阅读说明：本技术 一种钛扩散铌酸锂光波导的制备方法 (Preparation method of titanium-diffused lithium niobate optical waveguide ) 是由 富松 张洪波 华勇 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种钛扩散铌酸锂光波导的制备方法,包括在铌酸锂基片表面形成一层具有导电性能的导电薄膜；利用光刻工艺在所述导电薄膜的表面形成一第一钛条沉积窗口和光刻胶波导掩膜结构；对导电薄膜进行第一次腐蚀,在导电薄膜上对应于所述第一钛条沉积窗口的位置处形成第二钛条沉积窗口,所述第二钛条沉积窗口使得铌酸锂基片的表面显露于外；在铌酸锂基片显露于外的表面形成一层钛膜；将铌酸锂基片上的光刻胶波导掩膜结构剥离；对导电薄膜进行第二次腐蚀,得到具有钛条扩散源的铌酸锂基片；将得到的铌酸锂基片在预设的扩散温度及扩散时间下进行钛扩散,完成铌酸锂光波导的制备,光波导的成品质量成品率高。(The invention discloses a preparation method of a titanium-diffused lithium niobate optical waveguide, which comprises the steps of forming a conductive film with conductive performance on the surface of a lithium niobate substrate; forming a first titanium strip deposition window and a photoresist waveguide mask structure on the surface of the conductive film by utilizing a photoetching process; carrying out first corrosion on the conductive film, and forming a second titanium strip deposition window at the position, corresponding to the first titanium strip deposition window, on the conductive film, wherein the second titanium strip deposition window enables the surface of the lithium niobate substrate to be exposed; forming a titanium film on the exposed surface of the lithium niobate substrate; stripping the photoresist waveguide mask structure on the lithium niobate substrate; carrying out secondary corrosion on the conductive film to obtain a lithium niobate substrate with a titanium strip diffusion source; and performing titanium diffusion on the obtained lithium niobate substrate at a preset diffusion temperature and diffusion time to finish the preparation of the lithium niobate optical waveguide, wherein the finished product quality and yield of the optical waveguide are high.)

1. A preparation method of a titanium-diffused lithium niobate optical waveguide is characterized by comprising the following steps:

s1: forming a conductive film with conductive performance on the surface of the lithium niobate substrate;

s2: forming a first titanium strip deposition window and photoresist waveguide mask structures positioned on two sides of the first titanium strip deposition window on the surface of the conductive film by utilizing a photoetching process;

s3: carrying out first corrosion on the conductive film, and forming a second titanium strip deposition window at the position, corresponding to the first titanium strip deposition window, on the conductive film, wherein the second titanium strip deposition window enables the surface of the lithium niobate substrate to be exposed;

s4: forming a titanium film on the exposed surface of the lithium niobate substrate;

s5: stripping the photoresist waveguide mask structure on the lithium niobate substrate;

s6: carrying out secondary corrosion on the conductive film to obtain a lithium niobate substrate with a titanium strip diffusion source;

s7: and (4) performing titanium diffusion on the lithium niobate substrate obtained in the step (S6) at a preset diffusion temperature and diffusion time to complete the preparation of the lithium niobate optical waveguide.

2. The method according to claim 1, wherein in step S1, a conductive film is deposited on the lithium niobate substrate by sputtering or evaporation, and the thickness of the conductive film is 1.5 to 2.5 times the thickness of the formed titanium film.

3. The method for preparing a lithium niobate optical waveguide by titanium diffusion according to claim 1, wherein the specific method of step S2 is:

s201: forming a positive photoresist layer on the conductive film;

s202: exposing the positive photoresist layer by using a mask structure above the positive photoresist layer to obtain a first photoresist column of an exposure area and second photoresist columns positioned on two sides of the first photoresist column;

s203: and developing the exposed positive photoresist layer, and removing the first photoresist column in the exposure area to form the first titanium strip deposition window and photoresist waveguide mask structures positioned on two sides of the first titanium strip deposition window.

