Optical module

Abstract

The embodiment of the utility model provides an optical module. The optical module comprises a substrate; a first grating coupler overlying the substrate; and a second grating coupler overlying the first grating coupler, where the second grating coupler is configured to receive a first lateral mode of the input optical signal and to pass a second lateral mode of the input optical signal to the first grating coupler, and wherein the first grating coupler is configured to receive a second lateral mode of the input optical signal.

Description

Technical Field

[0001] The embodiment of the utility model relates to an optical module. Background Art

[0002] Optical couplers (e.g., grating couplers and edge couplers) are commonly used as components in photonic integrated circuits (PICs) that integrate multiple photonic functions. Optical couplers are used to confine and guide light from optical fibers to integrated chips with minimal attenuation. Grating couplers are more compact than edge couplers and allow for greater variation in coupling positions. Edge couplers have higher coupling efficiency and wider bandwidth than grating couplers. Utility Model Content

[0003] An embodiment of the utility model provides an optical module, comprising: a substrate; a first grating coupler overlying the substrate; and a second grating coupler overlying the first grating coupler, wherein the second grating coupler is configured to receive a first transverse mode of an input optical signal and transmit a second transverse mode of the input optical signal to the first grating coupler, and wherein the first grating coupler is configured to receive the second transverse mode of the input optical signal.

[0004] An embodiment of the utility model provides an optical module, comprising: a substrate; a first grating coupler overlying the substrate, wherein the first grating coupler comprises a plurality of first grating lines laterally adjacent to a first tapered segment, wherein the plurality of first grating lines have a first grating period; and a second grating coupler overlying the substrate and adjacent to the first grating coupler, wherein the second grating coupler comprises a plurality of second grating lines laterally adjacent to a second tapered segment, wherein the plurality of second grating lines have a second grating period different from the first grating period, and wherein a distance between the first grating coupler and the second grating coupler is less than a length of the first grating coupler.

[0005] In order to make the above features and advantages of the embodiments of the present invention more obvious and easy to understand, embodiments are specifically cited below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] When read in conjunction with the accompanying drawings, the various aspects of the present disclosure will be best understood from the following detailed description. It is worth noting that, in accordance with standard practice in the industry, the various features are not drawn to scale. In fact, the size of the various features may be arbitrarily increased or decreased for clarity of discussion.

[0007] Figure 1A-1B Various views of some embodiments of an optical module having a second grating coupler overlying a first grating coupler according to the present disclosure are shown.

[0008] Figure 2A-2E A method of manufacturing a plurality of grating couplers having a first plurality of grating couplers and a second plurality of grating couplers is shown. Figure 1A Cross-sectional views of some alternative embodiments of optical modules.

[0009] Figures 3A-3L Cross-sectional views of some alternative embodiments of optical modules are shown.

[0010] Figures 4A-4B A cross-sectional view of an optical module with extended grating lines is shown.

[0011] Figure 5 A top view of the optical module is shown overlaid with the light field emerging from the fiber waveguide.

[0012] Figure 6A-6B , 7A-7B, 8A-8B, 9A-9B, 10A-10B, 11A-11B, 12A-12B, 13A-13B, 14A-14D and 15A-15B show cross-sectional views of some embodiments of methods of forming an optical module having multiple grating couplers and optical combiners.

[0013] Figures 16A-16B , 17A-17B, 18A-18B and 19A-19B show combinations for forming a second plurality of grating couplers Figure 6A-6B , 7A-7B, 8A-8B, 9A-9A, 10A-10B, 11A-11B, 12A-12B, 13A-13B, 14A-14D and some embodiments of the continuation of the method described in 15A-15B.

[0014] Fig. 20 A flow chart illustrating some embodiments of a method for forming an optical module having a plurality of grating couplers and optical combiners.

[0015] Description of reference numerals:

[0016] 100a, 200a, 200b, 300g, 300k, 300l, 500, 600b, 700b, 800b, 900b, 1000b, 1100b, 1200b, 1300b, 1400a, 1500b, 1600b, 1700b, 1800b, 1900b: Top view

[0017] 100b, 200c, 200d, 200e, 300a, 300b, 300c, 300d, 300e, 300f, 300h, 300i, 300j, 400a, 400b, 600a, 700a, 800a, 900a, 1000a, 1100a, 1200a, 1300a, 1400b, 1400c, 1400d, 1500a, 1600a, 1700a, 1800a, 1900a: cross-sectional view

[0018] 102: Substrate

[0019] 104: First grating coupler

[0020] 105: Second grating coupler

[0021] 106: The First Dielectric

[0022] 108: Mirror

[0023] 110: The third dielectric

[0024] 111: Second dielectric

[0025] 112: The Fourth Dielectric

[0026] 112a: First spacing

[0027] 112b: Second spacing

[0028] 112c: Third pitch

[0029] 112d: Fourth spacing

[0030] 112e: Fifth pitch

[0031] 112f: Sixth pitch

[0032] 114a: First working cycle

[0033] 114b: Second working cycle

[0034] 114c: Third working cycle

[0035] 114d: Fourth working cycle

[0036] 114e: Fifth working cycle

[0037] 114f: Sixth working cycle

[0038] 116a: First grating period

[0039] 116b: Second grating period

[0040] 116c: Third grating period

[0041] 116d: Fourth grating period

[0042] 116e: Fifth grating period

[0043] 116f: Sixth grating period

[0044] 120: First Waveguide

[0045] 122: Second waveguide

[0046] 125: Tapering section

[0047] 126: Raster lines

[0048] 126a, 126f: first grating line

[0049] 126b: Second grating line

[0050] 126s: adjacent grating lines

[0051] 1002: First mask layer

[0052] 1102: First Etching

[0053] 1104: First Opening

[0054] 1302: Second mask layer

[0055] 1402: Second Etching

[0056] 1602: Second grating coupler precursor

[0057] 1702: Third mask layer

[0058] 1802: The Third Etching

[0059] 201: First multiple grating coupler

[0060] 202: The third grating coupler

[0061] 204: Fourth grating coupler:

[0062] 205, 210: Optical combiner

[0063] 206: Fifth grating coupler

[0064] 208: Sixth grating coupler

[0065] 212: Grating substrate

[0066] 214: Length

[0067] 218: The Fifth Waveguide

[0068] 220: The Sixth Waveguide

[0069] 222: The Third Waveguide

[0070] 224: The Fourth Waveguide:

[0071] 228: Input / output waveguide

[0072] 229: Distance

[0073] 231: Second multiple grating coupler

[0074] 2000: Methods

[0075] 2002, 2004, 2006, 2008, 2010, 2012, 2014: Step 302: Electromagnetic input signal

[0076] 306: The Fifth Dielectric

[0077] 308: Lens

[0078] 312: First Mode Section

[0079] 314: Second Mode Section

[0080] 322: First thickness

[0081] 324: The third thickness

[0082] 326: Second thickness

[0083] 328: Fourth thickness

[0084] 330: Fifth thickness

[0085] 332a, 334a: Outermost working cycle

[0086] 332b, 334b: Innermost working cycle

[0087] 336: Part 1

[0088] 338: Part 2

[0089] 340: Part 3

[0090] 342: Gaussian distribution

[0091] 406: Polysilicon layer

[0092] 502: Fiber Optic Cable

[0093] 504: First mode light field

[0094] 506: Second mode light field

[0095] 902: First grating coupler precursor

[0096] A-A', B-B', C-C': Line

[0097] D1, D2, D3, D4: Apodization etching depth

[0098] H1: First height

[0099] H2: Second height

[0100] H3: The third height

[0101] H4: The fourth height

[0102] λ1: First central wavelength

[0103] λ2: Second central wavelength

[0104] λ3: The third central wavelength DETAILED DESCRIPTION

[0105] The present disclosure provides many different embodiments or examples for implementing the different features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, these are only examples and are not intended to be limiting. For example, in the following description, the formation of a feature over or on a second feature may include an embodiment in which a first feature and a second feature are formed in direct contact, and may also include an embodiment in which an additional feature may be formed between the first feature and the second feature so that the first feature and the second feature may not be in direct contact. In addition, the present disclosure may repeat reference numerals and / or letters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or configurations discussed.

