Apparatus and article of manufacture including multiple core structures and method of manufacturing a polarization splitter rotator - Patents.com

Abstract

The polarization rotator structure (PRS) includes a first core structure formed in a first layer and extending from a first end to a second end, and a second structure formed in a second layer at a different depth from the first layer and adjacent to the first core structure. The first and second core structures provide mode hybridization of at least two orthogonally polarized waveguide modes of the PRS. The optical splitter structure includes a first core structure optically coupled at its first end to the second end of the PRS and optically coupled at its second end to at least two optical waveguides, the first core structure being contiguous with at least one of the first or second core structure of the PRS, and a second core structure separated from both the first and second core structures of the PRS.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 018,635, filed May 1, 2020, and entitled “METHOD AND ARCHITECTURE FOR GENERATING ON-CHIP POLARIZATION SPLITTER ROTATORS.”

[0002] The present disclosure relates to the integration of polarization rotation and splitting using mode hybridization between multiple-core structures. [Background technology]

[0003] Some techniques for integrating polarization splitter rotator (PSR) structures into photonic integrated circuits (PICs) or other photonic devices use ridge etch structures to break the symmetry in the PSR structure. However, such techniques only work well with materials that have a relatively high refractive index, such as silicon. Materials with a relatively low refractive index tend to exhibit secondary transverse electric (TE) modes (e.g., TE 21 To support the second-order TE mode and the fundamental transverse magnetic (TM) mode (e.g., TM mode) when the modal powers are concentrated at different locations, 11 In some cases, the perturbation introduced by the ridge etch may be too small to disrupt the large birefringence of the TE and TM polarizations. As a result, a relatively long (e.g., mm-scale) transition may be required to convert the polarization, and / or the conversion efficiency may be relatively low to be impractical for commercial use. Summary of the Invention

[0004] In one aspect, in general, an apparatus includes a photonic integrated circuit (PIC) including a plurality of optical waveguides, and a polarization rotator structure integrated into the PIC and optically coupled at a first end to at least one of the plurality of optical waveguides. The polarization rotator structure includes a first core structure formed in a first layer and a second core structure formed in a second layer at a depth different from the first layer, the first core structure extending from a first end to a second end of the polarization rotator structure, and the second layer formed adjacent to the first core structure. The first and second core structures provide mode hybridization of at least two orthogonal polarization waveguide modes of the polarization rotator structure. The first and second layers are separated by a third layer including a material different from a core material of the first core structure and a core material of the second core structure, and / or the core material of the first core structure is different from a core material of the second core structure. The apparatus also includes an optical splitter structure integrated into the PIC and optically coupled to a first end of the polarization rotator structure and optically coupled at a second end to at least two of the optical waveguides, the optical splitter structure including a first core structure contiguous with at least one of the first core structure or the second core structure of the polarization rotator structure, and a second core structure separated from both the first core structure or the second core structure of the polarization rotator structure.

[0005] Aspects can include one or more of the following features.

[0006] The first and second core structures of the polarization rotator structure are TM of the first core structure. 11 Modes and TE of the first core structure 21 This gives a mode hybridization with the mode.

[0007] The second core structure of the polarization rotator structure includes at least two separate continuous portions of core material that extend across at least a portion of the distance between the first end of the polarization rotator structure and the second end of the polarization rotator structure.

[0008] In another aspect, in general, an article of manufacture includes at least one cladding material providing cladding for a plurality of optical waveguides, a core material providing cores for the optical waveguides, the core material including at least one material having a higher refractive index than the cladding material, a first mode coupling structure, and a second mode coupling structure, the first mode coupling structure having a first end optically coupled to at least one optical waveguide formed in the cladding material, the first mode coupling structure including a first core structure formed in a first layer and a second core structure formed in a second layer at a depth different from the first layer and adjacent the first core structure, the first core structure extending from the first end to the second end of the first mode coupling structure. the second core structure comprises at least two separate continuous portions of the core material extending over at least a portion of the distance between a first end of the first mode coupling structure and a second end of the first mode coupling structure, the second mode coupling structure having a first end optically coupled to the second end of the first mode coupling structure and a second end optically coupled to at least two optical waveguides formed in the cladding material, the second mode coupling structure comprising a third core structure comprising a portion of core material contiguous with the core material of at least one of the first core structure or the second core structure, and a fourth core structure comprising a portion of core material separate from the core material of both the first core structure and the second core structure.

[0009] Aspects can include one or more of the following features.

