Thin film lithium tantalate large-spot-size end face coupler
By designing a thin-film lithium tantalate large-spot end-face coupler, and adopting a structure of three parallel narrow waveguide regions, variable-spacing three narrow waveguide regions, ridge-to-strip transition waveguide regions, and ridge-to-strip waveguide coupling waveguide regions, the problem of low transmission efficiency of traditional end-face couplers is solved, high-efficiency fiber array coupling is achieved, and process tolerance and coupling tolerance are improved.
Patent Information
- Application Number
- CN202520371792.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-05
- Publication Date
- 2025-12-19
- Estimated Expiration
- 2035-03-05
AI Technical Summary
Traditional end-face couplers have small receivers, which is not conducive to coupling with the large-mode end face of fiber arrays, resulting in low transmission efficiency. In addition, there is a lack of thin-film lithium tantalate end-face coupler designs, which makes it difficult to meet the application requirements of LTOI wafers.
A thin-film lithium tantalate large-spot end-face coupler was designed, comprising a substrate support layer, a dielectric layer, a thin-film lithium tantalate waveguide core layer, and a waveguide cladding. By employing a structure consisting of a three-parallel narrow waveguide region, a variable-spacing three-narrow waveguide region, a ridge-strip transition waveguide region, and a ridge-strip waveguide coupling waveguide region, the coupling area and tolerance are increased, thereby achieving efficient fiber array coupling.
It improves coupling efficiency with fiber arrays, reduces coupling process difficulty, supports end-face coupling of large-mode fiber arrays, especially for coupling requirements that are difficult to achieve, improves process tolerance, and reduces process incompatibility issues.
Smart Images
Figure CN223692544U_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optoelectronic integration technology, and particularly relates to a thin-film lithium tantalate large-spot end-face coupler. Background Technology
[0002] Lithium tantalate crystal (LiTaO3, abbreviated as LT) is a negative uniaxial crystal with non-centrosymmetry and a wide wavelength transmission range. It possesses excellent thermoelectric, piezoelectric, ferroelectric, electro-optic, and nonlinear optical properties. Therefore, LT is considered an excellent multifunctional material with high application value and promising prospects. Currently, traditional lithium tantalate materials are widely used in electronic communication equipment such as filters, resonators, and transducers, and have been applied in many high-end communication fields such as mobile phones, walkie-talkies, WeChat communication, and aerospace, demonstrating mature development and excellent material performance. Compared with lithium niobate crystal (LiNbO3, abbreviated as LN), lithium tantalate has advantages such as lower photorefractive damage, lower birefringence, lower dielectric loss, and lower signal drift under low-frequency carrier waves. This makes thin-film lithium tantalate a strong competitor to thin-film lithium niobate in some fields.
[0003] With technological advancements, smart-cut technology has matured. Recently, LTOI wafers manufactured using smart-cut technology have begun to enter the market. Compared to LNOI wafers, LTOI wafers offer higher production efficiency and lower costs due to their specialized technology, thus possessing greater commercial potential.
[0004] End-face couplers play a crucial role in the mass production of thin-film lithium tantalate. Compared to grating coupling or other vertical coupling methods, end-face coupling offers advantages such as low loss, high stability, and ease of packaging. Therefore, end-face couplers are often chosen in industry for coupling optical fibers and chips.
[0005] However, the receiver of traditional end-face couplers is small, which is not conducive to coupling with the large-spot end face of fiber arrays, resulting in low transmission efficiency. Furthermore, with the application of LTOI wafers, there is a lack of end-face coupler designs for thin-film lithium tantalate on the market. Therefore, we propose a thin-film lithium tantalate large-spot end-face coupler to solve the above problems. Utility Model Content
[0006] The purpose of this invention is to provide a thin-film lithium tantalate large-spot end-face coupler to solve the above-mentioned problems.
[0007] To achieve the above objectives, this utility model provides the following solution:
[0008] A thin-film lithium tantalate large-spot end-face coupler, comprising, from bottom to top, the following:
[0009] Substrate support layer, used to support the chip;
[0010] a medium layer;
[0011] a thin film lithium tantalate waveguide core layer, the thin film lithium tantalate waveguide core layer comprising a ridge transition layer below and a waveguide layer above;
[0012] a waveguide upper cladding layer;
[0013] the thin film lithium tantalate large mode area end coupler is divided into sequentially connected:
[0014] a three parallel narrow waveguide region, a variable interval three narrow waveguide region, a ridge transition transition waveguide region, a ridge transition waveguide coupling waveguide region and a thin film lithium tantalate waveguide region.
