CN112068255B

CN112068255B - Optical fiber coupling alignment structure, preparation method and optical fiber coupling method

Info

Publication number: CN112068255B
Application number: CN202010887753.4A
Authority: CN
Inventors: 任恒江; 罗杰; 杨帆
Original assignee: Individual
Current assignee: Shenzhen Conjugate Technology Co ltd
Priority date: 2020-08-28
Filing date: 2020-08-28
Publication date: 2021-07-20
Anticipated expiration: 2040-08-28
Also published as: CN112068255A

Abstract

The invention provides an optical fiber coupling alignment structure from an optical fiber to an optical waveguide structure, a preparation method and a method for coupling the optical fiber to an optical component, wherein the preparation method of the optical fiber coupling alignment structure comprises the following steps: the optical fiber groove, the optical waveguide structure and the auxiliary alignment part are prepared in the substrate, the longitudinal section of the optical fiber groove comprises a square shape, the alignment base surface of the auxiliary alignment part is attached to the coupling end surface of the optical fiber, three surfaces of the optical fiber groove are in contact with the optical fiber to be coupled, the upper part, the lower part, the left part and the right part of the optical fiber to be coupled can be automatically aligned with the optical waveguide structure, the optical fiber groove with the square section, the side wall of which is vertical to the bottom, of the optical fiber groove can be prepared on the basis of a dry etching process, the preparation of the optical fiber alignment coupling structure is compatible with other processes (such as an MEMS process), and the size of the optical fiber groove can be flexibly controlled according to the size of the optical fiber. The optical fiber groove, the optical waveguide structure and the auxiliary alignment part can be formed based on the same photoetching process, and the optical fiber groove, the optical waveguide structure and the auxiliary alignment part are beneficial to accurate alignment of the optical fiber to be coupled and the optical waveguide structure.

Description

Optical fiber coupling alignment structure, preparation method and optical fiber coupling method

Technical Field

The invention belongs to the field of optical fiber signal transmission, and particularly relates to an optical fiber coupling alignment structure, a preparation method thereof and a method for coupling an optical fiber to an optical component.

Background

In the signal transmission process of the optical fiber, the optical fiber needs to be coupled and aligned with an active or passive optoelectronic device, so as to realize the signal transmission process. For example, optical fibers that transmit information using electromagnetic signals at infrared wavelengths must be coupled to a silicon photonic chip or other optical component, i.e., properly mounted in a precisely aligned position, in order to ensure a sufficiently high coupling efficiency between the optical fiber and the silicon photonic chip for proper signal transmission. The two exit ends of each fiber need to be properly aligned at the respective photonic chip or photonic element (e.g., optical transmitter, receiver, or transceiver) to which it is connected. The rise of integrated optical systems has driven the development of many fiber-to-silicon optical chip coupling methods that can efficiently couple light from optical modes on the order of 10 microns in fiber diameter into sub-micron silicon optical waveguides at the chip surface.

Currently, common approaches to optical input/output include side evanescent field couplers, iso-pyramidal evanescent field couplers, and grating couplers. Side-evanescent-field coupler and tapered fiber coupling is one method of coupling from the side or front to an on-chip waveguide through the evanescent field of a tapered fiber. This technique uses specially formed fiber tapers, which limits the number of input and output channels and greatly increases the cost and complexity of the device, and is also susceptible to vibration noise and power instability related effects.

Another common coupling technique utilizes a grating patterned on the chip surface. A well designed grating coupler can theoretically convert more than 90% of incident light to an optical waveguide on a chip over a bandwidth of a few THz, occupies only tens of square microns of space, and requires only micron-scale alignment accuracy. However, in grating couplers, the fiber or fiber assembly must be held at a design-determined angle to the normal of the chip surface to achieve efficient coupling. This is typically accomplished by creating a support structure on the fiber surface through additional handling layers and securing the fiber at an angle around the larger assembly of chips. These additional processing steps make the method difficult to package with components such as sensor chips based on silicon photonics.

Therefore, it is necessary to provide an optical fiber coupling alignment structure, a method for fabricating the same, and a method for coupling an optical fiber to an optical module, so as to solve the above-mentioned problems in the prior art.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an optical fiber coupling alignment structure and a method for manufacturing the same, and a method for coupling an optical fiber to an optical module, which are used to solve the problems in the prior art, such as complicated optical fiber coupling manner, difficulty in improving coupling efficiency, difficulty in achieving effective alignment of the optical fiber, and difficulty in being compatible with existing processing methods such as MEMS.

To achieve the above and other related objects, the present invention provides a method for fabricating an optical fiber coupling alignment structure of an optical fiber to an optical waveguide structure, the method comprising the steps of:

providing a substrate; and

etching the substrate to form an optical fiber groove, an optical waveguide structure and an auxiliary alignment part, wherein the optical fiber groove is used for placing an optical fiber to be coupled, the optical fiber to be coupled is provided with an optical fiber coupling end face, the auxiliary alignment part is provided with an alignment base face, the longitudinal section of the optical fiber groove is square, the bottom and the side wall of the optical fiber groove are both in contact with the surface of the optical fiber to be coupled, and the alignment base face is attached to the optical fiber coupling end face so that the center of the optical waveguide structure is aligned with the center of the optical fiber to be coupled.

Optionally, the optical fiber groove and the optical waveguide structure are formed based on the same dry etching process, and the specific steps include:

forming a patterned mask layer on the substrate, wherein the patterned mask layer comprises a first opening, a second opening and a third opening which are communicated with the first opening, the cross section of the first opening is consistent with the cross section of the optical fiber groove to be formed, and the cross section of the material layer between the second opening and the third opening is consistent with the cross section of the optical waveguide structure;

and etching the substrate based on the graphical mask layer to obtain the optical fiber groove and the optical waveguide structure, wherein the optical fiber groove is obtained corresponding to the first opening, the first optical waveguide groove is obtained corresponding to the second opening, the second optical waveguide groove is obtained corresponding to the third opening, and the optical waveguide structure is formed between the first optical waveguide groove and the second optical waveguide groove.

Optionally, the first optical waveguide groove and the second optical waveguide groove have the same cross-sectional shape, and both the first optical waveguide groove and the second optical waveguide groove include a first optical waveguide groove section and a second optical waveguide groove section, wherein the cross-sectional shape of the first optical waveguide groove section includes a trapezoid shape, the cross-sectional shape of the second optical waveguide groove section includes a square shape, the second optical waveguide groove section is located on one side of the first optical waveguide groove section, which is far away from the optical fiber groove, and the width of the first optical waveguide groove section, which is close to one end of the optical fiber groove, is greater than the width of the end of the optical fiber groove.

