A hybrid integrated multimode waveguide coupler

Abstract

The present invention discloses a hybrid integrated multimode waveguide coupler, which belongs to the field of optoelectronic communication devices. The coupler includes a mode multiplexing three-dimensional integrated waveguide, a mode demultiplexer and a single-mode array connector, which are used to realize the coupling conversion of multiple modes in a multimode waveguide and a few-mode optical fiber. The mode demultiplexer can convert the high-order mode in the multimode waveguide into the fundamental mode of different channels, further couple it to the mode multiplexing three-dimensional integrated waveguide through the single-mode array connector, and finally use the mode multiplexing three-dimensional integrated waveguide to multiplex the fundamental mode into the corresponding mode in the few-mode optical fiber. The hybrid integrated multimode waveguide coupler can realize the coupling conversion of multiple modes between the multimode waveguide and the few-mode optical fiber, has the characteristics of compatible polarization multiplexing, simple process, high coupling efficiency, etc., and meets the actual needs of the fields of multi-mode optical fiber communication and on-chip communication.

Description

Technical Field

[0001] The present invention belongs to the field of optical interconnection communication, and more specifically, relates to a hybrid integrated multi-mode waveguide coupler. Background Art

[0002] Advanced multiplexing technology can transmit multiple signals simultaneously, which is of great significance to meet the growing demand for large-capacity optical interconnection. The optical field has multiple physical dimension resources, which can be used to realize various multiplexing technologies, demonstrating the feasibility of ultra-large capacity optical communication, such as wavelength division multiplexing (WDM) using wavelength dimension, time division multiplexing (TDM) using time dimension, polarization division multiplexing (PDM) using polarization dimension, and advanced modulation formats using amplitude and phase dimensions. In the past few decades, the above multiplexing technologies have achieved rapid development and continuously promoted the improvement of transmission capacity of optical communication networks. However, the existing optical field dimension resources will also face the problem of near-limit development and utilization. At the same time, in order to solve the predicted "capacity bottleneck" in single-mode optical fiber communication networks, mode division multiplexing (MDM) uses different spatial orthogonal modes in multimode waveguides / optical fibers to simultaneously transmit different signals, greatly improving the capacity of optical communication systems.

[0003] For optical fiber-based optical communication networks, mode division multiplexing technology has become an effective way to further improve the transmission capacity of optical fiber communication. Single-mode multi-core fiber (MCF), multi-mode fiber (MMF) and their hybrid combination of few-mode multi-core fiber (FM-MCF) have demonstrated ultra-high capacity data transmission. Among them, since few-mode fiber (FMF) can avoid the difficulty of controlling high-order modes in traditional multi-mode fiber (MMF), weak coupling MDM technology based on few-mode fiber has attracted widespread attention. In addition, by introducing the spatial mode parallel dimension into silicon photonic integrated circuits (PICs), mode division multiplexing can significantly expand the communication density of on-chip interconnects and also has great potential in multi-mode optical communications. For on-chip mode division multiplexing systems, integrated mode (de)multiplexers are key devices for efficient conversion, excitation and (de)multiplexing of guided modes. Silicon photonics is considered to be one of the most outstanding integrated photonic platforms because of its unique advantages such as strong light confinement, small size and mature complementary metal oxide semiconductor (CMOS) compatible technology. Currently, silicon-based mode (de)multiplexers can also be manufactured through mature manufacturing technologies, such as adiabatic couplers, asymmetric Y-junctions, asymmetric directional couplers (ADCs), and reverse-engineered photonic chips. Although there has been a lot of work on chip-level or fiber-based MDM technology, efficient multimode couplers as a bridge connecting on-chip multimode waveguides and few-mode fibers remain a challenging task due to the mismatch in size and shape between multimode waveguides and few-mode fiber modes.

