose of such laser-induced permanent structural changes can be to reach an asymmetric coupler or ensure that the coupling is symmetric between the two output ports. As shown in this embodiment, the elongated structures 16’ located outwardly from the two output ports have a length that extend from the coupling region, whereas the elongated structures 16” located inwardly from the two output ports extends from a more downstream portion of the output ports. Although this embodiment has been shown to be satisfactory in some embodiments, other constructions of the non-guiding structure 16 can be used in some other embodiments. Fig. 6B shows a similar photonic chip 10. However, in this very example, the elongated structures 16’ of the nonguiding structure 16 are positioned proximate to the coupling region of the Y-combiner instead of proximate the output ports of the Y-combiner.

[0075] Fig. 7 shows a photonic chip 10 having a guiding structure 12 provided in the form of a directional coupler, a cladding matrix 14 surrounding the guiding structure 12, and a nonguiding structure 16 spaced-apart from the guiding structure 12. In this example, the guiding structure 12 includes first and second input ports, a coupling region optically coupled to the input ports, and first and second output ports optically coupled to the coupling region. In this specific example, the non-guiding structure 16 is provided in the form of an elongated structure 16’ that is laterally spaced apart from the coupling region, between the first input port and the first output port. In this specific embodiment, a guiding structure protector 50 obstructs the corrective laser beam from reaching the second input port, a portion of the coupling region and the second output port. Accordingly, the corrective laser beam, or a focal point thereof, can be big enough to encompass all of the guiding structure 12 without necessarily affecting or creating local refractive index changes behind the guiding structure protector 50. However, in some embodiments, while the corrective laser beam can induce at least some refractive index change in the guiding structure 12, the guiding structure protector 50 can prevent the underlying guiding structure 12 to be damaged or otherwise modified. In this embodiment, the corrective laser beam is meant to be propagating across the page, therefore the guiding structure protector 50 is located between the guiding structure 12 and a top surface of the photonic chip 10. For instance, the guiding structure protector 50 may extend within the cladding matrix 14 or on a top surface of the photonic chip 10. Although the guiding structureprotector 50 is shown to have a relatively simple rectangular shape in this embodiment, other embodiments of the guiding structure protector 50 can be sized and shape to cover one or more small or bigger portions of the guiding structure 12 in some other embodiments.

[0076] Fig. 8 shows a photonic chip 10 having a guiding structure 12 provided in the form of an arrayed waveguide grating (AWG), a cladding matrix 14 surrounding the AWG, and a non-guiding structure 16 spaced-apart from the guiding structure 12. In this example, the guiding structure 12 includes a first star coupler having a coupling region, and a number of output ports leading to corresponding semiconductor waveguides 12’. A second star coupler is also provided to optically couple the corresponding semiconductor waveguides 12’ back to one another into a coupling region of the second star coupler. As shown in this embodiment, the non-guiding structure 16 includes a corresponding number of elongated structures 16’ spaced apart from but proximate to the semiconductor waveguides 12’. More specifically, the shapes of the non-guiding structures 16’ substantially match the shapes of the semiconductor waveguides 12’, although they are slightly spaced apart from one another. The non-guiding structure 16 may be modified similarly to one another or differently from one another, depending on the refractive index modifications to be achieved.

[0077] Fig. 9 shows a photonic chip 10 having a guiding structure 12, a cladding matrix 14 surrounding the guiding structure 12, and a non-guiding structure 16 spaced-apart from the guiding structure 12. In this example, the guiding structure 12 includes a number of semiconductor waveguides 12’ extending in an array format within the cladding matrix 14. In this embodiment, the semiconductor waveguides 12’ act as the guiding structure 12 as it can guide modes of bigger dimensions. As show, the non-guiding structure 16 is provided in the form of a sheet-like member extending within the cladding matrix 14, between the substrate 11 and the semiconductor waveguides 12’. In this example, the permanent structural changes 20 induced within the non-guiding structure 16 by way of a corrective laser beam can have different effects on the propagation of optical modes along the semiconductor waveguides 12’. For instance, the permanent structural change 20 can modify the effective refractive indexes of the mode guided by the array of semiconductor waveguides 12’. In this example, the guiding structure 12 is spaced apart by about 200 nm from the non-guiding structure 16. However, any spacing preventing optical energy to propagate within the sheet-like member can besufficient. In any case, the thickness of the non-guiding structure 16 can be so narrow, e.g., about 80 nm, that optical mode would likely not propagate therewithin.