[0015] Optionally, the thin film lithium tantalate waveguide core layer of the three parallel narrow waveguide region is provided with three parallel narrow waveguides one, one end of the three parallel narrow waveguides one being used for communicating with the optical fiber array light path;
[0016] The narrow waveguide one is located in the ridge transition layer.
[0017] Optionally, the thin film lithium tantalate waveguide core layer of the variable interval three narrow waveguide region is provided with three narrow waveguides two with variable intervals, the narrow waveguide two located in the center being arranged in parallel with any of the narrow waveguides one, and the narrow waveguide two located in the edge part being arranged intersecting with the extension line of any of the narrow waveguides one.
[0018] The interval between the narrow waveguide two located in the edge part and the narrow waveguide two located in the middle part increases in turn in the direction away from the three parallel narrow waveguide region;
[0019] The two narrow waveguides two located in the edge part are symmetrically arranged;
[0020] One end of the narrow waveguide two communicates with one end of the corresponding narrow waveguide one in light path;
[0021] The first end diameter of the narrow waveguide two located in the middle part is smaller than the second end diameter of the narrow waveguide two;
[0022] The second end of the narrow waveguide two located in the middle part is arranged away from the narrow waveguide one;
[0023] The narrow waveguide two is located in the ridge transition layer.
[0024] Optionally, the thin film lithium tantalate waveguide core layer of the ridge transition transition waveguide region is provided with a ridge transition transition waveguide in light path communication with the narrow waveguide two located in the middle part, and the ridge transition transition waveguide is located in the ridge transition layer.
[0025] Optionally, the thin-film lithium tantalate waveguide core layer of the ridge-to-strip waveguide coupling waveguide region is provided with a ridge-to-strip waveguide coupling waveguide located between the ridge-to-strip layer and the waveguide layer, and one end of the ridge-to-strip waveguide coupling waveguide is in optical communication with one end of the ridge-to-strip transition waveguide located in the ridge-to-strip layer.
[0026] The ridge-to-strip waveguide coupling waveguide gradually widens away from the ridge-to-strip transition waveguide.
[0027] The ridge-to-strip waveguide coupling waveguide is tapered away from one end of the ridge-to-strip transition waveguide, and the bottom edge of the taper is located on the side away from the ridge-to-strip transition waveguide.
[0028] Optionally, the thin-film lithium tantalate waveguide core layer of the thin-film lithium tantalate waveguide region is provided with a thin-film lithium tantalate waveguide, one end of the thin-film lithium tantalate waveguide is in optical communication with one end of the ridge-to-strip waveguide coupling waveguide away from the ridge-to-strip transition waveguide, and the width of the thin-film lithium tantalate waveguide matches the width of the bottom edge of the taper.
[0029] The thin-film lithium tantalate waveguide is located between the ridge-to-strip layer and the waveguide layer.
[0030] Optionally, the waveguide upper cladding layer is one of silicon oxide, silicon oxynitride and silicon nitride, and the thickness of the waveguide upper cladding layer is 5-8 um.
[0031] Optionally, the thickness of the thin-film lithium tantalate waveguide core layer is 300 nm-420 nm, the depth of the waveguide layer is 80-260 nm, and the depth of the ridge-to-strip layer is the difference between the thickness of the thin-film lithium tantalate waveguide core layer and the depth of the waveguide layer.
[0032] Optionally, the thin-film lithium tantalate waveguide, the ridge-to-strip waveguide coupling waveguide, the ridge-to-strip transition waveguide, the middle narrow waveguide two and the middle narrow waveguide one are integrally formed.
[0033] Compared with the prior art, the present application has the following advantages and technical effects:
[0034] The present application increases the area of coupling with the fiber array end face by the provision of three parallel narrow waveguide regions, and the tolerance rate of the butt joint is improved due to the increased butt joint area. BRIEF DESCRIPTION OF DRAWINGS
[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.