Optionally, the base includes an SOI substrate including, from bottom to top, a bottom layer silicon, an oxide layer, and a top layer silicon, wherein the optical fiber groove penetrates through the top layer silicon and the oxide layer stops in the bottom layer silicon, and the optical waveguide structure is formed in the top layer silicon.

Optionally, after the optical fiber groove and the optical waveguide structure are formed by etching, the method further includes: and removing the oxide layer below the optical waveguide structure to form a gap between the bottom silicon and the optical waveguide structure at the corresponding position, so as to obtain the optical waveguide structure arranged in a suspended manner.

Optionally, the gap is formed by a dry etching process using an etchant, and the optical fiber groove, the optical waveguide structure, and the auxiliary alignment portion are formed by a dry etching process using a dry etching agent, wherein the etchant used for dry etching includes gaseous hydrofluoric acid.

Optionally, the optical waveguide structure has a first end face and a second end face opposite to each other, the first end face is exposed in the optical fiber groove, and the width of the first end face is smaller than that of the second end face.

Optionally, the optical waveguide structure comprises a first portion and a second portion, the first portion comprising the first end face and the second portion comprising the second end face, wherein a width of the first portion gradually increases in a direction from the first end face to the second portion; the cross-sectional shape of the second portion comprises a square.

Optionally, the top of the optical fiber groove is flush with the upper surface of the optical waveguide structure, and the depth of the optical fiber groove is equal to the sum of half of the thickness of the optical waveguide structure and the radius of the optical fiber to be coupled; the width of the optical fiber groove is equal to the diameter of the optical fiber to be coupled.

Optionally, a space is provided between the auxiliary alignment portion and the optical waveguide structure, the optical waveguide structure has a waveguide coupling end surface, the waveguide coupling end surface is attached to the optical fiber coupling end surface to realize the coupling between the optical fiber to be coupled and the optical waveguide structure, and the alignment base surface and the waveguide coupling end surface are located on the same plane, so that the optical fiber coupling end surface is attached to the waveguide coupling end surface and the alignment base surface at the same time.

Optionally, the auxiliary alignment structures are formed on two sides of the optical waveguide structure, the alignment base surface is perpendicular to the bottom of the optical fiber groove, and the alignment base surface and a side wall of the optical fiber groove parallel to the optical fiber to be coupled are arranged in an L shape.

The invention also provides an optical fiber coupling alignment structure of an optical fiber-optical waveguide structure, which is preferably prepared by the preparation method of the optical fiber-optical waveguide structure, of course, other methods can be adopted, wherein the optical fiber coupling alignment structure comprises a substrate, an optical waveguide structure and an auxiliary alignment part, an optical fiber groove is formed in the substrate, the optical fiber groove is used for placing an optical fiber to be coupled, the optical fiber to be coupled is provided with an optical fiber coupling end face, the auxiliary alignment part is provided with an alignment base face, wherein the longitudinal section of the optical fiber groove comprises a square shape, the bottom and the side wall of the optical fiber groove are both contacted with the surface of the optical fiber to be coupled, the alignment basal plane is attached to the optical fiber coupling end face, so that the center of the optical waveguide structure is aligned with the center of the optical fiber to be coupled.

Optionally, a first optical waveguide groove and a second optical waveguide groove communicated with the optical fiber groove are further formed in the substrate, the optical waveguide structure is located between the first optical waveguide groove and the second optical waveguide groove, wherein the first optical waveguide groove and the second optical waveguide groove have the same cross-sectional shape, the first and second optical waveguide grooves each include a first optical waveguide groove section and a second optical waveguide groove section, the cross-sectional shape of the first optical waveguide groove segment comprises a trapezoid, the cross-sectional shape of the second optical waveguide groove segment comprises a square, the second optical waveguide groove segment is located on a side of the first optical waveguide groove segment remote from the optical fiber groove, and the width of the first optical waveguide groove section close to one end of the optical fiber groove is larger than that of the first optical waveguide groove section far away from one end of the optical fiber groove.

Optionally, the base includes an SOI substrate including, from bottom to top, a bottom layer of silicon, an oxide layer, and a top layer of silicon, wherein the fiber groove penetrates through the top layer of silicon and the oxide layer stops in the bottom layer of silicon, and the optical waveguide structure is formed based on the top layer of silicon.

Optionally, a gap is formed between the optical waveguide structure and the bottom layer silicon at a corresponding position below the optical waveguide structure, and the optical waveguide structure is suspended.

Optionally, a space is provided between the auxiliary alignment portion and the optical waveguide structure, the optical waveguide structure has a waveguide coupling end surface, the waveguide coupling end surface is attached to the optical fiber coupling end surface to realize coupling between the optical fiber to be coupled and the optical waveguide structure, and the alignment base surface and the waveguide coupling end surface are located on the same plane, so that the optical fiber coupling end surface is attached to the waveguide coupling end surface and the alignment base surface at the same time.

The present invention also provides a method of coupling an optical fiber to an optical package, comprising the steps of:

providing a fibre coupling alignment structure of a fibre to optical waveguide structure according to any one of the previous aspects;

placing an optical fiber to be coupled in the optical fiber groove to align a center of the optical fiber to be coupled with a center of the optical waveguide structure.

Optionally, the method further comprises the step of forming an adhesive layer in the optical fiber groove, wherein the adhesive layer fixes the optical fiber to be coupled in the optical fiber groove.

As described above, according to the optical fiber-to-optical waveguide structure optical fiber coupling alignment structure, the manufacturing method thereof, and the method for coupling an optical fiber to an optical component of the present invention, the longitudinal cross-sectional shape of the optical fiber groove includes a square shape, so as to facilitate alignment of the optical fiber to be coupled with the optical waveguide structure, three sides of the optical fiber groove are in contact with the optical fiber to be coupled, and can be in contact in a tangential manner, the up-down position, the left-right position, and the front-back position of the optical fiber to be coupled can be automatically aligned with the optical waveguide structure, and the optical fiber groove with the square cross-section whose side wall is perpendicular to the bottom can be manufactured based on a dry etching process, so that the manufacturing of the optical fiber coupling alignment structure is compatible with other processes (such as an MEMS process), and simultaneously, the optical fiber coupling structure is compatible with an optical MEMS structure (partial structure suspension), and the size of the optical fiber groove can be flexibly controlled. In addition, the optical fiber groove and the optical waveguide structure are formed based on the same photoetching process, so that the accurate alignment of the optical fiber to be coupled and the optical waveguide structure is facilitated.

