CN112817086B - Mach-Zehnder interferometer based on TM0 mode light and preparation method - Google Patents

Abstract

The invention provides a Mach-Zehnder interferometer based on TM0 mode light and a preparation method thereof. The structure includes: an input waveguide, a first mode converter, a connecting arm, a second mode converter and an output waveguide, wherein the second mode converter The structure of the converter is the same as that of the first mode converter, and has a double-layer pyramid structure. The invention realizes that no matter the input end inputs the incident light of TM0 mode or the input light of TE1 mode, the connecting arm includes a straight waveguide section, and its output end can output the outgoing light of TM0 mode and TE1 mode; it can effectively solve the Mach existing in the prior art. Zehnder interferometers are sensitive to temperature, complex in structure, and large in size: they can be compatible with CMOS technology and facilitate mass production.

Description

Mach-Zehnder interferometer based on TM0 mode light and preparation method

technical field

The invention belongs to the technical field of optics, in particular to a Mach-Zehnder interferometer based on TM0 mode light and a preparation method thereof.

Background technique

Mach Zehnder Interferometer (MZI) is an optical basic device and is widely used in modern optical fiber transmission systems. Due to the large thermo-optic coefficient of silicon-based materials, silicon-based Mach-Zehnder interferometers are generally sensitive to temperature. In order to solve this problem, existing Mach-Zehnder interferometers generally adopt a double-link structure. However, the methods in the prior art have problems such as complex structure and large size, especially the Mach-Zehnder interferometer based on TM0 mode light.

Therefore, it is necessary to effectively solve the problem that the Mach-Zehnder interferometer based on TM0 mode light is sensitive to temperature in the prior art.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a Mach-Zehnder interferometer, which is used to solve the problems of temperature-sensitive and structural problems of the Mach-Zehnder interferometer based on TMO mode light in the prior art. complex, large size, etc.

To achieve the above object and other related objects, the present invention provides a Mach-Zehnder interferometer based on TM0 mode light, the Mach-Zehnder interferometer comprising:

input waveguide;

a first mode converter connected to the input waveguide, the first mode converter having a double-layer tapered structure;

The second mode converter is located on one side of the first mode converter and has a space between the first mode converter and the second mode converter, the second mode converter and the first mode converter have the same structure and Symmetrical settings;

a connecting arm, located between the first mode converter and the second mode converter, one end is connected with the first mode converter, the other end is connected with the second mode converter, and the the connecting arm includes a straight waveguide segment;

An output waveguide is connected to the second mode converter to output mixed mode output light including TM0 mode light.

Optionally, the first mode converter includes: a first symmetrical transmission section, a second symmetrical transmission section and a third symmetrical transmission section connected in sequence, wherein the first symmetrical transmission section is connected to the input waveguide , the third symmetrical transmission section is connected with the connecting arm; the second mode converter includes: a fourth symmetrical transmission section, a fifth symmetrical transmission section and a sixth symmetrical transmission section connected in sequence, wherein the The fourth symmetrical transmission section is connected with the connecting arm, and the sixth symmetrical transmission section is connected with the output waveguide.

Optionally, the first symmetrical transmission section includes a first upper waveguide section and a first lower waveguide section located below and symmetrical about it, and the second symmetrical transmission section includes a second upper waveguide section and a first lower waveguide section located below and symmetrical about it. A second lower waveguide section symmetric about it; the fifth symmetric transmission section includes a fifth upper waveguide section and a fifth lower waveguide section located below and symmetric about it, the sixth symmetric transmission section includes a sixth upper waveguide segment and a sixth lower waveguide segment located below and symmetrical about it to form the double-layered tapered structure.

Optionally, the sum of the thicknesses of the first lower waveguide segment and the first upper waveguide segment, the sum of the thicknesses of the second lower waveguide segment and the second upper waveguide segment, and the third symmetrical transmission thickness of the fourth symmetrical transmission segment, the sum of the thicknesses of the fifth lower waveguide segment and the fifth upper waveguide segment, the sixth lower waveguide segment and the sixth upper waveguide segment The sum of the thicknesses is equal.

Optionally, the thicknesses of the first upper waveguide section and the first lower waveguide section are equal, and the thickness of the input waveguide is twice the thickness of the first upper waveguide section; the second upper waveguide section is the same as the thickness of the first upper waveguide section. The thicknesses of the second lower waveguide segment are equal; the thicknesses of the fifth upper waveguide segment and the fifth lower waveguide segment are equal; and the thicknesses of the sixth upper waveguide segment and the sixth lower waveguide segment are equal.

