Grating coupler, optical communication system and grating coupler manufacturing method

Abstract

Embodiments herein disclose a grating coupler integrated in a photon-enabled circuit and a method for manufacturing the same. In some embodiments, the grating coupler comprises: a substrate comprising a silicon wafer; a first grating region etched into the substrate, wherein the first grating region comprises a plurality of first gratings having a first predetermined height; and a second grating region etched into the substrate, wherein the second grating region comprises a plurality of second gratings having a second predetermined height, and wherein the first predetermined height and the second predetermined height are different.

Description

Technical Field

[0001] The embodiments of the present invention relate to a grating coupler, an optical communication system and a method for manufacturing the grating coupler. Background Art

[0002] Photonic integration is a key technology for future advances in optical communications. Scaled-down optical building blocks enable cost-effective, complex, and ultra-compact photonic circuits, i.e., chips that include integrated grating couplers (GCs) formed on or in a substrate and interconnected by coupling light entering or leaving a photonic integrated circuit (PIC) into free space or into optical fibers.

[0003] These grating couplers are advantageous because they can be tightly packed together in or on a planar platform (i.e., a semiconductor substrate) to form a planar package similar to an integrated circuit (IC). In addition, GCs offer compact size, ease of manufacture, flexible placement, and wafer-level testing. In addition, GCs, similar to conductor traces in semiconductor electronic ICs, are mounted in or on a silicon substrate and can be used to direct light to various optical, electro-optical, and optoelectronic devices or components on a PIC.

[0004] In many silicon photonic applications, GCs with high coupling efficiency and wide bandwidth are desired. In addition, sensing applications using visible light, such as LiDAR, require GCs with reduced back reflections. Optical noise caused by back reflections can increase optical instabilities in interferometric devices and produce ripples and / or oscillations. In addition, optoelectronic devices such as lasers and photodiodes are generally sensitive to back reflections because they contribute to noise generation, especially in optical circuits implementing optical feedback schemes. For efficient grating couplers, typical back reflections into the on-chip waveguide can be about -17 dB, while high back reflections of -10 dB and -8 dB have also been reported. Current GCs and their manufacturing methods do not provide high coupling efficiency and low back reflection characteristics. For this reason, low back reflection GCs and their manufacturing methods are needed for visible light applications.

[0005] The information disclosed in this Background section is intended only to provide context for the various embodiments of the invention described below, and therefore, this Background section may contain information that is not necessarily prior art information (i.e., information already known to one of ordinary skill in the art). Therefore, to the extent that the work is described in this Background section, the work of the presently named inventors and aspects of the description that may not have otherwise qualified as prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art against the present disclosure. Summary of the invention

[0006] According to an embodiment of the present invention, a grating coupler includes: a substrate including a silicon wafer; a first grating region etched in the substrate, wherein the first grating region includes a plurality of first gratings having a first predetermined height; and a second grating region etched in the substrate, wherein the second grating region includes a plurality of second gratings having a second predetermined height, wherein the first predetermined height and the second predetermined height are different.

[0007] According to an embodiment of the present invention, an optical communication system comprises: an optical fiber; and a photonic integrated circuit, comprising a grating coupler assembly, wherein the grating coupler assembly is configured to couple light carried in the optical fiber into or out of the photonic integrated circuit, wherein the grating coupler assembly comprises: a substrate comprising a silicon wafer; a first grating region etched in the substrate, wherein the first grating region comprises a plurality of first gratings having a first predetermined height; and a second grating region etched in the substrate, wherein the second grating region comprises a plurality of second gratings having a second predetermined height, wherein the first predetermined height and the second predetermined height are not the same.

[0008] According to an embodiment of the present invention, a method for manufacturing a grating coupler includes: forming a substrate layer; etching a first grating region into the substrate layer, wherein the first grating region includes a plurality of first gratings having a first predetermined height; and etching a second grating region into the substrate layer, wherein the second grating region includes a plurality of second gratings having a second predetermined height, wherein the first predetermined height and the second predetermined height are not the same; and forming a coating layer including silicon dioxide on the first grating region and the second grating region. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various exemplary embodiments of the present disclosure are described in detail below with reference to the following drawings. The drawings are provided for illustrative purposes only and only depict exemplary embodiments of the present disclosure to facilitate the reader's understanding of the present disclosure. Therefore, the drawings should not be considered to limit the breadth, scope or applicability of the present disclosure. It should be noted that for the sake of clarity and simplicity of illustration, these drawings are not necessarily drawn to scale.

[0010] Figure 1 is a schematic diagram illustrating an exemplary optical transceiver according to some embodiments.

[0011] Figure 2 The electromagnetic spectrum and optical communication wavelength bands are shown according to some embodiments.

