Low-loss Y-branch optical waveguide device capable of being used for reverse transmission

Abstract

The invention provides a low-loss Y-branch optical waveguide device capable of being used for reverse transmission. The low-loss Y-branch optical waveguide device comprises a substrate; an insulating layer; the waveguide layer is etched to form a waveguide structure; the waveguide structure includes: an input waveguide; the first end of the connecting part is connected with the input waveguide; the first branch waveguide is adjacent to the second end of the connecting part, and the second branch waveguide is connected with the third end of the connecting part; the first output waveguide is connected with one end, far away from the connecting part, of the first branch waveguide, and the second output waveguide is connected with one end, far away from the connecting part, of the second branch waveguide; a first side edge of the connecting part realizes transition between the input waveguide and the first branch waveguide, and the first side edge is composed of a plurality of semicircular bulges which are arranged at equal intervals; and the second side edge of the connecting part realizes the transition between the input waveguide and the second branch waveguide, and the second side edge is composed of a plurality of semicircular bulges which are arranged at equal intervals.

Description

Technical Field

[0001] The present application relates to the technical field of integrated optoelectronic devices for optical communications, and in particular to a low-loss Y-branch optical waveguide device that can be used for reverse transmission. Background Art

[0002] With the development of the information society, people's production and life require higher and higher data transmission speeds and quantities, and the frequency of electrical interconnection is getting higher and higher, which has caused problems such as limited bandwidth, signal distortion, and large interference, and the realization of ultra-high-speed circuits has encountered bottlenecks. However, the emergence of optical communication has broken through this bottleneck, making long-distance high-speed communication possible, greatly facilitating people's production and life. Therefore, optical communication has become one of the most important scientific and technological advances in the 21st century.

[0003] Optical communication devices are the core foundation of optical communication systems and important components of optical transmission systems. Their technology is a strategic high technology with forward-looking, pioneering and exploratory characteristics in the field of optical communications. This technology represents the level and capability of a country in the field of optical communications.

[0004] Photonic integrated circuit technology (PIC) is the mainstream development direction of future optical devices and has been the focus of attention and research in the industry in recent years. Compared with the currently widely used discrete components, photonic integrated circuit technology has obvious advantages in size, power consumption, cost, reliability, etc., and is the mainstream development direction of future optical devices.

[0005] Lithium niobate crystal is a synthetic multifunctional material with excellent electro-optical, acousto-optical and nonlinear optical properties. It has high transmittance in both visible and near-infrared bands and is widely used in the field of integrated optics. Due to the high refractive index difference between lithium niobate and silicon dioxide, the integration and device performance of photonic devices based on LNOI (Lithium Niobate on Insulator) have been greatly improved, and it has become possible to realize multi-device integration using LNOI as a platform.

[0006] Y-branch waveguide is one of the important basic optical waveguide units in integrated optoelectronics. It is widely used in integrated optical devices such as optical couplers, optical modulators, multiplexers / demultiplexers, optical switches, and fiber optic gyroscope multifunctional chips. Its performance is directly related to the performance of these devices. In the traditional Y-branch structure, reverse single-ended transmission will cause large radiation loss. Summary of the invention

[0007] The purpose of this application is to provide a low-loss Y-branch optical waveguide device that can be used for reverse transmission, which is used in a modulator structure to achieve more efficient transmission. By designing the shape of the Y-junction, the radiation of the high-order mode at this position is improved, thereby effectively improving the transmittance during reverse transmission.

[0008] In order to solve the above technical problems, the technical solution adopted in this application is:

[0009] According to one aspect of the present invention, a Y-branch optical waveguide device which can be used for reverse transmission and has low loss is provided, comprising: a substrate; an insulating layer located on the substrate; and a waveguide layer located on the insulating layer, wherein the waveguide layer is etched to form a waveguide structure; wherein the waveguide structure comprises: an input waveguide; a connecting portion, wherein a first end of the connecting portion is connected to the input waveguide; a first branch waveguide and a second branch waveguide, wherein the first branch waveguide is adjacent to the second end of the connecting portion, and the second branch waveguide is connected to the third end of the connecting portion; and a first output waveguide and a second output waveguide, wherein the first output waveguide is connected to an end of the first branch waveguide away from the connecting portion, and the second output waveguide is connected to an end of the second branch waveguide away from the connecting portion; wherein a first side edge of the connecting portion realizes a transition between the input waveguide and the first branch waveguide, and the first side edge is composed of a plurality of semicircular protrusions arranged at equal intervals; and a second side edge of the connecting portion realizes a transition between the input waveguide and the second branch waveguide, and the second side edge is composed of a plurality of semicircular protrusions arranged at equal intervals.