Optionally, the first lower waveguide section has a narrow end face and a wide end face, the first upper waveguide section has a narrow end face and a wide end face, and the narrow end face of the first lower waveguide section is connected to the first upper waveguide section. The widths of the narrow end faces of the first lower waveguide segment are equal to each other, and the wide end face of the first lower waveguide segment is larger than the respective preset distances on both sides of the wide end face of the first upper waveguide segment; the second lower waveguide segment has a narrow end face and a wide end face, so The second upper waveguide section has a narrow end face and a wide end face, and the width of the wide end face of the second lower waveguide section is equal to the width of the wide end face of the first lower waveguide section, and the narrow end face of the second upper waveguide section is the same as the width of the wide end face of the first lower waveguide section. The wide end faces of the first upper waveguide segment are connected and have the same width, the narrow end face of the second lower waveguide segment has the same width as the wide end face of the second upper waveguide segment; the fifth lower waveguide segment has a narrow end face and a wide end face, the fifth upper waveguide section has a narrow end face and a wide end face, and the width of the narrow end face of the fifth lower waveguide section is equal to the width of the wide end face of the fifth upper waveguide section; the sixth lower waveguide section has the same width. The segment has a narrow end face and a wide end face, the sixth upper waveguide segment has a narrow end face and a wide end face, and the narrow end face of the sixth lower waveguide segment has the same width as the narrow end face of the sixth upper waveguide segment and is equal to the width of the narrow end face of the sixth upper waveguide segment. The output waveguide is connected, the width of the wide end face of the sixth lower waveguide section is equal to the width of the wide end face of the fifth lower waveguide section, and the wide end face of the sixth lower waveguide section is larger than the wide end face of the sixth upper waveguide section the preset distances on both sides respectively.

Optionally, the width of the input waveguide is 0.40 μm-0.50 μm, the width of the narrow end face of the first upper waveguide is 0.40 μm-0.50 μm, and the width of the wide end face of the first upper waveguide segment is 0.50 μm -0.60 μm, the preset distance is 0.45 μm-0.55 μm, the width of the wide end face of the second upper waveguide is 0.57 μm-0.67 μm, and the width of the narrow end face of the third symmetrical transmission section is 0.40 μm-0.50 μm μm; the length of the first symmetrical transmission segment is 28 μm-29 μm, the length of the second symmetrical transmission segment is 24 μm-26 μm, and the length of the third symmetrical transmission segment is 5 μm-10 μm; The width of the straight waveguide segment is 0.40 μm-0.50 μm, the width of the wide end face of the fifth upper waveguide is 0.57 μm-0.67 μm, and the width of the narrow end face of the fifth upper waveguide is 0.40 μm-0.50 μm, so The width of the wide end face of the sixth upper waveguide section is 0.50 μm-0.60 μm, the width of the narrow end face of the fourth symmetrical transmission section is 0.40 μm-0.50 μm; the length of the fifth symmetrical transmission section is 24 μm-26 μm, The length of the fourth symmetrical transmission segment is 5 μm-10 μm.

Optionally, the Mach-Zehnder interferometer includes an SOI substrate, the SOI substrate includes a bottom silicon layer, a buried oxide layer and a top silicon layer, the first mode converter, the connecting arm and the first mode converter. Both mode converters are formed by etching the top silicon layer.

Optionally, the Mach-Zehnder interferometer further includes a protective layer, the protective layer is located on the upper surface of the buried oxide layer and completely covers the first mode converter, the connecting arm and the second Mode converter.

Optionally, the width of the straight waveguide section of the connecting arm is 569 nm.

Optionally, the incident light in the TM0 mode is input from the input waveguide section; in the first symmetrical transmission section, the effective refractive indices of TM0 and TE1 are equal, and the TM0 mode is converted into the TE1 mode; in the second symmetrical transmission section , and part of the TE1 mode light is converted back to the TM0 mode light to obtain the mixed mode light of TM0 and TE1.

In addition, the present invention also provides a preparation method of a Mach-Zehnder interferometer based on TMO mode light as described in any one of the above solutions, wherein the preparation method comprises the steps:

An SOI substrate is provided, the SOI substrate includes a bottom silicon layer, a buried oxide layer and a top silicon layer;

The top silicon layer is etched to form the first mode converter, the connecting arm and the second mode converter.

As mentioned above, the Mach-Zehnder interferometer based on TM0 mode light of the present invention and the preparation method thereof realize that no matter the input end inputs the incident light of the TM0 mode or the input light of the TE1 mode, the output end can output the TM0 mode and the TE1 mode. It can effectively solve the problems of the Mach-Zehnder interferometer existing in the prior art being relatively sensitive to temperature, complex in structure and large in size; it can be compatible with the CMOS process and facilitate mass production.

Description of drawings

1-2 are schematic top views of the structure of the Mach-Zehnder interferometer provided by the present invention; wherein, FIG. 1 is a schematic diagram of the overall structure, and FIG. 2 is a schematic diagram of a partial enlarged view.

3-7 are schematic cross-sectional views of the structure obtained by each step in the preparation of the Mach-Zehnder interferometer provided by the present invention.

FIG. 8 is a graph showing the width of the connecting arm in the Mach-Zehnder interferometer provided by the present invention and the change rate of the effective refractive index of the incident light in different modes with respect to the temperature.

FIG. 9 is a graph showing the wavelength of incident light and the input loss of the Mach-Zehnder interferometer provided by the present invention under two different temperature conditions of 26.85°C and 56.85°C.

10-14 are schematic diagrams showing the overall performance simulation results of the Mach-Zehnder interferometer device provided by the present invention, wherein, FIG. 10-13 is a graph of input loss under different input and output modes; FIG. 14 is a schematic diagram of the simulated mode field of the device .

FIG. 15 is a schematic diagram showing an output ratio of TM0 and TE1 of about 50:50 in an example of the Mach-Zehnder interferometer of the present invention.