[0012] Figure 3 is a cross-sectional view of an integrated 1D apodized GC assembly for reducing back reflection noise according to some embodiments.

[0013] Figure 4A Measured coupling loss and back reflection are shown for an apodized GC having one grating region containing a single-stage etched grating according to some embodiments.

[0014] Figure 4B Measured coupling loss and back reflection are shown for an apodized GC having two grating regions with two different levels of etched gratings according to some embodiments.

[0015] Figure 5 A flow chart illustrating a method for fabricating an apodized GC having two grating regions with two different levels of etched gratings according to some embodiments. DETAILED DESCRIPTION

[0016] Various exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings to enable a person of ordinary skill in the art to make and use the present disclosure. As will be apparent to a person of ordinary skill in the art, after reading the present disclosure, various changes or modifications may be made to the examples described herein without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the exemplary embodiments and applications described and shown herein. In addition, the specific order and / or hierarchy of the steps in the methods disclosed herein are only exemplary methods. Based on design preferences, the specific order or hierarchy of the steps of the disclosed methods or processes may be rearranged while remaining within the scope of the present disclosure. Therefore, a person of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or actions in an example order, and unless otherwise expressly stated, the present disclosure is not limited to the specific order or hierarchy presented.

[0017] like Figure 1As shown in , the exemplary optical transceiver 100 may include an optical modulator 117, a monitoring photodiode 113, and optical grating couplers 115 and 121. In some embodiments, the optical modulator 117 may include two arm waveguides, a high speed phase modulator (HSPM), a pin phase modulator (PIN-OM), a driver, a Mach-Zehnder interferometric (MZI) modulator, and a calibration circuit. In addition, the optical modulator 117 may receive a continuous wave (CW) light input. In addition, the input CW light is split into two beams of light by a 1×2 coupler, and the split light is then modulated in phase in the two arm waveguides, and the phase-modulated light is coupled at the output by a 2×1 coupler. The exemplary optical transceiver 100 may also include electrical devices and circuits, including amplifiers 105 and 125, analog / digital converter circuit 111, digital control circuit 101, photodiode 107, and control section 109. For example, amplifiers 105 and 125 may include transimpedance and limiting amplifiers (TIA / LA). In some embodiments, amplifier 105 receives I-channel data signals and Q-channel data as inputs to optical transceiver 100 through various input interfaces (e.g., small form-factor pluggable (SFP) interface). In addition, amplifier 105 outputs amplified versions of the input I-channel data and Q-channel data. Figure 1 , the modulator 117 receives the I-channel data signal and the Q-channel data signal from the amplifier 105. In some embodiments, the exemplary optical transceiver 100 may further include a photonic die 103 having a laser assembly. In some embodiments, the laser assembly may include one or more semiconductor lasers 131, a lens, a rotator for directing one or more continuous wave (CW) optical signals, and one or more laser drivers 129.

[0018] In further embodiments, the exemplary optical transceiver 100 may include a coupler 137 configured to receive an optical signal from the laser 131 and a beam splitter 133 configured to split the optical signal into four substantially equal power optical signals. In various embodiments, the split power signal may be transmitted from the beam splitter 133 to the optical modulator 117 via an optical waveguide. In some embodiments, the beam splitter 133 may be coupled to at least one coupler 137 (e.g., an input waveguide) and at least four output waveguides 102. In some embodiments, the beam splitter 133 may include a low-loss Y-junction power divider. In some embodiments, at least one coupler 137 (e.g., an input waveguide) may include a single polarization grating coupler (SPGC).

[0019] In some embodiments, the optical modulator 117 may include, for example, a Mach-Zehnder or ring modulator and enable modulation of a continuous wave (CW) laser input signal. The optical modulator 117 may also include high speed and low speed phase modulation sections and be controlled by the control section 109. In some embodiments, at least one of the outputs of each of the optical modulators 117 may be optically coupled to an optical output 120 such as an optical fiber via a grating coupler 115. In some embodiments, the grating coupler 115 may include a single polarization grating coupler (SPGC). The other output of the optical modulator 117 may be optically coupled to a monitoring photodiode 113 configured to provide a feedback path from the output of the optical modulator 117 to the section control 109.

[0020] In addition, the exemplary optical transceiver 100 may also utilize a grating coupler 121 to receive an optical signal from the optical input 119. In other embodiments, the grating coupler 121 may include a single polarization grating coupler (SPGC) and / or a polarization splitting grating coupler (PSGC). In the case of utilizing a PSGC, two input or output waveguides may be utilized.

