Method and system for modifying photonic chip having semiconductor waveguide

Abstract

A method of modifying a photonic chip having a semiconductor waveguide is described. The method generally has directing a focus of a correction laser beam into a portion of the photonic chip, the portion being one of a portion proximate to the semiconductor waveguide and a portion within the semiconductor waveguide, the correction laser beam having a center wavelength greater than a bandgap wavelength of the semiconductor waveguide, the guide modifies an effective refractive index of a portion of the semiconductor waveguide; performing a test routine on the semiconductor waveguide, including determining a parameter indicative of a performance of the semiconductor waveguide; and upon determining that the parameter does not match a reference parameter associated with a reference photonic chip, repeating the steering and the test routine until the parameter matches the reference parameter within a given tolerance.

Description

Technical Field

[0001] These improvements relate generally to photonic chips and, more particularly, to the fabrication and testing of such photonic chips. Background Art

[0002] Photonic chips process light signals in a similar way that electronic chips process electronic signals. Photonic chips are typically manufactured using foundry processes used for microelectronics manufacturing. Microelectronic foundry processes can achieve tolerances of about 1.5nm at best, and while this is satisfactory for state-of-the-art microelectronics, it may not be sufficient for photonic chip manufacturing. Therefore, each photonic chip manufactured using a known foundry process is rigorously inspected and tested to ensure that it meets the design specifications. Once a photonic chip is identified as defective, it is discarded, which can result in significant losses in materials and time. Although existing technologies for manufacturing photonic chips are satisfactory to a certain extent, there is still room for improvement. Summary of the invention

[0003] Methods and systems configured for modifying photonic chips and in particular defective photonic chips that have been identified as not meeting (one or more) design tolerances and / or (one or more) performance parameters based on individual inspection and testing are described. The methods and systems involve a test routine in which (one or more) parameters indicative of the performance of (one or more) semiconductor waveguides of the photonic chip are measured and, in some cases, monitored over time. Examples of such parameters may include, but are not limited to, wavelength, phase, amplitude, polarization, dispersion, gain and / or loss, etc., to name a few examples. A correction laser beam selected to exhibit a central wavelength greater than the bandgap wavelength of the (one or more) semiconductor waveguides is then used to perform (one or more) local modifications of the effective refractive index of (one or more) semiconductor waveguides. Such (one or more) local modifications may be performed iteratively until the monitored parameters match the corresponding reference parameters of a reference photonic chip. Notably, since the semiconductor waveguides are optically transparent to the correction laser beam, their focus may be directed through the photonic chip, such as through its cladding or substrate. When the focus of the correction laser beam transmits sufficient optical energy in a local portion of the (one or more) semiconductor waveguides, a local volumetric refractive index modification may be created. In at least some examples, these localized volume material modifications can result in adjusting the performance of a defective photonic chip to a level at which the photonic chip can become defect-free.

[0004] According to a first aspect of the present invention, there is provided a method for modifying a photonic chip having a semiconductor waveguide, the semiconductor waveguide having a bandgap wavelength, the method comprising: directing a focus of a correction laser beam into a portion of the photonic chip, the portion being one of a portion close to the semiconductor waveguide and a portion within the semiconductor waveguide, the correction laser beam having a central wavelength greater than the bandgap wavelength of the semiconductor waveguide, the directing modifying the effective refractive index of the portion of the semiconductor waveguide; performing a test routine on the semiconductor waveguide, the test routine comprising determining a parameter indicative of performance of the semiconductor waveguide; and when it is determined that the parameter does not match a reference parameter associated with a reference photonic chip, repeating the directing and the test routine until the parameter matches the reference parameter within a given tolerance.

[0005] Further, according to the first aspect of the present disclosure, directing may, for example, include moving at least one of a focus of the correction laser beam and the photonic chip along a path.

[0006] Still further, according to the first aspect of the present disclosure, the moving may, for example, include transmitting a laser pulse at each of a plurality of spaced-apart points distributed along the path.

[0007] Furthermore, according to the first aspect of the invention, the test routine may, for example, include directing a test light signal into and along the semiconductor waveguide, detecting an output signal resulting from the directing and determining a parameter based on the output signal.

[0008] Furthermore, according to the first aspect of the present invention, the directing may, for example, include injecting a test optical signal into the first end of the semiconductor waveguide.

[0009] Still further, according to the first aspect of the invention, detecting may, for example, comprise measuring the output signal using a photodiode optically coupled to the second end of the semiconductor waveguide.

[0010] Furthermore, according to the first aspect of the invention, the detecting may, for example, comprise measuring an output signal scattered from the semiconductor waveguide using a camera during redirection.

[0011] Furthermore, according to the first aspect of the present invention, the parameter may be, for example, at least one of an output wavelength, an output phase, an output amplitude, an output polarization, an output dispersion and an output loss.

[0012] Furthermore, according to the first aspect of the present invention, the central wavelength of the correction laser beam may be, for example, between about 1 μm and about 20 μm, preferably between about 1.2 μm and about 10 μm, and most preferably between about 1.5 μm and about 4 μm.

[0013] Furthermore, according to the first aspect of the invention, the correction laser beam may, for example, have laser pulses having a duration 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.

[0014] Furthermore, according to the first aspect of the present invention, the semiconductor waveguide may, for example, be placed relative to the substrate, the photonic chip may, for example, also have a cladding covering the top surface of the substrate and the semiconductor waveguide, and the guiding may, for example, include guiding the focus of the correction laser beam through at least one of the cladding and the substrate.

[0015] Furthermore, according to the first aspect of the present invention, the photonic chip may, for example, have a plurality of semiconductor waveguides, each semiconductor waveguide having a bandgap wavelength, and the method may, for example, include performing the guiding and testing routines for each of the plurality of semiconductor waveguides until a plurality of parameters associated with the plurality of semiconductor waveguides match corresponding reference parameters within a given tolerance.

[0016] According to a second aspect of the present invention, there is provided a system for modifying a photonic chip having a semiconductor waveguide, the semiconductor waveguide having a bandgap wavelength, the system comprising: an equipment correction laser device, the equipment correction laser device being configured to direct the focus of a correction laser beam into a portion of the photonic chip, the portion being one of a portion close to the semiconductor waveguide and a portion within the semiconductor waveguide, the correction laser beam having a central wavelength greater than the bandgap wavelength of the semiconductor waveguide, the directing modifying the effective refractive index of the semiconductor waveguide; a photonic chip testing device, the photonic chip testing device performing a test routine on the semiconductor waveguide, the test routine comprising determining parameters indicative of performance of the semiconductor waveguide; and a controller, the controller being communicatively coupled to the equipment correction laser device and the photonic chip testing device, the controller having a processor and a memory, the memory having instructions stored thereon, and when the processor executes the instructions, performing the following steps: comparing the parameters with reference parameters associated with a reference photonic chip; and when it is determined that the parameters do not match the reference parameters, repeating the directing and the test routine until the parameters match the reference parameters within a given tolerance.

[0017] Further, according to the second aspect of the present disclosure, the correction laser device may, for example, include a laser source that generates a correction laser beam, the central wavelength range being between about 1.0 μm and about 20 μm, preferably between about 2.5 μm and about 10 μm, and most preferably between about 2.8 μm and about 3.4 μm.

[0018] Still further, according to the second aspect of the present disclosure, the correction laser device may, for example, include a laser source that generates laser pulses having a duration 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.

[0019] Furthermore, according to the second aspect of the present invention, the calibration laser device may have, for example, a fiber laser source.

[0020] Furthermore, according to the second aspect of the present disclosure, the system may further include, for example, a multi-axis moving stage having a support area on which the photonic chip is accommodated, and the multi-axis moving stage may, for example, move the photonic chip during guiding.

