WO2016169054A1

WO2016169054A1 - Waveguide structure and silicon-based chip

Info

Publication number: WO2016169054A1
Application number: PCT/CN2015/077406
Authority: WO
Inventors: 魏玉明
Original assignee: 华为技术有限公司
Priority date: 2015-04-24
Filing date: 2015-04-24
Publication date: 2016-10-27
Also published as: CN107407775A

Abstract

A waveguide structure and a silicon-based chip containing the waveguide structure. The waveguide structure comprises a multi-mode interference optical waveguide (20) and an input/output channel (10) provided at two sides of the multi-mode interference optical waveguide (20), wherein the multi-mode interference optical waveguide (20) is provided with a waveguide channel (30) used for dissipating reflected light generated in the multi-mode interference optical waveguide (20), and the waveguide channel (30) may slowly dissipate light which would be reflected back originally, so as to reduce light rays reflected back to the input channel (10), thereby reducing the reflectivity of the waveguide structure. The waveguide structure avoids the cases where the quality of an output light signal decreases, a crosstalk increases, and a device connected in front of a multi-mode interference structure is damaged.

Description

Waveguide structure and silicon-based chip

Technical field

The present invention relates to the technical field of optical chips, and more particularly to a waveguide structure and a silicon-based chip.

Background technique

As a mainstream technology in all-optical signal processing, silicon-based photoelectrons uniformly fabricate devices such as lasers, modulators, detectors, and optical switches onto silicon-on-insulator (SOI) materials, which are silicon-based chips. Among the various devices that make up silicon-based chips, the multimode interference structure (Fig. 1) is widely used. It can be used as a beam splitter, a combiner or other devices to form optical switches, modulators, optical terminals, etc. .

As shown in Fig. 1, a classical 2×2 multimode interference structure consists of an input/output channel 1 and a multimode interference optical waveguide 2, the principle of which is to excite many modes by light excitation in the multimode interference portion. The light field distribution allowed by the waveguide) creates an interference phenomenon that eventually forms an image of the input light at a particular location. For multimode interference structures, the most important performance parameters are loss and back reflection characteristics.

The danger of back reflection is that, as shown in Figure 2, the reflected light entering the output channel will interfere with the output light we want, thus reducing the output light quality; returning the reflected light back to the input waveguide will harm the previously connected devices. If excessive reflection will directly reimburse the laser; reflected light entering other ports will form crosstalk, which is also undesirable. Especially when cascading multiple multimode interference structures, such as optical switch matrices, reflected light will always exist and propagate in the optical path, which is very detrimental to the performance of the system. Therefore, it is very important to reduce the reflection of multimode interference structures.

Summary of the invention

The invention provides a waveguide structure and a silicon-based chip for reducing light loss and improving the adverse effects of reflected light on the device.

In a first aspect, a waveguide structure is provided, the waveguide structure comprising a multimode interference optical waveguide and an input/output channel disposed on both sides of the multimode interference optical waveguide, wherein the multimode interference optical waveguide is provided with useful A waveguide channel that dissipates reflected light generated in the multimode interference optical waveguide.

In conjunction with the first aspect described above, in a first possible implementation, each of the waveguide channels has a structure in which the width gradually decreases in an outward direction of the multimode interference optical waveguide.

With reference to the first possible implementation manner of the foregoing first aspect, in a second possible implementation manner, a minimum value of a width of an end of the waveguide channel away from the multimode interference optical waveguide is smaller than the multimode interference light The single mode width of the waveguide at a specified wavelength.

With reference to the first possible implementation manner of the foregoing first aspect, in a third possible implementation manner, the length of the waveguide channel meets a set length, where the set length is greater than a width of the waveguide channel The width of the waveguide channel connected to the multimode interference optical waveguide is converted to a single mode width while satisfying the minimum length required without introducing a loss condition.

In conjunction with the first possible implementation of the first aspect, in a fourth possible implementation, the sidewall of the waveguide channel has a concave arc shape.