[0021] In some embodiments, the exemplary optical transceiver 100 employs a photodiode 107, which may be implemented using epitaxial germanium / SiGe films deposited directly on silicon. In other embodiments, the photodiode 107 may include, for example, a high-speed heterojunction phototransistor, and may include germanium (Ge) in the collector and base regions for absorption in the 1.3 micron to 1.6 micron optical wavelength range, and may be integrated on a CMOS silicon-on-insulator (SOI) wafer. The photodiode 107 may be configured to convert optical signals received from the PSGC 121 into electrical signals that are communicated to a receiver (Rx) 123, which may be configured to combine data streams and demultiplex the received optical signals. In addition, the received optical signals may be amplified, for example, by a transimpedance amplifier 125, and then communicated to a small package pluggable (SFP) interface circuit 127.

[0022] In some embodiments, the exemplary optical transceiver 100 may also include a digital control circuit 101 coupled to the serial interface 135 and configured to transmit the received optical data through the serial interface 135 .

[0023] like Figure 1 , the grating coupler 115 and the grating coupler 121 of the optical transceiver 100 enable light to be coupled into and out of an integrated circuit including the optical transceiver 100. In some embodiments, the grating coupler 115 and the grating coupler 121 may include regions of medium etched gratings and shallow etched gratings.

[0024] In some embodiments, the transmission or reception optical path of the optical transceiver 100 may include an optical waveguide connected to the grating coupler 115 and the grating coupler 121. In some embodiments, the grating coupler 121 may also be referred to as a grating coupler pair. In some embodiments, the first coupler of the grating coupler pair 121 may be configured for a transverse electric (TE) mode, and the second coupler of the grating coupler pair 121 may be configured for a transverse magnetic (TM) mode.

[0025] In some embodiments, grating coupler 115 and grating coupler 121 may be used in Figure 2201. For example, the grating coupler 115 and the grating coupler 121 can receive optical signals in a wavelength region within a range of 1260 nanometers to 1625 nanometers. In some embodiments, the grating coupler 115 and the grating coupler 121 can be configured to receive and / or transmit optical signals in at least one of the following five wavelength bands: O-band 203, E-band 205, S-band 207, C-band 209, and L-band 211. In some embodiments, the O-band 203 having an optical light wavelength within a range of 1260 nanometers to 1360 nanometers exhibits minimal chromatic dispersion. Thus, an optical fiber coupled to the grating coupler 115 and / or the grating coupler 121 and carrying optical communications in the O-band 203 can exhibit less transmission loss.

[0026] In some other embodiments, the optical fiber coupled to the grating coupler 115 and / or the grating coupler 121 and carrying optical communications in a metropolitan, long-haul, ultra-long-haul, or submarine optical network may also exhibit low loss in the C-band 209 having an optical light wavelength in the range of 1530 nanometers to 1565 nanometers. In some embodiments, when the bandwidth available in the C-band 209 is insufficient, the optical fiber coupled to the grating coupler 115 and / or the grating coupler 121 may carry optical communications in the L-band 211 having an optical wavelength in the range of 1565 nanometers to 1625 nanometers. In various embodiments, the optical fiber coupled to the grating coupler 115 and / or the grating coupler 121 and carrying optical downstream communications in the S-band 207 having an optical wavelength in the range of 1460 nanometers to 1530 nanometers may also be used in a passive optical network (PON). The E-band 205, having optical wavelengths in the range of 1360 nanometers to 1460 nanometers, may also be used to carry optical communications using optical fibers coupled to the grating coupler 115 and / or the grating coupler 121, despite attenuation due to residual water (OH groups) impurities in the optical fiber glass, which may be the least desirable of the optical bands discussed.

[0027] Figure 3 A cross-sectional view of a grating coupler assembly 300 configured with two grating couplers 115 and / or grating couplers 121 of different etching levels according to some embodiments is shown. The grating coupler assembly 300 couples a single polarization component of an out-of-plane light beam with a waveguide polarization mode. In some embodiments, the grating coupler assembly 300 may include a substrate 305. In some embodiments, the substrate 305 may be a silicon (Si) substrate used to manufacture integrated circuits, which may also include a silicon dioxide layer formed thereon. In other embodiments, the substrate 305 may be a glass substrate.

[0028] In an embodiment, the grating coupler assembly 300 is formed in a portion of a substrate layer 303 (e.g., a silicon layer), which also defines a silicon waveguide coupled to the grating coupler assembly 300. The total thickness of the substrate layer 303 (e.g., a silicon layer) is represented by H1. In some embodiments, the thickness H1 of the substrate layer 303 (e.g., a silicon layer) may preferably be in the range of about 200 nanometers to 500 nanometers in order to maximize the coupling efficiency (CE) of the grating coupler assembly 300.