[0010] Optionally, the radius of the semicircular protrusion gradually increases from the input waveguide to the first branch waveguide, and the radius of the semicircular protrusion gradually increases from the input waveguide to the second branch waveguide.

[0011] Optionally, the second end and the third end of the connecting portion are connected via a third side edge, and the third side edge is in an arc shape.

[0012] Optionally, the first branch waveguide and the second branch waveguide are bent in a cosine curve.

[0013] Optionally, a line width of the first branch waveguide is two-thirds of a line width of the input waveguide.

[0014] Optionally, the first output waveguide includes a first transition portion and a first output portion; the first transition portion connects the first branch waveguide and the second output portion; the second output waveguide includes a second transition portion and a second output portion; the second transition portion connects the second branch waveguide and the second output portion.

[0015] Optionally, the line width of one end of the first transition portion connected to the first branch waveguide is equal to the line width of the first branch waveguide, and the line width of one end of the first transition portion connected to the first output portion is equal to the line width of the first output portion; the line width of one end of the second transition portion connected to the second branch waveguide is equal to the line width of the second branch waveguide, and the line width of one end of the second transition portion connected to the second output portion is equal to the line width of the second output portion.

[0016] Optionally, the line width of the first branch waveguide is two-thirds of the line width of the first output portion, and the line width of the first transition portion gradually increases from the first branch waveguide to the first output portion; the line width of the second branch waveguide is two-thirds of the line width of the second output portion, and the line width of the second transition portion gradually increases from the second branch waveguide to the second output portion.

[0017] Optionally, the material of the waveguide structure is lithium niobate.

[0018] The advantages and positive effects of this application are:

[0019] The design of the wavy structure on both sides of the connection part in the embodiment of the present application can effectively smooth the gradual change process of the line width, change the propagation constant of each mode, promote the phase matching between the high-order mode and the fundamental mode, improve the coupling efficiency between different modes, and make a larger proportion of the high-order mode couple to the fundamental mode, thereby reducing the energy of the high-order mode radiation escape. In addition, since the line width of the waveguide will affect the cutoff frequency, the wider the waveguide, the lower the cutoff frequency, slowing down the trend of line width reduction can effectively postpone the position of the high-order mode cutoff, extend the coupling length, and reduce the radiation loss of the high-order mode outward at the connection part.

[0020] The present invention achieves at least 96% transmittance when a 1550nm light source is input in the forward direction, has a low loss of about 0.18db, and the splitting ratio can be stably maintained at 0.5:0.5. When inputting in the reverse single-end direction, the structure can still achieve a transmittance of more than 90%, which is close to the propagation efficiency when inputting in the forward direction. The structure can be applied to a double Y-branch structure and play a greater advantage in the modulator. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic perspective view of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to an embodiment of the present application is shown;

[0022] Figure 2 A schematic cross-sectional view of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to an embodiment of the present application is shown;

[0023] Figure 3A schematic top view of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to an embodiment of the present application is shown;

[0024] Figure 4 A schematic top view of a connection portion of a Y-branch optical waveguide device that can be used for reverse transmission and has low loss according to an embodiment of the present application is shown;

[0025] Figure 5 A schematic top view of a first output waveguide of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to an embodiment of the present application is shown;

[0026] Figure 6 A schematic top view of a second output waveguide of a Y-branch optical waveguide device with low loss and capable of reverse transmission according to an embodiment of the present application is shown;

[0027] Figure 7 The figure shows the mode field diagram of the output of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to the present invention when a 1550nm light source is input in the forward direction;

[0028] Figure 8 The figure shows the mode field diagram of the output of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to the present invention when a 1550nm light source is input in a reverse single-end manner. DETAILED DESCRIPTION

[0029] In order to better understand the present application, the present application is further described below in conjunction with specific embodiments and drawings.