[0106] Furthermore, to facilitate description of the relationship of one component or feature to another component or feature as illustrated in the figures, spatially relative terms may be used herein, for example, "beneath," "lower," "above," "upper," etc. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0107] Photonic integrated circuits (PICs) use optical signals (e.g., electromagnetic waves) to provide high-speed signal communications. The use of optical signals provides lower power consumption and generates less heat than electrical signals. PICs receive optical signals through optical modules such as grating couplers and edge couplers. Edge couplers have higher coupling efficiency and wider bandwidth than grating couplers, although they are most effective when placed at the edge of the chip and take up more space than grating couplers. Compared to edge couplers, grating couplers have a more compact design and can be placed in more locations on the chip, but generally have lower coupling efficiency, lower alignment tolerance, and lower bandwidth than edge couplers.

[0108] For example, a grating coupler can be polarization sensitive and can be configured to efficiently receive a transverse electric (TE) mode (e.g., an electric field component) or a transverse magnetic (TM) mode (e.g., a magnetic field component) of an input optical signal, while not receiving other signals. This can result in lower coupling efficiency due to energy loss in the unreceived modes. Grating couplers also have low alignment tolerance because the alignment of the optical fiber used to transmit the input optical signal can rotate the input optical signal, thereby shifting the central wavelength of the input optical signal. Furthermore, the narrow bandwidth of the grating coupler combined with the shift in the central wavelength can cause the input optical signal to be misaligned with the peak of the bandwidth, thereby reducing the coupling efficiency. An optical module with higher alignment tolerance, higher bandwidth, and higher coupling efficiency that is not subject to the placement constraints and footprint of edge couplers is needed.

[0109] The present disclosure provides an optical module, comprising a first grating coupler and a second grating coupler overlying the first grating coupler. The first grating coupler is configured to receive a first transverse mode (e.g., TE mode) of an input optical signal, and the second grating coupler is configured to receive a second transverse mode (e.g., TM mode) of the input optical signal. This combination of grating couplers results in higher coupling efficiency between the PIC and the optical fiber, because both the TE mode signal and the TM mode signal can be captured by the optical module.

[0110] In some embodiments, a first plurality of grating couplers and a second plurality of grating couplers including two or more grating couplers replace the first grating couplers and the second grating couplers to improve alignment tolerance, coupling efficiency, and bandwidth. By arranging the first plurality of grating couplers having partially overlapping bandwidths and coupling the grating couplers to an optical combiner, the bandwidth of the optical module can be increased. The grating couplers of the optical module are configured to receive input optical signals from a single optical fiber due to their proximity to each other, and a bandwidth variation on the grating couplers results in an increased bandwidth compared to another optical module having a single grating coupler. Furthermore, the bandwidth of the optical module maintains a loss of 1 dB or less over the increased bandwidth. The increased bandwidth of the optical module is conducive to effectively receiving input optical signals having a wide range of central wavelengths, thereby improving the alignment tolerance of the optical module.

[0111] Figure 1A-1B Various views of some embodiments of an optical module having a second grating coupler overlying a first grating coupler according to the present disclosure are shown. Figure 1A A top view 100a of some embodiments of an optical module is shown. Figure 1B Shown along Figure 1A A cross-sectional view 100b of some embodiments of an optical module taken along line AA' is also described. Figure 1A-1B .

[0112] The optical module includes a first grating coupler 104 on a substrate 102. A second grating coupler 105 overlies the first grating coupler 104. The first grating coupler 104 and the second grating coupler 105 include first grating lines 126a and second grating lines 126b, wherein the first grating lines 126a and the second grating lines 126b are bent to guide the input optical signal to the first waveguide 120 and the second waveguide 122, respectively. In various embodiments, the first grating lines 126a and the second grating lines 126b of the first grating coupler 104 and the second grating coupler 105 may be straight (not shown).

[0113] The first grating coupler 104 and the second grating coupler 105 each include a tapered section 125 laterally adjacent to the corresponding grating line 126. In various embodiments, the width of the tapered section 125 decreases continuously when viewed from the grating line 126 toward the first waveguide 120 and the second waveguide 122 in a top view.

[0114] The first grating coupler 104 is separated from the substrate 102 by a first dielectric 106 and a mirror 108. The mirror 108 is configured to reflect the optical signal transmitted through the grating coupler back to the grating coupler to increase the coupling efficiency. The second dielectric 111 surrounds the outer side wall of the first grating coupler 104, and the third dielectric 110 overlies the first grating coupler 104. The fourth dielectric 112 overlies the second grating coupler 105. In some embodiments, the first dielectric 106, the second dielectric 111, the third dielectric 110, and the fourth dielectric 112 are or include dielectric materials, such as silicon dioxide (SiO2) and the like.

[0115] The first grating coupler 104 includes a first grating period 116a (e.g., the distance between the start of a first grating line and the start of a subsequent grating line), a first pitch 112a (e.g., the distance between the end of the first grating line and the start of a subsequent grating line), and a first duty cycle 114a (e.g., the proportion of the grating period occupied by the first grating line). In some embodiments, the first grating period 116a corresponds to the distance from the outer sidewall of the first grating line 126f to the outer sidewall of the adjacent grating line 126s. The effective refractive index of the first grating coupler 104 is based at least in part on the first duty cycle 114a and the first pitch 112a. The first center wavelength λ1 (not shown) of the first grating coupler 104 is based at least in part on the first grating period 116a and / or the effective refractive index of the first grating coupler 104. In various embodiments, the first grating coupler 104 has a first bandwidth, which may be, for example, about 40 nanometers (nm) or another value. In some embodiments, the upper wavelength limit of the first bandwidth is λ1+x / 2 (where x is the first bandwidth of the first grating coupler 104), and the lower wavelength limit of the first bandwidth is λ1-x / 2. In other embodiments, the first center wavelength λ1 of the first grating coupler 104 is equal to the resonant wavelength of the first grating coupler 104. In still other embodiments, the first center wavelength λ1 may correspond to the center wavelengths of multiple grating couplers.

[0116] The second grating coupler 105 has a second duty cycle 114b, a second spacing 112b, and a second grating period 116b. The second duty cycle 114b and the second spacing 112b configure the effective refractive index of the second grating coupler 105. In some embodiments, the fourth grating period 116d and / or the effective refractive index configure the center wavelength of the second grating coupler 105 so that the bandwidth of the second grating coupler 105 is approximately the same as the bandwidth of the first grating coupler 104. In various embodiments, the second duty cycle 114b and / or the second spacing 112b are different from the first duty cycle 114a and / or the first spacing 112a of the first grating coupler 104 so that the second grating coupler 105 has a different effective refractive index than the first grating coupler 104. In other embodiments, the second grating period 116b is different from the first grating period 116a to configure the center wavelength of the second grating coupler 105.

[0117] In some embodiments, the first grating coupler 104 is configured to receive a first transverse mode of the optical signal (e.g., one of the TE mode or the TM mode). The second grating coupler 105 is configured to receive a second transverse mode of the optical signal (e.g., if the first mode is the TE mode, the second transverse mode is the TM mode, or if the first mode is the TM mode, the second transverse mode is the TE mode). For example, when an unpolarized input signal is provided to the optical module at a first angle, the first grating coupler 104 is configured to receive a first transverse mode portion of the unpolarized input signal, and the second grating coupler 105 is configured to receive a second transverse mode portion of the unpolarized input signal. This configuration allows the optical module to couple to multiple modes while maintaining the inherent placement flexibility of the grating coupler.