[0029] In some embodiments, the grating coupler assembly 300 and the silicon waveguide may be covered by one or more transparent layers 301, which may be reserved for other PIC functions. In some embodiments, the one or more transparent layers 301 may include a cladding layer formed of SiO2. In other embodiments, the substrate layer 303 (e.g., a silicon layer) containing the grating coupler assembly 300 may have a refractive index n eff , and the cladding layer of one or more transparent layers 301 may have a refractive index n cladding The refractive index of the substrate layer 303 (eg, a silicon layer) may be greater than the refractive index of the cladding layer of the one or more transparent layers 301 .

[0030] In an embodiment, the disclosed 1D grating coupler assembly 300 may include a plurality of grating elements 311. In some embodiments, the plurality of grating elements 311 may be configured to couple an out-of-plane received or transmitted optical beam to an integrated waveguide. In an embodiment, the out-of-plane optical beam may be coupled to the plurality of grating elements 311 via free space propagation and / or optical fiber.

[0031] In some embodiments, the grating coupler assembly 300 includes a grating element 311 (e.g., a first grating line) and first grating spaces 309, 312. In some embodiments, the width w1 of the grating element 311 (e.g., a first grating line) and the width w2 of the first grating spaces 309, 312 can be numerically optimized to maximize the mode overlap between the optical fiber and the grating coupler assembly 300, thereby generating a maximum coupling efficiency CE in a given communication band (e.g., C-band). In addition, the number of grating elements 311 (e.g., first grating lines) is also numerically optimized to maximize the coupling efficiency CE.

[0032] In some embodiments, the grating elements 311 (e.g., first grating lines) may preferably be etched to the substrate layer 303 (e.g., silicon layer). Dry etching or wet etching in combination with photolithography may be used for this purpose. In some embodiments, the grating coupler assembly 300 may include two or more different etching regions. For example, the grating coupler assembly 300 may include an intermediate etching region and a shallow etching region. Thus, the first height H2 of the first grating lines in the intermediate etching region measured relative to the first grating base plate 307 may preferably be in the range of about 70 nanometers to 210 nanometers. In addition, the second height H3 of the second grating lines 308 in the shallow etching region measured relative to the second grating base plate 313 may preferably be in the range of about 100 nanometers to 210 nanometers. An exemplary advantage of having two or more than two different etching regions in the grating coupler assembly 300 is to reduce back reflection losses and increase coupling efficiency CE in a given communication band.

[0033] In some embodiments, the formation of the intermediate etching region and the shallow etching region may include sequentially (e.g., performing two etching steps) forming predetermined etching mask patterns for the intermediate etching region and the shallow etching region. In some embodiments, a different patterned photoresist formed by any one of exposure methods (e.g., electron beam (EB) exposure and holographic exposure) may be used as a mask to dry-etch the substrate layer 303 (e.g., a silicon layer) so as to form grating lines in the intermediate etching region and the shallow etching region.

[0034] In some embodiments, the width w1 of the grating line 311 in the middle etched area may be different from the width w3 of the second grating line 308 in the shallow etched area. In addition, the width w2 of the first grating space 309, 312 may also be different from the width w4 of the second grating space 310. In some embodiments, the width w1 may be in the range of about 10 nanometers to 1000 nanometers, the width w2 may be in the range of about 10 nanometers to 1000 nanometers, the width w3 may be in the range of about 10 nanometers to 1000 nanometers, and the width w4 may be in the range of about 10 nanometers to 1000 nanometers. In some embodiments, the width w3 of the second grating line 308, the width w4 of the second grating space 310 may be numerically optimized to maximize the mode overlap between the optical fiber and the grating coupler assembly 300, thereby generating the maximum coupling efficiency CE and the minimum back reflection loss in a given communication band (e.g., C band). In addition, the number of the second grating lines 308 may also be numerically optimized to maximize the coupling efficiency CE and reduce the back reflection loss.

[0035] In some embodiments, any semiconductor manufacturing technology can be used to manufacture the intermediate etched grating region and the shallow etched grating region. In addition, the grating coupler assembly 300 having two or more etched grating regions can be included in an optical I / O interface module or a high-speed optical communication system.

[0036] Geometric variations resulting from process (lithography / etching) variations can negatively impact the sensitivity of the PIC grating coupler to noise and the coupling efficiency. One exemplary advantage of forming multiple etched grating regions (e.g., intermediate etched grating regions and shallow etched grating regions) in the grating coupler assembly 300 is to reduce the negative impact of geometric variations by simply shifting the operating wavelength of the beam.