Drawings

FIG. 1 is a flow chart illustrating the fabrication of an optical fiber coupling alignment structure according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a substrate for use in preparing an exemplary fiber coupling alignment structure according to the present invention.

FIG. 3 is a schematic diagram of a patterned mask layer formed in the fabrication of an exemplary fiber-coupled alignment structure according to the present invention.

FIG. 4 is a top view of an exemplary fiber coupling alignment structure according to the present invention.

Fig. 5 is a cross-sectional view along AA' in fig. 4.

Fig. 6 is a cross-sectional view taken along direction BB' in fig. 4.

FIG. 7 is a cross-sectional view along the direction AA' in FIG. 4 after the optical fiber to be coupled is placed in the groove of the optical fiber according to the present invention.

Fig. 8 is a perspective view of the optical fiber coupling alignment structure of the present invention after placing an optical fiber to be coupled.

Description of the element reference numerals

100 substrate

101 bottom layer silicon

102 oxide layer

103 top layer silicon

104 optical fiber groove

105 first optical waveguide groove

1051 a first optical waveguide groove segment

1052 second optical waveguide groove section

106 second optical waveguide grooves

107 optical waveguide structure

1071 first part

1072 second part

107a first end face

107b second end face

107c interface surface

108 gap

109 support column structure

200 patterned mask layer

201 first opening

202 second opening

203 third opening

300 optical fiber to be coupled

S1-S2

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structures are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.

For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, 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. "between … …" in the present invention is meant to include both end-points to the range.

In the context of this application, a structure described as having a first feature "on" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed freely, and the layout of the components may be more complicated.

As shown in fig. 1, the present invention provides a method for preparing an optical fiber coupling alignment structure, comprising the following steps:

s1: providing a substrate; and

s2: etching the substrate to form an optical fiber groove, an optical waveguide structure and an auxiliary alignment part, wherein the optical fiber groove is used for placing an optical fiber to be coupled, the optical fiber to be coupled is provided with an optical fiber coupling end face, the auxiliary alignment part is provided with an alignment base face, the longitudinal section of the optical fiber groove is square, the bottom and the side wall of the optical fiber groove are both in contact with the surface of the optical fiber to be coupled, and the alignment base face is attached to the optical fiber coupling end face so that the center of the optical waveguide structure is aligned with the center of the optical fiber to be coupled.

The method for fabricating the optical fiber coupling alignment structure according to the present invention will be described in detail with reference to the accompanying drawings.

First, as shown in S1 of fig. 1 and fig. 2, step S1 is performed to provide the substrate 100. The substrate 100 may be any semiconductor structure to which it is desired to couple an optical fiber, for example, the substrate 100 may be a silicon optical chip commonly used in the art. The substrate 100 may be a stacked structure composed of multiple material layers, or a structure composed of a single material layer, such as a silicon material layer, which is selected according to actual requirements. In one example, the substrate 100 is selected as an SOI substrate, and as shown in fig. 2, the SOI substrate includes, from bottom to top, a bottom silicon 101, an oxide layer 102, and a top silicon 103. In one example, the thickness of the top silicon 103 of the uppermost layer is between 200 and 250nm, and may be 220 nm; the thickness of the middle oxide layer 102 is between 2-4 μm, such as 3 μm, 3.5 μm; the thickness of the underlying silicon 101 is between 600 and 800 μm, such as 700 μm.

Next, as shown in S2 of fig. 1 and fig. 3-8, step S2 is performed to etch the substrate 100 to form the fiber groove 104, the optical waveguide structure 107 and the

auxiliary alignment portions

109 and 110.

Specifically, by this process, the optical fiber groove 104 for placing the optical fiber 300 to be coupled and the optical waveguide structure 107 for receiving the optical signal in the optical fiber 300 to be coupled and transmitting the received optical signal are obtained based on the substrate 100. Here, the longitudinal sectional shape of the fiber groove 104 includes a square shape, and may be, for example, a rectangle or a square, where the longitudinal section herein refers to a schematic sectional view on a plane perpendicular to the surface of the substrate 100, and the cross section refers to a schematic sectional view on a plane parallel to the surface of the substrate 100. Based on the above cross-sectional shape of the optical fiber groove 104, the bottom and the side wall of the optical fiber groove 104 are both in contact with the surface of the optical fiber 300 to be coupled, and the center of the optical waveguide structure 107 is aligned with the center of the optical fiber 300 to be coupled, so as to match the optical modes of the optical waveguide structure 107 and the optical fiber 300 to be coupled, and achieve extremely high coupling efficiency. The present invention implements a coupling scheme, which can efficiently implement the mutual transmission of signals between the optical waveguide structure and the optical fiber to be coupled on the substrate 100 (e.g., a single-sided silicon optical chip) based on the optical fiber groove 104 as an alignment structure, e.g., can efficiently transmit light from a silicon optical chip suspended optical waveguide (on-chip silicon waveguide) to a single-mode optical fiber on the silicon optical chip. In addition, the coupling alignment structure can be directly installed in any system with optical fiber ports, and the preparation process is simple.

The optical fiber groove 104 of the present invention is favorable for achieving stability in the optical fiber alignment process, and in addition, the optical fiber groove 104 having a square cross section with a side wall perpendicular to the bottom can be prepared based on a dry etching process, so that the preparation of the alignment coupling structure of the optical fiber 300 to be coupled is compatible with other processes (such as an MEMS process), and the width and depth of the optical fiber groove 104 can be flexibly controlled based on an etching process, therefore, the structure of the optical fiber groove can be flexibly designed according to requirements, in addition, through the optical fiber groove 104 and the optical waveguide structure 107, when the optical fiber to be coupled is placed in the optical fiber groove, the optical fiber to be coupled is automatically aligned with the optical waveguide structure, edge coupling of the optical fiber to be coupled is realized, the optical fiber to be coupled is transversely placed in the optical fiber groove, and compact chip packaging is facilitated.