[0118] The effective refractive index that affects the reception of TE mode signals and TM mode signals is different in the grating coupler. For example, the grating coupler may have a first effective refractive index that changes the reception of TE mode signals and a second effective refractive index that changes the reception of TM mode signals. The effective refractive index is based at least in part on the spacing of the grating lines of the grating coupler. The period of the grating lines (e.g., the distance between the start of a first grating line and the start of a subsequent grating line) combined with the effective refractive index can define the center wavelength of the bandwidth of the grating coupler. Therefore, the first grating period 116a of the first grating coupler 104 is configured to receive an optical signal of a first mode, wherein the optical signal of the first mode is at a different frequency close to the center wavelength of the first grating coupler 104. The second grating period 116b of the second grating coupler 105 is configured to receive an optical signal of a second mode, wherein the optical signal of the second mode is at a different frequency close to the center wavelength of the second grating coupler 105.

[0119] Figure 2A-2EA method of manufacturing a plurality of grating couplers having a first plurality of grating couplers and a second plurality of grating couplers is shown. Figure 1A Cross-sectional views of some alternative embodiments of optical modules. Figure 2A A top view 200a of some embodiments of an optical module flush with a first plurality of grating couplers is shown. Figure 2B A top view 200b of some embodiments of an optical module flush with a second plurality of grating couplers is shown. Figure 2C Shown along Figure 2A and 2B A cross-sectional view 200c of some embodiments of an optical module taken along line AA′. Figure 2D Shown along Figure 2A and 2B A cross-sectional view 200d of some embodiments of an optical module taken along line BB′. Figure 2E Shown along Figure 2A and 2B A cross-sectional view 200e of some embodiments of an optical module taken along line CC'.

[0120] In some embodiments, the optical module includes a first plurality of grating couplers 201. The first plurality of grating couplers 201 include a first grating coupler 104, a third grating coupler 202, and a fourth grating coupler 204 that are close to each other. The first grating coupler 104, the third grating coupler 202, and the fourth grating coupler 204 are coupled to an optical combiner 205 by a first waveguide 120, a third waveguide 222, and a fourth waveguide 224, respectively. The first grating coupler 104, the third grating coupler 202, and the fourth grating coupler 204 include grating lines 126, wherein the grating lines 126 are bent to guide the input optical signal to the first waveguide 120, the third waveguide 222, and the fourth waveguide 224, respectively.

[0121] The first waveguide 120 branches from the optical combiner 205 in a first direction toward the first grating coupler 104, and optically couples the first grating coupler 104 to the optical combiner 205. The third waveguide 222 branches from the optical combiner 205 in a second direction toward the third grating coupler 202, and optically couples the third grating coupler 202 to the optical combiner 205. The fourth waveguide 224 branches from the optical combiner 205 in a third direction toward the fourth grating coupler 204, and optically couples the fourth grating coupler 204 to the optical combiner 205. In various embodiments, the first direction, the second direction, and the third direction are different from each other. The first grating coupler 104, the third grating coupler 202, and the fourth grating coupler 204 are configured to each receive a separate input optical signal and / or are configured to receive different portions of the input optical signal. The optical signals input to the first grating coupler 104, the third grating coupler 202, and the fourth grating coupler 204 are transmitted to the optical combiner 205 through the first waveguide 120, the third waveguide 222, and the fourth waveguide 224. The optical combiner 205 is configured to combine the optical signals into a combined optical signal that is delivered to an input / output (I / O) waveguide 228.

[0122] like Figure 2B As shown, in some embodiments, the second plurality of grating couplers 231 overlie the first plurality of grating couplers 201 (see Figure 2A ). The second plurality of grating couplers 231 include the second grating coupler 105, the fifth grating coupler 206 and the sixth grating coupler 208. The second grating coupler 105, the fifth grating coupler 206 and the sixth grating coupler 208 are coupled to the optical combiner 210 by the second waveguide 122, the fifth waveguide 218 and the sixth waveguide 220, respectively. The fourth dielectric 112 covers the second plurality of grating couplers 231.

[0123] In some embodiments, the length 214 of the tapered section 125 of the second grating coupler 105 is between about 20 and 50 microns, between about 15 and 40 microns, between about 25 and 60 microns, etc. The tapered section 125 may be between 30% and 70% of the length 214 of the second grating coupler 105. The first grating coupler 104, the third grating coupler 202, the fourth grating coupler 204, the fifth grating coupler 206, and the sixth grating coupler 208 also have tapered sections 125, wherein the length of the tapered sections 125 is within the same numerical range as the length 214. In some embodiments, the distance 229 between the second grating coupler 105 and the fifth grating coupler 206 is less than the length of the second grating coupler 105.

[0124] like Figure 2CAs shown, in some embodiments, the first plurality of grating couplers (see Figure 2A 201) includes first grating lines 126a extending from the grating substrate 212 when viewed from a cross-sectional view. The height of the first grating lines 126a is approximately 20% to 80% of the thickness of the first grating coupler 104. In some embodiments, the second plurality of grating couplers 231 have second grating lines 126b that are physically isolated from each other. That is, when the second plurality of grating couplers 231 are formed, and when viewed from a cross-sectional view, the second waveguide precursor is completely etched through and the dielectric material completely surrounds the second grating lines 126b. In some embodiments, the distance between the first grating coupler 104 and the second grating coupler 105 is less than the length of the first grating coupler 104.

[0125] like Figure 2D As shown, the third grating coupler 202 includes grating lines 126 having a third duty cycle 114c, a third spacing 112c, and a third grating period 116c. The effective refractive index of the third grating coupler 202 is based at least in part on the third duty cycle 114c and the third spacing 112c. The second center wavelength λ2 (not shown) of the third grating coupler 202 is based at least in part on the third grating period 116c and / or the effective refractive index of the third grating coupler 202. In various embodiments, the effective refractive index and / or the third grating period 116c of the third grating coupler 202 are different from the effective refractive index and / or the first grating period 116a of the first grating coupler 104, so that the range of the second bandwidth of the third grating coupler 202 at least partially overlaps or approaches the first outer wavelength limit (first outer wavelength limit) of the first bandwidth of the first grating coupler 104 (e.g., the upper wavelength limit of the first bandwidth). For example, the second center wavelength λ2 may be equal to λ1+x (where x is the first bandwidth of the first grating coupler 104). In various embodiments, the upper wavelength limit of the second bandwidth may be approximately λ2+x / 2, and the lower wavelength limit of the second bandwidth may be approximately λ2-x / 2. In other embodiments, the second center wavelength λ2 of the third grating coupler 202 is equal to the resonant wavelength of the third grating coupler 202 .

[0126] The fifth duty cycle 114e and / or the fifth spacing 112e of the fifth grating coupler 206 configure the effective refractive index of the fifth grating coupler 206. The fifth grating period 116e and / or the effective refractive index configure the central wavelength of the fifth grating so that the bandwidth of the fifth grating coupler 206 matches the bandwidth of the second grating coupler 105. Therefore, in order to make the bandwidth of the fifth grating coupler 206 different from the bandwidth of the second grating coupler 105, the fifth grating period 116e and / or the effective refractive index of the fifth grating coupler 206 are different from the effective refractive index of the second grating period 116b and / or the second grating coupler 105.