[0037] like Figure 3 As shown in , an out-of-plane light beam may be incident on the grating coupler assembly 300 at an incident angle θ. In some embodiments, the out-of-plane light beam incident on the grating coupler assembly 300 may be coupled with the corresponding coupling waveguide under the following conditions:

[0038]

[0039] Where n cladding is the refractive index of the cladding layer of the one or more transparent layers 301, θ is the angle of incidence, n eff is the refractive index of the substrate layer 303 (e.g., silicon layer), λ is the wavelength of the incident out-of-plane beam, a is the grating period 409, and m is an integer representing the diffraction order (equal to 1 for a 1D grating coupler). In addition, the etching depth (e.g., depth H2 and depth H3) may result in n eff More specifically, an increase in etching depth can reduce n eff In some embodiments, by setting the θ incident angle in the range of about 5° to 15°, maximum coupling efficiency with the middle etched grating region and the shallow etched grating region can be achieved.

[0040] Figure 4A Measured coupling loss and back reflection loss 400A are shown for an apodized GC having one grating region with a single level etched grating and with a beam having a wavelength of 1310 nanometers, according to some embodiments. Figure 4AA horizontal axis 403A is shown representing the wavelength of the light beam in nanometers (nm). A vertical axis 402A represents the coupled power in decibels. Solid plotted line 401A represents the coupling loss of the apodized grating coupler. A second solid plotted line 405A represents the silicon waveguide back reflection of the apodized grating coupler. The coupling loss of the example apodized grating coupler embodiment with a single-stage etched grating has a peak value of -3.09 / 2 decibels at the optical wavelength range near 1310 nanometers, as shown by the first solid plotted line 401A. Other embodiments may be designed for other peak wavelengths. The back reflection of the example apodized grating coupler embodiment with a single-stage etched grating depicts a minimum of -25 decibels near 1310 nanometers, as shown by the second solid plotted line 405A. Other embodiments may have minima of different magnitudes at different wavelengths. In various embodiments, the grating coupler may be operated in an over-coupled state where the minimum back reflection wavelength may coincide with or be close to the maximum coupling loss wavelength.

[0041] Figure 4B Measured coupling loss and back reflection loss 400B are shown for an apodized GC having one grating region with two different etch levels and with a beam having a wavelength of 1310 nanometers, according to some embodiments. Figure 4B A horizontal axis 403B is shown representing the wavelength of the light beam in nanometers (nm). A vertical axis 402B represents the coupled power in decibels. A solid plotted line 401B represents the coupling loss of an apodized grating coupler with an intermediate etch level and a shallow etch level. A second solid plotted line 405B represents the back reflection loss of an apodized grating coupler with an intermediate etch and a shallow etch.

[0042] like Figure 4B As shown in , the coupling loss of the example apodized grating coupler embodiment with intermediate etching and shallow etching has a peak value of -2.59 / 2 decibels at the optical wavelength range near 1310 nanometers. Thus, the grating coupler with intermediate etching and shallow etching has improved coupling efficiency at the optical wavelength range near 1310 nanometers compared to the grating coupler with single-stage etched grating. Other embodiments can be designed for other peak wavelengths. The back reflection of the example apodized grating coupler embodiment with intermediate etching and shallow etching shows a minimum value of -36.6 decibels near 1310 nanometers, as shown by the second solid plot line 405B. Thus, the grating coupler with intermediate etching and shallow etching has lower back reflection loss at the optical wavelength range near 1310 nanometers compared to the grating coupler with single-stage etched grating. Other embodiments may have minimum values ​​of different magnitudes at different wavelengths. An exemplary advantage of lower back reflection loss is reduced optical noise and increased optical stability. In addition, lower back reflection reduces the sensitivity of the optical feedback scheme to noise.

[0043] Now turn to reference Figure 5 , a flow chart showing a method for manufacturing an optical grating coupler having an intermediate grating region and a shallow grating region according to some embodiments. The flow charts as shown herein provide examples of sequences of various process actions. Although depicted in a particular sequence or order, the order of the actions may be modified unless otherwise specified. Thus, the illustrated embodiments should be understood as examples only, and the processes may be performed in a different order, and some actions may be performed in parallel. Additionally, in various embodiments of the present invention, one or more actions may be omitted; therefore, not all actions are required in every implementation. Other process flows are possible.

[0044] In some embodiments, the physical layout of the grating coupler can be used to complete and manufacture a photon-enabled integrated circuit using a semiconductor manufacturing process. The physical layout, often referred to as a "geometry," can be used to produce integrated circuit tooling, which is a series of masks that each represent a layer of an integrated circuit. The tooling is then used by a manufacturer to manufacture a photon-enabled integrated circuit.

[0045] thus, Figure 5 Step 501 is shown, where a substrate layer 303 may be formed according to a physical layout grating coupler. In one embodiment, the fabricated substrate layer 303 is a single crystal Si wafer. In other embodiments, the fabricated substrate layer 303 may be an InP wafer.