[0010] The first core structure and the second core structure provide mode hybridization between a fundamental mode of the first core structure having a first polarization and a non-fundamental mode of the first core structure having a second polarization that is orthogonal to the first polarization.

[0011] A portion of the core material of the third core structure is contiguous with a continuous portion of the core material of the first core structure.

[0012] The second mode coupling structure includes a portion of the third core structure and the fourth core structure that are close to each other over a distance that provides evanescent coupling between a non-fundamental mode received at the third core structure and a fundamental mode of the fourth core structure, and preserves the fundamental mode of the third core structure without evanescent coupling with the fourth core structure.

[0013] The continuous portion of core material of the first core structure has an increasing width over at least a portion of the distance between the first end of the first modal coupling structure and the second end of the first modal coupling structure.

[0014] The two spaced apart contiguous portions of the core material of the second core structure have substantially equal widths that increase over a first distance and decrease over a second distance.

[0015] The fundamental mode of the first core structure is TM 11 modes, and the non-fundamental modes of the first core structure are TE 21 Includes modes.

[0016] Mode hybridization is based on the effective refractive index of the fundamental mode of the first core structure being substantially equal in magnitude to the effective refractive index of a non-fundamental mode of the first core structure.

[0017] The first core structure and the second core structure provide mode hybridization between a fundamental mode of the first core structure having a first polarization and a non-fundamental mode of the second core structure having a second polarization that is orthogonal to the first polarization.

[0018] A portion of the core material of the third core structure is contiguous with a continuous portion of the core material of the first core structure and is contiguous with one of the two continuous portions of the core material of the second core structure.

[0019] The second mode coupling structure includes a portion of the third core structure and the fourth core structure that are close to each other over a distance that provides evanescent coupling between a non-fundamental mode received at the third core structure and a fundamental mode of the fourth core structure, and preserves the fundamental mode of the third core structure without evanescent coupling with the fourth core structure.

[0020] The continuous portion of core material of the first core structure has a substantially constant width between the first end of the first modal coupling structure and the second end of the first modal coupling structure.

[0021] One of the two separate continuous portions of core material of the second core structure vertically overlaps the continuous portion of core material of the first core structure, and one of the two separate continuous portions of core material of the second core structure does not vertically overlap the continuous portion of core material of the first core structure.

[0022] The fundamental mode of the first core structure is TM 11 modes, and the non-fundamental modes of the second core structure are TE 21 Includes modes.

[0023] In another aspect, a method of making a polarization splitter rotator generally includes providing at least one cladding material providing a cladding for a plurality of optical waveguides; forming waveguides in the cladding material using a core material including at least one material having a refractive index higher than a refractive index of the cladding material; and forming a first mode-coupling structure optically coupled to a first end of at least one optical waveguide formed in the cladding material, the first mode-coupling structure including a first core structure formed in a first layer and a second core structure formed in a second layer at a depth different from the first layer and adjacent the first core structure, the first core structure extending from the first end of the first mode-coupling structure to the second core structure. the second core structure includes at least one continuous portion of the core material extending to an end of the first mode coupling structure, the second core structure including at least two separate continuous portions of the core material extending across at least a portion of the distance between the first end of the first mode coupling structure and the second end of the first mode coupling structure, forming a second mode coupling structure having a first end optically coupled to the second end of the first mode coupling structure and a second end optically coupled to at least two optical waveguides formed in the cladding material, the second mode coupling structure including a third core structure including a portion of the core material that is continuous with the core material of at least one of the first core structure or the second core structure, and a fourth core structure including a portion of the core material that is separate from the core material of both the first core structure and the second core structure.

[0024] Aspects can include one or more of the following features.

[0025] The first core structure and the second core structure provide mode hybridization between a fundamental mode of the first core structure having a first polarization and a non-fundamental mode of the first core structure having a second polarization that is orthogonal to the first polarization.

[0026] The first core structure and the second core structure provide mode hybridization between a fundamental mode of the first core structure having a first polarization and a non-fundamental mode of the second core structure having a second polarization that is orthogonal to the first polarization.

[0027] Aspects may have one or more of the following advantages.