The first possible aspect of the first aspect, the first possible implementation of the first aspect, the second possible implementation of the first aspect, the third possible implementation of the first aspect, and the fourth possible aspect of the first aspect In a fifth possible implementation manner, the number of input/output channels located on the same side of the multimode interference optical waveguide is multiple, and at least one side of the plurality of interference partial optical waveguides, At least one of the waveguide channels is disposed between adjacent input/output channels.

In conjunction with the fifth possible implementation of the foregoing first aspect, in a sixth possible implementation, the waveguide channels are symmetrically disposed on opposite sides of the multimode interference optical waveguide.

The first possible aspect of the first aspect, the first possible implementation of the first aspect, the second possible implementation of the first aspect, the third possible implementation of the first aspect, and the fourth possible aspect of the first aspect The implementation of the first aspect, the fifth possible implementation of the first aspect, and the sixth possible implementation of the first aspect. In the seventh possible implementation, each of the input/output channels passes through the transition part of the optical waveguide The multimode interference optical waveguide is connected, wherein the transition portion of the optical waveguide has a gradually increasing width, and a narrower end is connected to the input/output channel, and a wider end is interfering with the multimode Optical waveguide connection.

In conjunction with the seventh possible implementation of the foregoing first aspect, in an eighth possible implementation, the sidewall of the transition portion optical waveguide is an arcuate sidewall having a gradually changing slope and no abrupt change.

In conjunction with the seventh possible implementation of the foregoing first aspect, in a ninth possible implementation, the sidewall of the transition portion optical waveguide is connected to the input/output channel and the multimode interference optical waveguide The slope of the joint is the same.

In a second aspect, there is provided a silicon-based chip comprising the waveguide structure of any of the above.

According to the waveguide structure provided by the first aspect, the silicon-based chip provided by the second aspect, the present invention provides a waveguide channel on the multimode interference optical waveguide, which can slowly dissipate the light originally to be reflected back. The light reflected back into the input channel is reduced, the reflectivity of the waveguide structure is reduced, thereby avoiding the significant influence of the reflected light on the performance of the device, and the quality of the output optical signal is degraded, the crosstalk is enhanced, and the multimode interference structure is connected in front of the structure. The case of the device.

DRAWINGS

1 is a perspective view of a waveguide structure in the prior art;

2 is a schematic view showing a state of reflected light in a waveguide structure in the prior art;

3 is a schematic structural diagram of a waveguide structure according to an embodiment of the present invention;

4 is a schematic diagram of a waveguide channel according to an embodiment of the present invention;

FIG. 5 is another schematic structural diagram of an optical waveguide structure according to an embodiment of the present invention; FIG.

FIG. 6 is another schematic structural diagram of an optical waveguide structure according to an embodiment of the present invention; FIG.

FIG. 7 is another schematic structural diagram of an optical waveguide structure according to an embodiment of the present invention; FIG.

8 is a spectrum diagram of reflected light in an optical waveguide in the prior art;

FIG. 9 is a spectrum diagram of an optical waveguide structure according to an embodiment of the present invention.

Reference mark:

1-input/output channel 2-multimode interference optical waveguide 10-input/output channel

20-multimode interference optical waveguide 30-waveguide channel 40-transition partial optical waveguide

detailed description

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that this The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

As shown in FIG. 3, FIG. 5 and FIG. 6, FIG. 3, FIG. 5 and FIG. 6 are schematic diagrams showing the waveguide structures of different structures provided in this embodiment.

Embodiments of the present invention provide a waveguide structure including a multimode interference optical waveguide 20 and an input/output channel 10 disposed on both sides of the multimode interference optical waveguide 20, wherein the multimode interference optical waveguide 20 is connected for The waveguide channel 30 that dissipates the reflected light generated in the multimode interference optical waveguide is dissipated.