[0004] In order to overcome the above challenges, some integrated schemes for coupling multimode waveguides and few-mode fibers have been proposed, which can be divided into vertical coupling schemes and end-face coupling schemes. For the vertical coupling scheme, the two-dimensional grating coupler is a common device because of its large process tolerance and small footprint. However, the special defects of the grating, namely limited bandwidth and large insertion loss, greatly limit the application of the two-dimensional grating coupler. In contrast, the end-face coupling scheme theoretically has a wider operating bandwidth, lower coupling loss and more compact packaging. It is reported that the three-point inverted cone structure with a 1×3 splitter can achieve efficient four-mode coupling with a large operating bandwidth range, but the number of coupled modes is theoretically difficult to increase. In addition, the multi-stage inverted cone coupler based on heterogeneous waveguides can achieve direct coupling of six guided modes, but its wavelength sensitivity hinders its further application. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of the present invention is to provide a hybrid integrated multimode waveguide coupler, which aims to solve the coupling problem of multimode waveguide and few-mode optical fiber. It uses a mode-multiplexed three-dimensional integrated waveguide, which is of great significance for multimode optical communication.

[0006] To achieve the above-mentioned purpose, the present invention provides a hybrid integrated multimode waveguide coupler, comprising a mode demultiplexer, a single-mode array connector and a mode multiplexing three-dimensional integrated waveguide connected in sequence, for realizing the coupling conversion of multiple modes in a multimode waveguide and a few-mode optical fiber. One end of the mode demultiplexer is connected to a multimode silicon-based waveguide, which can convert the high-order mode in the multimode waveguide into a fundamental mode of different channels, and further couple it to the mode multiplexing three-dimensional integrated waveguide through a single-mode array connector, and finally use the output port of the mode multiplexing three-dimensional integrated waveguide to connect to the few-mode optical fiber, and multiplex the fundamental mode into the corresponding mode in the few-mode optical fiber.

[0007] Preferably, the mode-multiplexing three-dimensional integrated waveguide is processed on transparent material chips such as glass, crystal and optical ceramics using femtosecond laser direct writing technology to achieve mode multiplexing and couple the mode into few-mode optical fiber.

[0008] Furthermore, the mode demultiplexer may adopt an asymmetric Y-branch structure, a reverse design structure or an asymmetric directional coupling structure to demultiplex multiple modes in a multimode waveguide into fundamental modes of different channels. Preferably, the asymmetric directional coupling structure includes a multimode coupled waveguide, a single-mode coupled waveguide, an input multimode straight waveguide, an output multimode straight waveguide, a single-mode input curved waveguide and a single-mode output S-type waveguide; the single-mode input curved waveguide, the multimode coupled waveguide and the single-mode output S-type waveguide are connected in sequence, the input multimode straight waveguide, the single-mode coupled waveguide and the output multimode straight waveguide are connected in sequence, and a preset spacing is maintained with the single-mode input curved waveguide, the multimode coupled waveguide and the single-mode output S-type waveguide.

[0009] Furthermore, the single-mode array connector may adopt a strip waveguide inverted cone structure or a slot waveguide inverted cone structure, which may achieve efficient coupling of the transverse electric fundamental mode and the transverse magnetic fundamental mode.

[0010] Furthermore, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-independent, the multimode waveguide coupler can realize the same-order mode coupling conversion of arbitrary polarization in the multimode waveguide and the few-mode optical fiber.

[0011] Furthermore, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-dependent, the multimode waveguide coupler can realize coupling conversion corresponding to different modes with different polarizations in the multimode waveguide and the few-mode optical fiber.

[0012] Furthermore, the mode multiplexing three-dimensional integrated waveguide includes a single-mode input waveguide, a three-dimensional transition region coupling waveguide and a few-mode output waveguide. First, the single-mode tapered input waveguide is a tapered waveguide, which is arranged linearly and evenly, and then slowly transformed into a triangular arrangement, and then an adiabatic slow-changing method is used to couple and distribute power through the three-dimensional transition region coupling waveguide, and finally multiplexed into different modes in the few-mode fiber and coupled to the few-mode fiber.

[0013] Furthermore, the mode demultiplexing device can be processed on a silicon-based platform, the silicon waveguide thickness of the polarization-dependent mode demultiplexer is 220 nm, and the silicon waveguide thickness of the polarization-independent mode demultiplexer is greater than 220 nm.

