CN114047578A - Waveguide layer and cross waveguide - Google Patents

Abstract

The application belongs to the technical field of optical waveguides, and discloses a waveguide layer and a cross waveguide; the waveguide layer comprises two waveguides which are vertically crossed, the shapes and the sizes of the two waveguides are the same, and the central points of the two waveguides are overlapped; the waveguide is in a biaxial symmetric structure, the symmetric axes of the waveguide comprise a first symmetric axis passing through the central point along the length direction and a second symmetric axis passing through the central point along the width direction, and the first symmetric axis is vertical to the second symmetric axis; the waveguide comprises a widened part and two equal-width parts respectively arranged at two ends of the widened part, the widths of any cross sections of the equal-width parts are the same, and a specific relation exists between the distance from the point of the side edge of the widened part to the second symmetry axis and the distance from the point of the side edge to the first symmetry axis; the crossing waveguide comprises the waveguide layer; the waveguide layer and the crossed waveguide can effectively reduce transmission loss and crosstalk in 1310nm optical communication bands.

Description

A waveguide layer and cross waveguide

technical field

The present application relates to the technical field of optical waveguides, and in particular, to a waveguide layer and a crossed waveguide.

Background technique

When multiple optical devices are connected to each other, waveguide crossing often occurs. At this time, for the intersection of waveguides, it is necessary to use crossed waveguides to achieve the purpose of efficient propagation of light waves and low crosstalk between waveguides; if two widths remain unchanged If the optical waveguides are directly intersected, the optical transmission efficiency will be greatly lost due to diffraction at the intersection of the waveguides.

Since the intensity of the diffraction effect at the intersection of the waveguide is negatively correlated with the width of the two waveguides, most of the design of the crossed waveguide adopts a structure with a gradually increasing waveguide width. Problems such as large loss and large crosstalk.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide a waveguide layer and a crossed waveguide, which can effectively reduce transmission loss and crosstalk in the 1310 nm optical communication band.

In a first aspect, the present application provides a waveguide layer, comprising two waveguides that intersect vertically, the shape and size of the two waveguides are the same, and the center points of the two waveguides are coincident; the waveguides have a biaxially symmetric structure , its symmetry axis includes a first symmetry axis passing through the center point along the length direction and a second symmetry axis passing through the center point along the width direction, and the first symmetry axis is perpendicular to the second symmetry axis;

The waveguide includes a widened portion and two equal-width portions respectively disposed at both ends of the widened portion, the widths of the equal-width portions on any cross section are the same, and the side edges of the widened portion reach the There is the following relationship between the distance of the second axis of symmetry and the distance from the side edge point to the first axis of symmetry:

；

;

为所述变宽部的侧边沿点到所述第二对称轴的距离，

为所述变宽部的侧边沿点到所述第一对称轴的距离，

为所述变宽部的半长，

为所述等宽部的半宽，

为所述变宽部的中心半宽。in,

is the distance from the side edge point of the widened portion to the second axis of symmetry,

is the distance from the side edge point of the widened portion to the first axis of symmetry,

is the half length of the widened portion,

is the half-width of the equal-width portion,

is the central half-width of the widened portion.

The two waveguides of the waveguide layer both include a widening portion, and the design of the gradual change in the width of the widening portion is reasonable, so that the light waves can be gathered at the intersections of the waveguides, thereby effectively eliminating the diffraction effect of the light waves at the intersections of the waveguides and reducing the It has less transmission loss and less crosstalk in the 1310nm optical communication band.

Preferably, the center half-width of the widened portion is 0.75 μm, and the half-length of the widened portion is 3.5 μm.

Therefore, the structure of the waveguide layer is relatively compact, and when it is applied to a cross-wave guide, the volume of the cross-wave guide can be reduced, and the miniaturized design of the optoelectronic integrated circuit can be realized.

Preferably, the thickness of the waveguide is 0.22 μm, and the width of the equal width portion is 0.45 μm.

Therefore, the requirements of the general standard for the interface of the cross waveguide can be met.

Preferably, a cross section of the waveguide perpendicular to the first axis of symmetry is rectangular.

In a second aspect, the present application provides a crossed waveguide, which includes a substrate, and further includes the aforementioned waveguide layer, where the waveguide layer is disposed on the upper surface of the substrate.

The two waveguides of the waveguide layer of the cross-waveguide both include a widening portion, and the design of the gradual change of the width of the widening portion is reasonable, so that the light waves can be gathered at the intersection of the waveguides, thereby effectively eliminating the diffraction of the light waves at the intersection of the waveguides. effect, reduce the transmission loss, and have less transmission loss and less crosstalk in the 1310nm optical communication band.