[0021] Furthermore, according to the second aspect of the present invention, the photonic chip testing device may, for example, include: a test light source, which directs the test light signal into and along the semiconductor waveguide; and a detector, which detects the output signal caused by the guidance, and the controller may, for example, determine parameters based on the output signal.

[0022] Furthermore, according to the second aspect of the present disclosure, the detector may be, for example, a photodiode optically coupled to the first end of the semiconductor waveguide, for detecting the output signal.

[0023] Furthermore, according to the second aspect of the present invention, the detector may be, for example, an infrared camera that measures the output signal scattered from the semiconductor waveguide during the directing period.

[0024] According to a third aspect of the present invention, a method for testing a photonic chip is provided, wherein the photonic chip has a semiconductor waveguide and a plurality of semiconductor elements optically coupled to the semiconductor waveguide, wherein the semiconductor elements have a bandgap wavelength, the method comprising: when performing a test routine on the semiconductor waveguide, the test routine comprises directing a test optical signal into and along the semiconductor waveguide, detecting an output signal caused by the directing and monitoring an output signal based on the output signal, directing a focus of a detection laser beam into a portion of the photonic chip, the portion being one of a portion close to one of the plurality of semiconductor elements and a portion within the one of the semiconductor elements, a correction laser beam having a central wavelength greater than the bandgap wavelength of the semiconductor element, the directing modifying an effective refractive index of the portion of the one of the semiconductor elements; identifying optical features in an output spectrum modified in response to the directing; and associating the optical features with the one of the semiconductor elements.

[0025] Further, according to the third aspect of the present disclosure, the modification may, for example, include modifying the effective refractive index of the portion of the semiconductor waveguide by an amount between about 0.1 and about 0.00000001, preferably between about 0.05 and about 0.0005, and most preferably between about 0.01 and about 0.001.

[0026] According to a fourth aspect of the present invention, there is provided a system for testing a photonic chip, wherein the photonic chip has a semiconductor waveguide and a plurality of semiconductor elements optically coupled to the semiconductor waveguide, the semiconductor elements having a bandgap wavelength, the system comprising: a photonic chip testing device, which performs a test routine, comprising directing a test optical signal into and along the semiconductor waveguide, detecting an output signal caused by the directing, and monitoring an output spectrum based on the output signal; a correction laser device, which is configured to direct the focus of a correction laser beam into a portion of the photonic chip, the portion being one of a portion close to one of the plurality of semiconductor elements and a portion within the one of the semiconductor elements, the correction laser beam having a central wavelength greater than the bandgap wavelength of the semiconductor waveguide, the directing modifying the effective refractive index of the portion of the one of the semiconductor elements; and a controller, which is communicatively coupled to the photonic chip testing device and the correction laser device, the controller having a processor and a memory, the memory having instructions stored thereon, and when the processor executes the instructions, the following steps are performed: identifying an optical feature in the output spectrum that is modified in response to the directing; and associating the optical feature with the one of the semiconductor elements.

[0027] All technical implementation details and advantages described for certain aspects of the present disclosure are obviously applicable mutatis mutandis to all other aspects of the present disclosure.

[0028] It is worth noting that the expression "close to the semiconductor waveguide" means any location outside the semiconductor waveguide including the photonic chip, which can affect the effective refractive index of the semiconductor waveguide when modified using the focus of the correction laser beam. For example, in some embodiments, such a location may include a material matrix surrounding the semiconductor waveguide, a substrate on which the semiconductor waveguide is located, or a substrate on which it is suspended.

[0029] After reading this disclosure, those skilled in the art will recognize many further features and combinations thereof relating to the present improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the figure,

[0031] Figure 1 is a schematic diagram of an example of a system for modifying a photonic chip having a semiconductor waveguide according to one or more embodiments;

[0032] Figure 2 is an illustration according to one or more embodiments Figure 1 A diagram of an optical transmission window of a semiconductor waveguide and a central wavelength of a corrected laser beam;

[0033] Figure 3A According to one or more embodiments Figure 1 An oblique view of a photonic chip on which a test routine is being performed and showing a measured parameter mismatch;

[0034] Figure 3B A method for receiving a correction laser beam in a semiconductor waveguide according to one or more embodiments Figure 1 An oblique view of the photonic chip;

[0035] Figure 3C According to one or more embodiments Figure 1 An oblique view of a photonic chip on which a subsequent test routine is being performed and showing that the measured parameters match;

[0036] Figure 4 is a flow chart of an example of a method for modifying a photonic chip having a semiconductor waveguide according to one or more embodiments;

[0037] FIG. 5A to FIG. 5D is a top view of an exemplary semiconductor waveguide forming various photonic elements according to one or more embodiments, showing a correction laser beam being directed to a plurality of locations relative to the semiconductor waveguide;

[0038] FIG. 6A to FIG. 6D is a top view of an exemplary semiconductor waveguide of a given photonic element according to one or more embodiments, showing movement of a correction laser beam along different modes relative to the semiconductor waveguide;

[0039] Fig. 6E is a top view of an example of a semiconductor waveguide according to one or more embodiments, showing correction laser beams of different intensities directed to different positions relative to the semiconductor waveguide;

[0040] Fig. 6F is a top view of an example of a semiconductor waveguide according to one or more embodiments, showing correction laser beams of different central wavelengths being directed to different positions relative to the semiconductor waveguide;

[0041] Figure 6G is a top view of an example of a semiconductor waveguide according to one or more embodiments, showing correction laser beams of different spatial modes being directed to the semiconductor waveguide;

[0042] Fig. 7A is a side view of an example photonic chip according to one or more embodiments, showing a correction laser beam being directed through an upper cladding layer to a semiconductor waveguide;

[0043] Figure 7B is a side view of an example photonic chip showing a correction laser beam directed through a substrate to a semiconductor waveguide according to one or more embodiments;

[0044] Figure 8 is a side view of an example of a photonic chip modified by a correction laser beam according to one or more embodiments, showing the size of the correction laser beam and the size of the semiconductor waveguide;

[0045] Fig. 9 is a flow chart of an example of a method for testing a photonic chip having semiconductor elements according to one or more embodiments;

[0046] Fig.10 is a top view of an example of a photonic chip having semiconductor elements according to one or more embodiments;

[0047] Fig.11A is a top view of an example of a Mach-Zehnder interferometer arm having a semiconductor waveguide and refractive index modification performed thereabout according to one or more embodiments;

[0048] Fig. 11B FIG. 1 is a diagram showing the effect of different refractive index modification amounts on the Fig.11A A diagram showing fine tuning of the refractive index of a semiconductor waveguide;

[0049] Fig. 12A is a top view of an example of a Mach-Zehnder interferometer arm having a semiconductor waveguide and refractive index modification performed within the semiconductor waveguide according to one or more embodiments;

[0050] Fig. 12B FIG. 1 is a diagram showing the effect of different refractive index modifications on a semiconductor waveguide according to one or more embodiments. Fig. 12A A diagram showing a rough adjustment of the refractive index of a semiconductor waveguide;

[0051] Fig.13A is a graph showing post-fabrication spectral responses for different semiconductor elements each comprising a Mach-Zehnder interferometer according to one or more embodiments;

[0052] Fig. 13B It is shown Fig.13A a graph of the spectral response of a semiconductor element in after coarse tuning and / or fine tuning using refractive index modification performed within and / or proximate to a corresponding semiconductor waveguide; and

[0053] Fig.14 is a schematic diagram of an example of a computing device of a controller according to one or more embodiments. DETAILED DESCRIPTION

[0054] Figure 1 An example of a system 100 for modifying a photonic chip 10 having a semiconductor waveguide 12 is shown. The system 100 may be used in any testing phase of the manufacture of the photonic chip 10. For example, the system 100 may be used in a design phase where the photonic chip 10 is prototyped and iteratively corrected as needed, in a foundry phase where the photonic chip 10 is mass produced, and / or in a packaging phase where the photonic chip 10 is integrated into a package.