[0036] Fig. 1 is a layer structure diagram of the utility model;
[0037] Fig. 2 is a sectional view of each part of the utility model; DETAILED DESCRIPTION
[0038] The technical solutions in the embodiments of the utility model will be apparently and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all the other embodiments obtained by the ordinary skilled in the art without creative labor fall within the scope of protection of the utility model.
[0039] In order to make the above object, features and advantages of the utility model more apparent, obvious and easy to understand, the utility model will be further described in detail below with reference to the drawings and specific embodiments.
[0040] With reference to Figs. 1-2 The utility model discloses a thin film lithium tantalate large mode spot end face coupler, including from below to above setting in proper order:
[0041] Substrate support layer is used for supporting chip;
[0042] Dielectric layer;
[0043] Thin film lithium tantalate waveguide core layer, thin film lithium tantalate waveguide core layer includes the ridge transition strip layer located below and the waveguide layer located above;
[0044] Waveguide upper cladding layer;
[0045] Along thin film lithium tantalate large mode spot end face coupler is divided into sequentially connected from right to left:
[0046] Three parallel narrow waveguide area, variable spacing three narrow waveguide area, ridge transition strip transition waveguide area, ridge transition strip waveguide coupling waveguide area and thin film lithium tantalate waveguide area.
[0047] As an optional implementation, the thin film lithium tantalate waveguide core layer of three parallel narrow waveguide area is provided with three parallel narrow waveguide one, and one end of the three parallel narrow waveguide one is used for communicating with the optical fiber array light path;
[0048] Narrow waveguide one is located in ridge transition strip layer.
[0049] As an optional implementation, the thin film lithium tantalate waveguide core layer of variable spacing three narrow waveguide area is provided with three spacing variable narrow waveguide two, the narrow waveguide two located in the center is parallelly arranged with any narrow waveguide one, and the extension line of the narrow waveguide two located in the edge portion is intersected with the extension line of any narrow waveguide one.
[0050] The distance between the two narrow waveguides located at the edge and the two narrow waveguides located at the middle increases in turn along the direction away from the three parallel narrow waveguide regions;
[0051] The two narrow waveguides located at the edge are symmetrically arranged;
[0052] One end of the narrow waveguide is in optical communication with one end of the corresponding narrow waveguide;
[0053] The first end of the narrow waveguide located at the middle has a smaller diameter than the second end of the narrow waveguide;
[0054] The second end of the narrow waveguide located at the middle is arranged away from the narrow waveguide;
[0055] The narrow waveguide is located at the ridge transition layer.
[0056] When the conventional trident end face coupler is converted from three waveguides to one waveguide, the distance between the three waveguides needs to be narrowed. Generally, the narrower the distance, the higher the coupling efficiency, but the process also faces the problem that the waveguides cannot be etched through. The utility model discloses a variable distance three narrow waveguide region design, which can avoid the problem of process incompatibility, does not need targeted design, and only needs to increase the distance between the two side waveguides when the three waveguides are converted into one waveguide, so that high-efficiency conversion can be realized.
[0057] When the conventional trident end face coupler is converted from three waveguides to one waveguide, the distance between the three waveguides needs to be narrowed. The principle is that the three waveguides close to each other make the equivalent refractive index of the cross section close to the waveguide material, at this time, the waveguide is gradually widened to one waveguide, so that the light field can be constrained, and the coupling from a large mode spot to a small mode spot can be realized. The design is reversely designed, the two side waveguides are gradually pulled apart, and the middle waveguide is widened at the same time, so that the constraint of the three waveguides on the mode field is gradually weakened, but the constraint of the center waveguide on the light field is enhanced, and the condition that the equivalent refractive index of the three waveguides needs to be approximately equal to the effective refractive index of the material does not need to be considered in principle.
[0058] As an optional implementation manner, the thin film lithium tantalate waveguide core layer of the ridge transition strip transition waveguide region is provided with a ridge transition strip transition waveguide in optical communication with the two narrow waveguides located at the middle, and the ridge transition strip transition waveguide is located at the ridge transition strip layer.
[0059] As an optional implementation manner, the thin film lithium tantalate waveguide core layer of the ridge transition strip waveguide coupling waveguide region is provided with a ridge transition strip waveguide coupling waveguide, the ridge transition strip waveguide coupling waveguide is located at the ridge transition strip layer and the waveguide layer, and one end of the ridge transition strip waveguide coupling waveguide is in optical communication with one end of the ridge transition strip transition waveguide located at the ridge transition strip layer;
[0060] The ridge transition strip waveguide coupling waveguide gradually widens along the direction away from the ridge transition strip transition waveguide;
[0061] The end of the ridge-to-stripe waveguide coupling wave away from the ridge-to-stripe transition waveguide is provided with a taper, and the bottom edge of the taper is located on the side away from the ridge-to-stripe transition waveguide.