[0127] like Figure 2E As shown, the fourth grating coupler 204 includes grating lines 126 having a fourth duty cycle 114d, a fourth spacing 112d, and a fourth grating period 116d. The effective refractive index of the fourth grating coupler 204 is based at least in part on the fourth duty cycle 114d and the fourth spacing 112d. The third center wavelength λ3 (not shown) of the fourth grating coupler 204 is based at least in part on the fourth grating period 116d and / or the effective refractive index of the fourth grating coupler 204. In various embodiments, the effective refractive index and / or the fourth grating period 116d of the fourth grating coupler 204 are different from the effective refractive index and / or the first grating period 116a of the first grating coupler 104, so that the range of the third bandwidth of the fourth grating coupler 204 at least partially overlaps or approaches the second outer wavelength limit of the first bandwidth of the first grating coupler 104 (e.g., the lower wavelength limit of the first bandwidth). For example, the third center wavelength λ3 may be equal to λ1-x (where x is the first bandwidth of the first grating coupler 104). In various embodiments, the upper wavelength limit of the third bandwidth is λ3+x / 2, and the lower wavelength limit of the third bandwidth is λ3-x / 2. In further embodiments, the third center wavelength λ3 of the fourth grating coupler 204 is equal to the resonant wavelength of the fourth grating coupler 204. In various embodiments, the effective total bandwidth of the first plurality of grating couplers 201 is equal to the sum of the bandwidths of the first grating couplers 104, the third grating couplers 202, and the fourth grating couplers 204. Therefore, the bandwidth of the first plurality of grating couplers 201 combined with the proximity of the first plurality of grating couplers 201 to each other and coupled to the optical combiner 205 enables the optical module to pass an input optical signal from an optical fiber, wherein the total bandwidth of the optical fiber is two to four times greater than that of a single grating coupler (e.g., greater than the first bandwidth of the first grating coupler 104). Therefore, the coupling efficiency and overall performance of the optical module are increased.

[0128] The sixth duty cycle 114f and the sixth spacing 112f of the sixth grating coupler 208 configure the effective refractive index of the sixth grating coupler 208. The sixth grating period 116f configures the central wavelength of the sixth grating coupler 208 so that the bandwidth of the sixth grating coupler 208 matches the bandwidth of the fourth grating coupler 204. Therefore, in order to make the bandwidth of the sixth grating coupler 208 different from the bandwidth of the second grating coupler 105, the effective refractive index of the sixth grating period 116f and / or the sixth grating coupler 208 is different from the effective refractive index of the second grating period 116b and / or the second grating coupler 105.

[0129] In some embodiments, the first grating coupler 104, the third grating coupler 202, and the fourth grating coupler 204 are configured to receive a first transverse mode of the optical signal (e.g., one of the TE mode or the TM mode). The second grating coupler 105, the fifth grating coupler 206, and the sixth grating coupler 208 are configured to receive a second transverse mode of the optical signal (e.g., if the first mode is the TE mode, the second transverse mode is the TM mode, or if the first mode is the TM mode, the second transverse mode is the TE mode). For example, when an unpolarized input signal is provided to the optical module at a first angle, the first plurality of grating couplers 201 (see Figure 2A ) is configured to receive a first transverse mode portion of an unpolarized input signal, and a second plurality of grating couplers 231 is configured to receive a second transverse mode portion of an unpolarized input signal. This configuration allows the optical module to couple to multiple modes while maintaining the inherent placement flexibility of the grating couplers.

[0130] The effective refractive index that affects the reception of TE mode signals and TM mode signals is different in the grating coupler. For example, the grating coupler may have a first effective refractive index that changes the reception of TE mode signals and a second effective refractive index that changes the reception of TM mode signals. The effective refractive index is based at least in part on the spacing of the grating lines of the grating coupler. The period of the grating lines (e.g., the distance between the start of a first grating line and the start of a subsequent grating line) combined with the effective refractive index can define the center wavelength of the bandwidth of the grating coupler.

[0131] Therefore, the first grating period 116a, the third grating period 116c and the fourth grating period 116d of the first grating coupler 104, the third grating coupler 202 and the fourth grating coupler 204 are respectively configured to receive an optical signal of a first mode, wherein the optical signal of the first mode is at a different frequency close to the central wavelength of the first grating coupler 104. The second grating period 116b, the fifth grating period 116e and the sixth grating period 116f of the second grating coupler 105, the fifth grating coupler 206 and the sixth grating coupler are respectively configured to receive an optical signal of a second mode, wherein the optical signal of the second mode is at a different frequency close to the central wavelength of the second grating coupler 105.

[0132] Figures 3A-3L Cross-sectional views 300a-3001 of some alternative embodiments of optical modules are shown.

[0133] like Figure 3A As shown in the cross-sectional view 300a of FIG. 3 , the electromagnetic input signal 302 is directed to the first grating coupler 104 and the second grating coupler 105. In some embodiments, the first mode portion 312 of the electromagnetic input signal 302 is coupled to the second grating coupler 105, and the second mode portion 314 of the electromagnetic input signal 302 passes through the second grating coupler 105 to the first grating coupler 104. Portions of the electromagnetic input signal 302 may also be coupled to the second grating coupler, the third grating coupler, the fifth grating coupler, and the sixth grating coupler (see FIG. 3 ). Figure 2A and 2B 202, 204, 206 and 208).

[0134] In some embodiments, the first plurality of grating couplers 201 (see Figure 2A ) and a second plurality of grating couplers 231 (see Figure 2B ) may be apodized (e.g., having first and second grating lines 126a, 126b with different duty cycles or periods). An apodized grating coupler may have a higher coupling efficiency than a grating coupler with a uniform duty cycle. Figure 3A As shown, the outermost duty cycle 332a of the first grating line 126a may be higher than the innermost duty cycle 332b of the innermost grating line. Figure 3BAs shown in the cross-sectional view 300b of FIG. 1 , the outermost duty cycle 332a of the first grating coupler 104 may be greater than the innermost duty cycle 332b, and the outermost duty cycle 334a of the second grating coupler 105 may be smaller than the innermost duty cycle 334b. The first duty cycle 114a and the second duty cycle 114b or the first grating period 116a and the second grating period 116b may be distributed according to a linear scale, an exponential scale, a Gaussian distribution, etc. In some embodiments, as Figure 3C As shown in the cross-sectional view 300c of FIG. 300, the second duty cycle 114b and the second grating period 116b of the second grating coupler 105 may increase and decrease at various intervals throughout the second grating coupler 105. For example, the second grating period 116b or the second duty cycle 114b may be maximum toward the center of the second grating coupler 105, but may be minimum for the second grating line 126b at the edge of the second grating coupler 105. The duty cycles and periods of the first grating coupler 104, the third grating coupler 202, the fourth grating coupler 204, the fifth grating coupler 206, and the sixth grating coupler may also increase and decrease in a similar manner to the second grating coupler 105.

[0135] like Figure 3C As shown in the cross-sectional view 300c of , in some embodiments, the second grating coupler 105 has a first thickness 322, wherein the first thickness 322 is approximately between 50 and 1000 nanometers, approximately between 40 and 800 nanometers, approximately between 60 and 1200 nanometers, or in another suitable range. The fifth grating coupler 206 and the sixth grating coupler 208 have a thickness equal to the first thickness 322. In some embodiments, the first grating coupler 104 has a second thickness 326, wherein the second thickness 326 is approximately between 50 and 1000 nanometers, approximately between 40 and 800 nanometers, approximately between 60 and 1200 nanometers, or in another suitable range. The third grating coupler 202 and the fourth grating coupler 204 have a thickness equal to the second thickness 326. In some embodiments, the third dielectric 110 has a third thickness 324, wherein the third thickness 324 is measured between the bottom surface of the second grating coupler 105 and the top surface of the first grating coupler 104, and the third thickness 324 is between about 0 and 6 microns, between about 1 and 8 microns, between about 0 and 4 microns, or within another suitable range. In some embodiments, the first dielectric 106 has a fourth thickness 328, wherein the fourth thickness 328 is between about 2 and 6 microns, between about 1 and 5 microns, between about 3 and 7 microns, or within another suitable range. In some embodiments, the third thickness between the first grating coupler 104 and the second grating coupler 105 is less than the length of the first grating coupler 104.