4. The method for preparing the lithium niobate optical waveguide by titanium diffusion according to claim 3, wherein in step S201, the positive photoresist layer is formed by coating and baking in sequence, the thickness of the positive photoresist layer is 0.8 to 1.5 μm, the baking time is 60 to 120S, and the baking temperature is 80 to 100 ℃.

5. The method according to claim 3, wherein in step S202, the positive photoresist layer is exposed to form a first photoresist column with an inverted trapezoid-shaped cross section on the positive photoresist layer in the exposure region and a second photoresist column with an inverted trapezoid-shaped cross section on the positive photoresist layer corresponding to the non-exposure region on both sides of the exposure region; the exposure time is 5-10 s.

6. The method of claim 3, wherein in step S203, the positive photoresist layer is developed for 30-40S.

7. The method as claimed in claim 5, wherein in step S3, the first etching on the conductive film is over etching to form a second ti-strip deposition window on the lithium niobate substrate and conductive film waveguide mask structures located on two sides of the second ti-strip deposition window, and the vertical projection area of the conductive film waveguide mask structure on the lithium niobate substrate is located in the vertical projection area of the photoresist waveguide mask structure on the same side of the lithium niobate substrate.

8. The method according to claim 7, wherein the broadening range between the edge of the mask structure of the conductive film waveguide corresponding to the etched side and the lower edge of the mask structure of the photoresist waveguide on the same side is 0.5 to 2.5 μm.

9. The method according to claim 1, wherein in step S4, a titanium film is deposited on the lithium niobate substrate by sputtering or evaporation, and the thickness of the titanium film is 700 to 900 angstroms.

10. The method for manufacturing a lithium niobate optical waveguide by titanium diffusion according to claim 1, wherein in step S7, when titanium diffusion is performed, the diffusion temperature is 1000 to 1100 ℃, and the diffusion time is 7 to 10 hours.

Technical Field

The invention relates to the technical field of optical waveguide preparation, in particular to a preparation method of a titanium-diffused lithium niobate optical waveguide.

Background

In the field of the production of optical waveguide devices, lithium niobate (LiNbO)₃) Crystal toolThe method has the excellent characteristics of high electro-optic coefficient, good optical transparency, high electro-optic response speed, stable chemical performance, low cost and the like, and is widely used for preparing optical waveguide devices. Titanium diffusion is a commonly used lithium niobate optical waveguide manufacturing process at present, and the specific process is to manufacture a metal titanium strip pattern on the surface of a lithium niobate substrate, and the metal titanium strip is diffused into the lithium niobate substrate in a titanium ion form through high-temperature diffusion to form the titanium diffusion lithium niobate optical waveguide. In the process, the quality of the metal titanium strip directly influences the yield of the titanium-diffused lithium niobate optical waveguide, the optical insertion loss and the consistency of the optical insertion loss.

The existing titanium diffusion lithium niobate optical waveguide device usually adopts an etching method or a stripping method to manufacture a titanium strip diffusion source. The titanium bar graph prepared by the corrosion method has obvious saw teeth on the edge, low yield and poor line width uniformity; the titanium strip prepared by the stripping method has uniform line width, but the image quality is not ideal, mainly because a photoetching process is needed when the titanium strip is manufactured, the photoetching process inevitably involves baking of a lithium niobate substrate, and because the lithium niobate substrate has the special property of pyroelectric effect, in the baking process, when the process temperature is higher than a temperature threshold value, the surface of the lithium niobate substrate can generate local charge accumulation to generate a 'discharge' phenomenon, and can also generate electric arc discharge when the process temperature is serious, so that a photoresist waveguide mask structure is damaged, the quality of a lithium niobate optical waveguide is seriously influenced, and the yield is low. Similarly, stripping can be realized by a thick glue technology, a double-layer glue technology, a glue surface toughening technology and the like, but all photoresist stripping methods cannot solve the problem of discharge damage caused by the lithium niobate pyroelectric effect in the metal titanium pattern preparation process at present.