[0014] Furthermore, the multimode waveguide coupler can realize the corresponding coupling conversion of 6 or 10 or even more modes in the multimode waveguide and the few-mode fiber, wherein the 6 modes include TE0, TM0, TE1, TM1, TE2, TM2 modes in the multimode waveguide and LP in the few-mode fiber. 01 x , L.P. 01 y , L.P. 11a x , L.P. 11a y , L.P. 11b x , L.P. 11b y Mode; the 10 modes include TE0, TM0, TE1, TM1, TE2, TM2, TE3, TM3, TE4, TM4 modes in multimode waveguide and LP in few-mode fiber 01 x , L.P. 01 y , L.P. 11a x , L.P. 11a y , L.P.11b x , L.P. 11b y , L.P. 21a x , L.P. 21a y , L.P. 21b x , L.P. 21b y model.

[0015] Through the above technical solution conceived by the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The hybrid integrated multimode waveguide coupler proposed in the present invention uses a mode multiplexing three-dimensional integrated waveguide as a multiplexer of the few-mode fiber mode. The waveguide is processed on glass, crystal or optical ceramics using femtosecond laser processing technology, with low loss, low crosstalk, simple process, low cost, and can be mass-produced; and the existing silicon-based device processing technology is mature. Therefore, the hybrid integrated multimode coupler has a high feasibility for factory mass production.

[0017] 2. The reported multimode waveguide and few-mode fiber couplers, whether using vertical coupling or end-face coupling, have a limited number of coupled modes, but this is a challenge for multimode couplers with more modes. In contrast, the mode coupling number of the hybrid integrated multimode waveguide coupler proposed in the present invention depends on the mode number of the silicon-based demultiplexer or the mode multiplexing three-dimensional integrated waveguide, which is more than the mode number of the reported multimode coupler, and the mode coupling number of the multimode coupler is scalable, which is of great significance and has more application scenarios for multimode optical communication networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a hybrid integrated multimode waveguide coupler provided by the present invention.

[0019] Figure 2 It is a schematic diagram of the structure of a polarization-independent hybrid integrated multimode waveguide coupler.

[0020] Figure 3 It is a structural diagram of the mode demultiplexer.

[0021] Figure 4 It is a schematic diagram of the structure of a polarization-dependent hybrid integrated multimode waveguide coupler.

[0022] Figure 5 It is a schematic diagram of the structure of a single-mode connector. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] The present invention provides a hybrid integrated multimode waveguide coupler, comprising a mode demultiplexer, a single-mode array connector and a mode multiplexing three-dimensional integrated waveguide connected in sequence, for realizing the coupling conversion of multiple modes in a multimode waveguide and a few-mode optical fiber. One end of the mode demultiplexer is connected to a multimode silicon-based waveguide, which can convert the high-order mode in the multimode waveguide into a fundamental mode of different channels, further coupled to the mode multiplexing three-dimensional integrated waveguide through a single-mode array connector, and finally connected to the few-mode optical fiber using the output port of the mode multiplexing three-dimensional integrated waveguide to multiplex the fundamental mode into the corresponding mode in the few-mode optical fiber.

[0025] Specifically, the mode-multiplexing three-dimensional integrated waveguide uses femtosecond laser direct writing technology and is processed on transparent material chips such as glass, crystal and optical ceramics to achieve mode multiplexing and couple the mode into few-mode optical fiber.

[0026] Specifically, the mode demultiplexer may adopt an asymmetric Y-branch structure, a reverse design structure or an asymmetric directional coupling structure to demultiplex multiple modes in a multimode waveguide into fundamental modes of different channels.

[0027] Specifically, the single-mode array connector can adopt a strip waveguide inverted cone structure or a slot waveguide inverted cone structure, which can achieve efficient coupling of the transverse electric fundamental mode and the transverse magnetic fundamental mode.