[0030] Figure 1 A schematic perspective view of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to an embodiment of the present application is shown. Figure 2 A schematic cross-sectional view of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to an embodiment of the present application is shown. Figure 3 A schematic top view of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to an embodiment of the present application is shown.

[0031] See also Figure 1 and Figure 2 The optical waveguide device includes a substrate 7, an insulating layer 6 located on the substrate 7, and a lithium niobate layer 5 located on the insulating layer 6. The lithium niobate 5 is etched to form a plate layer portion 51 and a ridge-shaped waveguide structure 52, and the etching depth of the waveguide structure 52 is the same at all locations. Figure 1 and Figure 3 The waveguide structure 52 includes an input waveguide 1 , a connecting portion 2 , a first branch waveguide 31 and a second branch waveguide 32 , a first output waveguide 41 and a second output waveguide 42 .

[0032] The input waveguide 1 is a straight waveguide with a line width W.

[0033] Figure 4 A schematic top view of the connection portion of a Y-branch optical waveguide device that can be used for reverse transmission and has low loss according to an embodiment of the present application is shown, Figure 4 As shown, the connection part 2 is a "Y"-shaped structure, the first end 21 of the connection part 2 is connected to the input waveguide 1; the second end 22 of the connection part 2 is connected to the first branch waveguide 31, and the third end 23 of the connection part 2 is connected to the second branch waveguide 32. The first branch waveguide 31 and the second branch waveguide 32 are curved waveguides. Specifically, the first branch waveguide 31 and the second branch waveguide 32 are curved, for example, in a cosine curve. The end of the first branch waveguide 31 away from the connection part 2 is connected to the first output waveguide 41, and the end of the second branch waveguide away from the connection part 2 is connected to the second output waveguide 42. The line widths of the first branch waveguide 31 and the second branch waveguide 32 are respectively two-thirds of the line width of the input waveguide 1, for example, 2W / 3.

[0034] In this embodiment, the first branch waveguide 31 and the second branch waveguide 32 adopt a cosine curve, and the data points on the curve are taken using Matlab software, and then the model is drawn. Since the second end of the connecting portion is connected to the first branch waveguide 31, and the third end of the connecting portion 2 is connected to the second branch waveguide 32, the line width of the connecting portion 2 is approximately the sum of the line widths of the first branch waveguide 31 and the second branch waveguide 32. In order to reduce the difference between the sum of the line widths of the first end and the second end and the third end of the connecting portion 2, the line widths of the first branch waveguide 31 and the second branch waveguide 32 are reduced to two-thirds of the input waveguide 1.

[0035] The first end 21 and the second end 22 of the connecting portion 2 are connected via a first side edge 24, and the first side edge 24 of the connecting portion 2 realizes the transition between the input waveguide 1 and the first branch waveguide 31. The first side edge 21 is composed of a plurality of semicircular protrusions arranged at equal intervals, and the radius of the semicircular protrusions gradually increases from the input waveguide 1 to the first branch waveguide 31. The first end 21 and the third end 23 of the connecting portion 2 are connected via a second side edge 25, and the second side edge 25 of the connecting portion 2 realizes the transition between the input waveguide 1 and the second branch waveguide 32. The second side edge 25 is composed of a plurality of semicircular protrusions arranged at equal intervals, and the radius of the semicircular protrusions gradually increases from the input waveguide 1 to the second branch waveguide 32. The protrusions of the first side 24 and the second side 25 effectively smooth the line width change from the input waveguide 1 to the first branch waveguide 31, and the line width change from the input waveguide 1 to the second branch waveguide 32. When inputting in reverse direction, the efficiency of coupling the high-order mode to the fundamental mode can be improved. At the same time, the slowdown in the narrowing speed of the waveguide line width can effectively delay the position where the high-order mode is cut off, increase the coupling length between the high-order mode and the fundamental mode, and reduce the radiation loss of the high-order mode. The second end 22 and the third end 23 of the connecting portion 2 are connected via the third side 26, and the third side 26 is in an arc shape. The setting of the arc-shaped third side 26 increases the branching angle between the first branch waveguide 31 and the second branch waveguide 32.