Disclosure of Invention

The invention aims to provide a preparation method of a titanium diffusion lithium niobate optical waveguide, which aims to solve the problem that the quality of a titanium strip diffusion source in the prior art is not ideal, and further improve the optical parameters and the yield of the lithium niobate optical waveguide.

In order to solve the above problems, the present invention provides a method for preparing a titanium-diffused lithium niobate optical waveguide, comprising the following steps:

s1: forming a conductive film with conductive performance on the surface of the lithium niobate substrate;

s2: forming a first titanium strip deposition window and photoresist waveguide mask structures positioned on two sides of the first titanium strip deposition window on the surface of the conductive film by utilizing a photoetching process;

s3: carrying out first corrosion on the conductive film, and forming a second titanium strip deposition window at the position, corresponding to the first titanium strip deposition window, on the conductive film, wherein the second titanium strip deposition window enables the surface of the lithium niobate substrate to be exposed;

s4: forming a titanium film on the exposed surface of the lithium niobate substrate;

s5: stripping the photoresist waveguide mask structure on the lithium niobate substrate;

s6: carrying out secondary corrosion on the conductive film to obtain a lithium niobate substrate with a titanium strip diffusion source;

s7: and (4) performing titanium diffusion on the lithium niobate substrate obtained in the step (S6) at a preset diffusion temperature and diffusion time to complete the preparation of the lithium niobate optical waveguide.

Further, in step S1, a conductive film is deposited on the lithium niobate substrate by a sputtering or evaporation method, where the thickness of the conductive film is 1.5 to 2.5 times that of the formed titanium film.

Further, the specific method of step S2 is as follows:

s201: forming a positive photoresist layer on the conductive film;

s202: exposing the positive photoresist layer by using a mask structure above the positive photoresist layer to obtain a first photoresist column of an exposure area and second photoresist columns positioned on two sides of the first photoresist column;

s203: and developing the exposed positive photoresist layer, and removing the first photoresist column in the exposure area to form the first titanium strip deposition window and photoresist waveguide mask structures positioned on two sides of the first titanium strip deposition window.

Further, in step S201, the positive photoresist layer is formed by sequentially coating and baking, the thickness of the positive photoresist layer is 0.8 to 1.5 μm, the baking time is 60 to 120S, and the baking temperature is 80 to 100 ℃.

Further, in step S202, the positive photoresist layer is exposed to form a first photoresist column with an inverted trapezoid-shaped cross section on the positive photoresist layer of the exposure region and form a second photoresist column with an inverted trapezoid-shaped cross section on the positive photoresist layer of the non-exposure region on both sides of the exposure region; the exposure time is 5-10 s.

Further, in step S203, the time for developing the positive photoresist layer is 30 to 40 seconds.

Further, in step S3, the first etching of the conductive film is over etching, so as to form a second titanium strip deposition window and conductive film waveguide mask structures located on two sides of the second titanium strip deposition window on the lithium niobate substrate, and a vertical projection area of the conductive film waveguide mask structure on the lithium niobate substrate is located in a vertical projection area of the photoresist waveguide mask structure on the same side of the conductive film waveguide mask structure on the lithium niobate substrate.

Furthermore, the broadening range between the edge of the corresponding corroded side of the conductive film waveguide mask structure and the lower bottom edge of the photoresist waveguide mask structure on the same side of the conductive film waveguide mask structure is 0.5-2.5 microns.

Further, in step S4, a titanium film is deposited on the lithium niobate substrate by a sputtering or evaporation method, wherein the thickness of the titanium film is 700 to 900 angstroms.

Further, in step S7, when titanium is diffused, the diffusion temperature is 1000 to 1100 ℃, and the diffusion time is 7 to 10 hours.