[0028] The techniques described herein can be used to form compact and efficient integrated PSR structures using either a relatively high index of refraction (e.g., silicon with an index of refraction of about 3.5) or a relatively low index of refraction (e.g., silicon nitride with an index of refraction of about 2.0) at the operating wavelength of the device. In some implementations, the PSR structure is formed using two layers of core material to provide hybridization of the fundamental TM mode with the non-fundamental TE modes. For example, the transition portion of the structure may include three waveguide cores, one core in one layer and the other two cores in the other layer. The waveguide cores may be arranged in a "chevron array" (e.g., a V-chevron style or an inverted V-chevron style), which allows the fundamental TM mode (e.g., TM TE mode) to be hybridized with the non-fundamental TE mode, as described in more detail below. 11 ) and non-fundamental TE modes (e.g. TE 21 The top-bottom symmetry of the coupling geometry can be broken to allow hybridization with the modes in the coupling waveguide, even when the effective refractive indices of the modes are relatively close. The modes are sufficiently isolated from each other with minimal mutual coupling because the other modes supported by the coupling waveguide have effective indices that are sufficiently separated. In some implementations, more than two layers can be used, as will also be described in more detail below.

[0029] Other features and advantages will become apparent from the following description, and from the drawings and claims. [Brief description of the drawings]

[0030] The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings, in which: It is emphasized that, according to common practice, the various features of the drawings are not to scale, and on the contrary, dimensions of the various features have been arbitrarily expanded or reduced for clarity.

[0031] [Figure 1A]1A-1C are cross-sectional views of examples of different angle-style or inverted angle-style waveguides. [Figure 1B] 1A-1C are cross-sectional views of examples of different angle-style or inverted angle-style waveguides. [Figure 1C] 1A-1C are cross-sectional views of examples of different angle-style or inverted angle-style waveguides. [Figure 1D] 1A-1C are cross-sectional views of examples of different angle-style or inverted angle-style waveguides. [Figure 1E] 1A-1C are cross-sectional views of examples of different angle-style or inverted angle-style waveguides. [Figure 1F] 1A-1C are cross-sectional views of examples of different angle-style or inverted angle-style waveguides. [Figure 2A] FIG. 13 illustrates a set of waveguide cross-sections for different positions along a multi-core mode coupled waveguide structure. [Figure 2B] 1 is a plot of effective refractive index versus position for an eigenmode of a multicore waveguide structure. [Figure 2C] 1 is a set of cross sections of electric field intensity profiles for different positions along a multi-core waveguide structure. [Figure 2D] 1 is a set of cross sections of electric field intensity profiles for different positions along a multi-core waveguide structure. [Figure 2E] 1 is a set of cross sections of electric field intensity profiles for different positions along a multi-core waveguide structure. [Figure 3A] 1A-1C are a top view and alternative cross-sectional views of an exemplary PSR device. [Figure 3B] FIG. 13 is a top view of the rotor of the PSR with cross sections of the mode profiles at different locations for different eigenmodes. [Figure 3C] FIG. 13 is a top view of the splitter of the PSR with cross sections of the mode profiles at different locations for different eigenmodes. [Figure 3D] 1 is a graph of the effective refractive index associated with a simulated waveguide structure. [Figure 4A] 1A and 1B are top and cross-sectional views of an exemplary PSR device. [Figure 4B] FIG. 13 is a top view with cross sections of mode profiles at different locations for different eigenmodes of the first modal coupling structure. [Figure 4C] 4C is a graph of the effective refractive index for the construction of FIG. 4B. [Figure 4D] FIG. 13 is a top view with cross sections of mode profiles at different locations for different eigenmodes of the second modal coupling structure. [Figure 4E] 4E is a graph of the effective refractive index for the structure of FIG. 4D. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The techniques described herein can be used to fabricate polarization splitter rotators (PSRs). For example, PSRs can be used in polarization diversity modules or other photonic modules depending on the polarization rotation and splitting / combining functions provided. This is described in detail below. In some implementations, the polarization splitter rotators are fabricated on-chip, such as on a photonic integrated circuit (PIC), which may be fabricated on a semiconductor substrate (e.g., a silicon-on-insulator (SOI) platform or other platform that may be fabricated using layers of materials deposited and etched on a substrate). In some implementations, CMOS fabrication processes may be used. In addition, the techniques described herein allow such fabrication processes to result in compact PSR structures without necessarily requiring the use of high refractive index materials. Because low refractive index materials tend to exhibit low propagation losses, the techniques described herein enable the implementation of high performance devices and reduce costs associated with the use of high refractive index materials for polarization manipulation.