[0078] Fig. 10 shows a photonic chip 10 having a guiding structure 12, a cladding matrix 14 surrounding the guiding structure 12, and a non-guiding structure 16 spaced-apart from the guiding structure 12. In this example, the non-guiding structure 16 lies within the cladding matrix 14, and extends between the guiding structure 12 and the substrate 11 . In this specific example, the non-guiding structure 16 is sized and shaped so as to prevent propagation of an optical mode therein. More specifically, the non-guiding structure 16 has a lateral width that is smaller than a critical dimension of the optical mode to be propagated within the guiding structure 12, which prevents any optical mode propagation within the non-guiding structure 16. Moreover, the non-guiding structure 16 has vertexes and sharp edges which when blasted by the corrective laser beam can create significant cracks and the like to maximize the amount and importance of the laser-induced permanent structural changes 20 and associated refractive index changes. Accordingly, it was found that such a configuration can ensure that the non-guiding structure 16 has a damage threshold lower than a damage threshold of the guiding structure 12 so as to affect the non-guiding structure 16 without necessarily affecting the guiding structure 12. As shown in this example, the non-guiding structure 16 has dimensions (e.g., width, height) which are too small to allow guiding of an optical mode therewithin. Even though the dimensions of the non-guiding structure 16 are small, the sharp edges and vertices may efficiently propagate strain.

[0079] Fig. 1 1 shows a photonic chip 10 having a guiding structure 12, a cladding matrix surrounding the guiding structure 12, and a non-guiding structure 16 spaced-apart from the guiding structure 12. In this example, the guiding structure 12 and the non-guiding structure 16 are part of a common greater structure extending within the cladding matrix. As shown, the greater structure has a central portion which acts as the guiding structure 12, and lateral portions which act as non-guiding structures 16. As depicted, the guiding structure 12 and the non-guiding structure 16 are made of a similar material. The guiding structure 12 and the nonguiding structure 16 may even be made integral to one another. In this specific embodiment, the photonic chip 10 is provided with a guiding structure protector 50 which lies within the cladding matrix in this embodiment. As shown, the guiding structure protector 50 is positionedso as to prevent the corrective laser beam to modify the morphology of the guiding structure 12 while exposing the non-guiding structure 16 to a corrective laser beam. In these embodiments, the corrective laser beam may be shined onto the whole photonic chip 10, or a portion thereof, along a direction 51 such as illustrated in Fig. 11 , in a way which can both create the desired permanent structural changes 20 in the non-guiding structure 16 while protecting the guiding structure 12 from actual structural changes. In some embodiments, the guiding structure protector 50 can be made of metal. Examples of such metal can include, but are not limited to, gold, silver, copper, aluminum, titanium, tungsten, and the like. The guiding structure protector 50 can have a dimension M exceeding a dimension d of the guiding structure 12. The lateral wings ofthe non-guiding structure 16 can have a dimension Wgreater than 2 pm, 5 pm or 10 pm, for instance.

[0080] Figs. 12A through 12E show different examples of photonic chips 10 incorporating guiding structures 12 and non-guiding structures 16 having pointy members 17. As depicted, these pointy members 17 are meant to increase the odds of a permanent structural change (e.g., stress, crack) originating from the pointy members 17, as mechanical stress is generally known to do. It is encompassed that depending on the size and shape of the pointy members 17, a corresponding permanent structural change can be obtained, which can in turn help tune the amount of change to the effective refractive index.

[0081] For instance, Fig. 12A shows a photonic chip 10 having a guiding structure 12 provided in the form of a rib waveguide. As shown, the non-guiding structure 16 includes a number of pointy members 17 spaced apart from one another along a length of the guiding structure 12. The pointy members 17 have tips facing the guiding structure 12. In this embodiment, it is intended that upon shining of the corrective laser beam, cracks (or any other types of permanent structural changes) can be created at the tips, which encourage the mechanical propagation of the cracks towards the guiding structure 12 through the cladding matrix.

[0082] Fig. 12B shows a photonic chip 10 having a guiding structure 12 provided in the form of a ring resonator. As depicted, the non-guiding structure 16 includes inner and outer annular members located inwardly and outwardly ofthe ring, respectively. In this specific embodiment, the inner and outer annular members are jigsaw patterned and as such provide a significantnumber of pointy members 17 facing the ring of the guiding structure. It is intended that when processed by a corrective laser beam, the non-guiding structure 16 can provide permanent structural changes that are proportional to the amount of point ends of the non-guiding structure 16. Fig. 12C shows another example of a ring resonator where only an inner annular member having pointy members 17 is provided.