In addition, the optical fiber groove 104 and the optical waveguide structure 107 are formed together with

auxiliary alignment portions

109 and 110, the auxiliary alignment portions have alignment base surfaces, that is, the auxiliary alignment portion 109 has an alignment base surface 109a, the auxiliary alignment portion 110 has an alignment base surface 110a, and the optical fiber to be coupled has an optical fiber coupling end surface, and the alignment base surface is attached to the optical fiber coupling end surface, so as to achieve front-back alignment of the optical fiber to be coupled based on attachment of the alignment base surface and the optical fiber coupling end surface. In an example, the

auxiliary alignment portions

109 and 110 and the optical waveguide structure 107 have a distance, for example, in the previous example, the distance is the width of the first optical waveguide groove 105 and the second optical waveguide groove 106, wherein the optical waveguide structure 107 has a waveguide coupling end surface, the first end surface 107a in the previous example, the optical fiber 300 to be coupled has an optical fiber coupling end surface, and the waveguide coupling end surface 107a is attached to the optical fiber coupling end surface to realize the coupling between the optical fiber 300 to be coupled and the optical waveguide structure 107, wherein in this example, the

alignment base surfaces

109a and 110a and the waveguide coupling end surface 107a are located on the same plane, so that the optical fiber coupling end surface is attached to the waveguide coupling end surface 107a and the

alignment base surfaces

109a and 110a at the same time. That is, through the process of the present invention, the material of the substrate portions on both sides of the optical waveguide structure can be etched to form a structure for alignment, i.e. the

auxiliary alignment portions

109 and 110, when the optical fiber 300 to be coupled is pushed into the optical fiber groove 104, the optical fiber coupling end automatically pushes against the

alignment base surfaces

109a and 110a, so that the front-back alignment of the optical fiber to be coupled and the optical waveguide structure can be automatically realized.

In one example, the

auxiliary alignment structures

109 and 110 are formed on two sides of the optical waveguide structure 107, the

alignment bases

109a and 110a are perpendicular to the bottom of the optical fiber groove 104, and the

alignment bases

109a and 110a are disposed in an L-shape parallel to the side wall of the optical fiber groove 104 of the optical fiber to be coupled. In this example, the

auxiliary alignment structures

109 and 110 are used as the side walls of the fiber groove 104 perpendicular to one surface of the optical fiber to be coupled, and form an L-shaped corner with the side walls of the fiber groove 104 parallel to the optical fiber to be coupled, thereby facilitating stable alignment coupling.

As shown in fig. 3 to 6, as an example, a method for manufacturing the optical fiber coupling alignment structure is provided, in this example, the optical fiber groove 104 and the optical waveguide structure 107 are formed based on the same dry etching process.

Specifically, the dry etching includes the following steps:

first, as shown in fig. 3, a patterned mask layer 200 is formed on the substrate 100, wherein fig. 3 is a schematic top view of the patterned mask layer 200. The patterned mask layer 200 includes a first opening 201, and a second opening 202 and a third opening 203 both communicating with the first opening 201. In an example, the patterned mask layer may be formed by coating a photoresist layer on the substrate 100 and then forming the patterned mask layer 200 by a photolithography process. In an example, the step of forming the patterned mask layer 200 may be to coat a layer of photoresist (not shown) on the substrate 100, and then perform photolithography and developer washing in a photolithography machine to form a desired pattern, so as to obtain the patterned mask layer 200. And then etching down based on the patterned mask layer 200 as a mask.

Specifically, the shape of the first opening 201 is consistent with the cross-sectional shape of the optical fiber groove 104 to be formed, and is used for obtaining the optical fiber groove 104 by etching based on the first opening 201 in the subsequent process of etching the substrate 100. The cross-sectional shape of the material layer between the second opening 202 and the third opening 203 is consistent with the shape of the optical waveguide structure 107, so that the optical waveguide structure 107 with a required shape is defined based on the second opening 202 and the third opening 203 in the subsequent etching process of the substrate 100. In the process of etching the substrate 100, portions of the substrate 100 corresponding to the second opening 202 and the third opening 203 are etched, and the remaining substrate 100 between the second opening 202 and the third opening 203 may be used to form the optical waveguide structure 107, in an alternative example, the edges of the second opening 202 and the third opening 203 that are close to each other may form the edges of the optical waveguide structure 107 that are formed subsequently.

Next, as shown in fig. 4-6, the substrate 100 is etched based on the patterned mask layer 200, for example, by using a plasma dry etching process, so as to obtain the optical fiber groove 104, the optical waveguide structure 107 and the

auxiliary alignment structures

109 and 110. Fig. 4 is a top view of the optical fiber groove 104 and the optical waveguide structure 107 obtained by etching the substrate 100, fig. 5 is a cross-sectional view along AA 'in fig. 4, and fig. 6 is a cross-sectional view along BB' in fig. 4. In an example, the pattern of the patterned mask layer 200 is transferred to the substrate 100 by performing the above etching with a plasma etcher, a portion not covered by the photoresist is etched, the optical fiber groove 104 is obtained corresponding to the first opening 201, the first optical waveguide groove 105 is obtained corresponding to the second opening 202, the second optical waveguide groove 106 is obtained corresponding to the third opening 203, the optical waveguide structure 107 is formed between the first optical waveguide groove 105 and the second optical waveguide groove 106, the first optical waveguide groove 105 is communicated with the optical fiber groove 104, and the second optical waveguide groove 106 is communicated with the optical fiber groove 104. In this step, the optical fiber groove 104 and the optical waveguide structure 107 are simultaneously obtained based on the same mask layer, that is, the patterned mask layer 200 is subjected to the same etching process.

In particular, the fiber grooves formed simultaneously with the optical waveguide structure provide advantages for fiber alignment over conventional evanescent field and grating coupler techniques that require nanometer scale sensitive positioning to achieve optical mode overlap. Due to floor space and packaging requirements, achieving nano-positioning in silicon chip integration is both difficult and expensive. The optical fiber groove and the optical waveguide structure formed by the same photoetching process are formed in one-step etching process, so that accurate positioning of dozens of nanometers can be obtained, including left-right accurate positioning, up-down accurate positioning and front-back accurate positioning. Problems with imprecise positioning of the fiber coupling alignment structure on the corresponding photonic chip, for example, which would reduce optical coupling efficiency, can be solved, and imprecise positioning of the pre-formed fiber coupling alignment structure on the photonic chip would reduce the tolerance for any positional mismatch between the fiber and the pre-formed coupling structure itself during fiber assembly. Although fiber mounting can be performed using passive, self-aligned fiber coupling without the need to actively measure the actual transmitted light intensity, any misalignment between the fiber and the photonic chip can result in a reduction in photonic chip tolerances, and pre-formed fiber alignment structures (e.g., fiber grooves) that are lithographically patterned simultaneously with the optical waveguide structure can facilitate improved optical coupling efficiency.