[0055] It is worth noting that the semiconductor waveguide 12 can involve any type of semiconductor material, including but not limited to silicon, silicon nitride (SiN), silicon on insulator (SOI), silicon nitride (Si3N4), 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), indium arsenide (InAs), lead selenide (PbSe), lead sulfide (PbS), chalcogenide-based materials (such as sulfide-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 dots, gas).

[0056] The semiconductor waveguide 12 may be any type of semiconductor waveguide used in a photonic chip. For example, the semiconductor waveguide 12 may be a strip waveguide, a ridge waveguide, a groove waveguide, a photonic crystal waveguide, a subwavelength waveguide grating (SWG) waveguide, a SWG groove waveguide, an SPP groove waveguide, etc. Typically, the photonic chip 10 includes a substrate 14, and the semiconductor waveguide 12 is placed relative to the substrate 14. For example, the semiconductor waveguide 12 may be directly accommodated on the substrate 14, or indirectly accommodated on the substrate, for example, by a buried oxide layer. The substrate 14 may be a silicon substrate, a polymer substrate, a glass substrate, or any other suitable type of substrate. In some embodiments, the semiconductor waveguide 12 is disposed on top of the substrate 14. In these embodiments, the semiconductor waveguide 12 may move along a path substantially parallel to the plane of the substrate 14. Depending on the embodiment, the path may be straight, arc-shaped, circular. In some other embodiments, the semiconductor waveguide 12 may be suspended above the substrate 14 or buried therein. The photonic chip 10 may include one or more cladding or metal layers 16 partially or completely covering the top surface of the semiconductor waveguide 12 and / or substrate 14. In some embodiments, the cladding or metal layer 16 may be made of an oxide. In addition, in some embodiments, there may be a buried oxide layer between the substrate 14 and the semiconductor waveguide 12. In some embodiments, the cladding or metal layer 16 may be made of any material having a lower refractive index than the waveguide material, thereby allowing confinement and propagation of optical signals.

[0057] As shown, the system 100 has a correction laser device 110 and a photonic chip testing device 120. In some embodiments, the system 100 may also include a computer vision device 130 incorporating a camera 132 for real-time imaging of the photonic chip 10. A multi-axis moving stage 140 may be optionally used to move the photonic chip 10 within the working area as needed. The multi-axis moving stage 140 may be a translation stage and / or a rotation stage. In some embodiments, the correction laser device 110 may be integrated with an existing photonic testing device.

[0058] The system 100 may have a controller 150 that may be communicatively coupled to, for example, a calibration laser device 110, a photonic chip testing device 120, a computer vision device 130, and / or a multi-axis translation stage 140. The controller 150 has a processor and a memory having instructions stored thereon, which, when executed by the processor, perform pre-programmed instructions and / or method steps. To this end, the controller 150 typically includes hardware components provided in the form of a computing device and software components provided in the form of a program, algorithm, etc., for performing the method steps. An example of a computing device is described below.

[0059] As depicted, the correction laser device 110, the photonic chip testing device 120, the computer vision device 130, and the multi-axis moving stage 140 can be fixedly or detachably mounted to the frame 102. In this particular embodiment, the frame 102 is provided in the form of an optical bench or an optical bench. However, it can be understood that in some other embodiments, the correction laser device 110, the photonic chip testing device 120, the computer vision device 130, and the multi-axis moving stage 140 can be installed independently of each other at different locations in the photonic chip production line. In some embodiments, the electronic probe and / or the optical fiber probe of the photonic chip testing device 120 can be located in the path of the correction laser beam of the correction laser device 110. In these embodiments, the correction laser device 110, its laser source, or its output can be moved above or below the photonic chip 10 as needed. Such movement can be generated using a two-axis or three-axis galvanometer scanner, a coarse gantry mechanism for movement within a square centimeter, a fine gantry mechanism for movement within a relatively small area (e.g., 100μm×100μm, 10μm×10μm), a piezoelectric micropositioner (e.g., a hexapod robot, a spatial light modulator (SLM)), a fiber optic cable with a microlens tip, a six-degree-of-freedom robotic arm, any other motion device with or without (one or more) moving parts that can translate and / or deflect the correction laser beam, and / or any combination thereof.

[0060] It is worth noting that all semiconductor materials have their own band gap energy and a corresponding band gap wavelength that are linked together by the Planck relation. The band gap energy and the band gap wavelength define at which wavelengths or photon energies the semiconductor material exhibits at least a certain degree of transparency. It is intended to select the correction laser beam to have a central wavelength that is greater than the band gap wavelength of the corresponding semiconductor waveguide. Equivalently, the correction laser beam can have a photon energy that is lower than the band gap energy of the semiconductor waveguide. For example, to name a few examples, the direct band gap of lead selenide (PbSe) is 0.27 eV or 4.57 μm; the direct band gap of lead telluride (PbTe) is 0.32 eV or 3.86 μm; the direct band gap of indium arsenide (InAs) is 0.36 eV or 3.43 μm; the direct band gap of lead sulfide (PbS) is 0.37 eV or 3.34 μm; the indirect band gap of germanium (Ge) is 0.67 eV or 1.84 μm; the direct band gap of gallium antimonide (GaSb) is 0.726 eV or 1.70 μm; the indirect band gap of silicon (Si) is 1.12 eV or 1.1 μm; the direct band gap of indium phosphide (InP) is 1.35 eV or 915 nm; the direct band gap of gallium arsenide (GaAs) is 1.441 eV or 1.84 μm. 857nm; the direct band gap of cadmium telluride (CdTe) is 1.5eV or 823nm; the direct band gap of cadmium selenide (CdSe) is 1.74eV or 710nm; the indirect band gap of aluminum arsenide (AlAs) is 2.12eV or 583nm; the indirect band gap of gallium phosphide (GaP) is 2.24eV or 551nm; the direct band gap of cadmium sulfide (CdS) is 2.42eV or 510nm; the direct band gap of gallium nitride (GaN) is 3.4eV or 363nm; the direct band gap of cubic zinc sulfide (ZnS) is 3.54eV or 349nm; the direct band gap of hexagonal zinc sulfide (ZnS) is 3.91eV or 316nm; the direct band gap of aluminum nitride (AlN) is 6.015eV or 205nm.

[0061] Reference now Figure 2 It is noteworthy that the semiconductor waveguide of the photonic chip has a bandgap energy and a corresponding bandgap wavelength defining a light transmission window 20. The light transmission window 20 can be between about 1 μm and about 25 μm, preferably between about 2.0 μm and about 20 μm, and most preferably between about 2.5 μm and about 10 μm. For example, in an embodiment where the semiconductor waveguide includes silicon having a bandgap wavelength of about 1.1 μm, the light transmission window can be between about 1.1 μm and about 15 μm. In such an embodiment, the center wavelength of the correction laser beam can be selected to be greater than 1.1 μm. For example, a mid-infrared laser beam has been found to be satisfactory. For example, the light transmission window typically exhibits a transmittance between about 1% / cm and about 10% / cm.

[0062] In view of the above, it is desirable that the correction laser beam have a central wavelength 112 extending at least partially or entirely within the optical transmission window 20 of the semiconductor waveguide. For example, the central wavelength 112 of the correction laser beam can be between about 1.0 μm and about 20 μm, preferably between about 2.5 μm and about 10 μm, and most preferably between about 2.8 μm and about 3.4 μm. In this way, optical energy can be transmitted within the photonic chip (e.g., including within and / or near the semiconductor waveguide). In embodiments where the semiconductor includes silicon, it is found convenient to use a mid-infrared laser beam having a narrow spectral bandwidth (or equivalent central wavelength) (e.g., a central wavelength of about 3.2 μm). Notably, a fiber laser source having an optical fiber segment made of a low phonon energy glass and having at least one laser active doping region extending along the optical fiber segment can be used to generate the mid-infrared laser beam. An example of such a fiber laser source is described in U.S. Pat. No. 10,084,287 B2, the contents of which are incorporated herein by reference.