According to the invention, before the photoetching process is carried out, a conductive film with good conductivity is firstly deposited on the lithium niobate substrate to be used as a pyroelectric effect release layer, charges generated by the pyroelectric effect of the lithium niobate substrate are released in time at the edge of the lithium niobate substrate and cannot be accumulated on the surface of the lithium niobate substrate, so that the discharge damage of a photoresist waveguide mask structure can be effectively avoided, and the quality of a lithium niobate optical waveguide is greatly improved; in addition, due to the existence of the conductive film layer, the metal titanium on the side wall of the photoresist waveguide mask structure with the 'trapezoid' structure and the metal titanium in contact with the lithium niobate substrate are always in a separated state in the titanium film deposition process, so that the positive photoresist is easy to strip, the titanium strip diffusion source is not damaged, and compared with the conventional negative photoresist, the photoetching process does not need to be repeatedly baked and does not need to be stripped by adopting special stripping liquid.

Drawings

Fig. 1 is a flow chart of a method for manufacturing a titanium-diffused lithium niobate optical waveguide according to the present invention.

Fig. 2 is a schematic process flow diagram of the preparation method of fig. 1.

Fig. 3 is a flowchart of step S2 in fig. 1.

The reference numbers of the specification are as follows:

the device comprises a lithium niobate substrate 1, a conductive film 2, a positive photoresist layer 3, a first photoresist column 31, a second photoresist column 32, a photoresist waveguide mask structure 32a, a conductive film waveguide mask structure 4, a titanium strip deposition window 5, a first titanium strip deposition window 51, a second titanium strip deposition window 52, a titanium film 6, a titanium strip diffusion source 7 and a mask structure 8.

Detailed Description

The invention will be further explained with reference to the drawings.

As shown in FIGS. 1-2, the preparation method of the titanium-diffused lithium niobate optical waveguide is based on lithium niobate (LiNbO)₃) The special property of the substrate 1 is combined with the stripping process of the conductive film 2 and the photoresist, a titanium strip diffusion source 7 is formed on the lithium niobate substrate 1, and after the titanium strip diffusion source 7 is formed, high-temperature diffusion is carried out, so that the titanium strip diffusion source 7 is diffused into the lithium niobate substrate 1 in a titanium ion form, and finally the titanium-diffused lithium niobate optical waveguide is obtained. The invention relates to a preparation method of a titanium-diffused lithium niobate optical waveguide, which comprises the following steps:

s1: a conductive film 2 is formed on the surface of a lithium niobate substrate 1.

Specifically, a lithium niobate substrate 1 is provided, and a conductive film 2 with conductive performance is deposited on the surface of the lithium niobate substrate 1 by adopting a sputtering or evaporation method to be used as a pyroelectric effect release layer. The conductive film 2 can form an equipotential surface on the surface of the lithium niobate substrate 1, and when the lithium niobate substrate 1 is baked at a high temperature, electric charges generated by the pyroelectric effect are released in time at the edge of the lithium niobate substrate and cannot be accumulated on the surface of the lithium niobate substrate, so that the discharge phenomenon and even the generation of arc discharge are avoided. In the present embodiment, the surface size of the lithium niobate substrate 1 is 3 inches.

The conductive film 2 can be made of a conductive film 2 material with high process selectivity with the titanium strip diffusion source 7. In this embodiment, the conductive film 2 is a metal aluminum film. It can be understood that the conductive film 2 can be deposited by selecting other materials according to different diffusion source materials, and is not limited to a metal film, but can also be other film materials with good conductivity, such as a doped oxide film: indium tin oxide, and the like.

In order to improve the forming quality of the titanium strip diffusion source 7, the thickness of the conductive film 2 is 1.5-2.5 times of that of the titanium strip diffusion source 7. In the present embodiment, the thickness of the conductive film 2 is preferably 1.5 times the thickness of the titanium strip diffusion source 7.