[0136] like Figure 3D As shown in the cross-sectional view 300d of FIG. 300 , in some embodiments, a lens 308 (e.g., a microlens) is located between the first grating coupler 104 and the second grating coupler 105. The lens 308 is surrounded by the fifth dielectric 306. The lens 308 can guide the second mode portion 314 of the electromagnetic input signal 302 to the optimal position in the first grating coupler 104, thereby increasing the coupling efficiency. In some embodiments, the lens 308 includes silicon dioxide (SiO2), polysilicon, etc. In some embodiments, when the lens 308 includes silicon dioxide, the silicon dioxide of the lens 308 has a different crystal structure from the silicon dioxide of the third dielectric 110 due to being formed under different temperature and pressure conditions. In some embodiments, the lens 308 has a radius of curvature, wherein the radius of curvature is approximately between 100 and 600 microns, approximately between 80 and 500 microns, approximately between 120 and 700 microns, or in another suitable range. In some embodiments, the fifth thickness 330 measured between the bottom surface of the second grating coupler 105 and the top surface of the first grating coupler 104 is between approximately 100 and 1000 microns, between approximately 80 and 800 microns, between approximately 120 and 1200 microns, or in another suitable range.

[0137] like Figure 3E As shown in the cross-sectional view 300e of FIG. 3 , the first plurality of grating couplers 201 (see FIG. 3 ) including the first grating coupler 104 Figure 2A ) may have apodized grating line heights H1, H2, H3, and H4 (e.g., the grating lines have heights that vary from one grating coupler to another). For example, a grating line close to the center of the plurality of grating lines may have a first height H1, while the surrounding grating lines may sequentially have a second height H2 that is less than the first height H1, a third height H3 that is less than the second height H2, and a fourth height H4 that is less than the third height H3. In some embodiments, the apodized grating line heights H1, H2, H3, and H4 may have a Gaussian distribution 342. In other embodiments, the heights of the grating lines may be arranged by different patterns. The apodized grating line heights may further increase the coupling efficiency of the first grating coupler 104, and may be used in conjunction with, for example, Figures 3A-3C The duty cycle or period apodization discussed is used in conjunction with the third grating coupler (see Figure 2A 202) and the fourth grating coupler (see Figure 2A 204) may additionally have a variable grating line height.

[0138] like Figure 3F As shown in the cross-sectional view 300f of FIG. 1 , in some embodiments, the first plurality of grating couplers 201 (see FIG. 1 ) Figure 2A) may have apodized etch depths D1, D2, D3, and D4 instead of having apodized grating line heights. The apodized etch depths D1, D2, D3, and D4 may increase the coupling efficiency of the first plurality of grating couplers. In some embodiments, the apodized etch depths D1, D2, D3, and D4 may have a Gaussian distribution 342. In other embodiments, the apodized etch depths D1, D2, D3, and D4 of the grating lines may be arranged in a different pattern. The third grating coupler (see Figure 2A 202) and the fourth grating coupler (see Figure 2A 204) may additionally have a tracked etch depth.

[0139] Also describe Figure 3G , 3H , 3I and 3J. In some embodiments, the second plurality of grating couplers are omitted (see Figure 2B 231), but retaining the first plurality of grating couplers 201 (e.g., the first grating coupler 104, the third grating coupler 202, and the fourth grating coupler 204). The resulting optical module is configured to receive the TE mode or TM mode of the electromagnetic input signal 302 (see 3A), wherein the TE mode or TM mode of the electromagnetic input signal 302 has an increased bandwidth and a greater alignment tolerance, while having a shorter vertical structure (e.g., the space occupied by the optical module in the device). Therefore, the optical module has an increased bandwidth and a greater alignment tolerance than the first grating coupler 104 alone, but has the same number of formation steps as a conventional grating coupler.

[0140] like Figure 3K and 3L As shown in top views 300k and 300l of FIG. 1 , in some embodiments, the fourth grating coupler (see FIG. Figure 2A 204) and the sixth grating coupler (see Figure 2B 208) is omitted. In addition, the first grating coupler 104 and the third grating coupler 202 face away from each other. That is, the grating lines 126 of the first grating coupler 104 and the third grating coupler 202 are directly located between the tapered section 125 of the first grating coupler 104 and the tapered section 125 of the third grating coupler 202. In another embodiment, the second grating coupler (see Figure 2B 105) and the fifth grating coupler (see Figure 2B The first waveguide 120 and the third waveguide 222 are bent to guide the input optical signal to the optical combiner 205. Figure 3K In , the grating lines 126 are substantially straight. Figure 3L, the first and second portions 336 and 338 of the grating line 126 are bent toward the tapered sections 125 of the first and third grating couplers 104 and 202, respectively. The third portion 340 of the grating line 126 is substantially straight and is located between the first and second portions 336 and 338.

[0141] Figure 4A and 4B Cross-sectional views 400a and 400b of an optical module with extended grating lines are shown.

[0142] like Figure 4A As shown, the polysilicon layer 406 may be included in the first plurality of grating couplers 201 (see Figure 2A ), the second plurality of grating couplers 231 (see Figure 2B ) or on top of both. The polysilicon layer 406 can extend the height of the grating line 126, thereby changing the coupling characteristics. Figure 4B As shown, in some embodiments, the polysilicon layer 406 has a height that varies with the grating lines 126. The polysilicon layer 406 may be formed as shown in FIG. Figures 3A-3C Combined with apodization as shown in 3E-3F, it can control the coupling efficiency of the optical module.

[0143] Figure 5 A top view 500 of an optical module overlaid with a light field emerging from a fiber optic cable is shown.

[0144] like Figure 5 As shown, the optical fiber cable 502 (shown in dotted lines) impinges on the optical module. The energy transmitted by the optical fiber cable 502 is output into two optical fields: a first mode optical field 504 and a second mode optical field 506. The first mode optical field 504 and the second mode optical field 506 correspond to the first mode portion 312 (see Figure 3A ) and the second mode portion 314 (see Figure 3A ) formed by the first mode light field 504 and the second mode light field 506. A change in the incident angle (e.g., the amount by which the optical fiber cable 502 is rotated) may cause a shift in the central wavelength of the electromagnetic input signal 302 coupled to the optical module. In some embodiments, a change in the incident angle may cause the central wavelength of the electromagnetic input signal to change by approximately 2 nanometers per degree. A change in the incident angle will also cause the first mode light field 504 and the second mode light field 506 to rotate.

[0145] Conventional grating couplers may have a bandwidth of approximately 20 to 40 nanometers. The described optical device has an increased 1 dB bandwidth, wherein in addition to the first plurality of grating couplers (see Figure 1A), the increased 1 dB bandwidth is generated by the combination of the bandwidths of the second grating coupler 105, the fifth grating coupler 206, and the sixth grating coupler 208. The increased 1 dB bandwidth can be two to four times the 1 dB bandwidth of a conventional grating coupler. The increased 1 dB bandwidth of the optical module results in a higher alignment tolerance because the coupling efficiency is maintained over a larger range of incident angles.

[0146] Figure 6A-6B , 7A-7B, 8A-8B, 9A-9B, 10A-10B, 11A-11B, 12A-12B, 13A-13B, 14A-14D, and 15A-15B illustrate cross-sectional views of some embodiments of methods of forming an optical module having a plurality of grating couplers and optical combiners. Figure 6A-6B , 7A-7B, 8A-8B, 9A-9B, 10A-10B, 11A-11B, 12A-12B, 13A-13B, 14A-14D and 15A-15B are described as a series of actions, but it should be understood that these actions are not restrictive, and the order of the actions can be changed in other embodiments, and the disclosed method is also applicable to other structures. In other embodiments, some actions shown and / or described can be omitted in whole or in part.