[0083] Fig. 12D shows a photonic chip 10 having a guiding structure 12 provided in the form of a Mach-Zehnder interferometer having first and second arms. As depicted, the non-guiding structure 16 has a first portion extending outwardly from the first arm and a second portion extending inwardly from the first arm. The first and second portion of the non-guiding structure 16 may be sized and shaped differently depending on the amount and importance of the desired permanent structural changes to be laser-induced on the first arm of the Mach- Zehnder interferometer. More specifically, in this embodiment, the first portion has a width extending along a significant portion of the first arm, and a depth that is relatively large relative to the dimension of the first arm. The second portion has a number of segments spatially spaced from one another. These portions can have rectangular shapes as shown, in which case vertices act as the pointy members 17. The spacing of these segments prevent propagation of an optical mode therein, in addition to enhancing the number of permanent mechanical changes to be made nearthe first arm. The non-guiding structure 16 also has third and fourth portions extending inwardly and outwardly from the second arm of the Mach- Zehnder interferometer. As shown, the size and shape of the third and fourth portions of the non-guiding structure 16 is similar to one another in this specific embodiment. It is noted that, in some other embodiments, the first, second, third and fourth portions of the non-guiding structure can be sized and shaped similarly to one another. For instance, Fig. 12E shows an example where the first, second, third and fourth portions of the non-guiding structure all include pointy members 17 having different sizes and shapes, thereby creating different, corresponding refractive index changes on the neighboring guiding structure 12.

[0084] It is noted that the controller discussed above with reference to Fig. 1 can be provided as a combination of hardware and software components. The hardware components can be implemented in the form of a computing device 1300, an example of which is described with reference to Fig. 13. Moreover, the software components of the controller can beimplemented in the form of a software application performing some or more steps of a method of modifying a photonic chip or a method of testing a photonic chip.

[0085] Still referring to Fig. 13, the computing device 1300 can have a processor 1302, a memory 1304, and I / O interface 106. Instructions 1308 for performing the methods 400 or 900 described above can be stored on the memory 1304 and accessible by the processor 1302.

[0086] The processor 1302 can be, for example, a general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, a programmable read-only memory (PROM), or any combination thereof.

[0087] The memory 1304 can include a suitable combination of any type of computer- readable memory that is located either internally or externally such as, for example, randomaccess memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable readonly memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like.

[0088] Each I / O interface 1306 enables the computing device 1300 to interconnect with one or more input devices, such as a photonic chip testing apparatus, detector(s), a computer vision system, or with one or more output devices such as a multi-axis movement stage, an external network or an accessible memory system.

[0089] Each I / O interface 1306 enables the controller to communicate with other components, to exchange data with other components, to access and connect to network resources, to server applications, and perform other computing applications by connecting to a network (or multiple networks) capable of carrying data including the Internet, Ethernet, plain old telephone service (POTS) line, public switch telephone network (PSTN), integrated services digital network (ISDN), digital subscriber line (DSL), coaxial cable, fiber optics, satellite, mobile, wireless (e.g. Wi-Fi, WiMAX), SS7 signaling network, fixed line, local area network, wide area network, and others, including any combination of these.

[0090] The controller can run one or more software applications configured to operate the system described herein using instructions 1308. In some embodiments, the software applications are stored on the memory 1304 and accessible by the processor 1302 of the computing device 1300. The computing device 1300 and the software applications described above are meant to be examples only. Other suitable embodiments of the controller 1332 can also be provided, as it will be apparent to the skilled reader.