S2: a photoresist waveguide mask structure 32a is formed on the surface of the conductive film 2.

Specifically, a positive photoresist layer 3 is formed on the surface of the conductive film 2 by using a photolithography process, the positive photoresist layer 3 is exposed and developed, and the positive photoresist in the exposed region is removed, so that a first titanium strip deposition window 51 and a photoresist waveguide mask structure 32a located on two sides of the first titanium strip deposition window 51 are formed on the conductive film 2.

As shown in fig. 3, step S2 includes the following steps:

s201: a positive photoresist layer 3 is formed on the conductive film 2.

Firstly, uniformly coating a layer of positive photoresist on the surface of the lithium niobate substrate 1; the coating thickness of the positive photoresist is 0.8-1.5 mu m. In this embodiment, the positive photoresist is preferably coated to a thickness of 1 μm. It will be appreciated that in other embodiments, the positive photoresist layer 3 may also be deposited to a desired thickness, depending on the fabrication requirements.

Then baking and shaping the positive photoresist to form a positive photoresist layer 3; according to the coating thickness of the positive photoresist, the baking time is 60-120 s, and the baking temperature is 80-100 ℃. In the present embodiment, the baking time is preferably 90s, and the baking temperature is preferably 90 ℃.

S202: the positive photoresist layer 3 is exposed using a mask structure 8.

Above the positive photoresist layer 3, the positive photoresist layer 3 is exposed by using the mask structure 8 (the mask structure 8 is a light-tight structure), so as to form a first photoresist column 31 with an inverted trapezoid-shaped cross section on the positive photoresist layer 3 in the exposure region and form a second photoresist column 32 with an inverted trapezoid-shaped cross section at the position of the positive photoresist layer 3 corresponding to the non-exposure region on both sides of the exposure region. In the present embodiment, the exposure time is preferably 5 to 10 seconds.

Referring back to fig. 2, in particular, the mask structure 8 has a light-transmitting channel 81 passing through it from top to bottom, when exposing, the light source passes through the light-transmitting channel 81 to vertically radiate on the positive photoresist layer 3, the light generates a diffraction effect at the edge of the light-transmitting channel 81, so that the light energy gradually decreases from the middle region to the two side regions, that is, the light energy in the middle region is higher, the depth of the light energy penetrating through the positive photoresist layer 3 is deeper when exposing, the light energy in the two side regions is lower, and the depth of the light energy penetrating through the positive photoresist layer 3 is shallower when exposing, so that the first photoresist columns 31 of the inverse trapezoid structure can be formed in the exposure region, and the upper bottoms of the inverse trapezoids corresponding to the cross sections of the first photoresist columns 31 and the lower bottoms of the inverse trapezoids corresponding to the cross sections of the second photoresist columns 32 on the two sides are both located on the upper surface of the conductive film 2.

S203: the first photoresist column 31 is removed to obtain a photoresist waveguide mask structure 32 a.

Specifically, the exposed positive photoresist layer 3 is developed by using a developing solution for 30-40 seconds to remove the first photoresist columns 31 in the exposed regions and leave the second photoresist columns 32 in the unexposed regions. The first photoresist column 31 is removed to form a first titanium strip deposition window 51 with an inverted trapezoid cross section, and the remaining second photoresist column 32 forms a photoresist waveguide mask structure 32a when the titanium strip diffusion source 7 is deposited. In the present embodiment, the development time is preferably 35 s.

S3: the conductive film is etched to form a second titanium strip deposition window 52.

And etching the conductive film 2 for the first time, and etching the conductive film 2 in the area below the first deposition window 51 to form a second titanium strip deposition window 52 below the first titanium strip deposition window 51, wherein the second titanium strip deposition window 52 exposes the surface of the lithium niobate substrate 1 in the area of the second titanium strip deposition window 52. The cross section of the first titanium strip deposition window 51 is of an inverted trapezoid structure, and the first titanium strip deposition window 51 and the second titanium strip deposition window 52 form a titanium strip deposition window 5 for forming the titanium strip diffusion source 7.