[0063] Figure 3A Shows Figure 1 The photonic chip 10 is a photonic chip on which a test routine is being performed by a photonic chip test equipment 120. As shown in the figure, the photonic chip test equipment 120 determines a parameter P indicative of the performance of the semiconductor waveguide 12. When the measured parameter P is compared with a reference parameter P of a reference photonic chip REF When they do not match each other within a given tolerance TOL, that is, when , the photonic chip 10 may be identified as defective. Rather than discarding the defective photonic chip 10, the system 100 may be used to modify the photonic chip 10. For example, the reference photonic chip may correspond to a photonic chip that is considered to be non-defective or within the design tolerance(s). The reference parameter(s) P REF The parameters P may be stored in a storage system accessible to the controller 150. In some embodiments, each photonic chip under test has an identifier that identifies the type of photonic chip and one or more reference parameters P associated with the photonic chip type. REF When such a photonic chip is being tested, the controller may obtain the photon type and / or the associated reference parameter P REF .

[0064] In some embodiments, the photonic chip testing device 120 has a test light source 122 and a detector 126, the test light source 122 directs a test light signal 124 into and along the first end 12a of the semiconductor waveguide 12, and the detector 126 detects an output signal 128 resulting from the directing of the test light signal 124. The test light signal 124 may be injected using (one or more) grating couplers, (one or more) side couplers, (one or more) free space injection procedures, and the like. To name a few examples, the output light signal 128 may be detected by imaging the scattering from the photonic chip 10 using an integrated photodiode, a fiber optic probe, a free space detector, a spectrophotometer, a standard, infrared, or hyperspectral camera. In these embodiments, the controller may determine the parameter P based on the output signal 128. As Figure 3A As shown in the specific embodiment of the invention, the detector can be a photodiode optically coupled to the second end 12b of the semiconductor waveguide 12 for detecting the output signal 128. In some embodiments, the detector is an infrared camera that measures the output signal scattered from the semiconductor waveguide during the directing test light signal 124. The camera(s) can be part of the computer vision device 130. It is intended that the test routine need not be based solely on optical techniques. For example, in some other embodiments, the test routine involves optical modulation based on radio frequency signals and / or electronic measurements.

[0065] like Figure 3B As shown, the correction laser device 110 is used to direct the focus 114 of the correction laser beam 116 into a portion of the photonic chip 10, which is one or both of the semiconductor waveguide 12 or near the semiconductor waveguide 12. Due to the optical transparency of the semiconductor waveguide 12 to the correction laser beam 116, the effective refractive index of the portion of the semiconductor waveguide 12 can be modified to a certain extent, including a positive or negative refractive index change. The effective refractive index modification can modify the performance of the semiconductor waveguide 12 and the entire photonic chip 10 accordingly.

[0066] like Figure 3C As depicted, the modified photonic chip 10 may be tested again using a test routine to determine whether the measured parameter P is now within a given tolerance TOL with the reference parameter P REF Matching, that is, whether P∈[P REF -TOL;P REF+TOL]. These steps can be iterated repeatedly until a match is found, i.e., until the performance of the photonic chip 10 reaches a level that can be considered defect-free. Once the modified photonic chip 10 passes the test routine, it can be placed back into the photonic chip production line and proceed along the photonic chip production line, thereby reducing the number of photonic chips discarded after failing the test routine. Considering that in some embodiments, 50% to 80% of all photonic chips produced using existing microelectronic foundry technology may be defective, assuming that using the methods and systems described herein, the system 100 can reduce such photonic chip rejection rate by at least 25%, preferably less than at least 50%, and most preferably by at least 75%, compared to conventional manufacturing processes. It is also worth noting that the methods and systems described herein can correct defective photonic chips at a relatively high speed.

[0067] Figure 4 An example of a method 400 for modifying a photonic chip having a semiconductor waveguide is shown. Although the method 400 is a reference Figure 1 Although described with reference to the system 100 and the photonic chip 10, it should be understood that the method 400 may be applied to any photonic chip modifying system using any photonic chip.

[0068] In step 402, a focus 114 of a correction laser beam 116 is directed into a portion of the photonic chip 10 that is proximate to or within a semiconductor waveguide 12. As discussed above, the correction laser beam 116 has a central wavelength 112 that is greater than the bandgap wavelength of the semiconductor waveguide 12. Thus, step 402 modifies the effective refractive index of the portion of the semiconductor waveguide 12. The effective refractive index of the portion of the semiconductor waveguide 12 may be modified by an amount between about 0.1 and about 0.00000001, preferably between about 0.05 and about 0.0005, and most preferably between about 0.01 and about 0.001. It is noteworthy that the effective refractive index may be modified to increase or decrease the current effective refractive index of the semiconductor waveguide 12, depending on the embodiment.

[0069] In step 404, a test routine is performed on the semiconductor waveguide 12. The test routine generally includes the step of determining a parameter P indicative of the performance of the semiconductor waveguide 12. According to the embodiment, the parameter may be an output wavelength, an output phase, an output amplitude, an output polarization, an output dispersion, an output loss, and / or a combination thereof. The parameter P may be determined based on the output signal 128 detected by the detector 126 of the photonic chip test device 120.

[0070] In step 406, after determining the parameter P and the reference parameter P associated with the reference photonic chip, REFIf there is no match, the step 402 of guiding and the step 404 of performing the test routine are iterated repeatedly until the parameter P is within a given tolerance TOL with the reference parameter P REF For example, when a test routine result passes, a pass signal can be generated and the now defect-free photonic chip can be labeled accordingly in the database of the photonic chip production line.

[0071] It is worth noting that in some embodiments, the photonic chip 10 may have a plurality of semiconductor waveguides 12, each of which has a bandgap wavelength. In these embodiments, the method 400 may include performing steps 402 and 404 for each of the semiconductor waveguides 12 until the parameters associated with the semiconductor waveguide 12 match the respective reference parameters within a given tolerance. In some embodiments, the reference parameters for each semiconductor waveguide 12 may be the same. In some other embodiments, each semiconductor waveguide 12 has a dedicated reference parameter.

[0072] In step 408, the step of directing 402 may include the step of moving at least one of the focus 114 of the correction laser beam 116 and the photonic chip 10 along a path. For example, step 408 includes moving the focus 114 of the correction laser beam 116 relative to the semiconductor waveguide 12 of the photonic chip 10. Additionally or alternatively, step 402 includes moving the photonic chip 10 relative to the focus 114 of the correction laser beam 116. In these embodiments, the relative movement between the focus 114 of the correction laser beam 116 and the semiconductor waveguide 12 can define a path. In some embodiments, the path can be parallel to the plane of the photonic chip 10. For example, according to this embodiment, the path can be straight, arc-shaped, circular, and arbitrary. The path does not have to be limited to a plane, because it can also have a three-dimensional terrain. It is worth noting that step 408 is optional, because it can be omitted in some embodiments.