Component label description

11 Input Waveguide

12 First Mode Converter

121 First symmetrical transmission segment

121a first upper waveguide section

121b First lower waveguide segment

122 Second symmetrical transmission segment

122a Second upper waveguide section

122b Second lower waveguide section

123 Third symmetrical transmission segment

13 connecting arm

14 Second Mode Converter

15 Output waveguide

201 Bottom silicon layer

202 Buried Oxygen Layer

203 Top silicon layer

204 Etch mask layer

205 Initial layer

206 Upper waveguide segment layer

207 Lower waveguide segment layer

208 protective layer

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

When describing the embodiments of the present invention in detail, for the convenience of explanation, the cross-sectional views showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the protection scope of the present invention. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in the actual production.

For convenience of description, spatially relative terms such as "below," "below," "below," "below," "above," "on," etc. may be used herein to describe an element shown in the figures or The relationship of a feature to other components or features. It will be understood that these spatially relative terms are intended to encompass other directions of the device in use or operation than those depicted in the figures. In addition, when a layer is referred to as being 'between' two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Additionally, "between" as used in the present invention includes both endpoints.

In the context of this application, descriptions of structures where a first feature is "on" a second feature can include embodiments in which the first and second features are formed in direct contact, and can also include further features formed over the first and second features. Embodiments between the second features such that the first and second features may not be in direct contact.

It should be noted that the diagrams provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, so the diagrams only show the components related to the present invention rather than the number, shape and the number of components in the actual implementation. For dimension drawing, the type, quantity and proportion of each component can be arbitrarily changed in actual implementation, and the component layout may also be more complicated.

As shown in FIG. 1 , the present invention provides a Mach-Zehnder interferometer based on TM0 mode light. The Mach-Zehnder interferometer includes: an input waveguide 11 , a first mode converter 12 , a connecting arm 13 , and a second mode converter 14 and output waveguide 15. Based on the design of the present invention, a temperature-insensitive Mach-Zehnder interferometer based on TM0 mode light can be obtained. Regardless of whether the input end receives the incident light in TM0 mode or the input light in TE1 mode, the output end can output the outgoing light in TM0 mode and TE1 mode; the two mode converters in the temperature-insensitive Mach-Zehnder interferometer are connected to each other through a connecting arm. Connection, simple structure, with less loss. At the same time, the interferometer of the present invention can be compatible with the CMOS process, which is convenient for mass production.

As shown in Figures 1 and 2, the input waveguide 11 may be a straight waveguide with the same width everywhere.

In addition, the interferometer of the present invention includes a first mode converter 12 and a second mode converter 14 . In an example, the two are identical double-layer cone structures, which are symmetrically arranged with respect to the middle connecting arm 13 in the structure of the interferometer. The double-layer tapered structure means that the converter structure consists of upper and lower material layers. The two material layers have different parts. After receiving the signal from the input waveguide, it continues to transmit to the connecting arm, and then passes through the converter with the same structure symmetrically arranged. output from the output waveguide.

In an example, the first mode converter 12 specifically includes: a first symmetric transmission section 121, a second symmetric transmission section 122 and a third symmetric transmission section 123 connected in sequence, one end of the first mode converter 12 (the first symmetric transmission section 123). A symmetrical transmission section 121) is connected to the input waveguide 11, and the other end (the third symmetrical transmission section 123) is connected to the connecting arm 13, as shown in FIG. 2 .

In addition, in an example, the second mode converter 14 specifically includes: a fourth symmetrical transmission section, a fifth symmetrical transmission section and a sixth symmetrical transmission section connected in sequence, one end of the second mode converter 14 (the sixth symmetrical transmission section) The symmetrical transmission section) is connected to the output waveguide 15, and the other end (the fourth symmetrical transmission section) is connected to the connecting arm 13, as shown in the structure shown in FIG. 1 .

It should be noted that the structure of the first mode converter 12 and the second mode converter 14 are identical in structure and symmetrically arranged means that the first symmetrical transmission section of the first mode converter and the sixth symmetrical transmission section of the second mode converter The segment structure is the same and the structure is symmetrically arranged, and the size and dimensions of the two are the same. Similarly, the second symmetrical transmission segment of the first mode converter and the fifth symmetrical transmission segment of the second mode converter have the same structure and are symmetrically arranged. The first mode The third symmetrical transmission section of the converter and the fourth symmetrical transmission section of the second mode converter have the same structure and are symmetrically arranged. It can be understood that the second mode converter is connected to the back of the connecting arm 13 in turn after rotating the first mode converter by 180°.

As shown in FIG. 2 and FIG. 6 , as an example, the first symmetrical transmission section 121 includes a first upper waveguide section 121a and a first lower waveguide section 121b located below and symmetrical therewith, and the second symmetrical transmission section 122 includes a second upper waveguide segment 122a and a second lower waveguide segment 122b located below and symmetrical therewith. It should be noted that the symmetry here is that the structure size of the lower waveguide is symmetrical with respect to both sides of the upper waveguide, and the size of the first upper waveguide segment 121a itself changes symmetrically, for example, in an isosceles trapezoid structure, and further, the first lower waveguide segment 121b The portion beyond the first upper waveguide segment 121a is symmetrically distributed on the upper and lower sides shown in the figure (actually the left and right sides in the extending direction of the first upper waveguide segment).

Similarly, referring to the second symmetric transmission section 122, the fifth symmetric transmission section includes a fifth upper waveguide section and a fifth lower waveguide section located below and symmetric about it; refer to the first symmetric transmission section 121, the The six-symmetric transmission segment includes a sixth upper waveguide segment and a sixth lower waveguide segment located below and symmetric about it.