[0036] Figure 5 A schematic top view of a first output waveguide of a low-loss Y-branch optical waveguide device that can be used for reverse transmission according to an embodiment of the present application is shown. Figure 6 FIG. 4 is a schematic top view of a second output waveguide of a Y-branch optical waveguide device with low loss and capable of reverse transmission according to an embodiment of the present application. Figure 5 and Figure 6As shown, the first output waveguide 41 includes a first transition portion 41a and a first output portion 41b; the first transition portion 41a connects the first branch waveguide 31 and the second output portion 41b, the first transition portion 41a is a tapered waveguide, the first output portion 41b is a linear waveguide, and the line width of the first transition portion 41a gradually increases from the first branch waveguide 31 to the first output portion 41b. The line width of the end of the first transition portion 41a connected to the first branch waveguide 31 is equal to the line width of the first branch waveguide 31, for example, 2W / 3, and the line width of the end of the first transition portion 41a connected to the first output portion 41b is equal to the line width of the first output portion 41b, for example, W. The second output waveguide 42 includes a second transition portion 42a and a second output portion 42b; the second transition portion 42a connects the second branch waveguide 32 and the second output portion 42b, the second transition portion 42a is a tapered waveguide, and the second output portion 42b is a linear waveguide. In the direction from the second branch waveguide 32 to the second output portion 42b, the line width of the second transition portion 42a gradually increases. The line width of the end of the second transition portion 42a connected to the second branch waveguide 32 is equal to the line width of the second branch waveguide 32, for example, 2W / 3, and the line width of the end of the second transition portion 42a connected to the second output portion 42b is equal to the line width of the second output portion 42b, for example, W.

[0037] The first output portion 41b has the same line width as the input waveguide 1 and is slightly larger than the line width of the first branch waveguide 31. The tapered first transition portion 41a realizes a smooth transition from the first branch waveguide 31 to the first output portion 41b. Similarly, the second output portion 42b has the same line width as the input waveguide 1 and is slightly larger than the line width of the second branch waveguide 32. The tapered second transition portion 42a realizes a smooth transition from the second branch waveguide 32 to the second output portion 42b.

[0038] Figure 7 FIG. 2 shows a mode field diagram of a Y-branch optical waveguide device outputted in the present invention which can be used for reverse transmission and has low loss when a 1550nm light source is input in the forward direction; Figure 7 As shown, the present invention achieves at least 96% transmittance when a 1550nm light source is input in the forward direction, has a low loss of about 0.18db, and the splitting ratio can be stably maintained at 0.5:0.5. When input in the forward direction, the splitting ratio is uniform, the transmittance is high, and a small part of the radiation escapes at the Y-junction, but the transmission loss can still be no higher than 0.18db.

[0039] Figure 8 FIG. 4 shows a mode field diagram of a Y-branch optical waveguide device for reverse transmission and low loss output according to the present invention when a 1550nm light source is input in reverse single-end mode; Figure 8As shown in the figure, in the case of reverse single-ended input, the structure can still achieve a transmittance of more than 90%, which is close to the propagation efficiency in the case of forward input. In the case of reverse single-ended input, although there is a small amount of radiation loss at the Y-junction position, the transmittance detected at the output end can still reach more than 90%, which is very close to the transmittance in the case of forward input. This structure can be applied to the double Y-branch structure and play a greater advantage in the modulator.

[0040] Therefore, it can be concluded that the Y-branch optical waveguide device which can be used for reverse transmission and has low loss can achieve a good beam splitting effect during forward input and a higher light field transmittance during forward and reverse input, and can be applied to some modulators to achieve high-efficiency and low-loss light field transmission.