[0062] As an optional implementation, the thin-film lithium tantalate waveguide core layer of the thin-film lithium tantalate waveguide region is provided with a thin-film lithium tantalate waveguide, one end of the thin-film lithium tantalate waveguide is in optical path communication with the end of the ridge-to-stripe waveguide coupling wave away from the ridge-to-stripe transition waveguide, and the width of the thin-film lithium tantalate waveguide matches the width of the bottom edge of the taper.
[0063] The thin-film lithium tantalate waveguide is located between the ridge-to-stripe layer and the waveguide layer.
[0064] As an optional implementation, the upper waveguide cladding layer is one of silicon oxide, silicon oxynitride and silicon nitride, and the thickness of the upper waveguide cladding layer is 5-8 um.
[0065] As an optional implementation, the thickness of the thin-film lithium tantalate waveguide core layer is 300-420 nm, wherein the depth of the waveguide layer is 80-260 nm, and the depth of the ridge-to-stripe layer is the difference between the thickness of the thin-film lithium tantalate waveguide core layer and the depth of the waveguide layer.
[0066] As an optional implementation, the thin-film lithium tantalate waveguide, the ridge-to-stripe waveguide coupling wave, the ridge-to-stripe transition waveguide, the second narrow waveguide located in the middle and the first narrow waveguide located in the middle are integrally formed.
[0067] The utility model discloses a kind of thin-film lithium tantalate large mode spot end surface couplers, thin-film lithium tantalate large mode spot end surface coupler includes substrate support layer, dielectric layer, thin-film lithium tantalate waveguide core layer and waveguide upper cladding layer from bottom to top.
[0068] The utility model in preparation, by etching method, remove the excess part on the surface of thin-film lithium tantalate core layer, make thin-film lithium tantalate core layer form specified cross section form, then cover waveguide upper cladding layer again.
[0069] Thin-film lithium tantalate waveguide core layer is divided into waveguide layer and ridge-to-stripe layer according to etching depth. Thin-film lithium tantalate large mode spot end surface coupler is composed of sequentially connected three parallel narrow waveguide regions (a), three narrow waveguide regions with variable spacing (b), ridge-to-stripe transition waveguide region (c), ridge-to-stripe waveguide coupling wave region (d) and thin-film lithium tantalate waveguide region (e).
[0070] Among them, the three parallel narrow waveguides one, the three narrow waveguides two with variable spacing and the ridge-to-stripe transition waveguide are only prepared in the ridge-to-stripe layer, and the waveguide layer is completely etched; the ridge-to-stripe waveguide coupling wave and the thin-film lithium tantalate waveguide are prepared in both the waveguide layer and the ridge-to-stripe layer.
[0071] The substrate support layer serves as a chip support; the waveguide upper cladding layer serves to protect the thin film lithium tantalate waveguide core layer and, together with the dielectric layer, serves to provide high refractive index contrast for the thin film lithium tantalate waveguide core layer.
[0072] The thin film lithium tantalate waveguide core layer has a thickness of 300nm to 420nm; the waveguide has a width of 0.5um to 1.1um; the waveguide layer has a depth of 80 to 260nm, and the ridge transition layer depth is the waveguide core layer thickness minus the etching depth of the lithium tantalate waveguide layer. The three-parallel narrow waveguide region (a), the variable-pitch three-narrow waveguide region (b) and the ridge transition waveguide region (c) have a thickness of 160 to 340nm. The thin film lithium tantalate waveguide combination layer of the ridge transition waveguide coupling waveguide region (d) and the thin film lithium tantalate waveguide region (e) is divided into two layers, the first layer (waveguide layer) has a thickness of 80 to 260nm, and the second layer (ridge transition layer) has a thickness of 160 to 340nm. The three-parallel narrow waveguide region (a) has a waveguide width of 150 to 300nm, and the spacing between the outermost two waveguides is 0.8 to 3um. The variable-pitch three-narrow waveguide region (b) has the same design as the connected part of the three-parallel narrow waveguide region (a) and a different design as the connected part of the ridge transition waveguide region (c). Specifically, the center waveguide has a width of 0.8 to 2um, and the spacing between the outermost two waveguides is 2 to 4.2um. The second layer of the ridge transition waveguide coupling waveguide region (d) has a waveguide width of 0.8 to 2um connected to the ridge transition waveguide region (c), and the first layer waveguide has a width of 0.1 to 0.3um close to the ridge transition waveguide region (c). The second layer has a width of 3 to 10um close to the end of the thin film lithium tantalate waveguide region (e), and the first layer has a width of 0.5um to 1.1um close to the end of the thin film lithium tantalate waveguide region (e). The thin film lithium tantalate waveguide region (e) only has the first layer, and the waveguide has a width of 0.5um to 1.1um.