For example, referring to fig. 4, the cross-sectional shapes of the first optical waveguide groove 105 and the second optical waveguide groove 106 are the same, and for the first optical waveguide groove 105, the first optical waveguide groove 105 includes a first optical waveguide groove section 1051 and a second optical waveguide groove section 1052, wherein the cross-sectional shape of the first optical waveguide groove section 1051 includes a trapezoid, the cross-sectional shape of the second optical waveguide groove section 1052 includes a square, for example, a rectangle, the second optical waveguide groove section 1052 is located on the side of the first optical waveguide groove section 1051 away from the optical fiber groove 104, and the width s1 of the first optical waveguide groove section 1051 near the end of the optical fiber groove 104 is greater than the width s2 of the end of the first optical waveguide groove section 1051 away from the optical fiber groove 104. The optical waveguide structure is thin (initial width is w1), the optical mode of the optical waveguide structure is large (matched with the optical mode in the optical fiber), and the corresponding s1 is long, so that the optical loss caused by the fact that the optical mode extends to the structures on two sides (outside s 1) is avoided. As the width of the optical waveguide structure is gradually changed from W1 to W2, the optical mode gradually decreases, and the footprint on the silicon photonic chip decreases after the width is changed to s 2. In one example, as shown in FIG. 4, the width s1 of the first optical waveguide groove segment 1051 near the end of the fiber groove 104 has a dimension between 10 μm and 30 μm, for example, selected to be 20 μm; the width s2 of the first optical waveguide groove segment 1051 at the end remote from the fiber groove 104 has a dimension of between 3 μm and 5 μm, for example, 4 μm may be selected.

As an example, the base 100 includes an SOI substrate including, from bottom to top, a bottom layer silicon 101, an oxide layer 102, and a top layer silicon 103. That is, the optical fiber groove 104 and the optical waveguide structure 107 are prepared based on an SOI substrate, wherein the optical fiber groove 104 penetrates through the top silicon 103 and the oxide layer 102 and stops in the bottom silicon 101, the optical waveguide structure 107 is formed in the top silicon 103, that is, the optical waveguide structure 107 is made of the material of the top silicon 103, and the optical waveguide structure 107 is automatically formed when the top silicon 103 is etched.

In one example, referring to FIG. 5, the top silicon 103 has a thickness n1 between 200nm and 250nm, the oxide layer 102 has a thickness n2 between 3 μm and 7 μm, and the bottom silicon 101 has a thickness n3 between 650 μm and 750 μm. For example, in one example, the thickness of the top silicon 103 is selected to be 220nm, the thickness of the oxide layer 102 is selected to be 5 μm, and the thickness of the bottom silicon 101 is selected to be 700 μm.

As shown in fig. 6, as an example, after the optical fiber groove 104 and the optical waveguide structure 107 are formed by etching, the method further includes the steps of: and removing the oxide layer 102 below the optical waveguide structure 107 to form a gap 108 between the bottom silicon 101 and the optical waveguide structure 107 at a corresponding position, so as to obtain the optical waveguide structure 107 which is suspended.

In one example, the gap 108 may be formed using a dry etching process, such as an etching process using gaseous hydrofluoric acid, which does not etch silicon but instead etches silicon oxide by reacting with the silicon oxide. In this example, the etching of gaseous hydrofluoric acid is used on the silicon optical chip, that is, a dry etching process is adopted, and meanwhile, the etching process for forming the optical fiber groove and the optical waveguide structure in the previous step also adopts a dry etching process, and the two-step dry etching process is favorable for improving the product yield. Based on the above process, the problem of surface tension in the wet etching process can be solved, wherein the surface tension is formed in the wet etching process, but the finer suspended structure is easy to collapse in the invention. In addition, the suspended silicon optical waveguide part based on the process can be connected with a silicon optical MEMS element on a silicon optical chip subsequently. The optical waveguide structure 107 formed to be suspended can be more flexibly adapted to different optical elements, such as sensor optical elements, and by this exemplary arrangement, the optical waveguide structure 107 can be matched with the optical-micromechanical optical element, which needs to be suspended by a part of the micromechanical structure; and the optical loss is reduced when light rays propagate in the optical waveguide. In addition, the optical waveguide structure 107 may be suspended by other substrates, besides the SOI substrate, by using a process commonly used in the art. Of course, in other examples, the optical waveguide structure 107 may not be suspended.

In the above example, the optical waveguide structure 107 is formed in suspension, and at the same time, the underlying silicon 101 at the corresponding position below the optical waveguide structure 107 constitutes a support post structure 111. After the optical fiber 300 to be coupled is placed and installed, the supporting column structure 11 is in contact with the end surface of the optical fiber 300 to be coupled, which has a function of supporting and stabilizing, and is also beneficial to achieving front-back alignment when the optical fiber to be coupled is placed in the optical fiber groove 104.

Referring to fig. 4, the optical waveguide structure 107 has a first end face 107a and a second end face 107b opposite to each other, the first end face 107a is exposed in the optical fiber groove 104, and the width of the first end face 107a is smaller than that of the second end face 107 b. In this example, one end (the first end face 107a) of the optical waveguide structure 107 coupled to the optical fiber 300 to be coupled has a certain width w1, and the other end (the second end face 107b) of the optical waveguide structure has another width w2 when transmitting the signal of the optical fiber 300 to be coupled after coupling, where w2 is greater than w 1.

By way of example, the optical waveguide structure 107 includes a first portion 1071 and a second portion 1072, the first portion 1071 including the first end face 107a, the second portion 1072 including the second end face 107b, and further, a boundary between the first portion 1071 and the second portion 1072 may be considered to have an interface 107c, wherein a width of the first portion 1071 gradually increases in a direction from the first end face 107a to the second portion 1072; the cross-sectional shape of the second portion 1072 includes a square. That is, the cross-sectional shape of the second portion 1072 is square, may be rectangular, the length m2 of the second portion 1072 may be set according to practical requirements, may be infinitely elongated after it is converted into an on-chip waveguide, may be turned or routed to other elements, may keep the width constant in one example, and may be constant throughout, and may be w2, and the first portion 1071 may increase from w1 to w2, and may increase in a quadratic or cubic curve in one example, or even higher order curves. In one example, the first portion 1071 is symmetrical on both sides, the cross-sectional shape of the first portion 1071 is trapezoid, the first end face 107a is the upper base of the trapezoid, the width of the upper base of the trapezoid is w1, and the width of the lower base of the trapezoid is w 2.