[0147] like Fig. 6A and 6B As shown in the cross-sectional view 600a and the top view 600b of FIG. 1 , a substrate 102 is provided. In some embodiments, the substrate 102 is or includes single crystal silicon, germanium, etc. Figure 6B Shown along Fig. 6A A top view 600b of some embodiments of an optical module taken along line AA′.

[0148] like Fig. 7A and 7B As shown in the cross-sectional view 700a and the top view 700b of FIG. 1 , the mirror 108 is deposited on the substrate 102. In some embodiments, the mirror 108 is deposited by performing a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, or some other suitable deposition or growth process. In some embodiments, the mirror 108 is or includes a metal, such as gold, aluminum, etc. The mirror 108 has a thickness, wherein the thickness is approximately between 200 and 400 nanometers, approximately between 150 and 300 nanometers, approximately between 250 and 500 nanometers, etc. Figure 7B Shown along Fig. 7A A top view 700b of some embodiments of an optical module taken along line AA′.

[0149] like Fig. 8A and 8BAs shown in the cross-sectional view 800a and the top view 800b of FIG. 1 , the first dielectric 106 is deposited on the mirror 108. In some embodiments, the first dielectric 106 is formed by performing a PVD process, a CVD process, an ALD process, or some other suitable deposition or growth process. In some embodiments, the first dielectric 106 includes silicon dioxide, a high-k dielectric, etc. Figure 8B Shown along Fig. 8A A top view 800b of some embodiments of an optical module taken along line AA′.

[0150] like Fig. 9A and 9B As shown in the cross-sectional view 900a and the top view 900b of FIG. 1 , the first grating coupler precursor 902 is deposited on the first dielectric 106. In some embodiments, the first grating coupler precursor 902 is formed by performing a PVD process, a CVD process, an ALD process, or some other suitable deposition or growth process. In some embodiments, the first grating coupler precursor 902 is or includes polysilicon, silicon nitride (Si3N4), etc. Fig. 9B Shown along Fig. 9A A top view 900b of some embodiments of an optical module taken along line AA′.

[0151] like Fig. 10A and 10B As shown in the cross-sectional view 1000a and the top view 1000b of FIG. 1000 , the first mask layer 1002 is formed on the first grating coupler precursor 902. In some embodiments, the first mask layer 1002 is or includes a photoresist patterned using photolithography. The first mask layer 1002 covers the first plurality of grating couplers 201 (see FIG. 1001 ). Figure 2A ) and optical combiner 205 (see Figure 2A ) of the first grating coupler precursor 902. Fig. 10B Shown along Fig. 10A A top view 1000b of some embodiments of an optical module taken along line AA′.

[0152] like Fig.11A and 11B As shown in the cross-sectional view 1100a and the top view 1100b of FIG. 100 , a first etch 1102 is performed on the first grating coupler precursor 902. In some embodiments, the first etch 1102 is a dry etch (e.g., a plasma enhanced dry etch). The first etch 1102 removes the portion of the first grating coupler precursor 902 exposed by the first mask layer 1002, thereby creating a first opening 1104 above the first dielectric 106. Fig. 11B Shown along Fig.11A A top view 1100b of some embodiments of an optical module taken along line AA′.

[0153] like Fig. 12A and 12B As shown in the cross-sectional view 1200a and the top view 1200b of , the first mask layer 1002 is removed. In addition, the second dielectric 111 fills the first opening 1104 around the first grating coupler precursor 902. In some embodiments, the first mask layer 1002 is removed using one or more stripping processes. In some embodiments, the second dielectric 111 is formed by performing a PVD process, a CVD process, an ALD process, or some other suitable deposition or growth process. A planarization process (e.g., a chemical mechanical planarization (CMP) process) is then performed to remove a portion of the second dielectric 111 above the top surface of the first grating coupler precursor 902. Fig. 12B Shown along Fig. 12A A top view 1200b of some embodiments of an optical module taken along line AA′.

[0154] like Fig.13A and 13B As shown in the cross-sectional view 1300a and the top view 1300b of FIG. 1 , the second mask layer 1302 is formed on the first grating coupler precursor 902 and the second dielectric 111. In some embodiments, the second mask layer 1302 is or includes a photoresist patterned using photolithography. The second mask layer 1302 covers the first plurality of grating couplers 201 (see FIG. 1 ). Figure 2A ) and optical combiner 205 (see Figure 2A ) in the first grating coupler precursor 902, leaving a portion of the first grating coupler precursor 902 to be formed subsequently in the first plurality of grating couplers 201 (see Figure 2A )'s exposed portion of the first grating coupler precursor 902 between the grating lines of ). Fig. 13B Shown along Fig.13A A top view 1300b of some embodiments of an optical module taken along line AA′.

[0155] like Fig.14A and 14B As shown in the top view 1400a and the cross-sectional views 1400b, 1400c and 1400d of FIG. 1400, a second etch 1402 is performed on the first grating coupler precursor 902. The second etch 1402 is a dry etch (e.g., a plasma enhanced dry etch). The second etch 1402 removes the remaining portion of the first grating coupler precursor 902 exposed by the second mask layer 1302, exposing the first plurality of grating couplers 201 (see FIG. 1401). Figure 2A )'s sidewalls. Fig. 14B Shown along Fig.14A A top view 1400b of some embodiments of an optical module taken along line AA′. Fig. 14C Shown along Fig.14AA cross-sectional view 1400c of some embodiments of an optical module taken along line BB′. Fig.14D Shown along Fig.14D A cross-sectional view 1400d of some embodiments of an optical module taken along line CC'.

[0156] like Figures 14B-14D As shown, the first grating coupler 104, the third grating coupler 202, and the fourth grating coupler 204 include grating lines 126 having a first grating period 116a, a third grating period 116c, and a fourth grating period 116d (e.g., the distance between the start of the first grating line and the start of the subsequent grating line), a first spacing 112a, a third spacing 112c, and a fourth spacing 112d (e.g., the distance between the end of the first grating line and the start of the subsequent grating line), and a first duty cycle 114a, a third duty cycle 114c, and a fourth duty cycle 114d (e.g., the proportion of the grating period occupied by the first grating line). The first grating period 116a of the first grating coupler 104 is different from the third grating period 116c of the third grating coupler 202 and the fourth grating period 116d of the fourth grating coupler 204. In addition, the first duty cycle 114a, the third duty cycle 114c, and the fourth duty cycle 114d are different from each other, and the first spacing 112a, the third spacing 112c, and the fourth spacing 112d are different from each other. The difference in the first grating period 116a, the third grating period 116c, and the fourth grating period 116d is a factor in the first grating coupler 104, the third grating coupler 202, and the fourth grating coupler 204 having bandwidths centered at different wavelengths. In some embodiments, the bandwidths of the third grating coupler 202 and the fourth grating coupler 204 overlap with the first outer bandwidth limit and the second outer bandwidth limit of the bandwidth of the first grating coupler, respectively. That is, the bandwidth of the third grating coupler 202 overlaps with the first outer bandwidth limit of the first grating coupler 104, and the fourth grating coupler 204 overlaps with the second outer bandwidth limit of the first grating coupler 104. The bandwidth variation of the multiple grating couplers combined with their proximity enables the optical module to be configured to receive electromagnetic input signals having higher bandwidth than conventional grating couplers while maintaining higher alignment tolerances.

[0157] like Fig.15A and 15B As shown in the cross-sectional view 1500a and the top view 1500b of FIG. 1500, the second mask layer 1302 is removed. In addition, the third dielectric 110 covers the first plurality of grating couplers 201. In some embodiments, the second mask layer 1302 is removed using one or more lift-off processes. In some embodiments, the third dielectric 110 is formed by performing a PVD process, a CVD process, an atomic layer deposition ALD process, or some other suitable deposition or growth process.