Based on the above design, the first mode converter and the second mode converter obtained by the present invention actually include an upper and lower two-layer structure, forming a double-layer tapered structure, so as to adapt to the light of the TM0 mode, which corresponds to the light of the TM0 mode Design, since the effective refractive indices of TE0 mode and TM0 mode are very different, different structures must be designed to complete the transmission of different modes. In the double-sided tapered mode, since the cross-sectional symmetry of the structure is broken, in the double-layered tapered structure, it is beneficial to design the effective refractive index of the TM0 mode and the TE1 mode to be the same, and realize the conversion of the TM0 mode and the TE1 mode based on the design.

As an example, the upper and lower waveguide segments of each symmetrical transmission segment of the present invention are formed by etching based on the same material layer. Therefore, the sum of the thicknesses of the first lower waveguide segment 121b and the first upper waveguide segment 121a is the thickness of the material layer; the sum of the thicknesses of the second lower waveguide segment 122b and the second upper waveguide segment 122a and is the thickness of the material layer; the thickness of the third symmetrical transmission section 123 is the thickness of the material layer, so that the upper surfaces of the three are flush. Similarly, it can be understood that the thickness of the fourth symmetrical transmission segment, the sum of the thicknesses of the fifth lower waveguide segment and the fifth upper waveguide segment, the thickness of the sixth lower waveguide segment and the sixth The sum of the thicknesses of the upper waveguide segments is equal.

In an example, the thicknesses of the first upper waveguide section and the first lower waveguide section are equal. In addition, the thickness of the input waveguide is twice the thickness of the first upper waveguide, and the input waveguide 11 is also thick. It is formed by etching from the same material layer; for the same reason, it can be understood that the thicknesses of the second upper waveguide section and the second lower waveguide section are equal; the fifth upper waveguide section and the fifth lower waveguide section have the same thickness. The thicknesses of the sixth upper waveguide segment and the sixth lower waveguide segment are equal. In addition, the output waveguide 15 may also be formed by etching based on the same material layer, and has the same thickness as the input waveguide 11 .

In a specific example, the thickness of the input waveguide is 200-240 nm, which may be the above-mentioned value at both ends, or may be any value in between. 220nm is chosen as in this example. Optionally, the thickness of the first upper waveguide segment 121a is 100-120 nm, which is selected as 110 nm in this example, which is half of the thickness of the input waveguide. Meanwhile, the thickness corresponding to the first lower waveguide segment 121 may be 110 nm. Based on this, it can be understood that the thickness of the upper waveguide section of each symmetrical transmission section can have the same selection design as that of the first upper waveguide section, and the thickness of the lower waveguide section of each symmetrical transmission section can be the same as the thickness of the first lower waveguide section. There are the same selection designs. In addition, the third symmetrical transmission section and the fourth symmetrical transmission section are single-layer structures with the same thickness as the input waveguide.

As shown in FIG. 2 , as an example, the first lower waveguide section 121b has a narrow end face and a wide end face, the first upper waveguide section 121a has a narrow end face and a wide end face, and the first lower waveguide section 121b has a narrow end face and a wide end face. The width of the end face and the narrow end face of the first upper waveguide section 121a is equal, both W0; the wide end face of the first lower waveguide section is larger than the preset distance Ws on both sides of the wide end face of the first upper waveguide section. In one example, the width of the input waveguide 11 is also W0.

The second lower waveguide section 122b has a narrow end face and a wide end face, the second upper waveguide section 122a has a narrow end face and a wide end face, and the wide end face of the second lower waveguide section 122b is the same as the first lower waveguide section 121b. The width of the wide end face of the second upper waveguide segment 122a is equal to the width of the wide end face of the second upper waveguide segment 122a. The width is equal to the width of the wide end face of the second upper waveguide segment 122a, and both are W2.

The third symmetrical transmission section 123 has a narrow end face and a wide end face, and the wide end face of the third symmetrical transmission section is equal to the width W2 of the wide end face of the second upper waveguide section 122a. In addition, in an example, the connecting arm 13 is composed of only a straight waveguide section, including a multi-mode waveguide, the width of which is equal to the width W3 of the narrow end face of the third symmetrical transmission section 123 .

Similarly, it can be understood that the fifth symmetrical transmission segment has the same design as the second symmetrical transmission segment, the sixth symmetrical transmission segment has the same design as the first symmetrical transmission segment, and the fourth symmetrical transmission segment has the same design as the third symmetrical transmission segment. Design of the transmission segment. The fifth lower waveguide section has a narrow end face and a wide end face, the fifth upper waveguide section has a narrow end face and a wide end face, and the narrow end face of the fifth lower waveguide section and the wide end face of the fifth upper waveguide section The width of the sixth lower waveguide segment is equal to that of a narrow end face and a wide end face, the sixth upper waveguide segment has a narrow end face and a wide end face, and the narrow end face of the sixth lower waveguide segment is the same as the sixth upper waveguide segment. The width of the narrow end face of the segment is the same and is connected to the output waveguide, the width of the wide end face of the sixth lower waveguide segment is equal to the width of the wide end face of the fifth lower waveguide segment, and the wide end face of the sixth lower waveguide segment is larger The preset distances on both sides of the broad end face of the sixth upper waveguide segment are obtained.