Specifically, the optical mode in the actual optical fiber is relatively dispersed, for example, about 10 μm, but in the on-chip silicon optical waveguide (the optical waveguide structure 107), especially in the silicon optical waveguide in the other part of the silicon optical chip, the silicon optical waveguide is about 500nm, the optical mode is very concentrated, and based on the design of the present invention, the defect of optical fiber and optical waveguide mismatch is improved by designing the width variation of the optical waveguide structure 107, that is, the present invention designs that the width w1 of the first end face 107a close to the optical fiber groove 104 in the optical waveguide structure 107 is smaller than the width w2 of the second end face 107b far away from the optical fiber groove 104 in the optical waveguide structure 107, so that the optical mode in the silicon optical waveguide can be expanded at the first end face 107a with smaller width, so that the optical mode at the first end face 107a matches the optical mode in the optical fiber 300 to be coupled, reducing reflections between the two due to large differences in optical modes (reflections may include light from the fiber being reflected back into the fiber and light from the silicon optical waveguide being reflected back into the silicon optical waveguide). In one example, the width w1 of the first end face 107a of the optical waveguide structure 107 near the fiber groove 104 is between 80-200nm, for example 110 nm; the width w2 of the second end face 107b of the optical waveguide structure 107 away from the fiber groove 104 and the width of the second portion 1072 are both designed to be between 300 nm and 700nm, for example, 500nm is selected, so that most of the optical mode exists in the silicon material, and thus the optical mode of the optical waveguide structure is relatively small, and the loss caused thereby is relatively small. In other examples, the width w1 of the first end face 107a of the optical waveguide structure may be set to other dimensions depending on the internal structure of the optical fiber to be coupled to achieve better matching of optical modes.

In another example, the width of the first portion 1071 gradually increases in a direction from the first end face 107a to the second portion 1072, thereby gradually decreasing the optical mode in the process of gradually increasing the width, finally concentrating in the second portion 1072. In a further alternative example, the optical mode in the fiber is such that it is the fundamental optical mode, and when it passes to the tip of the tapered section (said first end face 107a), it is also the fundamental optical mode, i.e. the rate of change of the optical mode is slow enough that the fundamental optical mode is not disturbed until said second section 1072, it remains the fundamental optical mode and does not partially convert to a higher order optical mode, and thus no loss is caused by the partial change to a higher order optical mode. In one example, the length m1 of the first portion 1071 is between 100 and 500 μm, preferably greater than 200 μm, such as may be 300 μm, the width of the first end face 107a is between 80-200nm, and the width of the first and second portion interface 107c (the width of the interface 107c is equal to the width w2 of the second portion 1072) is between 300 and 700nm, such as may be 500 nm.

Referring to fig. 7 and 8, as an example, the top of the fiber groove 104 is flush with the upper surface of the optical waveguide structure 107, for example, in an example, the substrate 100 is selected as an SOI substrate, the fiber groove 104 and the optical waveguide structure 107 are formed by the same etching, and the upper surface of the top silicon 103 forms the top of the fiber groove 104 and the upper surface of the optical waveguide structure 107. In an example, as shown in fig. 7, the depth d1 of the optical fiber groove 104 is equal to the sum of half of the thickness n1 of the optical waveguide structure 107 and the radius r of the optical fiber 300 to be coupled, and the optical waveguide structure 107 is formed based on the top silicon 103, that is, the thickness of the optical waveguide structure 107 is n1, and the design of the above structure is such that when the optical fiber 300 to be coupled is placed in the optical fiber groove 104, the center thereof is automatically aligned with the center of the optical waveguide structure 107, which in this example is the center of the first end face 107a (the end face of the top silicon having the width w 1). In addition, the width of the fiber groove 104 is equal to the diameter of the optical fiber 300 to be coupled. The length of the fiber groove 104 (the dimension in the direction parallel to the optical fiber to be coupled) can be set according to practical requirements, and can be larger than 1 μm. One end of the optical waveguide structure 107 is in contact with one end of the optical fiber 300 to be coupled. In a specific alternative example, as shown in the structure of FIG. 4, the width w1 of the first end face 107a of the optical waveguide structure 107 is 110nm, the width w2 of the second end face 107b of the optical waveguide structure 107 is 500nm, the width s1 of the first portion 1051 of the first optical waveguide groove 105 near the fiber groove is 10 μm, and the width s2 of the second portion 1052 of the first optical waveguide groove 105 is 3 μm.

In addition, as shown in fig. 4 to 8 and referring to fig. 1 to 3, the present invention further provides an optical fiber coupling alignment structure, wherein the optical fiber coupling alignment structure is preferably prepared by the preparation method of the optical fiber coupling alignment structure of the present invention, and of course, may also be prepared by other methods.

The optical fiber coupling alignment structure comprises a substrate 100 and an optical waveguide structure 107, wherein an optical fiber groove 104 is formed in the substrate 100, the optical fiber groove 104 is used for placing an optical fiber 300 to be coupled, the longitudinal section of the optical fiber groove 104 comprises a square shape, the bottom and the side wall of the optical fiber groove 104 are both in contact with the surface of the optical fiber 300 to be coupled, in addition, the optical fiber coupling alignment structure further comprises

auxiliary alignment parts

109 and 110, the auxiliary alignment parts are provided with

alignment base surfaces

109a and 110a, the optical fiber to be coupled is provided with an optical fiber coupling end surface, the alignment base surfaces are attached to the optical fiber coupling end surfaces, and the center of the optical waveguide structure 107 is aligned with the center of the optical fiber 300 to be coupled. It can be understood by those skilled in the art that, for convenience of consistent description, the substrate 100 and the optical waveguide structure 107 in the optical fiber coupling alignment structure are separately described, and based on the description of the method for manufacturing the optical fiber coupling alignment structure in the present embodiment, the optical waveguide structure 107 can be obtained by etching the substrate 100.

Illustratively, the substrate 100 further has a first optical waveguide groove 105 and a second optical waveguide groove 106 formed therein and communicating with the optical fiber groove 104, the optical waveguide structure 107 is located between the first optical waveguide groove 105 and the second optical waveguide groove 106, wherein the first optical waveguide groove 105 and the second optical waveguide groove 106 have the same cross-sectional shape, the first optical waveguide groove 105 and the second optical waveguide groove 106 each comprise a first optical waveguide groove segment 1051 and a second optical waveguide groove segment 1052, the cross-sectional shape of the first optical waveguide groove segment 1051 comprises a trapezoid, the cross-sectional shape of the second optical waveguide groove segment 1052 comprises a square, the second optical waveguide groove segment 1052 is located on the side of the first optical waveguide groove segment 1051 away from the fiber groove 104, and the width of the first optical waveguide groove 1051 section near the end of the fiber groove 104 is larger than the width of the first optical waveguide groove section far from the end of the fiber groove 105.