[0158] Fig. 15B Shown along Fig.15A A top view 1500b of some embodiments of an optical module taken along line AA'. Fig. 15B As shown, Fig.11A , 12A , 13A, 14A and 15A, so as to form a first plurality of grating couplers 201 including a first grating coupler 104, a third grating coupler 202 and a fourth grating coupler 204. The first grating coupler 104, the third grating coupler 202 and the fourth grating coupler 204 are coupled to an optical combiner 205 by a first waveguide 120, a third waveguide 222 and a fourth waveguide 224, respectively. The first grating coupler 104, the third grating coupler 202 and the fourth grating coupler 204 include grating lines 126, wherein the grating lines 126 are bent to guide the input optical signal to the first waveguide 120, the third waveguide 222 and the fourth waveguide 224, respectively. The first waveguide 120 branches from the optical combiner 205 in a first direction toward the first grating coupler 104, and optically couples the first grating coupler 104 to the optical combiner 205. The third waveguide 222 branches from the optical combiner 205 in the second direction toward the third grating coupler 202, and optically couples the third grating coupler 202 to the optical combiner 205. The fourth waveguide 224 branches from the optical combiner 205 in the third direction toward the fourth grating coupler 204, and optically couples the fourth grating coupler 204 to the optical combiner 205. In various embodiments, the first direction, the second direction, and the third direction are different from each other.

[0159] Figures 16A-16B , 17A-17B, 18A-18B and 19A-19B show a method for forming a second plurality of grating couplers 231 (see Figure 2B ) Figure 6A-6B , 7A-7B, 8A-8B, 9A-9A, 10A-10B, 11A-11B, 12A-12B, 13A-13B, 14A-14D and 15A-15B are cross-sectional views of some embodiments of the continuation of the method described. Figure 6A-6B , 7A-7B, 8A-8B, 9A-9B, 10A-10B, 11A-11B, 12A-12B, 13A-13B, 14A-14B and 15A-15B are described as a series of actions, but it should be understood that these actions are not restrictive, and the order of the actions can be changed in other embodiments, and the disclosed method is also applicable to other structures. In other embodiments, some actions shown and / or described can be omitted in whole or in part.

[0160] like Fig.16A and 16BAs shown in the cross-sectional view 1600a and the top view 1600b of FIG. 1600 , the second grating coupler precursor 1602 is deposited on the third dielectric 110. In some embodiments, the second grating coupler precursor 1602 is formed by performing a PVD process, a CVD process, an ALD process, or some other suitable deposition or growth process. In some embodiments, the second grating coupler precursor 1602 is or includes polysilicon, silicon nitride, etc. Fig. 16B Shown along Fig.16A A top view 1600b of some embodiments of an optical module taken along line AA′.

[0161] like Fig.17A and 17B As shown in the cross-sectional view 1700a and the top view 1700b of FIG. 1700, the third mask layer 1702 is formed on the second grating coupler precursor 1602. In some embodiments, the third mask layer 1702 is or includes a photoresist patterned using photolithography. The third mask layer 1702 covers the layers corresponding to the second plurality of grating couplers 231 (see FIG. 1701). Figure 2B ) and optical combiner 210 (see Figure 2B ) in the grating lines of the second grating coupler precursor 1602. The third mask layer 1702 is left outside the second plurality of grating couplers 231 and between the grating lines of the second plurality of grating couplers 231 (see Figure 2B )'s exposed portion of the second grating coupler precursor 1602. Fig. 17B Shown along Fig.17A A top view 1700b of some embodiments of an optical module taken along line AA'.

[0162] like Fig.18A and 18B As shown in the cross-sectional view 1800a and the top view 1800b, in the second grating coupler precursor 1602 (see Fig.16A ) is performed on the substrate. The third etch 1802 removes the remaining portion of the second grating coupler precursor 1602 exposed by the third mask layer 1702, so that a second plurality of grating couplers (see Figure 2B 231). A second plurality of grating couplers (see Figure 2B 231) has such Figure 2A , 2B , 2C and 2D describe the second grating line 126b. Fig.18B Shown along Fig.18A A top view 1800b of some embodiments of an optical module taken along line AA'.

[0163] like Fig.19A and 19BAs shown in the cross-sectional view 1900a and the top view 1900b of FIG. 1900 , the third mask layer 1702 is removed. In addition, the fourth dielectric 112 is formed on and around the second plurality of grating couplers 231. In some embodiments, the third mask layer 1702 is removed using one or more lift-off processes. In some embodiments, the fourth dielectric 112 is formed by performing a PVD process, a CVD process, an ALD process, or some other suitable deposition or growth process. Fig.19B Shown along Fig.19A A top view 1900b of some embodiments of an optical module taken along line AA'.

[0164] Fig. 20 A method 2000 of forming an optical module having a plurality of grating couplers and an optical combiner is shown. Although the method and other methods shown and / or described herein are shown as a series of actions or events, it should be understood that the present disclosure is not limited to the order or actions shown. Therefore, in some embodiments, the actions may be performed in an order different from the order shown, and / or may be performed simultaneously. In addition, in some embodiments, the actions or events shown may be subdivided into multiple actions or events, which may be performed at a separate time or simultaneously with other actions or sub-actions. In some embodiments, some of the actions or events shown may be omitted, and other actions or events not shown may be included.

[0165] At step 2002, a mirror is formed on a substrate. For example, see Figure 7A-7B .

[0166] At step 2004, a first dielectric is formed over the mirror. For example, see Figures 8A-8B .

[0167] At step 2006, a first grating coupler precursor is formed on a first dielectric. Figures 9A-9B .

[0168] At step 2008, a first grating coupler precursor is etched to form a first grating coupler having a first plurality of grating lines, wherein the first plurality of grating lines are laterally separated by a first pitch. Figures 14A-14B .

[0169] At step 2010, a lens is formed on a first plurality of grating lines of a first grating coupler. Figure 3D .

[0170] At step 2012, a second grating coupler precursor is formed on the lens. Figure 3D The lens and Fig.16A and 16BA second grating coupler precursor is shown.

[0171] At step 2014, a second grating coupler precursor is etched to form a second grating coupler having a second plurality of grating lines, wherein the second plurality of grating lines are laterally separated by a second pitch. Figures 18A-18B .

[0172] Thus, the present disclosure is directed to a method of forming an optical module including a plurality of grating couplers and an optical combiner.

[0173] Some embodiments relate to an optical module, comprising a substrate; a first grating coupler overlying the substrate; and a second grating coupler overlying the first grating coupler, wherein the second grating coupler is configured to receive a first transverse mode of an input optical signal and pass a second transverse mode of the input optical signal to the first grating coupler, and wherein the first grating coupler is configured to receive the second transverse mode of the input optical signal.

[0174] In some other embodiments, in the optical module, the first grating coupler has a first bandwidth; and the second grating coupler has a second bandwidth substantially equal to the first bandwidth.

[0175] In some other embodiments, the optical module further includes: a third grating coupler flush with and close to the first grating coupler and having a third bandwidth, wherein the third bandwidth partially overlaps with the first outer wavelength limit of the first bandwidth.

[0176] In some other embodiments, the optical module further includes: an optical combiner coupled to the first grating coupler and the third grating coupler; a first waveguide branched from the optical combiner in a first direction toward the first grating coupler, wherein the first grating coupler is optically coupled to the optical combiner through the first waveguide; and a second waveguide branched from the optical combiner in a second direction toward the third grating coupler, wherein the second direction is different from the first direction, and wherein the third grating coupler is optically coupled to the optical combiner through the second waveguide.

[0177] In some other embodiments, in the optical module, the first transverse mode is a transverse electric mode, and the second transverse mode is a transverse magnetic mode.