As an example, the width W0 of the input waveguide is 0.40 μm-0.50 μm, the width W0 of the narrow end face of the first upper waveguide is 0.40 μm-0.50 μm, and the width W1 of the wide end face of the first upper waveguide segment is 0.50 μm-0.60 μm, the preset distance Ws is 0.45 μm-0.55 μm, the width W2 of the wide end face of the second upper waveguide is 0.57 μm-0.67 μm, and the width of the narrow end face of the third symmetrical transmission section W3 0.40μm-0.50μm. In addition, the length Ltp1 of the first symmetrical transmission segment 121 is 28 μm-29 μm, the length Ltp2 of the second symmetrical transmission segment 122 is 24 μm-26 μm, and the length Ltp3 of the third symmetrical transmission segment 123 is 5 μm-10 μm. In addition, the width W3 of the straight waveguide section of the connecting arm 13 is 0.40 μm-0.50 μm. Similarly, the width of the wide end face of the fifth upper waveguide is 0.57 μm-0.67 μm, the width of the narrow end face of the fifth upper waveguide is 0.50 μm-0.60 μm, and the width of the wide end face of the sixth upper waveguide segment is 0.57 μm-0.67 μm. The width is 0.50 μm-0.60 μm, the width of the narrow end face of the sixth upper waveguide segment is 0.40 μm-0.50 μm, and the width of the narrow end face of the fourth symmetrical transmission segment is 0.40 μm-0.50 μm. In addition, the length of the sixth symmetrical transmission segment is 28 μm-29 μm, the length of the fifth symmetrical transmission segment is 24 μm-26 μm, and the length of the fourth symmetrical transmission segment is 5 μm-10 μm.

In addition, it should be noted that the above-mentioned size parameters need to have a one-to-one correspondence within the above-mentioned range, which is beneficial to the realization of the mode conversion of the present invention. Several examples are described below. For example, in the first example, the width W0 of the input waveguide is 0.45 μm, the width W0 of the narrow end face of the first upper waveguide is 0.45 μm, and the first upper waveguide segment is 0.45 μm. The width W1 of the wide end face is 0.55 μm, the preset distance Ws is 0.5 μm, the width W2 of the wide end face of the second upper waveguide is 0.62 μm, and the narrow end face width W3 of the third symmetrical transmission section is 0.45 μm. In addition, the length Ltp1 of the first symmetrical transmission segment 121 is 28.5 μm, the length Ltp2 of the second symmetrical transmission segment 122 is 24 μm, and the length Ltp3 of the third symmetrical transmission segment 123 is 5 μm. In the second example, the width W0 of the input waveguide is 0.41 μm, the width W0 of the narrow end face of the first upper waveguide is 0.41 μm, and the width W1 of the wide end face of the first upper waveguide segment is 0.51 μm, The preset distance Ws is 0.46 μm, the width W2 of the wide end face of the second upper waveguide is 0.58 μm, and the width W3 of the narrow end face of the third symmetrical transmission section is 0.41 μm. In addition, the length Ltp1 of the first symmetrical transmission segment 121 is 28.1 μm, the length Ltp2 of the second symmetrical transmission segment 122 is 24.5 μm, and the length Ltp3 of the third symmetrical transmission segment 123 is 6 μm. In the third example, the width W0 of the input waveguide is 0.43 μm, the width W0 of the narrow end face of the first upper waveguide is 0.43 μm, and the width W1 of the wide end face of the first upper waveguide segment is 0.53 μm, The preset distance Ws is 0.48 μm, the width W2 of the wide end face of the second upper waveguide is 0.60 μm, and the width W3 of the narrow end face of the third symmetrical transmission section is 0.43 μm. In addition, the length Ltp1 of the first symmetrical transmission segment 121 is 28.3 μm, the length Ltp2 of the second symmetrical transmission segment 122 is 25 μm, and the length Ltp3 of the third symmetrical transmission segment 123 is 7 μm. In the fourth example, the width W0 of the input waveguide is 0.47 μm, the width W0 of the narrow end face of the first upper waveguide is 0.47 μm, and the width W1 of the wide end face of the first upper waveguide segment is 0.57 μm, The preset distance Ws is 0.52 μm, the width W2 of the wide end face of the second upper waveguide is 0.64 μm, and the width W3 of the narrow end face of the third symmetrical transmission section is 0.47 μm. In addition, the length Ltp1 of the first symmetrical transmission segment 121 is 28.7 μm, the length Ltp2 of the second symmetrical transmission segment 122 is 25.5 μm, and the length Ltp3 of the third symmetrical transmission segment 123 is 8 μm. In the fifth example, the width W0 of the input waveguide is 0.49 μm, the width W0 of the narrow end face of the first upper waveguide is 0.49 μm, and the width W1 of the wide end face of the first upper waveguide segment is 0.59 μm, The preset distance Ws is 0.54 μm, the width W2 of the wide end face of the second upper waveguide is 0.66 μm, and the width W3 of the narrow end face of the third symmetrical transmission section is 0.47 μm. In addition, the length Ltp1 of the first symmetrical transmission segment 121 is 28.9 μm, the length Ltp2 of the second symmetrical transmission segment 122 is 26 μm, and the length Ltp3 of the third symmetrical transmission segment 123 is 10 μm.