[0091] As can be understood, the examples described above and illustrated are intended to be exemplary only. For instance, although the non-guiding structure is said to be “nonguiding,” the non-guiding structure may be able to guide an optical mode before a laser- induced permanent structural change is made within the non-guiding structure. In otherwords, the non-guiding structure is always non-guiding only after its laser modification. For instance, the methods and systems described herein can be performed using more than one corrective laser beam. It is noted that a photonic chip can have a multitude of photonic functions and / or photonic components each having dedicated channels. The methods and systems described here can be applied to each of the photonic functions, each of the photonic components and each of the photonic channels of the photonic chip. Depending on the embodiment, the characteristics of the corrective laser beam can be varied. Examples of such characteristics can include, but are not limited to, pulse duration, repetition rate, burst mode or not, pulse energy, laser wavelength, laser intensity, beam shape (e.g., Gaussian, top-edge, Bessel, elliptical), fixed or moving beam, scan speed, hatch and laser path, to name a few examples. The number and / or locations of the laser taps can depend based on a geometry and material of the non-guiding structure. Moreover, the methods and systems described herein can be adapted to limit losses incurred to the photonic chip, to ensure precise positioning of the corrective laser beam relative to the photonic chip, to maximize a compensation range and to impart positive or negative refractive index changes. When the guiding structure is surrounded by many layers of material (e.g., glass insulator, other semiconductor layers), the effective refractive index change can be selective to the particular layer. Refractive index can be changed by different processes including, but not limited to, amorphization, stress induced, void creation, densification and the like. The laser-induced refractive index modification can be paired with other sources of heating, e.g., thermal heater(s), sources(s) of ionization (e.g., input voltage in the non-guiding structure) or another laser beam absorbed by the non-guidingstructure, to optimize the methods and systems described herein. The corrective laser beam can be perpendicular to a plane of the photonic chip or have an acute or obtuse angle with respect to a plane of the photonic chip. Structures such as fiber-Bragg gratings or polarisers can be created with the effective refractive index change inside the non-guiding structure in some embodiments. It is understood that modifying the effective refractive index can include a modification of the real part of the refractive index, a modification of the imaginary part of the refractive index, or a combination thereof. In some embodiments, the central wavelength of the corrective laser beam can be adapted to control the process parameters and optimize correction depending on the type of semiconductor material. In some embodiments, the refractive index modifications can be imparted in such a way that can influence the polarization of the optical signal propagating along one or more semiconductors of the guiding structure. For instance, the refractive index modifications can extend on opposite sides of the guiding structure to maintain or change polarization. In one specific embodiment, refractive index modifications such as those shown described herein can be used to mimic the structure of polarization-maintaining optical fibers, to name only one example. In embodiments where the photonic chip is based on the InP semiconductor platform, such refractive index modifications can form matrix defects which can attract electrons and thereby reduce optical losses occurring along the guiding structure. Although the guiding structure shown in the example above is rather simple and unidimensional, complex structures for the guiding and / or nonguiding structures can be used in some other embodiments. For instance, the guiding structure can include one or more guiding structures running alongside each other, and the cladding matrix (e.g., glass matrix) extending between them. The scope is indicated by the appended claims.

Claims

WHAT IS CLAIMED IS:1 . A method of modifying a photonic chip having a guiding structure and a cladding matrix surrounding the guiding structure, the guiding structure and the cladding matrix configured for guiding an optical mode within the photonic chip, the method comprising: directing a corrective laser beam within a non-guiding structure of the photonic chip, the non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the non-guiding structure having a material different from a material of the cladding matrix, said directing creating a permanent structural change within the non-guiding structure, the permanent structural change spatially extending into the cladding matrix between the nonguiding structure and the guiding structure, the permanent structural change permanently modifying an effective refractive index of the guiding structure; performing a testing routine on the photonic chip including determining a parameter indicative of a performance of the guiding structure; and upon determining that the parameter mismatches a reference parameter associated with a reference photonic chip, repeating said directing and said testing routine until the parameter matches the reference parameter within a given tolerance.

2. The method of claim 1 wherein the permanent structure change includes one or more cracks running within the cladding matrix between the non-guiding structure and the guiding structure.

3. The method of claim 2 wherein the one or more cracks originate from one or more corresponding apexes or edges of the non-guiding structure.

4. The method of any one of claims 1 to 3 wherein the non-guiding structure extends within the cladding matrix at least one of below, above and on a lateral side of the guiding structure.

5. The method of any one of claims 1 to 4 wherein the non-guiding structure has a body and one or more pointy members protruding from the body and facing the guiding structure through the cladding matrix, the permanent structure change extending from one or more pointy members towards the guiding structure.

6. The method of claim 5 wherein the one or more pointy members are two-dimensional pointy members, the two-dimensional pointy members extending in a plane one of parallel with a plane of the photonic chip and perpendicular to the guiding structure.