[0178] In some other embodiments, in the optical module, the first grating coupler includes first grating lines having a first pitch, and the second grating coupler includes second grating lines having a second pitch different from the first pitch.

[0179] In some other embodiments, the optical module further includes: a lens located between the first grating coupler and the second grating coupler.

[0180] In some other embodiments, the optical module further includes: a mirror located below the first grating coupler and configured to reflect the input optical signal back to the first grating coupler and the second grating coupler.

[0181] In some other embodiments, in the optical module, the first grating coupler has a first duty cycle that varies from a first end to a second end of the first grating coupler.

[0182] Other embodiments relate to an optical module comprising a substrate; a first grating coupler overlying the substrate, wherein the first grating coupler comprises a plurality of first grating lines laterally adjacent to a first tapered segment, wherein the plurality of first grating lines have a first grating period; and a second grating coupler overlying the substrate and adjacent to the first grating coupler, wherein the second grating coupler comprises a plurality of second grating lines laterally adjacent to a second tapered segment, wherein the plurality of second grating lines have a second grating period different from the first grating period.

[0183] In some other embodiments, in the optical module, the first grating coupler is vertically spaced between the second grating coupler and the substrate, wherein at least a portion of the second plurality of grating lines directly overlies at least a portion of the first plurality of grating lines.

[0184] In some other embodiments, the optical module further includes: an optical combiner overlying the substrate; a first waveguide branching from the optical combiner in a first direction toward the first grating coupler, wherein the first grating coupler is optically coupled to the optical combiner through the first waveguide; and a second waveguide branching from the optical combiner in a second direction toward the second grating coupler, wherein the second direction is different from the first direction, and wherein the second grating coupler is optically coupled to the optical combiner through the second waveguide.

[0185] In some other embodiments, in the optical module, the plurality of first grating lines have side walls with different heights.

[0186] In some other embodiments, in the optical module, the heights of the sidewalls of the plurality of first grating lines vary according to a Gaussian distribution.

[0187] Still other embodiments relate to a method of forming an optical module, comprising forming a first grating coupler precursor on a substrate; etching the first grating coupler precursor to form a first grating coupler having a first plurality of grating lines, the first plurality of grating lines being laterally separated by a first spacing; forming a first dielectric on the first grating coupler; forming a second grating coupler precursor overlying the first grating coupler and on the first dielectric; and etching the second grating coupler precursor to form a second grating coupler having a second plurality of grating lines, the second plurality of grating lines being laterally separated by a second spacing, wherein the second grating coupler is directly located on the first grating coupler.

[0188] In some other embodiments, in the method, etching the first grating coupler precursor includes: performing a first etching process to form a first optical combiner, a first waveguide coupled to the first optical combiner, and a second waveguide coupled to the first optical combiner; and performing a second etching process to form the first plurality of grating lines of the first grating coupler, wherein the first grating coupler is coupled to the first waveguide, and further forming a third plurality of grating lines of a third grating coupler close to the first grating coupler, wherein the third plurality of grating lines are laterally separated from each other by a third spacing, wherein the third spacing is different from the first spacing and the second spacing, and wherein the third grating coupler is coupled to the second waveguide.

[0189] In some other embodiments, the method further includes: forming a mirror on the substrate before forming the first grating coupler precursor; and forming a second dielectric before forming the first grating coupler precursor, wherein the second dielectric separates the mirror from the first grating coupler precursor.

[0190] In some other embodiments, the method further includes: forming a second dielectric before forming the second grating coupler precursor; forming a lens before forming the second grating coupler precursor, wherein the lens is configured to redirect the input optical signal to the first grating coupler and the second dielectric separates the lens from the first grating coupler; and forming a third dielectric before forming the second grating coupler precursor, wherein the third dielectric covers the lens.

[0191] In some other embodiments, in the method, forming the first plurality of grating lines includes a first etch, the first etch etching to a first depth within the first grating coupler precursor so that a grating substrate is below the first plurality of grating lines; and wherein forming the second plurality of grating lines includes a second etch, the second etch etching through a bottom surface of the second grating coupler precursor.

[0192] In some other embodiments, in the method, the second spacing of the second grating coupler is configured to receive the first transverse mode of the input optical signal and pass the second transverse mode of the input optical signal to the first grating coupler, wherein the first spacing of the first grating coupler is configured to receive the second transverse mode of the input optical signal.

[0193] It should be understood that in this specification and the following invention claims, the terms "first", "second", "third", etc. are only general identification symbols used for ease of description to distinguish components of different figures or a series of figures. By themselves, these terms do not imply any temporal order or structure close to these components, and are not intended to describe corresponding components in different illustrated embodiments and / or unillustrated embodiments. For example, the "first dielectric layer" described in conjunction with the first figure may not necessarily correspond to the "first dielectric layer" described in conjunction with another figure, and may not necessarily correspond to the "first dielectric layer" in an unillustrated embodiment.

[0194] The foregoing summarizes the features of several embodiments so that those skilled in the art can better understand the various aspects of the present disclosure. Those skilled in the art will appreciate that they can readily use the present disclosure as a basis for designing or modifying other processes and structures for performing the same purposes and / or achieving the same advantages of the embodiments introduced herein. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and those skilled in the art may make various changes, substitutions, and modifications to the present disclosure without departing from the spirit and scope of the present disclosure.

Claims

1. An optical module, characterized in that: include: substrate; A first grating coupler overlying the substrate; as well as A second grating coupler overlying the first grating coupler, wherein the second grating coupler is configured to receive a first transverse mode of an input optical signal and transmit a second transverse mode of the input optical signal to the first grating coupler, and wherein the first grating coupler is configured to receive the second transverse mode of the input optical signal.

2. The optical module according to claim 1, characterized in that: The first grating coupler has a first bandwidth; and The second grating coupler has a second bandwidth substantially equal to the first bandwidth.

3. The optical module according to claim 1, characterized in that: The first transverse mode is a transverse electric mode, and the second transverse mode is a transverse magnetic mode.

4. The optical module according to claim 1, characterized in that: The first grating coupler includes first grating lines having a first pitch, and the second grating coupler includes second grating lines having a second pitch different from the first pitch.

5. The optical module according to claim 1, characterized in that: Also includes: A lens is located between the first grating coupler and the second grating coupler.

6. The optical module according to claim 1, characterized in that: Also includes: A mirror is located below the first grating coupler and is configured to reflect the input optical signal back to the first grating coupler and the second grating coupler.

7. An optical module, characterized in that: include: substrate; a first grating coupler overlying the substrate, wherein the first grating coupler comprises a plurality of first grating lines laterally adjacent to the first tapered segment, wherein the plurality of first grating lines have a first grating period; and a second grating coupler overlying the substrate and adjacent to the first grating coupler, wherein the second grating coupler includes a plurality of second grating lines laterally adjacent to the second tapered segment, wherein the plurality of second grating lines have a second grating period different from the first grating period, and wherein a distance between the first grating coupler and the second grating coupler is less than a length of the first grating coupler.

8. The optical module according to claim 7, characterized in that: The first grating coupler is vertically spaced between the second grating coupler and the substrate, wherein at least a portion of the second plurality of grating lines directly overlies at least a portion of the first plurality of grating lines.

9. The optical module according to claim 7, characterized in that: Also includes: an optical combiner overlying the substrate; a first waveguide branching from the optical combiner in a first direction toward the first grating coupler, wherein the first grating coupler is optically coupled to the optical combiner through the first waveguide; as well as A second waveguide branches from the optical combiner in a second direction toward the second grating coupler, wherein the second direction is different from the first direction, and wherein the second grating coupler is optically coupled to the optical combiner through the second waveguide.

10. The optical module according to claim 7, characterized in that: The plurality of first grating lines have side walls with different heights.

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