As an example, the Mach-Zehnder interferometer includes an SOI substrate, the SOI substrate includes a bottom silicon layer 201 , a buried oxide layer 202 and a top silicon layer, the first mode converter 12 , the connecting arm 13 and the The second mode converters 14 are formed by etching the top silicon layer. Wherein, the upper waveguide segment layer 206 and the lower waveguide segment layer 207 of each symmetrical transmission are formed by two etchings, that is to say, it can be considered that each upper waveguide segment constitutes the upper waveguide segment layer 206, and each lower waveguide segment can be considered to constitute The lower waveguide segment layer 207 can be referred to the schematic diagrams in FIGS. 3-6 for details. The first mode converter, the connecting arm and the second mode converter in the temperature-insensitive Mach-Zehnder interferometer based on the Y-branch symmetric structure of the Mach-Zehnder interferometer of the present invention are prepared based on the SOI substrate. The thermo-optic coefficient of the silicon in the material is very large (up to 1.86×10-4RIU/K, where RIU is the refractive index unit), which can cause a considerable wavelength shift (about 80pm/K) with temperature. Based on this On the other hand, the temperature insensitivity can be realized by setting parameters such as the width and thickness of the connecting arm; at the same time, the temperature insensitive Mach-Zehnder interferometer of the present invention can be compatible with the CMOS process and is convenient for mass production. The two mode converters in the Mach-Zehnder interferometer are connected by a connecting arm, which has a simple structure and small loss. In addition, in an optional example, the input waveguide and the output waveguide are also prepared based on the top silicon layer.

As an example, as shown in FIG. 7 , the temperature-insensitive Mach-Zehnder interferometer further includes a protective layer 208 , the protective layer 208 is located on the upper surface of the buried oxide layer 202 and completely covers the first mode conversion The device, the connecting arm and the second mode converter are used to protect the first mode converter, the connecting arm and the second mode converter. In one example, the protective layer 208 may include, but is not limited to, a silicon oxide layer.

As an example, the width of the connecting arm 13 can be set according to actual needs. Preferably, the width of the connecting arm 13 is 569 nm. In order to achieve the temperature insensitivity of the device, the width of the multimode waveguide needs to meet different requirements. The d _neff /dT coefficients in the mode are equal; Figure 8 shows the curve of the width of the connecting arm and the rate of change of the effective refractive index of the incident light in different modes relative to the temperature in the temperature-insensitive Mach-Zehnder interferometer provided by the present invention. When the two modes of incident light have the same effective refractive index change rate with respect to temperature (d _neff /dT), the corresponding width of the connecting arm 13 is the corresponding connecting arm 13 when temperature insensitivity can be realized. It can be seen that when the width of the multimode waveguide is 569 nm, the dneff/dT coefficients in TM ₀ and TE ₁ modes are both 1.289*10 ^-4 /K, and the device can achieve temperature insensitivity.

In addition, please refer to Figure 9. In order to verify the temperature characteristics of the device, the transmission spectrum of the device at 20°C and 50°C is simulated. The incident light is taken as TM0 mode, and the output light is taken as an example in TM0 mode, as can be seen from Figure 9 , the simulation results are shown, the temperature sensitivity of the device with temperature change is only 15pm/℃, and the device has temperature insensitive characteristics. The temperature-insensitive Mach-Zehnder interferometer of the present invention has approximately the same performance at different temperatures, and the performance of the temperature-insensitive Mach-Zehnder interferometer of the present invention is not greatly affected by temperature, that is, FIG. 9 further proves the present invention The temperature-insensitive Mach-Zehnder interferometer is insensitive to temperature.

In addition, please refer to FIG. 10 to FIG. 13 , in which, the mixed mode light is obtained in the middle of the device of the present invention, and the output light is not a mixed mode, and finally a single output light is obtained. As shown in the figure, there are four types of input and output. Situation: that is, incident in TM0 mode, the output light is TM0 mode; incident in TM0 mode, output light is TE1 mode; incident in TE1 mode, output light is TM0 mode; incident in TE1 mode, output light is TE1 mode; The 569nm wide waveguide (connecting arm) transmits mixed-mode light, and the two ends of the device adopt a symmetrical pattern to obtain a single output light. As can be seen from the results in the figure, in order to verify the overall performance of the device and simulate, the temperature-insensitive Mach-Zehnder interferometer of the present invention can obtain the TM0 mode and TE1 mode regardless of the input of the incident light in the TM0 mode or the incident light in the TE1 mode. Blend mode outgoing light. The overall simulation results of the device are shown in the figure above. The insertion loss of the device under each port is less than 0.3dB, and the extinction ratio is greater than 20dB. In addition, FIG. 14 shows a schematic diagram of the simulated mode field of the device.