[0028] Specifically, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-independent, the multimode waveguide coupler can realize the same-order mode coupling conversion of arbitrary polarization in the multimode waveguide and the few-mode optical fiber, and the waveguide thickness of the mode demultiplexer is 340nm.

[0029] Specifically, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-dependent, the multimode waveguide coupler can realize the coupling conversion corresponding to different modes with different polarizations in the multimode waveguide and the few-mode optical fiber, and the waveguide thickness of the mode demultiplexer is 220nm.

[0030] Specifically, the mode multiplexing three-dimensional integrated waveguide includes a single-mode input waveguide, a three-dimensional transition region coupling waveguide and a few-mode output waveguide. First, the single-mode tapered input waveguide is a tapered waveguide, which is arranged linearly and evenly, and then slowly transformed into a triangular arrangement, and then an adiabatic slow-changing method is used to couple and distribute power through the three-dimensional transition region coupling waveguide, and finally multiplexed into different modes in the few-mode fiber and coupled to the few-mode fiber.

[0031] Specifically, the multimode waveguide coupler can realize the corresponding coupling conversion of 6 or 10 or even more modes in the multimode waveguide and the few-mode fiber, wherein the 6 modes include TE0, TM0, TE1, TM1, TE2, TM2 modes in the multimode waveguide and LP in the few-mode fiber. 01 x , L.P. 01 y , L.P. 11a x , L.P. 11a y , L.P. 11b x , L.P. 11b y Mode; the 10 modes include TE0, TM0, TE1, TM1, TE2, TM2, TE3, TM3, TE4, TM4 modes in multimode waveguide and LP in few-mode fiber 01 x , L.P. 01 y , L.P. 11a x , L.P. 11a y , L.P. 11b x , L.P. 11b y , L.P. 21a x , L.P. 21a y , L.P. 21b x , L.P. 21b y model.

[0032] Example

[0033] The present invention discloses a hybrid integrated multimode waveguide coupler, which belongs to the field of optical computing. It includes a mode demultiplexer I, a single-mode array connector II and a mode multiplexing three-dimensional integrated waveguide III. Figure 1As shown. The coupler can solve the problem of mismatch in size and shape between multiple modes in multimode waveguides and few-mode fibers, and can realize the coupling conversion of multiple modes in multimode waveguides and few-mode fibers. The mode demultiplexer I, one end of which is connected to a multimode silicon-based waveguide, can couple and convert the high-order modes in the silicon-based multimode waveguide into the fundamental mode of a single-mode waveguide. Then, it is further coupled to the mode multiplexing three-dimensional integrated waveguide III through a single-mode array connector II, and finally the fundamental mode is multiplexed into the corresponding mode in the few-mode fiber using the mode multiplexing three-dimensional integrated waveguide. Then the single-mode array connector is also located on the silicon-based platform, which is used to connect the single-mode output waveguide of the mode demultiplexer and the single-mode input waveguide of the mode multiplexing three-dimensional integrated waveguide. Finally, the output port of the mode multiplexing three-dimensional integrated waveguide is connected to the few-mode fiber, which can realize the function of mode multiplexing, excite the fundamental mode into the corresponding high-order mode in the few-mode fiber, and couple it to the few-mode fiber.

[0034] Specifically, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-independent, the multimode coupling device can realize the multimode waveguide (TE0 / TM0, TE1 / TM1, TE2 / TM2) and the few-mode fiber (LP 01 x / y , L.P. 11a x / y , L.P. 11b x / y ) The same-order mode coupling conversion of arbitrary polarization, such as Figure 2 As shown. The waveguide thickness of the mode demultiplexer is 340nm. The silicon-based mode multiplexer in the multimode coupler adopts a two-stage double-tapered asymmetric directional coupler structure, including a tapered multimode coupling waveguide 2, a tapered single-mode coupling waveguide 5, an input multimode straight waveguide 4, an output multimode straight waveguide 6, a single-mode input curved waveguide 1 and a single-mode output S-type waveguide 3, as shown Figure 3 As shown. The parameters of the double-tapered asymmetric directional coupler structure corresponding to TE2 / TM2 are: w1 = 0.15μm, w2 = 0.25μm, w3 = 1μm, w4 = 0.79μm, gap = 0.2μm, L = 100μm; the parameters of the double-tapered asymmetric directional coupler structure corresponding to TE1 / TM1 are: w1 = 0.18μm, w2 = 0.28μm, w3 = 0.63μm, w4 = 0.4μm, gap = 0.2μm, L = 100μm. The parameters of the polarization-independent mode multiplexing three-dimensional integrated waveguide are: the diameter of all single-mode waveguides is about 9μm, the diameter of all multi-mode waveguides is about 15μm; the diameter of the tapered single-mode input waveguide input port is about 5μm.