[0046] At step 503, a plasma etching process (e.g., reactive ion etching) may be used to form an intermediate etched grating region in the substrate layer 303. In other embodiments, a dry etching process may be used to form the intermediate etched grating region. The intermediate etched grating region may include a patterned grating having a width w1 and a width w2 between the patterned gratings. In some embodiments, the width w1 of the patterned grating lines in the intermediate etched region and the width w2 of the open space between the gratings may be uniform. The first height H2 of the grating in the intermediate etched region may be selected based on the expected wavelength of operation of the grating coupler. In a non-limiting embodiment, the first height H2 is preferably in the range of about 70 nanometers to 210 nanometers. Those skilled in the relevant art will appreciate that the first height H2 may vary slightly within the intermediate etched region due to variations in the etching process.

[0047] At step 505, a shallow etched grating region may be formed in the substrate layer 303 using a plasma etching process (e.g., reactive ion etching). In other embodiments, a dry etching process may be used to form the shallow etched grating region. The shallow etched grating region may include a patterned grating having a width w3 and a width w4 between the patterned gratings. In some embodiments, the width w3 of the patterned grating lines in the shallow etched region and the width w4 of the open space between the gratings may be uniform. The second height H3 of the grating in the shallow etched region may be selected based on the expected wavelength of operation of the grating coupler. In a non-limiting embodiment, the second height H3 is preferably in the range of about 100 nanometers to 210 nanometers. Those skilled in the relevant art will appreciate that the second height H3 may vary slightly within the shallow etched region due to variations in the etching process. In further embodiments, three or more grating regions with different grating heights may be etched in the silicon substrate.

[0048] exist Figure 5 In the embodiment, step 507 is shown to form a transparent layer 301 composed of a low refractive index material (such as a SiO2 film) to cover the grating in the middle etched area and the shallow etched area. In some embodiments, the thickness of the covering SiO2 film can be changed for each area of ​​the grating so that the diffraction intensity gradually increases toward the end of the grating coupler.

[0049] Although various embodiments of the present disclosure have been described above, it should be understood that the embodiments have been presented by way of example only and not by way of limitation. Similarly, various diagrams may depict example architectures or configurations, which are provided to enable those of ordinary skill in the art to understand the exemplary features and functions of the present disclosure. However, such technicians will understand that the present disclosure is not limited to the example architectures or configurations shown, but may be implemented using various alternative architectures and configurations. In addition, as those of ordinary skill in the art will understand, one or more features of an embodiment may be combined with one or more features of another embodiment described herein. Therefore, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments.

[0050] It should also be understood that any reference to elements numbered herein using, for example, "first," "second," etc., does not generally limit the number or order of those elements. Indeed, these numbers are used herein as a convenient way to distinguish between two or more than two elements or examples of elements. Thus, a reference to a first element and a second element does not mean that only two elements may be employed or that the first element must precede the second element in a certain manner.

[0051] In addition, those of ordinary skill in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, and symbols such as may be referenced in the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0052] Those of ordinary skill in the art will further appreciate that any of the various illustrative logical blocks, modules, processors, components, circuits, methods, and functions described in conjunction with the various aspects disclosed herein may be implemented by electronic hardware (e.g., digital implementations, analog implementations, or a combination of the two), firmware, various forms of programs or design code incorporating instructions (which, for convenience, may be referred to herein as "software" or "software modules"), or any combination of these technologies.

[0053] To clearly illustrate this interchangeability of hardware, firmware, and software, various illustrative components, blocks, modules, circuits, and steps have been generally described above with respect to their functionality. Whether this functionality is implemented as hardware, firmware, or software or a combination of these technologies depends on the specific application and design constraints imposed on the entire system. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions do not result in departure from the scope of this disclosure. According to various embodiments, processors, devices, components, circuits, structures, machines, modules, etc. may be configured to perform one or more of the functions described herein. As used herein, the term "configured to" or "configured for" relative to a specified operation or function refers to a processor, device, component, circuit, structure, machine, module, signal, etc. that is physically constructed, programmed, arranged, and / or formatted to perform a specified operation or function.

[0054] In addition, it will be understood by those of ordinary skill in the art that the various illustrative logic blocks, modules, devices, components, and circuits described herein may be implemented within or performed by an integrated circuit (IC), which may include a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device or any combination thereof. The logic blocks, modules, and circuits may further include antennas and / or transceivers to communicate with various components within a network or within a device. The processor programmed to perform the functions herein will become a specially programmed or dedicated processor and may be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other suitable configuration to perform the functions described herein.