[0041] In a traditional Y-branch structure, when light is transmitted in reverse to the Y-junction where the two branches meet, there will be a process in which the waveguide line width suddenly increases and then decreases. The waveguide line width suddenly increases to twice the original width, which will cause the transmission of light to not meet the continuity condition of the field, thereby exciting higher-order modes. The cutoff frequency of the higher-order mode is higher than the fundamental mode. As the waveguide line width gradually decreases, the higher-order mode will be cut off and scattered as a radiation mode. The intensity of the higher-order mode is the same as that of the fundamental mode, so a large radiation loss will be detected at the output end. In a traditional Y-branch structure, the radiation loss usually reaches 3db. In the present application, a plurality of semicircular protrusions arranged equidistantly are provided on the first side and the second side of the connecting portion 2 to form a wavy structure, so that the optical waveguide device of the present application has low loss and high transmittance during both forward and reverse input.

[0042] The above detailed description of the embodiments of the present application is only a preferred embodiment of the present application and cannot be considered to limit the scope of implementation of the present application. All equivalent changes and improvements made within the scope of the present application shall still fall within the scope of this patent.

Claims

1. A Y-branch optical waveguide device for reverse transmission and low loss, comprising: substrate; an insulating layer, located on the substrate; as well as A waveguide layer, located on the insulating layer, wherein the waveguide layer is etched to form a waveguide structure; Wherein, the waveguide structure comprises: Input waveguide; A connecting portion, a first end of which is connected to the input waveguide; a first branch waveguide and a second branch waveguide, the first branch waveguide being adjacent to the second end of the connecting portion, the second branch waveguide being connected to the third end of the connecting portion; and a first output waveguide and a second output waveguide, wherein the first output waveguide is connected to an end of the first branch waveguide away from the connecting portion, and the second output waveguide is connected to an end of the second branch waveguide away from the connecting portion; Among them, the first side of the connecting portion realizes the transition between the input waveguide and the first branch waveguide, and the first side is composed of a plurality of semicircular protrusions arranged at equal intervals; the second side of the connecting portion realizes the transition between the input waveguide and the second branch waveguide, and the second side is composed of a plurality of semicircular protrusions arranged at equal intervals.

2. The Y-branch optical waveguide device for reverse transmission and low loss according to claim 1, wherein: The radius of the semicircular protrusion gradually increases from the input waveguide to the first branch waveguide, and the radius of the semicircular protrusion gradually increases from the input waveguide to the second branch waveguide.

3. The Y-branch optical waveguide device for reverse transmission and low loss according to claim 1, wherein: The second end and the third end of the connecting portion are connected via a third side edge, and the third side edge is in an arc shape.

4. The Y-branch optical waveguide device for reverse transmission and low loss according to claim 1, wherein: The first branch waveguide and the second branch waveguide are bent in a cosine curve.

5. The Y-branch optical waveguide device for reverse transmission and low loss according to claim 1, wherein: The line width of the first branch waveguide is two thirds of the line width of the input waveguide.

6. The Y-branch optical waveguide device for reverse transmission and low loss according to claim 1, wherein: The first output waveguide includes a first transition portion and a first output portion; the first transition portion connects the first branch waveguide and the second output portion; The second output waveguide includes a second transition portion and a second output portion; the second transition portion connects the second branch waveguide and the second output portion.

7. The Y-branch optical waveguide device for reverse transmission and low loss according to claim 6, wherein: The line width of one end of the first transition portion connected to the first branch waveguide is equal to the line width of the first branch waveguide, and the line width of one end of the first transition portion connected to the first output portion is equal to the line width of the first output portion; The line width of one end of the second transition portion connected to the second branch waveguide is equal to the line width of the second branch waveguide, and the line width of one end of the second transition portion connected to the second output portion is equal to the line width of the second output portion.

8. The Y-branch optical waveguide device for reverse transmission and low loss according to claim 7, wherein: The line width of the first branch waveguide is two-thirds of the line width of the first output portion, and the line width of the first transition portion gradually increases from the first branch waveguide to the first output portion; The line width of the second branch waveguide is two-thirds of the line width of the second output portion, and the line width of the second transition portion gradually increases from the second branch waveguide to the second output portion.

9. The Y-branch optical waveguide device for reverse transmission and low loss according to claim 1, wherein: The material of the waveguide structure is lithium niobate.

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