[0073] In some embodiments, the correction laser beam 116 is pulsed, and the step of moving the focus 114 of the correction laser beam 116 along the path includes delivering one or more laser pulses at each of a plurality of points spaced apart that are evenly or unevenly distributed along the path. The duration of the laser pulses may be 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 may carry about 0.01 J / cm 2 and about 100J / cm 2The laser pulse may carry an optical energy 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 μJ. It is desirable that the focus 114 of the correction laser beam 116 may be sufficiently intense to allow nonlinear absorption into the photonic chip 10. Examples of such nonlinear absorption mechanisms may include, but are not limited to, multiphoton absorption, tunnel ionization, free carrier absorption, impact ionization, and the like. Such nonlinear absorption mechanisms are typically implemented using fast (sub-microsecond) melting and resolidification photomatter processes. More specifically, such nonlinear absorption mechanisms may excite electrons from the valence band to the conduction band, thereby generating free carriers. Material modification, i.e., a change in the refractive index, may depend on the carrier density, their excitation energy levels (electron temperature), and / or the temporal dynamics of energy transfer between photons, electrons, and phonons. In general, in order to maximize the possible bandwidth of the refractive index change, the carrier density and the electron temperature may be maximized. Typically, rapid melting and resolidification can occur within a fast (sub-microsecond) time frame to reach the modification threshold. In some applications, laser wavelengths below the semiconductor bandgap wavelength are used. In these applications, strong surface single-photon photoionization can drive absorption processes, resulting in limited tuning bandwidth due to weak and shallow material modifications. In addition, photoionization-driven semiconductor modifications can lead to limited excited electron temperature and enhanced plasma shielding. The use of laser pulses with wavelengths higher than the semiconductor bandgap wavelength allows escape from direct photoionization and exploitation of deeper volume nonlinear absorption processes. Similarly, it is well known that higher electron temperatures can be achieved by increasing the laser wavelength, because the electron temperature increase effects of tunnel ionization, free carrier absorption, and impact ionization are all proportional to the square of the laser wavelength. In order to induce refractive index changes through crystalline semiconductor phases, femtosecond to nanosecond pulses are used to create compressive stress, thereby inducing positive or negative refractive index changes (e.g., 0.0002) at 1550nm. To induce the refractive index change by amorphizing the semiconductor phase, femtosecond to picosecond pulses are used to create a rapid quench, thereby inducing a larger refractive index change (eg, 0.06) at 1550 nm.

[0074] FIG. 5A to FIG. 5D Examples of different photonic chips 10 with semiconductor waveguides 12 are shown. It should be understood that the semiconductor waveguide 12 is not limited to a single linear semiconductor waveguide, but may include one or more semiconductor waveguides of arbitrary shapes. In some cases, the semiconductor waveguide 12 forms a specific photonic function. For example, Figure 5AAn example of a photonic chip 10 having a first semiconductor waveguide 12' and a second semiconductor waveguide 12" optically coupled to the first semiconductor waveguide is shown. More specifically, the second semiconductor waveguide 12" has a closed loop shape, forming a semiconductor resonator 18. In this particular example, the focus 114 of the correction laser beam can be directed to more than two circumferentially spaced locations around the semiconductor resonator 18. In some embodiments, each location is tapped with a single laser pulse (hereinafter referred to as a "laser tap") of a given energy. Accordingly, in this particular embodiment, only three laser taps of the correction laser beam are used to modify the photonic chip 10. In some other embodiments, the photonic chip 10 may be modified using less than three laser taps or more than three laser taps. The laser taps may be spaced apart from each other or directed to a common area of ​​the photonic chip.

[0075] exist Figure 5B In the embodiment, the photonic chip 10 includes a first semiconductor waveguide 12' and a second semiconductor waveguide 12". having a coupling region 13 extending therebetween. In this configuration, the first semiconductor waveguide 12' and the second semiconductor waveguide 12" can form an optical coupler, such as a directional coupler. In this particular example, the focus 114 of the correction laser beam can be directed to, for example, two or more axially spaced positions along the coupling region 13. It is worth noting that the number and / or positions of the laser taps are merely exemplary, as they may be different in some other embodiments.

[0076] exist Figure 5C In the embodiment, the photonic chip 10 has a semiconductor waveguide 12, which is divided into two arms 12' and 12". In this particular embodiment, the semiconductor waveguide 12 can form a Mach-Zehnder interferometer. For example, the focus 114 of the correction laser beam can be directed to the divided area passing through each of the two arms 12' and 12", and can also be directed to the combined area of ​​the semiconductor waveguide 12.

[0077] exist Figure 5D In the embodiment of the present invention, the semiconductor waveguide 12 is reversely tapered and expanded to an output portion, from which two auxiliary semiconductor waveguides 12' and 12" protrude. In this configuration, the semiconductor waveguide 12 can form a multi-mode interferometer. The portion of the semiconductor waveguide 12 towards which the focus 114 of the correction laser beam is directed can vary from embodiment to embodiment. For example, it can be directed to any area along the multi-mode interferometer. It should be understood that the example photonic functions described herein are provided only as examples, as other photonic functions can also be modified using the methods and systems described herein.

[0078] The number and / or position of the laser taps depends on the photonic function of the semiconductor waveguide. For example, for a Mach-Zehnder Interferometer (MZI), (one or more) laser taps can be directed to the coupling region or to each arm to modify the contrast of the MZI (for example, from 45%-55% to 50%-50%) and / or its phase. For a directional coupler, (one or more) laser taps can be directed to the coupling region to modify the overall coupling, because it is known that the coupling ratio depends on the refractive index change between the two semiconductor waveguides in the coupling region. For a splitter (1×N), (one or more) laser taps can be directed into the coupling (multimode) transition region to modify its coupling ratio and / or extinction ratio. For a combiner (M×1), (one or more) laser taps can be directed into the coupling (multimode) transition region to modify its combination ratio and / or the phase in each arm. For a Microring Resonator (MRR), laser tap(s) may be directed into the coupling region or into the annular cross section to modify its resonant wavelength, Q factor and / or extinction ratio, since it is well known that the transmission of the through or lead-in port depends directly on the round trip phase within the ring, which in turn depends on the refractive index of the semiconductor waveguide within the ring. For an Arrayed Waveguide Grating (AWG), laser tap(s) may be directed into the coupling (multimode) transition region to modify the coupling within one channel relative to the coupling within the other channels. For a cone, laser tap(s) may be directed into the cone region to modify its losses, changing nonlinear and dispersion characteristics. For a grating coupler, laser tap(s) may be directed onto the grating to modify its injection efficiency. For a Bragg grating, laser tap(s) may be directed along the Bragg grating to modify its wavelength, Q factor and / or extinction ratio. For a photodetector, laser tap(s) may be directed along the detector to modify its detection efficiency or anneal. For a Distributed Feedback Laser (DFB), the laser tap(s) may be directed to the active region to modify its wavelength. The embodiments listed above are for example only.

[0079] FIG. 6A to FIG. 6GAn example of a photonic chip 10 having a semiconductor waveguide 12 and a semiconductor resonator 18 optically coupled to the semiconductor waveguide 12 is shown. Although the semiconductor resonator 18 has a closed loop shape, it can be understood that the semiconductor resonator 18 is also regarded as the semiconductor waveguide 12. Accordingly, the step of directing the focus 114 of the correction laser beam into or near the semiconductor waveguide 12 means including the case of directing the focus 114 of the correction laser beam into or near the semiconductor resonator 18. In other words, the semiconductor waveguide 12 may include the semiconductor resonator 18.

[0080] exist Fig. 6A In the embodiment of the present invention, the correction laser beam 114 is first directed to the first part of the semiconductor resonator 18 and then to the second part of the semiconductor resonator 18, or vice versa. As shown, the first part is located at a first circumferential position of the semiconductor resonator 18, and the second part is located at a second circumferential position radially opposite to the first circumferential position. However, in some other embodiments, the two parts can be spaced circumferentially by 10 degrees, 25 degrees, 90 degrees, etc. In this particular example, the focus 114 of the correction laser beam can be moved along the z-axis to increase the area of ​​the second part relative to the first part. Therefore, the second part can have an area (e.g., 10 μm) larger than the area of ​​the first part (e.g., 1 μm). It is worth noting that each of the first part and the second part can receive one or more laser pulses or be exposed to a continuous wave (CW) laser within a given time period. In some other embodiments, two different laser correction laser beams can be used.