[0033] In some implementations, a technique that can be used to facilitate a compact design of the PSR using materials with a relatively low refractive index includes the use of a chevron-style waveguide. In some implementations, a first mode-coupling structure provides a mode-dependent polarization rotator for the light received into an input port to convert orthogonal polarization modes (e.g., one TE mode and one TM mode) into co-polarized (both TE modes), and a second mode-coupling structure splits the co-polarized modes into different output ports. Similarly, a PSR can be used in the reverse direction to couple physically separated co-polarized modes into a combined polarization mode and an orthogonal polarization mode at one output port. A chevron-style waveguide includes multiple waveguide cores arranged in a chevron arrangement that can break the vertical symmetry of the waveguide modes. This breaking of vertical symmetry made possible by the chevron-style waveguide facilitates mode hybridization in the first mode-coupling structure, which allows the fundamental TM polarization mode (e.g., TM 11 ) and higher-order TE polarization modes (e.g. TE 21 ) to obtain mode-dependent polarization rotation. Other mode-coupling structures allow the conversion between the generated higher-order TE polarization modes received into the first core structure and the fundamental TE polarization mode (e.g., TE 11 ) to obtain the splitting of co-polarized modes into different core structures. Mode hybridization is based on the change in the magnitude of the effective refractive index associated with the propagating optical mode of light guided by the varying coupled multi-core waveguide structures. This is described in more detail below (with reference to FIG. 2B).

[0034] An example of such a chevron array of multi-core waveguides containing different core structures in different layers of the PIC is shown with reference to Figures 1A-1F. With reference to Figure 1A, a mode-coupling structure 100A includes a top core 102A in a top layer 103A and two bottom cores 104A and 106A in a bottom layer 105A. In this example, there is a gap layer 107A between the top layer 103A and the bottom layer 105A. A cross section of the core structure is shown in the yz plane (relative to the y and z axes 101). The yz plane is orthogonal to the x-axis of the light guided by the multi-core waveguide. The goal of this array is to separate two optical modes (i.e., TM in this example) by breaking the vertical symmetry about the z-axis. 11 and T.E. 21 If a single-core waveguide were present that contained only the top core 102A, the second-order TE-polarized mode TE 21 The fundamental TM polarization mode TM is not coupled to 11 By incorporating two cores 104A and 106A in the bottom layer 105A adjacent to the core 102A in the top layer 103A, the top-bottom symmetry is broken and two modes TM are present, as will be described in more detail below. 11 and T.E. 21 For example, the multi-core waveguide formed by the mode-coupling structure 100A supports hybridized mode profiles based on certain structural features including a relatively thin gap layer 107A and the overlap of the top core 102A with the bottom cores 104A and 106A, respectively, in the dimension along the y-axis, as shown in FIG.

[0035] Various alternative chevron arrangements of multi-core waveguides can be formed. In some implementations, the cores form an inverted chevron structure as in FIG. 1B. FIG. 1B shows a mode-coupled structure 100B that includes a bottom core 102B in a bottom layer 105B and two top cores 104B and 106B in a top layer 103B. In this example, there is a gap layer 107B between the top layer 103B and the bottom layer 105B.

[0036] In some implementations, multiple layers can be formed by patterning one thick layer of high index core material into a low index cladding material that provides the surrounding cladding. Figure 1C shows a chevron style mode-coupling structure 100C that includes a top core 102C in a top layer 103C and two bottom cores 104C and 106C in a bottom layer 105C. Figure 1D shows an inverted chevron style mode-coupling structure 100D that includes a bottom core 102D in a bottom layer 105D and two top cores 104D and 106D in a top layer 103D. In these examples of Figures 1C and 1D, there is no gap layer between the corresponding top and bottom layers.

[0037] In some implementations, more than two layers may form an extended chevron array of multi-core waveguides. FIG. 1E shows a chevron-style mode-coupling structure 100E including a top core 102E in a top layer 103E, two intermediate cores 104E and 106E in a middle layer 105E, and two bottom cores 108E and 110E in a bottom layer 107E. This example also includes gap layers 109E and 111E as shown. FIG. 1F shows an inverted chevron-style mode-coupling structure 100F including a bottom core 102F in a bottom layer 107F, two intermediate cores 104F and 106F in a middle layer 105F, and two top cores 108F and 110F in a top layer 103F. This example also includes gap layers 109F and 111F as shown.

[0038] Another aspect of the multi-core mode coupling structure that allows for mode hybridization is that the widths of the different core structures change as the guided light waves propagate along the propagation axis (i.e., the x-axis in these examples). For example, the width of the bottom core can be increased adiabatically as the guided light propagates. FIG. 2A shows an example of different cross sections of a multi-core mode coupling structure where the width of the bottom core increases for three different positions along the x-axis. Cross section 200A at X=-4 (arbitrary distance units) shows that the bottom core narrows and extends to the edge of the top core. Cross section 200B at X=0 further shows that the bottom core widens and extends past the edge of the top core. Cross section 200C at X=4 further shows that the bottom core extends even further past the edge of the top core. This increase in bottom core width allows for a mode transition process based on mode hybridization.