7. The method of any one of claims 1 to 6 wherein the non-guiding structure is a first nonguiding structure, the permanent structural change is a first permanent structural change, the method further comprising: directing the corrective laser beam within a second nonguiding structure of the photonic chip, the second non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the second non-guiding structure having a material different from a material of the cladding matrix, said directing creating a second permanent structural change within the non-guiding structure, the second permanent structural change spatially extending into the cladding matrix between the second non-guiding structure and the guiding structure, the permanent stress permanently further modifying the effective refractive index of the guiding structure.

8. The method of any one of claims 1 to 7 wherein the non-guiding structure has a shape closely matching a shape of the guiding structure.

9. The method of any one of claims 1 to 8 wherein the non-guiding structure includes at least one of: a semiconductor material, a metallic material, a glass material, and a polymer material.

10. The method of any one of claims 1 to 9 wherein the guiding structure includes a semiconductor material.1 1 . The method of any one of claims 1 to 10 wherein the material of the non-guiding structure is a semiconductor material having a bandgap wavelength, the corrective laser beam having a central wavelength below the bandgap wavelength of the semiconductor material of the non-guiding structure.

12. The method of any one of claims 1 to 11 wherein said directing includes moving at least one of the corrective laser beam and the photonic chip along a path.

13. The method of any one of claims 1 to 12 wherein said testing routine includes guiding a test optical signal into and along the guiding structure, detecting an output signal resulting from said guiding and determining the parameter based on said output signal.

14. The method of any one of claims 1 to 13 further comprising, using a guiding structure protector extending at least one of within the cladding matrix and on a top surface of the cladding matrix, obstructing at least a portion of the corrective laser beam and protecting at least a portion of the guiding structure from the corrective laser beam.

15. A photonic chip comprising: a guiding structure; a cladding matrix surrounding the guiding structure, the guiding structure and the cladding matrix configured for guiding an optical mode within the photonic chip; and a non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the non-guiding structure having a material different from a material ofthe cladding matrix, said non-guiding structure having a laser- induced permanent structural change within the non-guiding structure, the laser-induced permanent structural change spatially extending into the cladding matrix between the non-guiding structure and the guiding structure, the permanent structural change permanently modifying an effective refractive index of the guiding structure.

16. The photonic chip of claim 15 wherein the permanent structure change includes one or more cracks running within the cladding matrix between the non-guiding structure and the guiding structure.

17. The photonic chip of claim 16 wherein the one or more cracks originate from one or more corresponding apexes or edges of the non-guiding structure.

18. The photonic chip of any one of claims 15 to 17 wherein the non-guiding structure extends within the cladding matrix at least one of: below, above and on a lateral side of the guiding structure.

19. The photonic chip of any one of claims 15 to 18 wherein the non-guiding structure has a body and one or more pointy members protruding from the body and facing the guidingstructure through the cladding matrix, the permanent structure change extending from one or more pointy members towards the guiding structure.

20. The photonic chip of any one of claims 15 to 19 wherein the non-guiding structure has a shape closely matching a shape of the guiding structure.

21. The photonic chip of any one of claims 15 to 20 further comprising a guiding structure protector extending at least one of within the cladding matrix and on a top surface of the cladding matrix, the guiding structure protector made of a material non-transparent to a corrective laser beam.

22. A system for modifying a photonic chip having a guiding structure and a cladding matrix surrounding the guiding structure, the guiding structure and the cladding matrix configured for guiding an optical mode within the photonic chip, the system comprising: a corrective laser apparatus configured for directing a corrective laser beam within a portion of a non-guiding structure of the photonic chip, the non-guiding structure spaced-apart from the guiding structure and the optical mode propagating therealong, the non-guiding structure having a material different from a material of the cladding matrix, said directing creating a permanent structural change within the non-guiding structure, the permanent structural change spatially extending into the cladding matrix between the non-guiding structure and the guiding structure, the permanent structural change permanently modifying an effective refractive index of the guiding structure; a photonic chip testing apparatus performing a testing routine on the guiding structure including determining a parameter indicative of a performance of the guiding structure; and a controller communicatively coupled to the corrective laser apparatus and to the photonic chip testing apparatus, the controller having a processor and a memory having stored thereon instructions that when executed by the processor perform the steps of: comparing the parameter to a reference parameter associated with a reference photonic chip; andupon determining that the parameter mismatches the reference parameter, repeating said directing and said testing routine until the parameter matches the reference parameter within a given tolerance.

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