[0055] If implemented in software, the functions may be stored as one or more instructions or codes on a computer-readable medium. Therefore, the steps of the methods or algorithms disclosed herein may be implemented as software stored on a computer-readable medium. Computer-readable media include both computer storage media and communication media, and the communication media include any media that can enable a computer program or code to be transferred from one place to another. The storage medium may be any available medium that can be accessed by a computer. By way of example and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer.

[0056] In this document, the term "module" as used herein refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. In addition, for the purpose of discussion, various modules are described as discrete modules; however, as will be apparent to one of ordinary skill in the art, two or more modules may be combined to form a single module that performs the associated functions according to embodiments of the present disclosure.

[0057] In some embodiments, a grating coupler includes: a substrate including a silicon wafer; a first grating region etched in the substrate, wherein the first grating region includes a plurality of first gratings having a first predetermined height; and a second grating region etched in the substrate, wherein the second grating region includes a plurality of second gratings having a second predetermined height, wherein the first predetermined height and the second predetermined height are not the same.

[0058] In some embodiments, the first predetermined height is in a range of 70 nanometers to 210 nanometers.

[0059] In some embodiments, the second predetermined height is in the range of 100 nanometers to 210 nanometers.

[0060] In some embodiments, the substrate has a thickness in a range from 200 nanometers to 500 nanometers.

[0061] In some embodiments, the grating coupler further comprises a third grating region etched in the substrate, wherein the third grating region comprises a third plurality of gratings having a third predetermined height different from the first predetermined height and the second predetermined height.

[0062] In some embodiments, the grating coupler is configured to operate around a 1310 nanometer light wavelength.

[0063] In some embodiments, an optical communication system comprises: an optical fiber; and a photonic integrated circuit, comprising a grating coupler assembly, the grating coupler assembly being configured to couple light carried in the optical fiber into or out of the photonic integrated circuit, wherein the grating coupler assembly comprises: a substrate comprising a silicon wafer; a first grating region etched in the substrate, wherein the first grating region comprises a plurality of first gratings having a first predetermined height; and a second grating region etched in the substrate, wherein the second grating region comprises a plurality of second gratings having a second predetermined height, wherein the first predetermined height and the second predetermined height are not the same.

[0064] In some embodiments, the first predetermined height is in a range of 70 nanometers to 210 nanometers.

[0065] In some embodiments, the second predetermined height is in the range of 100 nanometers to 210 nanometers.

[0066] In some embodiments, the substrate has a thickness in a range from 200 nanometers to 500 nanometers.

[0067] In some embodiments, the angle between the optical fiber and a normal to a surface of the grating coupler assembly is in the range of 5° to 15°.

[0068] In some embodiments, the optical communication system is configured to operate around a 1310 nanometer optical wavelength.

[0069] In some embodiments, a method for manufacturing a grating coupler includes: forming a substrate layer; etching a first grating region into the substrate layer, wherein the first grating region includes a plurality of first gratings having a first predetermined height; and etching a second grating region into the substrate layer, wherein the second grating region includes a plurality of second gratings having a second predetermined height, wherein the first predetermined height and the second predetermined height are not the same; and forming a cladding layer including silicon dioxide on the first grating region and the second grating region.

[0070] In some embodiments, the first predetermined height of the plurality of first gratings is in a range of 70 nanometers to 210 nanometers.

[0071] In some embodiments, the second predetermined height of the plurality of second gratings is in the range of 100 nanometers to 210 nanometers.

[0072] In some embodiments, the substrate layer has a thickness in a range of 200 nanometers to 500 nanometers.

[0073] In some embodiments, the method further etches a third grating region into the substrate layer, wherein the third grating region includes a third plurality of gratings having a third predetermined height different from the first predetermined height and the second predetermined height.

[0074] In some embodiments, the plurality of first gratings and the plurality of second gratings have uniform widths.

[0075] In some embodiments, the width of each of the plurality of first gratings and the plurality of second gratings is selected to minimize coupling loss and back reflection loss between the grating coupler and an optical fiber coupled to the grating coupler.

[0076] In some embodiments, the substrate layer is formed of a silicon material.

[0077] Various modifications to the embodiments described in this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the embodiments illustrated herein, but should be given the broadest scope consistent with the novel features and principles disclosed herein.

Claims

1. A grating coupler, comprising: substrates, including silicon wafers; A first grating region is etched in the substrate, wherein the first grating region includes a plurality of first gratings having a first predetermined height and a plurality of first grating spaces; as well as a second grating region etched in the substrate, The second grating region includes a plurality of second gratings having a second predetermined height and a plurality of second grating spaces, wherein the first predetermined height and the second predetermined height are different, The sum of the width of one of the plurality of first gratings and the width of the adjacent first grating space is different from the sum of the width of one of the plurality of second gratings and the width of the adjacent second grating space, wherein the width of one of the plurality of first grating spaces is the same at the bottommost surface and the topmost surface of one of the plurality of first gratings, and the width of one of the plurality of second grating spaces is the same at the bottommost surface and the topmost surface of one of the plurality of second gratings.