In this embodiment, since the conductive film 2 is a metal aluminum film, the conductive film 2 is etched by using a mixed solution of nitric acid and hydrofluoric acid as an etching solution, and the etching solution has no etching effect on the photoresist waveguide mask structure 32. It will be appreciated that when the conductive film 2 is other metal or non-metal film, the etching solution should also be selected to etch the metal or non-metal film without etching the photoresist waveguide mask structure 32.

In order to improve the forming quality of the titanium strip diffusion source 7, when the conductive film 2 is subjected to the first etching, the degree of over etching needs to be reached, so as to form a second titanium strip deposition window 52 and conductive film waveguide mask structures 4 located at two sides of the second titanium strip deposition window 52 on the lithium niobate substrate 1. The vertical projection area of the conductive film waveguide mask structure 4 on the lithium niobate substrate 1 is located in the vertical projection area of the photoresist waveguide mask structure 32a on the same side of the lithium niobate substrate 1, that is, the distance between the edges of the adjacent sides of the two conductive film waveguide mask structures 4 is greater than the distance between the lower bottom edges of the adjacent sides of the two photoresist waveguide mask structures 32a with the regular trapezoid cross section (that is, the vertical projection width of the second titanium strip deposition window 52 on the lithium niobate substrate is greater than the bottom width of the first titanium strip deposition window 51 with the inverted trapezoid cross section), so that when the titanium film 6 is deposited on the lithium niobate substrate 1, the titanium strip diffusion source 7 formed by deposition can be prevented from contacting the conductive film waveguide mask structures 4 on both sides.

Because the allowable process tolerance of the over-etching is larger, the broadening range between the edge of the etched side of the conductive film waveguide mask structure 4 and the lower bottom edge of the photoresist waveguide mask structure 32a with the cross section of the same side in a regular trapezoid shape can be within 0.5-2.5 μm, so that the etching degree of the conductive film 2 can be easily controlled when the conductive film 2 is etched for the first time.

S4: a titanium film 6 is formed on the surface of the lithium niobate substrate 1.

Specifically, a titanium film 6 is deposited on the exposed surface of the lithium niobate substrate 1 (i.e. the area corresponding to the titanium strip deposition window 5) by a sputtering or evaporation method, and the thickness of the titanium film 6 is 700-900 angstroms.

S5: the photoresist waveguide mask structure 32a is stripped.

The photoresist waveguide mask structure 32a on the lithium niobate substrate 1 obtained in step S4 is peeled off. In the deposition process of the titanium film 6, the thickness of the conductive film 2 is greater than the thickness of the titanium strip diffusion source 7 formed by deposition (i.e. the thickness of the titanium film 6), so that the metal titanium on the side wall of the photoresist waveguide mask structure 32a and the metal titanium (i.e. the titanium strip diffusion source 7 to be prepared) contacting with the lithium niobate substrate 1 are always in a separated state, and the photoresist waveguide mask structure 32a is easy to strip and cannot damage the titanium strip diffusion source 7. Therefore, in this embodiment, the stripping of the photoresist waveguide mask structure 32a can be realized by placing the sample of the lithium niobate substrate 1 obtained in step S4 in an acetone solution and ultrasonically cleaning for a certain time; the ultrasonic cleaning time is preferably 15 minutes.

S6: and corroding the conductive film waveguide mask structure 4 to obtain the lithium niobate substrate 1 with the titanium strip diffusion source 7.