[0081] exist Figure 6B In the embodiment shown, the focus 114 of the correction laser beam moves radially inward along a linear path 115 through a portion of the semiconductor resonator 18. However, in some other embodiments, the focus 114 of the correction laser beam can move radially outward through the portion of the semiconductor resonator 18. In this embodiment, the overlap between consecutive laser taps can result in enhanced optical energy transmission at these overlapping portions.

[0082] exist Figure 6C , the focus 114 of the correction laser beam moves tangentially along an arc path 117 of a portion of the semiconductor resonator 18. Although the arc path 117 is shown as rotating in a clockwise direction, according to embodiments, the arc path 117 may also rotate in a counterclockwise direction. The arc path 117 may extend 15 degrees, 20 degrees, 45 degrees, or any other circumferential arc or offset.

[0083] exist Fig.6DIn the embodiment, the path 119 formed by the focus 114 of the correction laser beam is arbitrary relative to the semiconductor waveguide 12. It is understood that, according to the embodiment, the scanning speed of the focus 114 of the correction laser beam moving along the path can be constant or can vary with time.

[0084] exist Fig. 6E In the embodiment of the present invention, the correction laser beam is adjusted between consecutive laser taps to modify its intensity. More specifically, a first portion of the semiconductor resonator 18 is irradiated with a first intensity or a first pulse energy of the correction laser beam, while a second portion of the semiconductor resonator 18 is irradiated with a second intensity or a second pulse energy greater than the first intensity or pulse energy, or vice versa. For example, the first pulse energy may be 100 nJ, while the second pulse energy may be 1000 nJ. In some embodiments, there may be more than one correction laser beam.

[0085] For example, Fig. 6F As shown, the first focus 114a of the first correction laser beam is directed to the first portion of the semiconductor resonator 18, while the second focus 114b of the second correction laser beam is directed to the second portion of the semiconductor resonator. In this particular embodiment, the first correction laser beam and the second correction laser beam have different central wavelengths. However, the central wavelengths of both the first correction laser beam and the second correction laser beam are greater than the band gap wavelength of the semiconductor resonator so as to be able to propagate through the photonic chip 10. For example, in this embodiment, the spectral bandwidth of the first correction laser beam can be centered at about 1550nm, while the spectral bandwidth of the second correction laser beam can be centered at about 2800nm.

[0086] exist Figure 6G In the embodiment, a single portion of the semiconductor resonator 18 is illuminated by a correction laser beam of different spatial modes. For example, the portion may be modified using light of a first spatial mode (e.g., LP01), while the portion may be modified using light of a second spatial mode (e.g., LP02, LP11, LP21) different from the first spatial mode. In other embodiments, different portions of the semiconductor resonator are modified using light of different spatial modes.

[0087] Reference now Fig. 7A and 7B , the photonic chip 10 has a substrate 14, a semiconductor waveguide 12 on top of the substrate 14, and a cladding 16 covering the top surfaces of the semiconductor waveguide 12 and the substrate 14. In these embodiments, it is worth noting that the focus 114 of the correction laser beam can be passed through the cladding 16 (such as from above) Fig. 7A as shown) or from below through the substrate 14 (such as Figure 7BIn some embodiments, the correction laser beam 116 may be directed through one or more waveguides, claddings, or other material layers to reach the desired semiconductor waveguide 12 of interest. As shown, the focus 114 of the correction laser beam may be directed into or near the semiconductor waveguide 12. In these embodiments, it is understood that the substrate 14 and cladding 16 also have a bandgap wavelength and / or optical transmission window that allows the correction laser beam 116 to be transmitted. In embodiments where the refractive index modification is performed within the semiconductor waveguide 12, the effective refractive index of the semiconductor waveguide 12 may be changed. In embodiments where the external refractive index modification is slightly performed on the outside of the semiconductor waveguide 12, for example, within the adjacent cladding, it is understood that the effective refractive index of the semiconductor waveguide 12 may also be changed. In fact, since a light beam propagating along the semiconductor waveguide 12 typically has an attenuation tail extending to the outside of the semiconductor waveguide, if the attenuation tail reaches the external refractive index modification, it will affect the optical signal, thereby affecting the effective refractive index of the semiconductor waveguide 12.

[0088] It is contemplated that the size of the focal point relative to the size of the semiconductor waveguide may vary from embodiment to embodiment. Figure 8 , the focus 114 can have a Rayleigh range (depth of focus, zr) extending along the correction laser beam and a spot size (d) extending laterally through the correction laser beam. The semiconductor waveguide 12 has a waveguide width w extending within the plane of the photonic chip 10 and a thickness t extending through the plane of the photonic chip 10. As shown in this particular embodiment, the spot size is greater than the waveguide width w, and the Rayleigh range zr is greater than the waveguide thickness t. However, in some other embodiments, the spot size d can be less than the waveguide width w. Additionally or alternatively, the Rayleigh range zr of the focus of the correction laser beam can be less than the waveguide thickness t. Any combination of these dimensions can be used according to the embodiment.

[0089] On the other hand, Fig. 9 A flow chart of an example of a method 900 for testing a photonic chip is shown. In this aspect, the photonic chip has a semiconductor waveguide and a plurality of semiconductor elements optically coupled to the semiconductor waveguide. Each semiconductor element has a bandgap wavelength. In some embodiments, the semiconductor element is a semiconductor resonator, such as a ring resonator or a photonic crystal resonator, a semiconductor, or the like.

[0090] In step 902, a test routine is performed on the semiconductor waveguide. More specifically, the test routine includes the steps of directing a test optical signal into and along the semiconductor waveguide, detecting an output signal resulting from the directing, and monitoring an output spectrum based on the output signal. In some embodiments, the output spectrum may be an optical output spectrum, a radio frequency output spectrum, or the like. While performing the test routine, step 902 includes another step of directing the focus of a probe laser beam into a portion of the photonic chip, the portion being one of a portion near one of the semiconductor elements and a portion within one of the semiconductor elements. It is noteworthy that the probe laser beam has a central wavelength greater than the band gap wavelength of the semiconductor element. Additionally or alternatively, it is desirable that the central wavelength may partially or completely overlap with the optical transmission window of the semiconductor element. Thus, the semiconductor element is optically transparent to the probe laser beam. Step 902 results in a step of modifying the effective refractive index of a portion of one of the semiconductor elements. In some embodiments, multiple semiconductor elements may be laser tapped in one or more iterations.

[0091] In step 904, an optical signature is identified in the output spectrum that has been modified in response to the directed step 902. Examples of optical signatures may include, but are not limited to, spectral signatures, resonant signatures, and the like.

[0092] In step 906, the optical characteristic is associated with one of the semiconductor components.

[0093] Thus, if the photonic chip has a large number of components, the method 900 can be used to map the optical characteristics of the output spectrum to the corresponding semiconductor components. It is worth noting that the method 900 is generally performed for the purpose of identification and / or mapping, and is not intended to cause significant effective refractive index changes. Accordingly, the guiding step can be limited to lower powers to modify the effective refractive index only by a negligible amount. For example, the effective refractive index of the semiconductor waveguide portion can be modified by an amount between about 0.01 and about 0.00001, preferably between about 0.001 and about 0.00005, and most preferably between about 0.005 and about 0.0001. In some embodiments, the refractive index modification can be temporary or permanent.