[0073] The waveguide upper cladding layer is made of silicon oxide, silicon oxynitride or silicon nitride, and has a thickness of 5 to 8um.
[0074] The principle of the thin film lithium tantalate large-mode spot end face coupler provided by the utility model includes:
[0075] The thin film lithium tantalate large mode spot end face coupler is connected by an optical fiber array and three parallel narrow waveguides, light is incident from the optical fiber array into the three parallel narrow waveguides, the mode spot size of the three parallel narrow waveguides is close to the mode spot size of the optical fiber array, so that the coupling loss between the two modes is small. After the light enters the three parallel waveguides, the mode is affected by the three waveguides at the same time. Then the light is transmitted from the three parallel waveguides to the three narrow waveguides with changing spacing, during the transmission process of the three narrow waveguides with changing spacing, the central narrow waveguide gradually widens, and the constraint ability of the mode field gradually increases, while the two side narrow waveguides gradually move away from the central narrow waveguide, and the effect of the mode field gradually weakens. This process is converted into a mode field that only exists in the central waveguide by the three narrow waveguides. Then enter the ridge to strip transition waveguide, this stage is to stabilize the mode field transmitted in a single waveguide, the waveguide at this stage is a strip waveguide, which is not conducive to the subsequent device manufacturing, and at the same time has high transmission loss, and then enter the ridge to strip waveguide coupling waveguide. In the ridge to strip waveguide coupling waveguide, the light field gradually couples from the ridge to the strip to the waveguide, the ridge gradually widens, and when the waveguide is widened to a certain width, the waveguide also starts to widen through the inverted cone, and the mode field energy couples from the ridge to the strip to the waveguide. When the ridge is widened to the mode field distribution in the waveguide and the ridge waveguide is consistent, the ridge is no longer needed, at this time the waveguide below is a flat plate layer, and the waveguide is a thin film lithium tantalate waveguide connected to the device.
[0076] Compared with the prior art, the utility model has the characteristics that:
[0077] A. The thin film lithium tantalate large mode spot end face coupler design scheme can support the end face coupling demand of any mode spot optical fiber array, especially the difficult to realize large mode spot end face coupling demand, and the design can be perfectly realized.
[0078] B. Compared with the traditional three-pronged end face coupler, the ridge to strip layer process tolerance of the thin film lithium tantalate large mode spot end face coupler design scheme is improved by one level. The traditional three-pronged end face coupler needs to narrow the spacing between the three waveguides when converting the three waveguides into one waveguide. Generally, the narrower the spacing, the higher the coupling efficiency, but the process also faces the problem that the waveguides cannot be etched. This design can not consider the problem of process incompatibility, and only needs to increase the spacing between the two side waveguides when converting the three waveguides into one waveguide to realize high efficiency conversion.
[0079] C. The thin film lithium tantalate large mode spot end face coupler has the characteristics of large coupling tolerance. It does not require complete alignment and coupling with the optical fiber, which reduces the coupling process difficulty.
[0080] In the description of the utility model, need understanding is, the term "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and so on indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawing, just for the convenience of describing the utility model, and not indicate or imply that the indicated device or element must have a particular orientation, construct and operate in a particular orientation, therefore can not be understood as limiting the utility model.
[0081] The above-described embodiments are only descriptions of the preferred modes of the utility model, and do not limit the scope of the utility model, and various modifications and improvements to the technical solutions of the utility model made by those skilled in the art without departing from the design spirit of the utility model should fall within the protection scope defined by the claims of the utility model.