[0035] Specifically, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-dependent, the multimode coupling device can realize multimode waveguide (TE0, TM0, TE1, TM1, TE2, TM2) and few-mode fiber (LP 01x , L.P. 01 y , L.P. 11a x , L.P. 11a y , L.P. 11b x , L.P. 11b y ) The coupling conversion corresponding to different modes with different polarizations, such as Figure 4 As shown. The silicon-based mode multiplexer in the multimode coupler adopts a four-stage double-taper asymmetric directional coupler structure. Among them, the TE2 and TM2 modes are demultiplexed into two polarization fundamental modes through two cascaded double-taper asymmetric directional coupler structures and coupled to two adjacent channels. The TE1 and TM1 modes are demultiplexed into two polarization fundamental modes through another two cascaded double-taper asymmetric directional coupler structures and coupled to two adjacent channels. Finally, the TE0 and TM0 modes are separated into two adjacent channels through a polarization beam splitter. The polarization-related mode multiplexing three-dimensional integrated waveguide is divided into two parts. One part is to realize the polarization beam combining function, and the input adjacent different polarization fundamental modes are combined into a single-mode waveguide through a polarization beam combiner. The other part is to realize the mode multiplexing function, multiplexing the fundamental modes in multiple channels into multiple modes in the multimode waveguide, and finally coupling them into the few-mode fiber. The diameter size of the multimode waveguide matches the diameter of the few-mode fiber, which can realize low-loss mode coupling.

[0036] Specifically, the single-mode array connector can adopt a strip waveguide inverted cone structure or a slot waveguide inverted cone structure, such as Figure 5 As shown, the strip waveguide inverted cone structure includes an input straight waveguide 7 and a cone waveguide 8, and the slot waveguide inverted cone structure includes an input straight waveguide 9, an asymmetric slot waveguide 10 and a symmetric slot waveguide 11. The slot waveguide inverted cone structure used in this embodiment can achieve efficient coupling of the TE0 mode and the TM0 mode, thereby reducing the loss of the multimode coupler. The slit width and waveguide width of the symmetrical slot waveguide 11 are both changing. The closer to the coupling boundary, the larger the waveguide slit and the smaller the waveguide width; the asymmetric slot waveguide 10 has a constant waveguide slit and a changing waveguide width, which is used to achieve waveguide docking of the slot waveguide and the strip waveguide, and has the characteristics of low loss, thereby reducing the loss of the multimode coupler.

[0037] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A hybrid integrated multimode waveguide coupler, characterized in that: The invention comprises a mode demultiplexer (I), a single-mode array connector (II) and a mode multiplexing three-dimensional integrated waveguide (III) which are connected in sequence to realize the connection coupling between a multi-mode waveguide and a few-mode optical fiber; the mode demultiplexer (I) has one end connected to the multi-mode waveguide to couple and convert the high-order mode in the multi-mode waveguide into a fundamental mode; the single-mode array connector (II) is used to connect the single-mode output waveguide of the mode demultiplexer (I) and the single-mode input waveguide of the mode multiplexing three-dimensional integrated waveguide (III) to realize the transmission of the fundamental mode; the output port of the mode multiplexing three-dimensional integrated waveguide (III) is connected to the few-mode optical fiber to realize mode multiplexing and excite the fundamental mode into the corresponding high-order mode in the few-mode optical fiber.