In the above embodiment, the input/output channel 10 can be used both as a waveguide for light input and as a waveguide for light output. In specific use, it can only have one function, and the input is located on both sides of the multimode interference portion waveguide. / Output channel 10, when the input/output channel 10 on one side is used as an input channel, and the input/output channel 10 on the other side is used as an output channel. In this embodiment, by providing a waveguide channel 30 on the multimode interference optical waveguide 20, the waveguide channel 30 can slowly dissipate the light originally to be reflected back, reduce the light reflected back into the input channel, and reduce the waveguide. The reflectivity of the structure avoids the following drawbacks in the prior art: reflected light has a significant effect on the performance of the device, which causes a decrease in the quality of the output optical signal, an increase in crosstalk, and also jeopardizes the connection of the front of the multimode interference structure. Device. Especially when cascading multiple multimode interference structures, such as optical switch matrices, reflected light will always exist and propagate in the optical path, which adversely affects system performance.

As shown in FIG. 4, FIG. 4 shows the wear and tear of light in the optical waveguide. Specifically, the light is transmitted in the waveguide, and from the perspective of the ray, the reflection is continuously performed at the two interfaces of the waveguide. And refraction, when the refractive index distribution of the optical waveguide satisfies n1>n2, n1>n3

At the interface 1 and interface 2, total reflection may occur, that is, the refraction angle θ3 is equal to 90°, where n1 is the refractive index of the waveguide channel, and n2 and n3 are the refractive indices of the medium on both sides of the waveguide channel. When the width of the optical waveguide gradually becomes smaller, the incident angle θ1 also becomes smaller so that the total reflection condition is no longer satisfied, and the light leaks outward through the interface one and the interface two, thereby consuming the light.

In order to facilitate the understanding of the present embodiment, the waveguide structure provided by the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 3, first, the input/output channels on both sides of the multimode interference optical waveguide 20 in the light guiding structure 10 is symmetrically disposed, and the number of input/output channels 10 on the same side of the multimode interference optical waveguide 20 on one side is plural, and on at least one side of the plurality of interference portion optical waveguides, adjacent inputs/ A waveguide channel 30 is disposed between the output channels 10. Wherein, the input/output channel 10 on the same side is an input channel, and the input/output channel 10 on the other side is an output channel. And the number of the waveguide channels 30 is set corresponding to the input/output channel 10 as described above.

In the arrangement of the waveguide channel 30, the waveguide channel 30 may be disposed on both sides of the multimode interference optical waveguide 20, or the waveguide channel 30 may be disposed on one side of the multimode interference optical waveguide 20, as shown in FIG. As shown in FIG. 6 and FIG. 7, when the waveguide channel 30 is disposed on both sides, the symmetry of the waveguide channel 30 is disposed on both sides of the multimode interference optical waveguide 20. At this time, the input/output channel 10 can be based on actual conditions. As an output channel or an input channel, and a waveguide channel is provided on both sides, a waveguide channel (shown in FIG. 6) may be disposed between the two adjacent input/output channels 10 on the same side, or may be set. Multiple waveguide channels (shown in Figure 7), the specific settings are as needed. As shown in FIG. 3, when the optical waveguide channel 30 is disposed on one side, the optical waveguide channel 30 is disposed on one side of the output channel. The specific settings can be determined according to actual needs.

For the waveguide channel 30, it is used to reflect the light incident from the incident channel onto the multimode interference optical waveguide 20 to prevent the light from being reflected back to the input channel. In a specific arrangement, each waveguide channel 30 has a structure in which the width of the waveguide channel 30 gradually decreases in the outward direction of the multimode interference optical waveguide. That is, the waveguide channel 30 is a structure in which one end is wide and one end is narrow, wherein the wide end is in communication with the multimode interference optical waveguide 20, so that more light can enter the optical waveguide channel 30, and the end is wider and narrower at one end. The structure increases the incident angle of the light, making it easier for the light to be dissipated within the waveguide channel 30, thereby reducing the reflection of light back into the input channel.

In a specific arrangement, as shown in FIG. 3, FIG. 6, and FIG. 7, the sidewall of the waveguide channel 30 may adopt a linear sidewall. At this time, the waveguide channel 30 has a trapezoidal structure, so that the light can be better in the waveguide channel. 30 internal wear and tear. As a preferred solution, the trapezoidal structure is an isosceles trapezoidal structure, so that light energy is depleted in the waveguide channel 30 when applied to a plurality of input channels.