[0039] FIG. 2B shows a plot of the effective refractive index of the first three eigenmodes (labeled as mode 1, mode 2, and mode 3) as a function of position X (arbitrary distance units) along the x-axis as the width of the bottom core increases adiabatically as the propagation position progresses from X=-5 to X=5. The fundamental first eigenmode (mode 1) is at TE 11 The second eigenmode (mode 2) is the TM mode, which has a maximum effective refractive index that is well separated in magnitude (approximately 1.58 to 1.60) from the effective refractive index of the other modes. 11 The third eigenmode (mode 3) begins as a TE mode with an effective refractive index of approximately 1.48. 21 In some cases, the third order modes are relatively weakly supported, so that the initial light energy ends up with no energy in the highest TE mode (mode 1) and the highest TM mode (mode 2), mode 3, or lower eigenmodes. As light propagates through the structure of FIG. 2A, there exists a mode hybridization region 202 where the effective refractive indices of modes 2 and 3 approach each other, and a mode transition process causes mode 2 to hybridize to the TE mode (mode 1). 21 mode, and mode 3 is TM 11Mode 1 TE 11 The mode is preserved.

[0040] Figures 2C-2E show example electric field intensity profiles resulting from the mode-coupled structure of Figure 2A as light propagates through the mode transition process. Figure 2C shows how mode 1 retains its relative intensity profile and polarization at each of the three cross-sectional locations shown in Figure 2A. Figures 2D and 2E show how the intensity profiles and polarization modes for modes 2 and 3 change, resulting in gradual polarization rotation via mode hybridization.

[0041] 3A shows an exemplary PSR device 300 that includes a polarization rotator mode-coupling structure 301 (or simply "rotator 301") and a light splitter mode-coupling structure 302 (or simply "splitter 302"). The rotator 301 couples an input TM 11 TE mode 21 , so that one input light eigenmode obtains a polarization rotation while the other input light eigenmode does not. 11 The TE polarization of the two different eigenmodes provided by rotator 301 is preserved. Splitter 302 is configured to preserve the TE polarization of the two different eigenmodes provided by rotator 301, but split the eigenmodes to provide them to different corresponding output ports 305 and 307, as described in more detail below. The multi-core structure of rotator 301 may have (1) a chevron style arrangement with two temporary core structures in a layer below the main core structure as shown in cross section 308A in horizontal plane 310, or alternatively (2) an inverted chevron style arrangement with two temporary core structures in a layer above the main core structure as shown in cross section 308B in horizontal plane 310.

[0042] FIG. 3B shows mode profile cross-sections at different locations along rotator 301 for three different eigenmodes of rotator 301 (mode 1, mode 2, and mode 3). Each mode profile image represents the electric field intensity across the cross-sectional plane indicated by dashed lines 312-A through 312-H. At the left (input) side of rotator 301, the first eigenmode (mode 1) is tuned to the TE of the input waveguide structure, which starts from a single core that is graded to a larger size on the right side as shown. 11 Mode 1 corresponds to the TE mode. The structure of the rotator 301 changes as additional cores move in and overlap, then the width tapers up and down, then moves out until the cores no longer overlap. Mode 2 corresponds to the TE mode over the entire length of the rotator 301. 11 There is also a second eigenmode (mode 2) on the left side of the rotator 301. This is the TM 11 Start as mode and TE on the right 21 Also shown in FIG. 3B is a theoretical mode profile of a third-order eigenmode (mode 3) that is assumed to have no energy for the input lightwave used with the PSR device 300. However, on the left side, the TE 21 Start as mode and TM on the right 11 The presence of these higher-order eigenmodes that evolve into modes contributes to mode hybridization.

[0043] The perturbation introduced by a pair of temporary core structures in other layers adjacent to the main core structure (either below as in cross section 308A or above as in cross section 308B) causes the top-bottom symmetry to be broken, resulting in the TM 11 Mode and TE 21 Thus, by the process of adiabatic transition, the TM of mode 2 11 The mode profile is TE through a gradual change in the hybridized mode profile. 21The mode profiles can be developed as follows. Examples of hybridized mode profiles for cross sections 312-C, 312-D, and 312-E of eigenmodes mode 1 and mode 2 are shown in FIG. 3C. These contain significant energy in the core structure of both layers. The front cross sections (312-A and 312-B) and back cross sections (312-F, 312-G, and 312-H) correspond to adiabatic transitions to and from the hybridized modes, respectively, and contain significant energy in the primary core structure.