[0094] like Fig.10As shown in the embodiment of FIG. 1 , the photonic chip 10 has a main semiconductor waveguide 12 and three auxiliary semiconductor elements 18 ′, 8 ″ and 18 ′″ optically coupled to the main semiconductor waveguide 12. Each semiconductor element has its own optical characteristics, such as spectral resonance, and these optical characteristics are different from each other, for example. In this embodiment, a test routine is performed in a continuous manner to monitor the optical characteristic R of each auxiliary semiconductor element 18 ′, 18 ″ and 18 ′″. By directing the focus 114 of the probe laser beam 116 onto a given one of the auxiliary semiconductor elements 18 ′, 18 ″ and 18 ′″, the test routine shows that the optical characteristic R1 has undergone a slight spectral shift. In this way, the given auxiliary semiconductor element 18 ′ can be associated with the optical characteristic R1. Accordingly, if it is later discovered that the optical characteristic R1 is a parameter that does not match the corresponding reference parameter, then a larger amount of optical energy can be transmitted to the given auxiliary semiconductor element 18 ′ using the focus 114 of the probe laser beam 116 to modify its effective refractive index until the measured parameter matches the reference parameter within a given tolerance.

[0095] Experiments have been conducted using the methods and systems described herein to demonstrate that fine and coarse tuning of the effective refractive index of a semiconductor waveguide can be effectively achieved. One of these experiments involves a photonic chip having a Mach-Zehnder interferometer (MZI) formed using one or more semiconductor waveguides. More specifically, the MZI has a main semiconductor waveguide that is divided into two equal-length MZI arms at a first coupling point. The two MZI arms are recombined at a second coupling point downstream of the first coupling point. It is understood that when the optical signal propagates along the main semiconductor, it will be divided into two optical signal portions, which will interfere destructively or constructively once recombined at the second coupling point. Typically, if the length or effective refractive index of the MZI arm is similar, the optical signal portion will experience similar propagation conditions in each MZI arm, and the interference occurring at the second coupling point will be constructive interference. However, if there is a length difference or an effective refractive index difference between the two MZI arms, the MZI will become unbalanced, resulting in spectral modulation of the optical signal after recombination, which can be observed in the output optical signal.

[0096] In this experiment, subsequent sets of refractive index modifications were performed only near one MZI arm such as the equal-arm-length MZI discussed above. After each set of refractive index modifications, the spectral response of the resulting MZI was measured. Fig.11ASchematically, these groups correspond to linear channels L1, L2, ... L6 close to and parallel to the focus of the correction laser beam of the MZI arm. Linear channels L1, L2 and L3 are made on one side of the MZI arm, while the other channels L4, L5 and L6 are made on the other side of the MZI arm. In this particular embodiment, the length of each linear channel is about 50 μm and the lateral spacing from the MZI arm is about 7 μm. Most preferably, as Fig. 11B As shown, this figure shows the spectral response measured after each of the above series of linear passes, the spectral response of the MZI changes slightly with each additional linear pass. Fig. 11B The results shown confirm that by carefully positioning the refractive index modification close to the MZI arms, subtle or fine tuning of the effective refractive index of the semiconductor waveguide can be achieved when desired.

[0097] In another experiment, subsequent sets of refractive index modifications were performed in only one MZI arm, such as the equal-arm-length MZI discussed above. After each set of refractive index modifications, the spectral response of the resulting MZI was measured. Fig. 12A As shown, these groups correspond to linear channels P1, P2, ... P6 of the focus of the correction laser beam within and across the MZI arm. Each of these linear channels is about 15 μm long and is spaced about 10 μm apart from each other. Fig. 12B As shown, it is demonstrated that this invasive refractive index modification can effectively achieve coarse tuning of the effective refractive index of the semiconductor waveguide.

[0098] In another experiment, six different photonic chips were fabricated using known techniques, each with a corresponding MZI. As shown, the spectral responses of these MZIs differ greatly from each other, which is a common situation in the industry. However, using the methods and systems discussed herein, six different photonic chips were modified using refractive index modifications applied near and / or within the semiconductor waveguides to coarse and fine tune their respective spectral responses until they reached reference parameters.

[0099] It is worth noting that the above reference Figure 1 The controller discussed may be provided as a combination of hardware and software components. The hardware components may be implemented in the form of a computing device 1100, an example of which is shown in FIG. Fig.14 Furthermore, the software components of the controller may be implemented in the form of a software application that performs some or more steps of the method for modifying a photonic chip or the method for testing a photonic chip.

[0100] Still refer to Fig.14, the computing device 1100 may have a processor 1102 , a memory 1104 , and an I / O interface 106 . Instructions 1108 for performing the above-described method 400 or 900 may be stored on the memory 1104 and may be accessed by the processor 1102 .

[0101] The processor 1102 may 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.

[0102] Memory 1104 may include a suitable combination of any type of computer-readable memory located internally or externally, such as, for example, random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), electrically-erasable programmable read-only memory (EEPROM), ferroelectric random access memory (FRAM), etc.

[0103] Each I / O interface 1106 enables the computing device 1100 to be interconnected with one or more input devices (such as photonic chip testing equipment, (one or more) detectors, a computer vision system), or with one or more output devices (such as a multi-axis motion stage, an external network, or an accessible memory system).

[0104] Each I / O interface 1106 enables the controller to communicate with other components, exchange data with other components, 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) lines, Public Switch Telephone Network (PSTN), Integrated Services Digital Network (ISDN), Digital Subscriber Line (DSL), coaxial cable, fiber optic, 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.

[0105] The controller can use the instructions 108 to run one or more software applications configured to operate the system described herein. In some embodiments, the software application is stored on the memory 1104 and accessed by the processor 1102 of the computing device 1100. The computing device 1100 and the software application described above are meant to be examples only. Other suitable embodiments of the controller 1132 can also be provided, which will be apparent to those skilled in the art.

[0106] It is understood that the examples described and illustrated above are exemplary only. For example, more than one correction laser beam may be used to perform the methods and systems described herein. It is noteworthy that the photonic chip may have multiple photonic functions and / or photonic elements, each with a dedicated channel. The methods and systems described herein may be applied to each photonic function, each photonic element, and each photonic channel of the photonic chip 10. Depending on the embodiment, the characteristics of the correction laser beam may vary. To name a few examples, examples of these characteristics may include, but are not limited to, pulse duration, repetition rate, burst mode, pulse energy, laser wavelength, laser intensity, beam shape (e.g., Gaussian, top edge, Bessel, elliptical), fixed or moving beam, scanning speed, scanning spacing (hatch), and laser path. The number and / or position of the laser taps may depend on the geometry and material of the semiconductor waveguide. In addition, the methods and systems described herein may be applicable to limiting the losses suffered by the photonic chip, ensuring accurate positioning of the correction laser beam relative to the photonic chip, maximizing the compensation range, and imparting positive or negative refractive index changes. When the semiconductor waveguide is surrounded by multiple layers of material (e.g., glass insulator, other semiconductor layers), the effective refractive index change can be selective to a specific layer. The refractive index can be changed by different processes including but not limited to amorphization, stress induction, void generation, densification, etc. The laser-induced refractive index modification can be paired with other heating sources (e.g., (one or more) thermal heaters, (one or more) ionization sources (e.g., input voltage in the semiconductor waveguide) or another laser beam absorbed by the semiconductor waveguide) to optimize the methods and systems described herein. The correction laser beam can be perpendicular to the plane of the photonic chip or at an acute or obtuse angle relative to the plane of the photonic chip. In some embodiments, structures such as fiber Bragg gratings or polarizers can be created with the effective refractive index change inside the semiconductor waveguide. It should be understood that modifying the effective refractive index can include modification of the real part of the refractive index, modification of the imaginary part of the refractive index, or a combination thereof. In some embodiments, the central wavelength of the correction laser beam can be adjusted to control process parameters and optimize the correction according to the type of semiconductor material. In some embodiments, the refractive index modification can be imparted in a manner that can affect the polarization of the optical signal propagating along the semiconductor waveguide. For example, the refractive index modification can extend on opposite sides of the semiconductor waveguide to maintain or change the polarization. In a specific embodiment, as just one example, Fig.11AThose refractive index modifications shown can be used to simulate the structure of polarization-maintaining optical fibers. In embodiments where the photonic chip is based on an InP semiconductor platform, such refractive index modifications can form matrix defects that can attract electrons and thus reduce light losses occurring along the semiconductor waveguides. Although the semiconductor waveguides shown in the above examples are quite simple and unitary, complex structures for semiconductor waveguides can be used in some other embodiments. For example, a semiconductor waveguide can include one or more semiconductor waveguides running side by side, and a substrate (e.g., a glass substrate) extending between them. The scope is indicated by the appended claims.