In addition to the above-described isosceles trapezoid, the waveguide channel 30 adopts another preferred embodiment, that is, the sidewall of the waveguide channel 30 has a concave arc shape. As shown in Figure 5, when the waveguide channel is concave, It can be seen that compared with the waveguide channel of the straight side wall, there is obviously a smaller incident angle at the same length, so that the optical power originally to be reflected can be leaked out of the optical waveguide faster than the straight type. Thereby reducing the interference caused by the reflected light on the device.

In a specific arrangement, in order to reduce the light loss, it is preferable that the minimum value of the width of one end of the waveguide channel 30 away from the multimode interference optical waveguide 20 is smaller than the single mode width of the multimode interference optical waveguide 20 at a specified wavelength. The single mode width: the optical waveguide determined by the refractive index distribution on one section, we can find the spatial distribution of the electric field/magnetic field strength by discretizing the Maxwell's equations (the classical formula that all electromagnetic fields must satisfy). The situation, a distribution that is calculated in this way, is the solution of Maxwell's equations, which we call a pattern. The mode with the lowest order is called the fundamental mode. If there is a width/height size for the optical waveguide, so that the solution of Maxwell's equations has one and only one fundamental mode, we say that the optical waveguide satisfies the single mode condition (there is already an approximation Calculated formula). When the height is fixed, the minimum width that satisfies the single mode condition is the single mode width. At the same time, the single mode width is wavelength dependent. Since optical devices typically operate over a range of wavelengths, we choose a single mode width at the center wavelength. The specified wavelengths are common wavelengths such as 1550 nm and 1310 nm.

In addition, the length of the waveguide channel 30 also satisfies the set length, and the set length is greater than the width of the waveguide channel 30 from the width of the waveguide channel 30 connected to the multimode interference optical waveguide 20 to the single mode width, while satisfying the loss of introduction. Condition, the minimum length required. The lossless length is: the mode described in the single mode width, which are the solutions of Maxwell's equations, so they can propagate without loss in the optical waveguide, but when the refractive index distribution occurs in the transmission direction of the optical waveguide Studies have shown that only when the length of this mutation is very small can it be considered lossless. In practical applications, we often want to make some changes in the width of the waveguide. Then we can achieve a lossless width transition by cascading a number of segments (or smoothing into a curve) without loss. The shortest length required is called lossless length.

In order to further reduce wear and reflection, as a preferred embodiment, each input/output channel 10 is connected to the multimode interference optical waveguide 20 through a transition portion optical waveguide 40, wherein the transition portion of the optical waveguide 40 is gradually increased in width. The structure has a narrower end connected to the input/output channel 10 and a wider end connected to the multimode interference optical waveguide. Specifically, that is, in the input/output channel 10 and more The portion where the mode interference optical waveguide 20 is connected is provided with a transition portion optical waveguide 40 which also has a structure in which one end is wide and one end is narrow, and the narrow end is connected to the input/output channel 10, and the wide end is multimode. The interference optical waveguide 20 is connected. When the transition portion of the optical waveguide 40 is used, when light is reflected to the input channel, the light is reflected back through the sidewall of the transition portion of the optical waveguide 40 to prevent light from entering the input channel. Specifically, Since the transition portion of the optical waveguide 40 has a structure in which one end is narrow at one end and the narrow end is in communication with the input/output channel 10, the side wall of the transitional optical waveguide is an inclined side wall, and when the reflected light illuminates the transition portion of the light When the sidewall of the waveguide 40 is used, the incident angle of the reflected light is smaller than the incident angle directly incident on the sidewall of the input channel, so that the light is more easily consumed in the transition portion of the optical waveguide 40, thereby reducing the reflection of the reflected light from the input channel, thereby Improves the adverse effects of reflected light on the device.