[0044] 3C shows cross-sections of the mode profile at different locations along the splitter 302 for four different eigenmodes of splitter 302 (mode 1, mode 2, mode 3, and mode 4). Splitter 302 includes a lateral core structure with output port 307 in the same layer as the main core structure with output port 305. To achieve PSR functionality, the lateral core structure is used to split the two eigenmodes in the main core structure from rotator 301 into two different output waveguides at output ports 305 and 307. Mode 1 of rotator 301 corresponds to mode 1 of splitter 302, where cross sections 312-H and 314-A of the main core are aligned and propagate to output port 305 of the main core structure. Mode 2 of rotator 301 corresponds to mode 2 of splitter 302, where main core cross section 312-H and cross section 314-A coincide, and is evanescently coupled to lateral core structure output port 307. Mode 3 of splitter 302 (no energy in the input light) represents the mode at the input of the lateral core structure at cross section 314-A, and is evanescently coupled to main core structure output port 305. Mode 3 of rotator 301 corresponds to mode 4 of splitter 302 (no energy in the input light), where main core cross section 312-H and cross section 314-A coincide, and propagates to output port 305. TE 11 Mode 1, the fundamental eigenmode having a mode profile, remains in the primary core even after leaving the output port 305, while the other eigenmode, mode 2, is TE in the primary core. 21 Starting from the mode profile, the TE in the lateral core exiting the output port 307 11The introduction of another core in the splitter 302 breaks the in-plane symmetry of the waveguide structure. Thus, the TE of the wide main core 21 The mode is the TE of the narrow lateral core 11 Mode hybridized with the wide leading core TE 21 The mode is transformed into a narrow lateral core via adiabatic transformation. 11 mode and isolated from the main core with minimal losses.

[0045] 3B and 3C all show the electric field strength for light starting at the illustrated eigenmode (i.e.

number

[0046] To further illustrate the adiabatic transition between the different transverse mode profiles for different eigenmodes, FIG. 3D shows a simulation of a waveguide structure 320 implementing the PSR device 300 and the evolution of the effective refractive index of the supported eigenmodes. Mode 1 has a TE 11 The two hybridized regions 321 and 322 are examples of mode hybridization that associate the effective refractive index of one eigenmode with a similar magnitude to the effective refractive index of the other eigenmode. The first hybridized region 321 provides a TM 11 Mode and TE 21 The second hybridization region 322 allows the TE of the wide main core (C1) to mode 2 as described above. 21 Mode and TE of the narrow lateral core (C2) 11 Transitions between modes are possible.

[0047] Other techniques and device structures can also be used to fabricate a PSR. Figure 4A shows another exemplary PSR device 400. Rotation in one structure, such as in PSR device 300 (basic TM 11 Mode to TE 21 Instead of splitting in the multi-core waveguide structure (TM) and subsequent structures, the PSR device 400 11 TE of different structures from the mode 21 The mode transition allows for effective simultaneous rotation and splitting of polarization in the multi-core waveguide structure. The operation of the PSR device 400 will be described with reference to a first mode-coupling structure 401 and a second mode-coupling structure 402, which include a lower wide core structure (C1) and an upper narrow core structure (C2) as shown in cross section 404 in a horizontal plane 406, and two lateral core structures (C3, C4). There is an input port 408 that receives and directs light into the core C3, and two output ports 410 and 412 that provide rotated (co-polarized) and split portions of the output light.

[0048] FIG. 4B shows the mode transition in the first mode-coupling structure 401. By slowly grading the width of the core C1, the TM of the lateral core C3 11 The mode is the TE of the multicore structure including the cores C1 and C2. 21 mode and eventually the TE of the lateral core C3 with an adiabatic transition. 21 The modes evolve and are output at output port 410 (FIG. 4A). The mode profiles at cross sections 414-A and 414-B are shown for four eigenmodes: mode 1, mode 2, mode 3, and mode 4. Note that the output light contains energy only in modes 2 and 4 at input port 408.

[0049] The effective refractive indices (n eff The corresponding evolution of the TE of mode 2 is shown in FIG. 4C, where the transition between the different transverse mode profiles is shown. 11 Mode 4 is maintained in core C3.11 The mode evolves through modal hybridization into the TE21 mode of the C1 / C2 multicore structure.