Preferably, the refractive index of the substrate is lower than the refractive index of the waveguide layer, and the refractive index of the waveguide layer is higher than the refractive index of air.

Preferably, the refractive index of the waveguide layer is 3.45, and the refractive index of the substrate is 1.45.

Preferably, the substrate is made of silicon dioxide and the waveguide layer is made of silicon.

Preferably, the upper surface of the waveguide layer is provided with a cladding layer, and the refractive index of the cladding layer is lower than that of the waveguide layer.

Preferably, the cladding is made of silica.

Beneficial effects:

In the waveguide layer and the crossed waveguide provided by the present application, the two waveguides of the waveguide layer both include a widening portion, and the width of the widening portion is designed reasonably in a gradual manner, so that the light waves can be gathered at the intersection of the waveguides, thereby effectively eliminating the The diffraction effect of the light wave at the intersection of the waveguide reduces the transmission loss, and has less transmission loss and less crosstalk in the 1310nm optical communication band.

Other features and advantages of the present application will be set forth in the description that follows, and, in part, will be apparent from the description, or learned by practice of the present application.

Description of drawings

FIG. 1 is a schematic structural diagram of a waveguide layer provided by an embodiment of the present application.

FIG. 2 is a schematic structural diagram of a waveguide of a waveguide layer provided in an embodiment of the present application.

FIG. 3 is a schematic structural diagram of a crossed waveguide provided by an embodiment of the present application.

FIG. 4 is a simulation calculation result of the crosstalk situation of the crossed waveguide provided by the embodiment of the present application.

FIG. 5 is a simulation calculation result of the optical transmission efficiency of the crossed waveguide provided by the embodiment of the present application.

FIG. 6 changes the optical transmission efficiency of the crossed waveguide according to the embodiment of the present application with the wavelength of the optical communication wave.

Numeral description: 1. waveguide; 101, widened portion; 102, equal width portion; 2, first axis of symmetry; 3, second axis of symmetry; 100, waveguide layer; 200, substrate.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Thus, the following detailed description of the embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the application as claimed, but is merely representative of selected embodiments of the application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures. Meanwhile, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

For convenience of description, the width direction in this application is the left-right direction in FIG. 2 , the length direction is the up-down direction in FIG. 2 , and the thickness direction is the direction perpendicular to the paper surface of FIG. 2 .

Please refer to FIGS. 1-2 . FIG. 1 is a waveguide layer 100 in some embodiments of the present application, including two waveguides 1 that intersect vertically. The shapes and sizes of the two waveguides 1 are the same, and the center point of the two waveguides 1 is the same O coincides; the waveguide 1 is a biaxially symmetric structure, and its axis of symmetry includes a first axis of symmetry 2 passing through the center point O along the length direction and a second axis of symmetry 3 passing through the center point O along the width direction (that is, the waveguide 1 is both about the first axis of symmetry The symmetry axis 2 is symmetrical, and is also symmetrical about the second symmetry axis 3), and the first symmetry axis 2 is perpendicular to the second symmetry axis 3 (thus, the two waveguides 1 are arranged in a 90° rotational symmetry);

As shown in FIG. 2, along the length direction, the waveguide 1 includes a widened portion 101 and two equal-width portions 102 respectively disposed at both ends of the widened portion 101. Any cross-section of the equal-width portion 102 (perpendicular to the first symmetry axis) 2) are the same width, and the following relationship exists between the distance from the side edge point of the widened portion 101 to the second axis of symmetry 3 and the distance from the side edge point to the first axis of symmetry 2 (the side edge point refers to the Except for the points on the edges other than the end connected to the equal-width portion 102, this relationship exists for any side edge point):

；

;

为变宽部101的侧边沿点到第二对称轴3的距离，

为变宽部101的侧边沿点到第一对称轴2的距离，

为变宽部101的半长（即变宽部101的长度的一半），

为等宽部102的半宽（即等宽部102的宽度的一半，也等于变宽部101的端部的半宽），

为变宽部101的中心半宽（即第二对称轴3处的变宽部101的横截面宽度的一半）。in,

is the distance from the side edge point of the widened portion 101 to the second symmetry axis 3,

is the distance from the side edge point of the widened portion 101 to the first symmetry axis 2,

is the half length of the widened portion 101 (that is, half of the length of the widened portion 101 ),

is the half-width of the equal-width portion 102 (that is, half the width of the equal-width portion 102 is also equal to the half-width of the end of the widened portion 101 ),

is the central half width of the widened portion 101 (ie, half of the cross-sectional width of the widened portion 101 at the second axis of symmetry 3).

It should be noted that the above description of the structure of the waveguide 1 is for the description of the structure of any cross-section of the waveguide 1 in the thickness direction.