Claims

1. A method of modifying a photonic chip having a semiconductor waveguide having a bandgap wavelength, the method comprising: directing a focus of a correction laser beam into a portion of the photonic chip, the portion being one of a portion proximate to the semiconductor waveguide and a portion within the semiconductor waveguide, the correction laser beam having a central wavelength greater than a bandgap wavelength of the semiconductor waveguide, the directing modifying an effective refractive index of the portion of the semiconductor waveguide; performing a test routine on the semiconductor waveguide, the test routine comprising determining a parameter indicative of performance of the semiconductor waveguide; as well as Upon determining that the parameters do not match reference parameters associated with a reference photonic chip, the directing and testing routines are repeated until the parameters match the reference parameters within a given tolerance.

2. The method according to claim 1, wherein: The directing includes moving at least one of a focus of the correction laser beam and the photonic chip along a path.

3. The method according to claim 2, wherein: The moving includes transmitting a laser pulse at each of a plurality of spaced-apart points distributed along the path.

4. The method according to claim 1, wherein: The testing routine includes directing a test optical signal into and along the semiconductor waveguide, detecting an output signal resulting from the directing, and determining the parameter based on the output signal.

5. The method according to claim 4, wherein: The directing includes injecting the test optical signal into the first end of the semiconductor waveguide.

6. The method according to claim 5, wherein: The detecting includes measuring the output signal using a photodiode optically coupled to the second end of the semiconductor waveguide.

7. The method according to claim 4, wherein: The detecting includes measuring the output signal scattered from the semiconductor waveguide using a camera during the directing.

8. The method according to claim 1, wherein: The parameter is at least one of output wavelength, output phase, output amplitude, output polarization, output dispersion and output loss.

9. The method according to claim 1, wherein: The central wavelength of the correction laser beam is between about 1 μm and about 20 μm, preferably between about 1.2 μm and about 10 μm, and most preferably between about 1.5 μm and about 4 μm.

10. The method according to claim 1, wherein: The correction laser beam has laser pulses having a duration 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.

11. The method according to claim 1, wherein: The semiconductor waveguide is placed relative to a substrate, the photonic chip further has a cladding covering a top surface of the substrate and the semiconductor waveguide, and the guiding includes guiding a focus of the correction laser beam through at least one of the cladding and the substrate.

12. The method according to claim 1, wherein: The photonic chip has a plurality of semiconductor waveguides, each semiconductor waveguide having a bandgap wavelength, and the method further includes performing the guiding and testing routines for each semiconductor waveguide in the plurality of semiconductor waveguides until a plurality of parameters associated with the plurality of semiconductor waveguides match respective reference parameters within a given tolerance.

13. A system for modifying a photonic chip having a semiconductor waveguide having a bandgap wavelength, the system comprising: a correction laser device configured to direct a focus of a correction laser beam into a portion of the photonic chip, the portion being one of a portion proximate to the semiconductor waveguide and a portion within the semiconductor waveguide, the correction laser beam having a central wavelength greater than a bandgap wavelength of the semiconductor waveguide, the directing modifying an effective refractive index of the portion of the semiconductor waveguide; a photonic chip testing device that performs a test routine on the semiconductor waveguide, the test routine including determining a parameter indicative of a performance of the semiconductor waveguide; as well as A controller is communicatively coupled to the correction laser device and the photonic chip testing device, wherein the controller has a processor and a memory, wherein the memory has instructions stored thereon, and when the processor executes the instructions, the following steps are performed: comparing the parameters with reference parameters associated with a reference photonic chip; as well as Upon determining that the parameter does not match the reference parameter, the guiding and testing routines are repeated until the parameter matches the reference parameter within a given tolerance.

14. The system according to claim 13, wherein: The correction laser device comprises a laser source that generates the correction laser beam with a central wavelength between about 1.0 μm and about 20 μm, preferably between about 2.5 μm and about 10 μm, and most preferably between about 2.8 μm and about 3.4 μm.

15. The system of claim 13, wherein: The correction laser device includes a laser source that generates laser pulses having a duration 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.

16. The system of claim 13, wherein: The calibration laser device has a fiber laser source.

17. The system of claim 13, further comprising a multi-axis translation stage having a support area on which the photonic chip is received, the multi-axis translation stage moving the photonic chip during the guiding.

18. The system of claim 13, wherein: The photonic chip testing device includes a test light source and a detector, wherein the test light source directs a test light signal into and along the semiconductor waveguide, the detector detects an output signal caused by the directing, and the controller determines the parameter based on the output signal.

19. The system of claim 13, wherein: The detector is a photodiode optically coupled to the first end of the semiconductor waveguide for detecting the output signal.

20. The system of claim 13, wherein: The detector is an infrared camera that measures the output signal scattered from the semiconductor waveguide during the directing period.

21. A method for testing a photonic chip, the photonic chip having a semiconductor waveguide and a plurality of semiconductor elements optically coupled to the semiconductor waveguide, the semiconductor elements having a bandgap wavelength, the method comprising: When performing a test routine on the semiconductor waveguide, the test routine includes directing a test optical signal into and along the semiconductor waveguide, detecting an output signal resulting from the directing and monitoring an output signal based on the output signal, directing a focus of a probe laser beam into a portion of the photonic chip that is one of a portion proximate to one of the plurality of semiconductor elements and a portion within the one of the semiconductor elements, the correction laser beam having a center wavelength greater than the bandgap wavelength of the semiconductor element, the directing modifying an effective refractive index of the portion of the one of the semiconductor elements; identifying an optical feature in the output spectrum that is modified in response to the directing; as well as The optical characteristic is associated with the one of the semiconductor elements.

22. The method according to claim 21, wherein: The modification comprises modifying the effective refractive index of the portion of the semiconductor waveguide by an amount between about 0.1 and about 0.00000001, preferably between about 0.05 and about 0.0005, and most preferably between about 0.01 and about 0.

001.

23. A system for testing a photonic chip, the photonic chip having a semiconductor waveguide and a plurality of semiconductor elements optically coupled to the semiconductor waveguide, the semiconductor elements having a bandgap wavelength, the system comprising: a photonic chip testing apparatus that performs a test routine that includes directing a test optical signal into and along the semiconductor waveguide, detecting an output signal resulting from the directing, and monitoring an output spectrum based on the output signal; a correction laser device configured to direct a focus of a correction laser beam into a portion of the photonic chip, the portion being one of a portion near one of the plurality of semiconductor elements and a portion within the one of the semiconductor elements, the correction laser beam having a central wavelength greater than a bandgap wavelength of the semiconductor waveguide, the directing modifying an effective refractive index of the portion of the one of the semiconductor elements; and A controller is communicatively coupled to the photonic chip testing device and the correction laser device, the controller has a processor and a memory, the memory has instructions stored therein, and when the processor executes the instructions, the following steps are performed: identifying an optical feature in the output spectrum that is modified in response to the directing; as well as The optical characteristic is associated with the one of the semiconductor elements.

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