2. A hybrid integrated multimode waveguide coupler according to claim 1, characterized in that: The mode multiplexing three-dimensional integrated waveguide (III) adopts femtosecond laser direct writing technology and is processed on transparent materials to realize the mode, multiplexing the fundamental modes of different channels into multiple modes in the few-mode optical fiber.

3. The hybrid integrated multimode waveguide coupler according to claim 1, characterized in that: The mode demultiplexer (I) adopts an asymmetric Y-branch structure, a reverse design structure or an asymmetric directional coupling structure, and is used to demultiplex multiple modes in a multimode waveguide into fundamental modes of different channels.

4. The hybrid integrated multimode waveguide coupler according to claim 1, characterized in that: The single-mode array connector (II) adopts a strip waveguide inverted cone structure or a slot waveguide inverted cone structure.

5. The hybrid integrated multimode waveguide coupler according to claim 1, characterized in that: When the mode demultiplexer (I) and the mode multiplexing three-dimensional integrated waveguide (III) are polarization independent, the multimode waveguide coupler realizes the same-order mode coupling conversion of arbitrary polarization in the multimode waveguide and the few-mode optical fiber.

6. The hybrid integrated multimode waveguide coupler according to claim 1, characterized in that: When the mode demultiplexer (I) and the mode multiplexing three-dimensional integrated waveguide (III) are polarization-dependent, the multimode waveguide coupler realizes the coupling conversion corresponding to different modes with different polarizations in the multimode waveguide and the few-mode optical fiber.

7. A hybrid integrated multimode waveguide coupler according to claim 1 or 2, characterized in that: The mode multiplexing three-dimensional integrated waveguide (III) comprises a single-mode input waveguide, a three-dimensional transition region coupling waveguide and a few-mode output waveguide; the single-mode input waveguide is arranged linearly and evenly spaced, and the three-dimensional transition region coupling waveguide couples and distributes power in an adiabatic and gradual manner; the port size of the few-mode output waveguide matches the size of the few-mode optical fiber.

8. A hybrid integrated multimode waveguide coupler according to claim 1 or 3, characterized in that: The mode demultiplexer (I) is processed on a silicon-based platform, the waveguide thickness of the polarization-dependent mode demultiplexer is 220nm, the silicon waveguide thickness of the polarization-independent mode demultiplexer is greater than 220nm, and the waveguide thickness of the polarization-independent mode demultiplexer is 340nm.

9. The hybrid integrated multimode waveguide coupler according to claim 1, characterized in that: The multimode waveguide coupler is used to achieve interception coupling of 6 or 10 modes in the multimode waveguide and the few-mode optical fiber; the 6 modes include TE0, TM0, TE1, TM1, TE2, TM2 modes in the multimode waveguide and LP in the few-mode optical fiber. 01 x , L.P. 01 y , L.P. 11a x , L.P. 11a y , L.P. 11b x , L.P. 11b y Mode; the 10 modes include TE0, TM0, TE1, TM1, TE2, TM2, TE3, TM3, TE4, TM4 modes in multimode waveguide and LP in few-mode fiber 01 x , L.P. 01 y , L.P. 11a x , L.P. 11a y , L.P. 11b x , L.P. 11b y , L.P. 21a x , L.P. 21a y , L.P. 21b x , L.P. 21b y model.

10. The hybrid integrated multimode waveguide coupler according to claim 3, characterized in that: The asymmetric directional coupling structure comprises a multimode coupling waveguide (2), a single-mode coupling waveguide (5), an input multimode straight waveguide (4), an output multimode straight waveguide (6), a single-mode input curved waveguide (1) and a single-mode output S-type waveguide (3); the single-mode input curved waveguide (1), the multimode coupling waveguide (2) and the single-mode output S-type waveguide (3) are connected in sequence, and the input multimode straight waveguide (4), the single-mode coupling waveguide (5) and the output multimode straight waveguide (6) are connected in sequence, and a preset spacing is maintained with the single-mode input curved waveguide (1), the multimode coupling waveguide (2) and the single-mode output S-type waveguide (3).

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