The two waveguides 1 of the waveguide layer 100 both include a widening portion 101 , and the design of the gradual change in the width of the widening portion 101 is reasonable, so that the light waves can be gathered at the intersection of the waveguides 1 , thereby effectively eliminating the light waves at the intersection of the waveguides 1 . The diffraction effect at the 1310nm optical communication band reduces the transmission loss and has less transmission loss and less crosstalk.

和中心半宽

可根据实际需要设置。Among them, the half length of the widened portion 101

and center half width

Can be set according to actual needs.

为0.75μm，变宽部101的半长

为3.5μm。从而该波导层100的结构比较紧凑，其应用于交叉波导时，有利于降低交叉波导的体积，有利于实现光电集成电路的微型化设计。In some preferred embodiments, the central half-width of the widened portion 101

is 0.75 μm, the half length of the widened portion 101

is 3.5 μm. Therefore, the structure of the waveguide layer 100 is relatively compact, and when it is applied to a cross-wave guide, the volume of the cross-wave guide is reduced, and the miniaturization design of an optoelectronic integrated circuit is realized.

The thickness of the waveguide 1 and the width of the equal-width portion 102 can be set according to actual needs.

In some preferred embodiments, the thickness of the waveguide 1 is 0.22 μm (that is, the thicknesses of the widening portion 101 and the equal-width portion 102 are both 0.22 μm), and the width of the equal-width portion 102 is 0.45 μm. For the input/output interface of the waveguide layer of a general cross-waveguide, its standard size is 0.45 μm×0.22 μm, so that the waveguide layer 100 can meet the requirements of the general standard of the interface of the cross-waveguide, which is beneficial to ensure the application of the intersection of the waveguide layer 100 . The scope of application of the waveguide is large.

Preferably, the cross section of the waveguide 1 perpendicular to the first symmetry axis 2 (ie the cross section parallel to the second symmetry axis 3 ) is rectangular.

In this embodiment, the waveguide layer 100 is made of silicon.

为3.5μm，则等宽部102的长度=（8μm-2×3.5μm）/2=0.5μm。The length of the equal width portion 102 can be set according to actual needs, for example, it can be set according to the actual size of the cross waveguide using the waveguide layer 100; if the size of the cross waveguide using the waveguide layer 100 is 8 μm×8 μm, the widened portion 101's half length

If it is 3.5 μm, the length of the constant width portion 102=(8 μm−2×3.5 μm)/2=0.5 μm.

Referring to FIG. 3 , the present application provides a crossed waveguide, which includes a substrate 200 and the above-mentioned waveguide layer 100 . The waveguide layer 100 is disposed on the upper surface of the substrate 200 .

The two waveguides 1 of the waveguide layer 100 of the cross-waveguide both include a widening portion 101 , and the width of the widening portion 101 is designed in a reasonable gradient manner, so that the light waves can be gathered at the intersection of the waveguides 1 , thereby effectively eliminating the light waves in the waveguides. 1 The diffraction effect at the intersection reduces the transmission loss, and has less transmission loss and less crosstalk in the 1310nm optical communication band.

In some embodiments, the refractive index of the substrate 200 is lower than the refractive index of the waveguide layer 100 , and the refractive index of the waveguide layer 100 is higher than the refractive index of air. Since the refractive index of the waveguide layer 100 is higher than that of the substrate 200 and air, light waves can be totally reflected at the upper and lower surfaces when propagating in the waveguide layer 100 , avoiding energy loss caused by the light waves being transmitted from the upper and lower surfaces. In addition, it can be used normally without providing a cladding layer on the upper surface of the waveguide layer 100. In this case, it is equivalent to using air as the cladding layer.

Preferably, the refractive index of the waveguide layer 100 is 3.45, and the refractive index of the substrate 200 is 1.45, so that the refractive index deviation between the waveguide layer 100 and the substrate 200 is large enough to effectively prevent light waves from being transmitted from the lower surface and causing energy loss.

In some embodiments, the substrate 200 is made of silicon dioxide (but is not limited thereto) and the waveguide layer 100 is made of silicon.

In some preferred embodiments, the upper surface of the waveguide layer 100 is provided with a cladding layer (not shown in the figure), and the refractive index of the cladding layer is lower than that of the waveguide layer 100 . Since the refractive index of the cladding layer is lower than the refractive index of the waveguide layer 100 , total reflection of the light wave at the upper surface of the waveguide layer 100 can be achieved, avoiding energy loss caused by the light wave being transmitted from the upper surface. For example, when the refractive index of the waveguide layer 100 is 3.45, the refractive index of the cladding layer is 1.45 (but not limited to), so that the refractive index deviation between the waveguide layer 100 and the cladding layer is large enough to effectively prevent the light wave from Transmission from the top surface results in energy loss.