And (3) performing secondary corrosion on the conductive film 2 by using a mixed solution of phosphoric acid and glacial acetic acid as a corrosive solution, and removing the residual conductive film 2 (namely the conductive film waveguide mask structure 4) on the lithium niobate substrate 1 to obtain the lithium niobate substrate 1 with the titanium strip diffusion source 7. The corrosion solution can select different solutions to corrode the conductive film 2 aiming at the conductive film 2 materials of different materials, but the selected corrosion solution does not have corrosion effect on the titanium strip diffusion source 7.

S7: and (3) placing the lithium niobate substrate 1 formed with the titanium strip diffusion source 7 at high temperature for titanium diffusion to obtain the titanium diffusion lithium niobate optical waveguide.

And (2) placing the lithium niobate substrate 1 formed with the titanium strip diffusion source 7 obtained in the step (S6) in a high-temperature reaction device (such as a high-temperature furnace), and performing titanium diffusion at a preset diffusion temperature for a preset diffusion time to diffuse the titanium strip diffusion source 7 into the lithium niobate substrate 1 in a titanium ion form, so as to obtain the titanium diffusion lithium niobate optical waveguide, wherein the average insertion loss from the optical fiber to the optical fiber of the 50mm long titanium diffusion lithium niobate optical waveguide is about 1.84dB, the waveguide transmission loss is about 0.09dB/cm, the pattern quality is good, and the yield is high.

In the embodiment, the preset diffusion temperature is 1000-1100 ℃, and the diffusion time is 7-10 h. In the present embodiment, the diffusion temperature is preferably 1050 ℃, and the diffusion time is preferably 8 h.

According to the invention, the conductive film 2 with good conductivity is deposited on the lithium niobate substrate 1, so that an equipotential surface can be formed on the surface of the lithium niobate substrate 1, charges generated on the lithium niobate substrate 1 due to a pyroelectric effect can be timely released from the edge of the lithium niobate substrate 1 without being accumulated on the surface of the lithium niobate substrate 1, the damage of a photoresist waveguide mask structure 32a caused by the discharge or arc phenomenon generated in the photoetching process of the lithium niobate substrate 1 is effectively avoided, and the finished product quality of the lithium niobate optical waveguide is greatly improved.

In addition, because the thickness of the conductive film 2 is greater than that of the titanium film 6, and the width of the deposition window of the titanium film 6 is greater than the distance between the lower bottom edges of the adjacent sides of the two photoresist waveguide mask structures 32a in the shape of the regular trapezoid, in the deposition process of the titanium film 6, the metal titanium deposited on the side wall of the photoresist waveguide mask structure 32a in the shape of the regular trapezoid and the metal titanium in contact with the lithium niobate substrate 1 are always in a separated state, when the positive photoresist is stripped, the titanium strip diffusion source 7 cannot be damaged, and the finished product quality of the lithium niobate optical waveguide is further improved.

According to the invention, the titanium strip diffusion source 7 is prepared by using the photoresist waveguide mask structure 32a which is formed by positive photoresist and is in a positive trapezoid structure, so that the same effect and finished product quality as those of the titanium strip diffusion source 7 prepared by using the photoresist waveguide mask structure 32a which is formed by negative photoresist and is in an inverted trapezoid structure can be achieved, and the pattern edge of the prepared titanium strip diffusion source 7 is neat and has no damage; compared with the negative photoresist, the positive photoresist does not need to be repeatedly baked in the photoetching process, and a special stripping liquid does not need to be used for stripping.

It should be noted that, although the optical waveguide prepared in this embodiment is a lithium niobate optical waveguide based on titanium diffusion, the preparation method of the present invention is not only suitable for preparing an optical waveguide by using the lithium niobate substrate 1, but also suitable for preparing an optical waveguide by using other ferroelectric material substrates having pyroelectric effect; meanwhile, the preparation method of the invention is not only suitable for preparing the titanium diffusion lithium niobate optical waveguide, but also suitable for preparing devices with precise and complex pattern structures in other fields.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures made by using the contents of the present specification and the drawings can be directly or indirectly applied to other related technical fields, and are within the scope of the present invention.