2. The grating coupler of claim 1, wherein the first predetermined height is in the range of 70 nanometers to 210 nanometers.

3. The grating coupler of claim 1, wherein the second predetermined height is in the range of 100 nanometers to 210 nanometers.

4. The grating coupler of claim 1, wherein a thickness of the substrate is in a range of 200 nanometers to 500 nanometers.

5. The grating coupler of claim 1, further comprising a third grating region etched in the substrate, wherein the third grating region comprises a third plurality of gratings having a third predetermined height different from the first predetermined height and the second predetermined height.

6. The grating coupler of claim 1, configured to operate around a 1310 nanometer optical wavelength.

7. An optical communication system, comprising: optical fiber; as well as A photonic integrated circuit comprising a grating coupler assembly configured to couple light carried in the optical fiber into or out of the photonic integrated circuit, wherein the grating coupler assembly comprises: substrates, including silicon wafers; a first grating region, etched in the substrate, wherein the first grating region includes a plurality of first gratings having a first predetermined height and a plurality of first grating spaces; as well as a second grating region, etched in the substrate, The second grating region includes a plurality of second gratings having a second predetermined height and a plurality of second grating spaces, wherein the first predetermined height and the second predetermined height are different, The sum of the width of one of the plurality of first gratings and the width of the adjacent first grating space is different from the sum of the width of one of the plurality of second gratings and the width of the adjacent second grating space, wherein the width of one of the plurality of first grating spaces is the same at the bottommost surface and the topmost surface of one of the plurality of first gratings, and the width of one of the plurality of second grating spaces is the same at the bottommost surface and the topmost surface of one of the plurality of second gratings.

8. The optical communication system according to claim 7, wherein the first predetermined height is in the range of 70 nanometers to 210 nanometers.

9. The optical communication system according to claim 7, wherein the second predetermined height is in the range of 100 nanometers to 210 nanometers.

10. The optical communication system according to claim 7, wherein a thickness of the substrate is in a range of 200 nanometers to 500 nanometers.

11. The optical communication system of claim 7, wherein an angle between the optical fiber and a normal to a surface of the grating coupler assembly is in the range of 5° to 15°.

12. The optical communication system of claim 7, wherein the optical communication system is configured to operate around a 1310 nanometer optical wavelength.

13. A method for manufacturing a grating coupler, comprising: forming a substrate layer; etching a first grating region into the substrate layer, wherein the first grating region includes a plurality of first gratings having a first predetermined height and a plurality of first grating spaces; as well as etching a second grating region into the substrate layer, The second grating region includes a plurality of second gratings having a second predetermined height and a plurality of second grating spaces, wherein the first predetermined height and the second predetermined height are different, wherein the sum of the width of one of the plurality of first gratings and the width of the adjacent first grating space is different from the sum of the width of one of the plurality of second gratings and the width of the adjacent second grating space, wherein the width of the one of the plurality of first grating spaces is the same at the bottommost surface and the topmost surface of the one of the plurality of first gratings, and the width of the one of the plurality of second grating spaces is the same at the bottommost surface and the topmost surface of the one of the plurality of second gratings; and A cladding layer including silicon dioxide is formed on the first grating region and the second grating region. 14 . The method for manufacturing a grating coupler according to claim 13 , wherein the first predetermined height of the plurality of first gratings is in a range of 70 nanometers to 210 nanometers. 15 . The method for manufacturing a grating coupler according to claim 13 , wherein the second predetermined height of the plurality of second gratings is in the range of 100 nanometers to 210 nanometers.

16. The method for manufacturing a grating coupler according to claim 13, wherein a thickness of the substrate layer is in a range of 200 nanometers to 500 nanometers. 17 . The method for manufacturing a grating coupler according to claim 13 , further comprising etching a third grating region into the substrate layer, wherein the third grating region comprises a third plurality of gratings having a third predetermined height different from the first predetermined height and the second predetermined height.

18. The method for manufacturing a grating coupler according to claim 13, wherein the plurality of first gratings and the plurality of second gratings have uniform widths.

19. The method for manufacturing a grating coupler according to claim 13, wherein a width of each of the plurality of first gratings and the plurality of second gratings is selected to minimize coupling loss and back reflection loss between the grating coupler and an optical fiber coupled to the grating coupler.

20. The method for manufacturing a grating coupler according to claim 13, wherein the substrate layer is formed of a silicon material.

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