[0050] 4D shows the mode transition in the second mode-coupling structure 402. By further grading the width of the core C1, the TE of the multi-core structure including the cores C1 and C2 can be improved. 21 The mode is TE of the lateral core C4. 11 mode and eventually the TE of the lateral core C4 with an adiabatic transition. 11 mode and is output to output port 412.

[0051] The corresponding evolution of the effective refractive index of the different eigenmodes of the mode-coupling structure 402 is shown in FIG. 4E. In FIG. 4E, the transition between the different transverse mode profiles is shown. The TE of mode 3 21 Mode TE of Core C4 via Mode Hybridization 11 progresses to mode.

[0052] In addition to the exemplary embodiments described herein, for an on-chip PSR device, a basic mode (e.g., TM 11 modes) and higher-order TE modes (e.g., second-order TE 21 ) are possible. A multi-core waveguide structure can be formed using two or more layers, or it can be formed using a single layer by partial etching of the layer used to form the multi-core structure. For example, a single layer can be etched from the top and bottom to form adjacent core structures as shown in FIG. 1C and FIG. 1C.

[0053] While the present disclosure has been described in connection with certain embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all modifications and equivalent structures permitted under law.

Claims

1. An apparatus comprising: a photonic integrated circuit (PIC) including a plurality of optical waveguides; a polarization rotator structure integrated into the PIC and having a first end optically coupled to at least one of the plurality of optical waveguides; a light splitter structure integrated in the PIC and having a first end optically coupled to a second end of the polarization rotator structure; Including, The polarization rotator structure comprises: a first core structure formed in the first layer; a second core structure formed in a second layer present at a depth different from that of the first layer and formed adjacent to the first core structure; Including, the first core structure extends from a first end to a second end of the polarization rotator structure; the first core structure and the second core structure provide mode hybridization of at least two orthogonally polarized waveguide modes of the polarization rotator structure; the first layer and the second layer are separated by a third layer comprising a material having a refractive index different from a core material of the first core structure and a core material of the second core structure, and / or the core material of the first core structure has a refractive index different from a core material of the second core structure; the optical splitter structure includes a first core structure and a second core structure; a first core structure of the light splitter structure is contiguous with at least one of a first core structure or a second core structure of the polarization rotator structure such that the first core structure of the light splitter structure is formed in the first layer or the second layer; a second core structure of the light splitter structure is separate from both the first core structure and the second core structure of the polarization rotator structure; An apparatus, wherein a second core structure of the light splitter structure is laterally separated from a first core structure of the polarization rotator structure at the same layer as the first core structure of the polarization rotator structure.

2. The first core structure and the second core structure of the polarization rotator structure are TM of the first core structure. １１ Mode and TE of the first core structure ２１ The apparatus of claim 1 , which provides mode hybridization with the mode.

3. 2. The apparatus of claim 1 , wherein the second core structure of the polarization rotator structure includes at least two separate continuous portions of core material extending across at least a portion of the distance between the first end of the polarization rotator structure and the second end of the polarization rotator structure.

4. An article obtained by manufacturing, at least one cladding material providing cladding for the plurality of optical waveguides; a core material providing cores for the plurality of optical waveguides; a first mode-coupling structure having a first end optically coupled to at least one optical waveguide formed in the cladding material; a second mode coupling structure; Including, a first end of the second mode-coupling structure optically coupled to a second end of the first mode-coupling structure, the second end of the second mode-coupling structure optically coupled to at least two optical waveguides formed in the cladding material; the core material includes at least one material having a refractive index higher than a refractive index of the cladding material; The first mode coupling structure comprises: a first core structure formed in the first layer; a second core structure formed in a second layer present at a depth different from that of the first layer and formed adjacent to the first core structure; Including, the first core structure includes at least one continuous portion of the core material extending from a first end to a second end of the first modal coupling structure; the second core structure includes at least two separate continuous portions of core material extending across at least a portion of the distance between a first end of the first modal coupling structure and a second end of the first modal coupling structure; the at least two distinct contiguous portions of core material of the second core structure are laterally separated by a material having a refractive index different from that of the core material; The second mode coupling structure comprises: a third core structure including a portion of the core material contiguous with at least one of the first core structure or the second core structure; a fourth core structure including a portion of the core material laterally separated from the core material of both the first core structure and the second core structure in the first layer or the second layer; Including, articles.

5. 5. The article of claim 4, wherein the first core structure and the second core structure provide mode hybridization between a fundamental mode of the first core structure having a first polarization and a non-fundamental mode of the first core structure having a second polarization orthogonal to the first polarization.