As an example, the substrate 100 includes an SOI substrate including, from bottom to top, a bottom layer silicon 101, an oxide layer 102, and a top layer silicon 103, wherein the optical fiber groove 104 is stopped in the bottom layer silicon 101 through the top layer silicon 103 and the oxide layer 102, and the optical waveguide structure 107 is formed in the top layer silicon 103.

As an example, a gap 108 is formed between the optical waveguide structure 107 and the underlying silicon 101 at a corresponding position below, and the optical waveguide structure 107 is suspended.

Illustratively, the optical waveguide structure 107 has a first end face 107a and a second end face 107b opposite to each other, the first end face 107a is exposed in the optical fiber groove, and the width of the first end face 107a is smaller than that of the second end face 107 b.

By way of example, the optical waveguide structure 107 includes a first portion 1071 and a second portion 1072, the first portion 1071 including the first end face 107a and the second portion 1072 including the second end face 107b, wherein a width of the first portion 1071 gradually increases in a direction from the first end face 107a to the second portion 1072; the cross-sectional shape of the second portion 1072 includes a square.

Illustratively, the top of the fiber groove 104 is flush with the upper surface of the optical waveguide structure 107, and the depth of the fiber groove 104 is equal to the sum of half the thickness of the optical waveguide structure 107 and the radius of the optical fiber 300 to be coupled; the width of the fiber groove 104 is equal to the diameter of the optical fiber 300 to be coupled.

As an example, the

auxiliary alignment portions

109 and 110 are spaced apart from the optical waveguide structure 107, the optical waveguide structure has a waveguide coupling end surface, such as the first end surface 107a in the previous example, the optical fiber to be coupled has a fiber coupling end surface, and the waveguide coupling end surface is attached to the fiber coupling end surface to realize the coupling between the optical fiber to be coupled and the optical waveguide structure 107, wherein the

alignment base surfaces

109a and 110a are located on the same plane as the waveguide coupling end surface, so that the fiber coupling end surface is attached to the waveguide coupling end surface and the alignment base surface at the same time.

As an example, the

auxiliary alignment structures

109 and 110 are formed on two sides of the optical waveguide structure 107, the

alignment base surfaces

109a and 110a are disposed in an L-shape with the side wall of the optical fiber groove 104 parallel to the optical fiber to be coupled.

In addition, the present invention provides a method of coupling an optical fiber to an optical package, comprising the steps of:

providing a fiber coupling alignment structure of a fiber to optical waveguide structure according to any aspect of the present embodiment;

an optical fiber 300 to be coupled is placed in the optical fiber groove, where, in an example, referring to fig. 8, the optical fiber 300 to be coupled may be a single optical fiber entering from a splitter, and the optical fiber groove 104 is disposed in the silicon optical chip to align the center of the optical fiber to be coupled with the center of the optical waveguide structure, where, in this example, the optical waveguide structure is also disposed in the silicon optical chip.

As an example, the method further comprises the step of forming an adhesive layer in the fiber groove, wherein the adhesive layer fixes the optical fiber to be coupled in the fiber groove. For example, an adhesion layer is formed in the optical fiber groove in the silicon optical chip, and the adhesion layer adheres the optical fiber entering the silicon optical chip to the optical fiber groove of the silicon optical chip, wherein the adhesion layer may be an ultraviolet curing glue.

In summary, according to the optical fiber coupling alignment structure, the manufacturing method thereof, and the method for coupling an optical fiber to an optical assembly of the present invention, the shape of the longitudinal section of the optical fiber groove includes a square shape, so as to achieve alignment between the optical fiber to be coupled and the optical waveguide structure, three surfaces of the optical fiber groove are all in contact with the optical fiber to be coupled, and can be in contact in a tangential manner, the up-down position, the left-right position, and the front-back position of the optical fiber to be coupled can be automatically aligned with the optical waveguide structure, and the optical fiber groove with the square section whose side wall is perpendicular to the bottom can be manufactured based on a dry etching process, so that the manufacturing of the optical fiber coupling structure is compatible with other processes (such as an MEMS process), and the size of the optical fiber groove can be flexibly controlled. In addition, the optical fiber groove and the optical waveguide structure are formed based on the same photoetching process, so that the accurate alignment of the optical fiber to be coupled and the optical waveguide structure is facilitated. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A method for fabricating an optical fiber coupling alignment structure of an optical fiber to optical waveguide structure, the method comprising the steps of:

providing a base, wherein the base comprises an SOI (silicon on insulator) substrate, and the SOI substrate comprises bottom silicon, an oxidation layer and top silicon from bottom to top; and

etching the substrate to form an optical fiber groove, an optical waveguide structure and an auxiliary alignment part, wherein the optical fiber groove is used for placing an optical fiber to be coupled, the optical fiber to be coupled is provided with an optical fiber coupling end face, the auxiliary alignment part is provided with an alignment base face, the longitudinal section of the optical fiber groove comprises a square shape, the bottom and the side wall of the optical fiber groove are both contacted with the surface of the optical fiber to be coupled, and the alignment base face is attached to the optical fiber coupling end face so that the center of the optical waveguide structure is aligned with the center of the optical fiber to be coupled; the optical fiber groove penetrates through the top silicon layer and the oxide layer to be stopped in the bottom silicon layer, and the optical waveguide structure is formed in the top silicon layer; the optical fiber groove and the optical waveguide structure are formed based on the same dry etching process, and the method specifically comprises the following steps:

etching the substrate based on the graphical mask layer to obtain the optical fiber groove and the optical waveguide structure, wherein the optical fiber groove is obtained corresponding to the first opening, the first optical waveguide groove is obtained corresponding to the second opening, the second optical waveguide groove is obtained corresponding to the third opening, and the optical waveguide structure is formed between the first optical waveguide groove and the second optical waveguide groove; the first optical waveguide groove and the second optical waveguide groove have the same cross section shape, and both comprise a first optical waveguide groove section and a second optical waveguide groove section, wherein the cross section shape of the first optical waveguide groove section comprises a trapezoid shape, the cross section shape of the second optical waveguide groove section comprises a square shape, the second optical waveguide groove section is positioned on one side of the first optical waveguide groove section, which is far away from the optical fiber groove, and the width of the first optical waveguide groove section, which is close to one end of the optical fiber groove, is greater than the width of the first optical waveguide groove section, which is far away from one end of the optical fiber groove;

the method also comprises the following steps after the optical fiber groove and the optical waveguide structure are formed by etching:

and removing the oxide layer below the optical waveguide structure by using an etching agent through a dry etching process to form a gap between the bottom silicon and the optical waveguide structure at the corresponding position, wherein the gap is communicated with the first optical waveguide groove and the second optical waveguide groove to obtain the suspended optical waveguide structure.