Claims
1. A thin film lithium tantalate large mode volume end coupler characterized by, It comprises, from bottom to top, in sequence: a substrate support layer for supporting a chip; a dielectric layer; a thin film lithium tantalate waveguide core layer, which comprises a ridge transition strip layer below and a waveguide layer above; a waveguide upper cladding layer; The thin film lithium tantalate large mode spot end coupler is divided into sequentially connected: three parallel narrow waveguide regions, variable pitch three narrow waveguide regions, ridge transition strip transition waveguide regions, ridge transition strip waveguide coupling waveguide regions and thin film lithium tantalate waveguide regions from right to left.
2. The thin film lithium tantalite large mode volume end coupler of claim 1, wherein: The thin film lithium tantalate waveguide core layer of the three parallel narrow waveguide region is provided with three parallel narrow waveguides one, one end of which is used for communicating with the optical fiber array light path; The narrow waveguide one is located in the ridge transition strip layer.
3. The thin film lithium tantalite large mode volume end coupler of claim 2, wherein: The thin film lithium tantalate waveguide core layer of the variable pitch three narrow waveguide region is provided with three narrow waveguides two with variable pitch, the narrow waveguide two located in the center is arranged in parallel with any narrow waveguide one, and the narrow waveguide two located in the edge is arranged by intersecting the extension line of any narrow waveguide one. The pitch between the narrow waveguide two located in the edge and the narrow waveguide two located in the middle increases in sequence away from the three parallel narrow waveguide region. Two narrow waveguides two located in the edge are symmetrically arranged. One end of the narrow waveguide two communicates with the corresponding one end of the narrow waveguide one. The first end diameter of the narrow waveguide two located in the middle is smaller than the second end diameter of the narrow waveguide two. The second end of the narrow waveguide two located in the middle is arranged away from the narrow waveguide one. The narrow waveguide two is located in the ridge transition strip layer.
4. The thin film lithium tantalite large mode volume end coupler of claim 3, wherein, The thin film lithium tantalate waveguide core layer of the ridge transition strip transition waveguide region is provided with a ridge transition strip transition waveguide which communicates with the narrow waveguide two located in the middle.
5. The thin film lithium tantalite large mode volume end coupler of claim 4, wherein: The thin film lithium tantalate waveguide core layer of the ridge transition strip waveguide coupling waveguide region is provided with a ridge transition strip waveguide coupling waveguide which is located in the ridge transition strip layer and the waveguide layer, one end of which communicates with one end of the ridge transition strip transition waveguide located in the ridge transition strip layer. The ridge transition strip waveguide coupling waveguide gradually widens away from the ridge transition strip transition waveguide. The end of the ridge transition strip waveguide coupling waveguide away from the ridge transition strip transition waveguide is tapered, and the bottom edge of the taper is located on the side away from the ridge transition strip transition waveguide.
6. The thin film lithium tantalite large mode volume end coupler of claim 5, wherein: The thin film lithium tantalate waveguide core layer of the thin film lithium tantalate waveguide region is provided with a thin film lithium tantalate waveguide, one end of which communicates with one end of the ridge transition strip waveguide coupling waveguide away from the ridge transition strip transition waveguide, and the width of the thin film lithium tantalate waveguide matches the width of the bottom edge of the taper. The thin film lithium tantalate waveguide is located in the ridge transition strip layer and the waveguide layer.
7. The thin film lithium tantalite large mode volume end coupler of claim 6, wherein: The waveguide upper cladding layer is one of silicon oxide, silicon oxynitride and silicon nitride, and the thickness of the waveguide upper cladding layer is 5-8 um.
8. The thin film lithium tantalite large mode volume end coupler of claim 7, wherein: The thickness of the thin film lithium tantalate waveguide core layer is 300-420 nm, wherein the depth of the waveguide layer is 80-260 nm, and the depth of the ridge transition strip layer is the difference between the thickness of the thin film lithium tantalate waveguide core layer and the depth of the waveguide layer.
9. The thin film lithium tantalite large mode volume end coupler of claim 8, wherein: The thin film lithium tantalite waveguide, the ridge-to-strip waveguide coupling waveguide, the ridge-to-strip transition waveguide, the middle located narrow waveguide two and the middle located narrow waveguide one are integrally formed structures.