In the above embodiment, preferably, the sidewall of the transition portion optical waveguide 40 is a curved sidewall having a gradually changing slope and no abrupt change. And the curved sidewall is a curved sidewall protruding from the outside of the transitional optical waveguide, further reducing the incident angle of the reflected light. Further, the sidewall of the transition portion optical waveguide 40 has the same slope at the junction with the input/output channel 10 and the multimode interference optical waveguide 20. Thereby, the loss of light energy caused by the mutation occurring at the junction is avoided.

In order to more clearly understand the optical waveguide structure provided by this embodiment, the effects thereof will be described below with reference to FIG. 8 and FIG. 9. FIG. 8 is a 2×2 multimode interference structure in the prior art (shown in FIG. 2 Reflected light spectrum of the structure), FIG. 9 is a reflected light spectrum of the 2×2 multimode interference structure (the structure shown in FIG. 5) provided by the embodiment, wherein 1# represents the first input channel, and 2# represents The second input channel, as can be seen from the comparison of FIG. 8 and FIG. 9, the reflected light of the optical waveguide structure provided by this embodiment is significantly reduced. For a 2×2 multimode interference structure, the present invention is capable of reducing the reflection intensity by 10 dB; the corresponding cost to be paid is small, and the structure of the present invention has little effect on the insertion loss of the device, and does not increase the process difficulty or introduce additional Process steps; in addition, a wide range of uses: multimode interference structures are widely used in the field of optics.

Embodiments of the present invention also provide a silicon-based chip including the waveguide structure of any of the above.

In the above embodiment, by providing the waveguide channel 30 on the multimode interference optical waveguide 20, the wave The guiding channel can slowly dissipate the light originally to be reflected back, reduce the light reflected back into the input channel, and reduce the reflectivity of the waveguide structure, thereby avoiding the following defects in the prior art: the performance of the reflected light on the device The effect is significant, which causes the quality of the output optical signal to decrease, the crosstalk to increase, and the device connected to the front of the multimode interference structure. Especially when cascading multiple multimode interference structures, such as optical switch matrices, reflected light will always exist and propagate in the optical path, which adversely affects system performance.

It is apparent that those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and modifications of the invention

Claims

A waveguide structure comprising: a multimode interference optical waveguide and an input/output channel disposed on both sides of the multimode interference optical waveguide, wherein the multimode interference optical waveguide is provided for dissipating A waveguide channel that reflects light generated in a multimode interference optical waveguide.
The waveguide structure according to claim 1, wherein each of the waveguide channels has a structure in which a width gradually decreases in an outward direction of the multimode interference optical waveguide.
The waveguide structure according to claim 2, wherein a minimum value of a width of one end of said waveguide channel away from said multimode interference optical waveguide is smaller than a single mode width of said multimode interference optical waveguide at a specified wavelength.
The waveguide structure according to claim 2, wherein a length of said waveguide channel satisfies a set length, said set length being: greater than a width of said waveguide channel from said waveguide channel and a multimode interference optical waveguide The width of the connection is converted to a single mode width while satisfying the minimum length required to introduce no loss conditions.
The waveguide structure according to claim 2, wherein the side wall of the waveguide channel has a concave arc shape.
The waveguide structure according to any one of claims 1 to 5, wherein the number of input/output channels on the same side of the multimode interference optical waveguide is plural, and in the multimode interference optical waveguide At least one side is provided with at least one of the waveguide channels between adjacent input/output channels.
The waveguide structure according to claim 5, wherein said waveguide channels are disposed on both sides of said multimode interference optical waveguide.
The waveguide structure according to any one of claims 1 to 7, wherein each of the input/output channels is connected to the multimode interference optical waveguide through a transition portion optical waveguide, wherein the transition portion of the optical waveguide is gradually tapered The structure is enlarged, and a narrower end is connected to the input/output channel, and a wider end is connected to the multimode interference optical waveguide.
The waveguide structure according to claim 8, wherein the side wall of the transition portion optical waveguide is an arcuate side wall having a gradually varying slope and no abrupt change.
The waveguide structure according to claim 8, wherein a sidewall of said transition portion optical waveguide has the same slope at a junction with said input/output channel and said multimode interference optical waveguide.
A silicon-based chip comprising the waveguide structure according to any one of claims 1 to 10.