It should be noted that, based on the design of the present invention, the device includes two identical double-layer tapered structures and a multi-mode waveguide. The temperature-insensitive Mach-Zehnder interferometer can output both the TM0 mode and the TE1 mode outgoing light at the output no matter whether the input end inputs the TM0 mode incident light or the TE1 mode input light. The purpose of the double-layer tapered structure is to obtain mixed modes, and the working principle can be: for example, when the TM0 mode is incident into the device, there is a mode mixing region in the part where the width of the waveguide changes from W0 to W1, where the modes mix The effective refractive indices of TM0 and TE1 in the region are equal, and the symmetry of the structure in the vertical direction is broken by the etching part, at this time, the TM0 mode is converted into the TE1 mode. In the variation interval of the waveguide width W1-W2 of the structure, when the width of W2 is 0.62 μm, part of the TE1 mode will be converted back to the TM0 mode, so that the mixed mode of TM0 and TE1 can be obtained. At this time, the ratio of TM0 to TE1 after passing through the double-layer tapered mode coupler is about 50:50. The simulation results are shown in Figure 15. The incident light in the TM0 mode is input from the input waveguide section; in the first symmetrical transmission section, the effective refractive indices of TM0 and TE1 are equal, and the TM0 mode is converted into the TE1 mode; in the second symmetrical transmission section, part of the TE1 mode The light is converted back to TM0 mode light to obtain mixed mode light of TM0 and TE1. Further, the device is finally prepared to obtain a Mach-Zehnder interferometer. The function of the mixed-mode light is to make the device temperature insensitive. A symmetrical structure is added to the right side of the device to convert the mixed-mode light back to a single-mode light again. Thereby an interference pattern is obtained, and the structure of the present invention can be regarded as a special MZI structure.

In addition, referring to FIGS. 1-7 , the present invention also provides a method for preparing a Mach-Zehnder interferometer based on TMO mode light as described in any one of the above solutions, wherein the structure and material composition of each material layer are For the description of the features, reference may be made to the description of the structure of the interferometer in the present invention, which will not be repeated here. In the preparation process, the mask plate is deposited first, then the photoresist is spin-coated for photolithography, then silicon etching is performed, and finally the upper cladding layer is deposited. The preparation method specifically comprises the steps:

1) Provide an SOI substrate, the SOI substrate includes a bottom silicon layer 201, a buried oxide layer 202 and a top silicon layer 203;

2) Etching the top silicon layer 203 based on the etching mask layer 204 to form the first mode converter 12 , the connecting arm 12 and the second mode converter 14 . Wherein, the upper waveguide segment layer 206 and the lower waveguide segment layer 207 for each symmetrical transmission are formed by two etchings, for example, the initial layer 205 is formed by the first etching, and then the upper waveguide segment is formed by the second etching layer 206 and lower waveguide segment layer 207. That is to say, it can be considered that each upper waveguide segment constitutes the upper waveguide segment layer 206 , and each lower waveguide segment can be considered to constitute the lower waveguide segment layer 207 . Additionally, the step of depositing a protective layer 208 may also be included.

To sum up, the Mach-Zehnder interferometer based on TM0 mode light and the preparation method thereof of the present invention can realize that the output end can output both the TM0 mode and the TE1 mode regardless of whether the input end inputs the TM0 mode incident light or the TE1 mode input light. Mode of outgoing light; can effectively solve the problems of the Mach-Zehnder interferometer existing in the prior art that are sensitive to temperature, complex in structure, large in size, etc.; can be compatible with CMOS process, easy for mass production, and can be realized on the silicon photonics process platform High quality mass production. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (9)