2. The method of claim 1, wherein the gap is formed by a dry etching process using an etchant, and the fiber groove, the optical waveguide structure and the auxiliary alignment portion are formed by a dry etching process using a dry etching agent, wherein the etchant comprises gaseous hydrofluoric acid.

3. The method of claim 1, wherein the optical waveguide structure has a first end surface and a second end surface opposite to each other, the first end surface is exposed in the optical fiber groove, and the width of the first end surface is smaller than that of the second end surface.

4. The method of claim 3, wherein the optical waveguide structure comprises a first portion and a second portion, the first portion comprising the first end face and the second portion comprising the second end face, wherein a width of the first portion gradually increases in a direction from the first end face to the second portion; the cross-sectional shape of the second portion comprises a square.

5. The method of claim 1, wherein the top of the fiber groove is flush with the upper surface of the optical waveguide structure, and the depth of the fiber groove is equal to the sum of half of the thickness of the optical waveguide structure and the radius of the optical fiber to be coupled; the width of the optical fiber groove is equal to the diameter of the optical fiber to be coupled.

6. The method according to any one of claims 1 to 5, wherein the auxiliary alignment portion is spaced apart from the optical waveguide structure, the optical waveguide structure has a waveguide coupling end surface, and the waveguide coupling end surface is attached to the optical fiber coupling end surface to couple the optical fiber to be coupled to the optical waveguide structure, wherein the alignment base surface and the waveguide coupling end surface are located on the same plane, so that the optical fiber coupling end surface is attached to the waveguide coupling end surface and the alignment base surface at the same time.

7. The method according to claim 6, wherein the auxiliary alignment structures are formed on both sides of the optical waveguide structure, the alignment base is perpendicular to the bottom of the optical fiber groove, and the alignment base is disposed in an L-shape parallel to the side wall of the optical fiber groove of the optical fiber to be coupled.

8. An optical fiber coupling alignment structure of an optical fiber-to-optical waveguide structure is characterized by comprising a substrate, the optical waveguide structure and an auxiliary alignment part, wherein an optical fiber groove is formed in the substrate and used for placing an optical fiber to be coupled, the optical fiber to be coupled is provided with an optical fiber coupling end face, the auxiliary alignment part is provided with an alignment base face, the longitudinal section of the optical fiber groove comprises a square shape, the bottom and the side wall of the optical fiber groove are both contacted with the surface of the optical fiber to be coupled, and the alignment base face is attached to the optical fiber coupling end face so that the center of the optical waveguide structure is aligned with the center of the optical fiber to be coupled; a first optical waveguide groove and a second optical waveguide groove which are communicated with the optical fiber groove are also formed in the substrate, the optical waveguide structure is positioned between the first optical waveguide groove and the second optical waveguide groove, the cross section shapes of the first optical waveguide groove and the second optical waveguide groove are the same, the first optical waveguide groove and the second optical waveguide groove both comprise a first optical waveguide groove section and a second optical waveguide groove section, the cross section shape of the first optical waveguide groove section comprises a trapezoid shape, the cross section shape of the second optical waveguide groove section comprises a square shape, the second optical waveguide groove section is positioned on one side of the first optical waveguide groove section, which is far away from the optical fiber groove, and the width of one end, which is close to the optical fiber groove, of the first optical waveguide groove section is greater than the width of one end, which is far away from the optical fiber groove; the base comprises an SOI substrate, the SOI substrate comprises bottom silicon, an oxide layer and top silicon from bottom to top, wherein the optical fiber groove penetrates through the top silicon and the oxide layer and stops in the bottom silicon, and the optical waveguide structure is formed on the basis of the top silicon; and a gap is formed between the optical waveguide structure and the bottom layer silicon at the corresponding position below the optical waveguide structure, the gap is communicated with the first optical waveguide groove and the second optical waveguide groove, and the optical waveguide structure is arranged in a suspended manner.

9. The fiber-to-waveguide structure fiber-coupling alignment structure of claim 8, wherein the optical waveguide structure has opposing first and second end faces, the first end face exposed in the fiber groove, the first end face having a width less than a width of the second end face.

10. The fiber-coupling alignment structure of claim 9, wherein the optical waveguide structure comprises a first portion and a second portion, the first portion comprising the first end face and the second portion comprising the second end face, wherein a width of the first portion gradually increases in a direction from the first end face to the second portion, and a cross-sectional shape of the second portion comprises a square.

11. The fiber-to-waveguide structure fiber coupling alignment structure of claim 8, wherein the top of the fiber groove is flush with the upper surface of the optical waveguide structure and the depth of the fiber groove is equal to the sum of half the thickness of the optical waveguide structure and the radius of the fiber to be coupled; the width of the optical fiber groove is equal to the diameter of the optical fiber to be coupled.

12. The structure of any one of claims 8 to 11, wherein the auxiliary alignment portion is spaced apart from the optical waveguide structure, the optical waveguide structure has a waveguide coupling end surface, and the waveguide coupling end surface is attached to the optical fiber coupling end surface to couple the optical fiber to be coupled to the optical waveguide structure, wherein the alignment base surface and the waveguide coupling end surface are located on the same plane, so that the optical fiber coupling end surface is attached to the waveguide coupling end surface and the alignment base surface at the same time.

13. The fiber-coupling alignment structure of claim 12, wherein the auxiliary alignment structures are formed on both sides of the optical waveguide structure, the alignment base is perpendicular to the bottom of the fiber groove and the alignment base is disposed in an L-shape parallel to the side wall of the fiber groove of the optical fiber to be coupled.

14. A method of coupling an optical fiber to an optical package, comprising the steps of:

providing a fiber coupling alignment structure of an optical fiber to optical waveguide structure according to any of claims 8-13;

15. The method of coupling an optical fiber to an optical package of claim 14, further comprising the step of forming an adhesive layer in the fiber groove, the adhesive layer securing the optical fiber to be coupled in the fiber groove.