In this embodiment, the cladding layer is made of silica, but is not limited thereto (for example, it may also be a polymer or other material).

In some embodiments, the crossed waveguide is a compact crossed waveguide of the order of 8 μm×8 μm, so that the size of the substrate 200 is 8 μm×8 μm, the total length of the waveguide 1 is 8 μm, and the two end faces of the waveguide 1 (ie, equal widths) portion 102 ) is flush with the side of the substrate 200 .

In a specific embodiment, the thickness of the waveguide layer 100 is 0.22 μm, the width of the equal width portion 102 of the waveguide 1 is 0.45 μm, the central half width of the widened portion 101 is 0.75 μm, and the half length of the widened portion 101 is 3.5 μm, the refractive index of the waveguide layer 100 is 3.45, the refractive index of the substrate 200 is 1.45, and the refractive index of the cladding layer is 1.45. For this crossed waveguide, the crosstalk and transmission efficiency are calculated using the Gaussian light wave with TE (transverse electric field) polarization by the finite-difference time domain method. Figure 4 shows the crosstalk for the optical communication band of 1310 nm, and Figure 5 shows The variation of optical transmission efficiency with time for the optical communication band of 1310 nm (the two curves in the figure are the curves of the optical transmission efficiency of the two waveguides 1 with time), Figure 6 shows the variation of optical transmission efficiency with optical communication The change of wave wavelength; it can be seen from Figure 4 that the light wave has a relatively obvious convergence effect at the intersection point. For the optical communication band of 1310nm, the crosstalk is small, and the crosstalk can reach -30dBb; it can be seen from Figure 5 , for the optical communication band of 1310nm, the transmission efficiency can reach 97%, that is, the insertion loss of about -0.1dB; it can be seen from Figure 6 that the transmission efficiency of the crossed waveguide in the range of 1250nm to 1600nm is greater than 95%, even It shows a transmission efficiency of over 98.5% in the band around 1400 nm. It can be seen that the crossed waveguide has excellent robustness.

The above descriptions are merely examples of the present application, and are not intended to limit the protection scope of the present application. For those skilled in the art, various modifications and changes may be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims (10)

1. A waveguide layer comprises two waveguides (1) which are vertically intersected, the shapes and the sizes of the two waveguides (1) are the same, and the central points of the two waveguides (1) are overlapped; the waveguide (1) is of a biaxial symmetrical structure, the symmetry axes of the waveguide comprise a first symmetry axis (2) passing through the central point along the length direction and a second symmetry axis (3) passing through the central point along the width direction, and the first symmetry axis (2) is perpendicular to the second symmetry axis (3); it is characterized in that the preparation method is characterized in that,

the waveguide (1) comprises a widened part (101) and two equal-width parts (102) which are respectively arranged at two ends of the widened part (101), the widths of the equal-width parts (102) on any cross section are the same, and the following relation exists between the distance from the side edge point of the widened part (101) to the second symmetry axis (3) and the distance from the side edge point to the first symmetry axis (2):

；

wherein,

the distance of the side edge of the widened portion (101) from the second axis of symmetry (3) along a point,

is the distance of the side edge of the widening (101) from the first axis of symmetry (2) along a point,

is changed as describedThe half length of the wide portion (101),

is half the width of the equal width part (102),

is the central half width of the widening (101).

2. The waveguide layer according to claim 1, characterized in that the central half width of the widening (101) is 0.75 μm and the half length of the widening (101) is 3.5 μm.

3. The waveguide layer according to claim 2, characterized in that the thickness of the waveguide (1) is 0.22 μm and the width of the equal-width portion (102) is 0.45 μm.

4. The waveguide layer according to claim 1, characterized in that the cross section of the waveguide (1) perpendicular to the first axis of symmetry (2) is rectangular.

5. An intersecting waveguide comprising a substrate (200), further comprising a waveguide layer (100) according to any of claims 1-4, said waveguide layer (100) being arranged on an upper surface of said substrate (200).

6. The crossed waveguide according to claim 5, characterized in that the refractive index of the substrate (200) is lower than the refractive index of the waveguide layer (100), the refractive index of the waveguide layer (100) being higher than the refractive index of air.

7. The crossed waveguide according to claim 6, characterized in that the refractive index of the waveguide layer (100) is 3.45 and the refractive index of the substrate (200) is 1.45.

8. The crossed waveguide according to claim 5, characterized in that the substrate (200) is made of silicon dioxide and the waveguide layer (100) is made of silicon.

9. The crossing waveguide according to claim 5, characterized in that the upper surface of the waveguide layer (100) is provided with a cladding layer having a refractive index lower than the refractive index of the waveguide layer (100).

10. The crossed waveguide of claim 9, wherein the cladding is made of silica.

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