1. a Mach-Zehnder interferometer based on TM0 mode light, is characterized in that, described Mach-Zehnder interferometer comprises: input waveguide; a first mode converter connected to the input waveguide, the first mode converter having a double-layer tapered structure; The second mode converter is located on one side of the first mode converter and has a space between the first mode converter and the second mode converter, the second mode converter and the first mode converter have the same structure and Symmetrical settings; a connecting arm, located between the first mode converter and the second mode converter, one end is connected with the first mode converter, the other end is connected with the second mode converter, and the the connecting arm includes a straight waveguide segment; an output waveguide, connected to the second mode converter, to output mixed mode output light including TM0 mode light; The first mode converter includes: a first symmetrical transmission section, a second symmetrical transmission section and a third symmetrical transmission section connected in sequence; the first symmetrical transmission section is connected with the input waveguide, and the third symmetrical transmission section is connected to the input waveguide. The transmission section is connected with the connecting arm; the second mode converter includes: a fourth symmetrical transmission section, a fifth symmetrical transmission section and a sixth symmetrical transmission section connected in sequence; the fourth symmetrical transmission section is connected to the The connecting arm is connected, and the sixth symmetrical transmission section is connected with the output waveguide; the first symmetrical transmission section includes a first upper waveguide section and a first lower waveguide section located below and symmetrical about it; the second The symmetric transmission section includes a second upper waveguide section and a second lower waveguide section located below and symmetric about it; the fifth symmetric transmission section includes a fifth upper waveguide section and a fifth lower waveguide section located below and symmetric about it segment; the sixth symmetrical transmission segment includes a sixth upper waveguide segment and a sixth lower waveguide segment located below and symmetric about it, so as to form the double-layered tapered structure; Wherein, the incident light of TM0 mode or TE1 mode is input from the input waveguide section; in the first symmetrical transmission section, the effective refractive indices of TM0 and TE1 are equal, and the TM0 mode is converted to the TE1 mode; in the second symmetrical transmission section segment, part of the TE1 mode light is converted back to the TM0 mode light to obtain the mixed mode light of TM0 and TE1; the width of the connecting arm ensures the change rate of the effective refractive index relative to the temperature when the TM0 and TE1 mode light is transmitted in it equal. 2 . The Mach-Zehnder interferometer based on TM0 mode light according to claim 1 , wherein the sum of the thicknesses of the first lower waveguide segment and the first upper waveguide segment, the second lower waveguide The sum of the thicknesses of the second upper waveguide segment and the third symmetrical transmission segment is equal to the thickness of the third symmetrical transmission segment; the thicknesses of the fourth symmetrical transmission segment, the fifth lower waveguide segment and the fifth upper waveguide segment are equal. and the sum of the thicknesses of the sixth lower waveguide segment and the sixth upper waveguide segment is equal. 3 . The Mach-Zehnder interferometer based on TM0 mode light according to claim 2 , wherein the thicknesses of the first upper waveguide segment and the first lower waveguide segment are equal, and the thickness of the input waveguide is 3 . The thickness of the first upper waveguide section is twice the thickness of the first upper waveguide section; the thicknesses of the second upper waveguide section and the second lower waveguide section are equal; the thicknesses of the fifth upper waveguide section and the fifth lower waveguide section are equal; The thicknesses of the sixth upper waveguide section and the sixth lower waveguide section are equal. 4 . The Mach-Zehnder interferometer based on TM0 mode light according to claim 1 , wherein the first lower waveguide segment has a narrow end face and a wide end face, and the first upper waveguide segment has a narrow end face and a wide end face 4 . The width of the narrow end face of the first lower waveguide segment is equal to the width of the narrow end face of the first upper waveguide segment, and the wide end face of the first lower waveguide segment is larger than the two sides of the wide end face of the first upper waveguide segment. respectively preset distances; the second lower waveguide segment has a narrow end surface and a wide end surface, the second upper waveguide segment has a narrow end surface and a wide end surface, and the wide end surface of the second lower waveguide segment is the same as the first lower waveguide segment. The width of the wide end face of the waveguide section is equal, the narrow end face of the second upper waveguide section is connected to the wide end face of the first upper waveguide section and has the same width, and the narrow end face of the second lower waveguide section is the same as the second upper waveguide section. The widths of the wide end faces of the upper waveguide segment are equal; the fifth lower waveguide segment has a narrow end face and a wide end face, the fifth upper waveguide segment has a narrow end face and a wide end face, and the narrow end face of the fifth lower waveguide segment is the same as the width. The widths of the wide end faces of the fifth upper waveguide section are equal; the sixth lower waveguide section has a narrow end face and a wide end face, the sixth upper waveguide section has a narrow end face and a wide end face, and the sixth lower waveguide section has a narrow end face and a wide end face. The width of the narrow end face is equal to the narrow end face of the sixth upper waveguide segment and is connected to the output waveguide, and the width of the wide end face of the sixth lower waveguide segment is equal to the width of the wide end face of the fifth lower waveguide segment, so The wide end face of the sixth lower waveguide segment is larger than the preset distance on both sides of the broad end face of the sixth upper waveguide segment. 5 . The Mach-Zehnder interferometer based on TM0 mode light according to claim 4 , wherein the width of the input waveguide is 0.40 μm-0.50 μm, and the width of the narrow end face of the first upper waveguide is 0.40 μm. 6 . μm-0.50 μm, the width of the wide end face of the first upper waveguide segment is 0.50 μm-0.60 μm, the preset distance is 0.45 μm-0.55 μm, and the width of the wide end face of the second upper waveguide is 0.57 μm -0.67μm, the width of the narrow end face of the third symmetrical transmission section is 0.40μm-0.50μm; the length of the first symmetrical transmission section is 28μm-29μm, the length of the second symmetrical transmission section is 24μm-26μm, The length of the third symmetrical transmission section is 5 μm-10 μm; the width of the straight waveguide section of the connecting arm is 0.40 μm-0.50 μm, and the width of the wide end face of the fifth upper waveguide is 0.57 μm-0.67 μm , the width of the narrow end face of the fifth upper waveguide is 0.40 μm-0.50 μm, the width of the wide end face of the sixth upper waveguide segment is 0.50 μm-0.60 μm, and the width of the narrow end face of the fourth symmetrical transmission segment is 0.40 μm-0.50 μm; the length of the sixth symmetrical transmission segment is 28 μm-29 μm, the length of the fifth symmetrical transmission segment is 24 μm-26 μm, and the length of the fourth symmetrical transmission segment is 5 μm-10 μm. 6 . The Mach-Zehnder interferometer based on TM0 mode light according to claim 1 , wherein the Mach-Zehnder interferometer comprises an SOI substrate, and the SOI substrate comprises an underlying silicon layer, a buried oxide layer and The top silicon layer, the first mode converter, the connecting arm and the second mode converter are all formed by etching the top silicon layer. 7. The Mach-Zehnder interferometer based on TM0 mode light according to claim 6, wherein the Mach-Zehnder interferometer further comprises a protective layer, and the protective layer is located on the upper surface of the buried oxygen layer, And completely cover the first mode converter, the connecting arm and the second mode converter. 8 . The Mach-Zehnder interferometer based on TM0 mode light according to claim 1 , wherein the width of the straight waveguide section of the connecting arm is 569 nm. 9 . 9. A preparation method of a Mach-Zehnder interferometer based on TMO mode light as described in any one of claims 1 to 8, wherein the preparation method comprises the steps: An SOI substrate is provided, the SOI substrate includes a bottom silicon layer, a buried oxide layer and a top silicon layer; The top silicon layer is etched to form the first mode converter, the connecting arm and the second mode converter.

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