6. The article of claim 5 , wherein said portion of core material of said third core structure is contiguous with said continuous portion of core material of said first core structure.

7. 7. The article of claim 6, wherein the second mode-coupling structure includes a portion of the third core structure and the fourth core structure that are proximate to one another over a distance that provides evanescent coupling between the non-fundamental mode received at the third core structure and a fundamental mode of the fourth core structure, and preserves the fundamental mode of the third core structure without evanescent coupling with the fourth core structure.

8. 6. The article of claim 5, wherein the continuous portion of core material of the first core structure has a width that increases over at least a portion of the distance between the first end of the first modal coupling structure and the second end of the first modal coupling structure.

9. 9. The article of claim 8, wherein the two separate continuous portions of core material of the second core structure have substantially equal widths that increase over a first distance and decrease over a second distance.

10. The fundamental mode of the first core structure is TM １１ Includes modes, The non-fundamental mode of the first core structure is TE ２１ The article of claim 5 comprising a mode.

11. 6. The article of claim 5, wherein said mode hybridization is based on a substantially equal magnitude of effective refractive index of said fundamental mode of said first core structure and an effective refractive index of said non-fundamental mode of said first core structure.

12. 5. The article of claim 4, wherein the first core structure and the second core structure provide mode hybridization between a fundamental mode of the first core structure having a first polarization and a non-fundamental mode of the second core structure having a second polarization orthogonal to the first polarization.

13. 13. The article of claim 12, wherein the portion of core material of the third core structure is contiguous with the continuous portion of core material of the first core structure and is contiguous with one of the two separate continuous portions of core material of the second core structure.

14. 14. The article of claim 13, wherein the second mode-coupling structure includes a portion of the third core structure and the fourth core structure that are proximate to one another over a distance that provides evanescent coupling between the non-fundamental mode received at the third core structure and a fundamental mode of the fourth core structure, and preserves the fundamental mode of the third core structure without evanescent coupling with the fourth core structure.

15. 13. The article of claim 12, wherein the continuous portion of core material of the first core structure has a substantially constant width between the first end of the first modal coupling structure and the second end of the first modal coupling structure.

16. 16. The article of claim 15, wherein one of the two separate continuous portions of core material of the second core structure vertically overlaps the continuous portion of core material of the first core structure, and one of the two separate continuous portions of core material of the second core structure does not vertically overlap the continuous portion of core material of the first core structure.

17. The fundamental mode of the first core structure is TM １１ modes, and the non-fundamental modes of the first core structure are TE ２１ 13. The article of claim 12 comprising a mode.

18. 1. A method of manufacturing a polarization splitter rotator, comprising the steps of: providing at least one cladding material providing cladding for a plurality of optical waveguides; forming a waveguide in the cladding material using a core material comprising at least one material having a refractive index higher than a refractive index of the cladding material; forming a first mode-coupling structure having a first end optically coupled to at least one optical waveguide formed in the cladding material; forming a second mode-coupling structure; Including, The first mode coupling structure comprises: a first core structure formed in the first layer; a second core structure formed in a second layer present at a depth different from that of the first layer and formed adjacent to the first core structure; Including, the first core structure includes at least one continuous portion of the core material extending from a first end to a second end of the first modal coupling structure; the second core structure includes at least two separate continuous portions of core material extending across at least a portion of the distance between a first end of the first modal coupling structure and a second end of the first modal coupling structure; the at least two distinct contiguous portions of core material of the second core structure are laterally separated by a material having a refractive index different from that of the core material; a first end of the second mode-coupling structure optically coupled to a second end of the first mode-coupling structure, the second end of the second mode-coupling structure optically coupled to at least two optical waveguides formed in the cladding material; the second modal coupling structure includes a third core structure including a portion of the core material contiguous with a core material of at least one of the first core structure or the second core structure; a fourth core structure including a portion of the core material laterally separated from the core material of both the first core structure and the second core structure in the first layer or the second layer; A method comprising:

19. 20. The method of claim 18, wherein the first core structure and the second core structure provide mode hybridization between a fundamental mode of the first core structure having a first polarization and a non-fundamental mode of the first core structure having a second polarization orthogonal to the first polarization.

20. 20. The method of claim 18, wherein the first core structure and the second core structure provide mode hybridization between a fundamental mode of the first core structure having a first polarization and a non-fundamental mode of the second core structure having a second polarization orthogonal to the first polarization.

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